Laser drawing apparatus

• US 6,100,915 A
• Filed: 08/27/1997
• Issued: 08/08/2000
• Est. Priority Date: 08/28/1996
• Status: Expired due to Fees

• Current Assignee: ORC Manufacturing Co., Ltd.
• Original Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha
• Inventors: Okuyama, Takashi, Iwasaki, Etsuo
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): PHAM, HAI CHI
• Application Number:
  US08/917,943
• Time in Patent Office: 1,077 Days
• Field of Search: 347/250, 347/252, 347/235, 347/249, 347/116, 358/481
• US Class Current: 347/249
• CPC Class Codes: H04N 1/047 Detection, control or error compensation of scanning velocity or position H04N1/0402 and H04N1/17 take precedence
• CPC Class Codes: H04N 1/1008 with sub-scanning by translatory movement of the picture-bearing surface
• CPC Class Codes: H04N 1/1135 for the main-scan only
• CPC Class Codes: H04N 2201/02439 Positioning method
• CPC Class Codes: H04N 2201/04712 using unbroken arrays of detectors, i.e. detectors mounted on the same substrate
• CPC Class Codes: H04N 2201/04718 outside the image area
• CPC Class Codes: H04N 2201/04732 Detecting at infrequent intervals, e.g. once or twice per line for main-scan control
• CPC Class Codes: H04N 2201/04784 using one or more clock signals selected from a number of clock signals of different phases
• CPC Class Codes: H04N 2201/04794 Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line
• CPC Class Codes: H05K 3/0082 characterised by the exposure method of radiation-sensitive masks

Abstract

In a laser drawing apparatus, a pattern is drawn on a workpiece by scanning the workpiece with at least one laser beam. The laser beam is modulated on the basis of raster-graphic data, in accordance with a series of clock pulses. A calculator calulates clock-pulse-phase-shift location data, indicative of where a phase of the clock pulses should be shifted, with a unit of less than 2Π. The calculation is made on the basis of pixel-dot-pitch discrepancy data measured along a scanning line defined by the scanning laser beam. A clock-pulse-outputting controller controls outputting the clock pulses so that the phase of the clock pulses is shifted, with the unit of less than 2Π. The shift occurs whenever the laser beam reaches each of the clock-pulse-phase-shift locations, represented by the clock-pulse-phase shift location data, during scanning of the workpiece with the laser beam. Consequently, a pixel-dot-pitch discrepance in the scanning line can be corrected with a unit of less than a one-pixel-dot size.

Claims

1. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam and by modulating the laser beam on the basis of raster-graphic data, in accordance with a series of clock pulses, said apparatus comprising:

a calculator for calculating respective clock-pulse-phase-shift location data, to which a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously measured along equally-divided sections of a scanning line defined by the scanning laser beam; and

a clock-pulse-outputting controller for controlling outputting of said clock pulses so that the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the scanning of said workpiece with said laser beam, whereby a pixel-dot-pitch discrepancy in each of said equally-divided sections of said scanning line can be corrected with a unit of less than a one-pixel-dot size.

2. The laser drawing apparatus of claim 1, further comprising a determiner for determining whether production of pixel-dot-pitch discrepancy at each clock-pulse-phase-shift location results from the pixel-dots being spaced too close to each other or too far away from each other,

wherein the phase of said clock pulses with the unit of less than 2π

is shifted such that a pixel-dot-pitch is made larger when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the phase of said clock pulses, with the unit of less than 2π

is shifted such that the pixel-dot-pitch is made smaller when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

3. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam and by modulating the laser beam on the basis of raster-graphic data in accordance with a series of clock pulses, the workpiece being scanned with the laser beam by deflecting the laser beam with respect to the workpiece, said apparatus comprising:

a calculator for calculating respective clock-pulse-phase-shift location data, to which a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously measured along equally-divided sections of a scanning line defined by the deflection of said laser beam in a main-scanning direction; and

a clock-pulse-outputting controller for controlling outputting of said clock pulses so that the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the scanning of said workpiece with said laser beam, whereby a pixel-dot-pitch discrepancy in each of said equally-divided sections of said scanning line can be corrected with a unit of less than a one-pixel-dot size.

4. The laser drawing apparatus of claim 3, further comprising a determiner for determining whether production of pixel-dot-pitch discrepancy at each clock-pulse-phase-shift location results from the pixel-dots being spaced too close to each other or too far away from each other,

wherein the phase of said clock pulses, with the unit of less than 2π

, is shifted such that the phase of said clock pulses is delayed when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the phase of said clock pulses, with the unit of less than 2π

, is shifted such that the phase of said clock pulses is advanced when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far from each other.

5. The laser drawing apparatus of claim 4, wherein said clock-pulse-outputting controller further comprises:

a clock pulse generator for producing a plurality of series of clock pulses based on a series of basic clock pulses, the respective series of clock pulses having phases shifted from each other within a range of 2π

;

a switcher for selectively outputting one of the series of clock pulses from said clock pulse generator; and

a regulator for regulating said switcher to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator regulates said switcher to output one of the series of clock pulses in said first clock-pulse-outputting manner when said determiner determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein said regulator regulates said switcher to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far from each other.

6. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam and by modulating the laser beam on the basis of raster-graphic data in accordance with a series of clock pulses, the workpiece being scanned with the laser beam by moving the workpiece with respect to the laser beam, said apparatus comprising:

a calculator for calculating respective clock-pulse-phase-shift location data, to which a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously measured along equally-divided sections of a scanning line defined by the movement of said workpiece with respect to said laser beam; and

a clock-pulse-outputting controller for controlling outputting said clock pulses so that the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the movement of said workpiece along said scanning line, whereby a pixel-dot-pitch discrepancy in each of said equally-divided sections of said scanning line can be corrected with a unit of less than a one-pixel-dot size.

7. The laser drawing apparatus of claim 6, further comprising a determiner for determining whether production of pixel-dot-pitch discrepancy at each clock-pulse-phase-shift location results from the pixel-dots being spaced too close to each other or too far away from each other,

wherein the phase of said clock pulses, with the unit of less than 2π

, is shifted such that the phase of said clock pulses is advanced when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the phase of said clock pulses, with the unit of less than 2π

, is shifted such that the phase of said clock pulses is delayed when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

8. The laser drawing apparatus of claim 7, wherein said clock-pulse-outputting controller comprises:

a clock pulse generator for producing a plurality of series of clock pulses based on a series of basic clock pulses, the respective series of clock pulses having phases shifted from each other within a range of 2π

;

a switcher for selectively outputting one of the series of clock pulses from said clock pulse generator; and

a regulator for regulating said switcher to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator regulates said switcher to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein said regulator regulates said switcher to output one of the series of clock pulses in said first clock-pulse-outputting manner when said determiner determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far from each other.

9. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam in both a main-scanning direction and in a sub-scanning direction, the laser beam being modulated on the basis of raster-graphic data in accordance with a first series of clock pulses, scanning of the workpiece with the laser beam in the main-scanning direction being carried out by deflecting the laser beam with respect to the workpiece, scanning of the workpiece with the laser beam in the sub-scanning direction being carried out by moving the workpiece with respect to the laser beam in accordance with a second series of clock pulses, said apparatus comprising:

a first calculator for calculating first respective clock-pulse-phase-shift location data, by which a phase of said first clock pulses should be shifted, with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously measured along first equally-divided sections of a main-scanning line defined by the deflection of said laser beam in said main-scanning direction;

a second calculator for calculating second respective clock-pulse-phase-shift location data, by which a phase of said second clock pulses should be shifted with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously measured along second equally-divided sections of a sub-scanning line which is defined by the movement of said workpiece in said sub-scanning direction with respect to said laser beam;

a first clock-pulse-outputting controller for controlling outputting of said first clock pulses such that the phase of said first clock pulse is shifted, with the unit of less than 2π

, whenever said laser beam reaches each main-scanning-clock-pulse-phase-shift location, represented by said first clock-pulse-phase-shift location data, during the scanning of said workpiece with said laser beam in said main-scanning direction, whereby a pixel-dot-pitch discrepancy in each of said first equally-divided sections of said main-scanning direction can be corrected with a unit of less than one-pixel-dot size; and

a second clock-pulse-outputting controller for controlling outputting of said second clock pulses such that the phase of said second clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each of sub-scanning-clock-pulse-phase-shift location, represented by said second clock-pulse-phase-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby a pixel-dot-pitch discrepancy in each of said second equally-divided sections of said sub-scanning direction can be corrected with a unit of less than one-pixel-dot size.

10. The laser drawing apparatus of claim 9, further comprising a first determiner for determining whether a production of a pixel-dot-pitch discrepancy at each main-scanning-clock-pulse-phase-shift location results from the pixel-dots being spaced too close to each other or too far away from each other,

wherein the shift of the phase of said first clock pulses, with the unit of less than 2π

, is carried out such that the phase of said first clock pulses is delayed when the first determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the shift of the phase of said first clock pulses, with the unit of less than 2π

, is carried out such that the phase of said first clock pulses is advanced when said first determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

11. The laser drawing apparatus of claim 10, wherein said first clock-pulse-outputting controller comprises:

a clock pulse generator for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the respective series of clock pulses having phases shifted from each other within a range of 2π

;

a switcher for selectively outputting one of the series of clock pulses from said clock pulse generator; and

a regulator for regulating said switcher to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator regulates said switcher to output one of the series of clock pulses in said first clock-pulse outputting manner when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein said regulator regulates said switcher to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far from each other.

12. The laser drawing apparatus of claim 10, further comprising a second determiner for determining whether production of a pixel-dot-pitch discrepancy at each sub-scanning-clock-pulse-phase-shift location results from said pixel-dots being spaced too close to each other or too far away from each other,

wherein the shift of the phase of said second clock pulses, with the unit of less than 2π

, is carried out such that the phase of said second clock pulses is advanced when said second determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the shift of the phase of said second clock pulses, with the unit of less than 2π

, is carried out such that the phase of said second clock pulses is delayed when said second determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

13. The laser drawing apparatus of claim 12, wherein said second clock-pulse-outputting controller comprises:

a clock pulse generator for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the respective series of clock pulses having phases which are shifted from each other within a range of 2π

;

a switcher for selectively outputting one of the plurality of series of clock pulses from said clock pulse generator; and

a regulator for regulating said switcher to output one of the plurality of series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator regulates said switcher to output one of the series of clock pulses in said first clock-pulse outputting manner when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other, and

wherein said regulator regulates said switcher to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other.

14. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam in both a main-scanning direction and in a sub-scanning direction, the laser beam being modulated on the basis of raster-graphic data in accordance with a series of clock pulses stored in a memory, scanning of the workpiece with the laser beam in the main-scanning direction being carried out by deflecting the laser beam with respect to the workpiece, scanning of the workpiece with the laser beam in the sub-scanning direction being carried out by moving the workpiece with respect to the laser beam, said apparatus comprising:

a first calculator for calculating one-pixel-dot-shift location data, indicating where a main-scan-start position in said main-scanning direction should be shifted by a distance corresponding to a one-pixel-dot size, on the basis of previously-measured inclination data of a sub-scanning line with respect to said main-scanning direction, the sub-scanning line being defined by the movement of said workpiece in said sub-scanning direction with respect to said laser beam,

a first controller for controlling the shift of said main-scan-start position by regulating a reading-timing of said raster-graphic data from said memory whenever said laser beam reaches each one-pixel-dot-shift location, represented by said one-pixel-dot-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby an inclination of said sub-scanning line with respect to said main-scanning direction can be corrected with a unit of a one-pixel-dot size;

a second calculator for calculating clock-pulse-phase-shift location data, indicating where a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of said inclination data; and

a second controller for controlling outputting of said clock pulses so that the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby the inclination of said sub-scanning line with respect to said main-scanning direction can be finely corrected with a unit of less than said one-pixel-dot size.

15. The laser drawing apparatus of claim 14, further comprising a determiner for determining whether the inclination of said sub-scanning line is positive or negative, the inclination of said sub-scanning line being defined as being positive when a drifted distance of said sub-scanning line, resulting from the inclination thereof, is produced in said main-scanning direction, the inclination of said sub-scanning line being defined as being negative when a drifted distance of said sub-scanning line, resulting from the inclination thereof, is produced in an opposite direction to said main-scanning direction,

wherein the reading-timing of said raster-graphic data from said memory is advanced by a time required to read a one-pixel raster-graphic datum from said memory when said determiner determines the inclination of said sub-scanning line is positive,

wherein the reading-timing of said raster-graphic data from said memory is delayed by the time required to read said one-pixel raster-graphic datum from said memory when said determiner determines the inclination of said sub-scanning line is negative,

wherein the shift of the phase of said clock pulses, with the unit of less than 2π

, is carried out such that the phase of said clock pulses is advanced when said determiner determines the inclination of said sub-scanning line is positive, and

wherein the shift of the phase of said clock pulses, with the unit of less than 2π

, is carried out such that the phase of said clock pulses is delayed when said determiner determines the inclination of said sub-scanning line is negative.

16. The laser drawing apparatus of claim 15, wherein said second controller comprises:

a clock pulse generator for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the series of clock pulses having phases which are shifted from each other within a range of 2π

;

a switcher for selectively outputting one of the series of clock pulses from said clock pulse generator; and

a regulator for regulating said switcher to output one of the series of clock pulse in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator regulates said switcher to output one of the series of clock pulses in said first clock-pulse-outputting manner when said determiner determines that the inclination of said sub-scanning line is negative, and

wherein said regulator regulates said switch to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner determines that the inclination of said sub-scanning line is positive.

17. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam in both a main-scanning direction and in a sub-scanning direction, the laser beam being modulated on the basis of raster-graphic data read from a memory in accordance with a series of clock pulses, scanning of the workpiece with the laser beam in the main-scanning direction being carried out by deflecting the laser beam with respect to the workpiece, scanning of the workpiece with the laser beam in the sub-scanning direction being carried out by moving the workpiece with respect to the laser beam, said apparatus comprising:

a first calculator for calculating one-pixel-dot-shift location data, indicating where a main-scan-start position should be shifted, by a distance corresponding to a one-pixel-dot size, on the basis of relative inclination data of a sub-scanning line with respect to said main-scanning direction, the sub-scanning line being defined by the movement of said workpiece in said sub-scanning direction with respect to said laser beam, the relative inclination data of said sub-scanning line being determined on the basis of previously-measured absolute inclination data of said sub-scanning line with respect to said main-scanning direction and inclination data of an axis, defined by positioning-marks of said workpiece, with respect to said main-scanning line;

a first controller for controlling the shift of said main-scan-start position by regulating a reading time of said raster-graphic data from said memory whenever said laser beam reaches each one-pixel-dot-shift location, represented by said one-pixel-dot-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby a relative inclination of said sub-scanning line with respect to said main-scanning direction can be corrected with a unit of a one-pixel-dot size so that said sub-scanning line is approximate to said axis defined by the positioning-marks of said workpiece;

a second calculator for calculating clock-pulse-phase-shift location data, indicating where a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of said inclination data; and

a second controller for controlling outputting of said clock pulses so that the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby the relative inclination of said sub-scanning line, with respect to said main-scanning direction, can be finely corrected with a unit of less than said one-pixel-dot size so that said sub-scanning line is more closely approximate to said axis defined by the positioning-marks of said workpiece.

