According to the photosensitive device it uses, there are CCD and CMOS: CCD (Charge Coupled Device) is made of a high-sensitivity semiconductor material, which can convert light into electric charge through analog-to-digital converter The chip is converted into a digital signal. After the digital signal is compressed, it is stored in the camera's internal flash memory or built-in hard disk card. Therefore, the data can be easily transmitted to the computer, and the image can be modified according to needs and imagination with the help of computer processing methods. The CCD is composed of many photosensitive units. 

When the surface of the CCD is illuminated by light, each photosensitive unit will reflect the charge on the component. The signals generated by all the photosensitive units are added together to form a complete picture. It is like the photosensitive system of a traditional camera's film. It is a circuit device that senses light. You can imagine it as tiny sensing particles, spreading behind the optical lens. When the light and image pass through the lens and project to When the surface of the CCD is used, the CCD will generate an electric current to convert the sensed content into digital data for storage. The larger the number of CCD pixels and the larger the size of a single pixel, the clearer the collected image will be. Therefore, although the number of CCDs is not the only key to determining image quality, we can still regard it as one of the important criteria for camera level. At present, most scanners, camcorders and digital cameras are equipped with CCDs.

After 35 years of development, the general shape and mode of operation of the CCD have been finalized. The composition of the CCD is mainly composed of a mosaic-like grid, a condenser lens, and an electronic circuit matrix at the bottom. The companies currently capable of producing CCDs are: SONY, Philps, Kodak, Matsushita, Fuji and Sharp, most of which are Japanese manufacturers.

CMOS (Complementary etal-Oxide Semiconductor, additional metal oxide semiconductor components), like CCD, is a semiconductor that can record light changes in digital cameras. The manufacturing technology of CMOS is no different from that of general computer chips. It mainly uses semiconductors made of silicon and germanium to make it coexist with N (charged-charged) and P (charged + charged) grades on CMOS. In semiconductors, the current generated by these two complementary effects can be recorded and interpreted into images by the processing chip. However, the disadvantage of CMOS is that it is too prone to noise. This is mainly because the early design made CMOS overheat due to the frequent current changes when processing fast-changing images.

The pros and cons of CCD and CMOS, we can compare the main differences between the two from a technical point of view:

Information is read in different ways. The charge information stored in the CCD sensor needs to be read after the synchronization signal controls the next bit to be transferred. The charge information transfer and read output require a clock control circuit and three sets of different power supplies, and the whole circuit is more complicated. The CMOS sensor directly generates a current (or voltage) signal after photoelectric conversion, and the signal reading is very simple.

The speed is different. The CCD sensor needs to output information bit by bit in a line unit under the control of a synchronized clock, and the speed is slow; while the CMOS sensor collects the light signal, it can extract the electrical signal and process the image information of each unit at the same time. Much faster than CCD.

Power supply and power consumption. Most CCD sensor charge couplers need three sets of power supplies and consume a lot of power; CMOS sensors only need one power supply, and the power consumption is very small, only 1/8 to 1/10 of CCD charge couplers, CMOS photoelectric sensors It has great advantages in energy saving.

Image quality. CCD sensor manufacturing technology started earlier, and the technology is relatively mature. It uses PN combined with a silicon dioxide isolation layer to isolate noise, and the imaging quality has certain advantages over CMOS sensors. Due to the high integration of CMOS sensors, the distance between the photoelectric sensor element and the circuit is very close, the optical, electrical, and magnetic interference between each other is more serious, and noise has a great impact on image quality. 

At the same resolution, CMOS is cheaper than CCD, but the image quality produced by CMOS devices is lower than CCD. So far, most consumer-level and high-end digital cameras on the market use CCD as sensors; CMOS sensors are used in some cameras as low-end products. Whether it has a CCD sensor or not has once become one of the criteria for people to judge the grade of a digital camera. Since the manufacturing cost and power consumption of CMOS are much lower than that of CCD, many mobile phone manufacturers use CMOS lenses. Now, most mobile phones on the market use CMOS cameras, and a few also use CCD cameras.

Principles of optical zoom and digital zoom

Optical zoom (Optical Zoom) is produced by changes in the positions of the lens, object, and focus. When the imaging surface moves in the horizontal direction, as shown in the figure below, the vision and focal length will change, and the farther scene will become clearer, which makes people feel like objects are progressive.

Obviously, there must be two ways to change the angle of view, one is to change the focal length of the lens. In photography terms, this is optical zoom. The focal length of the lens is changed by changing the relative position of each lens in the zoom lens. The other is to change the size of the imaging surface, that is, the diagonal length of the imaging surface. In current digital photography, this is called digital zoom. In fact, digital zoom does not change the focal length of the lens, but only changes the angle of view by changing the angle of the imaging face, thus producing an effect that is "equivalent to" the focal length of the lens.

Therefore, we see that some digital cameras with longer lenses have more room for movement of the internal lenses and photoreceptors, so the zoom factor is also larger. We see that some ultra-thin digital cameras on the market generally do not have an optical zoom function, because the roots of the fuselage do not allow the movement of photosensitive devices, while the "long lens" digital cameras such as Sony F828 and Fuji S7000 have optical zoom The function reaches 5 or 6 times.

Digital zoom (DigitalZoom) is also known as digital zoom. Digital zoom uses the processor in the digital camera to increase the area of each pixel in the picture to achieve the purpose of magnification. This method is like using image processing software to increase the area of the picture, but the program is carried out in a digital camera, and a part of the pixels on the original image sensor is enlarged using "interpolation" processing methods to enlarge the pixels on the image sensor Use interpolation algorithm to enlarge the picture to the whole picture.

Different from optical zoom, digital zoom is a change in the vertical direction of the photosensitive device, which gives people a zoom effect. The smaller the area on the photosensitive device, the visually will allow the user to see only a part of the scene. However, since the focal length has not changed, the image quality is worse than normal.

Through the digital zoom, the shooting scene is enlarged, but its sharpness will be reduced to a certain extent, so the digital zoom does not have much practical significance. Because too much digital zoom will seriously damage the image, and sometimes even because the magnification is too high, it is difficult to distinguish the captured images.

Sensor internal working principle

After the external light passes through the lens, it is irradiated on the Sensor surface after being filtered by the color filter. The Sensor converts the light conducted from the lens into an electrical signal, and then converts it into a digital signal through the internal DA. If the Sensor does not integrate DSP, it will be transmitted to the baseband through DVP, and the data format at this time is RAW RGB.

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