OBJECT DETECTION SYSTEM AND OBJECT DETECTION METHOD

Abstract

A laser sensor (110) comprises: a first main laser (111) that emits a laser beam having a first wavelength; a second main laser (112) that emits a laser beam having a second wavelength; a dummy laser (113) that emits a laser beam having a third wavelength; a first light-receiving element (114) having a sensitivity to beams having the first wavelength; and a second light-receiving element which has a sensitivity to beams having the second wavelength. The first main laser and the second main laser alternately emit the respective laser beams.

Description

Laser sensor, object detection system, and object detection method

[0001] FIELD OF THE DISCLOSURE This disclosure relates to laser-based object detection.

[0002] Some LiDAR measurements utilize the ToF principle. LiDAR stands for Light Detection and Ranging. ToF stands for Time of Flight.

[0003] Measurement using the ToF principle is a method of calculating distance based on the time it takes for laser light to be emitted and for the laser light (reflected light) to be reflected by a subject and received by a sensor.

[0004] LiDAR primarily uses near-infrared light with wavelengths of 903 or 905 nanometers. 1550-nanometer LiDAR is also under development. Longer wavelengths allow for longer distances. 900-nanometer LiDAR uses silicon (Si) for the light-receiving element. 1550-nanometer LiDAR uses indium gallium arsenide (InGaAs) for the light-receiving element.

[0005] One known attack against infrared sensors that measure the surrounding environment, such as LiDAR, is a spoofing attack using false reflected waves. Countermeasures against such spoofing attacks include redundancy or sensor fusion. However, attacks against self-driving cars that deceive the object detection signal processing of sensor fusion using cameras and LiDAR are known. Therefore, it is important to take measures against attacks on individual sensors, rather than relying solely on sensor fusion using multiple sensors.

[0006] Known countermeasures to attacks on sensors include random modulation, the use of multiple wavelengths, and reducing the light receiving angle. Random modulation FMCW LiDAR has been developed, but it is difficult to rotate and has a narrow measurement range. Performing 360-degree measurements requires multiple LiDARs, making it unsuitable for small devices such as drones. The use of multiple wavelengths allows attackers to launch low-cost attacks by using multiple wavelengths. Reducing the light receiving angle reduces the potential for attack. However, this requires the installation of multiple LiDARs, which is costly. There are use cases where a cost-effective countermeasure for sensor attacks is needed without increasing the number of LiDARs.

[0007] Patent Document 1 discloses a countermeasure against deception attacks on sensors, in which a deceptive signal is prepared to trick an attacker into believing that the deceptive signal is a true measurement signal, and the attacker then launches an attack against the deceptive signal.

[0008] Japanese Patent Application Publication No. 9-281397

[0009] Conventional countermeasures against spoofing attacks require multiple LiDARs, which are not applicable to small devices such as UAVs, and also involve financial and technical costs. UAV stands for Unmanned Aerial Vehicle.

[0010] No countermeasures have been proposed against attacks that deceive the sensor fusion signal processing.

[0011] The present disclosure aims to prevent erroneous object detection due to the influence of spoofing attacks.

[0012] The laser sensor of the present disclosure includes a main laser that irradiates laser light of a specific wavelength, a dummy laser that irradiates laser light of a wavelength different from the specific wavelength, and a light receiving element that is sensitive to light of the specific wavelength.

[0013] According to the present disclosure, it is possible to prevent erroneous object detection from being caused by the influence of a spoofing attack.

[0014] FIG. 1 is a configuration diagram of an object detection system 100 according to embodiment 1. FIG. 2 is a configuration diagram of a laser sensor 110 according to embodiment 1. FIG. 3 is a configuration diagram of an attack detection device 120 according to embodiment 1. FIG. 4 is a configuration diagram of an object detection device 130 according to embodiment 1. FIG. 5 is a functional configuration diagram of the object detection system 100 according to embodiment 1. FIG. 6 is a flowchart of an object detection method according to embodiment 1. FIG. 7 is a flowchart of an object detection method according to embodiment 1.