18. The laser drawing apparatus of claim 17, further comprising a determiner for determining whether the relative inclination of said sub-scanning line is positive or negative, the relative inclination of said sub-scanning line being defined as being positive when a shifted distance of said sub-scanning line resulting from the inclination thereof is in said main-scanning direction, the relative inclination of said sub-scanning line being defined as being negative when a shifted distance of said sub-scanning line resulting from the inclination thereof is in an opposite direction to said main-scanning direction,

wherein the reading time of said raster-graphic data from said memory is advanced by a time required to read a one-pixel raster-graphic datum from said memory when said determiner determines that the relative inclination of said sub-scanning line is positive,

wherein the reading time of said raster-graphic data from said memory is delayed by the time required to read said one-pixel raster-graphic datum from said memory when said determiner determines that the relative inclination of said sub-scanning line is negative,

wherein the shift of the phase of said clock pulses, with the unit of less than 2π

, is carried out such that the phase of said clock pulses is advanced when said determiner determines that the inclination of said sub-scanning line is positive, and

wherein the shift of the phase of said clock pulses, with the unit of less than 2π

, is carried out such that the phase of said clock pulses is delayed when said determiner determines that the inclination of said sub-scanning line is negative.

19. The laser drawing apparatus of claim 18, wherein said second controller comprises:

a clock pulse generator for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the series of clock pulses having phases which are shifted from each other within a range of 2π

;

a switcher for selectively outputting one of the series of clock pulses from said clock pulse generator; and

a regulator for regulating said switcher to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator regulates said switcher to output one of the series of clock pulses in said first clock-pulse-outputting manner when said determiner determines that the relative inclination of said sub-scanning line is negative, and

wherein said regulator regulates said switches to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner determines that the inclination of said sub-scanning line is positive.

20. The laser drawing apparatus of claim 17, further comprising:

a detector for detecting the positioning-marks of said workpiece; and

a calculator for calculating the inclination data of said axis, defined by the positioning-marks of said workpiece, on the basis of the detection of said positioning-marks by said detector.

21. The laser drawing apparatus of claim 20, wherein said detector comprises:

an image sensor for optically and electronically sensing the positioning-marks of said workpiece, with respect to a coordinate system defined in a drawing plane of said apparatus, to produce video signals carrying the positioning-marks of said workpiece; and

a video-signal processor for processing the video signals to obtain the inclination data of said axis defined by the positioning-marks of said workpiece.

22. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam in both a main-scanning direction and in a sub-scanning direction, the laser beam being modulated on the basis of raster-graphic data read from a memory in accordance with a series of clock pulses, scanning of the workpiece with the laser beam in the main-scanning direction being carried out by deflecting the laser beam with respect to the workpiece, scanning of the workpiece with the laser beam in the sub-scanning direction being carried out by moving the workpiece with respect to the laser beam, said apparatus comprising:

a first calculator for calculating one-pixel-dot-shift location data, indicating where a main-scan-start position in said main-scanning direction should be shifted, by a distance corresponding to a one-pixel-dot size, on the basis of previously-measured pixel-dot-misalignment data of pixel-dots included in a sub-scanning line defined by the movement of said workpiece in said sub-scanning direction;

a first controller for controlling the shift of said main-scan-start position by regulating a reading time of said raster-graphic data from said memory whenever said laser beam reaches each one-pixel-dot-shift location, represented by said one-pixel-dot-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby a pixel-dot-misalignment of pixel-dots included in said sub-scanning line can be corrected with a unit of a one-pixel-dot size;

a second calculator for calculating clock-pulse-phase-shift location data, indicating where a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of said pixel-dot-misalignment data; and

a second controller for controlling outputting of said clock pulses so that the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby said pixel-dot-misalignment can be finely corrected with a unit of less than a one-pixel-dot size.

23. The laser drawing apparatus of claim 22, further comprising:

a first determiner for determining whether production of a pixel-dot-misalignment at each one-pixel-dot-shift location is positive or negative, the pixel-dot-misalignment being defined as being positive when produced at each of said one-pixel-dot-shift locations in said main-scanning direction, the pixel-dot-misalignment being defined as being negative when produced at each one-pixel-dot-shift location in an opposite direction to said main-scanning direction; and

a second determiner for determining whether production of a pixel-dot-misalignment at said clock-pulse-phase-shift location is positive or negative, the pixel-dot-misalignment being defined as being positive when produced at each clock-pulse-phase-shift location in said main-scanning direction, the pixel-dot-misalignment being defined as being negative when produced at each clock-pulse-phase-shift location in an opposite direction to said main-scanning direction,

wherein the reading time of said raster-graphic data from said memory is advanced by a time required to read a one-pixel raster-graphic datum from said memory when said first determiner determines that the pixel-dot-misalignment is positive,

wherein the reading time of said raster-graphic data from said memory is delayed by the time required to read said one-pixel raster-graphic datum from said memory when said first determiner determines that the pixel-dot-misalignment is negative,

wherein the shift of the phase of said clock pulses, with the unit of less than 2π

, is carried out such that the phase of said clock pulses is advanced when said second determiner determines that the pixel-dot-misalignment is positive, and

wherein the shift of the phase of said clock pulses, with the unit of less than 2π

, is carried out such that the phase of said clock pulses is delayed when said second determiner determines that the pixel-dot-misalignment is negative.

