WO2022037870A1

WO2022037870A1 - Lidar sensor for optically capturing a field of view, and method for capturing a field of view

Info

Publication number: WO2022037870A1
Application number: PCT/EP2021/070142
Authority: WO
Inventors: Alexander Greiner; Reiner Schnitzer
Original assignee: Robert Bosch Gmbh
Priority date: 2020-08-20
Filing date: 2021-07-19
Publication date: 2022-02-24
Also published as: DE102020210582A1

Abstract

A LIDAR sensor (100) for optically capturing a field of view (108) comprises a transmitter unit (101) with at least one emitter unit (102) which is designed to emit primary light (104) into the field of view (108); a receiver unit (112) with at least one detector unit (117) which is designed to detect secondary light (111) which was reflected and/or scattered in the field of view (108) by an object (109); and a deflection unit (106) which is designed to deflect emitted primary light (104) into the field of view (108) at a predeterminable angle and to deflect received secondary light (111) in the direction of the at least one detector unit (117). The detector unit (117) comprises a matrix of a multiplicity of light-sensitive pixels, wherein at least one transmission reduction element (202, 203) which is designed to reduce transmission of secondary light (111) to the pixels is arranged in at least one edge region (204-1 to 204-4) of the matrix.

Description

description

title

LIDAR sensor for optically capturing a field of view and method for capturing a field of view

The present invention relates to a LIDAR sensor for detecting a field of view and a method for detecting a field of view.

State of the art

In addition to video, ultrasound and radar-based systems, LIDAR systems are considered a key technology for highly automated driving. LIDAR systems typically use the Time-Of-Flight (ToF) method as the measuring principle. A laser pulse is emitted by a transmitter, reflected on an object and the time until detection is measured on a sensor unit. APDs (avalanche photodetectors) and SPADs (single-photon avalanche detectors), for example, but also CCDs (charged-coupled devices) can be used as detectors of a LIDAR sensor. However, SPAD and CCD-based systems in particular are prone to saturation of the individual pixels, so that no statement can be made about the intensity of a close and highly reflective object.

Disclosure of Invention

The present invention is based on a LIDAR sensor for optically detecting a field of view, having a transmission unit with at least one emitter unit, which is designed to emit primary light into the field of view; a receiving unit with at least one detector unit, which is designed to detect and/or detect objects reflected in the field of view to detect scattered secondary light; and a deflection unit, which is designed to deflect emitted primary light at a predeterminable angle into the field of view and to deflect received secondary light in the direction of the at least one detector unit.

According to the invention, the detector unit has a matrix of a large number of light-sensitive pixels, with at least one transmission reduction element being arranged in at least one edge region of the matrix, which element is designed to reduce transmission of the secondary light onto the pixels. In other words, the detector unit has an area with a first photon detection efficiency and at least one edge area with a second photon detection efficiency, which is lower than the first photon detection efficiency.

Using a LIDAR sensor, a distance between the LIDAR sensor and an object in the field of view of the LIDAR sensor can be determined directly or indirectly on the basis of a signal propagation time (time of flight, TOF). The field of view of the LIDAR sensor can be scanned using the emitted primary light. The emitter unit can be designed as at least one laser. The deflection unit can be designed as a mirror, in particular a micromirror. The deflection unit can also be designed as a rotatable unit on which the transmitting unit and/or the receiving unit are at least partially arranged. The LIDAR sensor optionally has at least one evaluation unit. The detected secondary light can be evaluated by means of the evaluation unit. The result of the evaluation can be used for a driver assistance function of a vehicle, for example. The result of the evaluation can be used, for example, to control an autonomously driving vehicle. The LIDAR sensor can be designed in particular for use in an at least partially autonomously driving vehicle. With the LIDAR sensor, semi-autonomous or autonomous driving of vehicles can be realized on freeways and in city traffic.

The advantage of the invention is that the intensity of the secondary light reflected and/or scattered by objects can be reduced. In particular, the intensity of the reflected light from nearby objects can be measured and/or scattered secondary light can be reduced. As a result, improved measurability can be achieved using the LIDAR sensor. The measuring range can be expanded into the near range in a simple and cost-effective manner. In particular in the event that the detector unit is in the form of a SPAD, the close-up range can now be expanded without impairing the long-distance range. Saturation of the detector unit in the close-up range can be avoided and the intensity of the secondary light received can thus be better determined.

Due to the second, lower photon detection efficiency in the edge area, the LIDAR sensor has no limitations in the long range. Firstly, a receiving optics forms the secondary light from the close-up range in a larger spot (blurred area). Secondly, a beam of the secondary light can be moved from the at least one edge region into the region with the first photon detection efficiency in the case of rotating or oscillating beam deflection. Depending on the direction of rotation/oscillation, this happens from left to right or vice versa, depending on the speed of rotation/oscillation more or less. At close range, the secondary pulse has a high intensity. The edge area with the low photon detection efficiency is thus advantageously used for the close-up area in order not to saturate the detector unit. The area with the first photon detection efficiency is used to image the far area.

