1. A solid-state imaging device comprising: an imaging device comprising an imaging area including a plurality of pixel blocks each of which includes a plurality of pixels; an image formation lens forming an image on an image formation plane by using light from a subject; an aperture unit including a plurality of aperture elements provided to associate with the plurality of pixel blocks, each of the aperture elements having an aperture portion and a shield portion, light from the image formation lens being filtered by each aperture element; a microlens array including a plurality of microlenses provided to associate with the plurality of aperture elements, each of the microlenses forming an image in the imaging area by using light filtered by an associated aperture element; and a signal processing circuit configured to process a signal of an image taken in the imaging area and estimates a distance to the subject.