Patent ID: 8045872

Claim:
An image-forming apparatus, comprising: an image-supporting member, an optical sensor that includes a light source unit which applies light having a light-emission main wavelength λ to a peripheral face of the image-supporting member, and a light-receiving unit which receives a reflected light thereof, so as to optically detect a toner pattern formed on a peripheral face of the image-supporting member, wherein the image-supporting member has at least one thin-film layer formed on the peripheral face thereof, and the thickness of an outermost surface thin-film layer is set so as to allow a reflectance function R(d) that indicates the relationship between a reflectance R of the peripheral face of the image-supporting member to light having a light-emission main wavelength λ from the light source unit and a thickness d (nm) of the outermost surface thin-film layer of the image-supporting member to satisfy the following conditional expression: R ( d )≧0.75 ×{R max ( d )− R min ( d )}+ R min ( d ) in which d is set in a range of 0<d<1000 nm; R max (d) is a maximum value that the reflectance function R(d) is allowed to have; and R min (d) is a minimum value that the reflectance function R(d) is allowed to have.