US3630622A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for determining the relative movement of an object by means of a grating mechanically connected to the object
Assignee: US Philips Corp
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Filing: 1969-08-06
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Granted: 1971-12-28
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Expires: 1989-08-06
Abstract
Abstract An apparatus for detecting the motion of an object attached to a grating wherein light impinges twice on different areas of the grating, first diffracting the light into various ordered subbeams. A phase-anisotropic element located in at least one subbeam and an electro-optic or magneto-optic modulator placed in the path of the composite beam produce orthogonally related beams, which after separation produce signals having a mutual phase difference varying about 180*.
Inventors
- 👤 Hendrik De Lang
- 👤 Gijsbertus Bouwhuis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 16:12
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/36; G01D5/38
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
149 words
An apparatus for determining the relative movement of an object, comprising a grating mechanically connected to the object and having the lines thereof aligned at right angles to the direction of movement, a source of polarized radiation for projecting polarized radiation on a first portion of the grating whereby the beam is diffracted into a plurality of subbeams, a phase-anisotropic element in the path of at least one of the subbeams, an electromagnetic field responsive birefringent optical modulator in the path of the radiation, means for directing the subbeams on to another portion of the grating whereby the subbeams are recombined, a beam splitter in the path of the recombined beam for spatially separating orthogonally polarized portions of the Recombined beam, a photoelectric detector in the path of each of the spatially separated beams from the beam splitter, and means for producing a time-varying electromagnetic field in the modulator.
Claim 2
Independent Claim
149 words
An apparatus for determining the relative movement of an object, comprising a grating mechanically connected to the object and having the lines thereof aligned at right angles to the direction of movement, a source of polarized radiation for projecting polarized radiation on a first portion of the grating whereby the beam is diffracted into a plurality of subbeams, a phase-anisotropic element in the path of at least one of the subbeams, an electromagnetic field responsive birefringent optical modulator in the path of the radiation, means for directing the subbeams on to another portion of the grating whereby the subbeams are recombined, a beam splitter in the path of the recombined beam for spatially separating orthogonally polarized portions of the Recombined beam, a photoelectric detector in the path of each of the spatially separated beams from the beam splitter, and means for producing a time-varying electromagnetic field in the modulator.
Claim 3
Dependent Claim
18 words
An apparatus as claimed in claim 1, characterized in that the modulator includes at least one electro-optical crystal.
Claim 4
Dependent Claim
48 words
An apparatus as claimed in claim 2, characterized in that the modulator comprises two lambda /4-plates having aligned optic axes, between which is arranged an electro-optical crystal which has an orientation differing by 45* from that of the lambda /4-plates and to which an electric voltage is applied.
Claim 5
Dependent Claim
46 words
An apparatus as claimed in claim 2 characterized in that a sawtooth voltage is applied to the electro-optical crystal, the voltage difference between the maximum and minimum values of the sawtooth voltage corresponding to a phase-anisotropy of 360* of the plane-polarized radiation produced by the modulator.
Claim 6
Dependent Claim
41 words
An apparatus as claimed in claim 2, characterized in that the modulator comprises three electro-optical crystals, the principal direction of the middle crystal being inclined at an angle of 45* to the mutually parallel principal directions of the two other crystals.
Claim 7
Dependent Claim
41 words
An apparatus as claimed in claim 2, characterized in that the modulator comprises (2n+1) electro-optical crystals (where n is an integer), the principal direction of the even-numbered crystals being inclined at an angle of 45* to that of the odd-numbered crystals.
Claim 8
Dependent Claim
35 words
An apparatus as claimed in claim 6, characterized in that there is a phase difference of 90* between the voltage applied to the odd-numbered crystals of the modulator and that applied to the even-numbered crystals.
Claim 9
Dependent Claim
58 words
An apparatus as claimed in claim 5, characterized in that the amplitude of the voltage applied to both outer crystals corresponds to a path-length difference of substantially a quarter wavelength in the respective crystal, while the amplitude of the voltage applied to the middle crystal corresponds to a path-length difference of substantially a half wavelength in this crystal.
Claim 10
Dependent Claim
46 words
An apparatus as claimed in claim 2 characterized in that said crystal comprises several component crystals and the amplitude of the voltage applied to each component crystal is smaller than that applied to the undivided crystal by a factor proportional to the number of component crystals.
