Main uses of semiconductor lasers

Optical communication technology is widely used in information and communication infrastructure, including the Internet. It achieves long-distance data transmission by using high-power laser light sources capable of high-speed modulation and optical fibers.

They are used as light sources for reading and writing to OPTICAL DISKS disc media such as CDs, DVDs, and BDs. The shorter the wavelength of light, the smaller the focused spot size, leading to larger capacity recording information. CDs use semiconductor lasers that emit light at wavelengths of 780 nm, DVDs at 650 nm, and BDs at 405 nm.

Taking advantage of the laser's high focusing and directivity, it is used as the light source for laser pointers and corner alignment devices used on construction sites, etc. Green lasers are often used outdoors as they have good visibility.

3D sensing technology using infrared lasers is attracting attention and is being widely used as a light source for facial recognition and object detection. Specific examples will be discussed later.

The stereo camera method is a widely known 3D sensing technology.
This is a method of measuring distance by capturing images of an object using two cameras, then creating disparity information from the misalignment between the images, just like the human eye. When using at night or in dark places, infrared lighting may be used to illuminate the object. 3D sensing can be achieved relatively easily by using a dedicated stereo camera, but this can be costly. Accuracy may also decrease in environments where it is difficult to obtain disparity information from images (fog, rain, etc.). LEDs are the mainstream lighting source, but some configurations use semiconductor lasers as an auxiliary to improve detection accuracy.

It uses an infrared laser to calculate distance based on the speed of light. It measures the time it takes for the infrared light it emits to reflect off an object and return to the sensor. A dedicated high-speed measurement circuit is required to convert the speed of light into distance.
There are two types of ToF: 1D-ToF, which measures the distance to an arbitrary point, and 3D-ToF, which diffuses the illuminated area to obtain distance information over a wide range. In particular, the latter, 3D-ToF, can detect objects hundreds of meters away due to the increased power of the infrared laser light source, and is mainly used in LiDAR, which is used in autonomous driving cars.

This method uses a light source that projects a special pattern to obtain parallax information and calculate the distance to the target object. It consists of one camera and a projector light source that projects a special pattern, and projects the special pattern onto the target to generate parallax information, which is then converted into distance information. Recently, dot projector products have been released that take advantage of the high density of the light-emitting part, a feature of VCSEL, and emit special dot patterns for the Structured Light method.
In this case, a reference calibration image is prepared in advance, and the calibration image is compared with the image each time a special pattern is projected onto the target object. This allows parallax information to be calculated from the pattern misalignment and converted into distance. Distance calculations are performed based on a dot pattern consisting of thousands to tens of thousands of dots, enabling high-resolution 3D sensing.