KR102480883B1 - Lidar sensor for vehicle - Google Patents

Abstract

The present application uses a single sensor, a TOF direct operation mode, a TOF in-direct operation mode in which the distance to the target is measured from the phase difference between the light irradiated to the target and the light reflected by the target, and the TOF direct/return mode. By controlling to selectively operate in any one of the in-direct simultaneous operation modes, a vehicle lidar sensor capable of accurately measuring the distance to the target by applying the in-direct method within the measurement distance range of the TOF direct method is provided. do.

Description

Lidar sensor for vehicle {Lidar sensor for vehicle}

The present application relates to a vehicle lidar sensor, and specifically, a single sensor selectively operating in any one of a TOF direct single operation mode, a TOF in-direct single operation mode, and a TOF direct/in-direct simultaneous operation mode. A technical idea for improving distance measurement accuracy to a target is disclosed.

LiDAR sensor is a technology for measuring distance using light and can be interpreted in the same sense as laser radar.

It can be seen as a radar developed using laser beams with properties close to radio waves. Although lasers were initially developed for communication, they are used for various purposes other than communication because they have dual characteristics of light and radio waves due to strong monochromaticity.

In particular, if the speed of light is always constant, distance measurement is possible. Specifically, the distance can be accurately measured by accurately measuring the time it takes for light irradiated from a light source near the camera to reflect back on an object, which is called Time-of-flight (TOF) technology.

There are two main types of TOF technology, a direct method and an in-direct method.

The direct method is a method of directly measuring time by irradiating light in the form of a pulse, receiving reflected light, and measuring the time between them. At this time, considering the speed of light, precision can be improved because the pulse width must be made as small as possible.

In addition, since a distance of 100 m is very short enough to be converted into a TOF of 667 ns, a precise time-to-digital converter is required and the sensitivity of the light receiving element must be very high.

The light receiving element of a sensor used in a general camera measures the received light for a long time of about 30 ms, and considering this, the sensitivity of the direct TOF light receiving element must be very high.

Therefore, in the direct method, an avalanche photodiode (APD) or a single photon avalanche diode (SPAD) can be used as a light receiving element.

SPAD, as its name suggests, can send out digital pulses in response to even one photon entering. The advantages of this method are that it is theoretically possible to measure at a long distance because there is no restriction on distance, and that the device has a wide dynamic range and is robust against external light such as sunlight.

However, SPAD is larger than a general photodiode, and since the time between the irradiated light pulse and the SPAD response output pulse must be digitized and stored, a large memory is required, making it difficult to implement high spatial resolution. there is.

On the other hand, lidar sensors used for vehicles require high resolution because all front images must be obtained. In recent years, various technologies for improving the resolution of a lidar sensor for a vehicle are being developed. LiDAR sensors currently under development or commercialized require a driving unit that rotates the sensor to improve resolution. However, when the driving unit for rotating the sensor is mounted on a vehicle, it is easily affected by vibration and it is difficult to obtain a reliable result.

The in-direct method does not directly measure time, but modulates and irradiates light and then measures a phase difference with reflected light to extract a distance.

Therefore, there is no need for a time digital converter for time measurement, and since it does not have all the time data for the irradiated light pulse, there is no need for memory, so the size is smaller than that of the direct method. Therefore, it is possible to increase the spatial resolution. Nevertheless, the in-direct method can only measure a distance corresponding to a period of a modulated wave, and has limitations in being vulnerable to external light.

The present invention improves distance measurement accuracy to a target by applying the TOF in-direct method within the measurement distance range of the TOF direct method using a single sensor capable of implementing the direct method and the in-direct method of the TOF technology alone or simultaneously. Its purpose is to provide a lidar sensor for vehicles.

A light source for irradiating light to a target on the front of a vehicle lidar vehicle according to an embodiment; A single sensor provided to measure the distance to the target by measuring the time for the light irradiated to the target to be reflected back by the target and the phase difference of the light; and a TOF direct operation mode in which the distance to the target is measured by measuring the time for the light irradiated to the target to be reflected by the target and return by controlling the light source and the single sensor, and the light irradiated to the target and the target and a control unit for controlling to operate in at least one operation mode of a TOF in-direct single operation mode and a TOF direct/in-direct simultaneous operation mode that measures the distance to a target from the phase difference of light reflected and returned by the vehicle. It provides a sensor.

