Design Of Wide Dynamic, Low Illumination Integrated Cameras Based On CMOS Image Sensor

At present, the integrated camera with reasonable price, good performance, installation easy and other advantages, they are widely used in the field of surveillance cameras. Using CCD image sensors to design integrated camera, the design is complex and cost is relatively high. The CMOS image sensor product technology is more and more matures, its performance has met or exceeded the CCD. Using CMOS image sensor develop for integrated camera can reduce the design complexity and cost of the product in the premise of ensuring high image performance. The integrated camera based on CMOS image sensor in surveillance system has great application value.In this paper, the scheme of "CMOS image sensor + FPGA + MCU" is adopted to design the 22 times PAL integrated camera. The whole design is divided into hardware circuit design and control programming design. The hardware circuit uses modular design method and the whole design is divided into four modules: image acquisition module, FPGA module, MCU control module and power module. This paper selects main chip according to the function of each module and complete the schematic design. PCB design is based on the signal integrity analysis, through the lumped circuit elements (resistors, capacitors and inductors) and transmission lines are equivalent, modeling and analysis, and thus the physical properties change into electrical model. Then, the equivalent electrical model is used to optimize the electrical properties of the entire design; so the problem of crosstalk, reflections and power distribution system orbital collapse in PCB design are solved. At the same time, effectively reducing the overall design of electromagnetic interference and radiation, and the final hardware circuit has stable performance. Control program is divided into CMOS image sensor initialization program, auto-focus program, OSD program and RS-485 Communication program. CMOS image sensor contains more than 400 internal control registers and variables, which registers and variables can be read and write through the I2C interface. Only those registers and variables are configured correctly, the image sensor can work according to design requirements. On the one hand, using I2C communication mechanisms of MCU, through the number of registers and variables correlated with each other configured to implement initialization of the sensor chip. Meanwhile, through the internal related command registers of the sensor chip to configuration and timing control of MCU to achieve OSD function. On the other hand, also in the MCU, SPI communication mechanism used to achieve communication between with the FPGA. The MCU reads the value of the focusing evaluation function of FPGA, combined with improved climbing search strategy to achieve the auto-focus; In addition, the microcontroller through the RS-485 communication mechanism to achieve remote monitoring and control.The dynamic range of the integrated camera designed in this paper up to 52dB, its minimum illumination is 0.09Lux, and it is cost-effective. Its parameters and performance meet the main parameters and performance indicators of the integrated cameras; it can be widely used in ports, video conferencing, intelligent transportation, intelligence community and other monitoring systems and its application prospect is better.