A collimator optical system collimates light from the coherent light source. A reflection type spatial light modulator returns collimated light from the collimator optical system to the collimator optical system. A Fourier transformation optical system Fourier-transforms light from the reflection type spatial light modulator and shares at least partial optical system with the collimator optical system. An emission light from another coherent light source passes through an incident light path composed of another collimator optical system, spatial modulator and polarized beam splitter in this order and reaches the reflection type spatial light modulator. Then, a reflection light from the reflection type spatial light modulator passes through a reflection light path which is reverse to the incident light path and reaches a polarized beam splitter. That is, the incident light path and reflection light path are split by the polarized beam splitter. Then, a shared optical system which is at least part of Fourier transformation optical system for the incident light and further at least part of reversed Fourier transformation optical system for the reflection light is disposed in optical path between the polarized beam splitter and reflection type spatial light modulator.