Illumination optical system, and spectrophotometric apparatus and image forming apparatus including the same

A spectrophotometric apparatus, comprising:

• an illumination optical system configured to illuminate an illuminated surface;
• and
• a spectral optical system configured to disperse scattered light from an object arranged on the illuminated surface to form an image of the object on a light receiving element,
• the illumination optical system comprising:
• a light source;
• and
• a light guiding member configured to guide a light flux emitted from the light source to the illuminated surface,
• the light guiding member having:
• an incident surface into which the light flux from the light source enters;
• an ellipsoidal reflection surface configured to reflect the light flux from the incident surface;
• and
• an exit surface from which the light flux reflected by the ellipsoidal reflection surface exits,
• wherein the light source is arranged so as to be separated from a first focal point of the ellipsoidal reflection surface at a position farther from the illuminated surface, in a direction perpendicular to a light emitting surface of the light source.

An image forming apparatus, comprising:

• a spectrophotometric apparatus;
• developing units configured to develop, as toner images, electrostatic latent images formed on photosensitive surfaces of a plurality of photosensitive bodies, respectively;
• transfer units configured to transfer the developed toner images onto a transfer material;
• and
• a fixing unit configured to fix the transferred toner images to the transfer material,
• the spectrophotometric apparatus comprising:
• an illumination optical system configured to illuminate an illuminated surface;
• and
• a spectral optical system configured to disperse scattered light from an object arranged on the illuminated surface to form an image of the object on a light receiving element,
• the illumination optical system comprising:
• a light source;
• and
• a light guiding member configured to guide a light flux emitted from the light source to the illuminated surface,
• the light guiding member having:
• an incident surface into which the light flux from the light source enters;
• an ellipsoidal reflection surface configured to reflect the light flux from the incident surface;
• and
• an exit surface from which the light flux reflected by the ellipsoidal reflection surface exits,
• wherein the light source is arranged so as to be separated from a first focal point of the ellipsoidal reflection surface at a position farther from the illuminated surface, in a direction perpendicular to a light emitting surface of the light source.