US3849643A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic focusing apparatus
Assignee: ASAHI KOGAHU KAGYO KK
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Filing: 1973-11-29
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Granted: 1974-11-19
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Expires: 1993-11-29
Abstract
Abstract An image is formed on a plane by light passing through a lens. The lens and the plane are movable relative to each other so as to focus the image. A two-dimensional diffraction grating, preferably of the phase grating type, is disposed in the optical path at a distance spaced away from the plane. A scanning mechanism is provided including a plate disposed between the diffraction grating and the plane, and having a slit therethrough. Light passing through the diffraction grating and through the slit impinges upon a photoelectric element, preferably a CdS cell exhibiting a dip effect, which provides an electrical signal used in a positioning mechanism that provides for maximizing the contrast of the image formed by the light passing through the diffraction grating and impinging on the photoelectric element so as to bring the image into focus.
Inventors
- 👤 H Takeda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 01:25
CPC Classifications
G; G02; G02B; G02B7/00; G02B7/28; G02B7/36; G02B27/00; G02B27/42; G02B27/46
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
225 words
AutoMatic focusing apparatus comprising: first means, including a lens, defining an optical path such that at least a portion of light passing through the lens impinges upon a plane, the lens and the plane being movable relative to each other in either of two opposite directions along the optical path, second means, including a photoelectric element responsive to the light impinging upon the plane, for producing an electrical focusing control signal that varies in accordance with the degree of contrast in the light impinging upon the plane, the degree of contrast being maximum for an in-focus spacing between the lens and the plane, third means, for increasing the difference between the degree of contrast obtained at an in-focus spacing and the degree of contrast obtained at an out-of-focus spacing, the third means including an optical transmission function filter comprising a two-dimensional diffraction grating disposed in the optical path and spaced from both the lens and the plane, and the third means further including a scanning mechanism comprising oscillating means and a plate disposed between the grating and the plane and having a slit therethrough through which the light passes in accordance with the oscillating means; and fourth means, responsive to the electrical focusing control signal for adjusting the spacing between the lens and the plane to a relative position that maximizes the degree of contrast.
Claim 2
Dependent Claim
225 words
AutoMatic focusing apparatus comprising: first means, including a lens, defining an optical path such that at least a portion of light passing through the lens impinges upon a plane, the lens and the plane being movable relative to each other in either of two opposite directions along the optical path, second means, including a photoelectric element responsive to the light impinging upon the plane, for producing an electrical focusing control signal that varies in accordance with the degree of contrast in the light impinging upon the plane, the degree of contrast being maximum for an in-focus spacing between the lens and the plane, third means, for increasing the difference between the degree of contrast obtained at an in-focus spacing and the degree of contrast obtained at an out-of-focus spacing, the third means including an optical transmission function filter comprising a two-dimensional diffraction grating disposed in the optical path and spaced from both the lens and the plane, and the third means further including a scanning mechanism comprising oscillating means and a plate disposed between the grating and the plane and having a slit therethrough through which the light passes in accordance with the oscillating means; and fourth means, responsive to the electrical focusing control signal for adjusting the spacing between the lens and the plane to a relative position that maximizes the degree of contrast.
Claim 3
Dependent Claim
29 words
Apparatus according to claim 1 wherein the oscillating means is coupled to rotate the plate about an axis parallel to the path of the light passing through the slit.
Claim 4
Dependent Claim
26 words
Apparatus according to claim 1 wherein the oscillating means is coupled to vibrate the plate so that the light passing through the slit is linearly scanned.
Claim 5
Dependent Claim
33 words
Apparatus according to claim 1 wherein the first means includes a mirror for reflecting the light toward the plane, and wherein the oscillating means is coupled to the mirror to move it cyclically.
Claim 6
Dependent Claim
49 words
Apparatus according to claim 1 further comprising a shifter unit for translating the diffraction grating so as to vary the center frequency of the optical transmission function optical filter and thereby enable higher sensitivity defocusing detection irrespective of the power spectrum distribution of the light passing through the lens.
References Cited (Backward Citations)
US3450018A
Cited
US3781110A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-18 | 1978-05-20 | 1978-11-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-18 | 1982-05-20 | 1982-11-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-18 | 1986-05-20 | 1986-11-19 | $7700.00 | Window Closed / Lapsed |