US3796494A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for interferometric measurement of displacements
Assignee: Anritsu Corp
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Filing: 1971-11-29
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Granted: 1974-03-12
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Expires: 1991-11-29
Abstract
Abstract An apparatus for interferometric measurement of displacements wherein two interferometers each with a movable mirror which are mounted on a carriage in perpendicularly intersecting relationship indicate the displacements of the carriage along the X and Y axes in the number of interference fringes passing a certain point in an interference field of view; the number of interference fringes appearing in the interference field of view of the interferometer is counted by a counter and converted to the value of displacements by an arithmetic calculator; the yawing displacements of the carriage are determined by detecting phase differece between electrcal signals obtained by photoelectrical conversion from different points in the interference field of view; and the signals thus produced actuate a servo mechanism to correct the determined yawing displacements.
Inventors
- 👤 H Takabayashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 04:42
CPC Classifications
G; G01; G01B; G01B9/00; G01B9/02; G01B9/02015; G01B9/02017; G01B9/02021; G01B9/02027
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
157 words
An apparatus for interferometric measurement of displacements which comprises: a carriage; two interferometers each of wHich includes a reference mirror, a half mirror and a movable mirror mounted on said carriage said interferometers arranged on axes which intersect at right angles; two photoelectric converteres one associated respectively with each of said interferometers and each having four photo-cells which convert four light signals appearing at four predetermined points in the interference field of view of the corresponding interferometer to four electrical signals respectively; two counters one connected respectively to said photoelectric converters to count interference fringes passing through the interference field of view according to the electrical signals from said photoelectric converter; two phase difference detectors connected respectively to said photoelectric converters to detect variations of the phase differences between said electrical signals from the corresponding photoelectric converter; and a correction device for correcting for rotational deviations of said carriage according to outputs from said phase difference detectors.
Claim 2
Independent Claim
157 words
An apparatus for interferometric measurement of displacements which comprises: a carriage; two interferometers each of wHich includes a reference mirror, a half mirror and a movable mirror mounted on said carriage said interferometers arranged on axes which intersect at right angles; two photoelectric converteres one associated respectively with each of said interferometers and each having four photo-cells which convert four light signals appearing at four predetermined points in the interference field of view of the corresponding interferometer to four electrical signals respectively; two counters one connected respectively to said photoelectric converters to count interference fringes passing through the interference field of view according to the electrical signals from said photoelectric converter; two phase difference detectors connected respectively to said photoelectric converters to detect variations of the phase differences between said electrical signals from the corresponding photoelectric converter; and a correction device for correcting for rotational deviations of said carriage according to outputs from said phase difference detectors.
Claim 3
Dependent Claim
82 words
An apparatus according to claim 1 wherein said correction device comprises an adder amplifier connected to said phase difference detection for summing up and amplifying the outputs therefrom; a servo motor connected to be actuated by output from said adder-amplifier; a potentiometer driven by said servomotor; a power amplifier connected to said adder-amplifier and potentiometer for summing up and amplifying outputs therefrom; and a correction mechanism driven by the output from said power amplifier to correct for rotational deviation of said carriage.
Claim 4
Dependent Claim
79 words
An apparatus according to claim 2 wherein said carriage comprises a carriage base and a carriage plate fitted to said carriage base through a plurality of elastic members; and said correction mechanism comprises a motor mounted on said carriage base and driven by the output from said power amplifier; a lead screw rotated by said motor; a nut reciprocated by said lead screw; and means for causing minute rotations of said carriage according to the movement of said nut.
Claim 5
Dependent Claim
166 words
An apparatus according to claim 1 wherein said correction device includes two control devices coupled respectively to said phase difference detectors and each device comprising a servo-motor connected to be actuated by the output from said phase difference detector, a potentiometer driven by said servomotor and a current amplifier for summing up and amplifying the outputs from said potentiometer and said phase difference detector; an adder-amplifier connected to average the outputs from the potentiometers of said devices; two correction mechanisms mounted on the carriage and each actuated according to output from the current amplifier to correct the rotational deviation of said movable mirror so as to realize the constant inclination of the movable mirror to the image of the reference mirror with respect to the half mirror; and an arithmetic unit to arithmetically correct the values of said counters in accordance with the signal from said adder-amplifier obtained in response to the rotational deviation of the carriage, thereby to detect an actual displacement of the carriage.
Claim 6
Dependent Claim
69 words
An apparatus according to claim 4 wherein each of said correction mechanisms includes means for pivotally fitting one end of the movable mirrors to the carriage; and a plate spring and magnetostrictive element for holding the other end of said mirrors, said magnetostrictive element changing in size according to output current supplied thereto from the amplifier of said control device thereby giving a slight rotation to said movable mirror.
Claim 7
Dependent Claim
130 words
An apparatus according to claim 1 wherein said correction device includes two control devices coupled respectively to said phase difference detectors and each comprising a servo motor actuated by output from one of said phase difference detectors, a potentiometer adjusted by said servo-motor and a voltage amplifier for summing up and amplifying outputs from said potentiometer and said phase difference detector; a correction mechanism actuated by output from the voltage amplifier of said control device to pivot the reference mirror of the interferometer so as to realize the constant inclination of the reference mirror to the image of the movable mirror with respect to the half mirror; and an arithmetic unit to arithmetically correct the values of said counters including errors caused in accordance with the deviation of the carriage.
Claim 8
Dependent Claim
67 words
An apparatus according to claim 6 wherein each of said correction mechanisms comprises a pair of piezoelectric elements disposed in contact with both ends of the reference mirror of the interferometer with the reference mirror arranged between the piezoelectric elements each changing in size according to output voltage supplied thereto from said voltage amplifier of said control device and giving a slight rotation to said reference mirror.
Claim 9
Dependent Claim
152 words
An apparatus according to claim 1 wherein said phase difference detector comprises two differential amplifiers each making a difference signal between two prescribed signals selected from among the four signals from the four photo-cells; two inverters each changing the phase of the difference signal by 180 degrees; four gates each allowing or obstructing the passage of one of said difference signals from said differential amplifiers or said inverted signals from said inverters; four comparators each of which makes a comparison between one of the four signals from the photo-cells which substantially synchronize with said difference signals and one of two reference signals proportional to the intensity of a light source and which generates a signal to open one of said gates when said difference signal or its inverted signal presents a large amplitude; and an adder for summing up the difference signals and the inverted signals which have passed through said gates.
References Cited (Backward Citations)
US3527537A
Cited
US3692413A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-11 | 1977-09-10 | 1978-03-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-11 | 1981-09-10 | 1982-03-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-11 | 1985-09-10 | 1986-03-12 | $7700.00 | Window Closed / Lapsed |