CN111736162B - Laser illumination echo detection device and method for complex target - Google Patents
Laser illumination echo detection device and method for complex target Download PDFInfo
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- CN111736162B CN111736162B CN202010769560.9A CN202010769560A CN111736162B CN 111736162 B CN111736162 B CN 111736162B CN 202010769560 A CN202010769560 A CN 202010769560A CN 111736162 B CN111736162 B CN 111736162B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/4802—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
Abstract
The invention discloses a laser illumination echo detection device and method aiming at a complex target, wherein the device comprises an initial light source, a spatial light modulator, a semi-reflecting and semi-transmitting mirror, a beam expanding unit, a light field detection unit and a control unit; the method comprises incident beam modulation, adjustment of illumination spots, detection of echo signals, data processing and optimization of incident beam modulation. The device provided by the invention has a simple structure, can obtain an optimal laser illumination scheme according to the characteristics of different targets, has the capabilities of modulating and detecting the light field, and provides a flexible and effective research platform for the theoretical research of the laser illumination technology; the method provided by the invention can quickly obtain parameters such as target distance, echo radiation intensity, radiation direction distribution characteristics and the like which are extremely concerned by the illumination system, and provides test data support for researching the influence of various factors in the illumination system on the illumination effect.
Description
Technical Field
The invention relates to the technical field of laser illumination, in particular to a laser illumination echo detection device and method for a complex target.
Background
The laser illumination is one of the important components of high-energy laser weapon systems, large astronomical telescopes and the like, and under the condition of low visibility or complex illumination, the laser illumination system can illuminate a target, improve the detected echo intensity and signal-to-noise ratio of the target, and provide more accurate target position and morphology information for a high-energy laser main emission system. In addition, the target illuminated by the laser can be used as a beacon source of the atmospheric turbulence correction system, so that the imaging quality is obviously improved, and the tracking efficiency is improved.
In practical application, laser illumination is a very complicated system engineering, and the illumination effect is closely related to various factors. Wherein, the target is mostly the geometry of structure complicacy, and the material and the geometry of target specific position can directly influence intensity and the radiation direction of echo to influence the echo intensity that echo detector received, finally influence the detection probability of detecting tracker to the target, and the prior art has not yet realized the technical scheme of optimal lighting effect according to the characteristic of different targets.
In addition, subject to objective factors such as test conditions and test cost, the research on some specific scientific problems in the laser illumination technology is still insufficient in China at present, and a technology capable of quickly and conveniently obtaining key parameters such as target distance, echo radiation intensity and direction characteristics and the like closely related to the illumination effect does not exist. If the problems are researched through a real outfield test, not only the cost and the cost-effectiveness ratio are unacceptable, but also the subsequent key technology is difficult to attack.
Disclosure of Invention
The invention provides a laser illumination echo detection device and method for a complex target, which are used for overcoming the defects that the optimal illumination effect cannot be realized according to the characteristics of different targets, key parameters in the illumination technology cannot be quickly and conveniently obtained and the like in the prior art.
In order to achieve the purpose, the invention provides a laser illumination echo detection device for a complex target, which comprises an initial light source, a spatial light modulator, a semi-reflecting and semi-transmitting mirror, a beam expanding unit, a light field detection unit and a control unit, wherein the initial light source is connected with the spatial light modulator;
the initial light source is used for providing incident light beams;
the spatial light modulator receives the incident beam and performs intensity distribution modulation on the incident beam to obtain an emergent beam with a set local intensity distribution mode;
the beam expanding unit receives the emergent light beam transmitted by the semi-reflecting and semi-transmitting lens and expands the emergent light beam to obtain an illumination spot covering the whole target model;
the beam expanding unit receives an echo signal generated after the illumination light spot irradiates the target model and emits the echo signal;
the half-reflecting and half-transmitting mirror reflects the echo signal into the light field detection unit;
the light field detection unit detects the echo signal and transmits data obtained by detection to the control unit in real time;
the control unit decodes the data obtained by detection by using a light field decoding algorithm to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics; meanwhile, the control unit controls the spatial light modulator to modulate the intensity distribution of the incident beam in real time according to the intensity of the echo radiation and the radiation direction distribution characteristic.
