FRINGE-COUNTING READOUT SYSTEM FOR A LENGTH-MEASURING LASER INTERFEROMETER
A solid-state detection and readout system that counts fringes at a maximum rate of 250,000/sec was developed for use with a length-measuring laser interferometer. The system consists of a photodetector, a phase detector, and a bidirectional counter. ln response to translation of a measuring probe, the interferometer produces interference fringes which appear as variations in light intensity. The photodetector senses these variations and converts them into two electrical signals. These signals have a phase difference of 90 degrees, either leading or lagging, depending on the direction in which the measuring probe is moving. The phase detector determines the phase relation and, for each quarter- cycle input from the photodetector, transmits a pulse to the appropriate channel (to indicate leading or lagging) of the bidirectional counter. The bidirectional counter displays continuously the algebraic difference between the number of pulses received on one channel and the number received on the other. Since each pulse corresponds to a displacement of about 1.6 microinches, the readout system indicates the number of 1.6-microinch increments by which the measuring probe of the interferometer was displaced from an arbitrary reference position. (auth)
- Research Organization:
- Sandia Corp., Livermore Lab., Livermore, Calif.
- DOE Contract Number:
- AT(29-1)-789
- NSA Number:
- NSA-18-015695
- OSTI ID:
- 4063332
- Report Number(s):
- SC-TM-162-63-81
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- United States
- Language:
- English
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