Radar and laser applications
Input and output interfaces
Input：
(1) Video image resolution (int int)
(2) Image video format (RGB, YUV, MP4, etc.)
(3) Camera calibration parameters (the center position (x, y) and five distortion
Coefficient (2 radially, tangentially 2, the rib 1), floating point type float)
(4) the camera initialization parameters (camera position and initial three coordinate directions
Rotation angle, vehicle speed, etc. width height, float float)
(5) information on lidar point cloud (cloud point coordinate position x, y, float float)
Output：
(1) The fused image video resolution (int int)
(2) The fused image of the video format (RGB, YUV, MP4, etc.)
(3) from the vehicle and the target (float float)
(4) the recognition target object (int int)
1. Function Definition
1) the object detection point cloud
2) the object recognition point clouds
3) a three-dimensional image reconstruction point clouds
4) point cloud object distance
2. Technology Roadmap program
Laser radar, is emitting a laser beam characteristic amount detecting target position, velocity, etc. of radar systems. Its working principle is to transmit the probe signal (laser beam) to a target, and then the signal (target received back from the target reflection echo ) compared with the transmitted signal, after suitable processing for the information, the target can be obtained, such as target distance, direction, altitude, speed, attitude, and even the shape and other parameters to the aircraft, missile target detection, tracking and identification. It consists of a laser transmitter, an optical receiver, turntable, and an information processing system , etc., the laser electrical pulses into light pulses emitted, the optical receiver from the target and then the reflected light pulses back into electrical pulses of the reduction, to a display.
definition
The LiDAR (Light Detection and the Ranging) , a light detection and ranging system referred to, also known as Laser Radar additionally or LADAR (Laser Detection and the Ranging) .
Using a laser as a radiation source, photodetection device using active remote sensing technologies means. Laser radar is an advanced technology and modern detection methods laser photoelectric detection technology combined. By the transmitting system, receiving system, information processing and other components. Emitting a laser system in various forms, such as the composition of a carbon dioxide laser, neodymium-doped yttrium aluminum garnet lasers, semiconductor lasers and tunable solid state laser and an optical beam expander means and the like; and a receiving system uses various forms of telescope photodetectors as photomultiplier, a semiconductor photodiode, an avalanche photodiode , infrared and visible light in combination a plurality of sensors and so on. Lidar using pulsed or continuous wave two kinds of work, in accordance with the principles of the detection method of detection can be divided into Mie scattering, Rayleigh scattering, Raman scattering, Brillouin scattering, fluorescence, etc. Doppler lidar.
Composition and principle
LIDAR is a set of laser, a global positioning system ( the GPS ) and inertial navigation system (INS) and a system three techniques for obtaining the data and generate accurate DEM. This combination of the three technologies, can be highly accurate positioning of the laser beam hitting a spot on the object. It consists of the current maturity for obtaining the digital elevation model (DEM) and topographic LIDAR system is ripe for underwater applications for obtaining hydrological DEM LIDAR system, a common feature of both systems is the use of laser detection and measurement, LIDAR which is the English translation of the original term, namely: LIght detection and Ranging - LIDAR.
Laser itself has a very accurate ranging capability, its ranging accuracy up to several centimeters, and the accuracy of the laser itself LIDAR system other factors, but also on intrinsic factors of the laser, GPS and Inertial Measurement Unit (IMU) three synchronization . With the development of commercial GPS and IMU, (such as on an airplane) available on mobile platforms through highly accurate LIDAR data it has become possible and is widely used.
LIDAR system comprises a single laser beam and a narrow band receiving system. Pulse laser beam of light generated and emitted, and reflected on the object to play back, eventually being received by the receiver. Receiver measures the light pulse is reflected back from the transmitter to the propagation time accurately. Since the speed of light in a light pulse, the receiver will always be issued before the next pulse is received before a pulse is reflected back. Given the speed of light is known, the propagation time can be converted into a measurement of distance. Binding height, laser scanning angle of the laser, the position obtained from the GPS and laser light emitted from the laser direction INS obtained, can accurately calculate the ground coordinates of each spot X, Y, Z. Frequency of the laser beam emitted from the pulse can be several tens of thousands of pulses per second per second. For example, a frequency of ten thousand pulses per second system, the receiver will record six hundred thousand points in a minute. Ground spot Generally, LIDAR system at intervals ranging from 2-4m.
Lidar principle is very similar to the radar, as a laser source, a laser pulse emitted by the laser, hit the ground trees, roads, bridges and buildings, cause scattering, part of the light waves will be reflected to the laser radar receiving after, laser ranging principle calculated, the distance is obtained from the laser radar to the target point, pulsed laser constantly scans the target, the target can be obtained data of all points on an object, an imaging processing with this data, to obtain an accurate three-dimensional image.
Laser radar works with the basic radio radar no difference, i.e., a signal transmitted by the radar transmitting system, receiving system after being collected by the object reflector, and the distance to the target is determined by measuring the running time of the reflected light. As the radial velocity of the target, the light may be reflected by the Doppler frequency shift is determined, may be measured two or more distances, and calculating the rate of change calculated speed, which is also substantially directly detect radar working principle.
