Design of a vehicle-mounted infrared night vision device based on PIC16F877A single-chip microcomputer

0 Introduction
With the rapid development of the automobile market and the increasing awareness of security, people have higher and higher requirements for automobile safety protection technology. The existing automobile lighting system has the disadvantages of short visibility and poor effect in low visibility conditions such as snowy nights, snowy days or heavy fog, which has become one of the safety hazards of automobile driving. What is more serious is that when driving at night, drivers are usually distracted by the lights of other vehicles and have blind spots, which is prone to car accidents. The night vision system can help drivers navigate in the dark, allowing drivers to see the driving environment clearly in both light and dark conditions. Therefore, the development of an automobile infrared night vision system with simple structure, stable performance, good reliability and strong applicability has important market application prospects.

1 System overall design
1) System principle
According to different working principles, infrared night vision systems are divided into passive infrared night vision systems and active infrared night vision systems. The active infrared night vision system uses the infrared light source it carries to actively illuminate the target. The objective lens of the optical system receives the infrared radiation reflected by the target and forms an infrared image of the target radiation on the photocathode surface of the infrared image converter. The image converter performs spectral conversion and brightness enhancement on the infrared image of the target, and finally displays the visible light image of the target on the fluorescent screen. The human eye can observe the enhanced target image through the eyepiece. Considering the durability of use, economic rationality, versatility of devices, etc., most people choose active infrared night vision systems as vehicle-mounted systems.
According to functional objectives and design requirements, this system is mainly composed of infrared irradiation lamps, CCD cameras, video processing systems and vehicle-mounted displays.
2) Hardware design
(1) Camera selection
The camera is also called a camera or CCD. It can convert light into electric charge and store and transfer electric charge. It can also remove the stored charge to change the voltage. It is an ideal camera element. Its working principle is: the light reflected by the camera body is transmitted to the lens and focused on the CCD chip through the lens. The CCD accumulates corresponding charges according to the intensity of the light, and generates electrical signals representing the pictures through periodic discharge. After filtering and amplification, a standard composite video signal is output through the output terminal of the camera. Here, the WAT-902H2 camera is selected as the camera. It has the advantages of good camera effect, easy maintenance and economical.
(2) Design of infrared irradiation part
A far-infrared laser is selected as the light emitter. It is a laser emitter with good monochromaticity, concentrated beam, small size, long life and high electro-optical conversion efficiency. It consists of a fiber-coupled semiconductor laser, a drive circuit, a temperature control circuit and a beam shaping lens. The core part is the drive circuit design. DD312 is selected as the drive chip. It is a single-channel constant current drive chip designed for high-power LEDs. It has a current absorption architecture and can provide a maximum constant current output of 1A. It also supports the enable end switch function. The microcontroller command signal is added to the enable end of DD312 through an optical coupler to control the switch of the laser. The driving circuit is shown in Figure 1.

(3) Design of power supply module
The display, microcontroller, MAX487 communication chip, CCD camera, and laser transmitter drive circuit in the system all need power supply. The microcontroller and DD312 driver chip require relatively stable power supply voltage, small ripple, and small electromagnetic interference. The LM2576 module is used to provide a regulated power supply for the microcontroller and DD312 driver chip (Figure 2). The operating voltage of the MAX4877 chip is relatively high and the range is relatively wide. The NW1-05S05S power conversion module is used to provide power for it.
(4) Design of control system
Two microcontrollers, PIC16F877A and PIC16F876A, are used as the control chips of the system. The entire control system is also a small transmission system. The PIC16F877A microcontroller is the initial end of the transmission system, responsible for data acquisition and "memory" buttons; the Max487 chip is a communication chip, responsible for receiving and transmitting signals. The PIC 16F876A microcontroller is the receiving end of the transmission system, controlling the rotation of the motor. [page]

0 Introduction
With the rapid development of the automobile market and the increasing awareness of security, people have higher and higher requirements for automobile safety technology. The existing automobile lighting system has the disadvantages of short visibility and poor effect in low visibility conditions such as snowy nights, snowy days or heavy fog, which has become one of the safety hazards of automobile driving. What is more serious is that when driving at night, drivers are usually distracted by the lights of other vehicles and have blind spots, which is prone to car accidents. The night vision system can help drivers navigate in the dark, allowing drivers to see the driving environment clearly in both light and dark conditions. Therefore, the development of an automobile infrared night vision system with simple structure, stable performance, good reliability and strong applicability has important market application prospects.

