System for scene imaging

Abstract

The invention relates to a system for imaging a scene, wherein the system (10, 20, 30) comprises: a recording unit (12, 22, 32) designed to acquire two-dimensional and / or three-dimensional information of the scene (S), which information has light waves (LW) from the scene (S); a first diffractive optical element (14, 24, 34) designed to receive the light waves (LW) from the recording unit (12, 22, 32); an optical waveguide (16, 26, 36) designed to transport the light waves (LW) received by the first diffractive optical element (14, 24, 34), wherein the first diffractive optical element (14, 24, 34) is further designed to inject the light waves (LW) into the optical waveguide (16, 26, 36); and a second diffractive optical element (14, 24, 34) designed to emit the light waves (LW) transported by the optical waveguide (16, 26, 36) out of the optical waveguide (16, 26, 36), it being provided that the system (10, 20, 30) further comprises: a first image sensor (18, 28, 38) and at least one second image sensor (18, 28, 38) designed to acquire the emitted light waves (LW) and to generate first image data (BD) and second image data (BD) therefrom, wherein the first image sensor (18, 28, 38) and the second image sensor (18, 28, 38) are arranged in a region (EB) assigned to the second diffractive optical element (14, 24, 34).

Description

TECHNICAL FIELD

[0001] The invention relates to a system for imaging / making an image of a scene, wherein the system has: a recording unit designed to acquire two-dimensional or / and three-dimensional information of the scene, wherein the information has light waves from the scene; a first diffractive optical element designed to receive the light waves from the recording unit; an optical waveguide designed to transport the light waves received by the first diffractive optical element, wherein the first diffractive optical element is further designed to inject the light waves into the optical waveguide; and a second diffractive optical element designed to eject the light waves transported by the optical waveguide from the optical waveguide. BACKGROUND

[0002] From the document US 9 753 141 B1 an image generation system based on sensors with a minimum latency time between sensor recordings is known.

[0003] From the document WO 94 / 24527 a spectrograph with a plurality of holographic optical transmission gratings is known, which diffract the incident light such that different spectral components hit spatially separated regions of a photodetector.

[0004] From the document US 10 116 915 B2 a system for generating artificial or augmented reality with data acquisition devices different from each other, each having a plurality of sensors, is known. The data acquisition devices, for example holographic cameras, collect scene information from their respective field of view (FOV).

[0005] In a holographic camera or short "HoloCam" light is injected into a light guide by an optical element and transported by means of internal total reflection to another ejecting optical element. A suitable image sensor is provided after the ejecting optical element.

[0006] So-called sensor noise has a large influence on the achievable image quality here. Sensor noise represents different disturbances that influence the pixel value, for example, a temporal course from image to image. This so-called temporal noise here includes photon noise, dark current, readout and quantization noise, local noise, "bias noise" and "gain noise". Today's trend is that sensors are becoming smaller and smaller, while at the same time the resolution is also becoming higher and higher, resulting in smaller and smaller pixels and thus lower and lower sensitivity, so that the susceptibility to noise is also becoming greater and greater. However, the noise behavior of the recorded images does not only depend on the size and the light sensitivity of the individual pixels.

[0007] The dynamic range is also an important photographic criterion. It is significantly smaller in image sensors than, for example, in the human eye. This effect is known from photography: If one looks through a window, the eye can see both the darker interior and the brighter outside world. In contrast, a camera with a significantly smaller dynamic range can usually only take the scene in a correctly exposed manner: either the darker interior, where the window is overexposed, or the outside world, where the interior is significantly underexposed. While the underexposed areas can subsequently be illuminated to some extent, the information from the overexposed areas cannot be recovered.

[0008] Photography with an extended dynamic range can be carried out in principle to date in two ways. On the one hand, the photography can be digitally reprocessed. Usually, the bright areas are correctly exposed and the dark areas are subsequently illuminated. An improved impression of the lighting is thereby produced in the image. On the other hand, a plurality of individual photographs with different settings, for example different exposure times, can be taken consecutively. A plurality of individual photographs are thereby formed which, in the ideal case, can cover the appropriate settings for the darkest to the brightest image areas. In this case, the individual photographs can be combined, wherein the correctly exposed image portions are used by each photograph. For example, the bright areas are correctly photographed and taken up in a short exposure time. However, as the exposure time is lengthened, the dark image areas are better exposed and taken up. SUMMARY

[0009] It is an object of the present application to provide an improved system for imaging a scene which, on the one hand, enables imaging of the scene with an extended dynamic range and, on the other hand, reduces the disturbance of the sensor noise.

