LEMON Photonics creates a one-stop laser light source solution for the intelligent robot industry
As a key core technology to realize industrial automation and intelligence, machine vision is becoming the fastest growing branch of artificial intelligence. Machine vision is to artificial intelligence what the eye is to humans. As one of the most critical parts of machine vision, laser light source directly affects the quality of images and the accuracy of perception, giving machine vision "intelligent light". Machine vision is rapidly expanding into new applications such as consumer electronics, automotive electronics, and industrial control. New applications and new features are driving the need for more power, higher efficiency and smaller footprint of laser light sources.
It is reported that at the China International Optical Expo. (CIOE 2024) held in Shenzhen from September 11th to 13th, LEMON Photonics, located in "Shenzhen Laser Valley", will display a variety of laser light source chips and module products used in machine vision, aiming to create a one-stop laser light source solution for the intelligent robot industry.
LiDAR industry technology is in the early stage of the life cycle, and multi-dimensional and diversified technological innovations are constantly emerging. Product upgrades brought about by technological innovation are the core driving force for the expansion of the machine vision industry. At present, the mainstream mobile navigation technologies mainly include LDS SLAM and VSLAM. LDS SLAM is currently the mainstream technology in the Chinese market. LEMON Photonics provides innovative light sources for three mainstream LDS SLAM systems.
scheme | Stereo vision | Structured light | TOF |
Fundamentals | Binocular matching, triangulation | Laser speckle coding | Reflection jet lag |
application | Locate, navigate, avoid obstacles | Positioning, navigate | Locate, navigate, avoid obstacles |
resolution | middle | high | middle |
precision | middle | high | middle |
Immunity to light interference | high | Low | middle |
cost | middle | middle | high |
Laser source | EEL/VCSEL | VCSEL | EEL/VCSEL/ HCSEL（LEMON Photonics EXCLUSIVE SOLUTION ） |
Table 1: Comparison of three mainstream LDS SLAM solutions
parameters | EEL | VCSEL | HCSEL (Lemon Photonics Exclusive Program） |
Width | 3-8nm FWHM | Narrower，<1nm FWHM | Narrower，<0.3nm FWHM |
Temperature drift | 0.25nm/℃ | Temperature drift ~0.07nm/℃ | Temperature drift ~0.07nm/℃ |
Optical power | High power in a single tube | The single tube power is low, and the array achieves high power | The single tube light surface is enlarged to achieve high power, the same wafer area, and the luminous area duty cycle is higher |
Electro-optical efficiency | >55% | >45% | >45% |
Beam angle | 10 ° x 25 ° | ~20°, symmetrical beam | 0.2°x10°: Approximates singlemode longitudinally along the grating |
Impulse response speed | ns | <0.1ns | <0.1ns |
Packaging and system integration | Optical shaping is complex | Vertical-Cavity Surface-Emitting Laser, simple installation | Excellent beam quality reduces the difficulty of optical shaping and improves the sharpness of the light field |
Relibility | Low | Superior relibility | The large output diameter gives ultra-high chip reliability |
Suitable for production level | The chip is emitted at the edge and the production process is complex | Available in 6" wafers for mass production | The production process is simpler, and the technology of writing gratings in 6" wafer moments has matured, and the production yield is higher |
Cost | High | The structure of the multi-layer vertical cavity is more complex, and the epitaxial thickness is ~10um | Simple epitaxial structure, thickness ~2.5um, simple chip manufacturing process, no oxidation process |
Table 2: Comparison of laser chips (based on 3D and LiDAR applications)
LEMON Photonics launches the industry-leading multi-junction 940nm VCSEL chip series. Among them, the slope efficiency of the five-junction chip is about 4.6W/A, the single-chip power is higher than 50W, and the electro-optical conversion efficiency is >56%. This series of products is characterized by high power density, high reliability and excellent high temperature performance. Suitable for short pulse (NS grade) and high peak power applications. Multi-junction technology represents the next leap forward in the VCSEL industry, bringing many advantages to machine vision applications. High power density reduces package size and optimizes system architecture; High electro-optical conversion efficiency can reduce the thermal load of the whole machine; The high slope efficiency reduces the pulse current, thereby increasing the switching speed of the driver chip.
