Camera module introduction(1)
August 11, 2021
Camera module introduction:
1、Camera module, full name CameraCompact Module, hereinafter abbreviated as CCM, is an important electronic device for image capture.
2. The working principle of the camera, the role of the components of the camera
If you want to fully understand it, you have to go deeper. If it is code, we will analyze it step by step. If it is a module, we will break it down to see how it works. Take a look at what parts it is composed of, as shown in the figure below:
(1) Working principle: The light gathered by the object through the lens (lens) converts the light signal into an electrical signal through the CMOS or CCD integrated circuit, and then converts it into a digital image signal through the internal image processor (ISP) and outputs it to the digital signal The processor (DSP) is processed and converted into standard GRB, YUV and other format image signals.
(2) CCM contains four major parts: lens, sensor, soft board (FPC), image processing chip (DSP). The important components that determine the quality of a camera are: lens (lens), image processing chip (DSP), and sensor (sensor). The key technologies of CCM are: optical design technology, aspheric mirror manufacturing technology, and optical coating technology.
The lens is the soul of the camera.
The lens plays an important role in the imaging effect. It uses the principle of refraction of the lens. The light from the scene passes through the lens to form a clear image on the focal plane. It is passed through the photosensitive material CMOS or CCD. The photoreceptor records the image of the scene.Lens manufacturers are mainly concentrated in Taiwan, Japan and South Korea. Lens, an industry with high optical technology content, has a relatively high threshold. Well-known companies in the industry such as Fuji Seiki, Konica Minolta, Largan, Enplas, etc.
The sensor is the core module of CCM. There are currently two widely used: one is the widely used CCD (charge coupled) component; the other is the CMOS (complementary metal oxide conductor) device.
The charge coupled device image sensor CCD (Charge Coupled Device), which is made of a high-sensitivity semiconductor material, can convert light into electric charge, which is converted into a digital signal through an analog-to-digital converter chip.CCD is composed of many photosensitive units, usually in millions of pixels.When the surface of the CCD is illuminated by light, each photosensitive unit will reflect the charge on the component, and the signals generated by all the photosensitive units are added together to form a complete picture.CCD sensor modules are dominated by Japanese manufacturers, and more than 90% of the global market is monopolized by Japanese manufacturers, led by Sony, Panasonic, and Sharp.
Complementary Metal-Oxide Semiconductor CMOS (Complementary Metal-Oxide Semiconductor) is mainly a semiconductor made of the two elements of silicon and germanium, making it coexist with N (charged-charged) and P (charged + charged) on the CMOS For advanced semiconductors, the current generated by these two complementary effects can be recorded and interpreted into images by the processing chip.CMOS sensors are mainly led by the United States, Taiwan and South Korea. The main manufacturers include OmniVision, Agilent, Micron from the United States, Sharp Image, Original Phase, and Taishi from Taiwan, and Samsung and Hyundai from South Korea.
The image processing chip (DSP) is an important part of CCM. Its function is to transfer the data obtained by the photosensitive chip to the central processing unit and refresh the photosensitive chip in a timely and fast manner. Therefore, the quality of the DSP chip directly affects the picture quality (such as color saturation). Degree, clarity, etc.).
FPC flexible circuit board (flexible PCB): referred to as "soft board", also known as "flexible circuit board", which connects the chip and the mobile phone. Play the role of electrical signal transmission.
3. How to assemble the camera module
(1) Assembly drawing of fixed focus module
CCM is divided into fixed focus module and automatic zoom module. The fixed focus module is mainly assembled by lens, lens holder, photosensitive integrated circuit, flexible circuit board, reinforcement and steel sheet. The assembly diagram is as follows:
(2) Assembly drawing of automatic zoom module
The automatic zoom module consists of a lens, a voice coil motor, a base bracket, a photosensitive integrated circuit, a driving integrated circuit and a connector. The assembly diagram is as follows:
4. Some technical indicators of the camera
(1) Image resolution/resolution (Resolution)
(2) Image format (imageFormat/Colorspace)
RGB24, 420 are currently the two most commonly used image formats.
RGB24: It means that the three colors of R, G, and B are 8bit each, and can express up to 256 shades, so that 256*256*256 colors can be reproduced.
I420: One of the YUV formats. Other formats are: RGB565, RGB444, YUV4:2:2, etc.
(3)automatic white balance adjustment (AWB)
Definition: It is required that the image on the screen should also be white when the object is illuminated in a different color temperature environment.The color temperature represents the spectral components, the color of light. Low color temperature means more long-wave light components.When the color temperature changes, the ratio of the three primary colors (red, green, and blue) in the light source will change, and the ratio of the three primary colors needs to be adjusted to achieve the color balance. This is the reality of white balance adjustment.
(4) Image compression method
JPEG: (joint photo graphicexpert group) static image compression method.A compression method for lossy images. The larger the compression ratio, the worse the image quality.This format can be selected when the image accuracy is not high and the storage space is limited. Most digital cameras currently use the JPEG format.
(5) color depth (color digits)
Reflecting the ability of color recognition and the color performance of imaging, it is actually the quantization accuracy of the A/D converter, which refers to how many levels the signal is divided into. Commonly used color digits (bit) said.The higher the color depth, the brighter and more attractive the color of the image obtained. Now the cameras on the market have reached 24-bit, some even 32-bit.
(6) Image noise
Refers to the noise and interference in the image. Appears as a fixed color noise in the image.
(7) Angle of view
Imaging with the human eye is based on the principle of mutuality, which is simply the imaging range.
Serial interface (RS232/422): The transmission rate is slow, 115kbit/s
Parallel interface (PP): the rate can reach 1Mbit/s
Universal Serial Bus USB: A plug-and-play interface standard that supports hot plugging. USB1.1 rate can reach 12Mbit/s, USB2.0 can reach 480Mbit/s
IEEE1394 (FireWire) interface (also known as ilink): its transmission rate can reach 100M~400Mbit/s