In an advantageous embodiment of the invention, it is provided that the transmission reduction element is designed as a mask, a partial mask, an attenuation filter arranged on the pixels and/or as a screen. The screen can be designed in particular as a slit screen. For example, the mask can be designed in such a way that only a fraction of the secondary light is transmitted to the pixels. The secondary light is typically attenuated to a fraction of 1/50 to 1/100. The masking can be in the form of a perforated grid or a partial cover. The partial masking can be in the form of a perforated grid or a partial covering. The advantage of this configuration is that the intensity of the secondary light reflected and/or scattered by objects can be reduced in a very cost-effective manner. In a further advantageous embodiment of the invention it is provided that a second transmission reduction element is arranged in a second edge area which is arranged on a side of the matrix opposite the first edge area of the matrix. In other words, the detector unit has an area of the matrix with a first photon detection efficiency, a first edge area of the matrix with a second photon detection efficiency, which is lower than the first photon detection efficiency, and on the opposite side of the matrix a second edge area of the matrix with a third photon detection efficiency, which is less than the first photon detection efficiency. The area of the matrix with the first photon detection efficiency is thus arranged in particular between the first and the second edge area of the matrix. The second photon detection efficiency can be the same as or different from the third photon detection efficiency. The advantage of this configuration is that, regardless of a direction of rotation or movement of the deflection unit, the received secondary light can be moved from the edge area with the second photon detection efficiency into the area with a first photon detection efficiency. The direction of rotation or movement can be switched or selected independently of the installation position of the detector unit.

In a further advantageous embodiment of the invention, it is provided that the detector unit is designed as an S PAD detector, CCD detector or as a CMOS (complementary metal oxide semiconductor) detector. The advantage of this configuration is that such detector units can be produced particularly inexpensively. In particular, S PAD detectors can significantly amplify a single photon to provide a detection signal. A few photons are sufficient to generate a signal. Because the LIDAR sensor has the transmission reduction element(s), intensity information and more precise distance data in the close range can also be recorded with SPAD systems. The invention is also based on a method for optically detecting a field of view using a LIDAR sensor. The method has the following steps: Emission of primary light by means of a transmission unit of the LIDAR sensor with at least one emitter unit; Deflecting emitted primary light at a predeterminable angle into the field of view using a deflection unit of the LIDAR sensor; receiving secondary light reflected and/or scattered by an object in the field of view by means of a receiving unit of the LIDAR sensor; deflecting the received secondary light in the direction of at least one detector unit of the receiving unit; and detecting the secondary light by the detector unit. In this case, the detector unit has a matrix of a large number of light-sensitive pixels, with at least one transmission reduction element being arranged in at least one edge region of the matrix. The method further includes the step of reducing a transmittance of the secondary light onto the pixels using the transmittance reducing element.

The invention is also based on a computer program which is set up to carry out the method described above.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

drawings

Exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. The same reference symbols in the figures denote the same or equivalent elements. Show it:

FIG. 1 exemplary embodiment of a LIDAR sensor for detecting the field of view;

FIG. 2 exemplary embodiment of a detector unit; FIG. 3 exemplary embodiment of a method for detecting the field of view using a LIDAR sensor.

Figure 1 shows an example of an embodiment of the LIDAR sensor 100 according to the invention in the form of a schematic block diagram. The LIDAR sensor 100 according to Figure 1 has a transmission unit 101 which is fed by an emitter unit 102, e.g and primary light 104 is generated and emits/emits this—possibly after passing through beam-shaping optics 105—into a field of view 108 for optically capturing a field of view 108, i.e. for capturing and/or examining a scene 110 and an object 109 located there.

Furthermore, the LiDAR sensor 100 according to Figure 1 has a receiving unit 112, which receives light and in particular light reflected and/or scattered by object 109 in field of view 108 as secondary light 111, for example via a lens 107 as primary optics, and via detector optics 116 as secondary optics to a detector unit 117. The detector unit 117 can be designed in particular as an S PAD detector, CCD detector or as a CMOS detector.

The receiving unit 112 and the transmitting unit 101 are designed with essentially coaxial optical axes on the field of view side and have a common deflection optics 106 in the exemplary embodiment shown. The common deflection optics 106 on the field of view side can be understood as part of the optics of the transmission unit 101 and as part of the optics of the reception unit 112 . The deflection optics 106 can have, for example, a corresponding deflection unit 115, which is shown purely schematically in FIG. In other words, the receiving unit 112 can have secondary optics 116 on the detector side, which are designed and include means for inherently directing secondary light 111 incident from the field of view 108 onto the detector unit 117 via the deflecting optics 106 . Optional and advantageous is the provision of aperture optics 107 on the field of view for the suitable output of the primary light 104 and for the bundling of the reception of the secondary light 111. Alternatively, the transmission unit 101 and the reception unit 112 of the LIDAR sensor 100 can also be arranged biaxially or essentially coaxially along the optical paths of the transmission unit 101 and the reception unit 112 . In the case of the coaxial arrangement, elements of the beam-shaping optics 105 can also be designed as elements of the detector optics 116, and vice versa.

