1. A method of standardized image generation comprising the steps of: irradiating living tissue with light; detecting images of mutually different wavelength bandwidths based on reradiated light generated from said living tissue by said irradiation with said light with an image detection means; adding a desired offset to at least one of said images of mutually different wavelength bandwidths; and generating a standardized image based on the ratio of said images of mutually different wavelength bandwidths, at least one of which a desired offset has been added to; wherein a predetermined correction function is employed for performing a distance correction on said standardized image, which corrects for the amount of fluctuation of said standardized image caused by the distance between said living tissue and said image detection means, thereby generating a corrected standardized image.