LiDAR system and operating method thereof

A Light Detection And Ranging (LiDAR) system may include: a transmitter configured to output pulse laser; a reflecting mirror comprising two or more reflecting surfaces to reflect the pulse laser; a driver configured to rotate the reflecting mirror; a path control mirror configured to reflect the pulse laser to the reflecting surfaces of the reflecting mirror to form an optical path of the pulse laser; and a receiver configured to receive the light reflected through the reflecting mirror, and convert the received light into an electrical signal, wherein the reflecting mirror comprises: a first reflecting surface; and a second reflecting surface, wherein the first and second reflecting surfaces are connected to each other at one point, the first reflecting surface and the second reflecting surface have different tilt angles from each other, and the first reflecting surface is tilted in the opposite direction of the second reflecting surface.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority from and the benefit of Korean Patent Application No. 10-2018-0084568, filed on Jul. 20, 2018, which is hereby incorporated by reference for all purposes as if set forth herein.

BACKGROUND

Field

Exemplary embodiments relate to a LiDAR (Light Detection And Ranging) system and an operating method thereof.

In general, a LiDAR system refers to a system that can irradiate laser onto an object, analyze light reflected and returned by the object, and detect the distance to the object, and the direction, speed, temperature, material distribution and concentration of the object.

Discussion of the Background

FIG.1illustrates a part of an optical system of a LiDAR system according to the related art. The optical system of the LiDAR system reflects transmitted/received beams through first and second mirrors110and120having a vertical structure. The first and second mirrors110and120have different fields of view (FOVs). Therefore, when three pairs of transmitters and receivers130and140are applied, the optical system has the same effect as that obtained by six pairs of transmitters/receivers. The LiDAR system according to the related art has a disadvantage in that the amount of received light is reduced depending on the FOV. As the angle at which light is reflected by the first and second mirrors110and120becomes an obtuse angle, the detectable distance to the object may decrease toward the edge of a scan region. Such a problem occurs because the light receiving area differs depending on angles and is further narrowed at an obtuse angle. Another problem is that the maximum FOV of the first and second mirrors110and120is limited to 145 degrees.

The related art may include technical information which the present inventor has retained to derive the present invention or has acquired during the process of deriving the present invention. The related art may not be necessarily a publicly known technique which was published to the public before the application of the present invention.

SUMMARY

Exemplary embodiments of the present invention are directed to a LiDAR (Light Detection And Ranging) system capable of maximizing a FOV while reducing a hardware unit price and size.

Also, embodiments of the present invention are directed to a LiDAR system having a sensing function in addition to a horizon detection function.

In one embodiment, a LiDAR system may include: a transmitter configured to output pulse laser; a reflecting mirror including two or more reflecting surfaces to reflect the pulse laser; a driver configured to rotate the reflecting mirror; a path control mirror configured to reflect the pulse laser to the reflecting surfaces of the reflecting mirror to form an optical path of the pulse laser; and a receiver configured to receive the light reflected through the reflecting mirror, and convert the received light into an electrical signal, wherein the reflecting mirror includes: a first reflecting surface; and a second reflecting surface, wherein the first and second reflecting surfaces are connected to each other at one point, the first reflecting surface and the second reflecting surface have different tilt angles from each other, and the first reflecting surface is tilted in the opposite direction of the second reflecting surface.

The first reflecting surface may reflect the pulse laser in a first direction parallel to a horizontal plane, and the second reflecting surface may reflect the pulse laser in a second direction perpendicular to the horizontal plane.

The first and second reflecting surfaces connected to each other at the one point may have V-shaped grooves corresponding to each other.

The driver may include a motor configured to rotate the reflecting mirror 360 degrees.

The LiDAR system may further include a controller configured to calculate the distance to an object and the speed of the object, using the electrical signal converted by the receiver.

