US3853406A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Differential optical noncontacting diameter gauge utilizing a pair of linearly scanning light beams sequentially scanning the test piece
Assignee: Zygo Corp
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Filing: 1973-12-03
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Granted: 1974-12-10
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Expires: 1993-12-03
Abstract
Abstract An electrooptical sensor is described for providing an output proportional to the difference between the cross section of an object, e.g. the diameter of a cylinder, and a known preset value. Two parallel beams of laser light separated by a known preset distance are scanned across the test object. By photoelectrically sensing when each laser beam is modulated on or off by the edges of the object, an electrical pulse whose width is equal to the difference between the object diameter and the spacing of the two laser beams is obtained. The two parallel, offset scanning laser beams are produced by reflecting two laser beams separated by a preset angle from a uniformly rotating mirror, or a multifaceted prism, placed at the focus of a lens; the beams are polarized at different orientations, preferably orthogonal to each other, so that they can be readily separated in the receiver portion of the device. The passage of the beams past the edges of the object is determined by the first and second derivatives of the output of each photodetector to accurately determine the point where the center of each laser beam coincides with an edge of the object.
Inventors
- 👤 C Zanoni
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 01:12
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/02
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
176 words
An electrooptical device for measuring the cross-sectional width of an opaque test object which comprises (1) a source of radiant energy which produces a narrow beam; (2) means for splitting said beam into two parallel beams of nearly equal intensity and of such different polarization that the two beams can be readily separated; (3) means for adjusting the distance between the two parallel beams; (4) means for focusing said two beams onto a reflecting uniformly rotating surface which reflects the beams onto (5) means for collimating said reflected beams to provide a pair of linearly-scanned light beams which are separated by a uniform preset distance and which can be interrupted by the object; (6) means for collecting, separating, and separately photosensing the two linearly-scanned beams to produce two pulses corresponding to the interruption and noninterruption of the beams by the opaque test object; and (7) means for processing said pulses to produce a pulse whose width is proportional to the difference between the width of the test object and the distance between the two parallel-scanned beams.
Claim 2
Dependent Claim
176 words
An electrooptical device for measuring the cross-sectional width of an opaque test object which comprises (1) a source of radiant energy which produces a narrow beam; (2) means for splitting said beam into two parallel beams of nearly equal intensity and of such different polarization that the two beams can be readily separated; (3) means for adjusting the distance between the two parallel beams; (4) means for focusing said two beams onto a reflecting uniformly rotating surface which reflects the beams onto (5) means for collimating said reflected beams to provide a pair of linearly-scanned light beams which are separated by a uniform preset distance and which can be interrupted by the object; (6) means for collecting, separating, and separately photosensing the two linearly-scanned beams to produce two pulses corresponding to the interruption and noninterruption of the beams by the opaque test object; and (7) means for processing said pulses to produce a pulse whose width is proportional to the difference between the width of the test object and the distance between the two parallel-scanned beams.
Claim 3
Dependent Claim
21 words
The device of claim 1, in which the means (2) split the narrow beam into two parallel beams of orthogonal polarization.
Claim 4
Dependent Claim
17 words
The device of claim 1, in which the said reflecting uniformly rotating surface is a multifaceted prism.
Claim 5
Dependent Claim
41 words
The device of claim 1, in which the said reflecting uniformly rotating surface is a multifaceted prism with the pyramidal angle of each facet offset from 90* by a small amount, and with individual adjoining facets having slightly different pyramidal angles.
Claim 6
Dependent Claim
16 words
The device of claim 1, in which the source of radiant energy is a laser beam.
Claim 7
Dependent Claim
148 words
The device of claim 1, in which the edges of the test object are determined by means which (a) differentiate the output of each photosensing means to produce signals of maximum intensity at points corresponding to the edges of said test object; (b) further differentiate a portion of each of said differentiated signals to produce signals of zero intensity at points corresponding to the edges of said test object; (c) feed a portion of the first differentiated signal 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 further differentiated signal; and (d) feed the signal from said switch to a zero-crossing detector which feeds the signal to the means which form the pulses corresponding to the said interruption and noninterruption of the beams by the opaque test object.
Claim 8
Dependent Claim
137 words
The device of Claim 1, in which the means (7) for processing the said pulses, designated A and B, corresponding to the interruption and noninterruption of the beams by the opaque test object, comprise (a) means to generate the pulse C derived from the leading edge of the pulse A so as to bridge any gap or overlap between the trailing edge of pulse A and the leading edge of pulse B; (b) means to generate pulses A and B complementary to pulses A and B; (c) means to derive A.B.C and A.B.C from A, B and C; and (d) means to measure the time during which either A.B.C or A.B.C is non-zero to determine the amplitude and sign of the difference between the distance between the two parallel-scanned beams and the width of the test object.
Claim 9
Dependent Claim
58 words
The device of claim 5, in which the collimating means (5) is a lens which follows an h f theta relation, where theta is the angle between the ray and the optical axis at the focal point of the lens, f is the focal length of the lens, and h is the ray height of the collimated ray.
References Cited (Backward Citations)
US3665202A
Cited
US3710128A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-09 | 1978-06-10 | 1978-12-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-09 | 1982-06-10 | 1982-12-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-09 | 1986-06-10 | 1986-12-10 | $7700.00 | Window Closed / Lapsed |