1 System overall design
1) System principle
According to different working principles, infrared night vision systems are divided into passive infrared night vision systems and active infrared night vision systems. The active infrared night vision system uses the infrared light source it carries to actively illuminate the target. The objective lens of the optical system receives the infrared radiation reflected by the target and forms an infrared image of the target radiation on the photocathode surface of the infrared image converter. The image converter performs spectral conversion and brightness enhancement on the infrared image of the target, and finally displays the visible light image of the target on the fluorescent screen. The human eye can observe the enhanced target image through the eyepiece. Considering the durability of use, economic rationality, versatility of devices, etc., most people choose active infrared night vision systems as vehicle-mounted systems.
According to functional objectives and design requirements, this system is mainly composed of infrared irradiation lamps, CCD cameras, video processing systems and vehicle-mounted displays.
2) Hardware design
(1) Camera selection
The camera is also called a camera or CCD. It can convert light into electric charge and store and transfer electric charge. It can also remove the stored charge to change the voltage. It is an ideal camera element. Its working principle is: the light reflected by the camera body is transmitted to the lens and focused on the CCD chip through the lens. The CCD accumulates corresponding charges according to the intensity of the light, and generates electrical signals representing the pictures through periodic discharge. After filtering and amplification, a standard composite video signal is output through the output terminal of the camera. Here, the WAT-902H2 camera is selected as the camera. It has the advantages of good camera effect, easy maintenance and economical.
(2) Design of infrared irradiation part
A far-infrared laser is selected as the light emitter. It is a laser emitter with good monochromaticity, concentrated beam, small size, long life and high electro-optical conversion efficiency. It consists of a fiber-coupled semiconductor laser, a drive circuit, a temperature control circuit and a beam shaping lens. The core part is the drive circuit design. DD312 is selected as the drive chip. It is a single-channel constant current drive chip designed for high-power LEDs. It has a current absorption architecture and can provide a maximum constant current output of 1A. It also supports the enable end switch function. The microcontroller command signal is added to the enable end of DD312 through an optical coupler to control the switch of the laser. The driving circuit is shown in Figure 1.

(3) Design of power supply module
The display, microcontroller, MAX487 communication chip, CCD camera, and laser transmitter driver circuit in the system all need power supply. The microcontroller and DD312 driver chip require relatively stable power supply voltage, small ripple, and small electromagnetic interference. The LM2576 module is used to provide a regulated power supply for the microcontroller and DD312 driver chip (Figure 2). The operating voltage of the MAX4877 chip is relatively high and the range is relatively wide. The NW1-05S05S power conversion module is used to provide power for it.
(4) Design of control system
Two microcontrollers, PIC16F877A and PIC16F876A, are used as the control chips of the system. The entire control system is also a small transmission system. The PIC16F877A microcontroller is the initial end of the transmission system, responsible for data acquisition and "memory" buttons; the Max487 chip is a communication chip, responsible for receiving and transmitting signals. The PIC 16F876A microcontroller is the receiving end of the transmission system, controlling the rotation of the motor.

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2 Experimental results
Figure 7 shows a picture taken on the highway. a is a picture without the night vision system, and b is a picture with the night vision system. The experimental results show that this system can enable drivers to accurately identify the road ahead in the dark and reduce traffic accidents.

3 Conclusion
This paper uses PIC microcontroller to design a complete set of infrared night vision system, which has the advantages of simple structure and high reliability. It is particularly suitable for long-distance driving, can effectively reduce traffic accidents, and has very good social benefits.