A position-sensitive detector (PSD) operates similarly to a standard photodiode, where an incident laser beam generates a photocurrent that moves toward the p- and n-type regions. However, unlike conventional photodiodes, a PSD features multiple electrical contacts. This design causes the photocurrent to be distributed among the contacts based on the laser spot’s location.
Position Determination
The position is derived from the current difference between two opposing contacts. When the total current is normalized, the position signal becomes independent of the laser’s intensity. Unlike charge-coupled devices (CCDs), a PSD is not limited by pixel size and does not require extensive computational analysis. In contrast, segmented detectors such as differential and quadrant detectors can only measure distances up to the beam diameter.
Benefits
A PSD is well-suited for measuring larger distances across its entire active surface. The laser spot’s shape, size, and intensity distribution have minimal impact on its functionality. The position is determined by the power center of the laser spot, making the system more adaptable to various conditions.
