||Differential Interference Contrast optical system has played an important role
in observing structure and motion in unstained living cells. By virtue of polarized light source into two coherent parts which are spatially displaced (sheared) at the sample plane, and recombined before observation. The interference of the two parts at recombination is sensitive to their optical path difference, giving the appearance of a three-dimensional physical relief corresponding to produce a contrast variation. Since the optical path differences highly depend on the image contrast, charac- terization of sample refractive distribution and polarization system has got an increasing importance to help us gaining an insight into the mechanisms behind, and furthermore, to use optical image recognition technology. This thesis presents our contribution to the topic of characterization of the gain in image contrast. In the early work, we duplicated a complete waveform of conventional DIC system, and set the adjustable path difference, the polarizer and analyzer device point to provide DIC images with a different orientation for the sample. Because the system setup is compatible to bright field and dark field, it is easy to operate and re-build the DIC optics system from the optical machine. In the next work, we developed display objective lens numerical aperture (Numerical Aperture; NA) function. In the obser- vation, condensing lens' NA value should be equal to or slightly be bigger than objective lens' NA value, we use the objective lens substitution condensing lens to serve this purpose. Because the optical system only uses the objective achievement to take analyzer and the image lenses, As the system has the volume potential extremely, made into a portable differential interference contrast microscopy.