LIGHTING DEVICE FOR ILLUMINATING A SCENE, CAMERA SYSTEM AND METHOD FOR ILLUMINATING A SCENE

Description

AREA OF INVENTION

[0001] The invention relates to a lighting device for illuminating a scene. The invention further relates to a camera system in which such a lighting device is used. Finally, the invention relates to a method for illuminating a scene. BACKGROUND OF THE INVENTION

[0002] Modern cameras, used for applications such as distance measurement, object detection, or gesture recognition, require specific lighting profiles. To capture a two-dimensional (2D) image of a scene, such as an object, with a standard camera, homogeneous flood lighting is needed to illuminate the scene with a uniform illuminance. When the camera is used as a three-dimensional (3D) sensor, lighting with a structured light pattern is required, allowing for triangulation to generate a depth image of the illuminated scene.

[0003] An illumination device of the type mentioned above can also be used with a time-of-flight (TOF) camera. Flood illumination allows the camera to utilize its full resolution, but only at limited distances, as the overall power of the illumination device must be adapted to the eye safety requirements of laser light sources. Using a structured light pattern, also called a spot pattern, concentrates the eye-safe energy onto a few pixels, thereby increasing the signal-to-noise ratio at these pixels and thus enabling longer measurement distances, albeit at the cost of lower resolution. If the illumination device can generate both illumination profiles—i.e., homogeneous flood illumination as well as spot illumination—the TOF camera can measure at different distances.If only one of the two lighting profiles is provided, this limits either the measuring distance or the resolution.

[0004] These specific combinations of functions in a single camera require either two separate light sources that are individually controlled or a single light source that can be switched between flood and spot lighting. Such a lighting device is described in document CN 108332082 A. This lighting device combines the functions of a flood light and a spot light, requiring the device to be switchable between these modes. The lighting device includes a light source for emitting a beam of light, a lens for diverging or converging the beam, a diffractive optical element for widening and directing the beam onto the scene to be illuminated, and a processor for controlling the beam.In one embodiment, the lens is a zoom lens, and the processor is used to change the lens's focal length to achieve flood or spot illumination. In other embodiments, the diffractive optical element has a first diffraction pattern and a second diffraction pattern, wherein the angle between adjacent diffracted light beams is no greater than the opening angle of the incident light beam to achieve flood illumination. The angle between adjacent diffracted light beams diffracted by the second diffraction pattern is greater than the opening angle of the incident light beam to achieve structured light illumination.The light source comprises a first partial light source and a second partial light source. The processor controls the first partial light source to emit a first partial light beam, which is then replicated and spread by the diffractive optical element to create flood illumination. A control device manages the second partial light source to emit a second partial light beam, which is also replicated and spread by the diffractive optical element to create illumination with the spot pattern. The first and second partial light sources have different properties with respect to their light-emitting area, beam angle, and / or light output.This well-known lighting device is therefore structurally complex and thus also costly, since either movable optical elements, different light sources, diffractive optical elements with different diffraction patterns and / or a light beam control are required for the two different lighting profiles of flood lighting and spot lighting.

[0005] Another approach to illuminating a scene is known, for example, from US 2020 / 103672 A1. SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide a lighting device that can simultaneously provide flood lighting and spot lighting for illuminating a scene, and which is structurally less complex and less costly.

[0007] The invention further aims to provide a camera system with such a lighting device and a method for illuminating a scene.

[0008] The invention is defined in the attached claims.

[0009] According to the invention, a lighting device for illuminating a scene is provided, comprising an array of light sources designed to each emit a beam of light, further comprising a first optic and a second optic, wherein the first optic receives the beams of light emitted by the light sources and directs them onto the second optic, wherein the first optic is an imaging optic that projects the individual beams of light into the scene as spots in order to illuminate the scene with a spot pattern, and the second optic is a widening optic that partially widens the beams of light in order to illuminate the scene simultaneously with the spot pattern with a substantially homogeneous illumination profile, wherein the widened portion of the beams of light is less than 90% of the luminous intensity of the beams of light emitted by the light sources.

[0010] The lighting device according to the invention generates a lighting profile in the scene to be illuminated, which is the sum of essentially homogeneous flood lighting and spot lighting. Flood lighting and spot lighting are generated simultaneously and directed into the scene without requiring special control of the light sources, nor light sources with different properties, nor movable, controlled, or switchable optics. How the lighting profile with simultaneous flood and spot lighting is used by the camera will be described later with reference to a camera system according to the invention.

