DE102013215627A1 - Light detection device and control method - Google Patents

Abstract

The invention provides a light detection device, a lidar device and control methods for controlling a light detection device and a lidar device. The light detection device comprises: a light focusing device (16) for coupling light beams (32) into the light detection device; a micromechanical diffraction grating (18), wherein the light focusing device (16) and the micromechanical diffraction grating (18) are designed and arranged with respect to one another such that light beams (34, 44) coupled in by means of the light focusing device (16) are at least partially directed towards the diffraction grating (FIG. 18) are focusable, wherein the diffraction grating (18) is further formed such that on the diffraction grating (18) incident light beams (34, 44) in response to adjustable diffraction properties of the diffraction grating (18) at least partially towards a light sensor (20) are diffractable, which is designed for measuring incident on the light sensor (20) light rays (36); and control means (22) adapted to adjust the diffraction characteristics of the diffraction grating (18).

Description

The present invention relates to a light detecting device, and more particularly to a lidar device having a light detecting device and control methods for a light detecting device and a lidar device.

State of the art

In the EP 0 448 111 A2 For example, a lidar scanning system is described which includes a rotating polygon mirror which transmits modulated light from one of its facets to a surface. The light diffusely reflected back from the surface is reflected by another facet of the polygon mirror onto a photodetector. The use of different optical paths for the transmitted and reflected light improves the signal-to-noise ratio.

Disclosure of the invention

The present invention discloses a light detection device having the features of claim 1, a lidar device having the features of claim 4 and a control method having the features of claim 10.

Accordingly, there is provided: a light detecting device having a light focusing device for injecting light beams into the light detecting device; a micromechanical diffraction grating, wherein the Lichtfokussiereinrichtung and the micromechanical diffraction grating are formed and arranged with respect to each other so that by means of the Lichtfokussiereinrichtung coupled light beams are at least partially focused on the diffraction grating, wherein the diffraction grating is further designed such that incident on the diffraction grating light beams in Depending on adjustable diffraction characteristics of the diffraction grating, at least in part diffractable towards a light sensor, which is designed to measure light rays incident on the light sensor; and a control device configured to adjust the diffraction characteristics of the diffraction grating.

Furthermore, a lidar device with the light-detecting device according to the invention is provided; and a scanning device configured to scan a scanning area by means of light beams; wherein the Lichtfokussiereinrichtung is formed such that from the scanning area on the lidar device incident light beams, are focused on the diffraction grating.

Furthermore, a control method is provided with the method steps: coupling of light beams into the light-detecting device by means of a light-focusing device; Focusing coupled light beams onto a micromechanical diffraction grating by means of the light focusing device; Diffracting light rays incident on the diffraction grating in response to adjustable diffraction characteristics of the diffraction grating; and adjusting the diffraction characteristics of the diffraction grating.

Advantages of the invention

The finding underlying the present invention is that adjustable micromechanical diffraction gratings with controllable diffraction properties can advantageously be used in light-detecting devices in order to reduce the influence of stray light on the light detection of useful light. Useful light is such light which has desirable properties, strikes the light detection device from a desired solid angle region, and / or originates from a desired source. Steady light may be, for example, such light which originates from undesired sources, such as from the sun, or which strikes the light-detecting device from an undesired solid angle range.

The micromechanical diffraction grating may be, for example, a "Grating Light Valve ^™ " (GLV). Such a diffraction grating can assume two different states. In a first, the so-called specular state, incident light is reflected as if from a mirror. In a second state, the diffraction state, the light is diffracted, substantially in the direction of that of first order diffraction maxima. In addition, such a diffraction grating, for example, a GLV, have a fast switching time, so that it may be possible to adaptively switch the GLV so that only light from a currently scanned solid angle or solid angle range is directed onto the light sensor.

The idea on which the present invention is based now consists in taking this finding into account and using a micromechanical diffraction grating with controllable diffraction properties in a light-detecting device, in particular in a lidar device with a corresponding light-detecting device.

