Source: https://patents.google.com/patent/KR102038533B1/en
Timestamp: 2020-04-02 10:23:07
Document Index: 294336000

Matched Legal Cases: ['art 1', 'art 2', 'art 1', 'art 1', 'art 1', 'art 1', 'art 2', 'art 2', 'art 2']

KR102038533B1 - Laser Radar System and Method for Acquiring Target Image - Google Patents
Laser Radar System and Method for Acquiring Target Image Download PDF
KR102038533B1
KR102038533B1 KR1020130052336A KR20130052336A KR102038533B1 KR 102038533 B1 KR102038533 B1 KR 102038533B1 KR 1020130052336 A KR1020130052336 A KR 1020130052336A KR 20130052336 A KR20130052336 A KR 20130052336A KR 102038533 B1 KR102038533 B1 KR 102038533B1
KR1020130052336A
KR20130140554A (en
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2012-06-14 Priority to KR1020120063801 priority Critical
2012-06-14 Priority to KR20120063801 priority
2013-05-09 Application filed by 한국전자통신연구원 filed Critical 한국전자통신연구원
2013-12-24 Publication of KR20130140554A publication Critical patent/KR20130140554A/en
2019-10-31 Application granted granted Critical
2019-10-31 Publication of KR102038533B1 publication Critical patent/KR102038533B1/en
The present invention relates to a laser radar system and a target image acquisition method, comprising: a light source for irradiating a laser beam; An optical deflector disposed between the light source and the target and configured to irradiate a laser beam irradiated from the light source to another position of the target over time; A photodetector for detecting a laser beam reflected from the target according to the irradiation of the optical deflector, wherein the photodetector includes: Sqrt (2) x P RBS + 2 x D RBS ≤ D DA ≤ 2 x D lens And a light receiving detection surface having a diameter D DA satisfying Equation (4 / [pi]) x wavelength x F_number < D RBS < D lens .
Where P RBS is the distance between the receiving laser beam spots, D RBS is the diameter of the receiving laser beam spot, D DA is the diameter of the light receiving detection surface, D lens is the pupil diameter of the receiving optical system, wavelength is the wavelength of the laser, and F_number is the receiving optical system. F number according to diameter and focusing.
Laser Radar System and Method for Acquiring Target Image
The present invention relates to a laser radar system and a target image acquisition method for obtaining three-dimensional images and images.
The three-dimensional imaging system is not only used for products such as three-dimensional display TVs, but also three-dimensional images of remote military targets, three-dimensional images for monitoring natural environments such as landslides, and three-dimensional images around various vehicles required for the operation of unmanned autonomous vehicles. Can be used to secure
Even poor quality 3D images could play a role in some areas, but as the application area expands in recent years, the demand for high quality 3D images is required in various environments, and the laser radar system for this has been spotlighted. I am getting it.
Prior art laser radar systems for obtaining three-dimensional images and images include a forward scan LADAR (PSL) and a forward looking LADAR (FLL). Omnidirectional scan lidar (PSL) is disclosed in US Patent Publication No. 2011-0216304 (name: HIGH DEFINITION LIDAR SYSTEM) (hereinafter referred to as 'prior art 1'), forward observation lidar (FLL) Is disclosed in US Patent No. 6414746 (Invention name: 3-D imaging multiple target laser radar) (hereinafter referred to as 'prior art 2').
The prior art 1 includes a plurality of laser generating modules and a plurality of photo detectors, for example four laser generating modules and a photo detector array of '4 × 1'. The driving of the prior art 1 may be configured such that the laser generation module and the photodetector array operate at different times or at the same time.
However, in the related art 1, it is difficult to align each laser generating module and each photo detector pair corresponding thereto so that a plurality of laser generating modules and a photo detector array can be scanned in a single line form or a predetermined form. In other words, it is necessary to examine what observation range the signals detected by each of the photodetectors have spatially, and to modify the arrangement of the plurality of laser generating modules and the photodetector array to meet the specifications. This process affects the cost of the module and can be detrimental to mass production.
In addition, the prior art 1 can obtain a two-dimensional image (usually distance information about the line in the vertical direction) without rotating the module, the whole including a plurality of laser generating module and the photo detector array in order to obtain a three-dimensional image The transmit / receive module should rotate.
The prior art 2 is composed of a plurality of photo detectors, 'M X N' photo detector array for detecting the light that is reflected back to the target after irradiating the optical signal generated in one laser generation module to a wide area. Specifically, the pulse laser generator for generating a short pulse evenly irradiates the laser on a wide surface at a constant divergence angle through a diffuser or the like. In this case, there is a characteristic in which the irradiation area is extended with distance, and a repeated light pulse irradiation surface is generated. The light pulse irradiation surface is reflected by being hit by a target, the reflected light signal is collected through the light receiving lens, and the collected light signal is detected by the light detector array. In this case, each detector of the photodetector array operates individually, measures the time difference and the magnitude of the reflected optical signal at each pixel position, and collects this information to form a three-dimensional image of an object reflecting the optical signal. .
