Color image formation apparatus with density measurement

Claim 1

An image formation apparatus for forming a color image comprising: an image combining member for overlapping a plurality of different mono-color images formed by an electrophotographic process with a plurality of respective different colorants to form said color image thereon; density measuring means for measuring a reflective density at a desired portion of said color image, said density measuring means including light emitting means for emitting light toward said image combining member and photoelectric conversion means for receiving and photoelectrically-converting said light reflected at said image combining member to a density signal, wherein said plurality of colorants are divided into first and second groups, said first group of said plurality of different colorants having a higher reflectivity than said image combining member with respect to said light, a second group of said plurality of different colorants having a lower reflectivity than said image combining member; and switching means for causing said light emitting means to change an intensity of said light in response to an intensity control signal, wherein said switching means comprises first reference signal generation means for generating a first reference signal, a second reference signal generation means for generating a second reference signal, and a switch responsive to said intensity control signal for selecting either of said first and second reference signals, and wherein said light emitting means changes said intensity of said light in accordance with an output of said switch.