1. An imaging-observation apparatus comprising: an image capturing section configured to shoot a subject under multiple different shooting optical conditions at the same time and sequentially generate a plurality of images under those multiple different shooting optical conditions; a display control section configured to accept an operator's input; an image synthesizing section configured to synthesize together the plurality of images in accordance with the input to the display control section at a synthesis ratio specified by the input and to sequentially generate synthetic images one after another; a display section configured to present the synthetic images; and a polarized light source that emits mostly polarized light with a predetermined polarization direction, wherein the subject is irradiated with the polarized light, wherein the image capturing section includes: a stop; an image capturing optical system; an image sensor with multiple groups of pixels, each said group of pixels being made up of a plurality of pixels; an area-divided optical element which is arranged in the vicinity of the stop and which has at least two optical regions, through which light beams are transmitted with mutually different optical properties; and an array of optical elements which is arranged between the image capturing optical system and the image sensor and which makes the light beams that have been transmitted through the predetermined optical regions of the area-divided optical element incident on mutually different groups of pixels of the image sensor, and wherein the plurality of images are generated from the multiple groups of pixels.