However, since the related art 2 requires a relatively high laser pulse power, it is difficult to implement a pulse laser module having a high repetition rate, and thus it is difficult to secure a high frame rate.
In addition, in the prior art 2, in order to detect the signals of each photodetector without the influence of the peripheral detectors in implementing the photodetector array, an optical signal that is reflected and reflected on an object independently as a pixel-by-pixel signal is detected. A pixel-by-pixel readout circuit is required, and the pixel-by-pixel readout circuitry is arranged in a two-dimensional array, and a portion for transmitting and processing a signal generated inside the pixel to the outside Finally, there is a need for a readout IC (ROIC) that can be transferred externally through an interface pad located near the edge of the chip.
In this type of ROIC, digital and analog exist simultaneously. ROIC is difficult to implement because of sufficient signal-to-noise ratio even in a narrow pixel area, and features high cost. In addition, ROICs and photodetector arrays are typically implemented using different substrates, so they can't be made all at once, and are connected to each other in a relatively expensive flip chip method. As a result, this complex imaging system uses short laser pulses on a large surface, and thus has the feature of obtaining a still image for a fast moving object (e.g., a rotor blade of a helicopter) (Flash image). Although used for military purposes, it is generally difficult to popularize due to the high overall manufacturing cost of the system.
The present invention has been made to solve the above problems, to minimize the effort, such as optical path alignment required to obtain a three-dimensional image, to reduce the overall cost of implementation, to provide a laser radar system suitable for mass production Its purpose is to.
Another object of the present invention is to eliminate or greatly reduce the drive unit that requires the movement of the entire sensor module, such as high stability, high-speed operation, and at the same time expensive photo detector array, FPA without compromising the design of the applied product It provides a laser radar system that can be implemented in a simpler structure without requiring a focal plane array and a readout IC that requires complex pixel-by-pixel driving to drive it.
Another object of the present invention is to provide a laser radar system capable of relatively easily eliminating or reducing blind spots that are not detected when mounted on a vehicle or the like.
Another object of the present invention is to provide a laser radar system capable of driving over a large area with respect to a target.
Another object of the present invention is to provide a laser radar system that can set the resolution of three-dimensional image data differently for each region.
It is still another object of the present invention to simultaneously or in some cases conditionally drive a three-dimensional image comprising long range data providing a high SNR mode for a narrow angle and short range data providing a low SNR mode for a wide angle. Provided is a laser radar system capable of acquiring long-distance data for an area of interest and conditionally acquiring data of a wide area for other areas.
In order to achieve the above object, the system of the present invention comprises a laser radar system for obtaining an image of a target using a laser beam, a light source for irradiating the laser beam; An optical deflector disposed between the light source and the target and configured to irradiate a laser beam irradiated from the light source to another position of the target over time; A photodetector for detecting a laser beam reflected from the target according to the irradiation of the optical deflector, wherein the photodetector includes: a light receiver having a diameter D DA satisfying the following Equations 1 and 2; A detection surface is provided.
Sqrt (2) x P RBS + 2 x D RBS ≤ D DA ≤ 2 x D lens
Where P RBS is the distance between the receiving laser beam spots, D RBS is the diameter of the receiving laser beam spot, D DA is the diameter of the light receiving detection surface, and D lens is the pupil diameter of the receiving optical system.
(4 / π) x wavelength x F_number <D RBS <D lens
Where wavelength is the wavelength of the laser and F_number is the F number according to the diameter and focusing of the receiving optics.
On the other hand, the method of the present invention is a method of obtaining an image of a target using a laser beam in a laser radar system, comprising the steps of: generating a laser beam to irradiate the target; Irradiating the generated laser beam to another position of the target over time; Detecting a laser beam reflected from the target as a result of the irradiation with a photodetector; And reading the detected laser beam by using other position information of the target over time used in the irradiating step, wherein the photodetector is represented by the following [Equation 1] and [Equation 2]. It is characterized by including the light-receiving detection surface having a satisfied diameter D DA .
Where wavelength is the wavelength of the laser and F_number is the F number according to the diameter and focus of the receiving optics.
As described above, according to the present invention, a "large-area optical detector (aka: static integrated detector (STUD)) based on a light transmitting unit which detects different positions according to time with respect to a target and detects the fixed light receiving unit based on Laser radar " to obtain high-resolution three-dimensional images and images in real time.
In addition, the present invention provides a laser radar system that does not require rotation of a sensor head having a large volume and is implemented in a single detection method integrated into one instead of individual detection of a detector array, thereby obtaining optical path alignment and the like when obtaining a three-dimensional image. The same effort can be minimized, eliminating the need for expensive detector arrays or focal plane arrays (FPAs), and eliminating the need for expensive ROICs to drive these FPAs, resulting in lower implementation costs and lasers for mass production. Radar systems can be provided.
