KR20210072671A - Lidar module - Google Patents

Abstract

The present invention relates to a LIDAR module, which comprises: a transmission unit which includes a pulse modulation unit which modulates a cycle or amplitude of a pulse, a light source unit which outputs an optical signal based on the modulated pulse, a scanner which uses one or more mirrors to adjust a path of the optical signal, and radiate the optical signal with the path adjusted to the outside, and a controller which controls the scanner; and a reception unit which includes a reception lens which receives a reflection signal generated by the optical signal reflected by an object, and which collects the reflection signal, a light detector which converts the reflection signal into an electric signal, and a data processing unit which acquires and analyzes information on the object based on the electric signal. The light detector acquires a signal reception rate based on the reflection signal, and provides the signal reception rate to the pulse modulation unit. The pulse modulation unit modulates the pulse based on the signal reception rate, and provides an area, which has acquired a signal reception rate which is lower than a preset reference value, with a pulse with a shortened cycle or a modulated pulse whose amplitude has increased. The present invention relates to a LIDAR module which is able to increase a signal detection rate without an increase in electric power.

Description

LIDAR MODULE

The present invention relates to lidar technology, and more particularly, to a light source modulation lidar module based on reflected signal characteristics.

LiDAR (Light Detection And Ranging, LIDAR) technology is a technology that can detect the distance, direction, speed, temperature, material distribution and concentration characteristics of an object by shining a laser on the target. LiDAR technology continues to advance for the purpose of earth science and space exploration. Currently, lidar technology is mounted on aircraft and satellites and is used as an important means for precise observation of the earth's topography and environment. In addition, lidar technology is being used as a core technology for a simple lidar sensor for long-distance measurement and vehicle speed violation control, a laser scanner for 3D image restoration, and a 3D image sensor for future driverless cars.

As a representative example, a recent autonomous driving system uses a lidar technology that uses a laser as a light source to accurately detect surrounding environment information. In order to recognize precise environmental information, lidar uses a scanner, etc. to irradiate a laser into space to acquire information on the size, shape, and danger of an object, and implement a 3D image based on the acquired information. In order to closely analyze the surrounding environment information based on such a three-dimensional image, it is necessary to acquire information on all points to be analyzed. In addition, in order to increase the signal detection rate of the lidar, a high intensity light detector and a strong light source are basically required.

However, it is difficult to obtain accurate information about the surrounding environment due to the reflection angle between the optical signal transmitted from the scanner and the reflector and various reflectance characteristics of the reflector. In addition, if a light source with excessive intensity is used, it may be dangerous to visual safety, and in the case of a high reflectivity object, it is caused by a full-well phenomenon beyond the dynamic range, which is the signal reception range of the photodetector. There is a problem in that a saturation phenomenon may occur. These problems may affect signal acquisition of neighboring pixels and accurate distance information acquisition.

An object of the present invention is to provide a light source modulation lidar module based on reflected signal characteristics.

The lidar module according to an embodiment of the present invention uses a pulse modulator for modulating the period or amplitude of a pulse, a light source for outputting an optical signal based on the modulated pulse, and at least one mirror to route the optical signal. A transmitter comprising a scanner for emitting an optical signal whose path is adjusted and adjusted to the outside, and a controller for controlling the scanner, and a reception for receiving a reflected signal generated by reflecting the optical signal by an object and condensing the reflected signal A lens, a photodetector that converts the reflected signal into an electric signal, and a receiver including a data processing unit that obtains and analyzes information about the object based on the electric signal, wherein the photodetector is based on the reflected signal A signal reception rate is obtained and provided to the pulse modulator, and the pulse modulator modulates the pulse based on the signal reception rate, but a pulse or amplitude having a shorter period is present in an area in which a signal reception rate lower than a preset reference value is obtained. Provides increased modulation pulses.

According to the lidar module according to the present invention, it is possible to increase the signal detection rate without increasing the power by irradiating an optimized signal to each point existing in the scan area through pulse modulation, and to implement an improved three-dimensional image.

1 is a block diagram schematically showing a lidar module according to an embodiment of the present invention.
2 is a block diagram schematically showing a transmitter of a lidar module according to an embodiment of the present invention.
3 is a block diagram schematically showing a receiver of a lidar module according to an embodiment of the present invention.
4 is a block diagram for explaining in detail the operation of the lidar module according to an embodiment of the present invention.
5A and 5B are graphs illustrating pulse modulation patterns according to the number of internal bits.
6A to 6C are diagrams illustrating a maximum scan range of a lidar module according to an embodiment of the present invention.
7 is a flowchart illustrating a method of operating a lidar module according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described clearly and in detail to the extent that those skilled in the art can easily practice the present invention.

