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US3904295A
Expired / Lapsed
US
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Method and apparatus for the no-contact measurement of velocities, changes in relative position, or displacement paths
Assignee: Ernst Leitz Wetzlar GmbH
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Filing: 1973-07-30
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Granted: 1975-09-09
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Expires: 1993-07-30
Abstract
Abstract Light diffracting or dispersing properties of an object dividing a wave front in angular differently oriented wave fronts are used for no-contact optical velocity-, acceleration-, change in relative position- or displacement path measurements of said object movable relative to a measuring head. No systematic markings affecting light phase or amplitude on the measuring surface are disposed in the depth of field of imaging system. Measurements are made respectively to one coordinate associated to one of the six possible spatial degrees of freedom of motion. The object under test and an optical component yielding sharply defined angular relationship among different but combined wave fronts are conjugatedly disposed in the imaging system. Light modulations produced upon changing the relative position are photoelectrically converted into signals exhibiting a frequency change proportional to linear or angular velocity variation. The measurement is improved by using components having negligible light absorption, and determining angular relationship among the wave fronts. Light fluxes from interaction among partial wave fronts containing information concerning the object movement, derived from solid angle areas of equal modulation phase are converted separately into photoelectrical signals having sinusoidally varying modulation characteristics with the respective measuring coordinate. The modulation period cycles are half as long as the statistical spatial frequency components of the object under test. The light energy proportions are split off from and outside the solid angle area of the illumination aperture. The electric signals produced are evaluated as direct or carrier-frequency signals with respect to the measured qualities desired.
Inventors
- 👤 Fromund Hock
- 👤 Knut Heitmann
- 👤 Dietmar Kaul
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 07:14
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/36; G01D5/38; G01P; G01P3/00; G01P3/36
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
177 words
A method of measuring a property of movement of a light-dispersing object in at least one coordinate direction, comprising the steps of: a. selecting from the light modulated at said object at least two differently oriented beams and utilizing said beams for forming an optical image of said object; b. determining the solid angles of said beams; c. suppressing light unmodulated or respectively dispersed into very large angles at said object; d. causing at least one optical component having negligible light absorption and the property of determining the angular relAtionships among at least three optical wave fronts, to further modulate light fluxes derived from solid angle areas of said imaging beams having equal modulation phase; e. utilizing each respective one of said further modulated fluxes to generate electrical signals having signal periods each equal to one-half of a signal period determined by parameters of said light dispersing object and having modulation characteristics that vary sinusoidally with respect to the associated coordinate direction; and f. evaluating said signals to produce output signals indicative of the property of movement.
Claim 2
Independent Claim
177 words
A method of measuring a property of movement of a light-dispersing object in at least one coordinate direction, comprising the steps of: a. selecting from the light modulated at said object at least two differently oriented beams and utilizing said beams for forming an optical image of said object; b. determining the solid angles of said beams; c. suppressing light unmodulated or respectively dispersed into very large angles at said object; d. causing at least one optical component having negligible light absorption and the property of determining the angular relAtionships among at least three optical wave fronts, to further modulate light fluxes derived from solid angle areas of said imaging beams having equal modulation phase; e. utilizing each respective one of said further modulated fluxes to generate electrical signals having signal periods each equal to one-half of a signal period determined by parameters of said light dispersing object and having modulation characteristics that vary sinusoidally with respect to the associated coordinate direction; and f. evaluating said signals to produce output signals indicative of the property of movement.
Claim 3
Dependent Claim
22 words
A method as claimed in claim 1, wherein the optical component is situated in the image plane set up by said beams.
Claim 4
Dependent Claim
47 words
A method as claimed in claim 2, wherein said fluxes being derived from solid angle areas of said imaging beams having equal modulation phase, are determined by the properties of said optical component and by the angular position of individual light fluxes incident on said optical component.
Claim 5
Dependent Claim
54 words
A method as claimed in claim 1, wherein said evaluating step includes the steps of selecting and combining said electrical signals for further producing signals having push-pull components, and feeding said further signals to input means of a push-pull amplifying means thereby to suppress mutually similar proportions in respective signals in said further signals.
Claim 6
Dependent Claim
26 words
A method as claimed in claim 4, wherein at least two electrical signals are produced to have periodic modulation characteristics associated with a given coordinate direction.
Claim 7
Dependent Claim
45 words
A method as claimed in claim 1, comprising the step of splitting said imaging beams into at least two components, each of which is employed in the production of at least two signals, which have relative phase displacements different from n, where n is integer.
Claim 8
Dependent Claim
19 words
A method as claimed in claim 6, wherein said signals are indicative of the direction of the relative movement.