[0011] The first optical element of the lighting device is an imaging element that focuses the light sources onto the scene to be illuminated, meaning that the individual light beams are projected onto the scene as spots. This first optical element can be, for example, a single converging lens, although it can also consist of multiple lenses. The second optical element, located downstream of the first, serves to generate flood illumination, which fills the spaces between the individual spots in the scene with light intensity as evenly as possible. The uniform light intensity between the spots is lower than the intensity of the spots themselves. To achieve this, the second optical element spatially distributes only a portion of the light energy contained in the light beams onto the scene. The second optical element can be designed as a diffusive, refractive, or diffractive element, which partially spreads the individual light beams coming from the first optical element.However, not the entire light intensity of the light beams is spread out, as is the case or desired with standard diffusers, but only a portion of the light intensity of the light beams, so that on the one hand a pronounced spot lighting with higher irradiance in the spots and on the other hand an essentially homogeneous irradiance with lower irradiance between the spots can be achieved.

[0012] The second optical element can be, for example, a transmitting or reflecting diffractive element, such as a diffractive beam splitter. In principle, all types of diffractive elements are suitable for use in the lighting device according to the invention. The second optical element can also be a refractive optical element, such as a scattering element formed from a microlens array, or a diffusive optical element, such as a scattering element.

[0013] The array of light sources can, in particular, be a two-dimensional array. The light sources can be laser diodes, especially vertical cavity surface-emitting lasers (VCSELs). The light beam emitted by a VCSEL typically has a circular cross-section in the far field, and the full aperture angle of the light beam emitted by a VCSEL is typically small, for example, less than 20°.

[0014] At least the first optic can be integrated into the array of light sources. For example, the light sources can be VCSELs, and in the case of substrate-side emitting lasers, the first optic can be integrated into the wafer or the substrate on which the VCSELs are arranged. The second optic can be integral with the first.

[0015] Preferably, the proportion of the light intensity of the light beams widened by the second optic is less than 80%, preferably less than 70%, more preferably less than 60%, and more preferably less than 50% of the light intensity of the light beams emitted by the light sources.

[0016] The smaller the proportion of light energy deflected or spread out from the light beams, the more light intensity remains in the spot illumination. This has the advantage of increasing the measurement distance with a 3D camera, such as a time-of-flight (TOF) camera. This is particularly useful for 3D scanning of distant objects. Conversely, the more light intensity is diverted or spread out from the light beams, the "brighter" the flood illumination. This allows, for example, a well-illuminated 2D image of the scene to be captured when using a camera as a 2D camera.

[0017] Furthermore, preferably the second optic expands the light beams with a maximum expansion angle equal to an angular distance, or an integer multiple thereof, between two light beams minus an opening angle of one light beam.

[0018] This design differs from standard widening optics, such as diffusers, which scatter all light beams from the array of light sources into the entire scene.

[0019] The two light beams mentioned above are preferably immediately adjacent light beams.

[0020] In this configuration, the spreading angle with which the second optic distributes a portion of the light energy between the spots can be limited to the space between the individual light beams. This achieves the smallest maximum spreading angle of the individual light beams.

[0021] If the second optics is a diffractive optics, the diffractive optics is preferably designed such that the angle between intensity maxima of adjacent diffraction orders essentially corresponds to the opening angle of a light beam divided by an integer greater than or equal to 1.

[0022] In this configuration, diffractive optics splits the individual light beams into their respective diffraction orders, such that the individual diffraction orders directly adjoin or even overlap. The opening angle here is the full opening angle of a light beam.

[0023] In this context, it is further preferred if the light intensity at the output of the diffractive optics in the zeroth diffraction order is at least 50%, preferably at least 100%, preferably at least 150%, and more preferably at least 200% greater than in the diffraction order with the second greatest light intensity.

[0024] This configuration is unusual for diffractive optics, as diffractive optics are typically designed to suppress the zeroth diffraction order as much as possible. However, within the scope of the present invention, this configuration is preferred because the zeroth diffraction order corresponds to the propagation direction of the component of the light beam intensity responsible for forming the spot pattern. This results in the spot pattern being created in the scene with sufficiently high irradiance, while the flood illumination is generated by the first and higher diffraction orders.

[0025] If the second optic is a refractive optic comprising an array of microlenses, the fill factor of the lenses in the array is less than 100%, preferably less than 90%, further preferably less than 80%, further preferably less than 70%, further preferably less than 60%, further preferably less than 50%.

