Patent ID: 7623907

Claim:
An endoscope apparatus having an insertable portion for examining an object within a living body using scattered light, said endoscope apparatus comprising: a light source; a first illumination device that directs light from the light source and illuminates the object from the insertable portion of the endoscope apparatus with a first light beam having a center ray and a first wavelength; a second illumination device that directs light from the light source and illuminates the object from the insertable portion of the endoscope apparatus with a second light beam having a center ray and a second wavelength; a detector; a light receiver optical system having a field of view and an optical axis, and that receives light from the first and second illumination devices that has been back-scattered from the object and guides it to the detector; and a processor that calculates a value that corresponds to the size of particles of an object that scatter light; wherein at least two of the first illumination device, the second illumination device, and the light receiver optical system include a positive or negative lens having a lateral offset relative to an optical axis of light that is incident onto the positive or negative lens; the center ray of the first light beam and the center ray of the second light beam intersect the optical axis of the light receiver optical system at substantially the same point; and the first illumination device and the second illumination device are arranged so that the following condition is satisfied α1<α2 where α 1 is the angle formed by the optical axis of the light receiver optical system and the center ray of the first light beam, which is defined as a line that is included in the first light beam and is substantially in the center of the bundle of rays that are emitted from the first illumination device and intersect at a point where the optical axis of the light receiver optical system intersects the surface of an object; and α 2 is the angle formed by the optical axis of the light receiver optical system and the center ray of the second light beam, which is defined as a line that is included in the second light beam and is substantially in the center of the bundle of rays that are emitted from the second illumination device and intersect at a point where the optical axis of the light receiver optical system intersects the surface of an object.