Laser Sensor

Description

Working Principle

A laser sensor consists of two modules: an emitter that uses a diode to emit laser light, and a receiver that uses a photoresistor to detect the laser.

The basic structure of a laser diode is similar to that of a regular diode, both composed of a P-N junction formed from semiconductor materials. When an external electric field is applied to the laser diode, electrons transition from the higher energy level of the n-region to the lower energy level of the p-region, releasing energy-carrying photons in the process. Unlike a regular diode, the laser diode has two parallel optical reflective surfaces that form an optical resonant cavity. This cavity allows the generated light to bounce back and forth between the reflective surfaces, stimulating the emission of more photons. Through repeated propagation, reflection, and amplification, the photons ultimately form a highly focused, monochromatic, and coherent laser beam.

A photoresistor is a semiconductor component whose resistance varies with the intensity of light. When light shines on the photoresistor, the energy of the photons excites electrons within the semiconductor, causing its resistance to decrease significantly. By measuring changes in resistance, it is possible to determine whether a light signal has been received. Photoresistors can be designed to be sensitive to specific wavelengths of light, allowing them to focus on detecting laser light while being less affected by ambient light.

The emitter and receiver work together to detect whether an object is present in the path of the laser beam. The receiver is positioned along the expected path of the laser, while the emitter generates a straight laser beam when powered on, aiming directly at the receiver. If there is an obstacle in the laser’s path, the beam is blocked and cannot reach the receiver directly. This causes a change in the resistance of the photoresistor, which is then detected by the receiver.