[0026] This design differs from refractive dilating optics formed by microlens arrays and used with an array of VCSELs. In typical refractive dilating optics based on microlenses, the aim is always to achieve a fill factor of 100% to avoid direct, undeflected transmission through the optics. In contrast, within the scope of the present invention, it is preferred to design the refractive optics with a lower fill factor, such that a significant portion of the light energy is not deflected. This can be achieved in a practical, very simple embodiment of the microlens array by integrating flat or planar areas into the microlens array, for example, within each lens, between the lenses, or by replacing a portion of the lenses with a flat or planar area.The flat areas should be large enough to minimize diffraction at openings formed by the edges of the flat areas. Therefore, the dimensions of the flat areas should be on the order of several wavelengths of the light emitted by the light sources.

[0027] Furthermore according to the invention, a camera system is provided, comprising a camera having an image sensor and a lighting device according to one or more of the aforementioned embodiments, wherein first pixels of the image sensor capture the part of the scene illuminated with the substantially homogeneous lighting profile and second pixels capture the spot pattern projected into the scene.

[0028] The majority of the pixels of the image sensor "see" the part of the scene illuminated by the homogeneous floodlight of lower irradiance, while a smaller proportion of the pixels "see" the smaller areas of the scene illuminated by the spots of high irradiance.

[0029] Preferably, the camera system includes a camera control designed to set the exposure time of the image sensor, wherein the camera control is designed to set a first exposure time to capture the scene with the substantially homogeneous illumination profile using the first pixels of the image sensor, and a second exposure time that is shorter than the first exposure time to capture the scene with the spot pattern projected onto the scene using the second pixels of the image sensor.

[0030] When the image sensor is used with the first, long, or longer exposure time, the first pixels will generate a sufficient sensor signal to allow a measurement, while the second pixels will be overexposed and excluded from the measurement. The camera can then be used with the short or shorter exposure time, in which case the first pixels will essentially generate no signal or a signal that is too weak and will be excluded from the measurement. The second pixels, however, will generate a sufficient signal strength to allow a measurement at, for example, longer distances. The two measurements can then be combined into a complete image of the scene.

[0031] If the camera is a standard camera, for example, it is preferable for the camera control to be designed to capture a 2D image of the scene from the signal values ​​of the first pixels, and to determine 3D information about the scene from the signal values ​​of the second pixels using triangulation. The 2D image is captured with a long exposure time, as described previously, and the 3D information with a short exposure time.

[0032] Furthermore, preferably in this case, the camera control is designed to replace at least partially the signal values ​​obtained from the second pixels during the first (long or longer) exposure time with signal values ​​obtained from the second pixels during the second (short or shorter) exposure time.

[0033] In this way, a full 2D grayscale image and additionally the 3D information for the positions of the spots in the spot pattern and the scene can be obtained.

[0034] The aforementioned replacement of the signal values ​​of the second pixels can be weighted with the exposure time and the relative irradiance.

[0035] If the camera is a time-of-flight (TOF) camera, the camera control is preferably designed to obtain a first 3D sub-image of the scene from signal values ​​of the first pixels and a second 3D sub-image of the scene from signal values ​​of the second pixels, wherein the camera control is designed to combine the two 3D sub-images into a complete 3D image of the scene.

[0036] With a time-of-flight (TOF) camera used to capture or measure a nearby object, the long exposure time produces a 3D image for the first pixels, while the second pixels are overexposed. The image captured with a short exposure time only provides the 3D partial image for the second pixels, as the first pixels generate too weak a signal. Combining the two partial images yields a full-resolution 3D image, similar to a TOF camera using only flood illumination. However, if the object being observed is far away or exhibits high absorption or low reflection, the second pixels still provide a sufficient signal, at least with the long exposure time. This allows for a 3D image to be obtained, albeit with lower resolution, that still provides 3D information even at large measurement distances or with objects that reflect little light back to the camera.

[0037] Furthermore, according to the invention, a method for illuminating a scene is provided, comprising the steps: Emitting individual beams of light by means of an array of light sources; projecting the beams of light as spots into the scene by means of a first optic to illuminate the scene with a spot pattern; simultaneously with the projection of the beams of light as spots, partially widening the beams of light by means of a second optic to illuminate the scene together with the spot pattern with a substantially homogeneous illumination profile, wherein the widened portion of the beams of light is less than 90% of the total intensity of the beams of light.

[0038] The method according to the invention has the same advantages and features as the lighting device according to the invention, as described above and as described below.

[0039] Further advantages and features will become apparent from the following description and the attached drawing.

