US3644739A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for detecting positional errors utilizing high-frequency modulation of light source and phasesensitive detector
Assignee: EMI Ltd
•
Filing: 1969-11-28
•
Granted: 1972-02-22
•
Expires: 1989-11-28
Abstract
Abstract Apparatus is disclosed for detecting error in the positioning of a member to which the apparatus is attached in relation to a reference surface having a different reflectivity from the surrounding area. An extended light source modulated at a frequency high relative to mains frequency is adapted to produce dispersive illumination for floodlighting the reference surface and at least two photoelectrically sensitive devices are arranged for viewing substantially only light reflected from respective discrete areas on the reference surface spaced in one direction and for producing in cooperation with the reference surface output electrical signals representative of the illumination received by the devices. Means are provided for deriving a position error signal depending on the differences between the output signals.
Inventors
- 👤 Alan Wilkinson
- 👤 Stewart Charles Hine
- 👤 David Robert Bosher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 02:28
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; B; B66; B66B; B66B1/00; B66B1/34; B66B1/36; B66B1/40
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
157 words
Apparatus for detecting error in the positioning of a member to which the apparatus is attached in relation to a reference surface having a different reflectivity from the surrounding area, comprising: a. an extended light source adapted for producing dispersed illumination of said reference surface, b. at least two photoelectrically sensitive devices adapted for viewing substantially only normally reflected light from respective discrete areas spaced in one direction and for producing in cooperation with the reference surface output electrical signals representative of the illumination received by said devices, c. means for modulating the light from said source at a frequency which is high relative to mains frequency, and d. phase-sensitive detecting means responsive to said output electrical signals and adapted to derive a position error signal having a magnitude dependent on the amplItude of the difference between components of said output signals corresponding to the modulation, and having a polarity dependent on the phase of said difference.
Claim 2
Dependent Claim
157 words
Apparatus for detecting error in the positioning of a member to which the apparatus is attached in relation to a reference surface having a different reflectivity from the surrounding area, comprising: a. an extended light source adapted for producing dispersed illumination of said reference surface, b. at least two photoelectrically sensitive devices adapted for viewing substantially only normally reflected light from respective discrete areas spaced in one direction and for producing in cooperation with the reference surface output electrical signals representative of the illumination received by said devices, c. means for modulating the light from said source at a frequency which is high relative to mains frequency, and d. phase-sensitive detecting means responsive to said output electrical signals and adapted to derive a position error signal having a magnitude dependent on the amplItude of the difference between components of said output signals corresponding to the modulation, and having a polarity dependent on the phase of said difference.
Claim 3
Dependent Claim
15 words
Apparatus according to claim 1 in which said light source comprises one elongated fluorescent lamp.
Claim 4
Dependent Claim
115 words
Apparatus according to claim 1 including: a. two further photoelectrically sensitive devices adapted for viewing substantially only normally reflected light from respective discrete areas on the reference surface spaced in a second direction perpendicular to the first and for producing in cooperation with the reference surface further output electrical signals representative of the illumination received by said further devices, and wherein b. said phase-sensitive detecting means is also responsive to said further output electrical signals and is adapted for deriving a further position error signal having a magnitude dependent on the difference between components of said further output signals corresponding to the modulation, and having a polarity dependent on the phase of the last-mentioned difference.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-02-21 | 1975-08-23 | 1976-02-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-02-21 | 1979-08-23 | 1980-02-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-02-21 | 1983-08-23 | 1984-02-22 | $7700.00 | Window Closed / Lapsed |