| 摘要 |
PURPOSE:To make construction simple and manufacture easy by differentiating the arraying spaces of respective photodetectors which detect >=3 luminous fluxes which are given with differences in optical path lengths and are split respectively. CONSTITUTION:The luminous flux L from an objective lens is split to luminous fluxes La, Lb, Lc in three different directions by the diffracting effect of a diffraction grating 24, and are detected in photodetectors 23a, 23b, 23c in respectively different image-forming states by respectively different optical path lengths. Since the photodetectors are disposed at irregular spaces in such a way that the space l1 between the photodetectors 23a and 23b differs from the space l2 between the photodetectors 23b and 23c, the restrictions in designing the optical splitting unit are eased and the differences la, lb, lc in the optical path lengths of the fluxes La, Lb, Lc can be increased without intricating the construction thereof. In other words, the detection of the images differing distinctly in image-forming states in the respective photodetectors 23a, 23b, 23c is made possible. |
