US4829172A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical ranging by phase shift measurement with return signal level compensation
Assignee: Nokia Bell Labs
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Filing: 1987-07-20
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Granted: 1989-05-09
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Expires: 2007-07-20
Abstract
Abstract There is disclosed an optical ranging system adapted for use with widely varying return signal levels. Automatic signal level control is achieved in two parts, a passive optical part and an active electronic AGC part. The optical part is based on the coaxial arrangement of transmitting and receiving elements in which the shielded transmitting element is mounted in front of the receiving element, which includes Fresnel lens which comprises a plastic casting. The electronic AGC portion of the system includes means for providing a voltage drive (with low internal impedance) for the final AGC transistor when it would tend to be slow, so little phase shift in the control results from changes in the signal levels. Thereby, the determination of distance (the ranging) by phase shift measurement is kept reliable as signal level changes. This optical ranging system is especially adapted for mounting on autonomously guided vehicles (robot carts), which are important for material handling and inventory control in manufacturing systems in factory environments.
Inventors
- 👤 Gabriel L. Miller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:21
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3084; G; G01; G01S; G01S17/00; G01S17/02; G01S17/06; G01S17/42; G01S7/00; G01S7/48; G01S7/481; G01S7/4811; G01S7/4812; G01S7/4817; G01S7/491; G01S7/4912; G01S7/4918; G01S17/08; G01S17/32; G01S17/36
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
146 words
An optical ranging system of the type employing means for radiating optical energy bearing continuous amplitude modulation, means for gathering a portion of the optical energy returned from an object, and means for measuring distance to the object by detecting the phase difference between the modulation of the radiated optical energy and the modulation of the returned optical energy, including means for compensating for variations in the level of the returned optical energy, said system being characterize in that the compensating means includes an optical portion based upon the partial optical blocking of the gathering means by the radiating means and an electronic portion based upon an automatic gain control arrangement in which phase shift occuring in such electronic portion varies negligibly with signal level, and the gathering means includes means for focusing the non-blocked portion of the returned optical energy arriving at the gathering means.
Claim 2
Dependent Claim
146 words
An optical ranging system of the type employing means for radiating optical energy bearing continuous amplitude modulation, means for gathering a portion of the optical energy returned from an object, and means for measuring distance to the object by detecting the phase difference between the modulation of the radiated optical energy and the modulation of the returned optical energy, including means for compensating for variations in the level of the returned optical energy, said system being characterize in that the compensating means includes an optical portion based upon the partial optical blocking of the gathering means by the radiating means and an electronic portion based upon an automatic gain control arrangement in which phase shift occuring in such electronic portion varies negligibly with signal level, and the gathering means includes means for focusing the non-blocked portion of the returned optical energy arriving at the gathering means.
Claim 3
Dependent Claim
97 words
A system according to claim 1 further characterized in that the automatic gain control arrangement includes a gain control element capable of its most rapid response at a first emitter-collector current level, but experiencing neglibible degradation if drived by a low-impedance voltage source when its emitter-collector current level is at a second level much lower than said first level, and includes a driving stage which requires a low-impedance output circuit characteristic enabling it to act as a voltage source for the gain control element when said gain control element has its emitter-collector current near the second level.
Claim 4
Dependent Claim
37 words
A system according to claim 2 further characterized in that the gain control element and the driving stage are supplied emitter-collector currents through a common node to split the current from a source of substantially constant current.
Claim 5
Dependent Claim
160 words
An optical ranging system of the type employing means for radiating optical energy bearing continuous modulation means for gathering a portion of the scattered optical energy returned form an object and means for measuring distance to the object by detecting the phase difference between the modulation of the radiated optical energy and the modulation of the returned optical energy, including means for compensating for variations in the level of the returned optical energy said system being characterized in that the raditing means is positioned in front of the gathering means and adapted to minimize propagation of optical energy from the radiating means to the gathering means other than via the object, and in addition the gathering means includes means for focusing the nonblocked portions of the returned optical energy arriving at the gathering means in such a way as to reduce the effect of the inverse square law dependence of the received scattered light-intensity upon distance of the scattering object.
Claim 6
Dependent Claim
160 words
An optical ranging system of the type employing means for radiating optical energy bearing continuous modulation means for gathering a portion of the scattered optical energy returned form an object and means for measuring distance to the object by detecting the phase difference between the modulation of the radiated optical energy and the modulation of the returned optical energy, including means for compensating for variations in the level of the returned optical energy said system being characterized in that the raditing means is positioned in front of the gathering means and adapted to minimize propagation of optical energy from the radiating means to the gathering means other than via the object, and in addition the gathering means includes means for focusing the nonblocked portions of the returned optical energy arriving at the gathering means in such a way as to reduce the effect of the inverse square law dependence of the received scattered light-intensity upon distance of the scattering object.
Claim 7
Dependent Claim
68 words
A system according to claim 3 or 4 further characterized by means for detecting the modulation of the returned optical energy, means for integrating the detected modulation, means for integrating the difference between a desired reference level for a function of the detected optical energy and the actual level of such function, and means for applying the outputs of both integrating means to an automatic gain control circuit.
Claim 8
Dependent Claim
28 words
A system according to claim 3 or 4 further characterized in that said system is mounted on an autonomously guided vehicle free to move within a manufacturing facility.
Claim 9
Dependent Claim
32 words
A system according to claim 4 further characterized in that the gathering means is a Fresnel lens having a diameter greater than that of the radiating means and being substantially coaxial therewith.
Claim 10
Dependent Claim
47 words
A system according to claim 3 further characterized in that the automatic gain control arrangement is adapted for an overall amplifier gain that is accurately linearly related to an output voltage, the system being arranged to generate this output voltage to enable its monitoring at all times.
Claim 11
Dependent Claim
53 words
A system according to claim 1 further characterized in that the optical portion of the compensating means is adapted so that the radiating means increasingly blocks the returned optical energy from the gathering means as the returned optical energy is returned as scattered light from an object increasingly close to the radiation means.
Claim 12
Dependent Claim
30 words
A system accordihg to claim 2 further characterized in that the automatic gain control arrangement includes a capacitance bridge which counteracts residual parasitic capacitance effects in the gain control element.
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) | 1992-05-08 | 1992-11-07 | 1993-05-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-05-08 | 1996-11-07 | 1997-05-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-05-08 | 2000-11-07 | 2001-05-09 | $7700.00 | Window Closed / Lapsed |