INTERFERENCE APPARATUS

PURPOSE:To enable measurement of coherence of light with single observation, by arranging a plurality of optical delay paths varied in the optical path length in one of two split optical paths of a Michelson's interferometer. CONSTITUTION:Light 1 generated with a single phenomenon of a light source or light is turned with a collimation lens 2 into a parallel luminous flux and the light divided in two with a half mirror 3 and reflected is reflected 4 in the original direction and transmitted through the half mirror 3 to reach a 1-D or 2-D detector 7, when a wave front 9 thereof becomes planar. The beam transmitted through the half mirror 3 out of the two split 3 beams is transmitted through and reflected 5 with an echelon 8, again, reaches the echelon 8 and the half mirror 3 and reflected to reach the detector 7. At this point, the wave front 10 shows a form of a staircase. The two wave fronts 9 and 10 interfere 7 with each other to form an interference fringe with the sharpness thereof varying corresponding to the coherence of the light 1. As the optical path length in steps of the echelon 8 is known, the coherence of the light can be detected by determining the sharpness of the interference fringe corresponding to the steps.