US3856407A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic focusing device
Assignee: Pentax Corp
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Filing: 1973-11-02
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Granted: 1974-12-24
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Expires: 1993-11-02
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 photoelectric element, preferably a CdS cell exhibiting a dip effect, is disposed in the plane and 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
- 👤 H Kawasaki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 12:27
CPC Classifications
G; G01; G01C; G01C3/00; G01C3/32; G02; G02B; G02B27/00; G02B27/40; G02B27/42; G02B27/46; G02B7/00; G02B7/28; G02B7/36
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
183 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 photoelectic 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, an optical transmission function filter for increasing the difference between the degree of contrast obtained at an infocus spacing and the degree of contrast obtained at an out-offocus spacing, the filter comprising a two-dimensional diffraction grating disposed in the optical path and spaced from both the lens and the plane, and third 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
183 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 photoelectic 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, an optical transmission function filter for increasing the difference between the degree of contrast obtained at an infocus spacing and the degree of contrast obtained at an out-offocus spacing, the filter comprising a two-dimensional diffraction grating disposed in the optical path and spaced from both the lens and the plane, and third 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 third means includes a motor mechanically coupled to move the lens and electrically coupled to respond to the electrical focusing control signal.
Claim 4
Dependent Claim
69 words
Apparatus according to claim 2 further including oscillating means for cyclically varying the optical path length between the two-dimensional diffraction grating and the plane whereby the control signal has a carrier frequency having opposite phases on opposite sides of the in-focus position, and wherein the third means includes a phase detector circuit responsive to the control sequel and the oscillating means for producing a signal for controlling the motor.
Claim 5
Dependent Claim
63 words
Apparatus according to claim 3 further comprising means for shifting the two-dimensional diffraction grating in either of two opposite directions relative to the plane, an electrically controlled indicator and circuit means coupling the electrical control signal to the indicator so as to provide a display indicating whether the spacing between the grating and the plane provides the optimum relative spacing for automatic focusing.
Claim 6
Dependent Claim
46 words
Apparatus according to claim 2 wherein the third means includes a pair of memory circuits, circuit means coupling the electrical focusing control signal to alternate ones of the memory circuits and comparison means responsive to the memory circuits for producing a signal for controlling the motor.
Claim 7
Dependent Claim
63 words
Apparatus according to claim 5 further comprising means for shifting the two-dimensional diffraction grating in either of two opposite directions relative to the plane, an electrically controlled indicator, and circuit means coupling the electrical control signal to the indicator so as to provide a display indicating whether the spacing between the grating and the plane provides the optimum relative spacing for automatic focusing.
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) | 1977-12-23 | 1978-06-24 | 1978-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-23 | 1982-06-24 | 1982-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-23 | 1986-06-24 | 1986-12-24 | $7700.00 | Window Closed / Lapsed |