Camera Module (CCM) Introduction(2)
September 1, 2021
Camera Module (CCM) Introduction
As a necessary functional component of intelligent terminals such as computers, mobile phones, car assisted driving, video phones, security monitoring, etc., cameras have been closely related to our daily lives.
1: What is CCM?
Compact Camera Module
CMOS Camera Module
Cellphone Camera Module
2: The main components of CCM
Lens、IR Filter、Sensor IC、DSP、FPC
3: CCM classification
Divided by image sensor type:
CCD (Charge Couple Device), called charge coupled device;
CMOS (Complementary Metal Oxide Semiconductor), that is, complementary metal oxide semiconductor.
Comparison of CCD and CMOS:
According to the manufacturing process:
CSP(Chip Scale Package)
Features: Simple process, easy control of Partical, high yield; Cover Class layer on the surface of the imaging area, which increases the cost.
COB(Chip On Board)
Features: good light transmittance, small module thickness, small post-Lens requirements; large equipment investment, complex manufacturing process, and difficult yield control;
Divided by lens type:
FF(Fixed Focus) ；
MF(Manual Focus) ；
4: CCM related technologies and terminology
4.1 Focal length f
The focal length is a measure of the concentration or divergence of light in an optical system. It refers to the distance from the optical center of the lens to the focal point of the light when parallel light is incident, and is represented by f.
4.2 Field of view
4.3 Auto Focus (AF)
The automatic focusing method of the camera module is roughly divided into:
4.3.1 Contrast detection method
Traditional mobile phone cameras use a contrast focusing system for focusing. The principle is to find the position of the lens when the contrast is the largest, that is, the position of accurate focusing, according to the change in the contrast of the image at the focal point.
a. In the out of focus state, because the entire focus picture is in a virtual focus state;
b. Start to focus, the lens starts to move, the picture gradually becomes clear, and the contrast starts to rise;
c. In the focus state, the picture is clearest and the contrast is the highest, but the mobile phone does not know it, so it will continue to move the lens;
d. Continue to move the lens and find that the contrast starts to drop. Move the lens further and find that the contrast has dropped further, and the phone knows that it has missed the focus;
e. The lens returns to the position with the highest contrast to complete focusing.
4.3.2 Phase detection method (PDAF)
The phase detection focusing system is a very popular focusing method on SLR cameras. It is characterized by fast focusing speed, and it is not easy to lose focus when capturing or shooting moving objects. The disadvantage is that it is easy to focus failure under low light conditions.
The image sensor used in the phase detection focusing system is a bit different. Some pixels in the photosensitive area are sacrificed. These pixels are called masked pixels and are used in pairs. The distance between the pixels, combined with their relative changes, can help the system determine how far the lens needs to be moved for accurate focus.
Masked Pixels are composed of two pixels. The left pixel only captures the left image, and the right pixel only captures the right pixel. Comparing the values of the left image and the right image can determine that the lens should move forward or backward. When these two values are the same, it means that the lens is in focus.
PDAF usually uses a lens splitter system. In layman's terms, it divides the light into two beams and irradiates them to the corresponding pixels on both sides. The detection signal and the algorithm cooperate to determine the accurate focus position. Compared with contrast focusing, the position can be determined in 1-2 frames, and the focusing speed is self-evident.
4.4 Image Optical Stabilization (OIS)
OIS is short for Optical Image Stabilization System.It should first include a gyroscope that can sense hand shaking. The gyroscope measures the camera tilt angle caused by the hand shake, and the system predicts the image offset caused by the tilt based on the angle, and then the system controls the lens relative to the image The sensor is shifted to produce an image offset of the same size but in the opposite direction, thereby offsetting the image offset caused by hand shaking, ensuring that the camera can still maintain imaging stability in a hand shaking environment.