A vehicle lidar sensor according to an embodiment of the present invention includes a single sensor operating in any one of a TOF direct single operation mode, a TOF in-direct single operation mode, and a TOF direct/in-direct simultaneous operation mode. Accordingly, it is possible to measure the distance to the target more precisely by applying the in-direct method within the measurement distance range of the TOF direct method.

1 is a diagram illustrating a lidar sensor according to an embodiment.
2 is a diagram illustrating pulse shapes of first and second lights irradiated by a light source according to an exemplary embodiment.

Specific structural or functional descriptions of the embodiments according to the concept of the present invention disclosed in this specification are only illustrated for the purpose of explaining the embodiments according to the concept of the present invention, and implementation according to the concept of the present invention Examples may be embodied in many forms and are not limited to the embodiments described herein.

Embodiments according to the concept of the present invention can apply various changes and can have various forms, so the embodiments are illustrated in the drawings and described in detail herein. However, this is not intended to limit the embodiments according to the concept of the present invention to specific disclosure forms, and includes modifications, equivalents, or substitutes included in the spirit and scope of the present invention.

Terms such as first or second may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another component, for example, without departing from the scope of rights according to the concept of the present invention, a first component may be named a second component, Similarly, the second component may also be referred to as the first component.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle. Expressions describing the relationship between elements, such as "between" and "immediately between" or "directly adjacent to" should be interpreted similarly.

Terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "have" are intended to designate that the described feature, number, step, operation, component, part, or combination thereof exists, but one or more other features or numbers However, it should be understood that it does not preclude the presence or addition of steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this specification, it should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, the scope of the patent application is not limited or limited by these examples. Like reference numerals in each figure indicate like elements.

1 is a diagram illustrating a lidar sensor according to an embodiment.

Referring to FIG. 1 , a lidar sensor according to an embodiment includes a light source 100, a single sensor 200, and a controller 300.

Specifically, the light source 100 radiates light to a target on the front of the vehicle. The single sensor 200 is provided to measure the distance to the target by measuring the time for the light irradiated to the target to be reflected by the target and return, and the phase difference of the light. In addition, the control unit 300 controls the light source 100 and the single sensor 200 to measure the time for the light irradiated to the target to be reflected by the target and return, thereby measuring the distance to the target directly. Single operation mode 310, TOF in-direct operation mode 320 that measures the distance to the target from the phase difference between the light irradiated to the target and the light reflected back by the target, and TOF direct/in-direct simultaneous operation Mode 330 is controlled to operate in at least one operation mode.

The lidar sensor according to the present application provides a direct measurement distance range through a single sensor 200 that selectively operates in a TOF direct single operation mode, a TOF in-direct single operation mode, and a TOF direct/in-direct simultaneous operation mode. It is possible to measure the precise distance to the target by applying the in-direct method within.

The TOF direct operation mode 310 measures the distance to the target through a time-to-digital converter and a histogramming circuit. For example, the TOF direct mode 210 directly measures the time to reflect and return from a target through a time-to-digital converter, converts it into a digital value, and calculates the time of reflected light through a histogramming circuit. Calculate precisely and measure the distance to the target. The TOF direct operation mode 310 can measure a distance to a relatively distant target.

In addition, the TOF in-direct operation mode 320 calculates the distance to the target by inverting the phase difference of the incoming light due to the light phase change after dividing the light pulse into three or more through a time-gate. Measure. The TOF in-direct operation mode 320 enables distance measurement to a relatively close target with high resolution.

In addition, the TOF direct/in-direct simultaneous operation mode 330 is a mode that complements the advantages and disadvantages of the above-mentioned single mode, and precise distance measurement using the TOF in-direct method is possible in the distance range of the TOF direct method.

In the TOF technology, since the direct method and the in-direct method are widely known technologies in the art, detailed descriptions thereof will be omitted in the present invention.

2 is a diagram illustrating pulse shapes of first and second lights irradiated by a light source according to an exemplary embodiment. Specifically, FIG. 2 (a) shows a pulse of the first light when the first light is irradiated alone, FIG. 2 (b) shows a pulse of the second light when the second light is irradiated alone, and FIG. 2 (c) represents pulses of the first and second lights when the first and second lights are simultaneously irradiated.