Figure 1: Measured LIV and PCE data of LEMON photonics multi-junction VCSEL chip
At this exhibition, LEMON Photonics will also display the newly designed VCSEL series point light source and line light source based on its own VCSEL chip. and an ultra-narrow linewidth line light source based on an exclusive, patented horizontal cavity surface emitting laser (HCSEL) chip design.
LEMON Photonics' VCSEL series collimating light source module adopts customized VCSEL single-point chip, which has the advantages of small temperature drift coefficient, high reliability and high cost performance compared with traditional EEL modules.
Figure 2: VCSEL collimation light source for LEMON Photonics facing LDS lidar
The LEMON Photonics VCSEL line projector laser module adopts a custom VCSEL array chip to achieve a high-quality linear light field. Its advantages over conventional EEL ToF light sources are as follows:
M-type light field distribution: M-type light field distribution with strong edge energy is more conducive to large-angle radar to compensate for edge energy; Far-field narrow-edge energy is more concentrated
Small temperature drift coefficient: it is 1/5 of EEL, and a narrowband filter can be used at the receiving end, which can effectively improve the signal-to-noise ratio
Higher reliability: VCSEL light-emitting surface is larger than EEL, with low relative power density and better reliability
Cost-effective: VCSEL provides more optimized costs in chip, packaging, lens and module assembly
Figure 3: VCSEL line laser source for SLAM radar facing LEMON Photonics
LEMON Photonics' HCSEL laser chip combines the advantages of high power output of edge-emitting lasers (EEL) and vertical-cavity surface-emitting lasers (VCSEL) that are more suitable for large-scale mass production, and can simultaneously meet the three major requirements of laser light sources for popular lidar applications: higher peak power, smaller spectral temperature drift, and longer laser bands to achieve longer 3D sensing distance, higher signal-to-noise ratio and eye safety.
Compared with VCSEL and EEL, the advantages of HCSEL chip technology are as follows:
- Ultra-high power, which can achieve hundreds of watts of peak power in a single tube
- Large output caliber gives the chip higher reliability
- Narrow spectral linewidth and stable wavelength for effective noise filtering in 3D sensing and LiDAR applications
- Excellent beam quality, reducing optical shaping difficulty and improving light field utilization
- Excellent polarization for sensing detection and optical beam combination
- The simple chip manufacturing process theoretically guarantees a more controllable cost
The 3D sensing scheme of line scanning has a relatively high degree of program integration and a relatively low cost of more mature line array photoelectric receiver chips, which makes line scan solutions more and more concerned by the sensing industry. Traditional EEL and VCSEL laser chips are difficult to form relatively low-cost, small-volume uniform line spots through diffusers due to their large far-field divergence angles. [Xiao Yan 4] LEMON Photonics' new HCSEL laser chip can greatly improve the sharpness and uniformity of the light field after diffuser shaping with its nearly collimated light divergence angle in one direction, and achieve ideal line spot in a small package size. Figure 5 shows the comparison of the light field effect of 2W VCSEL and HCSEL after passing the same 120 degrees x 1 degree diffuser.
Figure 5: Comparison of the light field of VCSEL and HCSEL chips by 120 degrees x 1 degree diffuser
Figure 6: HCSEL line spot laser projection module based on 4037 package
LEMON Photonics' HCSEL new semiconductor laser chip will take 3D sensing applications to a new level with higher performance, higher reliability and lower cost. At present, lemon photons can provide 2~50W peak power linear spot HCSEL laser projection ToF light source, and many internationally renowned manufacturers have adopted HCSEL chip solutions and are being tested.