Claim 9
Dependent Claim
39 words
A method as claimed in claim 6, wherein said splitting step takes place in geometric beam splitting means, light proportions from at least two surface elements of said light dispersing object being separately fed to a photoelectric receiving means.
Claim 10
Dependent Claim
42 words
A method as claim in claim 6, wherein said splitting step takes place in physical beam splitting means and individual mutually distinguishable light proportions from the whole surface of said light dispersing object being imaged are separately fed to photoelectric receiving means.
Claim 11
Dependent Claim
81 words
A method as claimed in claim 1, producing at least two carrier frequency signals, which provide beat frequencies or modulation phases indicative of the direction of the relative movement, one of the carrier frequency signals being associated with a given coordinate direction and being derived from light proportions which have passed through the optical component, the other one of the carrier frequency signals being derived from light proportion in the light path ot the optical components or from electrical modulation signals.
Claim 12
Dependent Claim
156 words
Apparatus for measuring a property of movement of a light dispersing object in at least one coordinate direction comprising: a. a light source, which is arranged to illuminate said object; b. means selecting at least two differently oriented beams from light modulated at said object, determining the solid angles of said beams and suppressing light unmodulated or respectively dispersed into very large angles at said object; c. optical imaging means to form an optical image of said object; d. at least one optical component, having negligible light absorption and the property of determining the angular relationships among at least three optical wave fronts, to further modulate light fluxes from said angle areas of said imaging beams having equal modulation phase; e. photoelectric receiving means producing an individual electrical signal from each respective one of said further modulated fluxes; and f. evaluating means to produce from said sigNals an output signal indicative of the property of movement.
Claim 13
Dependent Claim
156 words
Apparatus for measuring a property of movement of a light dispersing object in at least one coordinate direction comprising: a. a light source, which is arranged to illuminate said object; b. means selecting at least two differently oriented beams from light modulated at said object, determining the solid angles of said beams and suppressing light unmodulated or respectively dispersed into very large angles at said object; c. optical imaging means to form an optical image of said object; d. at least one optical component, having negligible light absorption and the property of determining the angular relationships among at least three optical wave fronts, to further modulate light fluxes from said angle areas of said imaging beams having equal modulation phase; e. photoelectric receiving means producing an individual electrical signal from each respective one of said further modulated fluxes; and f. evaluating means to produce from said sigNals an output signal indicative of the property of movement.
Claim 14
Dependent Claim
16 words
Apparatus as claimed in claim 11, wherein said light source illuminates the object with coherent light.
Claim 15
Dependent Claim
29 words
Apparatus as claimed in claim 11, wherein said optical component comprises a phase grating arranged to suppress light of the range of wavelengths and unmodulated light at the object.
Claim 16
Dependent Claim
55 words
Apparatus as claimed in claim 11, wherein said optical component comprises a bi-refringent component selected from a set of prisms, a set of lenses and a dielectric layer assembly, wherein the bi-refringement component is situated in a plane to be located in a position conjugate to the object with respect to the optical imaging means.
Claim 17
Dependent Claim
38 words
Apparatus as claimed in claim 11, comprising a semi-reflector within said optical component having a part thereof situated in a plane to be located in a position conjugated to the object with respect to the optical imaging means.
Claim 18
Dependent Claim
24 words
Apparatus as claimed in claim 15, wherein the semi-reflector is constructed to act independently of the state of polarisation of the light incident thereon.
Claim 19
Dependent Claim
53 words
Apparatus as claimed in claim 15, wherein said semi-reflector is a non-polarizing mirror having planar surfaces in parallel to each other and representing the bisector of an angle set up between at least two partial beams of said imagining light being incident on respectively opposite sides of said planar surfaces of said mirror.
Claim 20
Dependent Claim
48 words
Apparatus as claimed in claim 11, comprising an aperture stop provided with at least two apertures to define at least two light bundles in the imaging light, which have relative angular positions of the principal rays corresponding to the preferred relative angular positions defined by the optical component.
Claim 21
Dependent Claim
36 words
Apparatus as claimed in claim 18, wherein said aperture stop comprises portions so selected from optically absorbing and deflecting portions that unmodulated light from the object is prevented by said aperture stop from reaching the image.
Claim 22
Dependent Claim
28 words
Apparatus as claimed in claim 18, wherein the apertures define individual solid angle areas for the respective light bundles, the solid angle areas being of mutually equal size.
