US3812352A
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Encoder readout system
Assignee: Northrop Grumman Guidance and Electronics Co Inc
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Filing: 1972-08-28
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Granted: 1974-05-21
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Expires: 1992-08-28
Abstract
Abstract A system for reading out positional information from a linear or rotary encoder based on an extension of the pinhole imaging theory to include the effects of diffraction in the encoder. In a typical encoder, light from a radiation source is directed first through a code plate having thereon periodic markings of alternating transparent and opaque increments, then through a slit plate also having thereon periodic markings of alternating transparent and opaque increments, and then upon a detector. According to the teachings of this invention there are optimal positions for the encoder plate, the slit plate and the detector to obtain maximum readout signals from the encoder. These optimal positions are selected in theory according to two relationships which must be simultaneously satisfied, namely: Z1 nS1S2/ lambda , and Z1 (S1 - S2)Z2/ S2 where n is an integer of one or greater, lambda is the mean wavelength of the light source, S1 is the length of one clear increment-opaque increment period in the code plate, S2 is the length of one clear increment-opaque increment period in the slit plate, Z1 is the distance between the code plate periodic markings and the slit plate periodic markings, and Z2 is the distance between the detector and the periodic markings on the slit plate.
Inventors
- 👤 A Macgovern
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 23:02
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/36; G01D5/38
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
274 words
In an encoder which measures the movement of a first plate, having thereon periodic markings of alternating transparent and opaque increments, relative to a second plate, having thereon periodic markings of alternating increments, the improvement comprising the encoder and the readout system in the encoder being optimally designed while taking into account diffraction effects of radiation in the encoder and comprising: a. a first plate having thereon periodic markings of alternating transparent and opaque increments, with the length of one clear increment-opaque increment period being S1; b. a second plate having thereon periodic markings of alternating increments, with the length of one alternating increment period being S2; c. a radiation source means for producing radiation having a mean wavelength lambda and for directing it first through said first plate and then onto said second plate, with relative movement between said first plate and said second plate causing modulation of the radiation; d. a detector means for detecting modulation of the radiation by said first and second plates; and e. means for detecting and reading relative movement between said first plate and said second plate while taking into account diffraction effects, and including means for positioning said first plate and said second plate and said detector means substantially according to the following two relationships: Z1 nS1S21 lambda , and Z1 (S1 - S2)Z2/S2 wherein S1, S2, and lambda have already been defined, and wherein Z1 equals the distance between the first plate periodic markings and the second plate periodic markings, Z2 equals the distance between said detector means and the periodic markings on said second plate, and n equals an integer of one or greater.
Claim 2
Dependent Claim
274 words
In an encoder which measures the movement of a first plate, having thereon periodic markings of alternating transparent and opaque increments, relative to a second plate, having thereon periodic markings of alternating increments, the improvement comprising the encoder and the readout system in the encoder being optimally designed while taking into account diffraction effects of radiation in the encoder and comprising: a. a first plate having thereon periodic markings of alternating transparent and opaque increments, with the length of one clear increment-opaque increment period being S1; b. a second plate having thereon periodic markings of alternating increments, with the length of one alternating increment period being S2; c. a radiation source means for producing radiation having a mean wavelength lambda and for directing it first through said first plate and then onto said second plate, with relative movement between said first plate and said second plate causing modulation of the radiation; d. a detector means for detecting modulation of the radiation by said first and second plates; and e. means for detecting and reading relative movement between said first plate and said second plate while taking into account diffraction effects, and including means for positioning said first plate and said second plate and said detector means substantially according to the following two relationships: Z1 nS1S21 lambda , and Z1 (S1 - S2)Z2/S2 wherein S1, S2, and lambda have already been defined, and wherein Z1 equals the distance between the first plate periodic markings and the second plate periodic markings, Z2 equals the distance between said detector means and the periodic markings on said second plate, and n equals an integer of one or greater.
Claim 3
Dependent Claim
21 words
An encoder as set forth in claim 1 wherein said second plate has periodic markings of alternating transparent and opaque increments.
Claim 4
Dependent Claim
12 words
A system as set forth in claim 1 wherein n equals one.
Claim 5
Dependent Claim
12 words
An encoder as set forth in claim 1 wherein n equals two.
Claim 6
Dependent Claim
15 words
An encoder as set forth in claim 1 wherein the encoder is a linear encoder.
Claim 7
Dependent Claim
15 words
An encoder as set forth in claim 1 wherein the encoder is a rotary encoder.
Claim 8
Dependent Claim
26 words
An encoder as set forth in claim 1 wherein said first plate is the encoder code plate and said second plate is the encoder slit plate.
Claim 9
Dependent Claim
15 words
An encoder as set forth in claim 2 wherein the encoder is a linear encoder.
Claim 10
Dependent Claim
26 words
An encoder as set forth in claim 8 wherein said first plate is the encoder code plate and said second plate is the encoder slit plate.
Claim 11
Dependent Claim
15 words
An encoder as set forth in claim 2 wherein the encoder is a rotary encoder.
Claim 12
Dependent Claim
26 words
An encoder as set forth in claim 10 wherein said first plate is the encoder code plate and said second plate is the encoder slit plate.
Claim 13
Dependent Claim
21 words
An encoder as set forth in claim 1 wherein said second plate has periodic markings of alternating reflective and absorptive increments.
Claim 14
Dependent Claim
15 words
An encoder as set forth in claim 12 wherein the encoder is a linear encoder.
Claim 15
Dependent Claim
26 words
An encoder as set forth in claim 13 wherein said first plate is the encoder code plate and said second plate is the encoder slit plate.
Claim 16
Dependent Claim
15 words
An encoder as set forth in claim 12 wherein the encoder is a rotary encoder.
Claim 17
Dependent Claim
26 words
An encoder as set forth in claim 15 wherein said first plate is the encoder code plate and said second plate is the encoder slit plate.
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) | 1977-05-20 | 1977-11-19 | 1978-05-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-20 | 1981-11-19 | 1982-05-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-20 | 1985-11-19 | 1986-05-21 | $7700.00 | Window Closed / Lapsed |