Light detection device including light detector, light coupling layer, and light shielding film, and light detection system including same

A light detection system comprising:

• a light detection device;
• and
• an arithmetic circuit connected to the light detection device, wherein:
• the light detection device includes
• a light detector that has a main surface and includes first detectors and second detectors that are both disposed along the main surface;
• a light coupling layer disposed on or above the light detector, the light coupling layer including
• a first low-refractive-index layer,
• a first high-refractive-index layer that is disposed on the first low-refractive-index layer and includes a first grating, and
• a second low-refractive-index layer that is disposed on the first high-refractive-index layer,
• the first high-refractive-index layer having a higher refractive index than the first low-refractive-index layer and the second low-refractive-index layer;
• and
• a light shielding film that is disposed on the light coupling layer and includes a light transmitting region and a light shielding region adjacent to the light transmitting region,
• the light transmitting region facing two or more first detectors included in the first detectors,
• the light shielding region facing two or more second detectors included in the second detectors, and
• the arithmetic circuit, in operation, outputs at least one signal selected from the group consisting of (1) a first signal indicating a ratio of a second light amount to a first light amount, (2) a second signal indicating a ratio of the first light amount to a sum of the first light amount and the second light amount, and (3) a third signal indicating a ratio of the second light amount to the sum of the first light amount and the second light amount, the first light amount being a sum of light amounts detected by the two or more first detectors, and the second light amount being a sum of light amounts detected by the two or more second detectors.