Among other things, the diffraction grating can take on the task of an adaptive, direction-selective diaphragm, which transmits only light from a certain direction and directs it to the light sensor. Interference and ambient light from the rest Spatial directions, on the other hand, can be strongly damped. Compared to other solutions, therefore, there is considerable cost savings potential. In particular, when used in the return path of a light beam, which is used in a lidar device for scanning a scanning, arise in combination with the light source of the lidar device, which generates light or laser beams with known properties, advantageous synergy effects.

The guiding effect of the diffraction grating may be that a diffraction pattern of the incident light is produced when the light strikes the diffraction grating. The diffraction pattern has diffraction minima and diffraction maxima, wherein the intensity of the diffraction maxima usually decreases with increasing order of the diffraction maxima. The diffraction grating can be controlled such that the diffraction pattern is adapted such that a diffraction maximum of useful light impinges on the light sensor and / or a diffraction minimum of stray light impinges on the light absorber. The diffraction maxima of the light can thus be "diffracted towards the light sensor".

Advantageous embodiments and further developments emerge from the dependent claims and from the description with reference to the figures.

According to a preferred development of the light detection device, the diffraction grating has reflective strips arranged in parallel. The diffraction properties of the diffraction grating are adjustable at least by temporarily temporarily lowering a first plurality of the reflective strips compared to a second plurality of the reflective strips in a direction perpendicular to the direction in which the strips are arranged parallel to one another. For example, every second, every third, etc. strip can be lowered in each case. Such properties, for example, the "Grating Light Valve ^TM " (GLV). In particular, a dependence of the diffraction characteristics of the diffraction grating on the light beams incident on the diffraction grating can be adjusted via, for example, a depth of lowering of the first plurality of reflective strips. The first plurality of reflective strips may advantageously be lowered by a fraction of a wavelength, as compared to the second plurality of reflective strips, for example, to be diffracted.

According to a further preferred development of the light-detecting device, the diffraction grating has a matrix with a plurality of separately controllable sections, wherein the diffraction properties of each of the separately controllable sections can be adjusted separately. Thus, light beams incident on different portions of the diffraction grating can be diffracted according to different diffraction patterns. As a result, the diffraction grating can be used, for example, particularly simply as a direction-selective diaphragm.

According to a preferred refinement, the scanning device of the lidar device according to the invention has a light source, by means of which the light beams can be generated, and an adjustable mirror device, which is designed and arranged with respect to the light source such that the generated light beams are used to scan the scanning region by means of the mirror device are distractible.

According to a further preferred development, the light source is designed to generate the light beams in such a way that they essentially have a specific wavelength. The control device can furthermore be designed to control the diffraction grating in such a way that by means of the diffraction grating a first diffraction maximum of those of the light beams incident on the diffraction grating and having the specific wavelength can be diffracted at least in part towards the light sensor. The diffraction grating can also be controlled in such a way that, by means of the diffraction grating, a second diffraction maximum of those of the light beams incident on the diffraction grating and having a wavelength other than the specific wavelength can be diffracted at least in part towards a first light absorber. The first and / or second diffraction maximum may, for example, be a diffraction maximum with the respective highest intensity of a specific diffraction spectrum, for example a first order diffraction maximum. As a result, useful light - with the specific wavelength - can be directed to a greater extent onto the light sensor than stray light which has a wavelength which differs from the specific wavelength.

According to a further preferred development, the control device is designed to control the adjustable mirror device such that the adjustable mirror device deflects the generated light beams into a first solid angle of the scanning region. The control device can furthermore be designed to control the diffraction grating in such a way that, by means of the diffraction grating, a third diffraction maximum of those of the light rays impinging on the diffraction grating, which impinge on the diffraction grating from the first solid angle of the scanning region, diffracts at least in part towards the light sensor is. The diffraction grating can also be controlled so that a fourth diffraction maximum of those on the Diffraction grating incident light rays, which from a second solid angle of the scanning, which is different from the first solid angle, meet the diffraction grating, at least partially diffractable towards a second light absorber out. As a result, useful light, which emanates from a currently sampled solid angle or solid angle range, can be directed to a greater extent onto the light sensor than stray light, which emanates from a solid angle or solid angle range other than the currently sampled solid angle.