The terminology used herein is for the purpose of describing the embodiments, and is not intended to limit the present invention. As used herein, the singular also includes the plural unless the phrase specifically dictates otherwise. As used herein, “comprises and/or comprises” refers to the presence or addition of one or more other components, steps, acts and/or elements to a stated element, step, operation and/or element. do not exclude

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in the meaning commonly understood by those of ordinary skill in the art to which the present invention pertains. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless specifically defined explicitly. In this specification, the same reference numerals may refer to the same elements throughout.

1 is a block diagram schematically showing a lidar module according to an embodiment of the present invention.

Referring to FIG. 1 , a lidar module 100 according to an embodiment of the present invention includes a transmitter 110 and a receiver 120 . The lidar module 100 according to an embodiment of the present invention may transmit the optical signal generated by the transmitter 110 to the target object 200 . The optical signal reflected by the target object 200 may be received by the receiver 120 . The lidar module 100 according to an embodiment of the present invention is a distance using a round trip time in which a pulsed laser light signal transmitted from the transmitter 110 is reflected from an object, and the reflected optical signal is detected by the receiver 120 . It may be a Time-of-Fight (ToF) lidar module that detects

The lidar module 100 according to an embodiment of the present invention applies a modulated pulsed light source to a predetermined scan area through light source modulation under the control of the transmitter 110 or according to the characteristics of the signal obtained from the receiver 120 . By modulating the light source, a pulse light source suitable for the surrounding environment may be applied to the target object 200 . The lidar module 100 according to the present invention can improve the signal detection rate without loss of power by preventing the loss or distortion of some information in the scan range due to the characteristics of the reflector. The configuration and operation principle of the lidar module 100 according to an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 4 to be described later.

2 is a block diagram schematically showing a transmitter of a lidar module according to an embodiment of the present invention.

Referring to FIG. 2 , the transmitter 110 of the lidar module 100 (refer to FIG. 1 ) according to an embodiment of the present invention includes a light source unit 111 , a pulse modulator 113 , a scanner 114 and a controller 115 . may include. The light source unit 111 may generate an optical signal for detecting the object 200 (refer to FIG. 1 ). The light source unit 111 may include a Master Oscilltor Power Amplifier (MOPA) laser or a laser diode modulated in a pulse form through the pulse modulator 113 .

The pulse modulator 113 may generate a pulse signal for modulating the optical signal generated from the light source 111 into a desired shape. The pulse modulator 113 may modulate a pulse repetition rate (PRF) or a pulse width. The pulse modulator 113 may modulate the amplitude of the optical signal by basically changing the pulse width. For example, reducing the width of the pulse can produce a high amplitude light pulse. Increasing the pulse width can generate a low amplitude light pulse. The pulse modulator 113 may generate one or more pulse signals, and accordingly, the optical signal generated by the light source 111 may be modulated in one or more forms. A modulation method of the pulse modulator 113 will be described in detail with reference to FIGS. 5A and 5B which will be described later.

The scanner 114 may irradiate the optical signal transmitted from the light source 111 to a desired point. The controller 115 may control the optical signal incident on the scanner 114 . The scanner 114 may include two mirrors. The two mirrors may be responsible for adjusting the optical path vertically and horizontally, respectively. By the scanner 114 and the controller 115, the lidar module 100 can acquire three-dimensional information through laser beam scanning and signal reception without mechanical rotation, unlike the rotating lidar in which the entire module rotates. have.

3 is a block diagram schematically showing a receiver of a lidar module according to an embodiment of the present invention.

Referring to FIG. 3 , the receiving unit 120 of the lidar module 100 (see FIG. 1 ) according to an embodiment of the present invention may include a receiving lens 121 , a photodetector 122 , and a data processing unit 123 . have. The receiving lens 121 may receive a reflected signal in which the optical signal transmitted from the transmitter 110 (refer to FIG. 1 ) is reflected by the target and returns. The receiving lens 121 may include an optical filter for receiving only a laser signal of a desired wavelength. In order to minimize the influence of sunlight or ambient light on the front surface of the receiving lens 121 , a band pass filter (BPF) is applied to the wavelength of the light transmitted from the transmitting unit 110 to approximate the wavelength of the transmitted light. It can only receive signals for wavelengths. The receiving lens 121 may condense the received reflected signal to the photodetector. The focused optical signal may be output to the optical detector 122 .