24. The laser drawing apparatus of claim 23, wherein said second controller comprises:

a clock pulse generator for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the respective series of clock pulses having phases which are shifted from each other within a range of 2π

;

a switcher for selectively outputting one of the series of clock pulses from said clock pulse generator; and

a regulator for regulating said switcher to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator regulates said switcher to output one of the series of clock pulses in said first clock-pulse-outputting manner when said second determiner determines that the pixel-dot-misalignment is negative, and

wherein said regulator regulates said switches to output one of the series of clock pulses in said second clock-pulse-outputting manner when said second determiner determines that the pixel-dot-misalignment is positive.

25. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam and by modulating the laser beam on the basis of raster-graphic data in accordance with a series of clock pulses, said apparatus comprising:

calculator means for calculating respective clock-pulse-phase-shift location data, indicating where a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously measured along equally-divided sections of a scanning line defined by the scanning laser beam; and

clock-pulse-outputting controller means for controlling outputting of said clock pulses so that the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the scanning of said workpiece with said laser beam, whereby a pixel-dot-pitch discrepancy in each of said equally-divided sections of said scanning line can be corrected with a unit of less than a one-pixel-dot size.

26. The laser drawing apparatus of claim 25, further comprising determiner means for determining whether production of a pixel-dot-pitch discrepancy at each clock-pulse-phase-shift location results from the pixel-dots being spaced too close to each other or too far away from each other;

wherein the shift of the phase of said clock pulses, with a unit of less than 2π

, is carried out such that a pixel-dot-pitch is made larger when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the shift of the phase of said clock pulses, with a unit of less than 2π

, is carried out such that the pixel-dot-pitch is made smaller when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far from each other.

27. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam and by modulating the laser beam on the basis of raster-graphic data in accordance with a series of clock pulses, the workpiece being scanned with the laser beam by deflecting the laser beam with respect to the workpiece, said apparatus comprising:

calculator means for calculating respective clock-pulse-phase-shift location data, indicating where a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously-measured along equally-divided sections of a scanning line defined by the deflection of said laser beam in said main-scanning direction; and

clock-pulse-outputting controller means for controlling outputting of said clock pulses so that the phase of said clock pulses is shifted, with a unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the scanning of said workpiece with said laser beam, whereby a pixel-dot-pitch discrepancy in each of said equally-divided sections of said scanning line can be corrected with a unit of less than a one-pixel-dot size.

28. The laser drawing apparatus of claim 27, further comprising determiner means for determining whether production of a pixel-dot-pitch discrepancy at each of said clock-pulse-phase-shift locations results from the pixel-dots being spaced too close to each other or too far away from each other,

wherein the shift of the phase of said clock pulses, with a unit of less than 2π

, is carried out such that the phase of said clock pulses is delayed when said determiner means determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the shift of the phase of said clock pulses, with a unit of less than 2π

, is carried out such that the phase of said clock pulses is advanced when said determiner means determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

29. The laser drawing apparatus of claim 28, wherein said clock-pulse-outputting controller means comprises:

clock pulse generator means for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the respective series of clock pulses having phases which are shifted from each other within a range of 2π

;

switcher means for selectively outputting one of the series of clock pulses from said clock pulse generator means; and

regulator means for regulating said switcher means to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the clock pulses, wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said first clock-pulse-outputting manner when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

30. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam and by modulating the laser beam on the basis of raster-graphic data in accordance with a series of clock pulses, the workpiece being scanned with the laser beam by moving the workpiece with respect to the laser beam, said apparatus comprising:

calculator means for calculating respective clock-pulse-phase-shift location data indicating where a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously-measured along equally-divided sections of a scanning line defined by the movement of said workpiece with respect to said laser beam; and

clock-pulse-outputting controller means for controlling outputting of said clock pulses so that the phase of said clock pulses is shifted, with a unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the movement of said workpiece along said scanning line, whereby a pixel-dot-pitch discrepancy in each of said equally-divided sections of said scanning line can be corrected with a unit of less than a one-pixel-dot size.

31. The laser drawing apparatus of claim 30, further comprising determiner means for determining whether a production of a pixel-dot-pitch discrepancy at each clock-pulse-shift location results from the pixel-dots being spaced too close to each other or too far away from each other,

wherein the shift of the phase of said clock pulses, with a unit of less than 2π

, is carried out such that the phase of said clock pulses is advanced when said determiner means determines the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the shift of the phase of the said clock pulses, with a unit of less than 2π

, is carried out such that the phase of said clock pulses is delayed when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

32. The laser drawing apparatus of claim 31, wherein said clock-pulse-outputting controller means comprises:

clock pulse generator means for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the respective series of clock pulses having phases which are shifted from each other within a range of 2π

;

switcher means for selectively outputting one of the series of clock pulses from said clock pulse generator means; and

regulator means for regulating said switcher means to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said first clock-pulse-outputting manner when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

33. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam in both a main-scanning direction and in a sub-scanning direction, the laser beam being modulated on the basis of raster-graphic data in accordance with a first series of clock pulses, scanning of the workpiece with the laser beam in the main-scanning direction being carried out by deflecting the laser beam with respect to the workpiece, scanning of the workpiece with the laser beam in the sub-scanning direction being carried out by moving the workpiece with respect to the laser beam, in accordance with a second series of clock pulses, said apparatus comprising:

first calculator means for calculating first respective clock-pulse-phase-shift location data indicating where a phase of said first clock pulses should be shifted, with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously-measured along first equally-divided sections of a main-scanning line defined by the deflection of said laser beam in said main-scanning direction;

second calculator means for calculating second respective clock-pulse-phase-shift location data indicating where a phase of said second clock pulses should be shifted, with a unit of less than 2π

, on the basis of pixel-dot-pitch discrepancy data previously-measured along second equally-divided sections of a sub-scanning line defined by the movement of said workpiece in said sub-scanning direction with respect to said laser beam;

first clock-pulse-outputting controller means for controlling outputting of said first clock pulses so that the phase of said first clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each main-scanning-clock-pulse-phase-shift location, represented by said first clock-pulse-phase-shift location data, during the scanning of said workpiece with said laser beam in said main-scanning direction, whereby a pixel-dot-pitch discrepancy in said first equally-divided sections of said main-scanning direction can be corrected with a unit of less than a one-pixel-dot size; and

second clock-pulse-outputting controller means for controlling outputting of said second clock pulses so that the phase of said second clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each sub-scanning-clock-pulse-phase-shift location, represented by said second clock-pulse-phase-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby a pixel-dot-pitch discrepancy in said second equally-divided sections of said sub-scanning direction can be corrected with a unit of less than a one-pixel-dot size.

34. The laser drawing apparatus of claim 33, further comprising first determiner means for determining whether production of a pixel-dot-pitch discrepancy at each main-scanning-clock-pulse-phase-shift location results from the pixel-dots being spaced too close to each other or too far away from each other,

wherein the shift of the phase of said first clock pulses, with a unit of less than 2π

, is carried out such that the phase of said first clock pulses is delayed when said first determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the shift of the phase of said first clock pulses, with a unit of less than 2π

, is carried out such that the phase of said first clock pulses is advanced when said first determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

35. The laser drawing apparatus of claim 34, wherein said first clock-pulse-outputting controller means comprises:

clock pulse generator means for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the respective series of clock pulses having phases which are shifted from each other within a range of 2π

;

switcher means for selectively outputting one of the series of clock pulses from said clock pulse generator means; and

regulator means for regulating said switcher means to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said first clock-pulse-outputting manner when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

36. The laser drawing apparatus of claim 34, further comprising second determiner means for determining whether production of a pixel-dot-pitch discrepancy at each sub-scanning-clock-pulse-phase-shift location results from the pixel-dots being spaced too close to each other or too far away from each other,

wherein the shift of the phase of said second clock pulses, with a unit of less than 2π

, is carried out such that the phase of said second clock pulses is advanced when said second determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other, and

wherein the shift of the phase of said second clock pulses, with a unit of less than 2π

, is carried out such that the phase of said second clock pulses is delayed when said second determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other.

37. The laser drawing apparatus of claim 36, wherein said second clock-pulse-outputting controller means comprises:

clock pulse generator means for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the respective series of clock pulses having phases which are shifted from each other within a range of 2π

;

switcher means for selectively outputting one of the series of clock pulses from said clock pulse generator means; and

regulator means for regulating said switcher means to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said first clock-pulse-outputting manner when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too far away from each other, and

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner means determines that the production of the pixel-dot-pitch discrepancy results from the pixel-dots being spaced too close to each other.

38. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam in both a main-scanning direction and in a sub-scanning direction, the laser beam being modulated on the basis of raster-graphic data, read from a memory, in accordance with a series of clock pulses, scanning of the workpiece with the laser beam in the main-scanning direction being carried out by deflecting the laser beam with respect to the workpiece, scanning of the workpiece with the laser beam in the sub-scanning direction being carried out by moving the workpiece with respect to the laser beam, said apparatus comprising:

first calculator means for calculating one-pixel-dot-shift location data indicating where a main-scan-start position in said main-scanning direction should be shifted by a distance corresponding to a one-pixel-dot size on the basis of previously-measured inclination data of a sub-scanning line with respect to said main-scanning direction, the sub-scanning line being defined by the movement of said workpiece in said sub-scanning direction with respect to said laser beam;

first controller means for controlling the shift of said main-scan-start position by regulating a reading time of said raster-graphic data from said memory whenever said laser beam reaches each one-pixel-dot-shift location, represented by said one-pixel-dot-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby an inclination of said sub-scanning line with respect to said main-scanning direction can be corrected with a unit of a one-pixel-dot size;

second calculator means for calculating clock-pulse-phase-shift location data indicating where a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of said inclination data; and

second controller means for controlling outputting of said clock pulses so that the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby the inclination of said sub-scanning line with respect to said main-scanning direction can be finely corrected with a unit of less than a one-pixel-dot size.