According to a further preferred development, the light focusing device has a lens and / or a lens. It can also be provided more complicated optics or optical devices.

According to a further preferred refinement, the micromechanical diffraction grating functions as a bandpass filter in the infrared range. As a result, unwanted artifacts and stray light effects in the light sensor can be further reduced.

According to a preferred embodiment of the control method, the control method further comprises the method steps: generating light beams, which essentially have a specific wavelength, by means of a light source; Diffracting a first diffraction peak from those of the light rays incident on the diffraction grating having the particular wavelength at least in part toward the light sensor; and / or diffracting a second diffraction peak from those of the light rays incident on the diffraction grating which have a wavelength other than the determined wavelength, at least in part towards a first light absorber.

According to a preferred embodiment of the control method, the control method further comprises the method steps: deflecting light rays generated by a light source into a first solid angle of a scanning region by means of an adjustable mirror device; Diffracting a third diffraction peak of such light rays incident on the diffraction grating from the first solid angle of the scanning region, at least in part, toward the light sensor by means of the diffraction grating; and / or diffracting a fourth diffraction maximum of such light rays incident on the diffraction grating from a second solid angle of the scanning region different from the first solid angle by means of the diffraction grating at least in part toward a second light absorber.

Brief description of the drawings

The present invention will be explained in more detail with reference to the embodiments illustrated in the schematic figures of the drawings. Show it:

1 a schematic representation of a lidar device according to a first embodiment of the present invention; and

2A and 2 B schematically a light detection device according to a second embodiment of the present invention for illustrating a possible function.

In all figures, the same or functionally identical elements and devices - unless otherwise stated - provided with the same reference numerals.

Embodiments of the invention

1 shows a schematic representation of a lidar device according to a first embodiment of the present invention.

According to 1 For example, the lidar device has a light detection device 7 a scanning device 5 and an evaluation device 24 on. The scanning device 5 includes a light source 10 , by means of which light rays 30 can be generated and an adjustable mirror device 12 , By means of the adjustable mirror device 12 are those of the light source 10 generated light rays 30 for scanning a scanning range steerable. According to 1 is the adjustable mirror device 12 a gimbal-mounted micromechanical mirror attached to two axes. It is also conceivable, however, a number of other adjustable mirror devices 12 ie mirror devices whose reflective element can in particular be turned or pivoted.

The of the light source 10 generated and the adjustable mirror device 12 deflected light rays 30 are sent out to scan a scanning area, for example a solid angle area, into the scanning area. The scanning may include that according to a predetermined grid or predetermined scanning lines in continuous or pulsed operation of the light source 10 the rays of light 30 are sent in a solid angle of the scanning range. In the scanning area, the light beams 30 for example, to an external object 14 to meet. At the external object 14 can the light rays 30 wholly or partly as reflected light rays 32 reflected back towards the lidar device.

The light detection device 7 is designed to reflect the reflected light rays 32 at least partially to capture. For example, from a comparison of information about generating the light rays 30 in the light source 10 and that through the light detection device 7 detected reflected light rays 32 can the evaluation device 24 For example, a three-dimensional distance image or a hologram of the external object 14 in the scan area.

The light detection device 7 has a Lichtfokussiereinrichtung 16 for coupling the reflected light beams 32 in the light detection device 7 on. The light detection device 16 For example, it may include a lens and / or a lens. But there are also many other elements in or on the Lichtfokussiereinrichtung 16 be provided, which the beam path and / or properties of the light beams to be coupled by means of Lichtfokussierseinrichtung 32 influence.

