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Digital Compensation for Electrooptical System

IP.com Disclosure Number: IPCOM000081105D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Wallace, LJ: AUTHOR

Abstract

This optically coupled system may be used with slotted timing disks and the like to provide accurate timing pulses during shaft rotation, or other motion of the masking device. Long-term variations in the system are compensated by controlling the light output of a solid-state light source, by control of the current therethrough via digital circuitry. Since the light output from such solid-state devices is proportional to the operating current within the operating region, a linear system response may be achieved.

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Digital Compensation for Electrooptical System

This optically coupled system may be used with slotted timing disks and the like to provide accurate timing pulses during shaft rotation, or other motion of the masking device. Long-term variations in the system are compensated by controlling the light output of a solid-state light source, by control of the current therethrough via digital circuitry. Since the light output from such solid-state devices is proportional to the operating current within the operating region, a linear system response may be achieved.

In operation, assume the output of the light-emitting diode (LED) light source is high, and that the up-down binary counter BC is starting at a value of 8. As a light pulse is transmitted by the mask motion, from LED to the phototransistor PTX, the output from PTX will rise and reach the threshold values for operational amplifier OA1 and then OA2, in that order, as determined by the settings of resistors 1 and 3, respectively.

Output from OA1 will supply a system output signal at EO, and via capacitor C1, will turn on the control trigger CT. When the threshold of OA2 is reached, it will supply an output effective to turn trigger CT off.

When the light is cut off from PTX, the amplifiers OA2 and OA1 will turn off their respective outputs in that order. When the output EO goes down, a signal is provided via inverter 5 and AND gate 7 to drive counter BC, and since the down control line DWN is effective because C...