Light quantity measuring device and method for measuring light quantity that selectively connects light reception elements based on incident light angle

A light quantity measuring device comprising:

• a first light reception element that receives a predetermined incident light at a first light reception surface;
• a second light reception element that receives the incident light at a second light reception surface, which is oriented in the same direction as the first light reception surface;
• an identification circuit that identifies an incident angle of the incident light with respect to the first light reception surface;
• and
• a selection circuit that, when the incident light angle differs from a desired incident angle, selectively electrically connects an output portion of the second light reception element to an output portion of the first light reception element,
• wherein a plurality of the second light reception elements are provided, and the respective light reception surfaces thereof have different areas, and
• wherein the selection circuit selectively electrically connects the output portions of the second light reception elements with the output portion of the first light reception element, so as to compensate for a reduction in a received light quantity due to the incident light differing from the desired incident angle, via switching elements that, individually and in parallel, switch between connecting or not connecting at least one of the plurality of second light reception elements to the first light reception element.