Claim 11
Dependent Claim
41 words
An apparatus as claimed in claim 2 characterized in that in the path of one of the beams diffracted by the grating there is included an n lambda /4-plate (where n is odd) which is twice traversed by the respective beam.
Claim 12
Dependent Claim
75 words
An apparatus as claimed in claim 1 characterized in that in the path of one of the beams diffracted by the grating there is arranged an n lambda /4-plate (where n is odd) and in the path of another beam diffracted by the grating there is arranged an m lambda /8 plate (where m is odd) in a manner such that the principal directions of the plates make an angle of 45* with one another.
Claim 13
Dependent Claim
50 words
An apparatus as claimed in claim 1 characterized in that in each of two beams diffracted by the grating there is arranged an n lambda /8 plate (where n is odd), the arrangement being such that the principal directions of the plates make an angle of 90* with one another.
Claim 14
Dependent Claim
64 words
An apparatus as claimed in claim 2 characterized in that the electro-optical modulator is arranged in the path of one of the beams diffracted by the grating and a second electro-optical modulator is arranged in the path of another beam diffracted by the grating, the arrangement being such that the principal directions of the two crystals make an angle of 90* with one another.
Claim 15
Dependent Claim
55 words
An apparatus as claimed in claim 13, characterized in that in the path of each of the two beams diffracted by the grating there is arranged an n lambda /16-plate (where n is odd) the prIncipal direction of which is parallel to that of the electro-optical crystal arranged in the path of the respective beam.
Claim 16
Dependent Claim
54 words
An apparatus as claimed in claim 13, characterized in that there is arranged in the path of one of the beams diffracted by the grating an n lambda /8-plate (where n is odd) the principal directions of which is parallel to that of the electro-optical crystal arranged in the path of the respective beam.
Claim 17
Dependent Claim
18 words
An apparatus as claimed in claim 1, characterized in that the modulator includes at least one magneto-optical crystal.
Claim 18
Dependent Claim
90 words
An apparatus as claimed in claim 16, characterized in that the magneto-optical modulator includes three magneto-optical crystals which are each flanked on both sides by n lambda /4 plates the principal directions of which are either the same or inclined to one another at an angle of 90*, and in that the principal directions of the n lambda /4 plates which flank the middle crystal are inclined at an angle of 45* to the principal directions of the n lambda /4-plates which flank the outer crystals (where n is odd).
Claim 19
Dependent Claim
53 words
An apparatus as claimed in claim 16, characterized in that there is produced in the crystal or crystals a magnetization which has a sawtooth shape, the difference between the maximum and minimum values of this magnetization corresponding to a rotation through 180* of the orientation of the plane of polarization of plane-polarized radiation.
Claim 20
Dependent Claim
69 words
An apparatus as claimed in claim 16, characterized in that the magneto-optical modulator comprises the series combination of two magneto-optical crystals, which series combination is enclosed by two n lambda /4-plates having the same principal directions, whilst there is interposed between the magneto-optical crystals an n lambda /4 plate the principal direction of which is inclined at an angle of 45* to the principal directions of the other plates.
Claim 21
Dependent Claim
26 words
An apparatus as claimed in claim 16, characterized in that the modulator comprises the series combination of (22+ 1) magneto-optical crystals (where n is an integer).
Claim 22
Dependent Claim
35 words
An apparatus as claimed in claim 20, characterized in that there is a phase difference of 90* between the alternating magnetization produced in the even-numbered magneto-optical crystals and that produced in the odd-numbered magneto-optical crystals.
Claim 23
Dependent Claim
56 words
An apparatus as claimed in claim 20, characterized in that the sum of the amplitudes of the magnetizations produced in the even-numbered magneto-optical crystals and the sum of the amplitudes of the magnetizations produced in the odd-numbered magneto-optical crystals cause a rotation of the plane of polarization which is equal or substantially equal to 180* .
Claim 24
Dependent Claim
39 words
An apparatus as claimed in claim 20, characterized in that there is arranged in the paths of two of the subbeams diffracted by the grating a magneto-optical modulator in which magnetizations are produced which are opposite to one another.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-12-27 | 1975-06-28 | 1975-12-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-27 | 1979-06-28 | 1979-12-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-27 | 1983-06-28 | 1983-12-28 | $7700.00 | Window Closed / Lapsed |