US3778150A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Printing of photographic colour negatives
Assignee: Individual
•
Filing: 1971-10-27
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Granted: 1973-12-11
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Expires: 1991-10-27
Abstract
Abstract Apparatus for screening photographic colour negatives to determine the exposure time and colour filtering required to produce an acceptable colour print. The apparatus incorporates a photoresistor connected in series with an adjustable resistance calibrated in terms of exposure times, the photoresistor and adjustable resistance constituting two arms of a bridge circuit. A further two arms are constituted selectably by either a fixed resistor network or by one or other of two potentiometers calibrated in terms of colour filter densities, switches being provided to enable selection. Alternatively one potentiometer appropriately switched can serve the function of the two potentiometers. A detector circuit senses balance in the bridge circuit. The calibration of the adjustable resistance and potentiometers, and the way the apparatus is used are explained.
Inventors
- 👤 K Aston
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:32
CPC Classifications
G; G03; G03B; G03B27/00; G03B27/72; G03B27/73
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
239 words
Apparatus for determining the color balance for photographic color negatives which are printed on a color printer having a source of illumination which directs light through the negative and color correction filters to the printing paper, said apparatus comprising: a two terminal voltage source; first, second and third primary tricolor filters arranged on a moveable tray; a photosensitive device whose resistance varies in response to the light impinging upon it, said photosensitive device being located so as to receive part of the light from the source of illumination after it has passed through the negative, the color correction filters and at least one of said primary tricolor filters, one end of said photo sensitive device being connected to the first end of said voltage source; a logarithmically variable resistance connected between the other end of said photo sensitive device and the second end of said voltage source; first and second resistances connected in series across said voltage source; at least one linear potentiometer having its ends connected across said voltage source; a two input detector means for producing an output whenever the voltages on its inputs are substantially equal, the first input on said detector means being connected to the junction of said photosensitive device and said logarithmically variable resistance; and switching means for selectively connecting the junction of said first and second resistances and the wiper of said linear potentiometer to the second input of said detector means.
Claim 2
Dependent Claim
239 words
Apparatus for determining the color balance for photographic color negatives which are printed on a color printer having a source of illumination which directs light through the negative and color correction filters to the printing paper, said apparatus comprising: a two terminal voltage source; first, second and third primary tricolor filters arranged on a moveable tray; a photosensitive device whose resistance varies in response to the light impinging upon it, said photosensitive device being located so as to receive part of the light from the source of illumination after it has passed through the negative, the color correction filters and at least one of said primary tricolor filters, one end of said photo sensitive device being connected to the first end of said voltage source; a logarithmically variable resistance connected between the other end of said photo sensitive device and the second end of said voltage source; first and second resistances connected in series across said voltage source; at least one linear potentiometer having its ends connected across said voltage source; a two input detector means for producing an output whenever the voltages on its inputs are substantially equal, the first input on said detector means being connected to the junction of said photosensitive device and said logarithmically variable resistance; and switching means for selectively connecting the junction of said first and second resistances and the wiper of said linear potentiometer to the second input of said detector means.
Claim 3
Dependent Claim
24 words
Apparatus as claimed in claim 1 wherein the resistance of said logarithmically variable resistance extends over the range of resistances of said photosensitive device.
Claim 4
Dependent Claim
16 words
Apparatus as claimed in claim 1 wherein said first and second resistances are equal in value.
Claim 5
Dependent Claim
13 words
Apparatus as claimed in claim 1 wherein said photosensitive device is a photoresistor.
Claim 6
Dependent Claim
23 words
Apparatus as claimed in claim 1 wherein said detector means is a high gain field-effect transistor input amplifier whose output energizes a lamp.
Claim 7
Dependent Claim
39 words
Apparatus as claimed in claim 1 further including a housing separate from said printer for containing said apparatus, said housing having a window in one surface to permit light to enter the housing and impinge upon said photosensitive device.
Claim 8
Dependent Claim
47 words
Apparatus as claimed in claim 1 further including a head for containing said photosensitive device, said photosensitive device in said head being connected to said voltage source and said logarithmically variable resistance by electrical leads, said head being coupled to the objective lens of a color printer.
Claim 9
Dependent Claim
46 words
Apparatus as claimed in claim 1 further including a second linear potentiometer having its ends connected in parallel with the said first linear potentiometer, said switching means being adapted to connect the wiper of said second linear potentiometer to the second input of said detector means.
Claim 10
Dependent Claim
56 words
Apparatus as claimed in claim 8 further including a pointer knob and moveable scales associated with said logarithmically variable resistance and said linear potentiometers, the scales associated with said logarithmically variable resistance being representative of exposure time and the scales associated with said linear potentiometers, each being representative of filter densities for a different color component.
Claim 11
Dependent Claim
54 words
Apparatus as claimed in claim 1 wherein said switching means is operatively connected to the tray of said three tricolor filters so as to place a different one of said tricolor filters between the source of illumination and photosensitive device with each selection of a connection to the second input of said detector means.
References Cited (Backward Citations)
US3067649A
Cited
GB1065261A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-10 | 1977-06-11 | 1977-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-10 | 1981-06-11 | 1981-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-10 | 1985-06-11 | 1985-12-11 | $7700.00 | Window Closed / Lapsed |