Abstract:
A histogram equalization system that adaptively redistributes the intensity coding of the video in order to provide an equal number of elements at all display intensity levels. The actual amplitude value of the input video as stored in an integrator, for example, is utilized to address a random access memory which originally is loaded with all zeros. The memory is organized such that there are as many addressable words as there are possible video intensity values carried in the integrator thereby building up a histogram within the memory. Upon completion of the histogram, a constant equal to the number of picture elements corresponding to the data used to form the histogram divided by the number of values to which it is desired to truncate, is utilized in a comparator as the histogram memory is sequentially read out and accumulated to determine the truncation points. A latching circuit is filled with the truncation point values and these points are used in a truncation logic circuit responding to the input video signal to reduce the number of video bits. The truncated signal increases the sensitivity to localized signal variations of a scene so as to increase the detail of the gray scale region requiring additional intensity codes.