Alternatively, the deflection unit 106 can also be designed in such a way that the transmission unit 101 has a first deflection device for deflecting primary light 104 into the field of view 106 . The primary light 104 can be deflected into the field of view 106 by the first deflection device of the transmission unit 101 at predetermined deflection angles. In this case, the deflection unit 106 is also designed such that the receiving unit 112 has a second deflection device for deflecting secondary light 111 onto the detector unit 117 . Secondary light 111 incident at different angles can be deflected onto the detector unit 117 by a deflection device of the receiving unit 112 .

Alternatively, the deflection unit 106 can also be designed in such a way that the transmission unit 101 and the reception unit 112 are arranged on a rotatable unit. Individual elements of the transmitting unit 101 and/or individual elements of the receiving unit 112 can be arranged on a rotatable unit.

The emitter unit 102 and the detector unit 117 can be controlled via control lines 121 or 120 by means of a control and evaluation unit 119 .

FIG. 2 shows an exemplary embodiment of a detector unit 117 of a LIDAR sensor shown in FIG. 1, for example. The detector unit 117 has a matrix of a large number of light-sensitive pixels, which are not shown separately here. A transmission reduction element 202 is arranged in a first edge region 204-3 of the matrix, which element is designed to reduce transmission of the secondary light onto the pixels. In the exemplary embodiment shown, the one on the first edge area 204-3 of the matrix is also in a second edge area 204-4 is arranged on the opposite side of the matrix, a second transmission reduction element 202 is arranged. The detector unit 117 thus has an area 201 of the matrix with a first photon detection efficiency, a first edge area 204-3 of the matrix with a second photon detection efficiency, which is lower than the first photon detection efficiency, and on the opposite side of the matrix a second edge area 204-4 of the Matrix with a third photon detection efficiency, which is less than the first photon detection efficiency on. As shown in FIG. 2, further transmission reduction elements 203 can also be arranged in further edge regions 204-1, 204-2 of the matrix. The transmission reduction elements 202, 203 can be designed, for example, as a mask and/or as a diaphragm.

FIG. 3 shows an exemplary embodiment of a method 300 for detecting the field of view using a LIDAR sensor. The method starts in step 301. In step 302, primary light is emitted by means of a transmission unit of the LIDAR sensor with at least one emitter unit. In step 303, emitted primary light is deflected at a predeterminable angle into the field of view by means of a deflection unit of the LIDAR sensor. In step 304, secondary light reflected and/or scattered by an object in the field of view is received by a receiving unit of the LIDAR sensor. In step 305, the received secondary light is deflected in the direction of at least one detector unit of the receiving unit. As described in FIG. 2, the detector unit has a matrix of a large number of light-sensitive pixels, with at least one transmission reduction element being arranged in at least one edge area of the matrix. In step 306 a transmission of the secondary light onto the pixels is reduced by means of the transmission reduction element. Finally, in step 307, the secondary light is detected by the detector unit. The method ends in step 308.

Claims

- 9 - Claims

Having a LIDAR sensor (100) for optically detecting a field of view (108).

• a transmission unit (101) with at least one emitter unit (102) which is designed to emit primary light (104) into the field of view (108);

• a receiving unit (112) with at least one detector unit (117) which is designed to detect secondary light (111) reflected and/or scattered by an object (109) in the field of view (108); and

• a deflection unit (106) which is designed to deflect emitted primary light (104) at a predeterminable angle into the field of view (108) and to deflect received secondary light (111) in the direction of the at least one detector unit (117); characterized in that

• the detector unit (117) has a matrix of a large number of light-sensitive pixels, with at least one transmission reduction element (202, 203) being arranged in at least one edge area (204-1 to 204-4) of the matrix, which element is designed for transmission of the secondary light (111) to the pixels.

2. LIDAR sensor (100) according to claim 1, wherein the transmission reduction element (202, 203) is designed as a mask, a partial mask, an attenuation filter arranged on the pixels and/or an aperture.

3. LIDAR sensor (100) according to claim 1 or 2, wherein in a second edge region (204-2, 204-4) on a first edge region (204-1, 204-4) of the matrix opposite side of the matrix arranged a second transmission reduction element (202, 203) is arranged.

4. LIDAR sensor (100) according to any one of the preceding claims, wherein the detector unit (117) is designed as an S PAD detector, CCD or CMOS detector.

5. Method (300) for optically detecting a field of view using a LIDAR sensor, comprising the steps:

• Emission (302) of primary light by means of a transmission unit with at least one emitter unit;

• deflection (303) of emitted primary light at a predeterminable angle in the field of view by means of a deflection unit;

• receiving (304) secondary light reflected and/or scattered by an object in the field of view by means of a receiving unit;

• deflecting (305) the received secondary light in the direction of at least one detector unit of the receiving unit;

• detecting (307) the secondary light by means of the detector unit; characterized in that

• the detector unit is a matrix of a variety of photosensitive

having pixels, at least one transmission reduction element being arranged in at least one edge region of the matrix; and wherein the method (300) further comprises the step of:

• reducing (306) a transmission of the secondary light onto the pixels by means of the transmission reduction element.

6. A computer program which is set up to carry out the steps of the method (300) according to claim 5.