Automatic density control
US4017179A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 4, 1975 |
| Grant date | Apr 12, 1977 |
| Priority date | — |
| Expiry date | Sep 4, 1995 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B27/735
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An automatic density control device for photographic printers for sensing and correcting for a "subject failure" in a photographic negative, where the subject area of the negative is out of the optimum density ratio to the background area, which device includes a frusto-pyramidal radiation directing member having its enlarged end proximate to the negative and its small end remote therefrom and being positioned to receive the radiation from a source through the negative and having subject sensing means mounted at the central portion of the enlarged proximate end of said member to sense the radiation passing through the central subject area of the negative and also having background sensing means mounted at the diminished remote end to sense the radiation passing through the marginal portions of the negative and the marginal portions of the enlarged end of said member and including circuitry for comparing the signals produced by said subject sensing means and background sensing means and thus deriving a density signal which is used to control the exposure time during the printing process.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.