A method for acquiring light information of an image using a device for detecting a light distribution for a predetermined purpose on the basis of unit signals, the device including, as unit components of a unit pixel matrix comprising a solid-state image sensor having a photodiode formed in a semiconductor substrate, a respective detecting part (12R, 12G, 12B, 12IR) for detecting an electromagnetic wave and a respective unit signal generating part (205R, 205G, 205B, 205IR) comprising an amplification semiconductor element for generating a corresponding unit signal on the basis of the quantity of the electromagnetic wave detected by the respective detecting part (12R, 12G, 12B, 12IR) and outputting the unit signal, and the unit components (12R, 12G, 12B, 12IR, 205R, 205G, 205B, 205IR) being disposed on the same semiconductor substrate in a predetermined order; each detecting part (12R, 12G, 12B) having the characteristic that a predetermined wavelength region component of the electromagnetic wave is reflected, and the remainder is transmitted; includes a stacked member having a structure in which a plurality of dielectric layers (L_1,...,L_5) having different refractive indexes between the adjacent ones and each a predetermined thickness is stacked, the stacked member being provided on the incident surface side to which the electromagnetic wave is incident; the transmitted wavelength region component transmitted through the stacked member is detected by the respective detecting part (12R, 12G, 12B), and the light information of an image for a predetermined purpose is acquired on the basis of the unit signal of the transmitted wavelength region component obtained from the respective unit signal generating part (205R, 205G, 205B); characterized in that the stacked member is not provided on the incident surface side to which the electromagnetic wave is incident in a detecting part other than the detecting part (12R, 12G, 12B) for the transmitted wavelength region component so that the reflected wavelength region component is detected by the other detecting part, thereby obtaining light information of an image for a second predetermined purpose on the basis of a unit signal of the reflected wavelength region component obtained from the corresponding unit signal generating part; one of first light information based on the unit signal of the transmitted wavelength region component and second light information based on the unit signal of the reflected wavelength region component is selected and output, or both are simultaneously output; and optical members (14B, 14G, 14R) are provided only on the respective incident surface sides of a plurality of detecting parts (12B, 12G, 12R) for detecting the transmitted wavelength region component, for separating the transmitted wavelength region component into different wavelength region components; wherein the respective transmitted wavelength region components are detected by the plurality of detecting parts (12B, 12G, 12R), respectively, and other light information on the transmitted wavelength region component is acquired by combining the unit signals of the respective transmitted wavelength region components, which are obtained from the unit signal generating part.