Enhancement of fine detail in the presence of large radiance differences

A technique is described for enhancing fine detail in the production of radiance pictures of targets in which large differences also occur, and where the dynamic range of the picture viewing system is limited. This is achieved by scannig a raster with a mirror-chopper fed detector over the target area, and referencing one sampled area on this target against the next, the radiance intensity from which is reduced by a constant factor. The detector output is then a difference curve related to a derivative trace of the radiance profile, superimposed on the true radiance profile reduced in intensity. The method is compared with a similar technique previously used by Low(2), and examples of the use of the present technique both in the laboratory and in observing a feature on the lunar surface are included.