CCD charge coupled device

There are many indicators to measure the quality of CCD, such as the number of pixels, CCD size, sensitivity, signal to noise ratio, etc., in which the number of pixels and CCD size are important indicators. The number of pixels refers to the number of photosensitive elements on the CCD. The picture taken by the camera can be understood as consisting of a number of small dots, each of which is a pixel. Obviously, the more the number of pixels, the clearer the picture will be. If the CCD does not have enough pixels, the sharpness of the captured picture will be greatly affected. Therefore, the theoretical number of pixels of the CCD should be as good as possible. However, the increase in the number of CCD pixels will reduce the manufacturing cost and the yield. Moreover, under the current TV standard, after the number of pixels is increased to a certain amount, the effect of increasing the sharpness of the captured image becomes less obvious. Approximately a million pixels is sufficient for general use.

A single CCD camera means that there is only one CCD in the camera and it is used for photoelectric conversion of luminance signals and color signals. The chrominance signals are completed by using some specific color mask devices on the CCD and combining the following circuits. Since a CCD completes the conversion of the luminance signal and the chrominance signal at the same time, it is inevitable that the two images are completely perfect, so that the captured image does not meet the professional level requirement in color reproduction. In order to solve this problem, a 3CCD camera appeared. 3CCD, as the name suggests, is a camera using three CCDs. We know that if light passes through a special prism, it will be divided into three colors: red, green and blue. These three colors are the three primary colors used by our TV. Through these three primary colors, we can generate the brightness signal. All TV signals inside. If a single CCD is used to receive each color and converted into an electrical signal, and then processed by the circuit to generate an image signal, thus a 3CCD system is constructed.

Compared with the single CCD, since the 3CCD converts the red, green and blue signals with 3 CCDs respectively, the captured image is more natural than the single CCD, and the brightness and sharpness are better than the single CCD. However, due to the use of three CCDs, the price of a 3CCD camera is much more expensive than a single CCD.

The CCD column in the digital camera specification sheet often says "1/2.7 inch CCD". The "1/2.7 inch" here is the size of the CCD, which is actually the length of the CCD diagonal.

Existing digital cameras generally use CCDs of sizes 1/2.7 inch, 1/2.5 inch, and 1/1.8 inch. The CCD is an aggregate of light-receiving elements (pixels) that receive light transmitted through the lens and convert it into an electrical signal. In the case of the same number of pixels, the larger the CCD size, the larger the unit pixel. In this way, the unit pixel can collect more light, so in theory, it can be said that it is beneficial to improve the image quality.

However, the quality of digital cameras is not only determined by CCD. The performance of the circuit, such as the lens and the electrical signals output by the CCD, can also affect the image quality of the camera. The so-called "large size CCD = high image quality" is not correct. For example, although 1/2.7 inch is smaller than 1/1.8 inch, digital cameras equipped with 1/2.7 inch CCD are not criticized for poor quality.