CCD camera test method

Test Camera Mainly test the clarity and color reproduction, illumination, backlight compensation, followed by the spherical distortion, power consumption, and minimum operating voltage. The following is an introduction to the measurement steps of clarity and color reproduction, illumination, and backlight compensation.

1. Measurement of clarity

When testing multiple cameras, the same lens should be used (fixed focus and variable lens are recommended). The center circle of the test card appears on the left and right sides of the monitor screen. Clearly and accurately count the given scale lines, a total of 10 groups of vertical lines and 10 groups of horizontal lines. They represent the vertical clarity and horizontal clarity respectively, and the number of lines is given in the corresponding group. For example, 350 lines vertically and 800 lines horizontally. At this time, it is best to use a black and white monitor. When testing, you can focus on the distant object, or you can focus while measuring. It is best to use both, so that you can see the difference of this camera (convergence for far and near).

2. Color reproduction test

To test this parameter, you should choose a good color monitor. First, observe the people and clothing from a distance to see if there is any color distortion, compare with brightly colored objects to see the camera's reaction sensitivity, put a color album in front of the camera to see how clear the picture is, whether it is too light or too dark, and then record the moving color object again to see if there is any color tailing, delay, blur, etc. The test conditions are as follows: when the camera's most modern illumination is 50V, it should be measured under the illumination of 50+10V, that is, ten volts are added to the most modern illumination of each camera, and the aperture should be kept in the closest state.

3. Illumination

Place the camera in a dark room with active 220V incandescent lamps in front and behind. Install a voltage regulator to adjust the voltage high to adjust the brightness of the light in the dark room. The voltage can be adjusted from 0V to 250V. The indoor lighting can also be adjusted from the darkest to the brightest. When testing, open the camera aperture to the maximum and record the lowest illumination value (use the voltage regulator to dim the active lamp until the built-in image in the dark room cannot be seen clearly). Then open the aperture to the minimum and record the lowest illumination value. The front and rear lights can also be adjusted to flicker separately.

4. Backlight compensation

There are two ways to test this parameter: one is to turn on the voltage-adjusting light on the front side of the camera in a dark room, adjust it to the brightest, then place a picture or text under the light, and face the camera towards the light to see if the image and text can be seen clearly, whether the picture is glaring, and adjust the AL and AX shift switches to see if there is any change, which effect is best. The other is to point the camera out of the window in sufficient sunlight to see if the image and text can be seen clearly.

5. Spherical distortion

To check spherical distortion, place the test card in front of the camera so that the entire sphere appears on the screen. Check whether the sphere is elliptical. Move the camera forward to see if the center of the circle is magnified. Then test the edges, corners, and frames from a distance to see if there is arc distortion.

6. Power consumption

Minimum operating voltage, use a multimeter to measure the current, and use a small voltage regulator to adjust the voltage.

Correct understanding of low-light cameras

目前市场上标榜的低照度摄像机无论是厂商或是进口商，对低照度的定义众说纷纭，莫衷一是，彩色摄像机从0.0004LUX～1LUX，黑白摄像机从0.0003～0.1LUX均有，(若搭配红外线，则均可达 0LUX)，这就是国内市场在CCTV产业的技术规格方面并无统一标准，而产生各说各话的情况。行业内人士强调，照度能低到多少，不仅要看镜头的光圈大小(F值)，更要看是在什麽条件限制下才能出现所标示的LUX值，否则只是流于数字的游戏罢了!以光圈大小(F值)而言，光圈愈大则其所代表的F值愈小，所需的照度愈低。另外电子灵敏度(ELECTRONIC、SENSITIVITY)是否提高，单一画面累积帧数为多少?红外线是ON还是OFF?……等都应了解清楚，才不致被规格所标示的照度数值所混淆。

The evolution of low-light cameras in the Chinese market The evolution of low-light cameras in the Chinese market can be simply divided into the following three steps: color during the day/black and white at night (COLOR/MONO); slow shutter (SLOW/SHUTTER) and ultra-sensitive cameras (EXVIEW/HAD).

