The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 28, 1995
Filed:
Jun. 14, 1993
Stephen Herman, Monsey, NY (US);
Philips Electronics North America Corporation, New York, NY (US);
Abstract
Ordinarily, television signals are subjected to gamma correction at the source to compensate for non-linearities in CRT-based displays in accordance with set standards. However, it has been found in practice that all CRT-based displays do not exhibit the same amount of non-linearity. Hence, some television receivers include gamma correction circuitry which compensate for the difference between the particular CRT display and that assumed by the transmission system standard. In addition the above, circuitry is added for adapting this correction to local areas on the display thereby achieving dynamic range equalization. The input video signal is first low-pass filtered and then subjected to a normalization between 0.0 and a first predefined maximum value A. A second predefined value B is then added to this normalized signal generating a gamma exponential. At the same time, the input video signal is normalized for the range 0.0 and 1.0. This normalized input signal is then raised to an exponential power equivalent to the gamma exponential. Finally, this resultant signal is re-scaled back to the dynamic range of the input video signal. The resultant video signal on display then has the dark portions thereof more visible without the bright parts looking washed out.