[0015] In the embodiments and drawings, the same or corresponding elements are denoted by the same reference numerals. The description of elements denoted by the same reference numerals as those already described will be omitted or simplified as appropriate. Arrows in the drawings primarily indicate the flow of signals, data, or processes.

[0016] First Embodiment An object detection system 100 will be described with reference to FIGS.

[0017] ***Description of Configuration*** The configuration of the object detection system 100 will be described based on Figure 1. The object detection system 100 is a system that detects an object 101 using a laser sensor 110. The object 101 is the object to be detected. In other words, the object 101 is the target to be sensed. The object detection system 100 includes a laser sensor 110, an attack detection device 120, and an object detection device 130. Specifically, the laser sensor 110 is a LiDAR. The LiDAR is an infrared sensor. Furthermore, the attack detection device 120 and the object detection device 130 are computers.

[0018] The configuration of the laser sensor 110 will be described with reference to FIG. 2 . The laser sensor 110 includes three types of lasers (111, 112, and 113). The first main laser 111 and the second main laser 112 are measurement lasers that emit laser light of different wavelengths. The first main laser 111 emits laser light of a first wavelength. Specifically, the first main laser 111 emits laser light of approximately 900 nanometers. The second main laser 112 emits laser light of a second wavelength. Specifically, the second main laser 112 emits laser light of approximately 1550 nanometers. The dummy laser 113 emits laser light of a third wavelength. The third wavelength is a wavelength between the first wavelength and the second wavelength. Specifically, the dummy laser 113 emits laser light of approximately 1000 nanometers.

[0019] The laser sensor 110 includes two types of light receiving elements (114, 115). The first light receiving element 114 is a light receiving element that is sensitive to light of a first wavelength. Specifically, the first light receiving element 114 is a light receiving element that uses a silicon (Si) semiconductor. The second light receiving element 115 is a light receiving element that is sensitive to light of a second wavelength. Specifically, the second light receiving element 115 is a light receiving element that uses an indium gallium arsenide (InGaAs) compound semiconductor.

[0020] The laser sensor 110 has a mechanism for rotating the three types of lasers (111, 112, 113) and two types of light-receiving elements (114, 115) as a whole in order to measure a wide range of the surroundings. For example, the laser sensor 110 has a rotation mechanism for measuring a 360-degree surrounding area. The rotation mechanism rotates the three lasers and two light-receiving elements as a whole through 360 degrees.

[0021] The configuration of the attack detection device 120 will be described with reference to FIG. 3. The attack detection device 120 includes hardware called a processing circuit 129. The attack detection device 120 includes an element called an attack detection unit 121. The processing circuit 129 is hardware that realizes the attack detection unit 121. The processing circuit 129 may be dedicated hardware, or may be a processor that executes a program stored in memory. The dedicated hardware may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field Programmable Gate Array.

[0022] The configuration of the object detection device 130 will be described with reference to Fig. 4. The object detection device 130 includes hardware called a processing circuit 139. The object detection device 130 includes an element called an object detection unit 131. The processing circuit 139 is hardware that realizes the object detection unit 131. The processing circuit 139 may be dedicated hardware, or may be a processor that executes a program stored in a memory.

[0023] FIG. 5 shows the relationship between elements in the object detection system 100. Three types of lasers (111, 112, 113) emit laser light. However, the two types of main lasers (111, 112) emit laser light alternately. Two types of light-receiving elements (114, 115) receive (detect) the laser light reflected from the object 101 and output a light-receiving signal. Light-receiving refers to receiving light and converting the received light into an electrical signal. Detection refers to regarding the electrical signal as point cloud data. If the amount of light is greater than a threshold, the electrical signal is recognized as point cloud data. Electrical signals that are not recognized as point cloud data are discarded as unnecessary data. The light-receiving signal is an electrical signal that has been received and detected, and represents laser light. The attack detection unit 121 receives the light-receiving signal, detects an attack by the attack device 109, and outputs a light-receiving signal indicating that there is no attack. The object detection unit 131 processes the light-receiving signal indicating that there is no attack to detect the object 101.