The controller may adaptively change a pulse width of the pulse laser transmitted by the transmitter, a transmission repetition rate including the number of pulse lasers transmitted by the transmitter within a preset time, a reception repetition rate including the number of reflected lights received by the receiver within the preset time, and a power value of the pulse laser, according to the distance to the object and the speed of the object.

In another embodiment, an operating method of a LiDAR system may include: outputting, by a transmitter, pulse laser; reflecting, by a path control mirror, the pulse laser to form an optical path of the pulse laser; reflecting, by a reflecting mirror, the pulse laser reflected by the path control mirror, wherein the reflecting mirror is rotated by a driver and includes first and second reflecting surfaces which are connected to each other at one point and have different tilt angles; and receiving, by a receiver, light reflected through the reflecting mirror, and converting the received light into an electrical signal.

The first reflecting surface may reflect the pulse laser in a first direction parallel to a horizontal plane, and the second reflecting surface may reflect the pulse laser in a second direction perpendicular to the horizontal plane.

The operating method may further include rotating, by the driver, rotating the reflecting mirror 360 degrees.

The operating method may further include calculating, by a controller, the distance to an object and the speed of the object, using the electrical signal converted by the receiver.

The operating method may further include adaptively changing, by the controller, a pulse width of the pulse laser transmitted by the transmitter, a transmission repetition rate including the number of pulse lasers transmitted by the transmitter within a preset time, a reception repetition rate including the number of reflected lights received by the receiver within the preset time, and a power value of the pulse laser, according to the distance to the object and the speed of the object.

In addition, another method and system for implementing the present invention and a computer program for executing the method may be further provided.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

As is traditional in the corresponding field, some exemplary embodiments may be illustrated in the drawings in terms of functional blocks, units, and/or modules. Those of ordinary skill in the art will appreciate that these block, units, and/or modules are physically implemented by electronic (or optical) circuits such as logic circuits, discrete components, processors, hard-wired circuits, memory elements, wiring connections, and the like. When the blocks, units, and/or modules are implemented by processors or similar hardware, they may be programmed and controlled using software (e.g., code) to perform various functions discussed herein. Alternatively, each block, unit, and/or module may be implemented by dedicated hardware or as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed processors and associated circuitry) to perform other functions. Each block, unit, and/or module of some exemplary embodiments may be physically separated into two or more interacting and discrete blocks, units, and/or modules without departing from the scope of the inventive concept. Further, blocks, units, and/or module of some exemplary embodiments may be physically combined into more complex blocks, units, and/or modules without departing from the scope of the inventive concept.

The advantages and characteristics of the present invention and a method for achieving the advantages and characteristics will be clarified through the following embodiments which will be described in detail with reference to the accompanying drawings. However, it should understood that the present invention is not limited to the following embodiments, can be embodied in various different forms, and includes all modifications, equivalents or substitutes which are included in the scope and technical range of the present invention. The following embodiments are provided to complete the disclosure of the present invention, such that the scope of the present invention can be fully understood by those skilled in the art to which the present invention pertains. Moreover, detailed descriptions related to publicly known functions or configurations will be ruled out in order not to unnecessarily obscure subject matters of the present invention.

The terms used in this application are only used to describe a specific embodiment, and not intended to limit the present invention. The terms of a singular form may include plural forms unless referred to the contrary. In this application, the meaning of “include” or “have” only specifies a property, number, step, operation, component, part or combinations thereof, and does not exclude one or more other properties, numbers, steps, operations, components, parts or combinations thereof. The terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only to distinguish one component from another component.

Hereafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following descriptions with reference to the accompanying drawings, the same or corresponding components will be denoted by like reference numerals, and duplicated descriptions thereof will be omitted.

FIG.2schematically illustrates the detailed configuration of a LiDAR (Light Detection And Ranging) system in accordance with an embodiment of the present invention,FIGS.3A and3Bschematically illustrate the detailed configuration of an optical unit in the LiDAR system ofFIG.2, andFIGS.4A and4Bare perspective and exploded perspective views of the LiDAR system in accordance with the embodiment of the present invention.