39. The laser drawing apparatus of claim 38, further comprising determiner means for determining whether the inclination of said sub-scanning line is positive or negative, the inclination of said sub-scanning line being defined as positive when a shifted distance of said sub-scanning line, resulting from the inclination of said sub-scanning line, is produced in said main-scanning direction, the inclination of said sub-scanning line being defined as negative when a shifted distance of said sub-scanning line, resulting from the inclination thereof, is produced in an opposite direction to said main-scanning direction,

wherein the reading time of said raster-graphic data from said memory is advanced by a time required to read a one-pixel raster-graphic datum from said memory when said determiner means determines that the inclination of said sub-scanning line is positive,

wherein the reading time of said raster-graphic data from said memory is delayed by the time required to read said one-pixel raster-graphic datum from said memory when said determiner means determines that the inclination of said sub-scanning line is negative,

wherein the shift of the phase of said clock pulses, with a unit of less than 2π

, is carried out such that the phase of said clock pulses is advanced when said determiner means determines that the inclination of said sub-scanning line is positive, and

wherein the shift of the phase of said clock pulses with a unit of less than 2π

is carried out such that the phase of said clock pulses is delayed when said determiner means determines that the inclination of said sub-scanning line is negative.

40. The laser drawing apparatus of claim 39, wherein said second controller means comprises:

clock pulse generator means for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the series of clock pulses having phases which are shifted from each other within a range of 2π

;

switcher means for selectively outputting one of the series of clock pulses from said clock pulse generator means; and

regulator means for regulating said switcher means to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said first clock-pulse-outputting manner when said determiner means determines that the inclination of said sub-scanning line is negative, and

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner means determines that the inclination of said sub-scanning line is positive.

41. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam in both a main-scanning direction and in a sub-scanning direction, the laser beam being modulated on the basis of raster-graphic data, read from a memory, in accordance with a series of clock pulses, scanning of the workpiece with the laser beam in the main-scanning direction being carried out by deflecting the laser beam with respect to the workpiece, scanning of the workpiece with the laser beam in the sub-scanning direction being carried out by moving the workpiece with respect to the laser beam, said apparatus comprising:

first calculator means for calculating one-pixel-dot-shift location data indicating where a main-scan-start position should be shifted, by a distance corresponding to a one-pixel-dot size, on the basis of relative inclination data of a sub-scanning line with respect to said main-scanning direction, the sub-scanning line being defined by the movement of said workpiece in said sub-scanning direction with respect to said laser beam, the relative inclination data of said sub-scanning line being prepared on the basis of previously-measured absolute inclination data of said sub-scanning line, with respect to said main-scanning direction, and inclination data of an axis, defined by positioning-marks of said workpiece, with respect to said main-scanning line;

first controller means for controlling the shift of said main-scan-start position by regulating a reading time of said raster-graphic data from said memory whenever said laser beam reaches each one-pixel-dot-shift location, represented by said one-pixel-dot-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby a relative inclination of said sub-scanning line, with respect to said main-scanning direction, can be corrected with a unit of a one-pixel-dot size so that said sub-scanning line is approximate to said axis defined by the positioning-marks of said workpiece;

second calculator means for calculating clock-pulse-phase-shift location data indicating where a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of said relative inclination data; and

second controller means for controlling outputting of said clock pulses so the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift location, represented by said clock-pulse-phase-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby the relative inclination of said sub-scanning line, with respect to said main-scanning direction, can be finely corrected with a unit of less than said one-pixel-dot size so said sub-scanning line is more closely approximate to said axis defined by the positioning-marks of said workpiece.

42. The laser drawing apparatus of claim 41, further comprising determiner means for determining whether the relative inclination of said sub-scanning line is positive or negative, the relative inclination of said sub-scanning line being defined as positive when a shifted distance of said sub-scanning line, resulting from the relative inclination of said sub-scanning line, is produced in said main-scanning direction, the relative inclination of said sub-scanning line being defined as negative when a shifted distance of said sub-scanning line, resulting from the relative inclination of said sub-scanning line, is produced in an opposite direction to said main-scanning direction,

wherein the reading time of said raster-graphic data from said memory is advanced by a time required to read a one-pixel raster-graphic datum from said memory when said determiner means determines that the relative inclination of said sub-scanning line is positive,

wherein the reading time of said raster-graphic data from said memory is delayed by the time required to read said one-pixel raster-graphic datum from said memory when said determiner means determines that the relative inclination of said sub-scanning line is negative,

wherein the shift of the phase of said clock pulses, with a unit of less than 2π

, is carried out such that the phase of said clock pulses is advanced when said determiner means determines that the inclination of said sub-scanning line is positive, and

wherein the shift of the phase of said clock pulses, with a unit of less than 2π

, is carried out such that the phase of said clock pulses is delayed when said determiner means determines that the inclination of said sub-scanning line is negative.