Referring to FIG. 2 , the control unit 300 determines that the light source 100 has a first light having a first frequency and a second light having a higher frequency than the first light according to the operation mode. Either one of the two lights may be selectively irradiated, or the first light and the second light may be simultaneously irradiated so that three or more pulses of the second light are emitted between pulse intervals of the first light.

Specifically, the TOF direct single mode 310 measures the distance to the target by using the first light in the form of a pulse having a first frequency, and the TOF in-direct single mode 320 measures the distance to the target by using a pulsed first light having a first frequency. The distance to the target is measured by the second light in the form of a pulse having a second frequency, and the TOF direct/in-direct simultaneous operation mode 330 measures the distance to the target by the first light and the second light by the Arrangements may be made to measure the distance to the target based on the distance to the target.

In another example, the single sensor 200 may be a SPAD sensor. SPAD, as the name suggests, can send out digital pulses in response to even one photon entering. The advantages of this method are that it is theoretically possible to measure at a long distance because there is no restriction on distance, and that the device has a wide dynamic range and is robust against external light such as sunlight.

Unlike conventional SPAD sensors that operate only in the TOF direct method, the SPAD sensor according to the present invention has a TOF direct operation mode (310), a TOF in-direct operation mode (320) and a TOF direct/in-direct operation mode (330). ), it is possible to precisely measure the distance to the target by applying the in-direct method within the measurement distance range of the TOF direct method.

In one embodiment, the control unit 300 is provided to adjust the pulse width, pulse interval, and phase difference of light emitted from the light source according to the operation mode. In particular, the control unit 300 can adjust the phase difference of light by adjusting the capacitor value. Adjusting the phase delay of the light is to operate a TOF in-direct single (or simultaneous) operation mode in which a distance to a target is measured through a phase difference.

For example, the controller 300 may control the light emitted from the light source 100 to have three or more different phase delays. By controlling the light to have a plurality of different phase delays, it is possible to implement a TOF in-direct operating mode in a sensor such as a SPAD.

As described above, although the embodiments have been described with limited drawings, those skilled in the art can make various modifications and variations from the above description. For example, the described techniques may be performed in an order different from the method described, and/or components of the described system, structure, device, circuit, etc. may be combined or combined in a different form than the method described, or other components may be used. Or even if it is replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims.

100: light source
200: single sensor
300: control unit
310: TOF direct stand-alone operation mode
320: TOF in-direct stand-alone operation mode
330: TOF direct/in-direct simultaneous operation mode

Claims (6)

a light source for radiating light to a target in front of the vehicle;
A single sensor provided to measure the distance to the target by measuring the time for the light irradiated to the target to be reflected by the target and return, and the phase difference of the light; and
TOF direct operation mode in which the distance to the target is measured by measuring the time for the light irradiated to the target to be reflected by the target and return by controlling the light source and the single sensor, and the light irradiated to the target and the target A control unit for controlling to operate in at least one operation mode of a TOF in-direct single operation mode and a TOF direct/in-direct simultaneous operation mode that measures a distance to a target from a phase difference of reflected light,
The control unit selectively irradiates any one of the first light in the form of a pulse having a first frequency and the second light in the form of a pulse having a second frequency higher than the first light according to the operation mode, or Or, a vehicle lidar sensor provided to simultaneously irradiate the first light and the second light so that three or more pulses of the second light having different pulse widths from the first light are generated between the pulse intervals of the first light. delete The method of claim 1 , wherein the TOF direct mode measures a distance to the target by using a first pulse-type light having a first frequency,
In the TOF in-direct mode alone, the distance to the target is measured by a second light having a pulse type having a second frequency higher than that of the first light,
The TOF direct / in-direct simultaneous operation mode is a vehicle lidar sensor provided to precisely measure the distance to the target based on the distance to the target by the first light and the distance to the target by the second light. The vehicle lidar sensor according to claim 1, wherein the single sensor is a SPAD sensor. According to claim 1,
The control unit is a vehicle lidar sensor provided to adjust the pulse width, pulse interval, and phase difference of the light emitted from the light source according to the operation mode. The vehicle lidar sensor according to claim 5, wherein the control unit controls the light emitted from the light source to have three or more different phase delays.

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