Referring toFIGS.2to4, the LiDAR system in accordance with the embodiment of the present invention may include a transmitter200, an optical unit300, a driver400, a receiver500, a signal processor600, a controller700and a housing800. In the present embodiment, the optical unit300may include a path control mirror310, a reflecting mirror320and a light receiving lens330, the reflecting mirror320including a first reflecting surface321and a second reflecting surface322. Although not illustrated, the optical unit300may further include a light transmitting lens. The light transmitting lens may be included in the transmitter200, and the light receiving lens330may be included in the receiver500.

The transmitter200may generate pulse laser and transmit the generated pulse laser to the optical unit300, under control of the controller700. The pulse laser generated by the transmitter200may be transmitted to the optical unit300through the light transmitting lens. A method based on the pulse laser may be divided into a ToF (Time of Flight) method and a PS (Phase Shift) method, depending on a signal modulation method. The ToF method may indicate a method that measures a distance by emitting a pulse laser signal and measuring the times at which pulse signals reflected from objects within a measurement range reach the receiver500. The PS method may indicate a method that calculates a time and distance by emitting a pulse laser signal which is sequentially modulated with a specific frequency, and measuring a phase shift of a signal reflected and returned from an object within a measurement range.

The optical unit300may reflect pulse laser from the transmitter200, and transmit the reflected pulse laser to an object. Furthermore, the optical unit300may transmit light to the receiver500, the light being reflected by the object in response to the received pulse laser. In the present embodiment, the optical unit300may include the path control mirror310, the reflecting mirror320and the light receiving lens330, the reflecting mirror320including the first reflecting surface321and the second reflecting surface322.

The path control mirror310may reflect the pulse laser from the transmitter200to the reflecting mirror320. That is, when the pulse laser from the transmitter200reaches the path control mirror310, the path control mirror310may reflect the pulse laser to the reflecting mirror320to form an optical path of the pulse laser.

The reflecting mirror320may include two or more reflecting surfaces, reflect pulse laser to transmit to an object, and reflect light reflected from the object to the light receiving lens330. In an embodiment, the reflecting mirror320may include the first and second reflecting surfaces321and322. However, the reflecting mirror320is not limited thereto, but the number of reflecting surfaces can be increased or decreased.

In an embodiment, the first and second reflecting surfaces321and322may be connected to each other at one point (323inFIG.3), the tilt angle (θ1inFIG.3) of the first reflecting surface321and the tilt angle (θ2inFIG.3) of the second reflecting surface322may be different from each other, and the first reflecting surface321may be tilted in the opposition direction of the second reflecting surface322. Compared to the related art, the first and second reflecting surfaces321and322may not be formed at right angles, but diagonally tilted at an angle of approximately 45 degrees. In this case, since the first and second reflecting surfaces321and322have the same light receiving area depending on a tilt angle, the same distance may be detected according to the tilt angle. Furthermore, since there is no limit to the maximum FOV, 360-degree scanning can be performed. The first and second reflecting surfaces321and322may have V-shaped grooves corresponding to each other.

In the present embodiment, the first reflecting surface321may reflect pulse laser in a first direction (horizontal direction) parallel to a horizontal plane, and the second reflecting surface322may reflect pulse laser in a second direction (ground direction) which is oblique to the horizontal plane. In the related art, the reflecting mirrors for detecting the first and second directions have been separately developed. In the present embodiment, however, since the driver400rotates the reflecting mirror320, both of the first and second directions can be detected through the first and second reflecting surfaces321and322. Therefore, when such a structure is applied to a parking system, for example, a bump or parking stopper as well as a surrounding object or parking lot structure can be easily detected. In addition, since a coaxial structure in which transmission and reception optical axes are the same is applied instead of a biaxial structure, the minimum detection distance of Om can be achieved.

