What is the difference between tetra-lateral and duo-lateral structure position sensing detectors?
Both tetra-lateral and duo-lateral position sensing detectors are both types of devices used to determine the position of a light spot on their surface.
Tetra-lateral position sensing detectors, also known as quad-cell or four-quadrant detectors, have four separate photodiodes arranged in a square or rectangular pattern. These photodiodes capture the light intensity distribution and generate signals proportional to the position of the incident light spot in both the horizontal and vertical directions. The photocurrent is divided in two or four parts for one or two-dimensional sensing respectively. They show smaller dark currents and faster response times compared to duo-lateral PSDs. By comparing the output signals from the four photodiodes, the position of the light spot can be precisely determined.
Duo-lateral position sensing detectors, also known as bi-cell or two-quadrant detectors, have two photodiodes arranged in a linear pattern. These photodiodes capture the light intensity distribution and generate signals proportional to the position of the incident light spot along a single axis, typically the horizontal axis. The position of the light spot can be determined along that axis b comparing the output signals from the two photodiodes. They exhibit excellent position linearity over the entire active area.