[0024] The attacking device 109 is a device that performs a spoofing attack. The attacking device 109 detects laser light emitted from the three types of lasers and emits jamming laser light.

[0025] ***Description of Operation*** The procedure of operation of the object detection system 100 corresponds to an object detection method.

[0026] The object detection method will be described with reference to Figures 6 and 7. The operation of the laser sensor 110 in the object detection method will be described with reference to Figure 6. In step S101, the first main laser 111 and the second main laser 112 alternately irradiate laser light. In addition, the dummy laser 113 continues to irradiate laser light.

[0027] The first main laser 111 radiates laser light of a first wavelength. The laser light of the first wavelength is referred to as the first laser light. The second main laser 112 radiates laser light of a second wavelength. The laser light of the second wavelength is referred to as the second laser light. The dummy laser 113 radiates laser light of a third wavelength. The laser light of the third wavelength is referred to as the dummy laser light.

[0028] The first laser light, the second laser light, and the dummy laser light each hit the object 101 and are reflected.

[0029] When the attack device 109 detects the first laser beam, the second laser beam, or the third laser beam, it emits a jamming laser beam. The jamming laser beam is referred to as an attack laser beam.

[0030] In step S102, the first light receiving element 114 and the second light receiving element 115 receive the laser light.

[0031] The first light receiving element 114 detects the first laser light. If the wavelength of the attack laser light is close to the first wavelength, the first light receiving element 114 detects the first laser light and the attack laser light. On the other hand, the second laser light and the dummy laser light are not detected by the first light receiving element 114. The second light receiving element 115 detects the second laser light. If the wavelength of the attack laser light is close to the second wavelength, the second light receiving element 115 detects the second laser light and the attack laser light. On the other hand, the first laser light and the dummy laser light are not detected by the second light receiving element 115.

[0032] In step S103, the first light receiving element 114 and the second light receiving element 115 output light receiving signals. The light receiving signal output from the first light receiving element 114 is referred to as a first light receiving signal. The light receiving signal output from the second light receiving element 115 is referred to as a second light receiving signal.

[0033] The operation of the attack detection device 120 and the object detection device 130 in the object detection method will be described with reference to Fig. 7. In step S111, the attack detection unit 121 receives light reception signals from the first light receiving element 114 and the second light receiving element 115.

[0034] In step S112, the attack detection unit 121 determines the S / N ratio of the received light signal. The S / N ratio means the signal-to-noise ratio.

[0035] The S / N ratio of the received light signal is determined as follows: First, the attack detection unit 121 calculates the S / N ratio of the received light signal. Then, the attack detection unit 121 compares the S / N ratio with a threshold value. If the S / N ratio is equal to or greater than the threshold value, the attack detection unit 121 determines that the S / N ratio is good. If the S / N ratio is less than the threshold value, the attack detection unit 121 determines that the S / N ratio is poor.

[0036] If the S / N ratio is good, the process proceeds to step S113. If the S / N ratio is poor, the received light signal is considered to be a dummy laser light signal. Therefore, the received light signal is removed as an unnecessary point cloud. In other words, the received signal is removed as an electrical signal that does not become point cloud data. Then, the process ends without object detection being performed.

[0037] In step S113, the attack detection unit 121 determines whether the first light receiving signal from the first light receiving element 114 and the second light receiving signal from the second light receiving element 115 are received simultaneously. If the first light receiving signal and the second light receiving signal are not received simultaneously, the process proceeds to step S114. If the first light receiving signal and the second light receiving signal are received simultaneously, one of the light receiving signals is considered to be an attack signal. Therefore, the light receiving signal is processed as a false reflected wave. This means that although the light receiving signal is valid point cloud data, it is an attack signal, and therefore the point cloud is removed so as not to affect subsequent applications. The subsequent application means, for example, processing by the processing circuit 139. The process then ends.

