Self testing phototypesetter flash intensity control system
US4020495A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 29, 1975 |
| Grant date | Apr 26, 1977 |
| Priority date | — |
| Expiry date | Dec 29, 1995 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB41B21/12
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
An optical sensor is positioned at the output of a variable magnification optical system which focuses differing character size images upon a photosensitive medium. A reference voltage, which is a function of the proper exposure for a particular photosensitive medium, is compared with the photosensor voltage. The system automatically tests for the correct light flux before each size change by projecting a reference image through the optical system at the photosensor, such image having a relatively low intensity level, so that no output signal is produced by the above-mentioned comparator. The intensity of the reference image is iteratively increased until such output signal is produced by the comparator, thereby to maintain the light intensity at the last level attained, until a character size change is effected, wherein the comparison process is repeated. Upon the substitution of another photosensitive medium having a different sensitivity, the comparator threshold voltage is altered accordingly to produce the proper illumination intensities for various character sizes tailored to the sensitivity of the second photosensitive medium.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.