Emitting Lasers Hit the Target for Depth Detection
Modern industrial environments require advanced sensors, hardware, and software for functions such as gesture-based control, movement monitoring, distance measurement, quality control, object identification, product defect detection, safety, and human-robot interaction. Vertical-cavity surface-emitting laser (VCSEL) technology has become a dominant approach for 3D sensing based on time-of-flight (ToF) measurement, offering fast scanning, long operating distances, high efficiency, and excellent resistance to ambient-light interference. In 3D depth detection modules, VCSELs enable wavelength, brightness, size, and beam-angle selection to suit the application.To get more news about
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A ToF-type 3D video camera operates by illuminating the scene with a modulated light source. The sensor detects the reflected light pulses, converts them into electrical signals, and transmits them to the ToF processor, which measures the phase slip between the emitted light and the reflected light, a parameter from which it is able to deduce the distance of the object.
Though they are a relatively new technology, VCSELs are replacing edge-emitting lasers as the reference technology for short-range data communications networks and local networks, offering lower production costs and higher reliability compared with competing approaches.
A VCSEL is composed of layers of semiconductor material grown on an epitaxial substrate via molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD). The wafer is then processed accordingly to produce individual devices.
The laser beam inside a VCSEL is generated between two layers of distributed Bragg reflectors (DBRs) placed parallel to the surface of the wafer at the base of the diode and separated by one or more quantum wells responsible for generating the light beam.
Each DBR mirror is composed of alternating thin layers (each with a thickness of a quarter of the laser wavelength) of materials with high and low refractive indices. This configuration ensures a high reflectance index (about 99%, compared with about 30% for standard lasers) and greater electrical efficiency. As a result, light oscillates perpendicularly to the layers and is emitted from the top or bottom of the device.
VCSELs offer coherent light with direct emission, high power density, and simple packaging. The VCSEL structure is easier to assemble than a comparable edge-emitting laser (EEL). The shape of the radius of a VCSEL is a circular point, versus the elliptical form of Fabry-Perot and digital-feedback EELs. Compared with edge emitters, VCSELs’ simple beam structure considerably reduces the complexity and cost of the coupling/beam-shaping optics and increases the efficiency of coupling to the fiber or another medium. This has been a strong point for VCSEL technology in low-power markets.
