Patent US3698809A successfully refreshed from Google Patents.
US3698809A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic illumination control for photographic printing apparatus
Assignee: Eastman Kodak Co
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Filing: 1971-10-07
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Granted: 1972-10-17
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Expires: 1991-10-07
Abstract
Abstract Photographic printing apparatus includes a reference light source and a mirror with the mirror adapted to be moved into the normal projection path of the apparatus to reflect light from the reference light source through the printing lens and onto the print plane. A photocell in the print plane detects the light from the reference light source and effectively compares it with a reference potential to thereby control the opening of a diaphragm in the printing lens to maintain a constant illumination per unit area on the print plane.
Inventors
- 👤 James E Harter
- 👤 Juan A Rodriguez
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 07:59
CPC Classifications
G; G03; G03B; G03B7/00; G03B7/08; G03B7/081; G03B7/085; G03B27/00; G03B27/72
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
190 words
In photographic printing apparatus including a print plane adapted to receive paper for printing, a transparency holder and a projection light source adapted to be directed through a transparency in the holder for projection onto the print plane, lens means including a diaphragm interposed between said transparency holder and said print plane for magnifying and focusing the image of said transparency on said print plane, and means for varying the magnification of an image projected onto said print plane, improved illumination control apparatus comprising: a first source of reference potential corresponding to a predetermined illumination per unit area on the print plane; a reference light source; means for directing light from said reference light source through said lens means for projection onto the print plane; light detecting means in the print plane for intercepting light from said reference light source operative to produce an output proportional to the illumination level; and means for comparing the output of said light detecting means with said reference potential and for thereby controlling the opening of the diaphragm of said lens means to provide the predetermined illumination per unit area on the print plane.
Claim 2
Dependent Claim
190 words
In photographic printing apparatus including a print plane adapted to receive paper for printing, a transparency holder and a projection light source adapted to be directed through a transparency in the holder for projection onto the print plane, lens means including a diaphragm interposed between said transparency holder and said print plane for magnifying and focusing the image of said transparency on said print plane, and means for varying the magnification of an image projected onto said print plane, improved illumination control apparatus comprising: a first source of reference potential corresponding to a predetermined illumination per unit area on the print plane; a reference light source; means for directing light from said reference light source through said lens means for projection onto the print plane; light detecting means in the print plane for intercepting light from said reference light source operative to produce an output proportional to the illumination level; and means for comparing the output of said light detecting means with said reference potential and for thereby controlling the opening of the diaphragm of said lens means to provide the predetermined illumination per unit area on the print plane.
Claim 3
Dependent Claim
14 words
The invention according to claim 1 wherein said light detecting means is a photocell.
Claim 4
Dependent Claim
28 words
The invention according to claim 2 additionally comprising a composing screen adapted to be inserted into the print plane, whereIn said photocell is mounted on said composing screen.
Claim 5
Dependent Claim
127 words
The invention according to claim 2 said comparing and controlling means comprising: a current-to-voltage converter amplifier having first and second input terminals and an output terminal; means connecting said photocell across the first and second input terminals of said current-to-voltage converter amplifier; a voltage converter amplifier having first and second input terminals and an output terminal; means connecting the output of said current-to-voltage converter amplifier to the first input terminal of said voltage comparator amplifier; means for applying said source of reference potential to the second input terminal of said voltage comparator amplifier; and a drive motor connected between said diaphragm and the output of said voltage comparator amplifier operative to vary the opening of said diaphragm in response to the output of said voltage comparator amplifier.
Claim 6
Dependent Claim
102 words
The invention according to claim 1, wherein said reference light source is located outside of the direct light path between said projection light source and the print plane, additionally comprising: a reflective mirror located between said transparency holder and said lens means; means for positioning said reflective mirror in a first position in said light path to reflect light from said reference light source through said lens means onto said print plane; and means for positioning said reflective mirror in a second position out of said light path, whereby light from said reference light source does not pass through said lens apparatus.
Claim 7
Dependent Claim
52 words
The invention according to claim 5 wherein said reference light source comprises: a source of illumination; and a diffuser positioned between said source of illumination and said reflective mirror such that when said mirror is in said first position, said diffuser is in the same effective focal plane as said transparency holder.
Claim 8
Dependent Claim
14 words
The invention according to claim 6 wherein said source of illumination comprises a lamp.
Claim 9
Dependent Claim
25 words
The invention according to claim 6 wherein said source of illumination comprises a fiber optic light rod between said projection light source and said diffuser.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-17 | 1976-04-17 | 1976-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-17 | 1980-04-17 | 1980-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-17 | 1984-04-17 | 1984-10-17 | $7700.00 | Window Closed / Lapsed |