The photodetector 122 may convert the optical signal collected from the receiving lens 121 into an electrical signal. The photodetector 122 may include a low-noise trans-impedance amplifier (TIA) or a post-amplifier in order to increase a signal reception rate through signal amplification. The distance between the receiving lens 121 and the photodetector 123 may be determined by a back focusing length (BFL) of the receiving lens 121 . The electrical signal converted by the photodetector 122 may be output to the data processing unit 123 . For example, the photo detector 122 may include a PIN-Photo-Diode (PIN-PD) or an Avalanche Photo-Detector (APD).

The data processing unit 123 may process the electrical signal input from the photodetector 122 at high speed. In addition, reception information may be transmitted to the transmitter 110 in order to irradiate a modulated pulse having an appropriate shape to a desired region according to characteristics of the reflected signal. The data processing unit 123 may include a comparator and a time-to-digital converter (TDC). The data processing unit 123 may designate a signal detection level (threshold) according to the noise level, detect only a signal corresponding to the signal level higher than that, and obtain the magnitude of the received signal and the coordinate information at which the signal is obtained.

4 is a block diagram for explaining in detail the operation of the lidar module according to an embodiment of the present invention.

Referring to FIG. 4 , the lidar module 100 according to an embodiment of the present invention includes a transmitter 110 and a receiver including a light source 111 , a pulse modulator 113 , a scanner 114 , and a controller 115 . It may include a receiving unit 120 including a lens 121 , a photodetector 122 , and a data processing unit 123 .

The light source unit 111 may generate an optical signal for detecting the object 200 . The optical signal generated by the light source unit 111 may be modulated into a desired pulse shape by the pulse modulator 113 . A transmission optical system 112 may be attached to an output end of the light source unit 111 . The transmission optical system 112 may collect, bundle, or parallelize the beams to send the optical signal to the target. The optical signal modulated by the pulse modulator 113 may be input to the scanner 114 through the transmission optical system 112 .

The scanner 114 may include two mirrors. The optical signal can be routed in vertical and horizontal directions by the two mirrors. The controller 115 may perform a control operation for giving control values applied to the two mirrors included in the scanner 114 . According to a control operation of the controller 115 , the scanner 114 may radiate a transmission optical signal to a desired position with respect to the object 200 .

The reflected signal reflected by the object 200 may be input to the receiving lens 121 of the receiving unit 120 . The receiving lens 121 may filter only a signal having a wavelength corresponding to the optical signal transmitted from the transmitting unit 110 . The receiving lens 121 may condense the filtered optical signal and transmit it to the optical detector 122 .

The photodetector 122 may convert the focused optical signal into an electrical signal. The photodetector 122 may amplify the input optical signal. The photodetector 122 may input an electrical signal converted from the optical signal to the data processing unit 123 . The pulse modulator 113 included in the transmitter 100 may apply a pulse signal to the photodetector 122 . Also, the photodetector 122 may provide data on the signal reception rate to the pulse modulator 113 . The data processing unit 123 may collect data on the location, size, or surrounding environment information of the object from the electrical signal.

The data processing unit 123 may select a desired area or point within a scan range using the collected data to apply a modulation signal having a different form than that of the existing pulse. In addition, different types of pulse signals may be irradiated with respect to one or more divided scan areas. Different types of pulse signals may be modulated into appropriate pulses based on a received signal, and the modulated pulse signal may be irradiated to a corresponding point to irradiate an optimized signal to each point existing in the scan area.

For example, when the signal reception rate collected by the photodetector 122 is lower than a preset reference value, the corresponding data is provided to the pulse modulator 113 , and the pulse modulator 113 receives the signal reception rate based on the acquired data. A pulse signal modulated with a shorter period (modulated with a higher frequency) may be provided to the light source unit 111 in this low detected region. Alternatively, when the signal reception rate collected by the photodetector 122 is lower than a preset reference value, the corresponding data is provided to the pulse modulator 113, and the pulse modulator 113 determines the signal reception rate based on the acquired data. A pulse signal having an increased amplitude (reduced width) may be provided to the light source unit 111 in the low detected region.

