Vehicle camera technology trends

In recent years, with the upgrading of automobile intelligence, various car companies are upgrading from low-level autonomous driving to high-level. Autonomous driving will place higher requirements on active safety functions such as vehicle safety, pedestrian safety, and driver monitoring, and ADAS penetration will inevitably accelerate.

Compared with consumer electronic cameras, the working environment of car cameras is extremely harsh, such as vibration, high temperature, rain and fog, low temperature, and severe light changes. The purpose of the vehicle camera is to drive safety. In each of the above working states, it is necessary to obtain stable, reliable and clear surrounding environment data.

Therefore, with the improvement of automotive industry technology, the related performance requirements of in-vehicle cameras will become more and more stringent. According to the "Automotive Camera Industry Standard" issued in 2019, the vehicle camera is required to work continuously in the environment of -40°C to 85°C, not affected by moisture immersion, anti-magnetic and shock-resistant, and the service life should be 8 to 10 years. In addition, for safety reasons, the car camera needs to keep working even if the power supply is interrupted for a short time.
In addition, features such as high dynamic range, night vision, and LED flicker suppression will continue to gain popularity. At present, the function of the car camera requires it to have the following performance: the car camera often needs to have night vision function, which can suppress the noise during low-light photography, and still have excellent performance in low light conditions. The horizontal viewing angle is expanded to 25°~135° to achieve wide angle and high resolution around the image. Next, let's talk about the performance and technical improvements of car cameras in recent years.

Vehicle camera technology trends
1) Eliminate stray light ghosts and improve optical image stability:
With the optimization and upgrade of the vehicle camera technology, the shock resistance, wear resistance, high temperature and low temperature resistance of the vehicle camera are gradually improved, and the picture quality is clearer.
In order to control the ghost and stray light caused by frontal glare interference such as headlights, maintain optical imaging stability under extreme temperatures or short-term rapid temperature changes, and effectively capture and distinguish object details, in addition to improving the algorithm from the software, Vehicle lens manufacturers are also actively promoting the overall technological progress of vehicle lens products by improving the coating process, improving technical parameters, and adding conductive heating films outside the lens.

2) Pixel upgrade: 800W pixel camera
The core of vehicle camera perception is vision, and the resolution determines the level of vision. With the increasing demand for sensing distance by ADAS functions, more refined and higher resolution cameras in terms of sensing content are the general trend.

For mainstream new energy car companies, 120W to 200W lenses are no longer sufficient for use, and the industry has begun to upgrade to 800W pixels, such as Weilai and Ideal. At present, there are still relatively few manufacturers with the production capacity of 800W pixel camera modules, such as Sunny, Lianchuang Electronics, etc.

3) Lens material: glass-plastic hybrid
Vehicle cameras require high durability and thermal stability. According to the material, the lens of the car camera can be made of glass or plastic. Glass lenses have high durability and scratch resistance, and have better temperature performance, so they are more used in high-end products. The plastic lens is cheap but has poor imaging effect, and it is easy to cause deformation of the lens in the harsh use environment of the car, which affects the imaging quality.
At present, considering cost and performance, mainstream manufacturers of automotive lenses are gradually starting to use glass-plastic hybrid lenses, and some high-end lenses use full-glass solutions.
The performance comparison of plastic and glass lenses is as follows:
Plastic Lens:

Advantages: light weight, low cost, low process difficulty, suitable for mass production;

Disadvantages: slightly lower light transmittance, poor heat resistance, large thermal expansion coefficient, poor wear resistance, low mechanical strength, etc.

Glass lenses:

Advantages: excellent performance, high light transmittance;

Disadvantages: mainly due to the difficulty of mass production, low yield and high cost.

4) Lens technology: aspherical lens
Spherical lenses can cause aberration problems, that is, the focal point of the light entering from the center of the lens and the light entering the edge of the lens are inconsistent, resulting in blurred images. Spherical lenses require a combination of multiple lenses to reduce aberrations.

