| 摘要 |
Disclosed is a device for splitting incident light on an image forming optical system by means of a relief type diffraction lattice and for detecting a portion of the light. The device is constructed with a transparent substrate, on one surface of which there is formed the relief type diffraction lattice which satisfies the condition of N lambda &persp& 2n DELTA (where N is an integer; lambda is a wavelength contained in the incident light; n denotes a refractive index of the transparent substrate; and DELTA represents a quantity between peak and valley on the surface of the relief type diffraction lattice), a reflective film coated on the lattice surface, a transparent filling layer having the substantially same refractive index as that of the transparent substrate, which perfectly fills the peak and valley (or surface irregularity) of the relief type diffraction lattice, and light detectors. With this construction, the incident light is split by diffraction without undesirably effecting the image-formation, and the thus diffracted light is detected by the light detectors. |
