WO2018178159A1 - Lidar system - Google Patents

Abstract

The present invention relates to a lidar system (1) comprising a first light source (2) for emitting first light (4), which is amplitude-modulated with a first frequency, a second light source (3) for emitting second light (5), which is amplitude-modulated with a second frequency different from the first frequency, and a receiving device (6) for detecting a reflection (7), on which the first light (4) and the second light (5) are superimposed.

Description

 Description title

 Lidarsystem prior art

The present invention relates to a lidar system. In addition, the concerns

Invention A vehicle comprising such a lidar system. Finally, the invention relates to a method for determining a distance to an object.

Lidar systems are known from the prior art, which are used in vehicles. Such Lidarsysteme serve to determine a distance of an object, in particular by triangulation and / or by

Determination of the light runtime Measurements are possible that allow a localization of the object in the space in front of the vehicle. For example, a lidar system is known from DE 100 37 771 A1. Basically, known lidar systems have problems in bad weather. Especially with fog measuring distances is not possible or at least severely limited. The above problems in bad weather can not be solved easily. Thus, for an improved view, the light output of the lidar system would have to be increased. However, this would lead to increased risk to the human eye from the lidar system. This in turn brings with it regulatory issues.

Disclosure of the invention

The Lidarsystem invention allows improved measurement by means of light, in particular laser light, even in bad weather, at the same time an eye hazard is precluded by the light. This is achieved in that a receiving device is provided which only recognizes reflections that form from a superposition of light from two light sources with different amplitude modulation frequencies. Such reflections can be detected easily and with little effort, while at the same time enabling a determination of a distance between the object and the lidar system. The lidar system according to the invention comprises a first light source and a second light source as well as a receiving device. The first light source and / or the second light source is in particular a

Light source of high beam density. The first light source is configured to emit first light that is amplitude modulated at a first frequency. The second light source is designed to emit second light which has a second frequency which differs from the first frequency

is amplitude modulated. The receiving device serves to detect a reflection, at which the first light and the second light are superimposed. Thus, the receiving device only has to search for reflections with such a superposition. This simplifies the detection of reflections, so that a secure and reliable detection is available. This is especially the case when visibility is limited due to inclement weather, such as fog. Also in this case, the receiving device can surely and reliably detect said reflection. In the

Receiving device is particularly advantageous to a camera for optical detection of the reflection. As soon as the reflection has been detected, a distance between a object generating the reflection and the lidar system can take place by means of known methods. The dependent claims have preferred developments of the invention for

Content.

It is preferably provided that the second frequency is at most 200%, preferably at most 150%, and more than 100% of the first frequency. This creates a beating in the reflection that comes from the

 Receiving device can be detected easily and with little effort. The beat has a low frequency, which is calculated from the first frequency and the second frequency. Because the distance between the two

Frequencies due to the described sizes of the second frequency and the first frequency is low, the beating can be detected easily and with little effort. The receiving device particularly advantageously has a filter which does not suppress only such reflections and thus is permeable only to those frequencies which have a beat frequency which is calculated from the difference between the first frequency and the second frequency. This means that only said beat frequency passes the filter, while all other frequencies, in particular to quasi-static components of the amplitude, are suppressed. Thus, the Lidarsystem is easy and low effort even operable when poor visibility

prevail and / or strong external lighting is present. In particular, the receiving device only has to detect said reflection, which is made possible simply and with little effort on the basis of the beat frequency. The receiving device is advantageously an optical sensor which, in the preferred embodiment, thus only sees the reflection, but not all other lights emitted by the lidar system. Thus, a secure and reliable detection is possible. Based on

 Triangulation can then be calculated the distance to the reflection. This allows to perform a safe and reliable distance measuring method. If the receiving device is a camera, then the camera may preferably have further filters, in particular further electronic filters, in order to be able to supply further images in addition to the previously described image, which merely shows the reflection.

The first light and / or the second light are preferably emitted from the first light source and / or the second light source in a cell-shaped and / or column-shaped manner. In particular, the first light source and the second light source thus preferably serve to emit line-shaped light which, when hitting an object, leads to a linear reflection. If the cell-shaped light of one illumination and the column-shaped light of the other illumination are superimposed, a superposition line is created in the space. If this overlapping line meets an object, in particular said reflection arises. In addition, a synchronization between the cell-shaped light and the column-shaped light is particularly advantageous in such a way that the first light source and the second light source are synchronized. Thus, it is known how the cellular light and the columnar light are locally emitted relative to one another. Because of this information is a

Triangulation can be calculated easily and with little effort. This allows a simple and low-cost calculation of the distance of the reflection to the lidar system.

