Correct understanding of low illumination cameras

There are different opinions on the definition of low illumination. There is no consensus that color cameras range from 0.0004 lux to 1 lux, and monochrome cameras range from 0.0003 to 0.1 lux. There is no unified standard, and there are situations where each speaks its own way. Industry insiders emphasized that how low the illuminance can be depends not only on the aperture size (F value) of the lens, but also on the conditions under which the indicated LUX value can appear, otherwise it is just a digital game! In terms of aperture size (F value), the larger the aperture, the smaller the F value it represents and the lower the illuminance required. In addition, has the electronic sensitivity (ELECTRONIC, SENSITIVITY) been increased, and what is the cumulative number of frames on a single screen? Is infrared light ON or OFF? … Etc. should be understood clearly so as not to be confused by the illuminance values ​​indicated in the specifications.

The evolution of low-light cameras in the Chinese market The evolution of low-light cameras in the Chinese market is simply divided into the following three steps:

Daytime color / black and white at night (COLOR / MONO); slow shutter (SLOW / SHUTTER) and super-sensitivity camera (EXVIEW / HAD).

1. Daytime color / black and white at night (day / night type camera COLOR / MONO) This type of camera still has its specific demand group in the market. The domestic market in the United States before the launch of the DIS888C low-light night vision camera PC-360D, night vision The camera has always been the mainstream product of this type of night vision. The illuminance of the COLOR / MONO camera is the lowest in the domestic market, even 0LUX. We ca n’t help but ask: "The camera is made of optical principles, how to image at 0 illuminance?" Color / Mono in the daytime (COLOR / MONO) ) The camera uses the feature of high sensitivity of black and white image to infrared. Under certain light source conditions, the image is converted from color to black and white by line switching method, so as to match infrared. In the technical evolution of color / black and white line conversion, early phases like PHILIPS (Philips), IKEGAMI (Ikegami), and Japanese JVC used 2 SENSOR (1 color, 1 black and white) to share a set of circuits and then switched. The type of camera has adopted a single CCD (color) design. It is a color camera in the daytime or when the light source is sufficient. When the night comes or the light source is insufficient (generally in 1LUX ~ 3LUX), the digital signal is eliminated by the digital circuit to become a black and white image, and In order to match the infrared, the infrared filter that is indispensable for the color camera is also removed. Although this method can achieve the purpose of "low illumination" at night, it has the disadvantages of blurred images and unnatural colors during the day, and the camera's shooting distance Will be limited by the distance of the infrared lamp. According to the manufacturer, in order to make up for this shortcoming, Japan ’s SANYO has introduced a model that uses a motor to control the opening and closing of the filter (that is, with the switching of color / black and white images, opening and closing the filter), but this model also seems to have The market disappeared. However, whether the COLOR MONO camera is a "low-illumination" camera is still quite controversial. Experts point out that the real "low-illumination camera" should refer to the functions that can be achieved by the camera itself (the components used, the technology), and the color / The black-and-white camera at night is limited by the CCD sensitivity, and cannot be changed by itself. It only uses line switching and infrared light to enhance the function. It cannot be regarded as a low-light camera.

2. Low-speed shutter (SLOW / SHUTTER) This type of camera is also called (picture) accumulation type camera. It is a technology that uses computer memory to continuously accumulate several more blurred pictures due to insufficient light to become a clear image. The use of SLOW SHUTTER technology reduces the camera's illumination to 0.008LUX / F1.2 (× 128), and the number of frames (128 frames) that can be accumulated on the screen is a leading level even including imported brands. This type of low-light camera is suitable for museums that are prohibited from damage by red and ultraviolet rays, night biological activity observation, night military coastline monitoring, etc., and the monitoring of relatively static properties. Xu Tanbin, the manager of the marketing department of Taiwan Liling Enterprise, believes that the camera using SLOW SHUTTER technology is the real low-light camera; Zhang Zhiming, business manager of Taiwan Lingan Technology, believes that the standard low-light camera should refer to the (picture) cumulative camera. At present, this type of low-illumination camera is dominated by Taiwanese manufacturers with lilin. Imported brands include NEC, IKEGAMI, FUJULSU, MITSUBISHI, SAMSUNG, etc. Most imported brands are expensive and have a small accumulated frame number (32 frames), such as Ikegami in Japan (IKEGAMI) ICD-870P illuminance 0.03 / F1.2 (× 32). For this reason, the engineering and distributors should prefer the P-CAM (Taiwan P-CAM) which is also technologically advanced. 3. Super-sensitivity camera (EXVIEW / HAD) Super-sensitivity camera (EXVIEW / HAD), also known as 24-hour camera, is the most popular model in the world in 1998, its color illumination can reach 0.05LUX, and black and white can reach 0.003 -0.001LUX (can also be combined with infrared to achieve 0LUX) not only can clearly identify the image, but also real-time continuous picture. This type of camera mainly uses EXVIEW / HAD / CCD (super Sense CCD), which uses patented technology to increase the aperture ratio of each pixel of the CCD, thereby meeting the requirement of lower illumination. Because the cost of the CCD process is still high, the total amount of each month in the world in 1999 is not yet Up to 4,000 units; the technical barriers for relative finished product manufacturers to develop such cameras are also high. During the 2000 Beijing Expo, the DIS888C and DIS988C of the night vision series launched by the US discover used EXVIEW HAD CCD technology to show their unparalleled night vision effect. The technology adopted is EXVIEW HAD CCD + picture accumulation technology, and basically eliminated the drag The shadow phenomenon is estimated to be at the leading level in terms of current global technology.