Analysis of vehicle camera technology trends

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

There are more and more cameras in various models. But basically, there will be at least one ADAS front-view camera and four surround-view cameras. If we add the driver monitoring camera, which has been increasingly valued in recent years, it can be predicted that in the next few years, at least 6 cameras will be needed on the car, and the market prospects are huge.

Car cameras are safety-oriented and their technology is constantly upgraded

Compared with consumer electronic cameras, the working environment of vehicle cameras is extremely harsh, such as vibration, high temperature, rain and fog, low temperature, drastic changes in light, etc. The purpose of vehicle cameras is to ensure driving safety, and they need to be able to obtain stable, reliable, and clear surrounding environment data under the above working conditions.

Therefore, with the improvement of automotive industry technology, the performance requirements of vehicle-mounted cameras will become more and more stringent. According to the "Automotive Camera Industry Standard" issued in 2019, vehicle-mounted cameras are required to be able to work continuously in an environment of -40°C to 85°C, not be affected by water immersion, be anti-magnetic and shock-resistant, and have a service life of 8 to 10 years. In addition, for safety reasons, vehicle-mounted cameras need to be able to continue to work even when the power supply is interrupted for a short time.

In addition, high dynamic range, night vision, LED flicker suppression and other performance will continue to become popular. At present, the functional requirements of vehicle-mounted cameras need to have the following performance: vehicle-mounted cameras often also need to have night vision function, be able to suppress noise during low-light photography, and still have excellent performance under low-light conditions. The horizontal viewing angle is expanded to 25°~135°, and high resolution of wide angle and peripheral parts of the image must be achieved. Next, let's talk about the performance and technical improvements of vehicle-mounted cameras in recent years.

Technology Trends of Car Cameras

Eliminate stray light and ghosting to improve optical imaging stability

With the optimization and upgrading of vehicle-mounted camera technology, the vehicle-mounted camera's ability to resist shock, wear, high and low temperatures has gradually improved, and the image quality has become clearer.

In order to control ghosting and stray light caused by strong frontal light 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 algorithms from a software perspective, automotive lens manufacturers are also actively promoting the overall technological progress of automotive lens products by improving coating processes, improving technical parameters, and adding conductive heating films to the outside of the lens.

Pixel upgrade: 800W pixel camera

The core of vehicle camera perception is vision, and resolution determines the quality of vision. As ADAS functions increase the demand for perception distance, cameras with finer perception content and higher resolution are the general trend.

For mainstream new energy vehicle companies, 120W to 200W lenses are no longer sufficient, and the industry has begun to upgrade to 800W pixels, such as Weilai and Ideal. Currently, there are relatively few manufacturers with the ability to produce 800W pixel camera modules, such as Sunny Optical and Lianchuang Electronics.

Lens material: glass-plastic mixture

Car cameras are required to have high durability and thermal stability. According to the material, the lenses of car cameras can be made of glass or plastic. Glass lenses are highly durable and scratch-resistant, and have good temperature performance, so they are more often used in high-end products. Plastic lenses are cheap but have poor imaging effects, and are prone to deformation in the harsh use environment of cars, affecting imaging quality.

At present, taking into account cost and performance, mainstream manufacturers' automotive lenses are gradually beginning to use glass-plastic hybrid lenses as the main materials, and some high-end lenses adopt all-glass solutions.

The performance comparison between plastic and glass lenses is as follows:

Plastic lens:

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

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

Glass lenses:

Advantages: excellent performance and high light transmittance;

Disadvantages: Mainly the difficulty in mass production, low yield and high cost.

Lens technology: Aspherical lens

Spherical lenses can cause aberration problems, that is, the focus of the light entering from the center of the lens is inconsistent with that of the light entering from the edge of the lens, which in turn causes blurred images. Spherical lenses require a combination of multiple lenses to reduce aberrations.

Aspherical lenses are composed of curved surfaces other than spherical surfaces and planes. By changing the curvature of the lens, the light is focused at a fixed focus, solving the aberration problem, and only one lens is needed to achieve this. Therefore, aspherical lenses have the advantages of miniaturization, light weight and good imaging effect, and have become the best solution for high-pixel automotive lenses.

Plastic aspheric lenses are produced by injection molding, while glass aspheric lenses are made of high-quality optical glass and precision-controlled hot molding technology. Currently, companies with the ability to produce aspheric lenses for automotive cameras include: Sunny Optical, Lianchuang Electronics, Lantech Optics, etc.

Self-cleaning and anti-fog defrosting

Car cameras rely on light transmission to identify road information. Dirt on the lens surface will reduce recognition capabilities, and it is difficult to reduce dirt from an optical perspective. In addition, whenever there is rain or snow, the camera exposed outside the car will even fog and frost.

Self-cleaning and anti-fouling: Currently, mainstream manufacturers will at least coat the lens surface of the car camera with a layer of hydrophobic coating, which can effectively remove dirt through means such as water spray cleaning.

Image source: Ningbo Jieao

Anti-fog and defrosting: There are currently two directions in the industry. One is through coating, coating the outer surface of the lens with a hydrophobic film and the inner surface of the lens with a hydrophilic film; the other is to use a heating solution, either heating the entire lens or making a layer of transparent conductive film on the surface of the lens to achieve heating.

AA package

The assembly of vehicle lenses requires high-precision AA technology. The packaging of vehicle camera modules requires multiple assembly processes, and the superposition of errors will lead to a decrease in product yield. AA technology allows the relative position of the lens and the CMOS image sensor to be freely adjustable. It can also collect and analyze imaging data in real time, adjust the horizontal position and the tilt angle of the lens, thereby ensuring image clarity and ensuring that the focus of the optical axis and the image plane is at the center of the image.

As the resolution of automotive cameras increases, the positioning accuracy requirements between the lens and CMOS are also increasing. Therefore, the technical content of 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 vehicle-mounted cameras, the capital investment brought by AA equipment is very large at this stage, such as imported AEI and ASM. However, with the growth of domestic equipment manufacturers, such as: Zhongke Precision, Huaya Intelligent, Aiweishi, Desay Automation, Guanghaojie Technology, Tianjue, Sunny Optical, etc. The cost of AA equipment will also decrease to a certain extent.

Night Vision Technology

To ensure driving safety, the ADAS function of the car needs to be able to operate around the clock as much as possible. The camera perceives the surrounding environment through photosensitivity and algorithms, so in scenes with insufficient light, such as driving at night and passing through tunnels, the night vision capability of the camera needs to be enhanced. At present, the night vision system of the car can be divided into three categories according to the imaging principle and lens: low light, near infrared and far infrared.

The existing night vision assistance system can identify pedestrians beyond the range of the high beam and predict danger in advance. Source: Xuanyuan Intelligent Driving

Low light: literally, it is to amplify the small amount of visible light received, and finally collect and project the image onto the corresponding display screen. Low light is consistent with the imaging principle of general cameras, both of which realize night vision through visible light, but a certain visible light environment is required.

Near-infrared night vision: Also known as active infrared night vision technology, it refers to using a strong infrared emission source to illuminate the target during operation, and using the infrared light reflected back from the target to obtain the image of the object. The working band is near-infrared light of 800~1000nm.