The lidar system is advantageously designed such that the first

Light source and / or the second light source for line by line and / or column-wise scanning of an environment having a first sampling frequency and a second sampling frequency is formed. Column scanning is also called horizontal scanning and line scanning is also called vertical scanning. The first sampling frequency is advantageously used for vertical sampling while the second sampling frequency is used for horizontal sampling. The first sampling frequency is advantageously between 80 Hz and 120 Hz, in particular between 90 Hz and 110 Hz, particularly preferably of 100 Hz. The second sampling frequency is preferably between 1 kHz and 40 kHz, in particular between 10 kHz and 30 kHz, particularly preferably 20 kHz. Again, it is particularly advantageous that a synchronization between the line-wise scanning and the column-wise scanning takes place. Thus, it is ensured that the first light source and the second light source emit light in the same environment, so that said reflection can occur by superposition of the first light and the second light. In particular, it is also provided that a line-by-line scanning is performed by means of a cell-shaped light, wherein the cellular light has such an extent, which by the

column-wise scanning is covered. The same applies to column-by-column scanning and a columnar light which is preferably used for this purpose. Thus, it is ensured that a reflection by superposition of the first light and the second light can always occur because there is always an overlap between columnar light and cell-shaped light. In addition, synchronization preferably takes place in such a way that the receiving device is always aware of the position in which the line-by-line and / or column-by-column scanning light is located during the emission of the light.

The receiving device is advantageously a camera. In particular, it is provided that the receiving device has a

Image refresh rate between 80 fps and 120 fps, in particular between 90 fps and 1 10 fps, more preferably of 100 fps. Under fps is the

To understand the term "frames per second", which means that such a number of frames per second are resolved by the receiving device can be. In this way, the reflection, in particular by said beat, easy and low effort to recognize.

The invention also relates to a vehicle comprising such a lidar system. Thus, the vehicle is designed to be a distance to objects in the

Environment safely and reliably detected. In particular, it is possible to carry out such a detection even when poor visibility prevails, in particular due to fog. At the same time there is an eye safety of the light, since the beneficial linear / fan-shaped expansion light is absorbed by the eye only a fraction, i.e., light with higher light output can be used. This avoids regulatory issues when using the

Lidarsystems in vehicles. Finally, the invention relates to a method for performing a

 Distance measurement. The method comprises the following steps: First, there is a transmission of a first light, in particular laser light, which is amplitude-modulated with a first frequency and emitting a second light, in particular laser light, which is amplitude-modulated with a second frequency. The second frequency is different from the first frequency. The first light and / or the second light are preferably emitted fan-shaped, with the fan shapes particularly preferably intersecting along a line. Subsequently, a detection of an impinging of the overlay line on an object resulting reflection, in which the first light and the second light are superimposed. The distance measurement is preferably carried out by triangulation from the light paths of the superposition of the first light and the second light (superposition line) and the light path of the reflected light. The distance measurement is carried out particularly advantageously by means of triangulation with the image of a camera. In the camera image, an object that generates the reflection is modulated with a spot illuminated. This is particularly the case when the above-described line, at which the fan shapes of the first light and the second light intersect, hits the object. Using a pixel position in the image of the camera and the position of the line in space then the distance measurement can be easily performed. The reflected light is the light that moves from reflection to light

Receiving device runs. The light path of the first light and the second light are those light paths that go from the corresponding light source to the light source Lead reflection. The calculation of the distance takes place, in particular, to a reference point, which is defined by a lidar system, each comprising a light source for emitting the first light and the second light as well as said receiving device. The method allows a safe and reliable distance measuring even if due to bad

Visual conditions, such as fog in particular, optical measuring methods such as Lidar are not or only partially operational. Thus, the method allows in particular a safe and reliable measurement of a distance in vehicles, since there is no influence on environmental conditions.

To carry out the method, the second frequency is preferably at most 200%, in particular at most 150%, and more than 100% of the first frequency. In this way results in superposition of first light and second light a beating. Said beating is simple and

to detect little effort, which can be achieved safely and reliably that said beat can be detected by a receiving device. This is also the case when the view is due to

Environmental conditions, in particular due to fog, is limited.