The aspherical lens is a lens composed of a spherical surface and a curved surface other than a plane. By changing the curvature of the lens, the light is concentrated at a fixed focus, which solves the problem of aberration, and can be achieved with only one lens. Therefore, aspherical lenses have the advantages of miniaturization, light weight and good imaging effect, and have become the best solution for high-pixel vehicle lenses.

Plastic aspherical lenses are produced by injection molding, while glass aspherical lenses are produced by using high-quality optical glass and using precision-controlled hot-molding technology.

5) Self-cleaning and anti-fog defrosting
In-vehicle cameras rely on light transmission to identify road information. Contamination on the surface of the lens will reduce the recognition ability, and it is difficult to reduce the contamination from an optical point of view. In addition, whenever it encounters rain and snow, the cameras exposed outside the car will even experience fogging and frosting problems.

Self-cleaning and anti-fouling: At present, mainstream manufacturers will at least coat a hydrophobic coating on the surface of the lens of the car camera. On the one hand, it can effectively remove dirt by means of water spray cleaning.

Anti-fog and defrosting: At present, there are two directions in the industry. One is by coating, the outer surface of the lens is coated with a hydrophobic film, and the inner surface of the lens is coated with a hydrophilic film; Layer transparent conductive film to achieve heating.

6) AA package
Vehicle lens assembly requires high-precision AA technology. The packaging of the vehicle camera module needs to be assembled many times, and the superposition of errors will lead to a decrease in the product yield. The AA technology makes the relative position of the lens and the CMOS image sensor freely adjustable. It can also collect and analyze imaging data in real time, adjust the horizontal position and the tilt angle of the lens, so as to ensure the clarity of the image and ensure that the optical axis and the focus of the image plane are in the same position. image center.

With the improvement of the resolution of the vehicle camera, the requirements for the positioning accuracy between the lens and the CMOS are also rising. Therefore, the technical content of the AA equipment will affect the mechanical tolerance correction of each component, which in turn affects the camera imaging quality and product consistency.

In the field of in-vehicle cameras, the capital investment brought by AA equipment is very large at this stage, such as imported AEI and ASM. With the growth of domestic equipment manufacturers, such as: Zhongke Precision, Huaya Intelligent, Ivy Vision, Desay Automation, Guanghaojie Technology, Tianzhun, Sunny and so on. The cost of AA equipment will also be reduced to some extent.

7) Night vision technology
In order to ensure the safety of driving, the ADAS function of the car needs to be operated around the clock as much as possible. The camera realizes the perception of the surrounding environment through light sensing and algorithms. Therefore, in scenes with insufficient light, such as driving at night or passing through tunnels, the night vision capability of the camera needs to be enhanced. At present, automotive night vision systems can be divided into three categories according to imaging principles and lenses: low-light, near-infrared, and far-infrared.
Existing night vision assistance systems can identify pedestrians beyond the range of high beams and predict danger in advance.

Low light: Literally understood, it is to amplify a small amount of visible light received, and finally capture and project the image on the corresponding display screen. Low-light is the same as the imaging principle of general cameras, which realizes night vision through visible light, but requires a certain visible light environment.

Near-infrared night vision: Also known as active infrared night vision technology, it refers to irradiating the target with a strong infrared emission source during work, and using the infrared rays reflected by the target to obtain the image of the object. The working band is near-infrared light in the range of 800~1000nm.

Far-infrared night vision (thermal imaging system): It is also called passive infrared night vision technology, which mainly uses the infrared radiation emitted by the object itself to image, which is what everyone calls thermal imaging. The thermal imaging system is based on the difference in infrared emissivity formed by the temperature difference between the target and the background, and uses the radiation thermometry technology to measure the radiation intensity of the target point by point to form a thermal image of the visible target. Its theoretical working band is between 1-14um, but generally far-infrared night vision mainly uses short-wave (3μm-5μm) and long-wave (8μm-14μm).

Among them, low-light night vision needs to be improved from CMOS and algorithms; while infrared night vision needs to be equipped with a special infrared lens to ensure the entry of infrared light. In addition, low-light night vision can see color pictures, while infrared cannot achieve color.