[0040] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Exemplary embodiments of the invention are shown in the drawings and are described in more detail below with reference to them. The drawings show: Figur 1 a schematic diagram of a lighting device not according to the invention, comprising an array of light sources and a first optic; Figur 2 a schematic diagram of the lighting device in Fig. 1 , additionally with a second lens; Figur 3 a schematic diagram of the lighting device in Fig. 1 to explain the angular distance between light beams emitted by the light source and their opening angle; Figur 4 a schematic diagram of the lighting device in Fig. 2 , where the second optic is a diffractive optic; Figur 5a ) and b) a top view and a side view of a second optical system, which is a refractive optical system; Figur 6 a schematic diagram of a lighting device according to the invention, with which a scene is illuminated simultaneously with a spot pattern and with a substantially homogeneous lighting profile; Figur 7 a frontal view of a lighting profile; Figur 8 a schematic diagram of a camera system with a camera and a lighting device; and Figur 9 A flowchart of a procedure for illuminating a scene.

[0042] In the figures, identical or comparable elements are consistently marked with the same reference symbols.

[0043] With reference to Fig. 1 und 2 First, two lighting devices are described with which a scene can be illuminated either with only a spot pattern or with only an essentially homogeneous lighting profile without a spot pattern.

[0044] Fig. 1 Figure 1 shows a lighting device 100 for illuminating a scene 102. The lighting device 100 has an array 104 of light sources 106. In the schematic drawing in Fig. 1 Three light sources 106 are shown as examples. However, it is understood that the array 104 can have a large number of light sources 106, for example, 100 or more light sources 106. The light sources 106 can be distributed, in particular, in a two-dimensional arrangement. The light sources 106 can be, and the same applies to the embodiment of a lighting device according to the invention to be described later, laser diodes, in particular vertical cavity surface-emitting lasers (VCSELs). The light emitted by the light sources can be in the visible and / or near-infrared or infrared spectral range. Each light source 106 emits a light beam 108, wherein the light beams 108 are in Fig. 1 are each represented by a line.

[0045] The lighting device 100 further comprises a first optic 110. The optic 110 is an imaging optic that projects the individual light beams 108 into the scene 102 as spots 112. In other words, the first optic 110 images the light sources 106 into the scene 102.

[0046] In Fig. 1 The irradiance E along scene 102 is illustrated in the diagram above. Essentially all the energy of the light emitted by the light sources 106 is contained in the spot pattern, and the irradiance E in the area of ​​the spots 112 is correspondingly high. In the areas 116 between the spots 112, there is no or virtually no light energy. With a lighting profile that illuminates scene 102 with individual, separate spots 112, a 3D image can be captured using a camera, even at greater distances between scene 102 and the camera, albeit with low resolution.

[0047] Fig. 2 The lighting device displays 100. Fig. 1 , wherein a second optic 118 is additionally provided, the first optic 110 directing the light beams 108 onto the second optic 118. In the non-inventive example in Fig. 2 The first optic 110 can also be omitted. The second optic 118 is a widening optic which, unlike the invention, diffuses all the light energy contained in the light beams 108 evenly across the entire scene to be observed, so that the scene 102 is illuminated with a homogeneous illumination profile 120, as shown in the diagram above. Fig. 2 This illustrates how a comparison of Fig. 2 with Fig. 1 This results in the irradiance E (power of the incoming electromagnetic energy striking a surface, relative to the size of the area) being essentially homogeneous in scene 102, but lower than in the individual spots 112 according to Fig. 1 With a homogeneous lighting profile of 120 as in Fig. 2 To illustrate, a 2D image can be captured using a camera.

[0048] For example, if a standard camera is to be used both as a camera for capturing 2D images and 3D images, both lighting profiles, i.e., both the spot pattern according to Fig. 1 as well as the essentially homogeneous lighting profile according to Fig. 2 required. This can be achieved by switching the lighting device 100 between the two lighting types, for example by alternately inserting and removing the second optic 118 from the beam path. However, this involves additional structural effort. The following describes how it can be enabled that the scene 102 is illuminated simultaneously with a spot pattern according to Fig. 1 and a substantially homogeneous lighting profile according to Fig. 2 can be illuminated without requiring a switching of the device, movable optical elements or different light sources 106 in the array 104.

[0049] In principle, this is achieved according to the invention by partially widening the individual light beams, i.e., by spatially distributing or fanning out a portion of the light energy contained in the light beams, in particular by refracting, scattering or diffracting, so that on the one hand a pronounced spot pattern is maintained, and on the other hand the areas in the scene between the spots 112 are illuminated with sufficient irradiance.

