Patent ID: 6989849

Claim:
An exposure head comprising: a plurality of light emitting parts which are formed into an array configuration such that the light emitting parts are aligned in lines in the main scanning direction on a transparent substrate, the exposure head projecting modulated light beams from said light emitting parts to an image carrier so as to form a predetermined pattern on said image carrier, the light beams from said light emitting parts being projected on said image carrier side through said transparent substrate, wherein: said transparent substrate has plane faces substantially parallel to each other, one of the faces being a face on which the light emitting parts are formed and the other being a face from which light beams are projected, said transparent substrate is provided with a single light quantity detecting means for detecting the quantity of light emitted from said light emitting parts, at one or more positions other than the face on which the light emitting parts are formed and other than the face from which light beams are projected, said light emitting parts are light emitting parts of organic EL light emitting elements, and said single light quantity detecting means is disposed on one of the end faces in the main scanning direction of said transparent substrate and said single light quantity detecting means detects the quantity of light emitted from a plurality of said light emitting parts.