In addition, by providing a laser radar system including one light transmitting unit and at least one light transmitting unit, in the implementation of a vehicle or various application systems, an area that is not detected by being hidden by a hood or a part of the system of the vehicle, that is, an undetectable area Can be reduced or eliminated
In addition, by providing a laser radar system including at least one light receiving lens having a different wide-angle characteristics, it is possible to simultaneously obtain long-distance data in the high SNR mode and wide angle three-dimensional image in the low SNR mode.
In addition, by providing a laser radar system for processing a signal received through the at least one light receiving unit in one signal processing module, it is a very simple method compared to the conventional ROIC composition that must analyze the reflected signal for each pixel, so in terms of implementation cost It is advantageous.
In addition, by providing a laser radar system using at least one transmitting unit operating in different time zones, it is possible to implement a system that provides a scan of a larger area, effective blind spot resolution, different resolutions for each region as needed.
1 is a block diagram of a laser radar system according to the present invention.
2 is an explanatory diagram of a technique of detecting a fixed light receiving unit by irradiating different positions with respect to a target of a light transmitting unit according to the present invention with time;
3A and 3D are explanatory diagrams of various ways of investigating different locations over time for a target of the present invention.
4A and 4B are explanatory diagrams showing the concept of a large-area photodetector of the present invention and the diameter of the light receiving detection surface;
4C is an illustration of a large area photodetector of the present invention.
5 is a configuration diagram of a laser radar system according to a first embodiment of the present invention.
6 is a configuration diagram of a laser radar system according to a second embodiment of the present invention.
7 is a configuration diagram of a laser radar system according to a third embodiment of the present invention.
8 is a configuration diagram of a laser radar system according to a fourth embodiment of the present invention.
9 is a configuration diagram of a laser radar system according to a fifth embodiment of the present invention.
10A and 10B are explanatory diagrams of various applications to which the laser radar system of the present invention is applied.
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.
The present invention proposes a "large-area photodetector-based laser radar" in which the light-transmitting unit irradiates different positions with respect to a target over time and detects it with a fixed light-receiving unit, that is, a photodetector having a large-area light receiving detection surface. Such a laser radar of the present invention will also be referred to as a "static unified detector (STUD: based laser radar)".
In the laser radar system of the present invention, the light transmitting unit repeatedly generates a short laser pulse to irradiate different positions (in different directions) over time with respect to the target [scattered in space], and the fixed light receiving unit is targeted. Collect all or part of the laser beam that is reflected against the beam and detect the collected light through a single or divided large-area detector. And then analyze the incident laser light to calculate distance or / and reflected light intensity information. Three-dimensional images and images are obtained using the results of the distance or / and reflected light intensity information calculation.
1 is a block diagram of a laser radar system according to the present invention, Figure 2 is an explanatory diagram of a technique for detecting a fixed light receiving unit by irradiating the position of the light transmitting unit according to the present invention with respect to the target over time.
The laser emitted from the pulse laser 110 is output via the transmission optical system 120. The light emitted from the transmission optical system 120 is irradiated to the target 140 through the optical deflector 130 to a desired area, that is, different areas, over time. The light transmission optical system 120 may be omitted depending on the application, or may be configured to have a constant divergence angle using a diffuser. The transmission optical system 120 and the optical deflector 130 may be implemented in one form, or may be implemented in a different order. The laser light irradiated to the specific region is returned to fit the target 140.
The laser light reflected from the target 140 passes through the fixed light filter 150 to block other noise light, and then passes through the fixed light receiving lens 160 for focusing to the large-area photodetector 170. Will be reached. The order of the optical filter 150 and the light receiving lens 160 may be interchanged with each other, and the optical filter 150 is an optional component.
In the present invention, the fixed light receiving unit may be understood to include the fixed light receiving lens 160 and the photodetector 170. This fixed light receiver collects all or a portion of the laser beam reflected on the target and detects the collected light through a single or split or arrayed photodetector 170. In addition, the light receiving unit of the present invention may further include a module for controlling the temperature in order to maintain a constant performance of the photodetector 170 whose characteristics are sensitively changed according to the temperature.
The optical deflector 130 of the present invention is disposed between the light source 110 for irradiating the laser beam and the target 140, so that the laser beam irradiated from the light source 110 is positioned at another position of the target 140 over time. To be investigated.
In addition, the laser radar system of the present invention further includes a signal reading unit that reads the laser beam detected by the photodetector 170 by using other position information of the target over time used by the optical deflector 130.
In addition, the laser radar system of the present invention calculates the distance of each observation point or / and the reflected light intensity information to the target 140 using the laser beam information read by the signal reader, and calculates the distance to each point. Or / and an image processor configured to determine a 3D image of the target 140 using the reflected light intensity information. In the present invention, distance or / and reflected light intensity information is used for 3D image determination. In other words, when viewed from an aircraft, the distance of the asphalt pavement and the ground next to it is detected at the same height, so that the reflected light intensity information is used to classify the pavement and the soil into different reflectances for accurate 3D image determination. It is also preferable to use.