That is, the lidar module 100 according to an embodiment of the present invention adjusts the pulse signal emitted according to the characteristics of the object 200 and the surrounding environment to irradiate the pulse signal corresponding to each area, thereby detecting the signal without additional power change. It is possible to increase the rate and improve the quality of the 3D image derived from the lidar module 100 .

5A and 5B are graphs illustrating pulse modulation patterns according to the number of internal bits.

In more detail, FIG. 5A shows a relationship between a pulse and an amplitude generated in the pulse modulator of the lidar module 100 (refer to FIG. 1) according to an embodiment of the present invention. 5B shows a relationship between a pulse and a pulse width generated by the pulse modulator of the lidar module 100 according to an embodiment of the present invention.

The pulse modulator 113 (refer to FIG. 2 ) may generate a modulated pulse signal by controlling an internal bit. Referring to FIG. 5A , the number of internal bit controls of the pulse modulator 113 and the amplitude of the pulse are inversely proportional to each other. Referring to FIG. 5B , the number of internal bit controls of the pulse modulator 113 and the width of the pulse have a proportional relationship. Accordingly, when the number of internal bit controls of the pulse modulator 113 is increased, a pulse signal having a pulse width increased but a reduced pulse amplitude can be generated. On the other hand, if the number of internal bit controls of the pulse modulator 113 is reduced, a pulse signal having a pulse width decreased but an increased pulse amplitude may be generated.

5A and 5B, the number of bit controls inside is posted as 16, but the lidar module 100 according to the present invention is not limited to the number of bit controls posted in FIGS. 5A and 5B and utilizes various control bit spaces. Therefore, it is possible to control various pulses according to the situation. For example, the internal bit control space of the lidar module 100 according to the present invention may have a size of 32 bits, 64 bits, or 128 bits in addition to 16 bits.

6A to 6C are diagrams illustrating a maximum scan range of a lidar module according to an embodiment of the present invention.

In more detail, FIG. 6A is a diagram illustrating a basic laser scan area of a lidar module according to an embodiment of the present invention. The lidar module 100 (refer to FIG. 1) according to an embodiment of the present invention utilizes a scanner 114 (refer to FIG. 2) and a controller 115 (refer to FIG. 2) to transmit a maximum scan range (Field Of View, FOV). A pulsed optical signal may be irradiated to the entire area of the corresponding area. In addition, coordinate information about the reception maximum scan range and the reflected signal may be received.

The maximum scan range is the scanner 114 and controller 115 of the transmitter 110 (refer to FIG. 1) and the receiving lens 121 (refer to FIG. 3) and the photodetector 122 (refer to FIG. 3) of the receiver 120 (refer to FIG. 1). ) can be determined by the performance of However, since the scanner 114 of the lidar module 100 according to an embodiment of the present invention has mirrors for vertical and horizontal, the scan area is not fixed. Therefore, according to the lidar module 100 according to an embodiment of the present invention, the adjustment of the scan range according to the value applied to each mirror within the maximum scan range, the configuration of one or more scan areas, and a scan for a specific point are implemented. can

In addition, according to the lidar module 100 according to the embodiment of the present invention, the data processing unit 123 included in the receiving unit 120, the information on the reflection signal with respect to the optical signal irradiated through the scanner 114 (FIG. 3) see) can be obtained. Through this, it is possible to detect the received signal size and whether the received signal is received for each coordinate point, and based on this, a 3D image can be implemented.

6B and 6C are diagrams illustrating that signals having different characteristics are applied to each scan area by a lidar module according to an embodiment of the present invention.

When an optical signal of the same size is irradiated to the entire scan area as shown in FIG. 6A, the reflected signal is weak due to various reflectance characteristics and reflection angles, and thus signals that are not visible in the 3D image may exist. In addition, a signal exceeding the dynamic range, which is the signal detection performance of the photodetector 122, is detected by the high reflectance and high sensitivity reception characteristics, so that information about a difference between the signal and the existing signal can be extracted. In this case, an error may occur in the operation of the user or the determination unit or the control unit of the autonomous driving system because it is difficult to accurately measure the surrounding environment information because it also affects the reception of the surrounding pixel signal.

Therefore, in order to overcome this error, the lidar module 100 based on the reflected signal characteristics according to the present invention uses the pulse modulation characteristics using the pulse modulator 113 (refer to FIG. 2 ) to the photodetector 122 and the data processing unit. Based on the size and coordinate information of the received signal that can be obtained through (123), information about the surrounding environment may be acquired and analyzed through separate control of a specific area.