[0010] The object is achieved by a system for imaging a scene and a holographic camera having the features described below.

[0011] The present application proposes a system for imaging a scene, wherein the system comprises a photography unit designed to acquire two-dimensional or / and three-dimensional information of the scene, wherein the information has light waves from the scene, a first diffractive optical element designed to receive the light waves from the photography unit, an optical waveguide designed to transport the light waves received by the first diffractive optical element, wherein the first diffractive optical element is further designed to inject the light waves into the optical waveguide, and a second diffractive optical element designed to emit the light waves transported by the optical waveguide out of the optical waveguide. It is provided here that the system further comprises a first image sensor and at least one second image sensor designed to acquire the emitted light waves and to generate first image data and second image data therefrom, wherein the first image sensor and the second image sensor are arranged in a region assigned to the second diffractive optical element.

[0012] Instead of an image sensor that is to be provided, at least two image sensors are provided here in the region of the diffractive optical element that is to emit. The image sensors can thus take a picture of the scene from the same perspective, i.e. from the same position. This in turn enables the image data generated by the two sensors to be combined with one another. An averaged, noise-reduced image of the scene can thus be created.

[0013] The region that is assigned to the second diffractive optical element can here have a plane into which the second diffractive optical element emits light waves, wherein the first image sensor and the second image sensor are arranged in the plane.

[0014] In this regard, the size of the second diffractive optical element can determine the size of the plane, i.e. the size of the emission region (also referred to as "eyebox"). In other words, the size of the second diffractive optical element that is to emit can be determined in such a way that the size of the plane in which light waves of the scene are received is such that the two image sensors can be arranged therein and can take a picture of the same scene. The size of the second diffractive element can also be selected in such a way that further image sensors can be integrated in the plane.

[0015] In one embodiment, the first diffractive optical element can have a first holographic optical element and the second diffractive optical element can have a second holographic optical element. The use of holographic optical elements, which are lighter and more space-saving than conventional optical elements, enables further simplification of the optical arrangement of the system and a reduction in weight.

[0016] The first holographic optical element and the second holographic optical element can have a volume hologram that emits light waves into or out of the waveguide depending on the wavelength of the light waves. The volume hologram can here be used as a transmission grating as well as a reflection grating. Different arrangements of the holographic elements in the waveguide can thus be realized.

[0017] In this regard, the second holographic optical element can have further optical functions for image correction in order to reduce, for example, the distortion of the imaging of the scene.

[0018] The first holographic optical element and the second holographic optical element can have a light-sensitive material, preferably a light-sensitive polymer. It can also be a material such as dichroic water gel, silver halide, refractive crystals, etc.

[0019] The waveguide can have a prism. However, an arrangement with a waveguide with optical fibers can also be realized.

[0020] The first image sensor may have a first sensitivity and / or a first exposure time, and the second image sensor may have a second sensitivity and / or a second exposure time different from the first image sensor. By combining image sensors with different sensitivities with varying exposure times, scenes with large brightness differences can be captured. For example, the first image sensor can acquire bright image areas without overexposure, while the second image sensor can acquire dark image areas without underexposure. The resulting image data can be combined, enabling the scene to be imaged with improved dynamic range.

[0021] The first image sensor and the second image sensor can also convert photons associated with light waves into electrical signals, thereby generating first image data and second image data.

[0022] The first image sensor and the second image sensor may have CMOS sensors and / or CCD sensors.

[0023] The system may further include a processing unit that processes image data generated by the first and second image sensors and thereby produces an image of the scene. The processing unit may also perform additional corrections.

[0024] The aforementioned objective is achieved by a holographic camera having the aforementioned system for scene imaging. Attached Figure Description

[0025] Other advantages and details of the invention are set forth in the following description of embodiments with reference to the accompanying drawings. The drawings show:

[0026] Figure 1 A simplified and schematic schematic diagram of one implementation of a system for scene imaging is shown.

