US3761179A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Mirror testing apparatus
Assignee: Polaroid Corp
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Filing: 1971-08-26
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Granted: 1973-09-25
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Expires: 1991-08-26
Abstract
Abstract An apparatus automatically measures the reflecting surface of a mirror to evaluate its local flatness and its overall flatness. In one embodiment of the apparatus, two separate optical systems are arranged so a mirror under test forms a part of each optical system. One optical system forms a large beam of light which covers the entire surface of the mirror. The other optical system forms a small beam of light which covers only a small local area of the mirror, but it includes a device which sweeps the small beam over the entire surface of the mirror. Overall or local variations in flatness of the surface result in proportional variations of light intensity at detectors associated with each optical system. Electronic circuitry processes signals generated by the detector to decide if the signals indicate the surface of the mirror under test is within predetermined limits.
Inventors
- 👤 W Plummer
- 👤 U Salomon
- 👤 L Ting
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 04:02
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/30; G01B11/306; G01M; G01M11/00; G01M11/005
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
152 words
An apparatus comprising: a station for receiving a mirror whose surface topography is to be evaluated; a source plate having at least one transmitting aperture; lighting means, behind said source plate, for illuminating said transmitting aperture; a detecting station including a target plate having at least one receiving aperture; optical means, including said mirror, for forming an image of said transmitting aperture, using light emanating therefrom, at said receiving aperture; said optical means further including lens means to refract said light emanating from said transmitting aperture into a collimated beam incident on said mirror and to focus said collimated light after said mirror reflects said light to form an image of said transmitting aperture at said receiving aperture; photosensitive means, behind said target plate, for measuring the intensity of light from said transmitting aperture incident on said receiving aperture; and light chopping means to periodically interrupt the light reaching said photosensitive means.
Claim 2
Independent Claim
152 words
An apparatus comprising: a station for receiving a mirror whose surface topography is to be evaluated; a source plate having at least one transmitting aperture; lighting means, behind said source plate, for illuminating said transmitting aperture; a detecting station including a target plate having at least one receiving aperture; optical means, including said mirror, for forming an image of said transmitting aperture, using light emanating therefrom, at said receiving aperture; said optical means further including lens means to refract said light emanating from said transmitting aperture into a collimated beam incident on said mirror and to focus said collimated light after said mirror reflects said light to form an image of said transmitting aperture at said receiving aperture; photosensitive means, behind said target plate, for measuring the intensity of light from said transmitting aperture incident on said receiving aperture; and light chopping means to periodically interrupt the light reaching said photosensitive means.
Claim 3
Independent Claim
379 words
An apparatus comprising: a station for receiving and aligning a mirror whose surface topography is to be evaluated; a first source plate having at least one slot permitting light to pass through; first illuminating means behind said first source plate; a condenser to collect light from said first illuminating means and direct it onto said first source plate; a first rotatable disk having a plurality of radially extending slots; first optical means, including said mirror, for forming an image of said first source plate slot on said first rotatable disk, said optical means including means for collimating light incident on said mirror from said first source plate slot into a first light beam having an area substantially equal to the area of said mirror; a first light-detecting means, having at least One photosensitive element, positioned to receive light passing through said radially extending slots in said first rotatable disk, for generating a time-varying first signal proportional to the amount of light it receives at any instant; a second source plate having at least one slot permitting light to pass through; second illuminating means behind said second source plate; a condenser to collect light from said second illuminating means and direct it onto said second source plate; a second rotatable disk having a plurality of radially extending slots; second optical means, including said mirror, for forming an image of said second source plate slot on said second rotatable disk, said optical means including means for collimating light incident on said mirror from said second source plate slot into a second light beam; means for limiting said second light beam to an area substantially less than the area of said mirror at said mirror; scanning means for moving said second light beam across the surface of said mirror in a predetermined pattern; second light-detecting means, having at least one photosensitive element positioned to receive light passing through said radially extending slots in said second rotatable disk, for generating a time-varying second signal proportional to the amount of light it receives at any instant; and signal processing means for receiving said first and second signals generated by said first and second light-detecting means and comparing them with a reference signal to determine if said surface of said mirror is within precalibrated limits.