In addition, the laser radar system of the present invention may further include a camera for obtaining a 2D image of the target 140. In this case, the image processor also performs a function of correcting or synthesizing the 3D target image and the 2D target image acquired by the camera.
The receiver of the present invention may be implemented with a device (eg, TEC, temperature controller) for maintaining a temperature-sensitive photodetector at a constant temperature so as to have the same characteristics, the laser reflected from the analog signal generated at the receiver It may further include a signal processing module that can process the time difference, or the size of the reflected laser. Afterwards, a three-dimensional image may be finally obtained from an analysis device that transmits and displays data through a connection cable using various communication protocols such as USB and Gigabit Ethernet. That is, the controller calculates different positions according to time, and analyzes the incident laser light to calculate distance or / and reflected light intensity information. Three-dimensional images and images are obtained using the results of the distance or / and reflected light intensity information calculation. Here, although the analysis device to display is described, only the processing board is processed, and thereafter, it is also possible to directly receive and process the real application (when a 3D image such as a vehicle and a robot can be directly recognized and processed).
In FIG. 1, the light path of the transmitter and the light path of the light receiver are differently represented, which is referred to as a dual axis or bi-axial structure. As another example, the present invention may be implemented in the case where the light path of the transmitter and the light path of the light receiver are the same (single-axis or uni-axial structure).
Figure 2 shows the operation of the present invention to detect the fixed light-receiving unit by irradiating the position of the transmission unit proposed in the present invention with respect to the target over time. In order to show the form of optical scanning in the present invention, the laser radar system scans in one plane (in the form of a line) on the plane, but in fact it is natural to scan the front in a two-dimensional plane. In this case, the pattern to be optically scanned may be variously applied to circular coordinates or other coordinates of different intervals as well as two-dimensional planar coordinates having the same interval. Such a pattern may be implemented by applying an appropriate driving signal to the optical scanner, and may determine the quality of the 3D image. That is, the scanning operation of the present invention is not a method of spreading a surface by spreading a laser beam, but irradiating each observation point with respect to a target with each laser beam pulse, and irradiating all observation points over time. Is cumulative, it scans random area regularly.
In addition, FIG. 2 shows a light transmission optical system 120 (eg, between the pulse laser 110 and the optical deflector 130). Collimators, etc.] may be further included, and the optical filter 150 may be further included between the target 140 and the light receiving lens 160.
In addition, the method of investigating different positions with respect to the target of the present invention may vary. 3A-3D are explanatory diagrams of various ways of investigating different locations over time for a target of the present invention.
3A shows a galvano mirror of a motor driven method. Figure 3b shows a rotating face mirror. 3c shows an EO scanner (Electro-Optic Scanner). 3d shows a fiber array laser.
The EO scanner shown in FIG. 3C is an optical waveguide that changes the direction of light with an electrical signal and is implemented in the form of a deflector. The fiber array laser shown in FIG. 3D may be implemented with an arrayed waveguide grating (AWG). The fiber array laser outputs the incoming laser beam to the target through multiple fiber tips looking at different directions by optically delaying or having different wavelengths in the AWG. You can scan with time differences. 3c and 3d have the advantage that there is no physical drive, there is a strong impact, there is no vibration and noise has the advantage.
In another example, the optical deflector of the present invention is a stepping motor or a brushless DC motor or a rotating mirror or an electromagnet galvano mirror or an acoustic optical deflector or a two-axis drive scan mirror or For 2D scanning, such as a MEMS scanner or a MEMS reflector, a homogeneous or heterogeneous scanner combination structure may be implemented.
In addition, the transmitting part of the present invention may further include a component for controlling the beam width of the optical pulse (hereinafter, referred to as an 'optical pulse beam width controller'). The optical pulse beam width controller may be composed of a collimator, a beam expander, a lens, or the like, or may be composed of one or two or more thereof.
Next, the large-area photodetector of the present invention will be described with reference to FIGS. 4A to 4C. 4A and 4B are explanatory diagrams showing the concept of the large-area photodetector of the present invention and the diameter of the light-receiving detection surface, and FIG. 4C is an exemplary diagram of the large-area photodetector of the present invention.
In FIG. 4A, the transmitter (pulse laser 110, optical deflector 130) emits a laser beam to the target 140. At this time, when viewed from the front direction to obtain 3D (3D) resolution, the minimum resolution is a condition that scans the coordinates of two horizontal and two vertically with time, the reflection generated by examining four different points for explanation The points are displayed in a cumulative form over time. In practice, each point must be scanned in turn. In FIG. 4A, the diagonally-transmitted light reflection surface laser beam spot 143 among the light transmission reflection laser beam spots 141, 142, 143, and 144 represents an area that is being irradiated at the present time. Here, P TBS means a pitch of target beam spot between adjacent light reflecting surface laser beam spots, and D TBS means a diameter of a light beam reflecting surface laser beam spot.