1. Color during the day/black and white at night (day and night camera COLOR/MONO)

This type of camera still has a specific demand group in the market. The lowest illumination value of day and night (COLOR/MONO) cameras in the domestic market is even 0LUX. We can't help but ask: "Cameras are made of optical principles, how can they form images under 0 illumination?" Daytime color/night black and white (COLOR/MONO) cameras use the characteristics of black and white images being more sensitive to infrared rays. Under certain light conditions, they use line switching to convert images from color to black and white to facilitate matching with infrared rays. In the process of color/black and white line conversion technology evolution, this type of camera has adopted a single CCD (color) design. It is a color camera during the day or when there is sufficient light. When night falls or the light is insufficient (generally between 1LUX and 3LUX), the color signal is eliminated by digital circuits to become a black and white image. In order to match infrared rays, the infrared filter that is indispensable for color cameras is also removed. The real "low-light camera" should refer to the functions that can be achieved by the camera itself (the components and technologies used). The color camera during the day/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 considered a low-light camera.

2. SLOW/SHUTTER

This type of camera is also called a cumulative camera. It uses computer memory technology to continuously accumulate several blurry images due to insufficient light to form a clear image. The SLOW SHUTTER technology is used to reduce the camera illumination to 0.008LUX/F1.2 (128), and the number of frames that can be accumulated (128 frames) is at the leading level even among imported brands. This type of low-light camera is suitable for museums that prohibit damage by infrared and ultraviolet rays, night biological activity observation, night military coastline monitoring, etc., and is suitable for monitoring relatively static places.

3. Super Sensitivity Camera (EXVIEW/HAD)

The super-sensitive camera (EXVIEW/HAD), also known as a 24-hour camera, has a color illumination of up to 0.05LUX and a black-and-white illumination of 0.003-0.001LUX (can also be combined with infrared to reach 0LUX). It can not only clearly identify images, but also provide real-time continuous images.

Introduction to Ultra-Low-Light Cameras and Infrared Lights

Ultra-low illumination cameras are a hot product in the surveillance industry that has been launched in recent years with the development of semiconductor technology. They are currently widely used in finance, cultural and museum, hotels, office buildings, residential property management and other fields. As traditional cameras cannot meet the needs of 24-hour continuous monitoring (because it is impossible to keep lights on 24 hours a day at any location), new ultra-low illumination cameras have seized this opportunity and developed rapidly.

Most general ultra-low illumination cameras use Exview HAD technology. Cameras using Exview HAD CCD will greatly improve their sensitivity to external light. In the near-infrared region, their sensitivity can be increased to 4 times that of ordinary cameras. Therefore, even in a very dark environment, this camera can usually see objects that are invisible to the human eye. The emergence of this technology has been welcomed by the monitoring market and can show the best effect in various lighting environments. In particular, when used with dedicated infrared lighting equipment, high-definition black and white images can be obtained, and monitoring with 0 illumination (in the absence of light) can be achieved. In the near-infrared region of 760mm-1100mm, if infrared lighting with a suitable wavelength is used, clear black and white images can be achieved.

Similarly, the method of obtaining images under low illumination is to increase the exposure of the CCD in a single frame image by accumulating the charge in a single frame, thereby increasing the sensitivity of the camera to the single frame image. This method can also obtain a lower illumination index, but it is necessary to reduce the coherence of the image, so when choosing this camera, be careful not to use it with a pan/tilt head as much as possible, otherwise it will cause the phenomenon of losing the picture. There are some other ways to obtain images under low illumination, but none of them can fundamentally solve the illumination problem.

In addition, there are a few points to note when choosing to use low-light cameras and infrared lamps. First, you must choose an appropriate lens. In order to improve the camera's sensitivity to infrared lamps and scenes, you should choose a lens with a large light transmission as much as possible, and pay attention to the use of automatic aperture or electric variable lens. The aperture drive level should be as large as possible. Because generally as the focal length of the lens increases, its light transmission will be relatively reduced. When choosing an infrared lamp, you should leave a certain margin and pay attention to the nominal indicators of the infrared lamp. Second, the power supply of the infrared lamp should meet the minimum power required as much as possible. It often happens that the irradiation distance is not enough. Third, the degree of reflection of the scene being photographed should be considered. Since infrared rays have the same characteristics as visible light, such as reflection and refraction, a certain distance margin should be considered if there is no good reflective environment around the target scene (such as buildings, walls, signs).