In the light detection device 7 are still a light sensor 20 and a micromechanical diffraction grating 18 educated. The light focusing device 16 and the micromechanical diffraction grating 18 are formed and arranged with respect to each other so that by means of Lichtfokussiereinrichtung 16 coupled light beams 34 at least in part on the diffraction grating 18 are focusable. Accordingly, it may be provided that only those of the coupled light beams 34 on the diffraction grating 18 can be focused, which certain properties, for example, in terms of their wavelength and / or their direction of incidence, suffice. The diffraction grating 18 is formed such that the coupled, on the diffraction grating 18 incident light rays 34 depending on adjustable diffraction properties of the diffraction grating 18 at least in part to the light sensor 20 are bendable. Ie that on the diffraction grating 18 incident light rays 34 be bent such that at least one diffraction maximum of a resulting diffraction pattern at least partially the light sensor 20 overlaps. Advantageously, a first order diffraction maximum can be applied to the light sensor 20 directed or bent. The light sensor 20 is for measuring on the light sensor 20 incident light rays 36 educated. In this case, he can in particular a time of impact, a wavelength of the incident light rays 36 and / or a radiation power of the incident light rays 36 measure and, for example, the evaluation device 24 forward relevant information.

For adjusting the diffraction properties of the diffraction grating 18 can the controller 22 be educated. The control device 22 can also generate the light rays 30 by means of the light source 10 and / or deflecting the generated light rays 30 by means of the adjustable mirror device 12 Taxes. But it can be used for the light source 10 and / or the adjustable mirror device 12 each separate control devices may be provided. One or all of the mentioned control devices can be designed as electronic or electromechanical components, but also purely as software that can be executed on a processor.

2A and 2 B schematically show a light detection device according to a second embodiment of the present invention for illustrating a possible function.

According to 2A hit the reflected rays of light 32 on the Lichtfokussiereinrichtung 16 on. The on the Lichtfokussiereinrichtung 16 incident light rays 32 In particular, those light beams which have been sent out for scanning the scanning area and which on the object can be 14 in the scanning area on the Lichtfokussiereinrichtung 16 specularly or diffusely reflected. According to 2A is the diffraction grating 18 trained and / or is so controllable that on the diffraction grating 18 focused, ie on the diffraction grating 18 incident light rays 34 , which fulfill certain characteristics, by means of the diffraction grating 18 can be bent specifically. For example, the light rays incident on the diffraction grating may 34 be bent such that a diffraction maximum of the first order of the diffraction pattern of the diffraction grating 18 diffracted light rays 36 on the light sensor 20 is bent over. The angle of the diffraction maximum with respect to a diffractive surface of the diffraction grating 18 depends on the wavelength of the diffraction grating 18 incident light rays 34 and a lattice constant of the diffraction grating 18 from. Thus, for example, it can be achieved that only those light beams 34 , which have a certain wavelength, are diffracted such that their first order diffraction maximum on the light sensor 20 falls.

When using the light detection device 7 in for example the lidar device according to 1 can be provided that the light source 10 the rays of light 30 produced essentially with a specific wavelength. The diffraction grating 18 may be formed and / or by the control device 20 be controlled such that a first first order diffraction maximum of those on the diffraction grating 18 incident light rays 34 having the particular wavelength to the light sensor 20 is bent over. Furthermore, the diffraction grating 18 be formed and / or by the control device 20 be controlled such that such light rays 44 which have a wavelength which differs from the particular wavelength of the light source 10 generated light rays 30 differs from the diffraction grating 18 diffracted differently than those on the diffraction grating 18 incident light rays 34 which has the particular wavelength. For example, as in 2 B shown a second diffraction maximum 46 first order of the diffraction pattern on a light absorber 22 be bent over. By that is meant that the diffraction pattern 46 is changed so that the second diffraction maximum 46 first order of the diffraction pattern partially, preferably completely, on the light absorber 22 to come to rest.