In order to achieve the above object, the present invention further provides a laser illumination echo detection method for a complex target, where the laser illumination echo detection method includes:
receiving an incident beam provided by an initial light source by using a spatial light modulator, and carrying out intensity distribution modulation on the incident beam by using the spatial light modulator to obtain an emergent beam with a set local intensity distribution mode;
expanding the emergent light beam by using a beam expanding unit to obtain an illumination spot covering the whole target model;
receiving echo signals generated after the illumination light spots irradiate the target model by using a beam expanding unit, and emitting the echo signals;
reflecting the echo signal into a light field detection unit by using a semi-reflecting and semi-transmitting mirror;
detecting the echo signal by using the light field detection unit to obtain detection data;
decoding the detection data by using a control unit to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics;
judging whether the total echo radiation intensity of the target model reaches the maximum or not according to the echo radiation intensity and the radiation direction distribution characteristic, and if so, outputting a target distance, the modulation phase distribution of the spatial light modulator, the light intensity distribution of an emergent light beam, the posture of the target model, the echo radiation intensity and the radiation direction distribution characteristic; otherwise, the modulation phase of the spatial light modulator is adjusted through the control unit until the obtained total echo radiation intensity of the target model reaches the maximum.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides a laser illumination echo detection device for a complex target, which comprises the following steps of firstly, carrying out intensity distribution modulation on an incident beam by using a spatial light modulator to obtain an emergent beam with a set local intensity distribution mode; expanding the emergent light beam by using a beam expanding unit to obtain an illumination spot capable of covering the whole target model; then, detecting echo signals reflected and scattered by the target model by using a light field detection unit, and transmitting data obtained by detection to a control unit in real time; and finally, decoding the data obtained by detection through a control unit to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics, and simultaneously controlling the spatial light modulator to modulate the intensity distribution of the incident beam in real time according to the echo radiation intensity and the radiation direction distribution characteristics by the control unit so as to maximize the total echo radiation intensity of the target model. The device provided by the invention has a simple structure, can obtain an optimal laser illumination scheme according to the characteristics of different targets, has the capabilities of modulating and detecting the light field, and provides a flexible and effective research platform for the theoretical research of the laser illumination technology.
2. The invention provides a laser illumination echo detection method for a complex target, which comprises the steps of firstly utilizing a light field detection device to receive a reflected and scattered echo signal of a target model in real time and detecting the echo signal; then, a control unit is used for carrying out data processing on the detection data to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics, whether the total echo radiation intensity of the target model reaches the maximum value or not is judged according to the echo radiation intensity and the radiation direction distribution characteristics, and if the total echo radiation intensity of the target model reaches the maximum value, the target distance, the modulation phase distribution of the spatial light modulator, the light intensity distribution of an emergent light beam, the posture of the target model, the echo radiation intensity and the radiation direction distribution characteristics are output; otherwise, the modulation phase of the spatial light modulator is adjusted by the control unit until the obtained total echo radiation intensity of the target model reaches the maximum. The detection method provided by the invention can quickly obtain parameters such as target distance, echo radiation intensity, radiation direction distribution characteristics and the like which are extremely concerned by the illumination system, and provides test data support for researching the influence of various factors in the illumination system on the illumination effect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a block diagram of a laser illumination echo detection device for a complex target according to the present invention;
FIG. 2 is a block diagram of a focusing light field camera in an embodiment of the present invention;
fig. 3 is a flowchart of a laser illumination echo detection method for a complex target according to the present invention.
The reference numbers illustrate: 1: an initial light source; 2: a polarizer; 3: a spatial light modulator; 4: a half-reflecting and half-transmitting mirror; 5: a beam expanding unit; 51: a secondary mirror; 52: a primary mirror; 6: a target model; 7: a light field detection unit; 71: a main lens; 72: a microlens array; 73: a window; 74: imaging the target surface; 8: a control unit.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.
