Image reproduction using sharp and unsharp signals
US4237481A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 20, 1979 |
| Grant date | Dec 2, 1980 |
| Priority date | — |
| Expiry date | Sep 20, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N1/4092
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
This relates to a method of image reproduction in which detail enhancement is carried out using sharp and unsharp signals (S and U), for example in accordance with the expression EQU P=K (log U- log S)- log S where P is the derived picture signal and K is a constant. To reduce the disparity between the fringe amplitudes and steepness on the two sides of a density boundary, the above expression is modified, in accordance with the invention to EQU P=K {log[U+L (U-S)]}-(K+1) log S. Another expression involving the same subtractions of sharp and unsharp signals as the first expression above but in a form suitable for use with signals which have been compressed to represent luminance, is modified in accordance with the invention in a similar way.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.