[0050] Fig. 3 The lighting device 100 is shown again according to Fig. 1 , where the first optic 110 is only illustrated as a line for simplification. The light beams 108 are in Fig. 3 with their aperture angle determined by the type of light sources 106. In the case of VCSELs as light sources 106, the natural aperture or divergence angle is a few degrees, for example in a range of about 12° to 15°. The first optic 110 converges the individual light beams 108, which propagate downstream of the first optic 110 with an aperture angle α, also known as the spot size angle. The individual light beams 108 are separated from each other by an angular distance γ. Fig. 3 Since it is only a two-dimensional representation, it is understood that the opening angle α is taken in two mutually perpendicular directions and the angular distance γ is also taken in two mutually perpendicular directions in the case of a two-dimensional array 104, whereby the opening angle α and / or the angular distance γ may be different in the two mutually perpendicular directions.

[0051] To create a lighting profile in scene 102 that simultaneously or in total creates a spot pattern according to Fig. 1 and a substantially homogeneous lighting profile according to Fig. 2 The second optic 118 is designed such that, when it receives the light beams 108 from the first optic 110, it receives only a fraction of less than 90% of the intensity of the individual light beams 108 from their direction of propagation, which in Fig. 3 The second optics 118, illustrated by arrows 124, deflect the light beams 108 into the respective space between them. Preferably, the deflected portion of the light beam intensity is less than 80%, more preferably less than 70%, more preferably less than 60%, and more preferably less than 50% of the light beam intensity emitted by the light sources 106. The second optics 118 only needs to widen that portion of the light beam intensity of each beam with a maximum widening angle ϑ that is essentially equal to or greater than the angular separation γ between two light beams 108. In general, regardless of the type of second optics, preferably ϑ ≥ γ · i, where i is an integer greater than or equal to 1. The widening angle ϑ refers to the full width at half maximum (FWHM) of the intensity of a light beam 108 widened by the second optics. The widened orThe spread proportion of the intensity of an exemplary light beam 108a is represented by broken lines 128 in . Fig. 3 Illustrated. The maximum angle ϑ can be minimized if the angle γ between two immediately adjacent light beams is taken as 108.

[0052] This will be explained using an example. Assume that the field of view of a camera is 60° x 45°, and this field of view is to be filled with 20 x 15 spots with a spot opening angle (spot size angle) α of 0.5°. The angular distance γ between immediately adjacent spots is then 3° in both mutually perpendicular directions (60° / 20 spots = 3° and 45° / 15 spots = 3°). The second optic 118 can then exhibit a two-dimensional expansion pattern with a 3° full opening angle at half the intensity maximum, or, for improved homogeneity, a multiple thereof.

[0053] To achieve this, the second optic 118 can be a diffusive, refractive or diffractive optic.

[0054] Fig. 4 Figure 1 shows the case where the second optic 118 is a diffractive optic, for example a diffractive beam splitter, which divides the individual light beams 108 into several light beams by diffraction. The diffractive optic preferably produces N defined diffracted beams in N diffraction orders (excluding the zeroth diffraction order) of as similar intensity as possible, preferably has a defined maximum diffraction order or a defined maximum diffraction angle θ, while the light intensity preferably drops rapidly beyond the maximum diffraction order. In the example in Figure 118, the diffractive optic preferably produces N defined diffraction beams of N diffraction orders (excluding the zeroth diffraction order) of as similar intensity as possible, and preferably has a defined maximum diffraction order or a defined maximum diffraction angle θ, while the light intensity preferably drops rapidly beyond the maximum diffraction order. Fig. 4 The maximum diffraction order is +2 or -2, and N is therefore 4. The maximum diffraction angle θ is then the full angle between the maximum diffraction orders. The maximum diffraction angle can be the angular separation γ between adjacent light beams 108 minus the aperture or spot size angle α, where in particular θ = γ·i - α, where i is an integer. The spread angle ϑ is preferably given as ϑ = θ + α. A maximum angle δ between the different diffraction orders is preferably on the order of the aperture angle or spot size angle α, which in the example above is 0.5°, so that the individual diffracted images of the spots are directly adjacent to or even overlap. The maximum angle δ between the diffraction orders can also be smaller, such that the images of the individual spots overlap.Very good results are achieved when the maximum angle δ between the diffraction orders corresponds to the opening angle (spot size angle) α divided by an integer, i.e. δ = α / j, where j is an integer.

[0055] The second optic 118 can also be a refractive or diffusive optic which, in the example mentioned above, widens the respective light beams with a widening angle of 3° in both mutually perpendicular directions.