The invention provides a laser illumination echo detection device for a complex target, which comprises an initial light source 1, a spatial light modulator 3, a semi-reflecting and semi-transmitting mirror 4, a beam expanding unit 5, a light field detection unit 7 and a control unit 8, wherein the initial light source is connected with the spatial light modulator 3 through the semi-reflecting and semi-transmitting mirror;
the primary light source 1 is used for providing an incident light beam;
the spatial light modulator 3 receives the incident light beam and modulates the intensity distribution of the incident light beam to obtain an emergent light beam with a set local intensity distribution mode (after the spatial light modulator is modulated, the illumination intensity is changed from uniform distribution to set specific intensity distribution); the spatial light modulator 3 can control the intensity distribution of the illumination light spots;
the beam expanding unit 5 receives the emergent light beam transmitted by the half-reflecting and half-transmitting mirror 4, expands the emergent light beam and obtains an illumination spot covering the whole target model 6;
the beam expanding unit 5 receives echo signals generated after the illumination light spots irradiate the target model 6, and emits the echo signals (the echo signals are incident to the half-reflecting and half-transmitting mirror 4 after passing through the beam expanding unit 5);
the half-reflecting and half-transmitting mirror 4 reflects the echo signal into the light field detection unit 7;
the light field detection unit 7 detects the echo signals, and transmits data obtained by detection (the data obtained by detection is each pixel value obtained after the echo signals pass through the light field detection unit 7) to the control unit 8 in real time;
the control unit 8 decodes the data obtained by detection by using a light field decoding algorithm to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics; meanwhile, the control unit 8 controls the spatial light modulator 3 to modulate the intensity distribution of the incident beam in real time according to the intensity of the echo radiation and the radiation direction distribution characteristic.
The target distance refers to the distance between the target model 6 and the light field detection unit 7.
The echo radiation intensity refers to the total echo radiation intensity of the target model
。
The radiation direction distribution characteristic refers to the number of rays of the echo signal reflected and scattered by the target model 6 in each direction.
The spatial light modulator 3 modulates the intensity distribution of the incident beam according to the modulation phase input in advance, and outputs an emergent beam with uneven intensity distribution, wherein the light intensity distribution of the emergent beam follows a preset light intensity distribution rule. Therefore, the spatial light modulator 3 can control the intensity distribution of the emergent light beam, so that the irradiation intensity of the illumination light spot at different parts of the target model 6 can be adjusted, and the spatial light modulator can be used for researching the relation between the illumination echo and illumination light with different intensity distributions.
The invention provides a laser illumination echo detection device for a complex target, which comprises the following steps of firstly, carrying out intensity distribution modulation on an incident beam by using a spatial light modulator to obtain an emergent beam with a set local intensity distribution mode; expanding the emergent light beam by using a beam expanding unit to obtain an illumination spot capable of covering the whole target model; then, detecting echo signals reflected and scattered by the target model by using a light field detection unit, and transmitting data obtained by detection to a control unit in real time; and finally, decoding the data obtained by detection through a control unit to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics, and simultaneously controlling the spatial light modulator to modulate the intensity distribution of the incident beam in real time according to the echo radiation intensity and the radiation direction distribution characteristics by the control unit so as to maximize the total echo radiation intensity of the target model. The device provided by the invention has a simple structure, can obtain an optimal laser illumination scheme according to the characteristics of different targets, has the capabilities of modulating and detecting the light field, and provides a flexible and effective research platform for the theoretical research of the laser illumination technology.
In one embodiment, the laser illumination echo detection device further comprises a polarizer 2, wherein the polarizer 2 is arranged between the initial light source 1 and the spatial light modulator 3, and is used for obtaining polarized light from an incident light beam emitted by the initial light source 1 and inputting the polarized light into the spatial light modulator 3.
The polarizer 2 is used to obtain polarized light from natural laser light.
In another embodiment, the beam expanding unit 5 comprises a secondary mirror 51 and a primary mirror 52 which are coaxial, the radius of the secondary mirror 51 is smaller than that of the primary mirror 52, and the distance between the secondary mirror 51 and the primary mirror 52 is adjustable;
the emergent beam is collected by the secondary mirror 51, enters the beam expanding unit 5, is emitted by the primary mirror 51, and irradiates the target model 6.
The initial light source 1, the spatial light modulator 3, the half-reflecting and half-transmitting mirror 4 and the beam expanding unit 5 form an illuminating system of the laser illumination echo detection device, and the beam expanding unit 5 is used as an emitting terminal of the illuminating system, so that the emitting aperture of the illuminating system can be improved, and the focusing state and the spot size of an illuminating beam at the target model 6 can be controlled. The beam expanding unit 5 of the present invention employs a two-stage lens system including a secondary mirror 51 and a primary mirror 52. The size of the illumination light spot is determined by the focal length of the secondary mirror, the focal length of the primary mirror, the distance between the primary mirror and the secondary mirror and the distance between the target model and the primary mirror; further, the distance between the primary mirror 52 and the secondary mirror 51 is adjustable to meet the experimental requirements under different illumination light conditions.
