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What is frame accumulation?

Sep 26, 2017

solar lte ip surveillance

What is frame accumulation?



Concept

 

First of all to know what is the field, what is the frame. The active television image is composed of a continuous still image with little change in content. One of the still images in the television technology called "a frame", in order to ensure that the image is not flashing, according to the visual characteristics of the human eye (previously appeared in the human eye image will disappear for some time after the disappearance of the image) , Requiring a continuous image of 25 frames per second. In the television transmission technology, in order to further improve the transmission quality, in turn an image is divided into two to pass, this time a called "a" the. So, the TV transmits 50 games per second.

In the camera, the CCD is also in this way, the scene image into a charge to form a video signal. If the illumination is too low, the shooting target on the CCD to form the charge is very small, then the image is not clear or even can not show the image, in order to solve this problem, you can digital image processing technology (DSP) to solve this problem. The specific practice is to increase the CCD on the circuit for each frame of the image of the exposure time, that is, the target micro-photogenerated charge accumulation, rather with the night when the camera, hand-controlled shutter to take pictures, so that the image is relatively clear. Therefore, some of the camera's function called slow shutter. Sometimes called the number slow to open the door.

 

In the frame integration mode, the photo-generated charges stored in the odd-numbered rows of pixels are read out in the odd-numbered fields, and the photo-generated charges stored in the even-numbered pixels are read out in the even-numbered fields, and the photogenerated charge Time is one frame time, ie 1/25 s. Since the photogenerated charge accumulation time of the frame accumulation mode is relatively long, the photogenerated charge of the previous field remains in the photosensitive imaging region and appears in the next field, so there is a time delay which causes a decrease in the dynamic resolution.

 

Way

 

In the field accumulation mode, the charges of two adjacent rows are added to the vertical CCD shift register at the same time. The interlaced readout is achieved by the combination of the combined charges. The photogenerated charge accumulation time for each pixel is a time, ie 1/50 s. (2) the flicker of the vertical edge of the image is reduced; (3) the wide dynamic range and the anti-dispersibility are good; (4) the vertical resolution is slightly There is a decrease.

 

 

Whether the frame accumulation or field accumulation, due to extend the exposure time of the CCD, although the image is relatively clear, but the real-time image changes have been affected, that is, when the shooting target fast movement, there will be smear , The image also appears as an animation effect.


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