In more detail, as shown in FIGS. 6B and 6C , it is possible to irradiate a pulse signal having a shape suitable for a partial region. A higher signal detection rate can be achieved by reducing the pulse width and irradiating a pulse with an increased amplitude to a portion where the received signal is weak and the signal detection is insufficient. In addition, a pulse having an increased pulse width and decreased amplitude may be irradiated to a portion where a signal having a magnitude greater than or equal to the saturation signal is detected. That is, the lidar module 100 according to the present invention can acquire an accurate and reliable signal through selective driving of a partial region, and can accurately implement the shape of a target object in a three-dimensional image. In addition, since it is possible to secure an improved 3D image without increasing power, it is possible to easily implement the operation of the automation system based on accurate recognition.

7 is a flowchart illustrating a method of operating a lidar module according to an embodiment of the present invention.

In step S110, the pulse modulator 113 (refer to FIG. 2) included in the transmitter 110 (refer to FIG. 1) of the lidar module 100 (refer to FIG. 1) according to the present invention is generated by the light source (111, see FIG. 2). The optical signal can be modulated into a desired shape. In modulating the pulse shape, the period or pulse width of the pulse may be adjusted. The modulated optical signal may be input to the scanner 114 (refer to FIG. 2 ) included in the transmitter 110 .

In step S120 , the scanner 114 may receive a control signal for adjusting the two mirrors included in the scanner 114 from the controller 115 . According to the control signal received from the controller 115 , the scanner 114 may adjust a path for emitting an optical signal.

In step S130 , the optical signal is uniformly emitted by the scanner 114 over the object 200 (refer to FIG. 1 ), or for each scan area based on the characteristics of the object 200 , the surrounding environment, or the received signal. Different pulse signals can be emitted.

In step S140 , the receiver 120 (refer to FIG. 1 ) included in the lidar module 100 according to the present invention may receive a reflection signal of the transmission signal reflected by the object 200 . The reflected signal may include sunlight or external noise.

In step S150 , the receiving lens 121 (refer to FIG. 3 ) included in the receiving unit 120 may focus the received reflected signal. The receiving lens 121 may extract and focus only the optical signal corresponding to the wavelength of the transmission signal from among the collected reflected signals. The focused reflected signal may be output to the photodetector 122 (refer to FIG. 3 ).

In step S160 , the photodetector 122 may amplify the focused reflected signal and convert it into an electrical signal. The electrical signal may include information about the received signal detection rate, the position of the object, and the size of the object. The converted electrical signal may be output to the data processing unit 123 . In the conversion process of the photodetector 122 , the pulse modulator 113 included in the transmitter 110 may modulate the electrical signal.

In step S170 , the data processing unit 123 may analyze information about a signal detection rate, a position of an object, and a size of an object through the input electrical signal. In addition, by providing signal detection information based on the received signal to the transmitter 110 , it is possible to control the modulation and path of the optical pulse signal to be emitted later. The data processing unit 123 may implement a three-dimensional image based on the obtained information.

The above are specific embodiments for carrying out the present invention. The present invention will include not only the above-described embodiments, but also simple design changes or easily changeable embodiments. In addition, the present invention will include techniques that can be easily modified and implemented using the embodiments. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be defined by the claims described below as well as the claims and equivalents of the present invention.

100: lidar module (Lidar Module)
110: transmitter
111: receiver
113: pulse modulation unit
114: scanner
115: controller
120: receiver
121: receiving lens
122: photo detector
123: data processing unit

Claims (1)

A pulse modulator for modulating the period or amplitude of a pulse, a light source for outputting an optical signal based on the modulated pulse, and at least one mirror to adjust the path of the optical signal and externally output the optical signal with the adjusted path a transmitter including a scanner radiating to a furnace and a controller for controlling the scanner; and
A receiving lens that receives a reflected signal generated by reflecting the optical signal by an object and condensing the reflected signal, a photodetector that converts the reflected signal into an electrical signal, and acquires information about the object based on the electrical signal And including a receiving unit comprising a data processing unit to analyze,
The photodetector obtains a signal reception rate based on the reflected signal and provides it to the pulse modulator,
The pulse modulator modulates the pulse based on the signal reception rate, but provides a pulse with a shorter period or a modulated pulse with an increased amplitude to an area where a signal reception rate lower than a preset reference value is obtained.

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