STEP AND REPEAT CAMERA WITH COMPUTER CONTROLLED FILM TABLE

• US 3,572,925 A
• Filed: 10/18/1967
• Issued: 03/30/1971
• Est. Priority Date: 10/18/1967
• Status: Expired due to Term

• Current Assignee: Billy D. Ables, Charles Fort, Edmund D. Jackson
• Original Assignee: Billy D. Ables, Charles Fort, Edmund D. Jackson
• Inventors: Ables, Billy D., Fort, Charles, Jackson, Edmund D.
• Application Number:
  US04/676,211
• Time in Patent Office: 1,259 Days
• US Class Current: 355/46
• CPC Class Codes: G03B 27/44 for multiple copying of the same original at the same time G03B27/34, G03B27/53 take precedence
• CPC Class Codes: G03F 7/70275 Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem projection systems
• CPC Class Codes: G03F 7/70716 Stages
• CPC Class Codes: G03F 7/70775 Position control, e.g. interferometers or encoders for determining the stage position
• CPC Class Codes: G03F 7/70883 of optical system
• CPC Class Codes: G05B 19/188 characterised by special applications and not provided for in the relevant subclasses, (e.g. making dies, filament winding)

Abstract

A film support table is movable in the X and Y coordinate directions by X and Y drive systems. A laser interferometer and fringe counter detects movement of the table in the X and Y coordinate directions by fringe counts. A projection system simultaneously projects a plurality of images onto the film carried by the table after the table is moved to each of a plurality of predetermined exposure positions. A reference detector system detects when the table is at a zero reference position and resets the counters. A digital computer is programmed to compute the coordinate of each exposure position and then, based on the current barometric pressure, compute the number of fringe counts from the reference position to the first exposure position. The computer then operates the drive system in such a manner as to move the table to the exposure position by continuously computing the position and velocity of the table from the readings of the fringe counters. Then the table is maintained at the exposure position during the exposure period by continuously determining the position of the table from the fringe counters and operating the drive system to produce forces for correcting the positional error.

Claims

1. The step and repeat camera which comprises:

first means for supporting a photographic plate and second means for projecting an image onto a photographic plate supported by the first means, the first and second means being mounted for relative movement in X and Y coordinate directions;

drive means for moving the first and second means in the relative X and Y coordinate directions;

means for sensing movement of the first and second means in the relative X and Y directions and producing X and Y coordinate position information; and

control means responsive to the position information for operating the drive means in a manner to move the first and second means to selected relative coordinate positions and to maintain the relative coordinate position during exposure of a photographic plate supported by the first means.

2. The step and repeat camera defined in claim 1 wherein the movement-sensing means includes interferometer means for producing interference fringe lines and counter means for maintaining a count of the fringe lines produced by relative movement of the first and second means, and the control means includes a digital computer for calculating the relative position of the first and second means from the count of the counter means and operating the drive means in real time in response to the calculated position information.

3. The step and repeat camera defined in claim 2 wherein the movement-sensing means includes at least two detectors positioned to detect separate parts of the interference fringe lines, and logic means responsive to the detectors for producing data indicative of the direction of movement of the table.

4. The step and repeat camera which comprises:

means defining a plurality of vertically disposed optical axes;

a table for supporting a photographic plate aligned generally with each of the plurality of vertically disposed optical axes;

means supporting the table for horizontal movement in X and Y coordinate directions;

projection means for projecting an image along each of the optical axes;

drive means for moving the table in the X and Y coordinate directions;

interferometer and counter means for measuring the movement of the table in the X and Y coordinaTe directions by maintaining a count of interference fringe lines produced by movement of the table in each of the coordinate directions; and

control means coupled to the counter means and the drive means for controlling the drive means, the control means including a computer programmed to operate the drive means to move the table to a reference position, compute the number of fringe counts in each of the X and Y coordinate directions from the reference position to a selected coordinate position, operate the drive system to move the table to the selected coordinate position, and operate the drive system to maintain the table in the selected coordinate position within established tolerances during a period of time necessary to expose the photographic plates with the respective images.

5. The step and repeat camera defined in claim 4 wherein the projection means comprises:

upright support means extending above the table;

a lens stage supported above the table by the upright support means for adjustable movement in the vertical direction, said lens stage including a lens system for each optical axis; and

an upper stage adjustably supported above the lens stage by the upright means for adjustable movement in the vertical direction, the upper stage including a light source for each optical axis and means for supporting a photo transparency at each opticaL axis.