Finally, it is preferably provided that only those reflections are detected which have a beat frequency. The beat frequency is calculated from the difference between the first frequency and the second

Frequency. In this way it is achieved that a receiving device sees only the reflection. This ensures that a safe and reliable detection of the reflection takes place. At the same time, due to triangulation and / or transit time measurement, a distance to the reflection can be reliably and reliably calculated. Thus, a safe and reliable measurement of a distance is possible.

On the overlay line described above, along which the

Cut fan shapes of the first light and the second light, beats are preferred. If the two light fans scan, meaning the first light and the second light, then the line along which the fan shapes intersect is also shifted in space. If the line meets an object in the

Space, this is illuminated with the beat frequency. Brief description of the drawings

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawings:

Figure 1 is a schematic view of a lidar system according to a

 Embodiment of the invention, and

Figure 2 is a schematic view of a vehicle according to a

 Embodiment of the invention.

Embodiments of the invention

Figure 1 shows schematically a lidar system 1 according to an embodiment of the invention. The lidar system 1 comprises a first light source 2, in particular a laser light source, a second light source 3, in particular a

Laser light source, and a receiving device 6. The first light source 2 is used to emit first light 4, which at a first frequency

is amplitude modulated. The second light source 2 is used for emitting second light 5, which is amplitude-modulated with a second frequency. The first frequency and the second frequency differ. Particularly preferably, the first frequency is 100 MHz, while the second frequency is 101 MHz.

The first light source 2 is designed to carry out a vertical scanning of an environment 8 (cf. FIG. 2) of the lidar system 1. The vertical scanning is also called line by line scanning, which means that a line-shaped first light 4 is used, which is moved vertically or line by line through the environment 8.

By the second light source 3 is a horizontal scanning of the environment 8. This is also called column-by-column scanning. For this purpose, the second light 5 is formed in a column shape and moves horizontally. In this way a complete scanning of the environment 8 is made possible.

It is preferably provided that there is always an overlap between the first light 4 and the second light 5. Such an overlay comes from that the scanning in the horizontal or column-wise direction such

Dimension corresponds to the size of the line shape of the first light 4. Likewise, there is a line-by-line or vertical scanning in such a scanning path that corresponds to the dimension of the cellular second light 5. In this way, there is always a line of intersection between the first light 4 and the second light 5. This leads to the fact that always a reflection can be generated, which is composed of a superposition of the first light 4 and second light 5. Meets the line of intersection between the first light 4 and the second light 5 on an object

Reflection 7 is a superposition of the first light 4 and the second light 5. Due to the slightly different first frequency and second frequency, the reflection is a beating. This means that the line where the first light 4 and the second light 5 overlap, the

 Beating so that the object 1 1 is illuminated when hitting the line with the beat. The beat has a beat frequency of 1 MHz, which is the difference between the first frequency and the second

Frequency corresponds. Said beat is detected by the receiving device 6 through a corresponding filter easy and little effort.

For this purpose, the receiving device 6 is advantageously designed as a camera having a frame rate of 100 fps. Furthermore, the camera preferably has an electronic filter which is synchronized to the beat frequency. Such electrical filters are known, for example, as lock-in amplifiers.

In bad weather conditions, especially in fog, the entire line can be visible, the reflection 7 is still recognizable as such due to greater brightness. Thus, it is always ensured that the reflection 7 is reliably and reliably detected, whereby a reliable

 Distance measurement is possible.

The first light source 2 and the second light source 3 are connected to the

Receiving device 6 preferably synchronized. Thus, a first

Synchronization line 100 is present, which is a vertical or line by line

Synchronization enabled. In addition, a second synchronization line 200 is present, which is a horizontal or column-by-column synchronization on the one hand between the first light source 2 and second light source 3 and between the second light source 3 and receiving device 6 allows. In this way it is ensured that both the light sources 2, 3 and the

Receiving device 6 illuminate the same area of the environment 8 and capture. Thus, by simple triangulation a safe and reliable

Distance between the object 11, which has generated the reflection 7, and the lidar system 1 are determined.

The first light source 2 and the second light source 3 in particular comprise light-emitting diodes 9. The light-emitting diode 9 of the first light source 2 is designed to emit first light 4 with said first frequency. The light-emitting diode 9 of the second light source 3 is designed to emit the second light 5 with said second frequency. It is provided that the first frequency and the second frequency at which the light-emitting diodes 9 emit light are synchronized with the receiving device 6 via a third synchronization line 300. In this way, the above-described filter can be surely and reliably adjusted to the beat calculated from the difference between the first frequency and the second frequency. This ensures that the receiving device 6, at least in one

Operating mode, only the reflection 7 sees.