The reflecting mirror320may be covered by a cover window810, thereby forming the housing800. The cover window810may be formed of a material through which pulse laser and light reflected from an object can easily pass.

The light receiving lens330may transmit the light reflected through the first and second reflecting surfaces321and322to the receiver500.

The driver400may include a motor (not illustrated) capable of rotating the reflecting mirror320, and the rotational speed of the motor may be controlled by the controller700. In the present embodiment, the driver400may further a shaft (not illustrated) to support the reflecting mirror320, and the motor may be installed under the shaft. In an embodiment, the motor can rotate 360 degrees.

The receiver500may convert the light received by the light receiving lens330into an electrical signal. The receiver500may include a photodetector (not illustrated) to convert the received light into an electrical signal. The electrical signal detected by the photodetector may be outputted as an image signal through the signal processor600, and the image signal may be provided in such a manner that a user can watch the image signal through a display device (not illustrated) such as a navigation system of the vehicle.

The signal processor600may amplify the electrical signal converted by the receiver500, and transmit the amplified signal to the controller700. Furthermore, the signal processor600may receive control signals for the transmitter200, the optical unit300, the driver400and the receiver500from the controller700, convert the received signals into signals suitable for the corresponding components, and transmit the converted signals to the respective components.

The controller700may control the operations of the entire components from the transmitter200to the signal processor600, and calculate the distance to an object and the speed of the object, based on the electrical signal which is converted by the receiver500and amplified by the signal processor600. The distance to the object and the speed of the object, which are calculated by the controller700, may also be calculated by the signal processor600. That is, the signal processor600may be included in the controller700.

The controller700may adaptively change the pulse width of the pulse laser transmitted by the transmitter200, a transmission repetition rate including the number of pulse lasers transmitted by the transmitter200within a preset time, a reception repetition rate including the number of reflected lights received by the receiver500within a preset time, and the power value of the pulse laser, depending on the distance to the object and the speed of the object.

When the power of transmitted pulse laser is lowered and the transmission repetition rate and the reception repetition rate are raised, the resolution of the scan angle can be increased. Here, raising or lowering the power of the pulse laser may have the same effect as increasing or decreasing the pulse width of the pulse laser. Furthermore, when the number of received data used for distance detection is reduced, the detection distance may be increased while the angle resolution is decreased. Based on such characteristics, the distance detection, the detection interval and the detection performance may be variably applied according to the speed of the vehicle, depending on an indoor or outdoor situation.

For example, in order to detect the first direction, the pulse width of pulse laser may be increased, the power of the pulse laser may be raised, or the transmission repetition rate and the reception repetition rate may be raised to detect a long distance. In order to detect the second direction, the reverse parameters may be applied. That is, the pulse width of the pulse laser may be decreased, the power of the pulse laser may be lowered, and the transmission repetition rate and the reception repetition rate may be lowered. Furthermore, the pulse width of pulse laser with a specific pattern, the power of the pulse laser, and the transmission repetition rate and the reception repetition rate may be adjusted to remove interference between sensors.

FIGS.5A to5Cillustrate a sensing area of the LiDAR system according to the related art and a sensing area of the LiDAR system in accordance with the embodiment of the present invention.FIG.5Aillustrates the sensing area of the LiDAR system according to the related art, andFIGS.5B and5Cillustrate the sensing area of the LiDAR system in accordance with the embodiment of the present invention.

Referring toFIG.5A, the LiDAR system according to the related art needs to separately include the mirrors for sensing the first and second directions, and the maximum FOV is limited to 145 degrees. Referring toFIGS.5B and5C, however, the LiDAR system in accordance with the present embodiment can sense the first and second directions at the same time and perform 360-degree scanning without a limit to the maximum FOV, because the first and second reflecting surfaces are diagonally tilted at an angle of approximately 45 degrees.

FIG.6is a flowchart illustrating an operating method of the LiDAR system in accordance with an embodiment of the present invention. Hereafter, descriptions overlapping with the descriptions ofFIGS.1to5will be omitted.

