Apparatus and method for controlling the adjustment of optical elements in an electrophotographic apparatus

• US 4,268,165 A
• Filed: 12/17/1979
• Issued: 05/19/1981
• Est. Priority Date: 12/17/1979
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Bradmon, Paul J.
• Primary Examiner(s): WINTERCORN, RICHARD
• Application Number:
  US06/104,206
• Time in Patent Office: 519 Days
• Field of Search: 355/50, 355/51, 355/68, 355/63, 355/55, 355/56, 354/31, 354/25, 350/247, 350/101, 350/46, 324/61 R, 340/146.3 F, 358/93
• US Class Current: 355/55
• CPC Class Codes: G03B 27/526 in which the projection optics move
• CPC Class Codes: H04N 1/00013 Reading apparatus
• CPC Class Codes: H04N 1/00018 Scanning arrangements
• CPC Class Codes: H04N 1/00031 Testing, i.e. determining the result of a trial H04N1/00029 takes precedence; using test signals for transmission mode changing H04N2201/33371
• CPC Class Codes: H04N 1/00063 using at least a part of the apparatus itself, e.g. self-testing
• CPC Class Codes: H04N 1/00087 Setting or calibrating picture signal circuits H04N1/40
• CPC Class Codes: H04N 1/00819 Self-calibrating reading means
• CPC Class Codes: H04N 1/02409 Focusing, i.e. adjusting the focus of the scanning head
• CPC Class Codes: H04N 1/03 with photodetectors arranged in a substantially linear array
• CPC Class Codes: H04N 1/10 using flat picture-bearing surfaces H04N1/113, H04N1/195 take precedence
• CPC Class Codes: H04N 1/1013 with sub-scanning by translatory movement of at least a part of the main-scanning components H04N1/107 takes precedence
• CPC Class Codes: H04N 1/1026 using a belt or cable
• CPC Class Codes: H04N 2201/0458 Additional arrangements for improving or optimising scanning resolution or quality

Abstract

The optical elements of a copier are automatically aligned by positioning the elements under the control of signals from an image-dissecting scanner. The scanner, mounted to receive the image normally presented to the photoconductor, examines a master document placed in the position normally occupied by a document to be copied. Optical adjustments are made as a function of the examination of lines on the master document by the scanner. The contrast between a line and its background is maximum when optical elements between the master document and the scanner provide the sharpest focus of the line image to the scanner. Signals from the scanner for a plurality of lines on the master document determine optimum positioning of the optical elements. The scanner determines the apparent spacing between lines, which are a known distance apart on the master document, to position the optical elements for a desired magnification. The positions of selected lines, examined by the scanner, relative to absolute reference points are used to align the master document support for subsequent copying of original documents.

Digitized light-level value samples from the scanner are pushed into a last-in/first-out stack. A value significantly less than the average of the values in the stack indicates that the scanner has found a line. A plurality of scans of the line are then made while adjusting the optical elements. Corresponding light values are pushed into the stack and the average of the values stored in the stack is calculated. If the average is greater than previously calculated averages, a number of additional scans are made to insure that the best focus adjustment has been identified.

Claims

1. An apparatus for optimumly adjusting the optical elements of a copier to positions forming images of lines, on an illuminated background, which have the greatest background-to-line illumination contrast;

including an electronic scanner for examining, at different optical adjustments, point-by-point, target line and background images and generating at an output signals identifying the amount of light reflected at each point;

wherein the invention is characterized by means for indicating the adjustment at which there is greatest contrast, comprising;

stack means, connected to the electronic scanner output for retaining, in each of a plurality of positions, one of the light level representations;

first means interconnecting the scanner and stack means for sequentially entering into the same one of said positions the light level representations at each current target point as the scanner repeatedly progresses across a target line and causing the contents of each position to be placed into an adjacent position;

a storage register for retaining background light level representations;

comparison means, connected to the stack storage register and scanner, for comparing background light level representation in the storage register with the average of the representations in all of the stack positions and supplying at an output a first comparison signal if average is less than the background and a second compariaon signal if it is more;

second means, interconnecting the scanner, the stack and storage register, operable by a first comparison signal from the comparision means output, to enter into the storage register aforesaid average of the representations in all of the positions;

recognition means, connected to the comparison means output and to the scanner, operable upon the occurrence of a second signal following a first signal, to supply an indication that the lowest light level representation has occurred; and

utilization means, connected to the recognition means and to the scanner, for supplying at an output signals identifying the optical adjustment giving the lowest amount of reflected light.

