US3572935A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fringe counter for interferometers
Assignee: National Aeronautics and Space Administration
•
Filing: 1968-10-09
•
Granted: 1971-03-30
•
Expires: 1988-10-09
Abstract
Abstract A device for counting fringes produced by an interferometer. An interferometer with a single photomultiplier is used to determine the magnitude and direction of motion of an object to a digital sensitivity of one-eighth of a wavelength. By an electronic squaring technique the digital sensitivity of the device can be increased to one-sixteenth or one thirty-second of a wavelength.
Inventors
- 👤 William E Howell
- 👤 Kazmere C Romanczyk
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:27
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/266; G01B; G01B9/00; G01B9/02; G01B9/02041; H; H03; H03M; H03M1/00; H03M1/12; H03M1/22; H03M1/24; H03M1/28; H03M1/30
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
240 words
A device for counting electrical fringes whose wavelength varies proportional to a variable comprising: means receiving said electrical fringes for producing the fundamental and second harmonic envelopes of said fringes; means receiving said fundamental envelopes for producing a first voltage level when the carrier in said fundamental envelopes is a first phase and for producing a second voltage level when the carrier in said fundamental envelopes is a second phase; means receiving said second harmonic envelopes for producing said first voltage level when the carrier in said second harmonic envelopes is said first phase and for producing said second voltage level when the carrier in said second harmonic envelopes is said second phase; logic circuit means receiving the outputs from the last two mentioned means for producing a pulse on the first of its two output terminals when there is a change in the output level of either of the last two mentioned means and the last change was one of two possible changes and for producing a pulse on the second of its two output terminals when there is a change in the output level of either of the two last mentioned means and the last change was the other of two possible changes; and a bidirectional counter for counting the pulses produced by said logic circuit means whereby the count on said bidirectional counter at any instant is indicative of the value of said variable at that instant.
Claim 2
Independent Claim
240 words
A device for counting electrical fringes whose wavelength varies proportional to a variable comprising: means receiving said electrical fringes for producing the fundamental and second harmonic envelopes of said fringes; means receiving said fundamental envelopes for producing a first voltage level when the carrier in said fundamental envelopes is a first phase and for producing a second voltage level when the carrier in said fundamental envelopes is a second phase; means receiving said second harmonic envelopes for producing said first voltage level when the carrier in said second harmonic envelopes is said first phase and for producing said second voltage level when the carrier in said second harmonic envelopes is said second phase; logic circuit means receiving the outputs from the last two mentioned means for producing a pulse on the first of its two output terminals when there is a change in the output level of either of the last two mentioned means and the last change was one of two possible changes and for producing a pulse on the second of its two output terminals when there is a change in the output level of either of the two last mentioned means and the last change was the other of two possible changes; and a bidirectional counter for counting the pulses produced by said logic circuit means whereby the count on said bidirectional counter at any instant is indicative of the value of said variable at that instant.
Claim 3
Dependent Claim
18 words
A device for counting electrical fringes according to claim 1 wherein said second voltage level is ground potential.
Claim 4
Dependent Claim
33 words
A device for counting electrical fringes according to claim 1 including means for squaring said fringes before the fundamental and second harmonic envelopes are produced whereby the sensitivity of the counter is doubled.
Claim 5
Independent Claim
275 words
A device for counting the fringes produced by an interferometer of the type that includes a laser source, a beam splitter, a reference mirror driven at a given frequency and a second mirror attached to the object whose position is to be monitored combined such that the fringes produced thereby oscillate across the face of a single photomultiplier tube comprising: means connected to the output of said photomultiplier tube for producing the fundamental and second harmonic envelopes of said fringes; means receiving said fundamental envelop for producing a first voltage level during alternate cycles of said fundamental envelope and for producing a second voltage level during the other alternate cycles of said fundamental envelope; means receiving said second harmonic envelope for producing said first voltage level during alternate cycles of said second harmonic enVelope and for producing said second voltage level during the other alternate cycles of said second harmonic envelope; logic circuit means receiving the outputs from the last two mentioned means for producing a pulse on the first of its two output terminals when there is a change in the output level of either of the last two mentioned means and the last change was one of two changes and for producing a pulse on the second of its two output terminals when there is a change in output of either of the two last mentioned means and the last change was the other of two possible changes; and a bidirectional counter for counting the pulses produced by said logic circuit means whereby the count on said bidirectional counter at any instant is indicative of the position of said object at that instant.
Claim 6
Independent Claim
275 words
A device for counting the fringes produced by an interferometer of the type that includes a laser source, a beam splitter, a reference mirror driven at a given frequency and a second mirror attached to the object whose position is to be monitored combined such that the fringes produced thereby oscillate across the face of a single photomultiplier tube comprising: means connected to the output of said photomultiplier tube for producing the fundamental and second harmonic envelopes of said fringes; means receiving said fundamental envelop for producing a first voltage level during alternate cycles of said fundamental envelope and for producing a second voltage level during the other alternate cycles of said fundamental envelope; means receiving said second harmonic envelope for producing said first voltage level during alternate cycles of said second harmonic enVelope and for producing said second voltage level during the other alternate cycles of said second harmonic envelope; logic circuit means receiving the outputs from the last two mentioned means for producing a pulse on the first of its two output terminals when there is a change in the output level of either of the last two mentioned means and the last change was one of two changes and for producing a pulse on the second of its two output terminals when there is a change in output of either of the two last mentioned means and the last change was the other of two possible changes; and a bidirectional counter for counting the pulses produced by said logic circuit means whereby the count on said bidirectional counter at any instant is indicative of the position of said object at that instant.
Claim 7
Dependent Claim
25 words
A device for counting fringes in accordance with claim 4 wherein the two means for producing first and second voltage levels are both phase-sensitive detectors.
Claim 8
Dependent Claim
38 words
A device for counting fringes in accordance with claim 4 including means for squaring the output of said photomultiplier tube before it is applied to the remainder of the circuit whereby the sensitivity of the device is doubled.
Claim 9
Dependent Claim
136 words
A device for counting fringes in accordance with claim 4 wherein said logic circuit means includes circuitry for producing a pulse on its first output terminal when SnFo+ SnFo is true and includes circuitry for producing a pulse on its second output terminal when SnFo+ SnFo is true where Sn is a logical 1 when said means receiving said second harmonic envelope produces said first voltage level and is a logical 0 when it produces said second voltage level and where Fo is a logical 1 if just prior to the last change in voltage level of either the means receiving the fundamental or the means receiving the second harmonic, the means receiving the fundamental was producing said first voltage level and Fo is a logical 0 if this means was producing said second voltage level.
References Cited (Backward Citations)
US3409375A
Cited
US3414718A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-03-29 | 1974-09-28 | 1975-03-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-29 | 1978-09-28 | 1979-03-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-29 | 1982-09-28 | 1983-03-30 | $7700.00 | Window Closed / Lapsed |