An image pickup system with an illuminating device capable of sequentially irradiating three kinds of color lights different from each other onto an object, an objective lens system forming images of the object with the color lights, a solid-state image sensor receiving the images of the object, a signal processing device producing individual color images of the object based on electric signals supplied from the solid-state image sensor, and a color dispersion device or a color separation device disposed in an optical path of light incident on the solid-state image sensor from the object. The color dispersion device includes the combination of variously shaped prisms and a diffraction grating, and the color separation device includes a structure compounded of dichroic mirrors, whereby the images with respective color lights are incident at positions shifted each other on the solid-state image sensor. The compound of signals indicative of individual color images makes it possible to bring about the object image with high resolution.