Printer calibration method using electronically-decoupled color and tone scale adjustments
US5172224A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 18, 1990 |
| Grant date | Dec 15, 1992 |
| Priority date | — |
| Expiry date | Dec 18, 2010 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S347/90
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A calibration utility 22 for electronically-generated images decouples tone scale and color corrections by completing tone scale and color balance corrections upon separate RGB image signals (representative of intensity) and hue and saturation corrections upon combinations of RGB signals (representative of chrominance). An operator adjusts tone scale controls 32 and color controles 34, which provide values for calibrating separate RGB tone scale look-up tables 49a, 49b, and 49c and a color matrix 48 in a printer 14. To decouple the corrections, the tone scale look-up tables 49a, 49b, 49c are adjusted until the brightness of a predetermined number of image levels is accurately rendered. If the resultant image signal contains coloration in neutral areas, the values in the particular look-up table(s) for the color(s) producing the color cast in the neutral areas is adjusted, thereby producing a neutrally-adjusted image signal substantially free of neutral coloration. The hue and saturation of the image can then be adjusted by modifying terms in the color matrix 48 without affecting the tone scale reproduction.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.