In the next embodiment, the light field detection unit 7 is a focusing light field camera;
the focusing light field camera is shown in fig. 2 and comprises a main lens 71 and a micro lens array 72, wherein a primary imaging point P 'is formed by the target model P under the main lens 71 through a window 73 (substantially, an echo signal generated by the target model is in the target model through the window 73), the primary imaging point P' passes through the micro lens array 72 and is imaged again on an imaging target surface 74 under different micro lenses of the micro lens array 72 to form a plurality of secondary imaging points P "; and the pixels of the secondary imaging points are data obtained by detection.
The focusing light field camera is equivalent to a secondary imaging system, primary imaging of a target model is secondarily imaged on an infrared sensor (namely an imaging target surface 74) through a micro lens array 72, and a group of compound eyes are generated to image the same target model so as to detect light field information of echo signals. In the context of figure 2, it is shown,
、
the aperture and the focal length of the main lens 71;
、
the aperture and the focal length of the micro lens in the micro lens array 72 are respectively;
、
respectively the object distance and the image distance in the imaging space of the main lens;
、
the object distance and the image distance of the micro lens array are respectively;
the distance from the main lens to the imaging target surface.
In a certain embodiment, the target model 6 is mounted on an electric pan-tilt head, and the electric pan-tilt head drives the target model 6 to rotate and move under the control of the control unit 8.
The electric cradle head can adjust the posture of the target model 6 and the distance between the target model 6 and the beam expanding unit 5. The motion control parameters of the electric pan-tilt are given by the control unit 8 according to program presetting or manual intervention. Furthermore, according to different research backgrounds, several common typical target models, such as airplanes, unmanned planes, satellites and the like, can be adopted for researching the influence of the geometric structure, the material and the pose of the target on the lighting effect.
In another embodiment, the distance between the spatial light modulator 3 and the beam expanding unit 5 is larger than
Wherein
Being the radius of the incident light beam,
the wavelength of the incident beam.
The distance between the spatial light modulator 3 and the beam expanding unit 5 refers to the distance between the spatial light modulator 3 and the secondary mirror 51 in the beam expanding unit 5, and is controlled to satisfy the far-field transmission condition of the illumination light, thereby obtaining the desired light intensity modulation.
In a certain embodiment, the primary light source 1 is a laser.
After the illumination light spot irradiates the target model 6, a backward reflection and scattering echo signal is generated, the echo signal is incident to the semi-reflecting and semi-transmitting mirror 4 through the beam expanding unit 5, and enters the light field detection unit 7 after being reflected by the semi-reflecting and semi-transmitting mirror 4. In practical applications, the target distance, the intensity of the echo radiation and the radiation direction distribution characteristics are three parameters of great interest for the illumination system. The invention adopts a focusing light field camera structure as a light field detection unit of an echo signal and obtains the three parameters through resolving by a control unit. Different from the traditional point target detection technology, the focusing light field camera has a larger view field, so that the distance values, the radiation intensity and the direction distribution of the radiation intensity of all target models in the view field can be obtained at one time, and the complexity of an echo detection device is greatly reduced.
The control unit 8 is not only used as an interface for man-machine interaction of the laser illumination echo detection device, but also responsible for controlling the operation of the spatial light modulator 3, the electric holder and other devices. In addition, because the decoding operation amount of the light field data is huge, the light field decoding is also completed by the control unit 8.
In the test process, illumination light (i.e. incident light beams) is modulated and then irradiates on the target model 6, illumination echoes (i.e. echo signals) are collected by the light field detection unit 7, the target distance, the echo radiation intensity and the radiation direction distribution characteristics are obtained through resolving by the control unit 8, and the illumination echo radiation intensity of the target model 6 in the specific target distance and the specific radiation direction is enabled to be strongest through continuously adjusting the light intensity distribution of the illumination light.
The invention also provides a laser illumination echo detection method for a complex target, as shown in fig. 3, including:
101: receiving an incident beam provided by an initial light source by using a spatial light modulator, and carrying out intensity distribution modulation on the incident beam by using the spatial light modulator to obtain an emergent beam with a set local intensity distribution mode;
102: expanding the emergent light beam by using a beam expanding unit to obtain an illumination spot covering the whole target model;
103: receiving echo signals generated after the illumination light spots irradiate the target model by using a beam expanding unit, and emitting the echo signals;
104: reflecting the echo signal into a light field detection unit by using a semi-reflecting and semi-transmitting mirror;
105: detecting the echo signal by using the light field detection unit to obtain detection data;
the light field detection unit detects the echo signals to obtain light intensity information, and the light field information can be decoded according to the light intensity information.
