FILTER(OPCSDEFS) Optical Printer Control System FILTER(OPCSDEFS) NAME filter - define the channel that controls the filter wheel USAGE filter [chan] [tvels] [vels] EXAMPLES filter h 8 4 10 16 20 20 16 10 4 | | --------------------- | | | | | The 8 velocity samples sent to the motor, | | including ramping. Sum is 100. | | | 8 velocity samples | Channel with filter wheel DESCRIPTION This command defines which channel controls a 'wedge wheel', or 'filter wheel'. These settings configure the AUTOFILT(OPCS) command. Most filter wheels usually have 20 filters. If the motor controling it is 2000 pulses per revolution, and the motor is geared 1:1, then it would take 100 pulses to move the motor 1 filter position. [chan] is the channel controlling the filter wheel. [tvels] is the number of velocity samples specified. [vels] are the velocity samples. These values are the raw speed values (velocities) sent to the motor. These values should smoothly ramp up then back down. The sum of these values should be the number of pulses to move to the next filter position. These values are configured by hand, since the idea is to get the motor to move to the next position in as little time (as few values) as possible, without stalling the motor. At the fastest camera speed, you will want the filter wheel to be at rest while the camera is exposing film. NOTES When AUTOFILT(OPCS) is enabled, the filter wheel will begin moving after each camera frame exposes, at the moment the camera shutter has completely closed. This is determined by the MRP(OPCSDEFS) value. If you find the filter wheel starts its movement while the shutter is still open, you should either decrease the MRP(OPCSDEFS) value, or make sure your home position for the shutter is accurate.
The following diagram shows the travel of the camera shutter through a full rotation, from left to right. The numbers indicate the pulses throughout the rotation of a shutter that is 2000 pulese per rev: OPEN -- __________ / \ / \ / \ CLOSED -- ____________/ \___________ | | | | | 0 500 1000 1500 2000 If MRP(OPCSDEFS) is 500, then the AUTOFILT command will begin moving the filter wheel at the 1500 position, ie. 2000 - 500. The shutter should be fully closed at that position. If you decrease the MRP(OPCSDEFS) value to 400, AUTOFILT will begin moving the filter wheel at the 1600 position, ie. 2000 - 400. SEE ALSO AUTOFILT(OPCS) - enable auto-wedging with a filter wheel MRP(OPCSDEFS) - maximum ramp pulses for shutter motors ORIGIN Version K1.12e+ Gregory Ercolano, Venice California 04/10/98