Digital color densitometer and exposure meter
US4194838A · kind A · utility
Inventors
Key dates
| Filing date | Feb 22, 1977 |
| Grant date | Mar 25, 1980 |
| Priority date | — |
| Expiry date | Feb 22, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B27/735
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A photometric device for measuring and displaying by digital means primary color densities of a color negative to be printed to determine densities of color compensating filters. Exposure time, including reciprocity effect compensation for the photographic paper, is displayed digitally and determined by density measurements of the projected image. A reference area of a color negative illuminated by light through color compensating filters is projected on the aperture of a probe which directs light through a light guide to a photodetector. The resulting photocurrents generate voltages amplified by a first and second variable gain linear amplifier. The second amplifier provides primary color and exposure density reference by means of gains stored by measurement of a standard negative. Digital display means is provided to display memory gains for accurately modifying or resetting reference gains. The output of the second amplifier is coupled to a signal integrator alternately gated by a pulse generator and an exposure-time controlled integrator. A voltage comparator and digital circuitry coupled to the signal integrator serve to display the density of color compensation negative optic…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.