106: decoding the detection data by using a control unit to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics;
the target distance refers to the distance between the target model and the beam expanding unit.
107: according to the echo radiation intensity and the radiation direction distribution characteristic, whether the total echo radiation intensity of the target model reaches the maximum or not is judged (the total echo radiation intensity is continuously changed along with the change of the light intensity distribution of the emergent beam, the light intensity distribution of the emergent beam is changed for multiple times to obtain a plurality of total echo radiation intensities, the maximum value is selected from the total echo radiation intensities), if the total echo radiation intensity reaches the maximum, the target distance, the modulation phase distribution of the spatial light modulator, the light intensity distribution of the emergent beam (after the incident beam is subjected to phase modulation of the spatial light modulator, and the emergent beam is transmitted for a certain distance, the light intensity distribution is changed from uniform distribution to a set specific distribution shape), the posture of the target model, the echo radiation intensity and the radiation direction distribution characteristic; otherwise, the modulation phase of the spatial light modulator is adjusted through the control unit until the obtained total echo radiation intensity of the target model reaches the maximum.
The invention provides a laser illumination echo detection method for a complex target, which comprises the steps of firstly utilizing a light field detection device to receive a reflected and scattered echo signal of a target model in real time and detecting the echo signal; then, a control unit is used for carrying out data processing on the detection data to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics, whether the total echo radiation intensity of the target model reaches the maximum value or not is judged according to the echo radiation intensity and the radiation direction distribution characteristics, and if the total echo radiation intensity of the target model reaches the maximum value, the target distance, the modulation phase distribution of the spatial light modulator, the light intensity distribution of an emergent light beam, the posture of the target model, the echo radiation intensity and the radiation direction distribution characteristics are output; otherwise, the modulation phase of the spatial light modulator is adjusted by the control unit until the obtained total echo radiation intensity of the target model reaches the maximum. The detection method provided by the invention can quickly obtain parameters such as target distance, echo radiation intensity, radiation direction distribution characteristics and the like which are extremely concerned by the illumination system, and provides test data support for researching the influence of various factors in the illumination system on the illumination effect.
In one embodiment, for step 101, receiving an incident light beam provided by an initial light source by using a spatial light modulator, and performing intensity distribution modulation on the incident light beam by using the spatial light modulator to obtain an emergent light beam with a set local intensity distribution pattern, includes:
001: obtaining polarized light from an incident light beam provided by an initial light source by using a polarizer and inputting the polarized light into a spatial light modulator;
002: and carrying out intensity distribution modulation on the polarized light by using the spatial light modulator to obtain an emergent light beam with a set local intensity distribution mode.
In another embodiment, for step 102, expanding the outgoing light beam by using a beam expanding unit to obtain an illumination spot covering the entire target model, includes:
201: adjusting a beam expanding unit to enable an illumination light spot emitted from the beam expanding unit to cover the whole target model;
and the beam expanding unit is adjusted by adjusting parameters such as the focal length of a secondary mirror, the focal length of a primary mirror, the distance between the primary mirror and the secondary mirror, the distance between a target model and the primary mirror and the like in the beam expanding unit.
202: and expanding the beam of the emergent light beam by using the adjusted beam expanding unit to obtain an illumination spot covering the whole target model.
In a next embodiment, the light field detection unit is a focusing light field camera, the focusing light field camera includes a main lens and a micro lens array, the target model forms a primary imaging point under the main lens, the primary imaging point passes through the micro lens array and forms a plurality of secondary imaging points under different micro lenses of the micro lens array; and the pixels of the secondary imaging points are data obtained by detection.