6. The step and repeat camera defined in claim 4 further characterized by:

X comparator means for producing an X comparator interrupt signal when the count of the interference fringe line counter for the X coordinate direction equals the count set into the X comparator means, the count of the X comparator means being settable by the computer;

Y comparator means for producing a Y comparator interrupt signal when the count of the interference fringe line counter for the Y coordinate direction equals the count set into the Y comparator means, the count of the Y comparator means being settable by the computer; and

wherein the computer is programmed to respond to the X comparator interrupt signal to retard movement of the table in the X coordinate direction and to respond to the Y comparator interrupt signal to retard movement of the table in the Y coordinate direction.

7. In a system for controlling the movement of a member along an axis with precision, the combination of:

laser interferometer means for producing interference fringe lines as a measure of the distance the member moves along the axis;

detector means for detecting the interference fringe lines and producing a first signal representative of each fringe line and a second signal representative of the direction of movement of the member;

reversible counter means for counting the first signals in a direction determined by the second signal such that the count of the counter means is representative of the position of the member relative to a reference position;

drive means for moving the member in each direction along the axis; and

digital computer means for controlling the drive means in real time in response to the count of the counter means to control movement of the member along the axis.

8. The combination defined in claim 7 wherein the detector means for detecting the interference fringe lines comprises at least two photodetectors spaced in the interference pattern to produce two out-of-phase output signals, threshold means for converting each of the output signals to logic levels, and logic means for decoding the logic levels to produce the first and second signals.

9. The combination defined in claim 7 further characterized by comparator means for producing a comparator interrupt signal when the count of the counter equals the count set into the comparator, the comparator being set by the computer, and wherein the computer is programmed to retard movement of the member upon the occurrence of the comparator interrupt signal.

10. The step and repEat camera which comprises:

a table for supporting a plurality of photographic plates with each generally aligned with an optical axis;

means for successively stepping the table to a plurality of exposure positions;

upright support means extending above the table;

a lens stage supported above the table by the upright support means for adjustable movement in the vertical direction, said lens stage including a lens system for each optical axis; and

an upper stage adjustably supported above the lens stage by the upright means for adjustable movement in the vertical direction, the upper stage including a light source for each optical axis and means for supporting a photo transparency at each optical axis.

11. In a system for controlling the movement of a member along an axis, the combination of:

means for producing an origin interrupt signal when the member passes through a reference position;

laser interferometer means for producing interference fringe lines as a measure of the distance the member moves along the axis;

detector means for detecting the interference fringe lines and producing a count signal representative of each fringe cycle and a second signal representative of the direction of movement of the member;

reversible counter means for counting the counts of the counter means in a direction determined by the second signal such that the count of the counter means is representative of the position of the member relative to a reference position;

drive means for moving the member in each direction along the axis;

comparator means for producing a comparator interrupt signal when the count of the counter equals the count set into the comparator; and

digital computer means interfaced with the remainder of the system and programmed to;

operate the drive means in a manner to move the table past the reference position and store the count of the counter upon the occurrence of the origin interrupt signal, compute the new position to which the table is to be moved in fringe counts, compute the distance in fringe counts from the reference point to a calculation point at which a retard calculation should be made, set the count of the calculation point into the comparator, operate the drive means to apply an accelerating force to the member until the member has attained a predetermined velocity, pulse the drive means to maintain the predetermined velocity until the table reaches the calculation point and a comparator interrupt signal is produced, calculate the point in fringe counts from the reference point at which a retard force is to be applied and set the count into the comparator, maintain the velocity of the table until the table reaches the retard point and a comparator interrupt is produced, and operate the drive system to apply said retard force while measuring the velocity until the velocity has reached a predetermined minimum value.

12. The combination defined in claim 11 wherein the computer means is further programmed to repeatedly determine the position of the member relative to the desired position by comparing the actual count of the counter to the count representing the desired position, and operating the drive means to apply a force to the member acting in a direction to move the member toward the desired position.

13. In a system for controlling the movement of a member along an axis, the combination of laser interferometer means for producing an interference fringe pattern in response to movement of the member, at least two photodectectors spaced in the interference pattern to produce two out-of-phase output signals, threshold means for converting each of the output signals to logic levels, and logic means for decoding the logic levels to produce first and second signals.