The light absorber 22 For example, a specially formed plate, but also a part of a housing, which has a low reflectivity, be. The light absorber 22 may have one or more light-absorbing elements. The on the diffraction grating 18 incident light rays 44 can through the diffraction grating 18 be diffracted so that the resulting diffraction pattern 46 is arranged so that a diffraction minimum on the light sensor 20 to come to rest. For example, it can be ensured that stray light from an undesired source 40 , For example, with a certain, frequently occurring wavelength, with the least possible proportion, preferably a vanishing proportion, on the light sensor 20 incident. The stray light can be, for example, sunlight, in particular sunlight with a wavelength frequently represented in the solar spectrum.

The diffraction grating 18 can not only be used as a color filter, ie as a wavelength filter, but can also be used as a direction-selective filter. Based on the control of the adjustable mirror device 12 , for example by the control device 22 , it can be known which solid angle or solid angle range of the scanning region at a certain time of the generated light beams 30 is scanned. Due to the geometry of the lidar device, it may also be known from which direction in this solid angle or solid angle range on the object 14 reflected light rays 32 on the Lichtfokussiereinrichtung 16 hit and like the incident light rays 32 on the diffraction grating 18 be focused. The diffraction grating 18 can be formed as a matrix with a plurality of separately controllable sections, wherein the diffractive properties of each of the separately controllable sections can be set separately. Accordingly, a portion of the diffraction grating 18 on which the from the currently scanned solid angle or solid angle range on the Lichtfokussiereinrichtung 16 incident light beams are set to be set such that a third diffraction maximum of the incident on the section of light rays 34 on the light sensor 20 to come to rest. All other sections of the diffraction grating 18 to which corresponding light beams are incident, which do not originate from the currently sampled solid angle or solid angle range, can be controlled such that a fourth diffraction maximum around the light beams 34 which impinge upon these sections are diffracted towards one or more light absorbers.

Although the present invention has been described above with reference to preferred embodiments, it is not limited thereto, but modifiable in a variety of ways. In particular, the invention can be varied or modified in many ways without deviating from the gist of the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0448111 A2 [0002]

Claims (12)

