<p>PURPOSE:To permit the easy inserting and mounting of an optical imaging device to a printer engine by providing a means of changing an optical path between an integrating cylinder which decreases the uneven quantity of the light of a light source and a fiber bundle. CONSTITUTION:The spot light source 11 consisting of a halogen lamp irradiates the integrating cylinder 12. Average illuminance is high on the photodetecting surface of the integrating cylinder but the quantity of the light is extremely uneven on said surface. A heat-proof diffusion lens 13 is disposed to decrease the uneven quantity of light and to shut off heat rays so that the uneven quantity of the light is decreased by said lens coupled with the effect by the multiple reflections of the cylindrical mirror on the inside surface of the cylinder 12. The exit light from the cylinder 12 is made incident to the fiber bundle 16. The optical path thereof is bent 90 deg. between the integrating means 12 and the bundle 16 and a prism 21 having the critical reflection face at the incident face and exit face of the light bending part and having 45 deg. total reflection characteristic is used in order to prevent the dissipation of the light arising therefrom. The light emitted from an elliptical mirror 18 through a linear light distributing part 17 passes through a liquid crystal light valve 19 and is irradiated on the photosensitive device by passing through a convergent fiber lens 20. The inserting and mounting of the imaging device to the engine are thus made easy and the device is mader smaller in size.</p>
