Basic structure, types, advantages and disadvantages of electronic rearview mirrors

        With the continuous advancement of automotive technology, electronic rearview mirrors, as an emerging in-vehicle device, have gradually entered the public eye. Not only do they differ significantly from traditional rearview mirrors in structure and functionality, but they also offer unique advantages in improving driving safety and comfort. However, the widespread adoption of this new technology is also accompanied by challenges and controversies. This article will provide an in-depth analysis of the basic structure, types, advantages and disadvantages, giving you a comprehensive understanding of this innovative automotive technology and exploring whether it will become standard equipment in future vehicles.

Electronic Rearview Mirror Basic Structure

Components

Camera: Integrated in the vehicle's rear bumper, roof, or on the outside of the sideview mirror (side camera), equipped with a wide-angle/ultra-wide-angle lens (covering 120°–180°); it supports automatic aperture adjustment and dynamic range optimization (HDR) to enhance image clarity in backlit and low-light conditions. Display: Embedded in the vehicle's rearview mirror or on the door trim (side electronic mirror display), it features an anti-glare, high-contrast screen.

Control Unit: Integrates an image processing chip, video codec, and data transmission module, receiving raw signals from multiple cameras and performing preprocessing such as denoising, sharpening, and distortion correction.

Data Transmission Process

Video Capture: The rear camera captures the rearward motion image, while the side cameras simultaneously capture the field of view on both sides of the vehicle.

Data Transmission: Utilizes onboard Ethernet, offering high-bandwidth transmission speeds exceeding 1 Gbps and latency less than 20 ms.

Video Processing: Multi-frame synthesis technology reduces image noise, and gyroscope data is used to stabilize the image during bumpy driving.

Terminal Display: The rearview mirror displays a panoramic rearview image, while the side displays provide close-ups of the side blind spots.

Electronic rearview mirror type

Type 1 Hybrid Rearview Mirror

Structural Features: The physical left and right rearview mirrors are retained, while side cameras are added. The images captured by the side cameras are transmitted to the interior rearview mirror display and then algorithmically integrated with the rear camera image to create a wide-angle, low-blind-angle panoramic rearview image. The physical rearview mirrors can still be used independently to view the real-world image.

Advantages: Drivers can switch freely between traditional physical mirrors and electronic fusion images, taking into account compatibility with traditional driving habits (such as a quick glance at the physical mirror) and the expanded field of view of the electronic system. It is especially suitable for users who are new to electronic rearview mirrors to shorten the adaptation period; through multi-camera image fusion, the traditional rearview mirror's field of view of approximately 50°–70° can be expanded to 120°–150°.

Type 2: Purely Electronic Rearview Mirror

Structural Features: Physical left and right side mirrors are eliminated, leaving only cameras (side cameras + rear camera). Side images are displayed independently on dedicated screens on the door trim, while the rearview is displayed on the in-car streaming rearview mirror. These three images are independent and uninterrupted.

Advantages: Eliminating the protruding physical mirrors creates a smoother side profile, reducing drag by 3%-5%. The side displays can be individually adjusted, allowing the driver to simultaneously monitor the blind spot and oncoming vehicles directly behind without turning their head, improving parking efficiency. Raw data from each camera is directly fed into the driver assistance system, eliminating the need for image fusion algorithmic loss.

Advantages and Disadvantages of Electronic Rearview Mirrors

Advantages

Improved Range and Energy Efficiency: Side cameras are more compact than traditional rearview mirrors, optimizing aerodynamics and reducing noise, thereby improving vehicle efficiency and range. For example, Honda claims that electronic rearview mirrors can improve energy efficiency by 3.8%, thereby increasing range.

Eliminates Blind Spots: Wide-angle lenses provide a wider rearward field of view, significantly reducing the blind spots of traditional rearview mirrors and minimizing safety hazards when changing lanes or merging.

Enhanced Image Clarity in Complex Environments: In tunnels, low-light conditions at night, or inclement weather, the camera in an electronic rearview mirror optimizes the image by adjusting exposure, ISO sensitivity, and white balance. Traditional rearview mirrors rely solely on the human eye to adapt to ambient light and are easily limited by lighting conditions.

Disadvantages

High cost and complex maintenance: The camera structure is more sophisticated than traditional mirrors, resulting in higher purchase and replacement costs and a greater risk of failure. Repairs require the electronic system rather than simply replacing the lens.

Image quality depends on the stability of the technology: Blurred or noisy images may appear in low-light conditions, and lens flare can easily occur in strong direct sunlight. If the display brightness cannot be adjusted, it may cause visual disturbance during night driving.

Unfriendly to people with poor vision (presbyopia/hyperopia): Traditional rearview mirrors reflect light from distant objects, and the human eye focuses on the distant view. However, the display screen of an electronic rearview mirror is closer to the driver, and the human eye must frequently switch focus between the near view (the display screen) and the distant view (the road). Users with presbyopia may experience blur when viewing information on the electronic screen. Drivers who wear bifocal glasses (the upper half is for distance vision and the lower half is for near vision) have a particular difficulty. When switching focus at night, the vision may be blurred because the lens design cannot adapt to the near scene.