MECHANISM FOR ELIMINATING COLORED SHADOW/HIGHLIGHT ERRORS IN SCANNED COLOR IMAGE

摘要

Colored shadows (and highlights) in a reproduced color image, caused by limited sensitivities in different channels of an image scanning device, such as a multicolor video camera, are effectively eliminated by controllably adjusting the signal intensity of the output signals of one of the channels in dependance upon whether or not the level of that signal is within a limited region of the camera's response characteristic. As long as the signal level of the channel of interest, (e.g. blue color band channel), lies within a non-limited portion of the sensitivity range of the camera for that channel, the intensity of that channel's output signals are left unchanged. However, in response to the level of the channel's output signals falling within a limited portion of the sensitivity range of the camera, the intensity of that channel's output signals is effectively corrected by substituting in their place the output signals of another camera channel (e.g. the green channel), the dynamic range of which extends beyond that of the limited channel. As a consequence, in the reproduced image, regions, such as shadows and highlights, having intensity levels in the vicinity of one of the extremes of the sensitivity range of the camera, will tend to be neutral and thereby provide a higher quality image.