Claims
- 1. A computerized method of stage position compensation in a raster scanning laser beam pattern writing system, the writing system writing a pattern with a series of pixels, with a movable stage for providing Y direction motion for raster scanning successive rows, comprising the steps of:
- inputting stage position information from stage position encoders, the stream of position pulses from the stage position encoders having a periodicity equal to the pixel spacing;
- calculating the stage position; and
- timing the beginning of modulation of the raster scanning laser beam for each row to be scanned, using the calculated stage position, and after the stage has moved one pixel.
- 2. The method of claim 1, including the step of inputting the stage position information from a glass scale encoder.
- 3. The method of claim 1, including the step of inputting the stage position information from a laser interferometer.
- 4. The method of claim 1, wherein the step of calculating the stage position, is a step of calculating the X coordinate of the stage position to compensate for uncertainty in the X position of the stage.
- 5. The method of claim 1, wherein the step of calculating the stage position, is a step of calculating the Y coordinate of the stage position to compensate for uneven speed of travel of the stage in the Y direction.
- 6. The method according to claim 1, wherein position compensation is accomplished by programmed pulse rate scaling utilizing an arithmetic accumulator, including the step of adding a constant to the accumulator, for each incoming stage position pulse.
- 7. The method according to claim 6, wherein the position pulse may indicate a movement in either the positive or negative direction, and the constant added to the accumulator is positive for each positive direction pulse and the complement of the constant is added for each position pulse in the negative direction.
- 8. The method according to claim 7, wherein the constant added is calculated by dividing the number of input pulses to the accumulator by the number of output pulses form the accumulator and multiplying the resultant by the maximum value that can be stored in the accumulator.
Parent Case Info
This is a continuation of application No. 07/173,492, filed Mar. 25, 1988.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
4705395 |
Hageniers |
Nov 1987 |
|
4796038 |
Allen et al. |
Jan 1989 |
|
Continuations (1)
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Number |
Date |
Country |
Parent |
173492 |
Mar 1988 |
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