For step 104, decoding the detection data by using a control unit to obtain a target distance, an echo radiation intensity and a radiation direction distribution characteristic, including:
processing the detection data by using a light field decoding algorithm in the control unit, wherein the light field decoding algorithm uses virtual depth
Describing the normalized distance between the primary imaging point P' and the microlens array:
in the formula (I), the compound is shown in the specification,
is a virtual depth;
is the object distance of the microlens array (i.e., the actual distance from the primary imaging point to the microlens array);
is the image distance of the microlens array;
the primary imaging point P' of the target model P is imaged again as an image point P under different microlenses through the microlens array i ". The projection area of the primary imaging point P 'on the micro lens array is a circle, the center of the circle is the projection point of the primary imaging point P' on the micro lens array surface, and the radius of the circle depends on the virtual depth of the primary imaging point P
And satisfies the relation:
in the formula (I), the compound is shown in the specification,
the radius of a projection circular domain of a primary imaging point on the micro lens array;
is a virtual depth;
is the aperture of the micro lens;
virtual depth is achieved when each microlens in the microlens array is an independent camera
Calculated by the binocular vision classical algorithm:
in the formula (I), the compound is shown in the specification,
is a virtual depth;
the number of microlenses included between two farthest microlenses in a projection circular field on the microlens array for a primary imaging point;
is the aperture of the micro lens;
the Euclidean distance between the registration secondary imaging points in the two farthest micro-lenses is taken as the reference point;
due to the aperture of the micro-lens
The radius of the projection circle of the primary imaging spot on the microlens array is known
Can be obtained by detection of a focusing light field camera, and then virtual depth can be calculated and obtained according to formula (2)
。
Due to the image distance of the microlens array
Is known, then according to the virtual depth
And the formula (1), the actual distance from the primary imaging point P' to the micro-lens array can be obtained
。
Let the microlens array be at a distance from the main surface of the main lens
And then the distance between the target model and the light field detection unit is as follows:
in the formula (I), the compound is shown in the specification,
the distance between the target model and the light field detection device is taken as the distance;
is the main lens focal length of the light field detection device;
the object distance of the micro lens array of the light field detection unit;
is the image distance of the microlens array;
the distance from the microlens array to the main surface of the main lens;
further analysis shows that the primary image point P' of the target model P and a microlens for observing the primary image point P
Determine a direction from P' to
Light of (2)
(one ray represents one direction), and
is a point P of secondary imaging in the sub-image i "intensity of the incident light ray (the incident light ray refers to the light ray incident into the focusing light field camera) is
The radiation intensity of the direction, in the structure of the focusing light field camera, the light emitted by the primary imaging point P 'can be recorded by a plurality of micro-lenses in the projection circle domain, and the secondary imaging point P of the primary imaging point P' under the micro-lenses is found out i "the distribution of the echo intensity in the direction is obtained. All secondary imaging points P of the target model P i And adding the pixel intensities to obtain the total echo radiation intensity of the target model in the field of view of the light field detection unit as follows:
in the formula (I), the compound is shown in the specification,
the total echo radiation intensity of the target model in the field of view of the light field detection unit;
pixel intensity of a secondary imaging point;
the direction of a connecting line between the primary imaging point and a certain micro lens in the micro lens array;
the number of microlenses.
In this embodiment, step 104 specifically includes:
401: initializing data of a focusing light field camera;
the purpose of data initialization is to compensate for the vignetting aberration of the micro lens, then feature point marking is carried out on initialized light field original data (the original data refers to an original image), the marked feature points are geometric structure feature points or texture feature points of a target model, and the feature points correspond to all target models capable of calculating echo information;
402: according to the marked feature points, feature point registration is carried out in the local domain of the feature points, and all secondary imaging points of the same target model and corresponding microlenses thereof are found out;
403: calculating the distance between the target model and the light field detection device by using a light field decoding algorithm;
calculating the distance between the target model and the light field detection device according to the formula (4)
；
404: recording the sub-image pixel intensities of the same target model under all the micro lenses, and adding the sub-image pixel intensities to obtain the total echo radiation intensity of the target model;
405: and obtaining a full-field depth map of the focusing light field camera and a global radiance distribution map of the target model by adopting a finite field interpolation method according to the total echo radiation intensity of the target model.
The global radiance distribution map refers to the intensity of the echo radiation and the radiation direction distribution characteristics of the target model.
Example 1
The embodiment provides a laser illumination echo detection device for a complex target, which comprises a laser, a polarizer 2, a spatial light modulator 3, a semi-reflecting and semi-transmitting mirror 4, a beam expanding unit 5, a target model 6, a focusing light field camera and a control unit 8;
the beam expanding unit 5 comprises a secondary mirror 51 and a primary mirror 52 which are coaxial, the radius of the secondary mirror 51 is smaller than that of the primary mirror 52, and the distance between the secondary mirror 51 and the primary mirror 52 is adjustable;
the focusing light field camera includes a main lens 71 and a microlens array 72.