When the laser beam is irradiated to the distant target, the diameter D TBS of the light reflection surface laser beam spot generated when the target is hit is generally varied with distance. By transmitting collimated beams or transmitting them by increasing the initial size of the beams, it is also possible to somehow suppress this variation or increase with distance. In addition, when irradiating laser pulses to remote targets at different positions at different times, the distance P TBS between each transmitting reflection laser beam spot depends on the driving conditions of the optical deflector, If the distance is far, the distance P TBS between the transmission reflection surface laser beam spots increases linearly. The laser signal reflected from the target under the conditions of the P TBS and the D TBS is a distance between the received laser beam spots (P RBS : P RBS ) and the light receiving detection surface 170 of the photodetector through the light receiving lens 160. The diameter D RBS of the receiving laser beam spot may be converted and displayed under the condition of a diameter of received beam spot ( RBS ).
4A illustrates that the laser signal reflected from the target is incident on the light receiving detection surfaces at four different positions symmetrically about the light receiving lens 160 at different times according to time. In other words, when the scan is performed with a minimum resolution of 2x2 in total, the portion where the reflected laser beam is focused is displayed. Among the reception laser beam spots 171, 172, 173, and 174, the diagonally hatched reception laser beam spot 173 represents a position at which the current laser reflection signal is received.
Accordingly, the present invention proposes a light-receiving detection surface of a large area photodetector having a minimum area and a maximum area capable of receiving most beams so as to ensure maximum SNR for the reflection signals from all reflection points. .
When calculating the conditions for receiving all the reflected laser signals incident on the 2x2 image, which is the minimum resolution for acquiring the 3D image, the minimum size of the light-receiving detection surface required by the photodetector is determined by all It must be an area that contains. That is, the minimum diameter (D DA _ min : diameter of detecting area) of the light receiving detection surface was derived as "Sqrt (2) x P RBS + 2 x D RBS " . Here, the interval P RBS between the receiving laser beam spots means an interval of optical signals incident to the photodetectors at different times, and the diameter D RBS of the receiving laser beam spots indicates that one reflective laser signal is transferred to the photodetectors. It means the size of the beam is irradiated when incident. Of course, the diameter D RBS of the receiving laser beam spot may be different from each other in the vertical and horizontal intervals, and may vary for each of the reflected laser signals.
The maximum size of the light receiving detection surface required by the photodetector is derived as follows. It can be seen that it matches the size of the maximum beam incident through the light receiving lens 160, and even if the scan is assumed, it is difficult to more than double the size of the maximum beam, so the maximum diameter D DA_max of the light receiving detection surface is " 2 x D lens ". Here, the D lens is a pupil diameter of the receiving lens of the light receiving lens 160.
And, the minimum and maximum size of the laser beam for 3D image acquisition is the same as the single reflection laser beam coming through the light receiving lens. Therefore, the minimum beam size is the same as the focused spot size of the lens, and the formula is as follows. Therefore, the minimum diameter D RBS_min of the receiving laser beam spot may be defined as "(4 / π) x wavelength x F_number". Here, wavelength is the wavelength of the laser, F_number is the F number according to the diameter and focusing of the receiving lens. Since the maximum diameter D RBS _ max of the reception laser beam spot corresponds to the diameter of the light receiving lens, it may be defined as "D lens ".
The large-area photodetector of the present invention described above is summarized as follows. The photodetector of this invention is equipped with the light reception detection surface which has diameter DDA which satisfy | fills following [Equation 1] and [Equation 2].
On the other hand, as will be described later with reference to Figures 5 to 9, the laser radar system of the present invention may be composed of a plurality of transmitters and / and a plurality of receivers. That is, in the present invention, the receiver may be composed of two or more photodetectors to which different light receiving lens characteristics are applied, or two or more photodetectors facing different directions, and FIGS. 4A and 4B illustrate a single unit photodetector from the viewpoint of one unit. It is preferable to understand that it means the maximum size of the light-receiving detection surface.
As shown in Fig. 4C, the photodetector of the present invention has a single light receiving detection surface or a light receiving detection surface divided into at least two or more. In FIG. 4C, a rectangular photodetector is exemplified, but in the present invention, the photodetector may be implemented in various forms such as hexagon, circle, and ellipse.
The large-area photodetector of the present invention is not a single detector having a diameter of 20 to 50 μm, which is the diameter of a general optical communication detector, and is used to detect an optical signal region through a light receiving lens in which a laser pulse signal sent by a transmitter is reflected to an object and fixed. It is a detector having a light receiving area that may include. In the present invention, the large area means, for example, a size of 100 μm or more and less than 1 mm, and in some cases, may mean a size of 1 mm or more. In other words, it is to be understood that the large area of the present invention has an area capable of detecting almost all transmitted optical signals. This is because the position at which the reflection signal enters the light receiving portion is changed in response to different irradiation positions of the light transmitting portion with respect to the target.