[0038] In step S114, the attack detection unit 121 determines whether it has received both the first light receiving signal from the first light receiving element 114 and the second light receiving signal from the second light receiving element 115. If both the first light receiving signal and the second light receiving signal have been received, the attack detection unit 121 outputs the first light receiving signal and the second light receiving signal, respectively. Then, the process proceeds to step S121. If at least one of the first light receiving signal and the second light receiving signal has not been received, the received light receiving signal is considered to be an attack signal. Therefore, object detection is not performed and the process ends.

[0039] In step S121, the object detection unit 131 receives the first light reception signal and the second light reception signal. Then, the object detection unit 131 performs object detection using at least one of the first light reception signal and the second light reception signal. In this way, the subject 101 is detected.

[0040] The object detection process involves the following steps: The object detection unit 131 calculates the relative distance at the measurement time based on the time of flight of the laser light. The relative distance is the distance from the laser sensor 110 to the subject 101, and is calculated by multiplying the time of flight by the speed of light. The time of flight is the time from when the laser light is emitted until when the laser light is received (detected). The time of flight is measured based on, for example, the clock count of the internal circuit. The measurement time is the time when the laser light is emitted or the time when the laser light is received (detected).

[0041] After step S121, the process ends.

[0042] Steps S101 to S121 are repeatedly executed.

[0043] ***Effects of First Embodiment*** The first embodiment makes it possible to counter deception attacks on sensors and advanced attacks that deceive sensor fusion. The first embodiment makes it possible to significantly reduce the attacker's ability to launch deception attacks. The attacker can install a new mechanism to remove signals with a poor S / N ratio. However, attacks that overcome sensor fusion require the insertion of point clouds in specific locations, which is difficult to achieve if the degree of freedom of the attack is reduced. Furthermore, since the attacker needs to add a new mechanism in addition to the attack mechanism, it is expected that the attacker's attack costs will increase.

[0044] Summary of First Embodiment In the following description, elements corresponding to those in the first embodiment are enclosed in parentheses, with the reference numerals of the elements in the first embodiment inside the parentheses. The infrared sensor (110) is characterized by its configuration and detection signal processing. An approximately 900 nm laser (111) and an approximately 1550 nm laser (112) are alternately irradiated. However, when the approximately 900 nm laser light is irradiated, the approximately 1550 nm laser light is received but not processed as a point cloud. Similarly, when the approximately 1550 nm laser light is irradiated, the approximately 900 nm laser light is received but not processed as a point cloud. The approximately 1000 nm laser light is irradiated but is treated as dummy light that is not received. The Si light receiving element (114) and the InGaAs light receiving element (115) respond to light with a wavelength of approximately 1000 nm, but the signal S / N ratio is poor. Therefore, light signals with wavelengths of approximately 1000 nm are removed in the processing step of forming the point cloud.

[0045] Signal processing for attack detection distinguishes between true reflected waves and false reflected waves (signals from an attacker). First, if light of the same wavelength arrives from the same position during alternating measurements, the received light is considered a false reflected wave. This prevents laser irradiation attacks using either wavelengths of approximately 900 nm or approximately 1550 nm. Second, if light from both an approximately 900 nm laser (111) and an approximately 1550 nm laser (112) arrives simultaneously, the received light is considered a false reflected wave. This is because approximately 900 nm light and approximately 1550 nm light are emitted alternately, so only one of the lights should be detected at a time. Even if an attacker prepares a laser irradiation attack device (109) for both wavelengths, the attacker's light receiving mechanism will react to the approximately 1000 nm dummy light, causing the laser irradiation attack device to emit laser light of both wavelengths. This makes it possible to detect the attack. This is because the attacker does not have a signal processing mechanism to remove signals with poor S / N ratios.