Between the spatial light modulator 3 and the secondary mirror 51 in the beam expanding unit 5The distance is far greater than
Wherein
The radius of the incident beam provided for the laser,
is the incident beam wavelength.
The laser emits narrow-beam laser (i.e. incident beam) with the diameter of 2mm, the wavelength is 808nm, the incident beam is incident to the spatial light modulator 3 through the polarizer 2, the spatial light modulator 3 modulates the incident beam under the control of the control unit 8 to obtain an emergent beam with a specific local intensity distribution mode, the emergent beam passes through the half-reflecting and half-transmitting mirror 4 after being transmitted for 5m, the emergent beam is expanded by the beam expanding unit 5, the size of an illumination spot obtained after beam expansion is about 30cm, and the size of a target model 6 is 25cm, so that the illumination spot can cover the target model 6. The target model 6 can do displacement and rotation movement under the control of the electric pan-tilt. Reflected and scattered echo signals of the target model 6 are collected by a primary mirror 52 of the beam expanding unit 5, then are emitted by a secondary mirror 51, and then are reflected by the semi-reflecting and semi-transmitting mirror 4 to enter the focusing type light field camera, the focusing type light field camera detects the echo signals, and transmits data obtained by detection to the control unit 8 in real time;
the control unit 8 decodes the data obtained by detection by using a light field decoding algorithm to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics; meanwhile, the control unit 8 controls the spatial light modulator 3 to modulate the intensity distribution of the incident beam in real time according to the intensity of the echo radiation and the radiation direction distribution characteristic.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. The laser illumination echo detection device for the complex target is characterized by comprising an initial light source, a spatial light modulator, a semi-reflecting and semi-transmitting mirror, a beam expanding unit, a light field detection unit and a control unit;
the initial light source is used for providing incident light beams;
the spatial light modulator receives the incident beam and performs intensity distribution modulation on the incident beam to obtain an emergent beam with a set local intensity distribution mode;
the beam expanding unit receives the emergent light beam transmitted by the semi-reflecting and semi-transmitting lens and expands the emergent light beam to obtain an illumination spot covering the whole target model;
the beam expanding unit receives an echo signal generated after the illumination light spot irradiates the target model and emits the echo signal;
the half-reflecting and half-transmitting mirror reflects the echo signal into the light field detection unit;
the light field detection unit detects the echo signal and transmits data obtained by detection to the control unit in real time;
the control unit decodes the data obtained by detection by using a light field decoding algorithm to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics; meanwhile, the control unit controls the spatial light modulator to modulate the intensity distribution of the incident beam in real time according to the intensity of the echo radiation and the radiation direction distribution characteristic.
2. The apparatus of claim 1, further comprising a polarizer disposed between the initial light source and the spatial light modulator for obtaining polarized light from the incident beam of light emitted from the initial light source and inputting the polarized light into the spatial light modulator.
3. The laser illumination echo detection device for the complex target according to claim 1, wherein the beam expanding unit comprises a secondary mirror and a primary mirror which are coaxial, the radius of the secondary mirror is smaller than that of the primary mirror, and the distance between the secondary mirror and the primary mirror is adjustable;
and the emergent light beam enters the beam expanding unit after being collected by the secondary mirror, is emitted by the primary mirror and irradiates the target model.
4. The laser illumination echo detection device for complex targets of claim 1, wherein the light field detection unit is a focusing light field camera;
the focusing light field camera comprises a main lens and a micro lens array, a target model forms a primary imaging point under the main lens, and the primary imaging point passes through the micro lens array and forms a plurality of secondary imaging points under different micro lenses of the micro lens array through imaging again; and the pixels of the secondary imaging points are data obtained by detection.
5. The apparatus according to claim 1, wherein the target model is mounted on a motorized pan/tilt head, and the motorized pan/tilt head rotates and moves the target model under the control of the control unit.
6. The apparatus of claim 1, wherein a distance between the spatial light modulator and the beam expanding unit is greater than
Wherein
Is the radius of the incident light beam,
the wavelength of the incident beam.