[0027] Figure 2 A simplified and schematic schematic diagram illustrating one implementation of the system is shown.

[0028] Figure 3 A simplified and schematic schematic diagram illustrating one implementation of the system; and

[0029] Figure 4 A simplified and schematic schematic diagram of one embodiment of an image sensor that works in conjunction with the system's processing unit is shown. Detailed Implementation

[0030] exist Figures 1 to 3Figures 1 to 3 show simplified and schematic diagrams of different embodiments of a system 10, 20, 30 for imaging a scene S. The scene S can be the surrounding of the system 10, 20, 30. The system 10, 20, 30 has a taking unit 12, 22, 32, a first diffractive optical element 14, 24, 34 and a second diffractive optical element 14, 24, 34, a waveguide 16, 26, 36 and a first image sensor 18, 28, 38 and at least one second image sensor 18, 28, 38.

[0031] The taking unit 12, 22, 32 acquires two-dimensional or / and three-dimensional information of the scene S, wherein the information comprises light waves LW of the scene S. As shown in Figures 1 to 3 The taking unit 12, 22, 32 can be designed as an objective with a lens which images the light waves LW onto the first diffractive optical element 14, 24, 34. However, this is not limiting. The taking unit 12, 22, 32 can equally be constituted by other optical elements, e.g. mirrors, light barriers, etc.

[0032] The first diffractive optical element 14, 24, 34 receives the light waves LW from the taking unit 12, 22, 32 and injects the light waves into the waveguide 16, 26, 36. The waveguide 16, 26, 36 transmits the light waves LW received by the first diffractive optical element 14, 24, 34 to the second diffractive optical element 14, 24, 34 by total reflection. In this case, the second diffractive optical element 14, 24, 34 ejects the light waves LW transmitted through the optical waveguide 16, 26, 36 from the optical waveguide 16, 26, 36. This is shown by the respective arrows in Figures 1 to 3

[0033] Here different arrangements of the first and second diffractive optical elements 14, 24, 34 in the system 10, 20, 30 can be realized. The diffractive optical elements 14, 12, 24 can for example be arranged within the waveguide 16, 36, which is shown in Figure 1 and Figure 3 However, the diffractive optical elements can also be arranged externally, which is shown in Figure 2 According to the requirements of the system 10, 20, 30, here any arrangement can be realized.

[0034] The ejected light waves LW are then acquired by the first image sensor 18, 28, 38 and the at least one second image sensor 18, 28, 38 and first image data BD and second image data BD are generated therefrom. This is described in detail later with reference to Figure 4 The first image sensor 18, 28, 38 and the at least one second image sensor 18, 28, 38 are here arranged in a region EB which is attributed to the second diffractive optical element 14, 24, 34, which is simplified by the dashed border in​Figures 1 to 3 is shown in Fig. 2.

[0035] The arrangement in the region EB enables the image sensors 18, 28, 38 to acquire the light waves LW of the scene S from the same perspective. The resulting image data can thus be combined with one another or averaged in order to obtain a denoised image of the scene AS.

[0036] In one embodiment, the region EB assigned to the second diffractive optical element 14, 24, 34 can have a plane into which the second diffractive optical element 14, 24, 34 causes the light waves LW to exit, wherein the first image sensor 18, 28, 38 and the at least one second image sensor 18, 28, 38 are arranged in the plane.

[0037] Here, the size of the second diffractive optical element 14, 24, 34 determines the size of the plane, that is to say the exit region, also referred to as the "eyebox". By suitably selecting the size of the second diffractive optical element 14, 24, 34, it is possible to determine the size of the plane such that further image sensors 18, 38, 38 can be arranged in the plane, as is shown, for example, in the embodiment shown in Fig. 2. In Figure 3 Figure 3 The size of the second diffractive element 34 is selected in such a way in Fig. 3 that a total of four image sensors can be arranged in the plane. This is, however, not limiting. Different sizes for the second diffractive optical element 14, 24, 34 and thus an arbitrary number of image sensors 18, 28, 38 can be implemented. By the combination of the image data BD produced by the further image sensors, it is possible to further improve the image quality of the resulting imaging of the scene AS.