Particularly advantageously, the receiving device 6 provides a plurality of different images that can be generated due to different electronic filters. Thus, the receiving device 6

In particular, a high-resolution camera image and at the same time a low-resolution image that sees only the reflection provide. In this way, a comprehensive scanning and / or detection of the environment 8 is made possible.

Figure 2 shows schematically a vehicle 10 according to an embodiment of the invention. The vehicle 10 has the lidar system 1 according to FIG. 1.

Thus, the vehicle 10 is configured to scan the surroundings 8 around the vehicle 10 and to detect objects 11. Triangulation also makes it possible to calculate a distance to the object 11 and a position of the object 11 relative to the vehicle 10. Due to the fact that the reflection 7 represents a superimposition of the first light 4 and the second light 5, this is easily and effortlessly recognizable due to a beating resulting from the superposition. Thus, in general, objects 11 can be detected along a measurement line, the measurement line being determined from the section between the light fan of the first light source 2 and the light fan of the second light source 3. As soon as an object 11 is present within this measuring line, a reflection 7 results as described above. In fog or other environmental conditions that provide a reduced view, the reflection 7 is not sharply delimited and has a lower intensity, but is detected by the receiving device 6 safely and reliably.

The lidar system 1 has the following advantages:

 • 3D measurement in the fog (the lidar system 1 also sees in fog)

• The range is limited by the signal-to-noise ratio of the beat detection, which maximizes the range even in low visibility

 • enables detection of non-metallic surfaces (as opposed to radar-based systems)

 The 3D image requiring only detection of the reflection and a high-resolution camera image are 100% coincident due to the use of the same receiving device 6

 • Eye safety is present despite high light flux

 • due to favorable light sources 2, 3, for the Lidarsystem 1

 can be used, the Lidarsystem 1 is inexpensive to manufacture

 • thermal stability of the lidar system 1 is given

 • Several light source suppliers are possible, so that production of the lidar system 1 is optimized.

Claims

claims 1. Lidar system (1) comprising  A first light source (2) for emitting first light (4) amplitude-modulated at a first frequency,  A second light source (3) for emitting second light (5) which is amplitude modulated with a second frequency different from the first frequency, and  • A receiving device (6) for detecting a reflection (7) on which the first light (4) and the second light (5) overlap. 2. Lidarsystem (1) according to claim 1, characterized in that the second frequency is at most 200%, preferably at most 150%, and more than 100% of the first frequency. 3. Lidarsystem (1) according to any one of the preceding claims, characterized  in that the receiving device (6) has a filter which is permeable only to those reflections (7) which have a beat frequency which is calculated from the difference between the first frequency and the second frequency. 4. Lidarsystem (1) according to any one of the preceding claims, characterized in that the first light (4) and / or the second light (5) in the form of cells and / or columns by the first light source (2) and / or second light source (3 ) is send out. 5. Lidarsystem (1) according to claim 4, characterized in that the first light source (2) and / or the second light source (3) for line by line and / or column-wise scanning of an environment (8) with a first sampling frequency between 80 Hz and 120 Hz, in particular between 90 Hz and 110 Hz, preferably of 100 Hz, and / or with a second one Sampling frequency between 1 kHz and 40 kHz, in particular between 10 kHz and 30 kHz, preferably of 20 kHz is formed. Lidar system (1) according to one of the preceding claims, characterized in that the receiving device (6) has a  Image refresh rate between 80 fps and 120 fps, in particular between 90 fps and 110 fps, preferably of 100 fps. Vehicle (10) comprising a lidar system (1) according to one of  previous claims. Method for performing a distance measurement, comprising the steps: • emitting first light (4) at a first frequency  is amplitude modulated,  Emitting second light (5) which is amplitude modulated at a second frequency different from the first frequency,  • detecting a reflection (7), at which the first light (4) and the second light (5) overlap, and  Determining a distance to the reflection (7) by triangulation from the light paths of the first light (4), the second light (5) and the reflected light (12) or by a transit time between the  Emitting the first light (4) and / or the second light (5) and the detection of the reflection. A method according to claim 8, characterized in that the second frequency is at most 200%, preferably at most 150%, and more than 100% of the first frequency. 0. The method of claim 8 or 9, characterized in that only  such reflections are detected which have a beat frequency which is calculated from the difference between the first frequency and the second frequency.