To dispense with a high manufacturing precision or assembling precision and eliminate a movable part by integrating and microminiaturize a spectral filter, a microlens and a photo detector.

Spectral filters 9-12, microlenses 13a-13d and photo detectors 14a-14d are integrated and microminiaturized, or arrayed. Since an incident light 100 is transmitted by the spectral filters 9-12 having different wavelength selective characteristics, the lights transmitted by the spectral filters 9-12 form selected wavelength components. The transmitted lights are converged by the microlenses 13a-13d, and incident on the photo detectors 14a-14d. The output signals 101a-101d detected and outputted by the photo detectors 14a-14d form light intensity signals corresponding to the wavelengths selected by the spectral filters 9-12, respectively. Thus, the light intensity signals corresponding to the respective selected wavelengths are collectively processed, whereby a spectral pattern can be provided.