On the importance of wide dynamic technology in AI cameras

With the application of artificial intelligence in video surveillance, in addition to the basic requirements in terms of definition, wide dynamic capability has become one of the basic configurations of smart cameras. In certain scenarios, the effect of wide dynamics determines the accuracy of intelligent analysis results.

What is wide dynamic?

Wide dynamic technology is a technique that allows the camera to see the characteristics of the image in very strong contrast.

When a high-luminance area illuminated by a strong light source (daylight, luminaire, or reflective) and a relatively low-intensity area such as a shadow or a backlight are simultaneously present in the image, the image outputted by the camera may appear bright, and the white area becomes white due to overexposure. The dark area becomes black due to insufficient exposure, which seriously affects the image quality.

The camera's performance in the brightest and darker regions in the same scene is limited. This limitation is commonly referred to as the "dynamic range." The technical feature of the wide dynamic camera is that the wide dynamics is mainly used to solve the backlight compensation problem of the camera.

In real life, there are many such monitoring areas with large contrasts of light, such as glass doors, tunnel junctions, buildings, subway entrances and exits, and road monitoring. In the case of strong contrast between light and dark, ordinary cameras are unable to meet the monitoring needs. Therefore, a wide dynamic camera came into being.

What are the technical characteristics?

Broadly speaking, dynamic range refers to the span that a changed thing may change, that is, the area between the lowest pole and the highest pole of its change value. The description of this area is generally between the highest point and the lowest point. Difference. When talking about the captured image indicators of the camera product, the general "dynamic range" refers to the ability of the camera to adapt to the illumination of the scene in the scene, specifically the range of brightness (contrast) and color temperature (contrast).

Natural light is arranged from 120,000 Lux illuminated during daylight to 0.00035 Lux at night. When the camera looks out of the window from inside the room, the indoor illumination is 100 Lux, and the illumination of the outside scenery may be 10,000 Lux, compared to 10,000 Lux/100 Lux = 100:1. In this contrast environment, the human eye can handle it easily because the human eye can handle a contrast ratio of 1000:1. However, the processing power of the camera is judged based on the performance of its various hardware.

The ultra-wide dynamic camera is capable of shooting a large number of excellent surveillance videos in a backlight environment. The space where the light is strong will not be exposed, and the dark space will not be clear. Popularly speaking, the ultra-wide dynamic camera is able to adapt well to the situation where the difference in light intensity between different parts of the unified scene is large, and it can fade the difference in brightness of the light in the final video, so that every part of the whole picture can be Clear and legible.

Current status of wide dynamic technology

With the continuous maturity of video surveillance technology, the sales of wide dynamic cameras have grown by leaps and bounds. At present, wide dynamics have basically become a standard feature of IPC.

The multi-frame wide dynamic processing technology has become the mainstream choice of camera manufacturers. The application of this technology in the camera system makes the dark areas brighter, making the bright areas in the scene softer and changing the visual effects. Provide useful identifiable images.

At present, most of the general surveillance network cameras adopt CMOS+DPS wide dynamic technology. DPS uses a separate exposure and control technology for each pixel, combined with a multi-frame image acquired with a CMOS sensor to synthesize a linear superposition of a complete image, which has a higher dynamic range than the two-exposure imaging of the CCD. Numerically speaking, CMOS cameras using DPS technology can achieve a dynamic range of 120 dB with current processing technology. While expanding the dynamic range, DPS also solves the deficiencies of the CCD sensor in processing dynamic range and color authenticity, and its color reproduction is more realistic and can meet the requirements of the application. A camera using this technology uses an analog-to-digital converter (ADC) in each pixel of the digital image sensor, which directly converts to a digital signal when capturing the optical signal, minimizing the attenuation and interference of the signal in the arrangement. .

At present, the mainstream brand cameras have a nominal dynamic range of 120dB, while the dedicated wide dynamic cameras have a dynamic range of 140dB. Some of them are labeled as true wide dynamics and digital wide dynamics. In the actual test for camera wide dynamics, cameras that are also nominally 120 dB dynamic values ​​may have different wide dynamic effects. It is difficult for us to judge whether the imaging effect of a surveillance camera is good or bad by the manufacturer's bragging. In order to distinguish the differences between the products of different manufacturers, the surveillance cameras of different brands are placed in the same environment, and the image quality and consistency are tested by different light and dynamic display effects, which is essential for the user in the selection process. step.

summary

Through the wide dynamic technology in the abnormal environment, you can see the things that are monitored, and overcome the weakness of the picture when the ordinary camera is surrounded by the bright field. Wide dynamic cameras have a wide range of applications, including finance, education, and transportation. At present, wide dynamics have become an indispensable feature of HD cameras, and market demand is strong.