Natural color scanning electron microscopy based on the frequency characteristics of the human visual system

The principles of image formation in natural color scanning electron micros copy (NC-SEM) are discussed in detail. This method is based on the frequenc y characteristic of the human visual system. It is shown that the Mach effe ct and masking effect are important in the characteristics. The former, whi ch can enhance structural details, is visually similar to the edge effect i n secondary electron (SE) images, and the latter is required for proper rep resentation of very degraded color information obtained from a light micros cope. When using these effects suitably, an NC-SEM image with the resolutio n equivalent to that of an SEM image can be acquired. though it is composed of an SEM image and a special video microscopy (VM) image with a resolutio n much lower than the SEM image of the identical view. The NC-SEM is more e ffective than the SEM in observation, interpretation, and analysis of vario us samples with important color information.