2. The apparatus of claim 1, wherein the recognition means is further operable by said second signal to supply an indication for causing a fixed plurality of additional scans of the target line to occur after an increase in the amount of reflected light occurs.

3. An apparatus for optimumly adjusting the optical elements of a copier to positions forming images of lines, on an illuminated background, which have the greatest background-to-line illumination contrast;

including an electronic scanner for examining, point-by-point, target line and background images;

wherein the invention is characterized by means for indicating the optical adjustment at which there is greatest contrast, comprising;

means for detecting, during scanning, the light level and position of each background point and line examined and supplying at an output light level signals;

last-in/first-out (LIFO) storage means, connected to the detecting means output for retaining, in each of a plurality of storage positions, the light level signals and for retaining corresponding optical adjustment signals;

first means, interconnecting the detecting and the LIFO storage means, for sequentially pushing into the LIFO storage the light level as the scanner passes across a target line;

a background register, for storing signals which are a function of light levels;

comparsion means, connected to the LIFO storage and background register, for comparing light level signals in the background register with the average of the light level signals in all of the LIFO storage positions, and supplying at an output a "compare" signal if the average is less than the signals in the background register;

second means, interconnecting the background register and LIFO storage means, operable by a "compare" signal from the comparison means output, to enter into the background register aforesaid average of the signals in all of the LIFO storage positions; and

utilization means, conncted to the storage and comparison means, for supplying at an output signals identifying the optical adjustment at which the lowest amount of light is relfected.

4. The apparatus of claim 3, wherein the utilization means supplies signals only after a fixed plurality of additional target points have been examined following an increase in light between two successive optical adjustments.

5. In a system, wherein focus is determined by scanning an image for the point of greatest illumination contrast between a background and a line on the background, apparatus comprising:

scanning means, for examining the image point-by-point and indicating, as digital data, the illumination value of each point examined;

background calculation means, connected to the scanner, for calculating and retaining a background illumination value from the digital data resulting from the scanning of a plurality of background points of the image;

a data exchange bus, connected to the background calculating means;

a storage stack, connected to the bus, comprising a plurality of locations, each selectively arranged to exchange data either with the bus or with an adjacent location;

first control means, connected to the scanning calculation, bus and stack means, for entering directly into each location the background illumination value and for pushing into the stack successive illumination values from the scanning means;

comparison means, connected to the background calculation means and the stack, for indicating when the background illumination value differs from the average of all the values in the stack;

second control means, connected to the scanning, calculation, bus, stack and comparison means, for retaining in said calculation means the average of all the illumination values in the stack, if the comparison means indicates that the current background illumination value differs from the average in the stack; and

third control means, connected to the first and second control means, for indicating that the illumination value most different from the background illumination value has been retained in the calculation means, and supplying the illumination value thereof.

6. The system of claim 5, wherein the third control means additionally causes a fixed number of illumination values to be pushed into the stack when the background value is greater than the average in the stack.

7. In combination:

a master document, carrying lines on a backgroung;

an illumination source, operable to illuminate selected areas of the master document;

a scanner arranged to receive images of illuminated areas of the master document;

a digitizer, connected to the scanner, for supplying digital data representing the illumination intensity of the master document images;

averaging means, connected to the digitizer, operable to receive digital data and compute therefrom current averages of a plurality of successively received digital data;

a first storage, connected to the averaging means, operable to store the current averages one at a time;

a second storage, connected to the averaging means, operable to receive previous averages one at a time;

a comparator, connected to the first and second storages, operable when the current average in the first storage is less than the previous average in the second storage, to transfer the current average to the second storage; and

controls, connected to the scanner and comparator, operable to cause the scanner to continue to receive images when the current average is less than the previous average and to cause the scanner to receive a predetermined number of images when the current average is not less than the previous average.

8. In a combination for automatically adjusting a copier optical system for optimum focus by determining the apparent darkness of a line on a light background while changing the relationship of optical elements in the system to achieve the darkest apparent line;

the invention comprising apparatus for indicating the optical relationship giving the darkest line;

including;

receiving means, operable to receive the light level signals as the image is scanned, and to supply digital data representing the light levels and the optical adjustment corresponding thereto;

level logic means, connected to the receiving means, operable in accordance with the light level data to initially supply data which is a function of the light level of the background and, subsequently, when a first decrease in light level occurs, to supply data which indicates the light level of a line;

a first position means, connected to the receiving and level logic means, for recording the idicia of the optical relationship at which said first decrease in light level occurs;

a last-in/first-out storage stack, connected to the receiving means, comprising a plurality of individually accessible storage register locations, operable initially to hold in each register aforesaid background light level data and, subsequently, after the first decrease in light level, to receive in an input register aforesaid line light level data as data is pushed into the stack;

averaging logic, connected to the push-up stack, for receiving data stored in all the stack registers, calculating the average of the data and providing a best-focus signal when the stack average is less than a precalculated value; and

second position means, connected to the receiving means and the averaging logic, for recording the optical relationship at which the best focus signal occurs.

