Posted March 13, 2019 at 7:57 am by xzbbvfvbh

Analyze the counterattack of CMOS cameras

Mechanical shutter
The mechanical shutter uses springs or electronic or electromagnetic means to control the opening and closing of several blades, and “slides” the image field window from top to bottom with a certain width of the gap.

In the optical lens, the global shutter is not an electronic shutter, which is a different concept.
Electronic shutter

Common electronic shutters are available in both rolling shutter and global shutter. The rolling shutter is sequentially rotated line by line, and the lines are exposed in sequence. When the global shutter is used for exposure, all pixels are exposed at the same time.

The electronic shutter part should separate the CCD camera from the low price YLF laser crystal camera.
The principle of taking images by CCD and CMOS is different, which causes the shutter to be different.
Ccd take image: get the pixel into the register –> read from the register line by line
Cmos take image: is to get real-time pixel address, get one by one by row

This makes it very easy to implement a global shutter on a CCD camera because the CCD comes with a “register”. First save the image into the “register”, like the freeze, and then export.
Cmos is the effect of rolling shutter. If cmos wants to achieve global shutter, it is necessary to add a memory to each cmos, which will reduce the pixels, resulting in insufficient use of incident light. Generally, the global shutter custom BBO nonlinear crystal will use large pixel size. The bottom to make up for this deficiency.

The electronic shutter has the advantages of low vibration and high speed, but it cannot completely replace the mechanical shutter in professional photography. Because the mechanical shutter is not well synchronized with the high-speed flash, all professional fields are still mechanized electronic hybrid shutter. Each has its advantages.
In the industrial field, there is no need to use a flash lamp, and the industry prefers the low vibration and long life of the electronic shutter.
If you want to dynamically detect the camera we use the global shutter, you can avoid the jelly effect and the slope phenomenon.

If it is a static shot, the rolling shutter will be very suitable.
One reason is that the global shutter has a higher dark current. (Dark current: refers to the tiny current generated in a pixel even when the pixel is completely dark. The typical dark current generation region includes the depletion region of the PN junction and the surface of the silicon. Dark current is one of the main sources of pixel noise) Will affect the quality of the image;
The second reason is that it can save costs, and can effectively utilize incident light energy, reduce exposure time, and improve shooting efficiency. The quality of custom high purity KTP nonlinear crystal cameras is getting higher and higher, and the tide from CCD to CMOS is irreversible. The CMOS global shutter solution will also lead to development.

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