7. A laser illumination echo detection method for a complex target, the laser illumination echo detection method comprising:
receiving an incident beam provided by an initial light source by using a spatial light modulator, and carrying out intensity distribution modulation on the incident beam by using the spatial light modulator to obtain an emergent beam with a set local intensity distribution mode;
expanding the emergent light beam by using a beam expanding unit to obtain an illumination spot covering the whole target model;
receiving echo signals generated after the illumination light spots irradiate the target model by using a beam expanding unit, and emitting the echo signals;
reflecting the echo signal into a light field detection unit by using a semi-reflecting and semi-transmitting mirror;
detecting the echo signal by using the light field detection unit to obtain detection data;
decoding the detection data by using a control unit to obtain a target distance, echo radiation intensity and radiation direction distribution characteristics;
judging whether the total echo radiation intensity of the target model reaches the maximum or not according to the echo radiation intensity and the radiation direction distribution characteristic, and if so, outputting a target distance, the modulation phase distribution of the spatial light modulator, the light intensity distribution of an emergent light beam, the posture of the target model, the echo radiation intensity and the radiation direction distribution characteristic; otherwise, the modulation phase of the spatial light modulator is adjusted through the control unit until the obtained total echo radiation intensity of the target model reaches the maximum.
8. The method of claim 7, wherein the receiving an incident beam from an initial light source by a spatial light modulator and performing intensity distribution modulation on the incident beam by the spatial light modulator to obtain an emergent beam with a set local intensity distribution pattern comprises:
obtaining polarized light from an incident light beam provided by an initial light source by using a polarizer and inputting the polarized light into a spatial light modulator;
and carrying out intensity distribution modulation on the polarized light by using the spatial light modulator to obtain an emergent light beam with a set local intensity distribution mode.
9. The method according to claim 7, wherein expanding the outgoing beam by a beam expanding unit to obtain an illumination spot covering the entire target model comprises:
adjusting a beam expanding unit to enable an illumination light spot emitted from the beam expanding unit to cover the whole target model;
and expanding the beam of the emergent light beam by using the adjusted beam expanding unit to obtain an illumination spot covering the whole target model.
10. The method of claim 7, wherein the light field detection unit is a focused light field camera; the focusing light field camera comprises a main lens and a micro lens array, a target model forms a primary imaging point under the main lens, and the primary imaging point passes through the micro lens array and forms a plurality of secondary imaging points under different micro lenses of the micro lens array through imaging again; the pixels of the secondary imaging points are data obtained by detection;
decoding the detection data by using a control unit to obtain a target distance, an echo radiation intensity and a radiation direction distribution characteristic, wherein the method comprises the following steps:
performing data processing on the detection data by using a light field decoding algorithm in the control unit, wherein the light field decoding algorithm describes a normalized distance between the primary imaging point and the microlens array by using a virtual depth:
in the formula (I), the compound is shown in the specification,
is a virtual depth;
is the object distance of the microlens array;
is the image distance of the microlens array;
the projection area of the primary imaging point on the micro lens array is a circular area, the center of the circular area is the projection point of the primary imaging point on the micro lens array surface, the radius of the circular area depends on the virtual depth of the primary imaging point, and the relationship is satisfied:
in the formula (I), the compound is shown in the specification,
the radius of a projection circular domain of a primary imaging point on the micro lens array;
is a virtual depth;
is the aperture of the micro lens;
each microlens in the microlens array is an independent camera, and the virtual depth is calculated by a binocular vision classical algorithm:
in the formula (I), the compound is shown in the specification,
is a virtual depth;
the number of microlenses included between two farthest microlenses in a projection circular field on the microlens array for a primary imaging point;
is the aperture of the micro lens;
the Euclidean distance between the registration secondary imaging points in the two farthest micro-lenses is taken as the reference point;
the distance from the target model to the light field detection unit is as follows:
in the formula (I), the compound is shown in the specification,
the distance between the target model and the light field detection device is taken as the distance;
is the main lens focal length of the light field detection device;
the object distance of the micro lens array of the light field detection unit;
is the image distance of the microlens array;
the distance from the microlens array to the main surface of the main lens;
the total echo radiation intensity of the target model in the field of view of the light field detection unit is as follows:
in the formula (I), the compound is shown in the specification,
the total echo radiation intensity of the target model in the field of view of the light field detection unit;
pixel intensity of a secondary imaging point;
the direction of a connecting line between the primary imaging point and a certain micro lens in the micro lens array;
the number of microlenses.
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