As mentioned in the previous article“ ”Here we mainly talk about the physical components of the camera. Mobile phone camera is composed of PCB board, lens, holder and color filter, DSP (for CCD), sensor and other components. Its working principle is: shooting objects pass through the lens, and the generated optical image is projected onto the sensor, and then the optical image is converted into an electrical signal, which is then converted into a digital signal through analog digital conversion, and the digital signal is processed by DSP, and then sent to the mobile phone processor for processing, and finally converted into an image that can be seen on the mobile phone screen.
PCB board
It refers to the printed circuit board used in the camera, which is divided into three types: hard board, soft board and soft and hard combination board. The application range of these three materials is different. CMOS can use any one, but CCD can only use soft and hard combination board, and the cost of soft and hard combination board is the highest.
▲ PCB board
camera lens
The lens is a device that images the photographed object on the sensor. It is usually composed of several lenses. From the material point of view, the camera lens can be divided into plastic lens and glass lens. Glass transparency and imaging quality have great advantages, but the cost of glass lens is also high. Therefore, the quality of a camera has something to do with the lens. For example, the Nokia 800 uses a Carl Zeiss certified lens, and the imaging effect will be better than ordinary lenses. Of course, it is only one of the factors affecting the overall effect.
camera lens
Lens has two important parameters: aperture and focal length. Aperture is a device installed on the lens to control the amount of light passing through the lens to the sensor. In addition to controlling the amount of light, the aperture also has the function of controlling the depth of field. The larger the aperture, the smaller the depth of field. Usually, when shooting portraits, the dim background effect is a manifestation of the small depth of field. The aperture of the Nokia 800 and Meizu MX quad core versions is f/2.2, the aperture of Xiaomi 2 is f/2.0, and the aperture of the iPhone 4S is f/2.4. The smaller the number, the larger the aperture. That is to say, Xiaomi 2 has the largest aperture. Without other factors, the imaging effect is best in theory.
Another important parameter of the lens is "focal length". The focal length is the distance from the center point of the lens to the clear image formed on the sensor plane. According to the imaging principle, the focal length of the lens determines the size of the image formed by the object photographed by the lens on the sensor. For example, when shooting the same object, the longer the focal length is, the larger the image of the object can be captured. Long focal length is similar to telescope.
Holder and color filter
The function of the holder is actually to fix the lens. In addition, there is a color filter on the holder. Color filter is also called "color separation filter". At present, there are two color separation methods, one is RGB primary color separation, and the other is CMYK complementary color separation. The advantages of primary color CCD are sharp picture quality and true color, but the disadvantage is noise. For digital cameras that generally use primary color CCD, the ISO sensitivity will not exceed 400. In contrast, the complementary CCD has an additional Y yellow color filter, which sacrifices the resolution of some images, but the ISO value can generally be set above 800.
Holder and color filter
DSP
DSP is also called digital signal processing chip. Its function is to optimize the digital image signal through a series of complex mathematical algorithms, and finally transmit the processed signal to the display. At present, the design and production technologies of DSP manufacturers are relatively mature, and the technical indicators are not different.
Sensors and DSP
The DSP mentioned above will be used in CCD because its DSP chip has been integrated into CMOS in the camera of CMOS sensor. From the appearance, they are a whole. The camera with CCD sensor is divided into two independent parts, CCD and DSP.
sensor
The sensor is the core of the camera and the most critical technology. It is a device used to receive light passing through the lens and convert these light signals into electrical signals. In a simple understanding, we can regard the sensor as a film for traditional cameras. Although the principles of the two are different, there is a certain similarity in the overall composition of the camera.
The larger the area of the photosensitive device, the more photons captured, the better the photosensitive performance, and the lower the signal-to-noise ratio.
There are two common camera sensors, one is CCD sensor , one is CMOS sensor 。 The difference between the two is that CCD has the advantage of good imaging quality, but because of the complex manufacturing process, only a few manufacturers can master it, so the manufacturing cost remains high, especially for large CCD, the price is very high. At the same resolution, CMOS is cheaper than CCD, but the image quality produced by CMOS devices is lower than CCD.
sensor
Compared with CCD sensor, one of the advantages of CMOS image sensor is that its power consumption is lower than that of CCD. In order to provide excellent image quality, CCD pays the price of higher power consumption. In order to make charge transmission smooth and reduce noise, it is necessary to improve the transmission effect by high voltage difference. However, CMOS image sensor converts the charge of each pixel into voltage, amplifies it before reading, and can be driven by 3.3V power supply. The power consumption is lower than that of CCD.
In addition, it is occasionally mentioned CCM sensor CCM (Compact CMOS module) is actually a kind of CMOS, but after some processing, the image quality of CCM is higher than that of CMOS, and the sensing speed is faster when taking pictures, but the picture quality is still inferior to that of CCD.
At present, the mainstream mobile phones use CMOS sensors , such as Samsung Galaxy Note 2, iPhone 5, Xiaomi 2, Meizu MX quad core, Nokia Lumia 800, etc.
In addition, some manufacturers will mention the concepts of "back reflection" and "BSI" in their publicity. In fact BSI is back illuminated CMOS English abbreviation of, Backlit CMOS is a kind of CMOS , it improves the sensitivity of traditional CMOS sensor, and the imaging effect is relatively better in night photography and high sensitivity. For example, BSI sensors are used in iPhone 4, Meizu MX quad core, ZTE U895, Sony Ericsson LT15i and other machines, while the sensors of iPhone 4 are produced and provided by OmniVision.
In addition, Sony is also very famous among sensor manufacturers, The backlight CMOS (BSI) produced by Sony is named "Exmor R CMOS", and the next generation revolutionary build up CMOS is named "Exmor RS CMOS". The Exmor R CMOS sensor is used by Sony LT26i and HTC Triumph X310e.
From the above nouns, we know that Exmor R CMOS Exmor RS CMOS belongs to a kind of back illuminated CMOS (BSI), and back illuminated CMOS (BSI) belongs to a kind of CMOS. Conceptually, there should be no confusion.
