Patent ID: 7265773

Claim:
An image detection device comprising: a light source configured to irradiate a pattern image with a light beam; an image sensor; a light guiding device located on a first light path from the light source to the pattern image and configured to guide the light beam irradiated by the light source to the pattern image and further guide a light reflected from the pattern image to the image sensor along a second light path, the first light path including only the light guiding device and not including any image focusing device; an image focusing device located on the second light path from the light guiding device to the image sensor and configured to focus the light reflected from the pattern image on the image sensor; and a housing configured to contain the light source, the image sensor, the light guiding device and the image focusing device, wherein an optical axis of the light reflected from the pattern image coincides with an optical axis of the image focusing device, and a bottom surface of a prism in the light guiding device and a surface on which the pattern image is formed make a first angle that is half of a second angle made by a plane perpendicular to the bottom surface of the prism and the first light path from the bottom surface to the pattern image.