In general, since the width of the laser pulse is several ns and several tens ns, the detection speed of the photodetector should be fast to detect it. When the light receiving area is increased, the output capacitance of the photodetector increases, resulting in a slow operation speed. As a result, a problem arises in that a short laser pulse cannot be detected. In order to solve this problem, the large-area photodetector may be configured as a photodetector designed not only in the form of a single photodetector but in various structures. For example, large area photodetectors may be comprised of multiple unit photodetectors to reduce parasitic capacitance. That is, the large-area photodetector according to the present invention may be composed of two or more divided photodetectors, and each unit pixel is assembled to form one large-area photodetector.
Since one light pulse can be reflected at more than one location, the large area photodetector can detect more than one light signal. This means that more than one three-dimensional point cloud may occur with one light pulse. Therefore, the large-area photodetector according to the present invention can operate in weather conditions such as dust, snow or rain in the air by using the multiple detection function. That is, since the ray point beam may be reflected from two or more positions in the target corresponding to one laser beam pulse irradiation according to the scan operation of the present invention, two or more coordinates of the laser beam are detected to generate two or more coordinate information. .
Large area photodetectors may be implemented in a variety of ways, including PN junction photodiodes, PIN photodiodes and APD photodiodes based on silicon or InP or semiconductor substrates.
As described above, in the present invention, a large-area photodetector is used, but the prior art uses a photodetector array, and this prior art uses the photodetector APD (avalanche photo-diode, avalan) as the incoming light is driven with different time information. Q photodiodes) have different time differences. That is, it is difficult to implement a ROIC in which each pixel has time information and interprets each pixel independently. On the contrary, the present invention has the advantage that the circuit configuration of the ROIC and the signal processing module does not have to be complicated in order to interpret the same because the TOF (Time of Flight, time information) for the light entering the two APDs is the same. .
That is, the circuit and the processing method of the signal processing module for processing the output of one (single) photodetector or the signal processing module for processing the output of two or more divided photodetectors by using the large-area photodetector of the present invention are the same. This is an advantage that it can be implemented. However, if it is found that the output of each photodetector has the same information in time, the process of adding each photodetector output to one output (for example, RF combiner or RF combiner) is further performed. Whether the signal comes from a single APD or from multiple unit APDs is important and can be integrated. Therefore, even if the present invention uses an array APD structure as in the prior art, the method of processing signals from a single APD by integrating all the electric signals from each pixel, All you need to do is implement a signal processing module that is easy to implement. In other words, it is desirable to understand that the split photodetector of the present invention includes both a unit APD, a plurality of unit photodetectors, and an array APD.
Then, various embodiments of the present invention will be described with reference to FIGS. 5 to 9, and the same technical configurations between the technical configurations and embodiments of the present invention described above with reference to FIGS. 1 to 4C will be described. Detailed description will be omitted and will be described based on the contrast.
FIG. 5 is a schematic diagram of a laser radar system according to a first embodiment of the present invention, and FIG. 5 is a large area single photodetector. Reference numeral 600 denotes a front view of the object.
The optical pulse generator 612 may be implemented as a master oscillator power amplifier (MOPA), a diode pumped solid state laser (DPSSL), an optical direct modulator, or the like. In addition, the optical pulse generator 612 according to the present invention may be configured to have a high pulse repetition frequency (PRF). The optical pulse generator 612 may maintain a high frame rate by scanning one surface using a high repetition rate. In general, to scan a QVGA (320x240) image at 30 frames per second (fps), a repetition rate of 230 KHz or more is required, which can be easily implemented in MOPA. While the prior art requires very high laser pulse power (several mJ / pulse), the repetition rate is about tens of fps, whereas the laser radar system according to the present invention is not a method of irradiating a large area with a laser pulse, and thus much more. It requires less laser power and can therefore produce high speed laser pulses with high repetition rates.
The light transmission module 614 includes the optical deflector described above, and may further include an optical pulse beam width controller for controlling the beam width of the optical pulse.
The light receiving lens 622 is fixed to collect the reflected signal of the beam transmitted from the light transmitting module 614, and collects the reflected signal coming in at a wide angle to the large-area photodetector 624 for detecting the actual signal. The light receiving lens 622 may be a fisheye lens, a user designed lens, or the like. In addition, the laser radar system according to the present invention includes an additional optical system such as a ball lens and a micro lens in the vicinity of the large-area photodetector 624 together with the light receiving lens 622, so that light of a wider angle is detected by the photodetector 624. It is possible to improve the signal-to-noise ratio depending on the implementation.
The laser radar system according to the second embodiment of the present invention includes one light transmitter 710 and two light receivers 720 and 730. In realizing a vehicle or various application systems, there may be an area that is not detected by the hood of the vehicle or a part of the system (hereinafter referred to as an “undetectable area”). Thus, the laser radar system includes two light receivers 720 and 730. ), The non-detectable area can be reduced or eliminated.
7 is a configuration diagram of a laser radar system according to a third embodiment of the present invention. 7 illustrates two light receiving lenses having different wide-angle characteristics, in which case two or more different photodetectors receive light through lenses having different characteristics. As another example, one common lens having different wide-angle characteristics may be used in an inner region, in which case, two or more different photodetectors receive light coming from light receiving lenses having different optical characteristics. .