9. In the combination of claim 8, the averaging logic further including means for continuing to receive additional line light level data after the best-focus signal occurs, supplying another best-focus signal only if additional line light level data causes the stack average to be less than the precalculated value.

10. In a combination for automatically controlling the adjustment of a copier optical system by examining a number of lines on a background;

the invention comprising apparatus for finding the edge of a line in accordance with the level of light reflected from an image carrying the line as points on the image are scanned;

including;

receiving means, operable to receive the light level signals for each point of the image scanned, and to supply digital data representing the light levels and the position on the image of the point corresponding thereto;

level logic means, connected to the receiving means, operable in accordance with the light level data to initially supply data which is a function of the light levels of points on the background;

averaging logic, connected to the receiving means, for calculating the average of portions of the digital data, providing an indication of light level data that is significantly less than the average, and providing an edge-of-line signal when the line light level data is less than the average; and

position means, connected to the receiving means and the averaging logic, for recording the position on the image at which the edge-of-line signal occurs.

11. The combination of claim 10, further comprising apparatus for indicating the apparent focus value of the line in accordance with the level of light reflected from an image carrying the line as points on the image are scanned, including:

a stack, connected to the receiving means, comprising a plurality of individually accessible positions, operable initially to hold in each register aforesaid background light level data and, subsequently, after the edge-of-line signal, to receive in an input position aforesaid line light level data as data is pushed into the stack;

the averaging logic further including means for receiving data stored in the stack positions, calculating the average of the data and providing a best apparent focus value signal when the average is less than a specified variable value; and

aforesaid position means, recording identifiers of optical adjustments at which the best apparent focus value signal occurs.

12. The combination of claim 11, wherein the variable value represents the lowest previous average.

13. The combination of claim 11, further including alignment apparatus, for registering the position of the image with respect to fixed position reference axes, comprising:

logic means, connected to the position means, operable in accordance with signals representing the position of a plurality of points on the same line at which edge-of-line signals occur, and signals representing the position of at least one axis to supply adjustment signals representing image position changes required to register at least one line on the image with at least one reference axis; and

control means, connected to the comparison means, operable as a function of the adjustment signals to bring the image into registration with the reference axes.

14. The combination of claim 11, further including apparatus for determining and correcting the accuracy of actual magnification relative to a pedetermined, desired, magnification, comprising:

logic means, connected to the position means, operable in accordance with signals representing the position of a plurality of points, at least two of which are on different lines, to supply signals determined by the difference between points on different lines; and

comparison means, connected to the logic means, operable to supply correction signals for adjusting the optical system as a function of the signals from the logic means and signals representing the predetermined, desired, magnification.

15. A method for optimumly adjusting the optical elements of a copier to positions forming images of lines, on an illuminated background, which have the greatest background-to-line illumination contrast, comprising the steps of:

(a) examining, point-by-point, target line and background images while changing the optical element relationships;

(b) detecting, during scanning, the light level and position of each background point and line point examined;

(c) supplying, at an output, light level signals;

(d) retaining, in each of a plurality of storage positions, the light level signals;

(e) sequentially entering into a selected one of said storage positions the light level;

(f) recording the position of each current target point in sequence as the scanner progresses across a target line;

(g) causing the contents of each storage position to be moved to an adjacent position;

(h) comparing light level signals in all of the storage positions with the lowest previous value; and

(i) supplying at an output signals identifying the optical element relationship at which the lowest amount of light is reflected.

16. A process for focus determination, comprising the steps of:

(a) scanning an image for the point of greatest illumination contrast between a background and a line on the background;

(b) changing the focus setting elements between each scan;

(c) examining the image point-by-point;

(d) indicating, as digital data, the illumination value and focus for each scan;

(e) calculating a background illumination value from the digital data resulting from the scanning of a plurality of background points and the image;

(f) entering directly into each position of a last-in/first-out (LIFO) stack the background illumination value and separately storing the value;

(g) pushing into the stack each illumination value;

(h) indicating when the separately stored value differs from the average of all the values in the stack;

(i) indicating when the stack average is the most different from the background illumination; and

(j) supplying the illumination value and the focus setting thereof.