The Application Advantages and Principle Analysis of VCSEL Technology in 3D Reconstruction

1. What is VCSEL?

VCSEL (Vertical-Cavity Surface-Emitting Laser), vertical cavity surface emitting laser (also translated as vertical resonant cavity surface emitting laser), is a new type of optoelectronic semiconductor laser, whose laser is emitted perpendicularly from the top surface, making it a type of f-p laser with light emission directed perpendicularly to the resonant cavity surface. Unlike the edge-emitting laser, which is generally made by cutting independent chips and emitting lasers from the edge, this type of laser has a fast modulation function and can obtain stable, continuous, high-quality lasers with a certain power. Since Professor Ken Iga of Tokyo Institute of Technology first proposed the concept of VCSEL in 1977, this technology has been widely used in optical communications and other fields, and has matured after more than 40 years of development.

In the field of 3D scanning, VCSEL technology has greatly enhanced scanning performance. For instance, iReal 3D scanners employ infrared VCSEL technology for speckle surface scanning.  The iReal M3 3D scanner is equipped with an infrared VCSEL as one of its light sources, while the iReal 2E scanner 3D uses three infrared VCSELs for speckle surface scanning.

2. What is the principle of VCSEL projecting infrared speckle code for 3D Reconstruction?

VCSEL technology plays a critical role in 3D reconstruction, primarily through the projection of infrared speckle codes. Here are the core principles behind this process:

(1) Projecting speckle code: Using the infrared laser emitted by VCSEL, a speckle code pattern is projected through a special optical system.

(2) Optical imaging: After the speckle code pattern is irradiated onto the surface of an object, it is scattered and the camera captures the image formed by the scattered light.

(3) Image matching: Match the captured speckle image with the original speckle code, and extract the 3D information of the object surface through correlation calculation.

(4) 3D reconstruction: Based on the matching results, the distance between each point on the object surface and the camera is calculated using the triangulation principle, thereby achieving accurate 3D reconstruction.

3. What are the advantages of VCSEL for 3D reconstruction compared with LED projected speckle codes?

In the process of 3D reconstruction using projected speckle codes, VCSEL (vertical cavity surface emitting laser) has the following significant advantages compared with LED light sources:

(1) High coherence: The high coherence light source provided by VCSEL can produce clearer speckle patterns, thereby achieving higher measurement accuracy in 3D reconstruction, especially in capturing object details.

(2) Anti-ambient light interference: The wavelength characteristics of infrared VCSEL make it less susceptible to interference in strong light environments, ensuring the stability and reliability of 3D reconstruction. In addition, since infrared is invisible light, VCSEL can achieve lightless scanning, especially when scanning sensitive occasions such as the human body scan, providing a more friendly and interference-free scanning experience.

Both iReal M3 and iReal 2E support outdoor 3D scanning, demonstrating their adaptability under different lighting conditions.

(3) Wide applicability: VCSEL is suitable for a variety of surfaces with different characteristics, including black or highly reflective materials, making 3D reconstruction technology more flexible and universal. The material adaptability of iReal M3 and iReal 2E means that they can scan black, shiny, reflective objects (such as 3d scan car mats), and in most cases do not require powder spraying.

(4) Low power consumption: VCSEL has relatively low power consumption, which makes it suitable for portable devices and applications that require long-term operation, such as real-time 3D scanning. The scanning speed of iReal M3 can reach up to 60 frames per second, while that of iReal 2E is 15 frames per second, both demonstrating the advantage of VCSEL in scanning speed.

(5) Temperature stability: VCSEL has high performance stability under temperature changes, ensuring the accuracy of 3D reconstruction under different environmental conditions.

Specifically, VCSEL has been significantly applied in the fields of 3D facial recognition in smartphones and object detection in autonomous driving systems. For example, the efficiency of VCSEL can reach more than 30%, which is much higher than the efficiency of LED, which enables VCSEL to provide a more stable light source in 3D reconstruction. The lightless scanning characteristics of infrared VCSEL are particularly important in outdoor applications or occasions that require concealed operation. It not only reduces the interference of ambient light, but also improves the safety and comfort of the scanning process.

In summary, the unique structure, principle, and application advantages of VCSELs in 3D reconstruction highlight their significant role and promising future in the field of modern optoelectronics.