Camera module (CCM) and coating
November 28, 2022
Camera module (CCM) and coating
Mobile phone lenses are colored, and different mobile phone lenses have different colors, some are red, some are blue, and some are gold.
In addition to mobile phone lenses, the lenses of digital camera lenses, telescopes, glasses, etc. are all colored. These colors are mainly due to the fact that the surface of the lens has a thin layer of coating, so the surface of the lens will display different colors and use different coatings. The coatings of various colors of the lens play a very important role in the imaging of the lens.
The main function of coating
1. Antireflection. When the light passes through the lens, about 4%-10% of the light will be reflected by the lens (the reflectivity of the plastic lens will be higher). 90% light transmittance, but the general lens is composed of several lenses, and the lens is composed of multiple lenses, and only about 50% of the light reaching the sensor is left.
The light that is reflected inside the lens is also repeatedly reflected inside the lens, eventually forming a flare or ghost image on the sensor. How to increase the light transmittance is a very important issue. The commonly used method is to add a layer of coating on the surface of the lens. These coatings can greatly increase the light transmittance of a certain spectrum.
The light that needs to be enhanced is often not monochromatic, but has a certain bandwidth. A single-layer anti-reflection coating can only have a complete anti-reflection effect on monochromatic light of a certain wavelength. Multilayer coating techniques are required to improve AR light coverage. In addition, the different reflectivity of each layer of coating can also increase the amount of light passing through.
When looking at the surface of the lens, the color you see is the light that is reflected back. The less light is reflected back, the more effective the coating is.
2. Color correction. Due to the material or certain components in the lens, the lens may have a high absorption rate of certain colors, resulting in a color cast in the final image. In order to eliminate this chromatic aberration, lens manufacturers will add some other color coatings, such as amber, cyan, purple or blue coatings, on the basis that the lens does not produce additional glare and ghost images. These coatings can balance the final appearance of the lens. Image color.
Camera module (CCM) introduction:
1. Camera close-up
Camera module, full name CameraCompact Module, referred to as CCM, image capture electronic device. .
2. Camera principle and camera components
(1) Working principle: The light gathered by the object through the lens (lens) converts the optical signal into an electrical signal through a CMOS or CCD integrated circuit, and then converts it into a digital image signal through the internal image processor (ISP) and outputs it to digital signal processing Processor (DSP) processing, converted into standard GRB, YUV and other format image signals.
(2) CCM consists of four major components: lens (lens), sensor (sensor), soft board (FPC) and image processing chip (DSP). The important components that determine the quality of a camera are: the lens (lens), the image processing chip (DSP), and the sensor (sensor). The key technologies of CCM are: optical design technology, aspheric mirror manufacturing technology, and optical coating technology.
The lens (lens) is the soul of the camera. The lens (lens) plays a very important role in the imaging effect. It uses the refraction principle of the lens. The scene light passes through the lens and forms a clear image on the focal plane. 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, and Enplas.
Sensor (sensor) is the core module of CCM, and there are two types widely used at present: one is the widely used CCD (charge coupled) element; the other is CMOS (complementary metal oxide conductor) device.
Charge Coupled Device image sensor CCD (Charge Coupled Device), made of a high-sensitivity semiconductor material, can convert light into electric charge, and convert it into a digital signal through an analog-to-digital converter chip. CCD is composed of many photosensitive units, usually in megapixels. When the surface of the CCD is irradiated by light, each photosensitive unit will reflect the charge on the component, and the signals generated by all 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 scale 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 two elements, silicon and germanium, so that N (charge-charge) and P (charge + charge) coexist on CMOS. )-level semiconductors, the current generated by these two complementary effects can be recorded and interpreted into images by the processing chip. The main manufacturers of CMOS sensors include Largan, Sunny Technology, OFILM, OmniVision, Agilent, Micron, Sharp Image, Original Phase, Taishi, Samsung, etc.
The image processing chip (DSP) is an important part of CCM. Its function is to transmit 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, clarity, etc.).
FPC flexible circuit board (flexible PCB): referred to as "soft board", also known as "flexible circuit board", which connects chips and mobile phones. Play the role of electrical signal transmission.
3. Assembly method of camera module
(1) Assembly drawing of fixed focus module
CCM is divided into a fixed-focus module and an automatic zoom module. The fixed-focus module is mainly composed of a lens, a mirror holder, a photosensitive integrated circuit, a flexible circuit board, reinforcement and steel sheets.
(2) Automatic zoom module assembly
There is a voice coil motor inside, which is only available in high-resolution modules.
The automatic zoom module consists of a lens, a voice coil motor, a base bracket, a photosensitive integrated circuit, a driver integrated circuit and a connector.
(3) 3D modules
3D is shooting with multiple cameras.
Second, the working principle of the camera
The composition and working principle of the camera module are discussed above. Let's analyze how the camera works from the perspective of the register. How to read the camera specifications (key parameters are used for drive adjustment, take GT2005 as an example).
Specifications, that is, all descriptions of a device, are accurate to every detail of the device, registers that software cares about, electrical characteristics that hardware cares about, packaging, and so on. In terms of drivers, only look at the useful aspects, there is no need to read them all.
The control part is to power on the camera, IIC control interface, and the data output is to transmit the pictures taken by the camera to the main control chip, all of which must have data, field synchronization and clock number. The image sensor chip with CMOS interface can sense external visual signals, convert them into digital signals and output them.
VCM (Voice Coil Motor) voice coil motor
The full name is Voice Coil Montor, a voice coil motor in electronics, which is a kind of motor. Because the principle is similar to that of a speaker, it is called a voice coil motor, which has the characteristics of high frequency response and high precision. Its main principle is to control the stretching position of the spring leaf by changing the DC current of the inner coil of the motor in a permanent magnetic field, thereby driving up and down movement. Mobile phone cameras widely use VCM to realize the auto-focus function, through which the position of the lens can be adjusted to present a clear image.
VCM performance index
The performance of VCM mainly depends on the ratio of current to travel distance. Starting from the starting current, the current rise should be proportional to the travel distance that can be driven. The smaller the required rising current, the higher the accuracy. At the same time, it also depends on the maximum power consumption, maximum power, and size.
From the structure can be roughly divided into three categories: (1) shrapnel structure; (2) ball structure; (3) friction structure.
In terms of function, it can be roughly divided into five categories: (1) Open loop open motor; (2) Close loop closed-loop motor; (3) Alternate mid-mounted motor; (4) OIS optical image stabilization motor (divided into translation type, shifting shaft type, Memory metal type, etc.); (5) OIS+Close loop six-axis motor.