Detailed Explanation of CMOS Image Sensors for Car Cameras

1. Introduction to CMOS Image Sensors

CMOS (Complementary Metal-Oxide-Semiconductor) image sensors are semiconductor devices that convert light signals into electrical signals. They are widely used in mobile phones, security, medical, and automotive applications. Compared to traditional CCD (Charge-Coupled Device) sensors, CMOS offers low power consumption, high integration, and significant cost advantages, making it the mainstream choice for automotive cameras.

2. Core Requirements for Automotive CMOS Sensors

Due to the complex and ever-changing driving environment, automotive CMOS sensors must meet the following key performance indicators:

2.1 High Dynamic Range (HDR)

Purpose: Produces clear images in both bright light (such as direct sunlight) and low light (such as tunnels and at night).

Technical Solutions:

Multi-exposure synthesis (such as Staggered HDR)

Dual Conversion Gain (DCG)

Local Tone Mapping

2.2 Low-Light Performance

Challenges: Maintaining low noise and a high signal-to-noise ratio (SNR) in low-light environments such as nighttime and tunnels.

Solutions:

Large pixel size (such as 2.1μm, 3.0μm)

Backside-illuminated (BSI) or stacked architecture

Advanced noise reduction algorithms (such as DOL-HDR)

2.3 High Frame Rate and Fast Response

Autonomous driving requirements: A high frame rate (≥60fps) reduces motion blur and improves recognition accuracy.

Technical Implementation:

Global Shutter (avoids rolling shutter effect)

High-speed readout circuit design

2.4 Temperature Stability

In-vehicle Environment: Stable operation within a wide temperature range of -40°C to 105°C is required.

Solution:

High-temperature-resistant semiconductor materials

Temperature compensation algorithm

3. Future Trends

3.1 Higher Resolution (8MP+)

As autonomous driving levels increase, 4K (8-megapixel) cameras will become mainstream to meet the need for object recognition at longer distances.

3.2 Multispectral Sensing (RGB-IR)

The addition of infrared (IR) sensors can enhance imaging capabilities at night and in inclement weather, improving autonomous driving safety.

3.3 Sensor Fusion (LiDAR + CIS)

In the future, CMOS sensors may be deeply integrated with LiDAR to achieve more accurate environmental perception.

3.4 AI-ISP Integration

With a built-in AI acceleration unit, CMOS sensors can perform image processing directly on the chip, reducing system latency.

Conclusion

Automotive CMOS image sensors serve as the "eyes" of intelligent driving, and their technological development directly impacts the reliability and safety of autonomous driving. In the future, with continuous breakthroughs in technologies such as HDR, low-light performance, and high frame rates, CMOS sensors will play an even more critical role in L3+ autonomous driving.