Optical device

An optical device comprising:

• a light source configured to project illumination light toward a sensing region;
• a photodetector configured to receive reflected light of the illumination light reflected on the sensing region;
• and
• a condenser mirror configured to condense the reflected light on the photodetector, wherein
• the condenser mirror has
• a through hole through which the illumination light emitted from the light source passes,
• a reflection surface having a shape obtained by cutting out a columnar body extending along an optical axis of the light source, with a spheroid whose rotation axis is a major axis, such that the condenser mirror has a first focal position and a second focal position different from the first focal position along the major axis of the spheroid, and
• a first optical axis extending from the reflection surface toward the first focal position and a second optical axis, aligned with the optical axis of the light source, extending from the reflection surface toward the second focal position,
• the photodetector is disposed on the first optical axis, and
• the sensing region is set on the second optical axis.