Referring toFIG.6, the transmitter200of the LiDAR system may generate pulse laser and transmit the generated pulse laser through the light transmitting lens, under control of the controller700, at step S610.

At step S620, the path control mirror310of the optical unit300may reflect the received pulse laser to the reflecting mirror320, and the reflecting mirror320may reflect the pulse laser to transmit to an object.

In an embodiment, the reflecting mirror320may include the first and second reflecting surfaces321and322. Upper edges of the first and second reflecting surfaces321and322may be connected to each other, the tilt angle of the first reflecting surface321and the tilt angle of the second reflecting surface322may be different from each other, and the first reflecting surface321may be tilted in the opposite direction of the second reflecting surface322. The first and second reflecting surfaces321and322may have V-shaped grooves corresponding to each other. In the present embodiment, the first reflecting surface321may reflect the pulse laser in the first direction (horizontal direction) parallel to a horizontal plane, and the second reflecting surface322may reflect the pulse laser in the second direction (ground direction) perpendicular to the horizontal plane. Since the driver400rotates the reflecting mirror320, both of the first and second directions can be sensed through the first and second reflecting surfaces321and322.

At step S630, the light reflected from the object may be reflected through the first and second reflecting surfaces321and322of the reflecting mirror320of the optical unit300.

At step S640, the light reflected by the reflecting mirror320may be transmitted to the receiver500through the light receiving lens, and the receiver500may convert the reflected light into an electrical signal.

At step S650, the controller700may calculate the distance to the object and the speed of the object using the electrical signal converted by the receiver500.

The controller700may adaptively change the pulse width of the pulse laser transmitted by the transmitter200, a transmission repetition rate including the number of pulse lasers transmitted by the transmitter200within a preset time, a reception repetition rate including the number of reflected lights received by the receiver500within a preset time, and the power value of the pulse laser, depending on the distance to the object and the speed of the object.

In accordance with the embodiments of the present invention, it is possible to maximize the FOV while reducing a hardware unit price and size.

Furthermore, the LiDAR system can perform ground detection as well as horizontal detection.

The above-described embodiments of the present invention may be implemented in the form of computer programs which can be executed on a computer through various components, and the computer programs may be recorded in a computer readable medium. At this time, the medium may include a magnetic medium such as a hard disk, floppy disk or magnetic tape, an optical recording medium such as a CD-ROM or DVD, a magneto-optical medium such as a floptical disk, and a hardware device such as a ROM, RAM or flash memory, which is specifically configured to store and execute program commands.

The computer program may include an available program which is specifically designed and configured for the present invention, or publicly known to those skilled in the computer software field. Examples of the computer program may include high-level language codes which can be executed by a computer through an interpreter, as well as machine language codes which are generated by a compiler.

In the specification (or particularly claims) of the present invention, the use of the term “the” and directional terms similar to “the” may correspond to a singular form or plural forms. Furthermore, when a range is described in the present invention, it may indicate that the present invention includes an embodiment to which individual values belonging to the range are applied (unless referred to the contrary), and the individual values constituting the range are described in the detailed descriptions of the invention.

The steps constituting the method in accordance with the embodiment of the present invention may be performed in suitable order, when the order of the steps is clearly specified or unless referred to the contrary. The present invention is not limited to the order of the steps. In the present invention, all examples or exemplary terms (for example, and the like) are simply used to describe the present invention in detail. The scope of the present invention is not limited by the examples or exemplary terms, as long as the scope of the present invention is not limited by claims. Furthermore, it is obvious to a person skilled in the art that various modifications, combinations and changes can be made according to design conditions and factors within the scope of claims or equivalents.

Therefore, the spirit of the present invention is not limited to the above-described embodiments, and all ranges which are equivalent to the following claims or equivalently changed from the claims, as well as the claims, may be considered as being included in the sprit of the present invention.