VCSEL for Sensing
On October 26, 2018, Huawei MATE20 was released at the Shanghai Deductive Center. Its configuration and performance caused a strong sensation in the mobile phone market. On the hardware side, Huawei MATE20 is equipped with a 3D depth-sensing camera that has become the focus of attention. This is an RGB-D (RGB + Depth) depth camera based on a structured light scheme. As shown in the figure below, this can be considered a smaller version of Kinect.
The traditional 2D camera can only obtain two-dimensional plane information of the object. However, the 3D camera can acquire three-dimensional information of the object, thereby giving the face recognition function of the mobile phone camera to realize device unlocking and mobile payment. In addition, 3D cameras will also play a major role in 3D modeling, human-computer interaction and AR/VR. Compared with traditional 2D cameras, 3D cameras mainly include infrared light sources and infrared sensors. Among this, the most critical part is the infrared light source.
There are three main types of 3D depth cameras: binocular stereo imaging, structured light and ToF. The binocular stereo imaging scheme uses a dual camera to capture an object information and then calculates the object distance based on the triangle principle. The structured light scheme projects specific optical information onto the surface of the object, and then is collected by the camera to calculate the position and depth information of the object based on the change of the optical signal caused by the object. The TOF acquires object depth information by calculating the time of flight of the near-infrared light from transmission to reception. All three options have their own advantages and disadvantages. At present, structured light is the most widely used in front-facing cameras, and ToF may be widely used in rear-facing cameras in the future.
2. Augmented reality
Augmented reality is a technique that superimposes real environments and virtual objects onto the same picture or space in real time. The AR technology simulates and models the information that is difficult to experience in the real world, such as vision, sound, taste, and touch, and then superimpose on the real world through computer and other scientific techniques. Then, it is perceived by human senses to achieve a sensory experience that transcends reality.
Micro-projection imaging and 3D imaging are the two core technologies of the AR industry. Semiconductor laser diodes, especially VCSELs, will become the most basic components of the AR industry and become the leader in the era of consumer electronics. With the development of projection display technology, people demand a higher quality of the brightness, resolution and color richness of the projection system. As a important component of the projection system, the light source will directly determine the quality of the projection system. The light emitted by the VCSEL has the characteristics of monochromatic, stable, uniform chromaticity and illuminance, and high brightness. These features are not available in traditional light sources. The replacement of LEDs by VCSELs as a light source for miniature projection modules, projectors, projection televisions, etc., has become a trend.
Compared with ordinary microwave radar, lidar uses laser beam. The laser diode is a very important part of the lidar, which can emit a laser beam to detect the position and velocity of the target. Its working frequency is much higher than microwave, so it gives lidar many advantages, such as high resolution, good concealment, strong anti-interference ability, excellent low-altitude detection performance, small size, light weight. Compared with LED and EEL, VCSELs have considerable advantages in terms of performance and cost. Therefore, lidar equipped with VCSEL will show significant applications in the following fields.
In the field of drones, lidar equipped with VCSELs can realize drone altitude holding, terrain simulation flying, landing. Lidar can also give the vehicle many functions, such as forward and backward collision avoidance, automatic obstacle avoidance, and automatic driving. Lidar can assist the robot to automatically acquire the environmental information of the three-dimensional space, construct the map in a complex environment, and move autonomously in the environment. In addition, lidar can also be used for AGV collision avoidance, intelligent transportation, automatic toll booths and more.
4. Security surveillance
The traditional security surveillance camera has a relatively close monitoring range and cannot clearly distinguish the target in the case of dim light. However, if the camera is equipped with the VCSEL, the laser camera can easily monitor a range of a few hundred meters at night due to the excellent penetration of the laser in low visibility environments. The advantages of the security surveillance camera with VCSEL are very obvious. The VCSEL has high energy conversion efficiency, low waste heat, and relatively small driving voltage and current required. This greatly reduces the heat dissipation burden of the camera, so its life can be drastically prolonged and its performance stability can be significantly improved. In addition, since the infrared light emitted by the VCSEL is invisible, and the VCSEL is very small in size, this fundamentally improves the concealment of the camera, making it widely used in special environments.
The laser camera can also obtain the depth information of the target, making it more powerful in the field of security monitoring. 2D Color image showing frontal view of life sized flat mannequins stacked one behind the other creating an “Optical Illusion”. Depth Image solves the “Optical Illusion” , and tells us how many images, their position in space, ie. distance from camera.
Can you see how many objects are in the image? Depth Image can tells us how many objeccs and their distance from the camera.