US3723744A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical tracker with variable density spatial filter
Assignee: AT&T Inc
•
Filing: 1970-12-21
•
Granted: 1973-03-27
•
Expires: 1990-12-21
Abstract
Abstract An optical filter whose transmission coefficient increases monotonically with distance from the center of the filter is placed in front of the Image Position Sensor of an optical tracker. The optical tracker is of the type using a single photocell and a single chopper for both azimuthal and elevational channels. The center of the filter lies substantially on the optical axis of the system. Accordingly, the beam returning from a target being tracked by the optical tracker is attenuated according to its displacement from the axis of the system. The effect of this variable attenuation is to reduce the crosscoupling between azimuthal and elevational channels and to linearize the dependence of the error signals upon the respective components of target image displacement.
Inventors
- 👤 Y Lim
- 👤 M Subramanian
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 09:03
CPC Classifications
G; G01; G01S; G01S3/00; G01S3/78; G01S3/782; G01S3/787; G01S17/00; G01S17/66
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
163 words
In apparatus for receiving a light beam and providing output signals indicative of the displacement of said light beam along first and second coordinate axes which apparatus comprises light chopping means interposed in the path of said light beam for periodically interrupting the passage of said light beam according to its displacement, photodetector means positioned to intercept said light beam after said light beam has passed through said chopping means, said photodetector means providing an electrical signal proportional to the instantaneous intensity of said lIght beam, and demodulation means for receiving said electrical signal from said photodetector means and for providing first and second error signals indicative of the corresponding displacements of said light beam along said first and second coordinate axes, the improvement comprising a variable density spatial filter positioned in the path of said light beam for attenuating said light beam according to its displacement, so that said first and second error signals are substantially linearly proportional to the corresponding displacements.
Claim 2
Dependent Claim
163 words
In apparatus for receiving a light beam and providing output signals indicative of the displacement of said light beam along first and second coordinate axes which apparatus comprises light chopping means interposed in the path of said light beam for periodically interrupting the passage of said light beam according to its displacement, photodetector means positioned to intercept said light beam after said light beam has passed through said chopping means, said photodetector means providing an electrical signal proportional to the instantaneous intensity of said lIght beam, and demodulation means for receiving said electrical signal from said photodetector means and for providing first and second error signals indicative of the corresponding displacements of said light beam along said first and second coordinate axes, the improvement comprising a variable density spatial filter positioned in the path of said light beam for attenuating said light beam according to its displacement, so that said first and second error signals are substantially linearly proportional to the corresponding displacements.
Claim 3
Dependent Claim
29 words
The apparatus of claim 1 wherein said light chopping means comprises a disk diametrically divided into reflective and nonreflective areas and a motor rotating said disk about its axis.
Claim 4
Dependent Claim
109 words
The apparatus of claim 2 wherein said demodulation means comprises: means for generating first and second phase reference signals, the phase of said first phase reference signal having a fixed relationship to the angle of rotation of said disk and said second phase reference signal being 90 * out of phase with said first phase reference signal, and first and second phase demodulators each receiving said electrical signal from said photodetector means, said first phase demodulator also receiving said first phase reference signal and said second phase demodulator also receiving said second phase reference signal, said first and second phase demodulators providing said first and second error signals, respectively.
Claim 5
Dependent Claim
143 words
In an image position sensor comprising optical means for focusing the image of a target toe tracked in a focal plane, a photodetector, and a rotary chopper positioned in said focal plane to periodically modulate the intensity of said image according to the position of said image in said focal plane, said chopper and said photodetector combining to produce an output signal indicating the position of said image in said focal plane, the improvement comprising: a variable density spatial filter positioned between said optical means and said focal plane for attenuating the intensity of said image according to its position in said focal plane, said filter having a transmission coefficient increasing monotonically with distance from its center so that the output of said photodetector includes components which vary in linear proportion to the displacement of said image from the center of said filter.
Claim 6
Dependent Claim
143 words
In an image position sensor comprising optical means for focusing the image of a target toe tracked in a focal plane, a photodetector, and a rotary chopper positioned in said focal plane to periodically modulate the intensity of said image according to the position of said image in said focal plane, said chopper and said photodetector combining to produce an output signal indicating the position of said image in said focal plane, the improvement comprising: a variable density spatial filter positioned between said optical means and said focal plane for attenuating the intensity of said image according to its position in said focal plane, said filter having a transmission coefficient increasing monotonically with distance from its center so that the output of said photodetector includes components which vary in linear proportion to the displacement of said image from the center of said filter.
Claim 7
Dependent Claim
41 words
An image position sensor as recited in claim 4 further comprising demodulation means for receiving said output of said photodetector and extracting said components which vary in linear proportion to the displacement of said image from the center of said filter.
Claim 8
Dependent Claim
141 words
In apparatus for generating first and second signals which are substantially linearly proportional to the displacement of an object along corresponding first and second coordinate axes which apparatus comprises means for generating a light beam, the position of which is indicative of the position of said object, means for focusing said light beam onto an image plane, and first means responsive to the position of said light beam on said image plane, said first means providing output signals which are nonlinearly proportional to the displacement of said light beam in said image plane along said first and second coordinate axes, the improvement comprising an optical filter interposed between said means for focusing and said first means, said filter comprising a substantially planar optical medium whose transmissivity is a monotonically increasing function of the distance from the center of said optical medium.
Claim 9
Dependent Claim
141 words
In apparatus for generating first and second signals which are substantially linearly proportional to the displacement of an object along corresponding first and second coordinate axes which apparatus comprises means for generating a light beam, the position of which is indicative of the position of said object, means for focusing said light beam onto an image plane, and first means responsive to the position of said light beam on said image plane, said first means providing output signals which are nonlinearly proportional to the displacement of said light beam in said image plane along said first and second coordinate axes, the improvement comprising an optical filter interposed between said means for focusing and said first means, said filter comprising a substantially planar optical medium whose transmissivity is a monotonically increasing function of the distance from the center of said optical medium.
Claim 10
Dependent Claim
129 words
The apparatus of claim 6 wherein said optical medium comprises a medium whose transmissivity varies as a function of spatial coordinates x0 and yo in the plane of said optical medium, said xo and yo being rectangular coordinates with an origin at said center of said optical medium, so that the transmissivity is proportional to yo/(E(xo; yo))+xo/(E(yo; xo)) where f( theta ) 1/ pi ( theta 1 - 1/2 sin 2 theta ), theta 1 0 if D > 1 theta 1 cos 1D, O < theta 1 < pi , if D < or = 1 theta 1 pi , if D < -1, D( theta ) Rho o sin ( theta o -theta ), Rho 0 Square Root xo2 + yo2, and theta o tan 1 (yo/xo).
References Cited (Backward Citations)
US2958783A
Cited
US3413478A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-26 | 1976-09-25 | 1977-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-26 | 1980-09-25 | 1981-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-26 | 1984-09-25 | 1985-03-27 | $7700.00 | Window Closed / Lapsed |