MONOCHROMATOR

PURPOSE:To simplify the constitution of a device, by making an incident angle into a diffraction grating at a recess surface, where ruled lines are formed at a specified interval, equal to a diffraction angle, and arranging an incident slit and a reflecting slit respectively on one straight line, which is in parallel with the ruled lines. CONSTITUTION:An original point 0 of coordinates is provided at the center of a diffraction grating 20 of a recess surface having an unequal interval. An (x) axis is provided in the normal direction, a (y) axis is provided in the vertical direction with respect to a groove and a (z) axis is provided in the parallel direction with respect to the groove. An incident slit 2 and an output slit 3 are arranged in parallel with the (z) axis in the up and down direction. A light beam from the incident slit 2 is diffracted through the diffraction grating 20 of a recess surface having an equal interval and taken out as monochromatic light through the output slit 3. The wavelength is selected only by rotary motion 10 around the (z) axis. Since the incident slit 2 and the output slit 3 can be aligned in the vertical direction and the wavelengths can be scanned only by the rotation of the diffraction grating 20, the device can be made compact.