US3619067A
Expired / Lapsed
US
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Method and apparatus for determining optical focal distance
Assignee: Massachusetts Institute of Technology
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Filing: 1970-01-19
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Granted: 1971-11-09
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Expires: 1990-01-19
Abstract
Abstract The location of the focal surface of a lens system is precisely determined, using a retroreflector on one side of the lens system and a bifurcated light guide of intermixed fibers on the other side, with one set of the light guide fibers leading to a source of light and another set leading to a light detector. The bifurcated light guide is moved relative to the lens system and the position which results in a minimum of light output to the detector determines precisely the location of the focal surface of the lens system.
Inventors
- 👤 Bradford Howland
- 👤 Arthur F Proll
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 23:04
CPC Classifications
G; G01; G01M; G01M11/00; G01M11/02; G01M11/0228; G02; G02B; G02B6/00; G02B6/04; G02B6/06
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
153 words
Optical apparatus for determining the optical focal distance of a lens system comprising: a source of light, means for detecting a nadir in the intensity of light incident thereon, a focusing lens system, means along the optical axis of the lens system on one side thereof which reflects light from one path which is parallel to the optical axis to a parallel oppositely directed path, whereby light from the focal plane of the lens system on the other side thereof passes through the lens system, is reflected and focused by the lens system of the focal plane, means for directing light from the source to the point, means for directing light from the point to the detecting means and means for measuring the distance between the point and the lens system, whereby the distance measured when the light detected is at a nadir is representative of the focal distance of the lens system.
Claim 2
Dependent Claim
153 words
Optical apparatus for determining the optical focal distance of a lens system comprising: a source of light, means for detecting a nadir in the intensity of light incident thereon, a focusing lens system, means along the optical axis of the lens system on one side thereof which reflects light from one path which is parallel to the optical axis to a parallel oppositely directed path, whereby light from the focal plane of the lens system on the other side thereof passes through the lens system, is reflected and focused by the lens system of the focal plane, means for directing light from the source to the point, means for directing light from the point to the detecting means and means for measuring the distance between the point and the lens system, whereby the distance measured when the light detected is at a nadir is representative of the focal distance of the lens system.
Claim 3
Dependent Claim
21 words
Optical apparatus as in claim 1 and in which the point is located on the optical axis of the lens system.
Claim 4
Dependent Claim
20 words
Optical apparatus as in claim 2 and in which the distance between the point and the lens system is variable.
Claim 5
Dependent Claim
26 words
Optical apparatus as in claim 1 and in which the means which reflects light from one path to a parallel oppositely directed path is a retroreflector.
Claim 6
Dependent Claim
27 words
Optical apparatus as in claim 1 and in which the means which reflects light from one path to a parallel oppositely directed path is a corner reflector.
Claim 7
Dependent Claim
28 words
Optical apparatus as in claim 1 and in which the means which reflects light from one path to a parallel oppositely directed path is a cube corner prism.
Claim 8
Dependent Claim
70 words
Optical apparatus as in claim 1 and in which the means for directing light from the source to point and the means for directing light from the point to the detecting means includes a bifurcated optical fiber light guide, one end of which is at the point and from which one set of fibers extends to the source of light and the other extends to the means for detecting light.
Claim 9
Dependent Claim
25 words
Optical apparatus as in claim 7 and in which the fibers from each set are intermixed in the bifurcated light guide at the one end.
Claim 10
Dependent Claim
18 words
Optical apparatus as in claim 8 and in which the fibers at the one end are randomly intermixed.
Claim 11
Dependent Claim
111 words
In optical apparatus for aid in focusing on a given surface an image of an object at a given location the combination comprising: a lens system along an optical path between the surface and the position of the object, a mirror at the location of the object, a source of light, means for detecting the intensity of light incident thereon, a bifurcated optical fiber light guide, one end of which is contiguous with the surface and from which two sets of fibers extend, one set extends to the source of light and the other extends to the detecting means, whereby optimum focusing occurs when the detected intensity is at a nadir.
Claim 12
Dependent Claim
111 words
In optical apparatus for aid in focusing on a given surface an image of an object at a given location the combination comprising: a lens system along an optical path between the surface and the position of the object, a mirror at the location of the object, a source of light, means for detecting the intensity of light incident thereon, a bifurcated optical fiber light guide, one end of which is contiguous with the surface and from which two sets of fibers extend, one set extends to the source of light and the other extends to the detecting means, whereby optimum focusing occurs when the detected intensity is at a nadir.
Claim 13
Dependent Claim
28 words
Optical apparatus as in claim 10 and in which means are provided for varying the position of the lens system while monitoring the intensity of the light detected.
Claim 14
Dependent Claim
28 words
Optical apparatus as in claim 10 and in which means are provided for varying the focal length of the lens system while monitoring the intensity of light detected.
Claim 15
Independent Claim
78 words
A method for determining a focal surface of a lens system comprising the steps of: producing an object on one side of the lens system, the distance between the object and the lens system being variable, direcTing light from the object which is transmitted by the lens system to a retroreflector, and detecting the intensity of light from the object which is reflected by the retroreflector through the lens system and which does not fall on the object.
Claim 16
Independent Claim
78 words
A method for determining a focal surface of a lens system comprising the steps of: producing an object on one side of the lens system, the distance between the object and the lens system being variable, direcTing light from the object which is transmitted by the lens system to a retroreflector, and detecting the intensity of light from the object which is reflected by the retroreflector through the lens system and which does not fall on the object.
Claim 17
Dependent Claim
36 words
A method as in claim 13 and further including the steps of: varying the distance between the object and the lens system, and selecting the distance at which the intensity of detected light is at nadir.
Claim 18
Independent Claim
98 words
A method for focusing with a lens system an image of an object on a surface comprising the steps of: placing a mirror at the position of the object, producing a second object on the opposite side of the lens system, the distance between the second object and the lens system being variable, directing light from the second object, which is transmitted by the lens system to the mirror, and detecting the intensity of light from the second object which is reflected from the mirror through the lens system and which does not fall on the second object.
Claim 19
Independent Claim
98 words
A method for focusing with a lens system an image of an object on a surface comprising the steps of: placing a mirror at the position of the object, producing a second object on the opposite side of the lens system, the distance between the second object and the lens system being variable, directing light from the second object, which is transmitted by the lens system to the mirror, and detecting the intensity of light from the second object which is reflected from the mirror through the lens system and which does not fall on the second object.
Claim 20
Dependent Claim
39 words
A method as in claim 15 and further including the steps of: varying the distance between the second object and the lens system, and selecting the distance at which the intensity of the detected light is at a nadir.
Claim 21
Dependent Claim
31 words
A method as in claim 16 and further including the steps of: directing the lens system at the object and disposing a light-sensitive surface at the position of the second object.
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) | 1974-11-08 | 1975-05-10 | 1975-11-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-08 | 1979-05-10 | 1979-11-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-08 | 1983-05-10 | 1983-11-09 | $7700.00 | Window Closed / Lapsed |