[0038] The first diffractive optical element 14, 24, 34 can have a first holographic optical element, and the second diffractive optical element 14, 24, 34 can have a second holographic optical element. The holographic optical elements here have a diffraction grating which is produced by holography. The diffraction grating is, for example, written into or recorded in a volume hologram.

[0039] ​The first and the second holographic optical element can have a volume hologram which lets the light wave LW in or out of the waveguide 16, 26, 36 depending on the wavelength of the light wave. More precisely, the light wave LW is let in or out according to the Bragg condition (phase matching condition), that is, the light wave LW has to have the right wavelength (color) and the right shape (radiation direction, wave front profile). Here, a distinction is made between volume holograms with reflective gratings and volume holograms with transmissive gratings. For transmissive gratings, a part of the incident light wave LW is reflected and a part is absorbed. For reflective gratings, the light wave LW is diffracted for a certain angle and wavelength such that a structured interference is formed. In Figure 1 An embodiment with a reflective grating is shown in Figure 1 A monochromatic (single color) structure is shown in Figure 2 A polychromatic (multi color) structure can also be realized, which is shown in

[0040] In Figure 2 Light waves LW with different wavelengths are let in or out. This can be realized by using multiple holographic optical elements (not shown). It is also possible to use a holographic optical element with a volume hologram, into which multiple diffraction gratings are written.

[0041] An embodiment is shown in Figure 3 which illustrates a monochromatic structure in the case of using a transmissive grating. In this embodiment, the holographic optical element is arranged centrally in the waveguide 36. Here, a part of the incident light wave LW is absorbed and a part is reflected.

[0042] The examples shown in Figures 1 to 3 above are not limiting. Other arrangements and combinations are possible.

[0043] The second holographic optical element can also have other optical functions for image correction. It can for example be written into a volume hologram and can reduce additional disturbances, such as distortions, when the light wave LW is let out.

[0044] The first and the second holographic optical element can have a photosensitive material, preferably a photosensitive polymer. Photosensitive polymers have a good diffraction efficiency and the advantage that they do not have to be additionally chemically treated. It can also be a material like dichroic water glue, silver halide, etc.

[0045] The waveguide 16, 26, 36 can have a prism. It can also be a fiber.

[0046] First image sensors 18, 28, 38 may have a first sensitivity and / or a first exposure time, and second image sensors 18, 28, 38 may have a second sensitivity and / or a second exposure time different from the first image sensors 18, 28, 38. By using different sensitivities and / or exposure times, different sections of scene S can be acquired and combined with varying precision. Therefore, scene S can be imaged with all brightness differences. For example, the sensitivity and / or exposure time can be set such that the first image sensors 18, 28, 38 acquire the bright sections of scene S without overexposure, while the second image sensor 18, 28, 38 acquires the dark sections of scene S without underexposure. By combining the resulting image data BD, for example, by superimposing image data with different exposure times, a high-contrast image of scene S can be produced. For example, using… Figure 2 The multicolor arrangement shown can also produce color images with an extended dynamic range.

[0047] The first image sensor 18, 28, 38 and the second image sensor 18, 28, 38 can convert photons associated with the light wave LW into electrical signals to generate first image data BD and second image data BD. This is achieved through the photoelectric effect, wherein, simplified, photons are absorbed by the image sensor and electrons or charges are triggered.

[0048] Here, the first image sensor 18, 28, 38 and the second image sensor 18, 28, 38 may have CMOS sensors and / or CCD sensors. In a CMOS sensor (“complementary metal oxide semiconductor”), the charge in a pixel is converted into a voltage. This voltage is amplified, quantized, and output as a digital value. A CCD (“charge-coupled device”) sensor consists of multiple planar arranged photosensitive semiconductor elements. Each semiconductor element is a photodetector that converts incident photons into electrons.

[0049] Systems 10, 20, and 30 may also include a processing unit VB that processes image data BD generated by the first image sensors 18, 28, and 38 and the second image sensors 18, 28, and 38, thereby producing an image of the scene AS. In this respect, Figure 4A simplified and schematic diagram showing one embodiment of the image sensor 18, 28, 38 in cooperation with the processing unit VB of the system 10, 20, 30. The light waves LW received by the first and second image sensors 18, 28, 38 are converted into image data BD as described above and provided to the processing unit BV. The processing unit processes the image data BD, wherein additional image corrections can be performed. The imaging of the scene AS is generated by the processed image data BD by a suitable combination.

