Circuit to improve the contrast of a detail of a video image

Abstract

Abstract 1. Video signal processing circuit comprising an automatic contrast expansion circuit (14) receiving the video signal and having the function of expanding its amplitude and aligning it between a predetermined lower reference voltage and upper reference voltage, a window generator (16) producing a window signal (F), a switching circuit (12) controlled by the window generator (16) for directing to the output of the processing circuit on the one hand the video signal processed by the expanding circuit during the time intervals corresponding to the window and on the other hand the video signal during the remaining time intervals of the image, i.e. outside the window, characterized in that the expanding circuit (14) is also controlled by the window generator for aligning the darkest point of the window with the lower reference voltage and the brightest point of the window with the upper reference voltage, and that it includes a complementary automatic contrast expanding circuit (10) receiving said video signal and having the same function as the first but relatively to the entirety of the image, the switching circuit directing to said output of said processing circuit the video signal processed by the complementary circuit during said time intervals outside the window.

Inventors

• 👤 Claude Lepage
• 👤 Gérard Voisin

Bibliographic Details