Automotive Laser Speed Detection System

Automotive Laser Speed Detection System

With the development of the information society, people's living standards continue to improve, traffic management is in urgent need of running car detection, especially on the car speed to have an effective means of detection, which is also an important part of the modern intelligent transportation system.

Detecting automobile speed, the more commonly used is microwave radar speed measurement, which has a large detection range, but the accuracy value of its detection speed is poor, thus the need to develop automobile laser speed measurement system.

Components and Principles of Automotive Laser Speed Detection System

Phase-method laser velocimetry has high measurement accuracy and is suitable for observing terrain and wave undulations where higher accuracy is required, but it has very stringent requirements for optical paths and is complex to design. For civil traffic speed measurement, in the remote and precision is not high, the pulse method laser speed measurement power is larger, the system is simpler than the phase method, easy to realize, more easy to operate, the whole system is easier than other methods to achieve the user's needs. Therefore, applied in traffic control such as electronic police, pulse method and laser speed measurement method is undoubtedly the best one.

Components of an automotive laser speed measurement system

The automotive laser pulse speed measurement system is mainly composed of 3 main parts: optical system, hardware circuit and software processing. Among them, the optical system consists of optical collimation part and spectroscopic system; the hardware circuit consists of transmitting module (including pulse driving circuit), receiving module and computer interface circuit; the software processing part consists of CPLD pulse driving, technical program and MCU serial port program, as well as the communication processing part with the host computer.

The laser transmitter module consists of a pulse driver circuit, a laser, and a transmitter optical system; the laser receiver module consists of a receiver optical system, a photodetector, a signal amplifier, a shaping filter circuit, and a counting interface circuit. In addition, the laser power supply consists of 160V high voltage power supply and 12V and 5V low voltage power supply.

The working principle of the automotive laser pulse speed measurement system, is through the double glued lens, the laser issued by the pulse light focusing for parallel light emission (i.e., laser collimation system), and then a part of the light through the beam splitter mirror to the photodetector, then the beginning of the timekeeping moment for t1, most of the light through the convergence of double glued lens shot to the target point, the target reflected back to the scattered light first through the narrow-band filter filtering out the clutter, and then by the double glued lens will be the weak reflection of the light to the convergence of the photoelectric photodetector to the small area of the moment, then the end of the timekeeping moment, the moment for t2.

It is worth noting that weather is an important constraint on laser speed measurement, such as in foggy weather when the laser speed measurement is less effective. Because there is diffuse reflection on the way of laser pulse propagation, the laser pulse should have enough intensity in order to expand the measurement range and improve the measurement accuracy. No matter how to improve the directionality of the beam, it is inevitable that there will be a certain degree of dispersion, coupled with the absorption and scattering of light by the air, the further the target is, the weaker the light energy reflected back. Therefore, in order to measure a longer distance, on the one hand, the light source should be made to emit light intensity with higher power density; on the other hand, the directionality of the laser pulse is required to be good. In this way, the light energy can be concentrated in a smaller dispersion angle to shoot farther away, the spot is smaller, which can also accurately determine the location of the target.

Although the above two measures can expand the measurement range, but to improve the measurement accuracy, the laser pulse also has the following three requirements.
1. The monochromaticity of the laser pulse should be good. Because day or night, there will always be a variety of scattered light in the air, which is often much stronger than the reflected light signal. Therefore, the better the monochromaticity of the laser pulse, the better the effect of the narrow-band filter, the more effective way to improve the signal-to-noise ratio of the receiving system to ensure the accuracy of the measurement.
2. The width of the laser pulse should be narrow, that is, the pulse rise time and duration should be short. Because the speed of light is extremely fast, the optical round-trip time is extremely short, the optical pulse period should be at least far less than the optical round-trip time in order to measure properly, and reduce the measurement error, but also to improve the signal-to-noise ratio of the system.

3. The response speed of the received detector should be fast enough. This allows the pulse signal to be extracted efficiently.

CLZ Optical Co., Ltd. is a company specializing in the production of optical components, from design to production, sales integration, the main products include optical dome, optical window, optical prism, we can also provide coating technology, customized service, according to the customer's needs for their customized products. The double glued lenses mentioned in the above article are also our main products, through advanced production equipment, high precision production technology, professional inspection equipment. If you need please feel free to contact us.