[0056] In both the case of a diffractive optic and a refractive or diffusive optic, the second optic 118 is preferably configured such that a substantial portion of the light intensity of each light beam 108 is not diffracted or scattered. In other words, in the case of a diffractive optic as the second optic 118, it is configured such that the light intensity at the output of the diffractive optic in the zeroth diffraction order is at least 50% greater than in the diffraction order with the second-highest light intensity. Preferably, the light intensity at the output of the diffractive optic in each zeroth diffraction order is at least 100%, more preferably at least 150%, and further preferably at least 200% greater than in the diffraction order with the second-highest light intensity. A similar principle applies if the second optic 118 is a diffuse optic.In this case too, it is preferred if the undeflected intensity at the output of the diffusive optics is greater in the aforementioned orders of magnitude than in the scattered directions.

[0057] A diffractive optic can be designed as a transmissive or reflective diffractive optic. It can be designed as a grating, perforated grating, echelle grating, holographic grating, etc., provided that, as previously described, the diffractive optic diffraction ...

[0058] Fig. 5a Figures 1 and 2 show a second optic 118, which is configured as a refractive optic. In this example, the second optic 118 is configured as an array 128 of microlenses 130. Unlike typical microlens-based expanding optics, where it is desirable to bring the fill factor of the lenses close to 100% to avoid scattering losses and, in particular, direct, undeflected transmission through the optic, the array 128 of microlenses 130 is designed so that certain regions 132 of the array 128 do not deflect or scatter the respective light beam, thus preventing a significant proportion of the light energy from being expanded. Preferably, the fill factor of the lenses in the array is less than 90%, more preferably less than 80%, more preferably less than 70%, more preferably less than 60%, and more preferably less than 50%. Fig. 5a Figures ) and b) show, as a simple example, that flat regions 134 can be integrated into the array within some or all of the lenses, or between the lenses. Non-expanding regions can also be achieved by omitting some of the lenses, thus achieving a lens fill level of the array significantly below 100%, for example, 50%. The flat regions 134 should be large enough to minimize diffraction losses caused by edges. In other words, the apertures created by the flat regions should be on the order of several wavelengths of the light emitted by the light sources.

[0059] A diffusive optic as the second optic 118 can be a scattering disc, for example a disc with a rough surface, or a frosted glass, whereby here too there are areas that do not have a scattering effect in order not to scatter a significant proportion of the intensity of the light beams 108 in order to maintain a pronounced spot pattern in the illumination profile.

[0060] Fig. 6 Figure 1 shows a lighting device 100 that incorporates the aspects described above. The lighting device 100 has an array 104 of light sources 106, each emitting a light beam 108. The light beams 108 are projected onto the scene 102 by the imaging first optic 110. The second optic 118 receives the light beams 108 from the first optic 110 and expands a fraction of less than 90% of the light intensity of each light beam 108. The second optic 118 is configured as described above, for example, as a diffracting, refracting, or scattering optic with the properties described above. The resulting lighting profile 150 in scene 102 simultaneously contains a spot pattern of spots 152 and, at the same time, an essentially homogeneous lighting profile 154. In other words, the lighting profile 150 is the sum of the spot pattern 152 and the essentially homogeneous lighting profile 154.The individual spots 152 exhibit a greater intensity or irradiance E in scene 102 than the essentially homogeneous lighting profile 154. The advantage of the lighting device 100 is that the light sources 106 do not need to be different from one another or be operated differently, nor do optics such as the first optic 110 and / or the second optic 118 need to be relocated or moved into or out of the beam path.

[0061] Fig. 7 shows the lighting profile 150 in a frontal view with the spots 152 and the essentially homogeneous lighting profile 154.

[0062] Fig. 8 Figure 1 shows a camera system 200 comprising a lighting device 100 according to one or more of the embodiments described above and a camera 202. The lighting device 100 illuminates the scene 102 with the lighting profile 150, which simultaneously includes a spot pattern of spots 152 and a substantially homogeneous lighting profile 154 with a lower illuminance than the spot pattern, as described above.

[0063] Camera 202 has an image sensor 204. In Fig. 8 An enlarged section of the image sensor 204 is shown in a top view. The camera 202 also has a camera control unit 206.

[0064] Camera 202 records scene 102, which is illuminated with lighting profile 150. The first pixels 208 of the image sensor 204, which are visible in the enlarged section in Fig. 8 The areas not hatched represent the larger part of the scene illuminated by the essentially homogeneous illumination profile 154. Second pixel 210, located in the enlarged section of the image sensor 204 in Fig. 8 Those that are hatched, however, see the smaller part of the scene into which the spot pattern with spots 152 is projected.