Claim 4
Independent Claim
379 words
An apparatus comprising: a station for receiving and aligning a mirror whose surface topography is to be evaluated; a first source plate having at least one slot permitting light to pass through; first illuminating means behind said first source plate; a condenser to collect light from said first illuminating means and direct it onto said first source plate; a first rotatable disk having a plurality of radially extending slots; first optical means, including said mirror, for forming an image of said first source plate slot on said first rotatable disk, said optical means including means for collimating light incident on said mirror from said first source plate slot into a first light beam having an area substantially equal to the area of said mirror; a first light-detecting means, having at least One photosensitive element, positioned to receive light passing through said radially extending slots in said first rotatable disk, for generating a time-varying first signal proportional to the amount of light it receives at any instant; a second source plate having at least one slot permitting light to pass through; second illuminating means behind said second source plate; a condenser to collect light from said second illuminating means and direct it onto said second source plate; a second rotatable disk having a plurality of radially extending slots; second optical means, including said mirror, for forming an image of said second source plate slot on said second rotatable disk, said optical means including means for collimating light incident on said mirror from said second source plate slot into a second light beam; means for limiting said second light beam to an area substantially less than the area of said mirror at said mirror; scanning means for moving said second light beam across the surface of said mirror in a predetermined pattern; second light-detecting means, having at least one photosensitive element positioned to receive light passing through said radially extending slots in said second rotatable disk, for generating a time-varying second signal proportional to the amount of light it receives at any instant; and signal processing means for receiving said first and second signals generated by said first and second light-detecting means and comparing them with a reference signal to determine if said surface of said mirror is within precalibrated limits.
Claim 5
Dependent Claim
52 words
The apparatus of claim 2, wherein at least one of said source plates has a pair of orthogonal slots and wherein the corresponding detecting means has a pair of photosensitive elements, each of said pair of photosensitive elements positioned to receive light from a specific one of said pair of orthogonal slots.
Claim 6
Dependent Claim
13 words
The apparatus of claim 2, wherein said scanning means comprises a Nipkow disk.
Claim 7
Dependent Claim
101 words
The apparatus of claim 2, further comprising: first signal averaging means for determining an average first signal from said first light-detecting means over a period of time that is long compared to the period of the fundamental frequency of said first signal but short compared to the period of observation of said mirror; and second signal averaging means for determining an average second signal from said second light-detecting means over a period of time that is long compared to the first period of the fundamental frequency of said second signal but short compared to the period of observation of said mirror.
Claim 8
Dependent Claim
48 words
The apparatus of claim 2, wherein said signal processing means includes means to maintain said average first and second signals from said first and said second signal averaging means each at a predetermined magnitude despite variations in the reflectivity of said mirror and its alignment at said station.
Claim 9
Dependent Claim
66 words
The apparatus of claim 6, wherein said light-detecting means each comprise a photomultiplier and said signal processing means comprises: means for generating a predetermined signal to compare said average signal with; a high-voltage supply for each said photomultiplier; and means for controlling each said high-voltage supply, so as to maintain said average signal, by comparing said average signal from its respective photomultiplier with said predetermined signal.
Claim 10
Dependent Claim
67 words
The apparatus of claim 6, further comprising: means for receiving and amplifying said signal from said light-detecting means; means for monitoring said signal after it is amplified and for generating a DC voltage proportional to the periodic amplitude of said signals generated by said each light detecting means; means for furnishing a predetermined reference voltage; and means for comparing said DC voltage with said predetermined reference voltage.
Claim 11
Dependent Claim
21 words
The apparatus of claim 8, further comprising: means for synchronizinG the operation of said signal processing means with said scanning means.
Claim 12
Dependent Claim
19 words
The apparatus of claim 6, wherein said means for controlling each said high-voltage supply comprises a low-pass servo amplifier.
Claim 13
Dependent Claim
61 words
The apparatus of claim 8, wherein: said means for receiving and amplifying said signal comprises a tuned amplifier; said means for generating a DC voltage proportional to the difference between maximum and minimum signals generated by each light-detecting means comprises an AC to DC converter; and said means for comparing said DC voltage with said predetermined voltage comprises a voltage comparator.
