US3723748A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Digital tachometer with symmetrical output
Assignee: International Business Machines Corp
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Filing: 1971-06-23
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Granted: 1973-03-27
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Expires: 1991-06-23
Abstract
Abstract A two-phase optical tachometer whose two stationary masks and one movable mask are constructed to provide approximately a 3-to1 dark-to-light ratio. The two masks, and two associated photocells, are oriented relative to the movable mask to provide two signals which are 90* out of phase. The electrical output signal of each photocell is cyclic in nature, and each cycle thereof provides an active triangular output waveform interval, corresponding to the presence of light, which is slightly larger than one-half of the total cycle time. Each of these electrical output signals is connected to the input of an amplifier whose sensitivity threshold is adjusted to a low value, and to a value which produces a cyclic square-wave output. Each square-wave cycle of the amplifier output is symmetrical; that is, each cycle includes an active output interval, corresponding to the presence of light, which is equal to one-half of the total cycle time. The frequency of the two signals provides distance and/or velocity information. The phase relationship of the two signals provides direction information.
Inventors
- 👤 R Coburn
- 👤 O Roth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:58
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/36; G01D5/366; G01P; G01P3/00; G01P3/42; G01P3/44; G01P3/48; G01P3/481; G01P3/486
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
162 words
An incremental encoder comprising: a stationary source of radiant energy, a relatively movable element associated with said source and having a plurality of energy transparent regions separated by energy opaque regions, the physical dimensions of said regions being select to alternately block and then allow transmission of radiant energy in the ratio of approximately 3-1, a stationary detector of radiant energy associated with said relatively movable element to intercept the transmission of radiant energy thereby and to produce an electrical output signal having a pulse-shaped active portion corresponding to the presence of radiant energy and a substantially steady-state inactive portion corresponding to the absence of radiant energy, said active portion being of longer duration than said inactive portion, and signal processing means having an input connected to said detector and constructed and arranged to have a sensitivity threshold level which is above said steady-state value and is of a value such that a symmetrical output is produced by said signal processing means.
Claim 2
Dependent Claim
162 words
An incremental encoder comprising: a stationary source of radiant energy, a relatively movable element associated with said source and having a plurality of energy transparent regions separated by energy opaque regions, the physical dimensions of said regions being select to alternately block and then allow transmission of radiant energy in the ratio of approximately 3-1, a stationary detector of radiant energy associated with said relatively movable element to intercept the transmission of radiant energy thereby and to produce an electrical output signal having a pulse-shaped active portion corresponding to the presence of radiant energy and a substantially steady-state inactive portion corresponding to the absence of radiant energy, said active portion being of longer duration than said inactive portion, and signal processing means having an input connected to said detector and constructed and arranged to have a sensitivity threshold level which is above said steady-state value and is of a value such that a symmetrical output is produced by said signal processing means.
Claim 3
Dependent Claim
47 words
An incremental encoder as defined in claim 1 including a stationary mask associated with said detector, said mask having a plurality of energy transparent regions separated by energy opaque regions, said regions being in the same dimensional relationship as the like named region of said movable element.
Claim 4
Dependent Claim
13 words
An incremental encoder as defined in claim 2 wherein said ratio is 2.8-1.
Claim 5
Dependent Claim
217 words
A multiphase incremental encoder comprising: a stationary source of radiant energy, a bidirectional relatively movable element associated with said source and having a plurality of energy transparent regions of a given dimension measured in the direction of movement of said element, said energy transparent regions being separated by energy opaque regions which are of approximately three times said given dimension measured in said direction of movement, a plurality of stationary radiant energy detector means associated with said relatively movable element to intercept the transmission of radiant energy thereby and to produce a plurality of electrical output signals as a result thereof, each of said output signals having a pulse-shaped active portion corresponding to the presence of radiant energy and a substantially Steady-state inactive portion corresponding to the absence of radiant energy, said active portion being of longer duration than said inactive portion, and said detector means being spaced from each other in said direction of movement to produce phase-displaced signals therefrom, and a plurality of signal processing means, each having an input connected to one of said detector means and each being constructed and arranged to have a selected sensitivity threshold level which is above said steady-state value and is of a value such that a symmetrical output is produced by each of said signal processing means.
Claim 6
Dependent Claim
217 words
A multiphase incremental encoder comprising: a stationary source of radiant energy, a bidirectional relatively movable element associated with said source and having a plurality of energy transparent regions of a given dimension measured in the direction of movement of said element, said energy transparent regions being separated by energy opaque regions which are of approximately three times said given dimension measured in said direction of movement, a plurality of stationary radiant energy detector means associated with said relatively movable element to intercept the transmission of radiant energy thereby and to produce a plurality of electrical output signals as a result thereof, each of said output signals having a pulse-shaped active portion corresponding to the presence of radiant energy and a substantially Steady-state inactive portion corresponding to the absence of radiant energy, said active portion being of longer duration than said inactive portion, and said detector means being spaced from each other in said direction of movement to produce phase-displaced signals therefrom, and a plurality of signal processing means, each having an input connected to one of said detector means and each being constructed and arranged to have a selected sensitivity threshold level which is above said steady-state value and is of a value such that a symmetrical output is produced by each of said signal processing means.
Claim 7
Dependent Claim
62 words
A multiphase incremental encoder as defined in claim 4 wherein each of said detector means includes a stationary mask having energy transparent regions and energy opaque regions in the same spacial relationship as the like named region of said movable element, said masks being spaced from each other in said direction of movement and being in alignment with its associated detector means.
Claim 8
Dependent Claim
37 words
A multiphase incremental encoder as defined in claim 5 including means responsive to the output of said plurality of signal processing means and effective to provide an output indicating the direction of movement of said movable element.
Claim 9
Dependent Claim
45 words
A multiphase incremental encoder as defined in claim 6 including means responsive to the output of at least one of said plurality of signal processing means and effective to provide an output which varies as a function of the distance through which said element moves.
Claim 10
Dependent Claim
59 words
A multiphase incremental encoder as defined in claim 5 wherein said source of radiant energy provides energy in the visible spectrum, wherein said element is a low inertia rotary disc, wherein said detectors are photoelectric cells responsive to the visible spectrum, and wherein said signal processing means are amplifiers having adjustment means effective to adjust the sensitivity threshold thereof.
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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 |