[0065] The camera control unit 206 is designed to set the exposure time of the image sensor 204. Specifically, the camera control unit 206 is designed to set a first exposure time T1 to capture scene 102 with the substantially homogeneous illumination profile 154 using the first pixels 208 of the image sensor 204. The camera control unit 206 is further designed to set a second exposure time T2, which is shorter than the first exposure time T1, to capture scene 102 with the spot pattern projected onto the scene using the second pixels 210 of the image sensor 204, including the spots 152.

[0066] When the first (longer) exposure time T1 is set, the first pixels 208 will provide a sensor signal sufficient in terms of the signal-to-noise ratio to allow measurement, while the second pixels 210 will be overexposed and excluded from the measurement. The camera can then be used with the second (shorter) exposure time T2, in which case the first pixels 208 will not generate an image signal or will generate an image signal that is too weak, since the essentially homogeneous illumination profile 154 has a comparatively low irradiance E. The first pixels 208 therefore do not contribute to the measurement and are excluded from it. The second pixels 210 provide a good signal strength at the short exposure time T2 and allow measurement even at greater distances from the scene 102. Both measurements, i.e.,The measurement at the short exposure time and the measurement at the long exposure time can then be combined into a complete image of scene 102.

[0067] For example, camera 202 can be a standard camera or a time-of-flight (TOF) camera.

[0068] If camera 202 is a standard camera, the portion of scene 202 illuminated by the spot pattern can be captured with camera 202 when the shorter exposure time T 2 is set. The camera control then uses triangulation to determine 3D information about scene 102 from the signal values ​​of the second pixel 210, i.e., a depth image of the scene can be captured with a resolution corresponding to the density of the spots in scene 102. If the longer exposure time is set, camera 202 can capture a conventional 2D image using the first pixel 208, while the second pixel 210 is overexposed. The signal values ​​of the second pixel 210 can be replaced in a processing step with the signal values ​​of the second pixel at the shorter exposure time T 2, with the replacement optionally weighted by the exposure time and the relative irradiance.Overall, a full two-dimensional image, for example a grayscale image, and additionally the three-dimensional information for the positions of the spots 152 in the spot pattern of the lighting profile 150 can be obtained.

[0069] If the camera 202 is a time-of-flight (TOF) camera, a scene 102 located close to the camera 202, for example, an object near the camera, can be recorded. If the long exposure time T1 is set, a 3D partial image is generated from the first pixels 208, while the second pixels 210 are overexposed and excluded from the measurement. With the short exposure time T2, a 3D partial image results only from the signal values ​​of the second pixels, since the signal values ​​of the first pixels 208 are too low. Combining the two 3D partial images results in a fully resolved 3D image. In contrast to a TOF camera operated with an illumination device that only provides flood illumination, the camera system according to the invention can also record a distant scene 102, for example, an object located far from the camera 202, or an object that exhibits strong absorption or...The system exhibits low reflection because the second pixels 210 still provide a good signal, at least when the longer exposure time T1 is set. This means that the camera system according to the invention is able to obtain at least a partial 3D image, albeit with lower resolution, even at greater measuring distances or when recording scenes that reflect only a small amount of illumination. This is a significant difference from the conventional case where the TOF camera is operated with an illumination device that only provides flood illumination.

[0070] In Fig. 9 A flowchart of a procedure for illuminating a scene is shown. The procedure has a step S10 according to which individual light beams 108 are emitted by means of the array 104 of light sources 106.

[0071] In step S12, the first optics 110 are used to project the light beams 108 as spots 152 into the scene 102 in order to illuminate the scene 102 with a spot pattern.

[0072] In step S14, while the light beams 108 are being projected as spots 152, a second optical system is used to partially widen the light beams 108, in particular by scattering or diffracting them, in order to illuminate the scene together with the spot pattern 152 with a substantially homogeneous illumination profile 154 using the scattered or diffracted portion of the light intensity of the light beams 108. The scattered or diffracted portion of the light intensity of the light beams 108 is less than 90% of the total intensity of the light beams 108.

[0073] This method can therefore be used to create a lighting profile 150, as is the case in Fig. 6 shown.

Claims

1. Illumination device for illuminating a scene, comprising an array (104) of light sources (106) adapted to emit respective light beams (108), further comprising a first optical unit (110) and a second optical unit (118), wherein the first optical unit (110) receives the light beams (108) emitted by the light sources (106) and directs them onto the second optical unit (118), wherein the first optical unit (110) is an imaging optical unit, which projects the individual light beams (108) into the scene as spots (152) in order to illuminate the scene with a spot pattern, and the second optical unit (118) is an expanding optical unit, which partly expands the individual light beams (108) in order, with the expanded proportion of the light beams (108), to illuminate the scene simultaneously with the spot pattern with a substantially homogeneous illumination profile (154), wherein the expanded proportion of the light beams (108) amounts to less than 90% of the light intensity of the light beams (108) emitted by the light sources (106).

