An image generation method, image generation device, and image synthesis device include generating at least two images at different exposure times. Intensities of pixels in the images at different exposure times are respectively obtained. Reliabilities of the pixels in the images at different exposure times are respectively obtained. The intensities of the corresponding pixels in the images at different exposure times are respectively multiplied by the corresponding reliabilities, and then the products are summed, so as to obtain intensities of pixels in a synthesized image and thus generate the synthesized image. By using the technical schemes of the present disclosure, an image with abundant details can be generated in real time.