CCD is the abbreviation of Charge Coupled Device, which is the core component of gel image system and is a photoelectric conversion device. Most people have a certain understanding of digital cameras, and many people are experts in this field. Some people look at the pixels of the digital camera very heavy, but after comparison, it is found that some 4 million, 5 million pixel camera shots are not as good as the 300-pixel machine. Why?
In fact, there are many factors affecting imaging. The indicators for measuring CCD quality are resolution, CCD size, dynamic range, sensitivity, quantum efficiency, signal-to-noise ratio, etc. Among them, the number of pixels and CCD size are important indicators. In fact, it refers to the size of the photosensitive device. Here, the larger the area of ​​the CCD sensor, the larger the CCD area, the more photons are captured, the better the photographic performance, and the lower the signal-to-noise ratio.
In order to better understand the size of the CCD, the CCD specifications currently applied on the market are as follows:
1/2 inch - the target size is 6.4mm wide by 4.8mm high and 8mm diagonal.
1/3 inch - the target size is 4.8mm wide by 3.6mm high and 6mm diagonal.
1/4 inch - the target size is 3.2mm wide by 2.4mm high and 4mm diagonal.
1 inch - the target size is 12.7mm wide by 9.6mm high and 16mm diagonal.
2/3 inch - the target size is 8.8mm wide by 6.6mm high and 11mm diagonal.
The resolution of CCD is from low to high: from about 450,000, about 1 million, about 1.4 million, about 2 million, about 3 million, about 4 million, about 5 million, and even higher, according to the temperature of CCD. Can be divided into normal temperature CCD camera and refrigeration CCD camera, refrigeration CCD: in the same full well electronic CCD, reduce CCD noise, can improve the CCD monitoring ability, hot or dark current is CCD for noise, noise in the Cool CCD basic Can be eliminated by the deep-cooled Peltier. After exposure for more than 5-10 seconds, the CCD chip will heat up. Without the chip of the cooling device, the "hot" or white pixels will cover the image, and the image will be visible everywhere. CCD structure design, digital methods, etc. will affect the noise. Of course, by improving the structure and optimizing the method, noise can also be reduced.
The applicability of the refrigeration CCD: Fluorescence and chemiluminescence itself are weak, so the CCD noise reduction is very high. A high-resolution digital cooling CCD camera combined with a high-pass lens head system should be used to capture the extremely weak fluorescence of the signal. And chemiluminescence sample images, and can minimize noise, reduce background, and provide excellent image clarity. An optional excitation source and multiple filter wheels expand the range of applications for fluorescence/chemiluminescence imaging. Therefore, it is generally necessary to select a refrigeration CCD during fluorescence and chemiluminescence observation. Therefore, the refrigeration CCD camera is definitely the future development trend of the high-end molecular imaging imaging analysis system and must be required.
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