[0050] Furthermore, the holographic camera can be equipped with the above described system 10, 20, 30 for imaging the scene S.

Claims

1. A system (10, 20, 30) for scene (S) imaging, wherein, The system (10, 20, 30) includes: The imaging units (12, 22, 32) are designed to acquire two-dimensional and / or three-dimensional information of the scene (S), wherein the information has light waves (LW) from the scene (S). The first diffractive optical element (14, 24, 34) is designed to receive light waves (LW) from the imaging unit (12, 22, 32). Optical waveguides (16, 26, 36) are designed to transmit light waves (LW) received by first diffractive optical elements (14, 24, 34), wherein the first diffractive optical elements (14, 24, 34) are also designed to allow light waves (LW) to enter the optical waveguides (16, 26, 36); and The second diffractive optical element (14, 24, 34) is designed to allow light waves (LW) transmitted by the optical waveguide (16, 26, 36) to exit from the optical waveguide (16, 26, 36). The system (10, 20, 30) is characterized in that it further includes: A first image sensor (18, 28, 38) and at least one second image sensor (18, 28, 38) are designed to acquire emitted light waves (LW) and thereby generate first image data (BD) and second image data (BD), wherein the first image sensor (18, 28, 38) and the second image sensor (18, 28, 38) are arranged in a region (EB) associated with a second diffractive optical element (14, 24, 34) and acquire light waves (LW) emitted by the second diffractive optical element (14, 24, 34) from an optical waveguide (16, 26, 36) from the same viewing angle.

2. The system (10, 20, 30) according to claim 1, characterized in that, The region (EB) associated with the second diffractive optical element (14, 24, 34) has a plane into which light waves (LW) are emitted, wherein the first image sensor (18, 28, 38) and at least one second image sensor (18, 28, 38) are arranged in the plane.

3. The system (10, 20, 30) according to claim 2, characterized in that, The dimensions of the second diffractive optical element (14, 24, 34) determine the dimensions of the plane.

4. The system (10, 20, 30) according to any one of claims 1 to 3, characterized in that, The first diffractive optical element (14, 24, 34) has a first holographic optical element, and the second diffractive optical element (14, 24, 34) has a second holographic optical element.

5. The system (10, 20, 30) according to claim 4, characterized in that, The first holographic optical element and the second holographic optical element have volume holograms, which cause the light wave (LW) to enter or exit the optical waveguide (16, 26, 36) according to the wavelength of the light wave.

6. The system (10, 20, 30) according to claim 4, characterized in that, The second holographic optical element has other optical functions for image correction.

7. The system (10, 20, 30) according to claim 4, characterized in that, The first holographic optical element and the second holographic optical element (14) have photosensitive materials.

8. The system (10, 20, 30) according to claim 7, characterized in that, The photosensitive material is a photosensitive polymer.

9. The system (10, 20, 30) according to any one of claims 1 to 3, characterized in that, The optical waveguides (16, 26, 36) have prisms.

10. The system (10, 20, 30) according to any one of claims 1 to 3, characterized in that, The first image sensor (18) has a first photosensitivity and / or a first exposure time, and the second image sensor (18) has a second photosensitivity and / or a second exposure time that is different from that of the first image sensor (18).

11. The system (10, 20, 30) according to any one of claims 1 to 3, characterized in that, The first image sensor (18, 28, 38) and the second image sensor (18, 28, 38) convert photons of light waves (LW) into electrical signals to generate first image data (BD) and second image data (BD).

12. The system (10, 20, 30) according to claim 11, characterized in that, The first image sensor (18, 28, 38) and the second image sensor (18, 28, 38) have CMOS sensors and / or CCD sensors.

13. The system (10, 20, 30) according to any one of claims 1 to 3, characterized in that, The system also has a processing unit (VB) that processes image data (BD) generated by the first image sensor (18) and the second image sensor (18) and thereby produces an image of the scene (AS).

14. A holographic camera having a system (10, 20, 30) for imaging a scene (S) according to any one of claims 1 to 13.

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