US3856412A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical noncontacting gauge
Assignee: Zygo Corp
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Filing: 1973-09-06
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Granted: 1974-12-24
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Expires: 1993-09-06
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 rotating 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 at least about half the width of the laser beam, to generate a modulated signal whose spatial frequency is independent of variations in the speed of scanning and intensity of the laser beam, squaring off this modulated signal, and then dividing up the squared signal with a vernier during those portions of the signal corresponding to the edges of the test object.
Inventors
- 👤 C Zanoni
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 17:09
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/02
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
209 words
An electrooptical device for measuring the crosssectional width of an opaque object which comprises (1) a source of radiant energy which provides a narrow beam; (2) rotating means for scanning said beam; (3) means for collecting and splitting said scanned beam into first and second portions, and for passing (4A) said first portion of said beam through a precision scale, with alternate transparent and opaque bands of equal width, at least half the width of the diameter of said scanned beam, onto a first photodetector to produce a sinusoidal signal with spatial frequency corresponding to the spacings on the precision scale; (4B) said second portion of said beam past an opaque object onto a second photodetector for photoelectrically detecting the modulation of the scanned light beam by said test object; (5) means for squaring off said sinusoidal signal derived from said first portion of said scanned beam; (6) means for generating a fine vernier; and (7) means connected to the signals from said squaring off means, said vernier, and said second photodetector for measuring the number of full pulses and vernier pulses during the interruption of said second portion of said beam by said test object, to produce a signal corresponding to the cross-sectional width of said test object.
Claim 2
Dependent Claim
209 words
An electrooptical device for measuring the crosssectional width of an opaque object which comprises (1) a source of radiant energy which provides a narrow beam; (2) rotating means for scanning said beam; (3) means for collecting and splitting said scanned beam into first and second portions, and for passing (4A) said first portion of said beam through a precision scale, with alternate transparent and opaque bands of equal width, at least half the width of the diameter of said scanned beam, onto a first photodetector to produce a sinusoidal signal with spatial frequency corresponding to the spacings on the precision scale; (4B) said second portion of said beam past an opaque object onto a second photodetector for photoelectrically detecting the modulation of the scanned light beam by said test object; (5) means for squaring off said sinusoidal signal derived from said first portion of said scanned beam; (6) means for generating a fine vernier; and (7) means connected to the signals from said squaring off means, said vernier, and said second photodetector for measuring the number of full pulses and vernier pulses during the interruption of said second portion of said beam by said test object, to produce a signal corresponding to the cross-sectional width of said test object.
Claim 3
Dependent Claim
28 words
The device of claim 1, in which the width of the bands of said precision scale is between half the diameter and the diameter of the scanned beam.
Claim 4
Dependent Claim
15 words
The device of claim 1, in which the source of radiant energy is a laser.
Claim 5
Dependent Claim
25 words
The device of claim 2, in which means for generating the vernier is a fixed frequency clock, and the scanning means is operated synchronously therewith.
Claim 6
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 (8) of claim 1.
Claim 7
Dependent Claim
85 words
The device of claim 4, in which the scanned beam is focused onto the first photodetector through a tangent-corrected lens, and the diameter of the test object is measured by counting the number of full pulses during which the scanned beam is blocked by the test object, and measuring the width of the partial pulses during which the scanned beam is blocked by the test object by counting the number of vernier cycles of the high frequency clock during those portions of the partial pulses.
Claim 8
Dependent Claim
170 words
The device of claim 4, in which the scanned beam is focused onto the first photodetector through an ordinary collimating lens and the diameter of the test object is measured by counting the number of full pulses during which the scanned beam is blocked by the test object, and measuring the width of the partial pulses during which the scanned beam is blocked by the test object by recycling a portion of signal from the high frequency clock through a counter which measures the difference between the number of cycles from said high frequency clock and a preset number, and applying the signal from this counter to a rate multiplier which also receives signal direct from the high frequency clock, to produce a modulated output which gives a fixed number of frequency cycles for each full pulse from the first photodetector, and counting the number of frequency cycles from this modulated output during those portions of the partial pulses during which the scanned beam is blocked by the test object.
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 |