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  • Purchase surveillance cameras tips

    When the purchase of surveillance cameras can always see in the technical parameters such as CCD, standard resolution and other parameters, as well as some characteristics about these parameters, the camera will give us the time provided in the purchase of a lot of help.

    1 What is a CCD camera?

    CCD is ChargeCoupledDevice (charge-coupled device) of the abbreviation, it is a semiconductor imaging device, which has high sensitivity, anti-glare, distortion, body Small size, long life, anti-vibration and so on.

    2.CCD camera work

    The subject of the image through the lens focus to the CCD chip, CCD based on the accumulation of the corresponding light intensity ratio of the charge, the charge accumulated in each pixel in the video sequence under the control of the relocation point by point, by filtering, amplification processing, the formation of video signal output. Connect the video signal to a monitor or TV video input you can see the same image with the original video image.

    3 resolution options

    Assess the level of the camera resolution is a resolution of the target, in units of line pairs that can distinguish between black and white image after the number of pairs. Commonly used in black and white camera resolution Generally 380-600, 380-480 color is, the greater its value image more clear. General surveillance applications, with about 400 line black and white cameras to meet the requirements. While In medical image processing and other special occasions, with 600 line camera to get a clearer picture.

    4 SNR.

    The camera image signal and the noise voltage ratio, CCD camera is typically between 45-55dB, the higher the better signal to noise ratio.

    5. Imaging sensitivity

    Usually the minimum illumination requirements that environmental sensitivity of the camera, black and white camera sensitivity is about 0.02-0.5Lux (Lux), color camera and more than in 1Lux . 0.1Lux camera for general surveillance applications; used at night or when ambient light is weak, recommended 0.02Lux camera. Used in conjunction with near-infrared light, the Must also use low-light camera.

    In addition the sensitivity camera with the lens on, 0.97Lux/F0.75 equivalent 2.5Lux/F1.2 equivalent 3.4Lux/F1.4. Reference environment Illumination: Summer sun 100000Lux, cloudy outdoor 10000Lux, television studio 1000Lux, 60W lamp 60cm away from the desktop 300Lux, said interior light 100Lux , Evening room 10Lux, 20cm at the candlelight 10-15Lux, night lights 0.1Lux

    6 Electronic shutter

    Electronic shutter time in 1/50-1/100000 seconds, the camera´s electronic shutter is generally set to automatic electronic shutter mode can automatically adjust the light and dark environment, the shutter time, to get a clear image. Some cameras allow the user to manually adjust the shutter time, to meet some special applications.

    7 External synchronization with external trigger

    External synchronization is between different video devices use the same sync signal to ensure synchronization of the video signal, it can guarantee the output of different devices have the same frame video signal , The line beginning and ending time. To achieve external synchronization, the camera needs to enter a composite sync signal (C-sync) or composite video signals. External synchronization can not guarantee that users from the finger Time to get a complete set of a continuous image, to achieve this feature, you must use some special camera with external triggering.

    8 spectral response

    CCD device made from silicon, are more sensitive to the near-infrared spectral response can be extended to about 1.0um. The response peak for the green light (550nm), distribution curve, such as right Shown. Implicit provision of night monitoring, you can use near-infrared light illumination, the environment in the human eye is unclear, it can be clearly on the monitor image. Since the surface layer of the CCD sensor UV absorption of the transparent electrode, so CCD is not sensitive to UV. Color imaging unit on the camera´s red, green, blue three-color filter section, so the color camera for infrared, Purple Outside are not sensitive.

    9.CCD chip size

    CCD imaging are commonly used size 1 / 2 ", 1 / 3", etc., the smaller the size of the camera image size can be made smaller. In the same optical lens, the image size the more Large field of view angle. Chip size image plane size (width X height) diagonal 1/26.4x4.8mm8mm1/34.8x3.6mm6mm Video camera perspective and lens a few millimeters, CCD´s size are inseparable.

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