US3856411A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical noncontacting diameter gauge
Assignee: Zygo Corp
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Filing: 1973-08-14
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Granted: 1974-12-24
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Expires: 1993-08-14
Abstract
Abstract An electrooptical sensor is described for providing an output proportional to the cross section of an object, i.e., the diameter of a cylinder. A beam of laser light from a rapidly oscillating mirror is scanned across the test object. By photoelectrically sensing when the laser beam is modulated on or off by the edge of the object, using the first and second derivatives of the output of the sensor to accurately determine the point of passage, the diameter of the test object can be measured, using an auxiliary photoelectric output obtained by passing a part of the scanning laser beam onto a sensor over a precision grating or scale with markings which generate a modulated signal whose spatial frequency is independent of variations in the speed of scanning and intensity of the laser beam, and then breaking up the signal with a vernier which is phase-locked to the signal from the sensor. The markings are preferably as small as possible, i.e., about half the width of the laser beam.
Inventors
- 👤 C Zanoni
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 06:38
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/02
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
207 words
An electrooptical device for measuring the cross-sectional width of an opaque test object which comprises (1) a source of radiant energy which provides a narrow beam; (2) means for scanning this beam in a direction perpendicular to its direction of propagation; (3) means for collecting and splitting said scanned beam into first and second portions and (4A) to direct said first portion of said beam onto a first photodetector through a precision scale with alternate transparent and opqaue bands at least about half the width of the diameter of said scanned beam, to produce a sinusoidal signal whose spatial frequency corresponds to the spacings on said precision scale, and thence onto (5) means for breaking up said signal to produce a much higher frequency locked in phase to the output of said first photodetector, and (4B) to direct said second portion of said beam past said opaque test object onto a second photodetector which detects the modulation of said scanned beam by said test object; and (6) means connected to the signals derived from both portions of said beam for measuring the number of pulses while the energy is interrupted by the test object to produce a signal corresponding to the cross-sectional width of said test object.
Claim 2
Dependent Claim
207 words
An electrooptical device for measuring the cross-sectional width of an opaque test object which comprises (1) a source of radiant energy which provides a narrow beam; (2) means for scanning this beam in a direction perpendicular to its direction of propagation; (3) means for collecting and splitting said scanned beam into first and second portions and (4A) to direct said first portion of said beam onto a first photodetector through a precision scale with alternate transparent and opqaue bands at least about half the width of the diameter of said scanned beam, to produce a sinusoidal signal whose spatial frequency corresponds to the spacings on said precision scale, and thence onto (5) means for breaking up said signal to produce a much higher frequency locked in phase to the output of said first photodetector, and (4B) to direct said second portion of said beam past said opaque test object onto a second photodetector which detects the modulation of said scanned beam by said test object; and (6) means connected to the signals derived from both portions of said beam for measuring the number of pulses while the energy is interrupted by the test object to produce a signal corresponding to the cross-sectional width of said test object.
Claim 3
Dependent Claim
55 words
The device of claim 1, in which the bands of the precision scale are between half the width of, to equal in width to, the diameter of said scanned beam and are equal in width to each other, whereby the signal produced has the form of a regular sine wave with a fixed spatial frequency.
Claim 4
Dependent Claim
126 words
The device of claim 2, in which (a) the output from the second photodetector is differentiated to produce signals of maximum intensity adjacent points corresponding to the edges of said test object; (b) a portion of said differentiated signal is further differentiated to Produce signals of zero intensity at points corresponding to the edges of said test object; (c) a portion of the first differentiated signal is fed to a switch to which the second differentiated signal is also fed, which switch passes the second differentiated signal only for a limited period adjacent the peaks of said first differentiated signal; and (d) the signal from said switch is fed into a zero-crossing detector to produce a signal which is fed into means (5) of claim 1.
Claim 5
Dependent Claim
15 words
The device of claim 3, in which the source of radiant energy is a laser.
Claim 6
Dependent Claim
50 words
The device of claim 3, in which the bands of the precision scale are about half the width of the diameter of said scanned beam, and are equal in width to each other, whereby the signal produced has the form of a regular sine wave with a fixed spatial frequency.
References Cited (Backward Citations)
US3744915A
Cited
US3765774A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-23 | 1978-06-24 | 1978-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-23 | 1982-06-24 | 1982-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-23 | 1986-06-24 | 1986-12-24 | $7700.00 | Window Closed / Lapsed |