Claim 23
Dependent Claim
77 words
Apparatus as claimed in claim 11, wherein said optical component comprises beam splitting means of geometrical or physical property for splitting the imaging light into at least two proportions, wherein said component comprises at least two joint surface structures displaced relative to one another as to define periodic phase modulation characteristics, and wherein geometrically separate optical means being associated with the respective surface structures to guide light from the individual surface structures to respective photo-electric receiving means.
Claim 24
Dependent Claim
108 words
Apparatus as claimed in claim 21, wherein said optical component comprises a phase grating being provided in the light path from an aperture stop to the plane of the image to define a plane parallel to the plane of the image, and being arranged to split the image into at least two co-planar partial images and so to split images, formed behind said image plane, of the aperture stop that with each of the co-planar partial images, when disposed to be conjugated to the object with respect to the imaging means there are associated by correspondingly positioned light flux portions at least two images of the aperture stop.
Claim 25
Dependent Claim
106 words
Apparatus as claimed in claim 22, wherein said physical beam splitting means and optical means are Wollaston prisms disposed in the paths of respective light bundles to the optical component, the paths being defined by an aperture stop, the optical means being arranged to introduce different path differences or phase displacements between light components of mutually orthogonal polarisation direction or of different frequency in the light bundles, wherein said beam splitting means are arranged to split the light from the optical component into light proportions of different polarisation direction or of different frequency respectiVely and to direct the light proportions to respectively associated photo-electric receiving means.
Claim 26
Dependent Claim
20 words
Apparatus as claimed in claim 23, wherein the magnitude of the phase displacements between the light component is pi /2.
Claim 27
Dependent Claim
108 words
Apparatus as claimed in claim 21, wherein said optical component comprises a Wollaston prism being provided in the light path from an aperture stop to the plane of the image to define a plane parallel to the plane of the image and being arranged to split the image into at least two coplanar partial images and so to split images formed behind said image plane of the aperture stop that with each of the coplanar partial images, when disposed to be conjugated to the object with respect to the imaging means there are associated by corresponding positioned light flux proportions at least two images of the aperture stop.
Claim 28
Dependent Claim
66 words
Appparatus as claimed in claim 21, wherein said physical beam splitting means and optical means are Savart plates disposed in the paths of respective light bundles to the optical component, the paths being defined by an aperture stop, the optical means being arranged to introduce different path differences or phase displacements between light components of mutually orthogonoal polarization directions or of different frequency in the light.
Claim 29
Dependent Claim
66 words
Apparatus as claimed in claim 21, wherein said physical beam splitting meand and optical means are mica plates disposed in the paths of respective light bundles to the optical component, the paths being defined by an aperture stop, the optical means being arranged to introduce different path differences or phase displacements between light components of mutually orthogonoal polarization directions or of different frequency in the light.
Claim 30
Dependent Claim
69 words
Apparatus as claimed in claim 21, wherein said physical beam splitting means and optical means are totally reflecting phase displacing means disposed in the paths of respective light bundles to the optical component, the paths being defined by an aperture stop, the optical means being arranged to introduce different path differences or phase displacements between light components of mutually orthogonal polarization directions or of different frequency in the light.
Claim 31
Dependent Claim
66 words
Apparatus as claimed in claim 21, wherein said physical beam splitting means and optical means are dispersion prisms disposed in the paths of respective light bundles to the optical component, the paths being defined by an aperture stop, the optical means being arranged to introduce different path differences or phase displacements between light components of mutually orthogonal polarization directions or of different frequency in the light.
Claim 32
Dependent Claim
66 words
Apparatus as claimed in claim 21, wherein said physical beam splitting means and optical means are dispersing plates disposed in the paths of respective light bundles to the optical component, the paths being defined by an aperture stop, the optical means being arranged to introduce different path differences or phase displacements between light components of mutually orthogonal polarization directions or of different frequency in the light.
Claim 33
Dependent Claim
27 words
Apparatus as claimed in claim 11, wherein the optical component comprises an electro-acoustic light modulator, which comprises two acoustic generators to excite an optical medium situated therebetween.
Claim 34
Dependent Claim
21 words
Apparatus as claimed in claim 31, wherein the two individual acoustic generators are constructed to produce waves of respectively different frequency.
Claim 35
Dependent Claim
39 words
Apparatus as claimed in claim 11, wherein the apparatus described is used as an incremental measuring device that forms electrical signals by the relative movement between a fixed point and at least one grating, for example a phase grating.
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) | 1978-09-08 | 1979-03-10 | 1979-09-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-08 | 1983-03-10 | 1983-09-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-08 | 1987-03-10 | 1987-09-09 | $7700.00 | Window Closed / Lapsed |