We have been developing new biomedical optical-measurement techniques similar to optical biopsy based on opto-electronics and laser engineering. In particular, optical coherence tomography (OCT) is a promising clinical diagnostic technique, because it can provide clear in vivo tomographic images with a spatial resolution of 10 µm at a depth of a few millimeters beneath the skin surface. Our present research is directed at not only the analysis of the physiology of skin sweat glands and peripheral vessels, but also in vivo observation of allergic dermatitis by OCT imaging. Furthermore, we have developed novel OCT techniques using an electro-optic crystal.