[0046] The first embodiment is characterized by using dummy light with low measurement sensitivity of the light receiving elements (114, 115). By using light that can be measured as dummy light, rather than completely invisible light, it is possible to induce an attack by an attacker and remove false signals.

[0047] *** Supplementary Note to First Embodiment *** The light reception signal output from the attack detection unit 121 is used, for example, for object detection based on a set of point clouds and for mapping the surrounding environment.

[0048] An attack that overcomes sensor fusion cannot be carried out by simply shining light onto an object; it is necessary to shine light in a way that causes a point cloud to appear in a specific location and a specific pattern. For example, a specific location would be behind an obstruction such as a car. For example, a specific pattern would be to shine light in such a way that the point cloud appears as a cone. It is difficult to shine light onto a moving object, and to successfully carry out an attack, a high degree of freedom in the attack (few conditions for the attack to be successful) is required. Therefore, if the degree of freedom in the attack is reduced, it becomes difficult to carry out.

[0049] The first embodiment is an example of a preferred embodiment and is not intended to limit the technical scope of the present disclosure. The first embodiment may be implemented in part or in combination with other embodiments.

[0050] The laser sensor 110 may not include one of the first main laser 111 and the second main laser 112. The attack detection device 120 and the object detection device 130 may be realized by a single device.

[0051] The procedures explained using the flowcharts etc. may be changed as appropriate. The order of steps S112, S113 and S114 may be interchanged.

[0052] The "part" of each element of the attack detection device 120 and the object detection device 130 may be read as "processing," "step," "circuit," or "circuitry."

[0053] The program can be recorded (stored) in a computer-readable manner on a non-volatile recording medium such as an optical disk or flash memory.

[0054] 100 Object detection system, 101 Subject, 109 Attack device, 110 Laser sensor, 111 First main laser, 112 Second main laser, 113 Dummy laser, 114 First light receiving element, 115 Second light receiving element, 120 Attack detection device, 121 Attack detection unit, 129 Processing circuit, 130 Object detection device, 131 Object detection unit, 139 Processing circuit.

Claims

1. a first main laser that irradiates a laser beam having a first wavelength, and a second main laser that irradiates a laser beam having a second wavelength, the first main laser and the second main laser alternately irradiate the laser light, a dummy laser that irradiates a laser beam having a third wavelength; a first light receiving element that is sensitive to light of the first wavelength, detects a laser beam, and outputs a first light receiving signal that is a signal of the detected laser beam; a second light receiving element that is sensitive to light of the second wavelength, detects the laser light, and outputs a second light receiving signal that is a signal of the detected laser light; an attack detection unit that receives the output first light receiving signal and the output second light receiving signal, determines a signal-to-noise ratio of the received first light receiving signal and the received second light receiving signal, and determines whether the first light receiving signal and the second light receiving signal are received simultaneously; an object detection unit that performs object detection using at least one of the first light receiving signal determined to have a good signal-to-noise ratio and the second light receiving signal determined to have a good signal-to-noise ratio when it is not determined that the first light receiving signal and the second light receiving signal are received simultaneously; An object detection system comprising:

2. Alternately irradiating a laser beam having a first wavelength and a laser beam having a second wavelength; Irradiating the laser light having a third wavelength; a first light receiving signal outputted from the first sensor which is sensitive to light of the first wavelength and detects the laser light; a second light receiving signal outputted from the second light receiving element, which is sensitive to light of the second wavelength and detects the laser light; receiving the output first light receiving signal and the output second light receiving signal, determining a signal-to-noise ratio of the received first light receiving signal and the received second light receiving signal, and determining whether the first light receiving signal and the second light receiving signal are received simultaneously; When it is not determined that the first light receiving signal and the second light receiving signal are received simultaneously, object detection is performed using at least one of the first light receiving signal determined to have a good signal-to-noise ratio and the second light receiving signal determined to have a good signal-to-noise ratio. Object detection methods.