Advantages and disadvantages
Advantage of laser radar
Compared with ordinary microwave radar, laser radar is due to the use of a laser beam, the operating frequency is much higher than the microwave, so bring a number of advantages, including:
(1) high resolution
Laser radar Keyihuode high angle, distance and speed resolution. Usually angular resolution that is not less than 0.1mard can identify two targets on 3km distance from 0.3m (which is in any case impossible microwave radar), and track multiple targets; distance resolution of 0.lm; velocity resolution can be achieved within 10m / s. Distance and speed with high resolution, which means you can take advantage of the distance - Doppler imaging techniques to obtain a clear picture of the target. High resolution, is the most significant advantage of laser radar, which most applications are based on this.
(2) good for hiding, active and strong anti-interference ability
Laser light travels in straight lines, good direction, the beam is very narrow, only received on its propagation path, and therefore very difficult to intercept the enemy, and the laser radar transmitter system (transmitter telescope) diameter is very small, narrow receivable area, intends to launch different Further, an electromagnetic wave is widespread in nature and prone to microwave radar, the signal source can be small interfering effect on the nature of the laser radar, the laser against active; the probability of the laser interference signal into the receiver a very low interference ability is very strong, suitable for work in an increasingly complex and intense information warfare environment.
(3) low-altitude detection performance is good
Because of the influence of various microwave radar ground clutter, and low-altitude areas have some blind spots (undetectable region). For laser radar, only the irradiated target will produce reflection, influence of the complete absence of ground clutter, so you can "zero height", and to detect low-altitude performance than the microwave Leida Jiang a lot.
(4) small size, light weight
Usually bulky ordinary microwave radar, the entire system with several tons of quality in mind, light antenna aperture even reached several meters to tens of meters. The lidar will light, much dexterity, launch telescope aperture generally only centimeters, the minimum quality of the entire system of only a few dozen kilograms, erection, demolition is very easy to close. And the structure of the laser radar is relatively simple, easy maintenance, easy to manipulate, lower prices.
Disadvantage of laser radar
First, work by weather and atmospheric effects large. Laser generally clear weather less attenuation, spread far away. In heavy rain, smoke, fog and other bad weather, a sharp increase attenuation, propagation distance greatly affected. The co2 laser operating at a wavelength of 10.6μm, preferably all laser atmospheric transmission performance, attenuation in bad weather is sunny 6 times. The role of the ground or use low-co2 laser radar distance, sunny day for the 10-20km, while bad weather dropped to less than 1 km. Further, the laser beam will circulation distortion, jitter, directly affecting the measurement accuracy of the laser radar.
Secondly, due to the extremely narrow beam of laser radar, space in the search target is very difficult to directly affect the probability of intercept and detection efficiency of non-cooperative targets can only search within a smaller range, target acquisition, and thus less direct laser radar alone applied to battlefield target detection and search.
use
Laser scanning method is not only the main way to get three-dimensional geographic information within the military, and the data obtained by this route outcome is also widely used in resource exploration, urban planning , agricultural development, water conservancy , land use, environmental monitoring , transportation and communication, shockproof mitigation and national key construction projects aspects, to provide for the national economy, social development and scientific research a very important raw materials , and achieved significant economic benefits, demonstrating a good prospect. Compared with the traditional method of measuring airborne LIDAR low-dimensional surface data acquisition method, an advantage to the production cost data and post-processing industry low cost. At present, the majority of users need low-cost, high density, fast, high-precision digital elevation data or digital data surface, airborne LIDAR technology just to meet this demand, so it became a high-tech variety of measurement applications popular.
Quick access to highly accurate digital elevation data or digital surface data is a prerequisite for widespread use onboard LIDAR technology in many fields, so research airborne LIDAR data accuracy has very important theoretical and practical significance. In this context, research scholars have done a lot to improve the accuracy of airborne LIDAR data.
Laser radar is a work from the infrared to the ultraviolet spectral range radar system, its principles, and configured with laser ranging instrument very similar. Scientists use a laser pulse of probes called lidar, the continuous-wave laser beam is referred to detect a continuous wave laser radar. Action of the laser radar is able to accurately measure a target position (distance and angle), motion (velocity, attitude and vibration) and the shape, detection, identification, tracking and resolution targets. Over the years, scientists have developed a laser fire control radar, laser radar detection, missile guidance laser radar, laser range instrumentation radar, laser radar and other navigation.
Since flight operations is a laser radar aerial mapping of a first procedure, which provides direct starting the data for subsequent data processing industry. According to the basic principle of measurement error and the principle of the development of "standard", are required before the results of the error contained in a step, a step after the impact should be minimized. Therefore, by studying the airborne laser radar processes, optimize the design work plan to improve data quality, it is very meaningful.
3. The key technical parameters and performance indicators
1) point cloud object detection rate
2) the point cloud object recognition rate
3) a three-dimensional image reconstruction point clouds
4) point cloud object distance measurement accuracy