43. The laser drawing apparatus of claim 42, wherein said second controller means comprises:

clock pulse generator means for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the respective series of clock pulses having phases which are shifted from each other within a range of 2π

;

switcher means for selectively outputting one of the series of clock pulses from said clock pulse generator means; and

regulator means for regulating said switcher means to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator means regulates said switcher means to output one of the series of clock pulses therefrom in said first clock-pulse-outputting manner when said determiner means determines that the relative inclination of said sub-scanning line is negative, and

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said second clock-pulse-outputting manner when said determiner means determines that the inclination of said sub-scanning line is positive.

44. The laser drawing apparatus of claim 41, further comprising:

detector means for detecting the positioning-marks of said workpiece; and

calculator means for calculating the inclination data of said axis, defined by the positioning-marks of said workpiece, on the basis of the detection of said positioning-marks by said detector means.

45. The laser drawing apparatus of claim 44, wherein said detector means comprises:

image sensor means for optically and electronically sensing the positioning-marks of said workpiece, with respect to a coordinate system defined in a drawing plane of said apparatus, to produce video signals containing the positioning-marks; and

video-signal processor means for processing the video signals to obtain the inclination data of said axis defined by the positioning-marks of said workpiece.

46. A laser drawing apparatus for drawing a pattern on a workpiece by scanning the workpiece with at least one laser beam in both a main-scanning direction and in a sub-scanning direction, the laser beam being modulated on the basis of raster-graphic data, read from a memory, in accordance with a series of clock pulses, scanning of the workpiece with the laser beam in the main-scanning direction being carried out by deflecting the laser beam with respect to the workpiece, scanning of the workpiece with the laser beam in the sub-scanning direction being carried out by moving the workpiece with respect to the laser beam, said apparatus comprising:

first calculator means for calculating one-pixel-dot-shift location data indicating when a main-scan-start position in said main-scanning direction should be shifted, by a distance corresponding to a one-pixel-dot size, on the basis of previously-measured pixel-dot-misalignment data of pixel-dots included in a sub-scanning line defined by the movement of said workpiece in said sub-scanning direction;

first controller means for controlling the shift of said main-scan-start position by regulating a reading time of said raster-graphic data from said memory whenever said laser beam reaches each one-pixel-dot-shift location, represented by said one-pixel-dot-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby a pixel-dot-misalignment of said pixel-dots included in said sub-scanning line can be corrected with a unit of said one-pixel-dot size;

second calculator means for calculating clock-pulse-phase-shift location data indicating where a phase of said clock pulses should be shifted, with a unit of less than 2π

, on the basis of said pixel-dot-misalignment data; and

second controller means for controlling outputting of said clock pulses so the phase of said clock pulses is shifted, with the unit of less than 2π

, whenever said laser beam reaches each clock-pulse-phase-shift- location, represented by said clock-pulse-phase-shift location data, during the movement of said workpiece in said sub-scanning direction, whereby said pixel-dot-misalignment can be finely corrected with a unit of less than said one-pixel-dot size.

47. The laser drawing apparatus of claim 46, further comprising:

first determiner means for determining whether production of a pixel-dot-misalignment at each one-pixel-dot-shift location is positive or negative, the pixel-dot-misalignment being defined as positive when produced at each one-pixel-dot-shift location in said main-scanning direction, the pixel-dot-misalignment being defined as negative when produced at each one-pixel-dot-shift location in an opposite direction to said main-scanning direction; and

second determiner means for determining whether production of a pixel-dot-misalignment at each clock-pulse-phase-shift location is positive or negative, the pixel-dot-misalignment being defined as positive when produced at each clock-pulse-phase-shift location in said main-scanning direction, the pixel-dot-misalignment being defined as negative when produced at each clock-pulse-phase-shift location in an opposite direction to said main-scanning direction,

wherein the reading time of said raster-graphic data from said memory is advanced by a time required to read a one-pixel raster-graphic datum from said memory when said first determiner means determines that the pixel-dot-misalignment is positive,

wherein the reading-timing of said raster-graphic data from said memory is delayed by the time required to read said one-pixel raster-graphic datum from said memory when said first determiner means determines that the pixel-dot-misalignment is negative,

wherein the shift of the phase of said clock pulses, with the unit of less than 2π

, is carried out such that the phase of said clock pulses is advanced when said second determiner means determines that the pixel-dot-misalignment is positive, and

wherein the shift of the phase of said clock pulses, with the unit of less than 2π

, is carried out such that the phase of said clock pulses is delayed when said second determiner means determines that the pixel-dot-misalignment is negative.

48. The laser drawing apparatus of claim 47, wherein said second controller means comprises:

clock pulse generator means for producing a plurality of series of clock pulses on the basis of a series of basic clock pulses, the respective series of clock pulses having phases which are shifted from each other within a range of 2π

;

switcher means for selectively outputting one of the series of clock pulses from said clock pulse generator means; and

regulator means for regulating said switcher means to output one of the series of clock pulses in one of a first clock-pulse-outputting manner, to cause a delay in the phase of the output clock pulses, and a second clock-pulse-outputting manner, to cause an advance in the phase of the output clock pulses,

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said first clock-pulse-outputting manner when said second determiner means determines that the pixel-dot-misalignment is negative, and

wherein said regulator means regulates said switcher means to output one of the series of clock pulses in said second clock-pulse-outputting manner when said second determiner means determines that the pixel-dot-misalignment is positive.