The different types of laser sensors include charge-coupled devices (CCD), complimentary metal oxide semiconductors (CMOS), position-sensitive detectors (PSD), and photoelectric sensors. Depending on the requirements of a particular application, one or more laser sensors might operate simultaneously within a piece of equipment. All but the photoelectric laser sensors function by triangulated signal reception. A laser diode emits a beam of light toward an object. The beam diffuses and reflects back to the sensor, which interprets the data and provides the required information.
CCD sensors contain millions of tiny cells that convert received light into electrons. These charges then cross a chip that interprets the data. The CCD sensors produce high quality and low noise images, without regard to color, texture or quantity of light. Manufacturers frequently combine CCD sensors with PSD technology for image reproduction. CCD sensors are usually more expensive and require more electricity than other sensor types.
CMOS sensors also contain millions of cells or pixels, which convert light into energy, but the wiring and transistors within the sensor are constructed so that data from each cell can be obtained individually without the need to transfer energy over a chip. CMOS sensors operate at close or long-distance ranges, regardless of light intensity or reflectivity. This type of sensor is more susceptible to noise than a CMOS sensor and may not produce as clear an image. A CMOS might be combined with a CCD sensor, forming a laser displacement sensor that is commonly used in industrial laser measurement.
PSD sensors can locate a beam of light in one or two dimensions. For example, when the sensor surface receives the signal, the position might be determined both horizontally and vertically. This type of laser sensor is generally suitable for use in both short and long range applications. The technology is often employed by the military, as the laser sensor accurately detects motion, position, and vibration.
A photoelectric laser emits an infrared or visible beam of light aimed at and received by an opposing photoelectric sensor detector. These laser sensors are usually designed to detect the absence or presence of objects. When the light beam traveling to the sensor is disrupted, the laser sensor relays a signal, and the equipment performs a specific function. Photoelectric lasers might be used to count the items being transported along a conveyor belt or to provide a barrier as part of a security system.
The sensitivity of photoelectric sensors varies, but some are quite sensitive. Certain models are capable of detecting objects at close range that measure no more than 0.40 inches (1 mm) in diameter. The length of the beam transmitted also varies, with some units able to transmit up to 197 feet (60 m).
