Patent US3617119A successfully refreshed from Google Patents.
US3617119A
Expired / Lapsed
US
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Method and apparatus for automatically focusing film projectors
Assignee: Eastman Kodak Co
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Filing: 1969-10-01
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Granted: 1971-11-02
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Expires: 1989-10-01
Abstract
Abstract A device for automatically adjusting the focus of a film projector to compensate for film distortion caused by the sudden heating experienced by the film frame located in the projection gate as a result of absorption of radiant energy from the projection lamp. The distortion that each successive film frame will experience in the gate is predicted by measuring density characteristics of that frame before it arrives at the gate and the focus of the projector is adjusted accordingly in substantial synchronism with the movement of that frame into the gate.
Inventors
- 👤 Armin B Pagel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 16:06
CPC Classifications
G; G03; G03B; G03B21/00; G03B21/14; G03B21/53
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
219 words
For use in a film projector including: a. a projection gate adapted to support a film frame, b. film-transporting means for moving a film frame along a predetermined path into said gate, c. a light source for illuminating a film frame supported in said gate, and d. a projection lens for focusing a projected image of the illuminated film frame in said gate at a predetermined projected image plane; an automatic focusing apparatus for substantially correcting defocusing of the projected image of a film frame located in said gate which occurs as a result of distortion of said frame due to its absorption of radiant energy from said light source, said apparatus comprising e. density-measuring means for measuring a distortion determinative density characteristic of a film frame located at a predetermined sensing position along said path and for providing an output functionally related to such measurement, f. focus-adjusting means automatically responsive to the output of said density-measuring means for effecting focusing adjustment of the distance between said projection lens and said film gate as a function of such output, and g. delay means for delaying the focus-adjusting response of said focus-adjusting means to said output to substantially synchronize said focusing adjustment with the occurrence of the distortion experienced by the corresponding film frame upon illumination thereof in said gate.
Claim 2
Dependent Claim
219 words
For use in a film projector including: a. a projection gate adapted to support a film frame, b. film-transporting means for moving a film frame along a predetermined path into said gate, c. a light source for illuminating a film frame supported in said gate, and d. a projection lens for focusing a projected image of the illuminated film frame in said gate at a predetermined projected image plane; an automatic focusing apparatus for substantially correcting defocusing of the projected image of a film frame located in said gate which occurs as a result of distortion of said frame due to its absorption of radiant energy from said light source, said apparatus comprising e. density-measuring means for measuring a distortion determinative density characteristic of a film frame located at a predetermined sensing position along said path and for providing an output functionally related to such measurement, f. focus-adjusting means automatically responsive to the output of said density-measuring means for effecting focusing adjustment of the distance between said projection lens and said film gate as a function of such output, and g. delay means for delaying the focus-adjusting response of said focus-adjusting means to said output to substantially synchronize said focusing adjustment with the occurrence of the distortion experienced by the corresponding film frame upon illumination thereof in said gate.
Claim 3
Dependent Claim
69 words
The invention defined by claim 1 in which said density-measuring means comprises: a. illumination means for impinging a beam of light of substantially constant intensity on a film frame located at said sensing position and b. photoresponsive means for measuring the absorption by the film frame at said sensing position of light impinged thereon by said illumination means and for providing said output as a function of such absorption.
Claim 4
Dependent Claim
17 words
The invention defined by claim 2 in which said beam of light originates at said light source.
Claim 5
Dependent Claim
35 words
The invention defined by claim 2 in which said photoresponsive means comprises a photocell adapted to be illuminated by light from said beam transmitted through a frame of film located at said predetermined sensing position.
Claim 6
Dependent Claim
31 words
The invention defined by claim 2 including monitored area defining means limiting the measurement of said density characteristic to a predetermined region of the film frame located at said sensing position.
Claim 7
Dependent Claim
24 words
The invention defined by claim 2 including a light-filtering means for modulating the response of said density-sensing means in accordance with predetermined spectral criteria.
Claim 8
Dependent Claim
87 words
The invention defined by claim 1 including: a. lens support means supporting said projection lens for focus-adjusting movement and b. means comprising said focus-adjusting means including i. electrical means for producing an electrical current functionally related to said output of said density-measuring means and ii. electrically operated movement producing means operatively connected to said lens support means and controlled by said electrical current for moving said projection lens to adjust the focus thereof as a function of the distortion determinative density characteristic measured by said density-measuring means.
Claim 9
Dependent Claim
73 words
The invention defined by claim 7 in which said electrically operated movement-producing means includes: a. an elongate wire having relatively high resistive and thermal expansion characteristics, b. conductor means for conducting said electrical current through said wire, and c. linkage means for translating into focus-adjusting movement of said projection means variations in the length of said wire produced by changes in its temperature determined by corresponding changes in said electrical current passing therethrough.
Claim 10
Independent Claim
150 words
The method of correcting defocusing of a projection lens in a film projector to compensate for thermal distortion experienced by a filM frame positioned within the film projection gate of said projector as a result of absorption by that film frame of radiant energy from a source of projection illumination, said method comprising the steps of a. measuring a predetermined light-absorptive characteristic of said film frame before said film frame is moved into said gate, b. predicting from that measurement the distortion that will be experienced by said film frame under the illumination influence to which it will be subjected within said gate to determine the necessary focus adjustment required to maintain sharp focus of said film frame after such distortion thereof has occurred in said gate, and c. effecting the focus adjustment so predicted in predetermined timed relation to the movement of said film frame into said projection gate.
Claim 11
Independent Claim
150 words
The method of correcting defocusing of a projection lens in a film projector to compensate for thermal distortion experienced by a filM frame positioned within the film projection gate of said projector as a result of absorption by that film frame of radiant energy from a source of projection illumination, said method comprising the steps of a. measuring a predetermined light-absorptive characteristic of said film frame before said film frame is moved into said gate, b. predicting from that measurement the distortion that will be experienced by said film frame under the illumination influence to which it will be subjected within said gate to determine the necessary focus adjustment required to maintain sharp focus of said film frame after such distortion thereof has occurred in said gate, and c. effecting the focus adjustment so predicted in predetermined timed relation to the movement of said film frame into said projection gate.
References Cited (Backward Citations)
GB1109215A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-01 | 1975-05-03 | 1975-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-01 | 1979-05-03 | 1979-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-01 | 1983-05-03 | 1983-11-02 | $7700.00 | Window Closed / Lapsed |