Patent US3697183A successfully refreshed from Google Patents.
US3697183A
Expired / Lapsed
US
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Optical apparatus using slitted masks for detecting rotary motion of object
Assignee: Quantic Industries Inc
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Filing: 1968-06-14
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Granted: 1972-10-10
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Expires: 1988-06-14
Abstract
Abstract A digital angle readout subsystem for an infrared horizon tracker provides a position reference for the tracker and a readout counter for indicating the angular displacement of the tracker from the reference position. The tracker is coupled to a movable mirror, which moves in synchronism with the tracker. The mirror reflects light projected through a primary mask and causes the light to strike a secondary mask at a location which varies with movement of the mirror. Photodetectors behind the secondary mask are responsive to the moving light patterns to provide electrical signal indications of the reference position and angular displacement of the mirror. The counting portion of the primary mask has evenly spaced slits and bars, the secondary counting mask includes left and right sections for splitting the field of movement of the tracker into two parts. Each section has four individual subsections shifted 90* in phase from an adjacent subsection. Switching between left and right counting sections is provided by switching pulses produced by primary and secondary reference masks. The reference masks have a pattern based on a vk lambda mathematical difference set and provide a reference position signal for the tracker.
Inventors
- 👤 Sheldon Knight
- 👤 Kerwin Peter Mccarron
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 13:26
CPC Classifications
G; G01; G01S; G01S3/00; G01S3/78; G01S3/782; G01S3/783; G01S3/7835; H; H03; H03M; H03M1/00; H03M1/12; H03M1/22; H03M1/24; H03M1/28; H03M1/30
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
270 words
Optical apparatus for detecting motion of a rotatable object having a reference reflecting surface which includes: slitted primary and secondary counting masks and means for projecting light through said primary mask through a lens toward such surface to be reflected therefrom to strike said secondary mask at a location thereon which varies with movement of said rotatable object, the invention comprising said secondary counting mask with slits therein equal in number per unit length to said primary mask slits, all of said slits being directed parallel to the axis of rotation of said object, said rotatable object having a predetermined field of movement, said secondary mask having a first cluster of four mutually adjacent slitted sections intercepting reflected light substantially only when said object is in one half of said field, said sections being spaced so that the slits of bordering sections have a 90* phase difference, light sensitive means behind each of said sections for providing an electrical signal indicative of the rotation of said object in said one half of said field, said secondary counting mask including a second cluster of four mutually adjacent slitted sections spaced similarly to said first cluster and intercepting reflected light substantially only when the object is in the other half of said field, light sensitive means behind each of the sections of said second cluster for providing an electrical signal indicative of the rotation of said object in said other half of said field and switching means responsive to the fIeld half in which said object is located to selectively receive data from the light sensitive means associated with that field half.
Claim 2
Dependent Claim
270 words
Optical apparatus for detecting motion of a rotatable object having a reference reflecting surface which includes: slitted primary and secondary counting masks and means for projecting light through said primary mask through a lens toward such surface to be reflected therefrom to strike said secondary mask at a location thereon which varies with movement of said rotatable object, the invention comprising said secondary counting mask with slits therein equal in number per unit length to said primary mask slits, all of said slits being directed parallel to the axis of rotation of said object, said rotatable object having a predetermined field of movement, said secondary mask having a first cluster of four mutually adjacent slitted sections intercepting reflected light substantially only when said object is in one half of said field, said sections being spaced so that the slits of bordering sections have a 90* phase difference, light sensitive means behind each of said sections for providing an electrical signal indicative of the rotation of said object in said one half of said field, said secondary counting mask including a second cluster of four mutually adjacent slitted sections spaced similarly to said first cluster and intercepting reflected light substantially only when the object is in the other half of said field, light sensitive means behind each of the sections of said second cluster for providing an electrical signal indicative of the rotation of said object in said other half of said field and switching means responsive to the fIeld half in which said object is located to selectively receive data from the light sensitive means associated with that field half.
Claim 3
Dependent Claim
39 words
Optical apparatus as in claim 1 together with reference mask means for actuating said switching means said reference mask means including primary and secondary masks having a bar and slit pattern determined by a predetermined mathematical constant difference set.
Claim 4
Dependent Claim
229 words
Optical apparatus for determining the angular displacement of a movable object from a reference position which includes primary and secondary reference masks having transparent slits and opaque bars means for projecting light through said slits of said primary mask to strike said secondary mask at a location thereon which varies with movement of said movable object, light sensitive means behind said secondary mask for detecting said reference position of said movable object which will cause the slit pattern of the primary mask to strike the secondary mask exactly on the bar pattern of the secondary mask, the invention comprising secondary and primary reference masks having predetermined bar and slit patterns, the pattern of said secondary mask being the reverse of the pattern of said primary mask, said patterns being based on a mathematical constant difference set of the vk lambda type where v is the modulus of the set which is the number of units in the set which determines the total number of slits and bars, k is the number of members in the set which determines the number of bars in the pattern and lambda is in mathematical terms the number of ways the differences form in the set and the ratio ( lambda + 1)/(v) determines the light transmittance of said first and second masks for positions of said movable object other than said reference position.
Claim 5
Dependent Claim
229 words
Optical apparatus for determining the angular displacement of a movable object from a reference position which includes primary and secondary reference masks having transparent slits and opaque bars means for projecting light through said slits of said primary mask to strike said secondary mask at a location thereon which varies with movement of said movable object, light sensitive means behind said secondary mask for detecting said reference position of said movable object which will cause the slit pattern of the primary mask to strike the secondary mask exactly on the bar pattern of the secondary mask, the invention comprising secondary and primary reference masks having predetermined bar and slit patterns, the pattern of said secondary mask being the reverse of the pattern of said primary mask, said patterns being based on a mathematical constant difference set of the vk lambda type where v is the modulus of the set which is the number of units in the set which determines the total number of slits and bars, k is the number of members in the set which determines the number of bars in the pattern and lambda is in mathematical terms the number of ways the differences form in the set and the ratio ( lambda + 1)/(v) determines the light transmittance of said first and second masks for positions of said movable object other than said reference position.
Claim 6
Dependent Claim
24 words
Optical apparatus as in claim 3 in which v is equal to 63, k is equal to 31, and lambda is equal to 15.
Claim 7
Dependent Claim
43 words
Optical apparatus as in claim 4 where the geometry of said pattern is 0, 1, 2, 3, 4, 6, 7, 8, 9, 12, 13, 14, 16, 18, 19, 24, 26, 27, 28, 32, 33, 34, 35, 38, 41, 45, 48, 49, 52, 56.
Claim 8
Dependent Claim
29 words
Optical apparatus as in claim 3 in which said primary mask includes first and second adjacent sections one of said sections being offset from the other by one unit.
Claim 9
Dependent Claim
23 words
Optical apparatus as in claim 6 where said secondary mask includes first and second sections corresponding to said sections of said primary mask.
Claim 10
Dependent Claim
39 words
Optical apparatus as in claim 7 where the light sensitive means behind said secondary mask provides a double polarity reference pulse at said reference position the direction of said polarity change indicating the direction of movement of said object.
Claim 11
Dependent Claim
25 words
Optical apparatus as in claim 3 in which said primary mask lies wholly within a single track and includes means for polarization coding said mask.
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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) | 1975-10-10 | 1976-04-10 | 1976-10-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-10 | 1980-04-10 | 1980-10-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-10 | 1984-04-10 | 1984-10-10 | $7700.00 | Window Closed / Lapsed |