Claim 14
Independent Claim
187 words
An apparatus comprising: a station for receiving a mirror whose surface topography is to be evaluated; a source plate having at least one transmitting aperture; lighting means, behind said source plate, for illuminating said transmitting aperture; a detecting station including a target plate having at least one receiving aperture and further including light chopping means to periodically interrupt the light passing through said receiving aperture; optical means including said mirror for forming an image of said transmitting aperture, using light emanating therefrom at said receiving aperture, and further including means for collimating light incident on said mirror; zone means for limiting in a variable manner the size of a light beam incident on said mirror to a fraction of the area of said mirror, said zone means further including means for causing the limited size light beam to scan the total area of said mirror and means for varying the size of said beam in relation to the specified areas of said mirror being scanned; and photosensitive means, behind said target plate, for measuring the intensity of light from said transmitting aperture incident on said receiving aperture.
Claim 15
Independent Claim
187 words
An apparatus comprising: a station for receiving a mirror whose surface topography is to be evaluated; a source plate having at least one transmitting aperture; lighting means, behind said source plate, for illuminating said transmitting aperture; a detecting station including a target plate having at least one receiving aperture and further including light chopping means to periodically interrupt the light passing through said receiving aperture; optical means including said mirror for forming an image of said transmitting aperture, using light emanating therefrom at said receiving aperture, and further including means for collimating light incident on said mirror; zone means for limiting in a variable manner the size of a light beam incident on said mirror to a fraction of the area of said mirror, said zone means further including means for causing the limited size light beam to scan the total area of said mirror and means for varying the size of said beam in relation to the specified areas of said mirror being scanned; and photosensitive means, behind said target plate, for measuring the intensity of light from said transmitting aperture incident on said receiving aperture.
Claim 16
Dependent Claim
43 words
The apparatus of claim 12, further comprising: processing means, for evaluating the light measurements made by said photosensitive means and for determining if said measurements indicate that said surface of said mirror is within precalibrated limits; and indicator means for distinguishing certain mirrors.
Claim 17
Independent Claim
183 words
A method for testing a mirror wherein the blur of an image formed by said mirror is indicative of said mirror''s quality, comprising the steps of: positioning a first aperture; illuminating said first aperture; collimating light emanation from said first aperture; limiting the cross-section of said collimated light to a size less than the area of said mirror; scanning said limited collimated light across said mirror; changing the cross-section of said collimated light while scanning it across said mirror; reflecting said collimated light from said mirror forming an image of said first aperture with said collimated light reflected from said mirror at an image plane; positioning a second aperture of predetermined cross-section at said image plane to limit the size of said image transmitted through said second aperture; chopping said image transmitted through said second aperture; receiving the light forming said image transmitted through said second aperture on a photosensitive element; generating an electrical signal through means of said photosensitive element, periodic amplitude of said electrical signal related to the flatness of said mirror; and comparing said periodic amplitude to a reference amplitude.
Claim 18
Independent Claim
183 words
A method for testing a mirror wherein the blur of an image formed by said mirror is indicative of said mirror''s quality, comprising the steps of: positioning a first aperture; illuminating said first aperture; collimating light emanation from said first aperture; limiting the cross-section of said collimated light to a size less than the area of said mirror; scanning said limited collimated light across said mirror; changing the cross-section of said collimated light while scanning it across said mirror; reflecting said collimated light from said mirror forming an image of said first aperture with said collimated light reflected from said mirror at an image plane; positioning a second aperture of predetermined cross-section at said image plane to limit the size of said image transmitted through said second aperture; chopping said image transmitted through said second aperture; receiving the light forming said image transmitted through said second aperture on a photosensitive element; generating an electrical signal through means of said photosensitive element, periodic amplitude of said electrical signal related to the flatness of said mirror; and comparing said periodic amplitude to a reference amplitude.
References Cited (Backward Citations)
US2315282A
Cited
US2446628A
Cited
US2623927A
Cited
US2604809A
Cited
US2720812A
Cited
US3439988A
Cited
US3606541A
Cited
US3663107A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-24 | 1977-03-26 | 1977-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-24 | 1981-03-26 | 1981-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-24 | 1985-03-26 | 1985-09-25 | $7700.00 | Window Closed / Lapsed |