2. Illumination device according to claim 1, wherein the expanded proportion of the light beams (108) amounts to less than 80%, preferably less than 70%, further preferably less than 60%, further preferably less than 50%, of the light intensity of the light beams (108) emitted by the light sources (106).

3. Illumination device according to claim 1 or 2, wherein the second optical unit (118) expands the light beams (108) with an expansion angle (ϑ), which is equal to an angular distance (γ), or an integral multiple thereof, between two light beams (108).

4. illumination device according to claim 3, wherein the two light beams (106) are directly adjacent light beams.

5. Illumination device according ot any of claims 1 to 4, wherein the second optical unit (118) is a diffractive, refractive or diffusive optical unit.

6. Illumination device according to any of claims 1 to 5, wherein the second optical unit (118) is a diffractive optical unit, wherein the diffractive optical unit is configured such that the angle (δ) between intensity maxima of adjacent orders of diffraction substantially corresponds to the aperture angle (α) of a light beam (108), divided by an integer greater than or equal to 1.

7. Illumination device according to any of claims 1 to 6, wherein the second optical unit (118) is a diffractive optical unit, which diffracts the individual light beams (108) respectively with a maximum diffraction angle which is equal to an angular distance (γ), or an integer multiple thereof, between two light beams (108) minus an aperture angle (α) of a light beam (108).

8. Illumination device according to any of claims 1 to 7, wherein the second optical unit (118) is a diffractive optical unit, and wherein the light intensity at the output of the diffractive optical unit in the respective zeroth order of diffraction is at least 50% greater than in the order of diffraction with the second highest light intensity.

9. Illumination device according to claim 8, wherein the light intensity at the output of the diffractive optical unit in the respective zeroth order of diffraction is at least 100%, preferably at least 150%, further preferably at least 200%, greater than in the order of diffraction with the second highest light intensity.

10. Illumination device according to any of claims 1 to 5, wherein the second optical unit (118) is a refractive optical unit having an array (128) of microlenses (130), wherein a fill factor of the microlenses (130) in the array is less than 100%, preferably less than 90%, further preferably less than 80%, further preferably less than 70%, further preferably less than 60%, further preferably less than 50%.

11. Camera system, comprising a camera (202) having an image sensor (204), further comprising an illumination device (100) according to any of claims 1 to 10, wherein first pixels (208) of the image sensor (204) record the part of the scene illuminated with the substantially homogeneous illumination profile (154) and second pixels (210) record the spot pattern projected into the scene.

12. Camera system according to claim 11, further comprising a camera controller (206) adapted to set the exposure time of the image sensor (204), wherein the camera controller (206) is adapted to set a first exposure time in order, with the first pixels (208) of the image sensor (204), to record the scene with the substantially homogeneous illumination profile (154), and a second exposure time, which is shorter than the first exposure time, in order, with the second pixels (210) of the image sensor (204), to record the scene with the spot pattern projected into the scene.

13. Camera system according to claim 11 or 12, wherein the camera controller (206) is adapted to record a 2D image of the scene from signal values of the first pixels (208), and to determine 3D information about the scene from signal values of the second pixels by triangulation.

14. Camera system according to claim 12 or 13, wherein the camera controller (206) is adapted to at least partly replace the signal values obtained by the second pixels (210) during the first exposure time with signal values obtained by the second pixels (210) during the second exposure time.

15. Camera system according to claim 12, wherein the camera (202) is a time-of-flight camera, and wherein the camera controller (206) is adapted to obtain a first 3D partial image of the scene from signal values of the first pixels (208) and a second 3D partial image of the scene from signal values of the second pixels (210), wherein the camera controller is adapted to combine the two 3D partial images to form a 3D image of the scene.

16. Method for illuminating a scene, comprising the following steps: emitting, by means of an array (104) of light sources (106), individual light beams (108), projecting, by means of a first optical unit (110), the light beams (108) as spots (152) into the scene in order to illuminate the scene with a spot pattern, simultaneously with projecting the light beams (108) as spots, partly expanding, by means of a second optical unit (118), the light beams (108) in order, with the expanded proportion of the light beams (108), to illuminate the scene together with the spot pattern with a substantially homogeneous illumination profile (154), wherein the expanded proportion of the light beams (108) amounts to less than 90% of the total intensity of the light beams (108).