1. Hardware Overview
As a video input device, CAMERA is widely used in video conferencing, surveillance, mobile phone consumer products, etc.
There are three different definitions of CCM:
1) Compact camera module
2) CMOS camera module (Cmos CAMERA Module)
3) Cellphone Camera Module
The camera can be divided into digital (Digital Camera) and analog (Simulant CAMERA) according to the image processing method. At present, digital is widely used.
The digital camera directly integrates the camera unit and the video capture unit, and then connects to the HOST System through serial, parallel, or USB interfaces.
The main components of CCM: lens (Lens), infrared filter (IR Filter), image sensor (Sensor IC), digital signal processing (DSP) and flexible board (FPC). Some of the Sensor ICs integrate DSPs, some do not integrate DSPs, and modules without integrated DSPs require external DSPs.
Commonly used Sensor ICs are integrated with DSP, such as OV3640 integrated with DSP. The raw data is converted into YUV or RGB format data after sensor processing.
Schematic diagram of a typical mobile phone camera module:
The role of the lens is to collect light and then image the object to the surface of the photosensitive chip to collect the light reflected by the object of interest (similar to the lens of our glasses).
The function of the sensor IC is to convert the optical signal sent by the upper lens of the surface into an electrical signal, and then we can get the photos we want by processing the electrical signal.
The function of the voice coil motor is to focus, and the lens can be easily moved so that we can get very clear photos and look comfortable.
The role of the filter is to filter out excess infrared light and ultraviolet light, so that the color of the photo taken is closer to the color seen by our eyes.
2. Hardware interface
The CAMERA controller is generally integrated inside the MCU, and the interface between the MCU and the camera module is generally DVP (Digital Video Port).
DVP consists of three parts: I2C (configuration initialization communication), parallel data line Data [0 ... 7] (transmit image data), clock signal and power supply.
MCLK camera main clock, HSYNC (row synchronization), VSYNC (column synchronization), PCLK (pixel clock).
The work of the camera is divided into three steps:
- Basic conditions such as power-on and clock of the camera;
- I2C guarantees the initialization of the camera;
- Data transmission.
The control part is the camera power-on, I2C control interface.
Data output is that the image data captured by the camera is transmitted to the main control chip, so Data, line sync clock, and PCLK pixel clock are required.
If it is a dual camera, the frame synchronization signal XVSYNC between the two cameras must be added.
reference:
1. Camera module knowledge introduction Baidu Library
2. Brief introduction of mobile phone camera module
3. Camera module basic literacy