In the laser radar system of FIG. 7, two light receiving lenses 722 and 732 having different wide-angle characteristics are disposed. That is, one light receiving lens 722 is used for viewing a wide angle, and another light receiving lens 732 is used for viewing a narrow angle to detect a relatively long distance reflected signal that is not measured at the wide angle. . In other words, when two light receiving lenses having different wide-angle characteristics are used, remote data of a high SNR mode and a wide angle three-dimensional image of a low SNR mode may be simultaneously acquired. In general, in the case of a vehicle application, it is necessary to detect a long distance from a central portion corresponding to a driving lane, and a wider angle of view may be required even if a short distance is detected from a surrounding environment such as a road. The laser radar system according to the present invention can satisfy this requirement because it operates by mixing a high angle SNR mode of a narrow angle and a low SNR mode of a wide angle.
6 and 7, signals received through the two light receivers 720 and 730 may be added to each other and processed in one signal processing module. Because the signals from the two light receivers 720 and 730 are similar signals with little time difference between the reflected pulses, a signal output can be configured after adding signals using a simple RF combiner or the like. This is because a single signal output can be analyzed by using a single signal processing module to analyze reflected signals at once. However, according to the requirements of the system, each signal may be processed by two signal processing modules, which may be determined according to the position or system requirements of the two light receivers 720 and 730. However, this case is also very simple compared to the conventional array-type ROIC structure in which the reflected signal must be analyzed pixel by pixel, which is very advantageous in terms of implementation cost.
6 and 7, one transmitter 710 is disposed in front of the two receivers 720 and 730, but is not limited thereto. One transmitter 710 may be disposed at an arbitrary position. have. However, in order to reduce the direct reflection noise from which the optical signal directly enters the light receivers 720 and 730 from the light receiver 710, the light transmitting surface of the light receiver 710 is formed by the light receiving lenses 722 and 732 of the light receivers 720 and 730. It is preferably arranged in front of the incident surface.
The laser radar system according to the fourth embodiment of the present invention includes two transmitters 910 and 920 and one receiver 930. With such a configuration, the laser radar system can detect the reflected signal of the optical signal transmitted from the light transmitting units 910 and 920 irradiating different areas using one light receiving unit 930.
In addition, the light pulse generated in one transmitter 910 does not mix with the light pulse generated in the other transmitter 920. To this end, the two transmitters 910 and 920 may use a time division method of alternately generating lasers. This is because when the light receiving unit 910 detects the incidence of light pulses, it should be known which light pulses are emitted from the light transmitting units 910 and 920.
In the laser radar system of FIG. 8, two transmitters 910 and 920 are arranged side by side. In the laser radar system according to the fifth embodiment of the present invention illustrated in FIG. 9, two transmitters 910 and 920 are arranged. It is arranged to scan different angles. For example, one transmitter 910 scans a narrow area of the central portion of the receiver 930 in detail, and the other transmitter 920 scans a relatively large area. By configuring the laser radar system as described above, the resolution can be easily changed for each region of the three-dimensional image to be observed. In addition, although the centers of the two transmitters 910 and 920 are different from each other in FIG. 9, the centers of the two transmitters 910 and 920 are not limited thereto. In addition, although the narrow angle of the optical signal is displayed in FIG. 9, the size of the optical signal may vary depending on the configuration of the transmitter.
In addition, although two transmitters 910 and 920 are disposed in front of one receiver 930 in FIGS. 8 and 9, the present invention is not limited thereto, and two transmitters 910 and 920 may be disposed at arbitrary positions. Can be. However, in order to reduce the direct reflection noise from which the optical signal directly enters the light receiving unit 930 from the light transmitting units 910 and 920, the light transmitting surface of the light receiving units 910 and 920 is an incident surface of the light receiving lens 932 of the light receiving unit 930. It is preferably arranged in the front.
Accordingly, the laser radar system according to the fourth and fifth exemplary embodiments of the present invention uses two light transmitting units 910 and 920 operating at different time periods to scan a larger area, solve an effective blind spot, and as needed. A system that provides different resolutions for each region can be implemented.
The laser radar system of FIGS. 6 and 7 includes one transmitter 710 and two receivers 720 and 730, and the laser radar system of FIGS. 8 and 9 includes two transmitters 910 and 920 and The laser radar system may include two or more light receivers and two or more light receivers, including, but not limited to, one light receiver 930.
In addition, although the laser radar system according to the present invention described with reference to the drawings are all configured in a dual axis structure, the laser radar system may be configured in a single axis structure. In addition, the light receiving unit and the light transmitting unit may be variously arranged, and the positions of the light receiving unit and the light transmitting unit may be variously set.
For example, when the laser radar system of the present invention is applied to an automobile, the light transmitting unit may be disposed at the hood edge portion of the vehicle, and the light receiving unit may be disposed at the windshield portion of the vehicle. As described above, the laser radar system according to the present invention has no limitation in optical alignment, and thus can greatly increase the degree of freedom in designing a vehicle, and can be mounted on the vehicle as a three-dimensional imaging system or a sensor without spoiling the design of the vehicle. Can be.
