Optical image measurement apparatus and optical attenuator

An optical image measurement apparatus comprising:

• an optical system that splits low-coherence light into signal light and reference light, generates and detects interference light by superposing the signal light that has passed through a signal optical path toward a measured object and the reference light that has passed through a reference optical path;
• and
• an image-forming part that forms an image of the measured object based on the detection result of the interference light;
• the optical image measurement apparatus comprising:
• an optical attenuator that is respectively provided in at least one subject optical path of an optical path of the low-coherence light, the signal optical path, the reference optical path, and an optical path of the interference light, and capable of shielding subject light traveling in the subject optical path;
• the optical attenuator comprising:
• a stepping motor,
• a cam that has a cam surface shaped depending on the distribution of the light amount in the cross-section of the subject light, and that is rotated by the stepping motor;
• a shielding mechanism including an abutment that abuts the cam face, an axis of rotation provided at a predefined distance away from the abutment, and a first shield that is provided at a predefined distance away from the axis of rotation and capable of shielding the subject light from a first direction;
• and
• a second shield that is capable of shielding the subject light from a second direction different from the first direction;
• wherein, in response to the rotation of the cam by the stepping motor:
• the abutment moves following the displacement of the cam face with the rotation of the cam;
• the shielding mechanism rotates about the axis of rotation with the movement of the abutment;
• the first shield moves in the first direction with the rotation of the shielding mechanism to change the shielding region of the subject light;
• the optical system detects the interference light based on the subject light, part of which is shielded by the first shield and the second shield;
• and
• the image-forming part forms an image of the measured object based on the detection result of this interference light.