Speaking of the size of the CCD, it is actually the size of the photosensitive device, including CCD and CMOS. The size of the photosensitive device, the larger the CCD/CMOS area, the more photons are captured, the better the photographic performance, and the lower the signal-to-noise ratio. CCD/CMOS is a component used by digital cameras for photographic imaging, which is equivalent to film in optical conventional cameras.
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The surface of the photosensitive member on the CCD has the ability to store charges and is arranged in a matrix. When light is felt on the surface, the charge is reflected on the component, and the signals generated by all the photosensitive components on the entire CCD form a complete picture.
If you decompose the CCD, you will find that the structure of the CCD is three layers, the first layer is the "micro lens", the second layer is the "dichroic filter" and the third layer is the "photosensitive layer".
The first layer of "micro lens"
We know that the key to digital camera imaging lies in its photosensitive layer. In order to expand the CCD's luminous rate, it is necessary to extend the light receiving area of ​​a single pixel. However, the method of increasing the daylighting rate is also likely to degrade the image quality. This layer of "micro lens" is equivalent to adding a pair of glasses in front of the photosensitive layer. Therefore, the photosensitive area is no longer determined by the opening area of ​​the sensor, but is determined by the surface area of ​​the microlens.
The second layer is the "separation filter"
The second layer of the CCD is a "color separation filter". There are currently two color separation methods, one is the RGB primary color separation method, and the other is the CMYK complementary color separation method. First of all, let us first understand the concept of two color separation methods, RGB is the three primary color separation method, almost all the colors that human glasses can recognize, can be composed of red, green and blue, and the three letters of RGB are Red. Green and Blue, which means that the RGB color separation method is adjusted by the color of these three channels. Let's talk about CMYK, which is made up of the colors of four channels. They are cyan (C), magenta (M), yellow (Y), and black (K). In the printing industry, CMYK is more suitable, but its adjusted color is not as much as RGB.
The advantage of the primary color CCD is that the picture quality is sharp and the color is real, but the disadvantage is the noise problem. Therefore, you can note that digital cameras that use primary color CCDs generally do not exceed 400 in ISO sensitivity. In contrast, the complementary color CCD has a Y yellow color filter, which is more careful in color resolution, but sacrifices the resolution of some images. In the ISO value, the complementary color CCD can tolerate higher sensitivity, generally Can be set above 800
Third layer: photosensitive layer
The third layer of the CCD is a "photosensitive sheet". This layer is mainly responsible for converting the light source that passes through the filter color layer into an electronic signal, and transmits the signal to the image processing chip to restore the image.
The conventional camera film size is 35mm, 35mm is the diagonal length, and the 35mm film has a photosensitive area of ​​36 x 24mm. Converted to a digital camera, the diagonal length is approximately 35mm, and the CCD/CMOS size is larger. In SLR digital cameras, many have CCD/CMOS sizes close to 35mm, such as the Nikon D100. The CCD/CMOS size is 23.7 x 15.6, which is much larger than the consumer digital camera, and Canon's EOS-1Ds CMOS. The size is 36 x 24mm, which is 35mm, so the imaging is relatively good.
Consumer-grade digital cameras on the market today are mainly 2/3 inches, 1/1.8 inches, 1/2.7 inches, and 1/3.2 inches. The larger the CCD/CMOS size, the larger the photosensitive area and the better the imaging effect. The 1/1.8-inch 3 megapixel camera is usually better than a 1/2.7-inch 4 megapixel camera (the latter has only 55% of the former). While the same size of CCD / CMOS pixel increase is a good thing, but it will also lead to a reduction in the photosensitive area of ​​a single pixel, there is the possibility of underexposure. However, if you want to maintain the existing image quality while increasing the CCD/CMOS pixels, you must increase the total area of ​​the CCD/CMOS by at least maintaining a single pixel area without reducing. At present, larger CCD/CMOS processing is more difficult and costly. Therefore, digital cameras with larger CCD/CMOS sizes are also more expensive. The size of the photosensitive device directly affects the volumetric weight of the digital camera. Ultra-thin, ultra-light digital cameras generally have small CCD/CMOS sizes, and the more professional digital cameras, the larger the CCD/CMOS size.
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