A light detection device comprising: a light focusing device ( 16 ) for coupling light beams ( 32 ) in the light detection device; a micromechanical diffraction grating ( 18 ), wherein the light focusing device ( 16 ) and the micromechanical diffraction grating ( 18 ) are formed and arranged with respect to each other so that by means of the Lichtfokussiereinrichtung ( 16 ) coupled light beams ( 34 . 44 ) at least in part on the diffraction grating ( 18 ) are focusable, wherein the diffraction grating ( 18 ) is further configured such that on the diffraction grating ( 18 ) incident light rays ( 34 . 44 ) as a function of adjustable diffraction properties of the diffraction grating ( 18 ) at least partially to a light sensor ( 20 ) are bendable, which for measuring on the light sensor ( 20 ) incident light rays ( 36 ) is trained; and a control device ( 22 ), which for adjusting the diffraction properties of the diffraction grating ( 18 ) is trained. A light-detecting device according to claim 1, wherein the diffraction grating ( 18 ) has parallel, reflective strips; and wherein the diffraction properties of the diffraction grating ( 18 ) are adjustable at least in that a first plurality of the reflective strips is temporarily lowered in a direction perpendicular to the direction in which the strips are arranged parallel to one another compared to a second plurality of the reflective strips. Light-detecting device according to one of the preceding claims 1 or 2, wherein the diffraction grating ( 18 ) has a matrix with a plurality of separately controllable sections, wherein the diffractive properties of each of the separately controllable sections can be adjusted separately. A lidar device comprising: the light-detecting device according to one of the preceding claims 1 or 2; and a scanner ( 5 ), which is designed to be illuminated by light beams ( 30 ) to scan a scanning area; wherein the light focusing device ( 16 ) is formed such that from the scanning area on the lidar device incident light beams ( 32 ), on the diffraction grating ( 18 ) are focusable. Lidar device according to claim 4, wherein the scanning device ( 5 ) comprises: a light source ( 10 ), by means of which the light rays ( 30 ) are producible; and an adjustable mirror device ( 12 ), which are formed in such a way and with respect to the light source ( 10 ) is arranged so that by means of the mirror device ( 12 ) the generated light beams ( 30 ) are deflectable for scanning the scanning area. Lidar device according to claim 5, wherein the light source ( 10 ) is adapted to the light beams ( 30 ) such that they have substantially a certain wavelength; and wherein the control device ( 22 ) is further adapted to the diffraction grating ( 18 ) such that by means of the diffraction grating ( 18 ) a first diffraction maximum of those of the diffraction grating ( 18 ) incident light rays ( 34 ) having the particular wavelength, at least in part to the light sensor ( 20 ) and / or that by means of the diffraction grating ( 18 ) a second diffraction maximum ( 46 ) of those on the diffraction grating ( 18 ) incident light rays ( 44 ), which have a different wavelength than the particular, at least partially to a first light absorber ( 22 ) is bendable. Lidar device according to one of the preceding claims 5 or 6, wherein the control device ( 22 ) is adapted to the adjustable mirror device ( 12 ) such that the adjustable mirror device ( 12 ) the generated light beams ( 30 ) deflects into a first solid angle of the scanning area; and further the diffraction grating ( 18 ) such that by means of the diffraction grating ( 18 ) a third diffraction maximum of those on the diffraction grating ( 18 ) incident light rays ( 34 ), which from the first solid angle of the scanning range on the diffraction grating ( 18 ), at least in part to the light sensor ( 20 ) and that a fourth diffraction maximum of those on the diffraction grating ( 18 ) incident light beams, which from a second solid angle of the scanning range, which is different from the first solid angle, on the diffraction grating ( 18 ), at least in part to a second light absorber ( 22 ) is bendable. Lidar device according to one of the preceding claims 1 to 7, wherein the light focusing device ( 16 ) has a lens and / or a lens. Lidar device according to one of the preceding claims 1 to 8, wherein the micromechanical diffraction grating ( 18 ) acts as a bandpass filter in the infrared range. A control method, in particular for controlling the light-detecting device according to claim 1, comprising: injecting light beams ( 32 ) in the light detection device by means of a light focusing device ( 16 ); Focusing coupled light beams ( 34 ) to a micromechanical diffraction grating ( 18 ) by means of the light focusing device ( 16 ); Bending from to the diffraction grating ( 18 ) incident light rays ( 34 . 44 ) as a function of adjustable diffraction properties of the diffraction grating ( 18 ); and adjusting the diffraction properties of the diffraction grating ( 18 ). A control method according to claim 10, in particular for controlling the lidar device according to claim 6, comprising: generating light beams ( 30 ), which essentially have a certain wavelength, by means of a light source ( 10 ); Bending those of a first diffraction maximum of those of the diffraction grating ( 18 ) incident light rays ( 34 ) having the particular wavelength, at least in part to the light sensor ( 20 ); and / or bending a second diffraction maximum ( 46 ) of those on the diffraction grating ( 18 ) incident light rays ( 34 ), which have a different wavelength than the particular, at least partially to a first light absorber ( 22 ). Control method according to one of the preceding claims 10 or 11, in particular for controlling the lidar device according to claim 7, comprising: deflecting by means of a light source ( 10 ) generated light beams ( 30 ) in a first solid angle of a scanning region by means of an adjustable mirror device ( 12 ); Bending a third diffraction maximum of such light rays ( 34 ), which from the first solid angle of the scanning range on the diffraction grating ( 18 ), by means of the diffraction grating ( 18 ) at least in part to the light sensor ( 20 ); and / or diffracting a fourth diffraction maximum of such light rays, which diffracts from a second solid angle of the scanning region, which is different from the first solid angle, to the diffraction grating (US Pat. 18 ), by means of the diffraction grating ( 18 ) at least in part towards a second light absorber.

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