In addition, the prior art has a limit in reducing the size of the module in which a pair of the transmitter and the receiver is present together, which is also constrained in the rotational speed, the present invention uses a slip ring for the rotating body You do not have to do. Such slip ring has a liquid contact type that uses a material such as mechanical contact and mercury, and mechanical contact is a very unfavorable composition in durability, and in the case of a liquid connection type, mercury is reluctant to use due to environmental pollution. to be. When applied to applications such as vehicles, the present invention does not seriously compromise the inherent design of the vehicle due to the large volume of rotors.
In addition, the laser radar system according to the present invention can be easily aligned. This is because the laser radar system according to the present invention only needs to be able to irradiate a beam generated at the transmitting unit with a predetermined size over a desired distance range and to detect only the reflected optical signal using the receiving unit. In particular, in the present invention, the transmitter and receiver are present in pairs as in the prior art, and there is no need for separate correction for separation between different channels or alignment of the same channel. In addition, there is an advantage that it is not necessary to go through the candidate correction process to correct the characteristics between channels that are not corrected in advance in the subsequent process.
Laser radar system 1000 of the present invention is a vehicle, such as automobiles and ships (unmanned driving system, safe driving system (lane detection, human body / leading vehicle collision avoidance), etc.), aerospace / defense (helicopter, tank, etc.), It can be installed in various applications such as product inspection (product surface inspection, etc.) and unmanned security systems.
FIG. 10A shows that the laser radar system 1000 of the present invention is mounted in an automobile. 10B shows that the laser radar system 1000 of the present invention is mounted on a helicopter. The laser radar system can detect a wire to prevent a helicopter crash and can be used for landing guidance, docking guidance, air refueling, and the like.
The embodiments disclosed in the specification of the present invention are not intended to limit the present invention. The scope of the present invention should be construed by the claims below, and all techniques within the scope equivalent thereto will be construed as being included in the scope of the present invention.
110 pulse laser 130 optical deflector
140: target 160: light receiving lens
170: photodetector
In the laser radar system for obtaining an image of a target using a laser beam,
An optical deflector disposed between the light source and the target and configured to irradiate a laser beam irradiated from the light source to another position of the target over time;
A photodetector for detecting a laser beam reflected from the target according to the irradiation of the optical deflector,
The photodetector,
A laser radar system comprising a light receiving detection surface having a diameter D DA that satisfies the following [Equation 1] and [Equation 2].
And a signal reader which reads the laser beam detected by the photodetector by using other positional information of the target over time used by the optical deflector.
The apparatus further includes an image processor configured to calculate distance or reflected light intensity information of the target by using the laser beam information read by the signal reader, and determine a 3D image of the target by using the calculated distance or reflected light intensity information. Laser radar system, characterized in that.
Further comprising a camera for obtaining a 2D image of the target,
And the image processor corrects or synthesizes the determined 3D target image and the 2D target image acquired by the camera.
And the photodetector has a single light receiving detection surface or a light receiving detection surface divided into at least two or more.
And a photodetector having a light receiving detection surface divided into at least two or more, wherein a plurality of signals output from different divided light receiving detection surfaces are combined and processed into a single output signal.
And the optical deflector irradiates each laser beam pulse to each observation point with respect to a target, and scans a predetermined area at a predetermined period when all observation point irradiations are accumulated over time.
And generating at least one coordinate information by detecting the at least one reflected laser beam when the ray point beam is reflected from at least one position in the target corresponding to each laser beam pulse irradiation.
The optical deflector includes a plurality of optical scanning unit,
Wherein each of the optical scanning units is arranged to irradiate a laser beam at different angles or some overlapping areas or at different angles with respect to the target.
Each of the optical scanning unit is irradiated with a laser beam in a time division manner laser radar system.
The photodetector is a plurality of,
Wherein some of the photodetectors are arranged parallel or oblique to detect a reflected laser beam not detected by the other photodetectors.
And the photodetectors comprise at least one condenser having different wide-angle characteristics.
The optical deflector
A laser radar system comprising at least one of a galvano mirror or a rotating polyscopy or an acousto-optical deflector or a biaxial drive scan mirror or a MEMS scanner or a MEMS reflector.
A laser radar system comprising an EO scanner (Electro-Optic Scanner) or a fiber array laser.
In the method for obtaining an image of a target using a laser beam in a laser radar system,
Generating a laser beam to irradiate the target;
Irradiating the generated laser beam to another position of the target over time;
Detecting a laser beam reflected from the target as a result of the irradiation with a photodetector;
Reading the detected laser beam by using other position information of the target over time used in the irradiating step,
A light receiving detection surface having a diameter D DA satisfying the following Equations 1 and 2 is provided.
Calculating distance or reflected light intensity information of the target by using the read laser beam information;
And determining an image of the target by using the calculated distance or reflected light intensity information.
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