Analysis of the Development of Future Wide Dynamic Video Surveillance Camera Technology

Since the arrangement of natural light is from 100,000 lux to 0.00035 Lux at night, the indoor illuminance is 100 Lux, and the illuminance of the outside scenery may be 10,000 Lux, so when the camera looks out of the room from the window, the contrast between the two is 10000/100=100:1. This contrasting eye can be easily seen because the human eye can handle a contrast ratio of 1000:1, but traditional security surveillance cameras cannot, because it has only 3:1 contrast performance.

Therefore, when a security surveillance camera is used in a scene where the contrast between light and darkness is large or backlighting occurs, the bright area in the entire image is overexposed and the dark area is underexposed, while the brightest and darkest parts of the image cannot be clearly seen. Such as bank savings, import and export of important places. Because the strong light from the outside of the window and the soft light from the fluorescent lamp on the ceiling may cause difficulty in the capture of indoor and outdoor scenes at the time, it is impossible to clearly record indoor and outdoor scenes with great contrast at the same time.

The images will appear too bright if the background is too dark, or if the foreground of the background is too dark and the foreground is too bright for the background. The earliest solution is to use backlight compensation technology or to set up two cameras indoors or outdoors to accommodate larger light contrasts, but the effect is not ideal. The technology to expand the dynamic range has emerged, which is what we call now Wide Dynamic Range WDR (WideDynamicRange) technology.

Panasonic debuted its first-generation wide dynamic CCD camera in 1977; it introduced the second generation in 1999; and the third-generation super dynamic CCD camera was launched in 2003-2008. During this period, Sony, JVC, Samsung, etc. have also introduced their own wide dynamic CCD camera. So far, in the field of security monitoring again and again in the technological reform, led the rapid development of the security industry.

CCD wide dynamic technology uses a special DSP (digital signal processing) circuit to perform the most suitable shutter speed exposure for the bright part, and then exposes the dark part with the most suitable shutter speed, and then the two images are processed by the DSP again. The combination makes the bright part and the dark part visible. Although this 160 times dynamic range technology has the advantages of large wide dynamics and optimized image gray scale, it has high requirements for DSP performance (especially processing speed). At present, due to the limitations of CCD characteristics, even with multiple exposure sampling methods, the wide dynamic range of the camera can only reach 66dB.

Obviously, due to the limitations of the CCD's photographic characteristics, it is difficult to make major breakthroughs in technology, and the CMOS camera has outstanding performance due to its excellent performance of the image sensor itself. Such as the general linear output mode of the dynamic range up to 40 ~ 60dB;

Dalsa Corporation adopts linear-logarithmic output mode IM28-SA CMOS camera, its dynamic range can be as high as 120dB; Apical Co., Ltd. combined Altera CycloneIII and CycloneIVFPGA, using AptinaMT9M033720pWDRCMOS image sensor also introduced the bright part and the dark part Clearly visible CMOS wide dynamic camera;

The United States PIXIM company developed CMOS-DPS technology, its chipset from D1000, D1500, D2000 to D2500 in the performance has been rapidly improved: the image clarity from 480 lines to 540 lines or more; minimum illumination from 1.0Lux/F1. 2 to 0.5 Lux/F1.2; typical wide dynamic range from 95dB to 120dB. According to sources, some CMOS wide dynamic technologies have even reached 160dB.

Therefore, it can be foreseen that the future surveillance cameras belong to wide dynamic cameras, while the wide dynamic technology belongs to CMOS.