BACKGROUND PLAYBACK DEVICE, CAMERA AND METHOD FOR PLAYING A REPRESENTATION OF A VIRTUAL BACKGROUND

Description

[0001] The invention relates to a background playback device for a virtual image recording studio, which is designed to reproduce a representation of a virtual background behind a real subject for a camera recording.

[0002] Furthermore, the invention relates to a camera for recording such a representation of a virtual background and to methods for reproducing a representation of a virtual background by means of a background reproduction device for a recording with an associated camera in a virtual image recording studio.

[0003] Background playback devices can be used, in particular, to recreate a landscape or environment in a recording studio where a recording is to be made using an assigned camera, and which forms a virtual background for the scene being filmed. The recording studio could be, for example, a film studio for recording moving image sequences or a photography studio where individual images or still images are taken. Generally, such recording can involve local storage of image data or transmission to a remote location (e.g., broadcast, streaming). Thus, a virtual background or environment can be created in the virtual recording studio, within which an actor can move during a moving image recording or which can serve as a background for a still image recording.The virtual background mentioned in this context thus comprises image information that represents a background motif and can be directly captured by an associated camera as the seemingly real environment of a (foreground) scene. The representation of the virtual background "behind" a real motif is to be understood comprehensively in this context, since the virtual environment can also be positioned above or below the real motif.

[0004] For example, in video recordings, a background playback device can be used to display a virtual background, allowing a scene to be filmed directly in the intended environment. This can be particularly helpful for acting, as any events occurring in the virtual background can be perceived by the actor, and the actor can react to them. Unlike, for example, using a green screen, where the environment is not visible to the actor, the actor can adapt their performance to any background events, and a director, camera operator, or other personnel involved in the shoot can gain an overall impression of the scene and assess its performance during filming.Furthermore, the entire scene or a corresponding section of a film can be viewed and checked immediately after recording, without having to overlay the background intended for the scene.

[0005] In still photography, such a background playback device can be used, for example, to take photographs in a studio setting—a controlled environment—in virtually any setting, while keeping the entire image in view during the shoot. The background and the actual subject, or person being photographed, can thus be optimally aligned and interact. Furthermore, the captured photograph can be viewed immediately to make any necessary adjustments.

[0006] Furthermore, WO 2020 / 053416 A1 discloses an LED display used as an advertising board for sporting events. The LED display is controlled in such a way that a recording video camera can generate different video outputs with various advertising messages, while spectators watching the sporting event on-site always see the same display. The patent also describes how to shift a shutter signal in a camera photographing the advertising board depending on the control of the LED display.

[0007] To display the virtual background, background display devices can, in particular, form or include an electronic display with an active pixel matrix and, for example, an active lighting device with a multitude of light sources. For instance, an LED wall can be used to display a virtual background in a virtual image capture studio. The LEDs in such a wall can be individually and / or in groups of adjacent LEDs or in arrays controllable. The LEDs in such an LED wall can be, for example, LEDs (Light Emitting Diodes) or OLEDs (Organic Light Emitting Diodes). Furthermore, the LEDs can be part of a liquid crystal display.Such background playback devices can, for example, extend over a width of at least 5 m and a height of at least 2 m in order to be able to record several actors in front of a common (virtual) background.

[0008] Furthermore, background playback devices can comprise multiple panels on which the pixel elements are arranged and which together form the LED wall.

[0009] While the panels, also commonly referred to as panels, are essentially two-dimensional and the pixel elements arranged on a panel can extend in a planar arrangement, a suitable arrangement of several panels can, for example, result in the background display being curved and / or arched in sections. This allows the background display to be positioned behind, above, or below the real subject in the virtual image capture studio, enabling the direct recording of a virtual sky, a virtual ceiling, or a virtual floor within the studio.As an alternative to an LED wall, a virtual background can also be created using points of light generated by reflection or transmission off a light source wall, such as a screen for rear projection. The active light generation can be provided by a projector, with the light sources on the screen being only indirectly generated.

[0010] In particular, such a background playback device can enable the visual representation of a virtual background, which can represent a three-dimensional scene, by appropriately controlling the pixel elements, and / or by adjusting the control during recording. A background playback device thus offers a way to display a vivid and easily adjustable virtual background for a scene being recorded, thereby facilitating acting or gestures.

[0011] To record a moving image sequence in the virtual image recording studio, the camera can, for example, generate a sequence of images of the virtual background, whereby the camera can record these images at a predefined or adjustable frame rate. Similarly, the background playback device can be configured to change the virtual background display over time, for example, to reproduce movements within the virtual background. This change in the display can also occur at a specific refresh rate, so that the displayed images can be changed or replaced with the next image at that refresh rate.

[0012] In principle, when recording in such a virtual image capture studio, it is advisable to synchronize the image capture rate of the camera used for recording and the refresh rate of the background playback device, so that each display of the virtual background by the background playback device corresponds to a respective image generated by the camera. Furthermore, the background playback device can be configured to display the virtual background at a specific light pulse frequency that is higher than the refresh rate. The associated camera can thus register multiple light pulses, each representing a different virtual background, during a single image capture.

[0013] However, even with such synchronization between the update frequency of the background playback device and the image acquisition frequency of the camera, the problem remains that the camera does not usually produce an image during an entire image acquisition time, but rather any light-sensitive elements of the camera are only exposed during an adjustable exposure time and / or within an adjustable exposure window, which can be freely selected and does not necessarily have to be coupled with the image acquisition frequency.Since camera settings that are independent of the image capture frequency but relevant to image acquisition can be made, synchronization between the camera's image capture frequency and the refresh rate of the background playback device alone may be insufficient to achieve a natural rendering of the virtual background that resembles a real background corresponding to the virtual background. For example, different areas of a light-sensitive element in the camera may register a different number of light pulses during a single exposure, depending on the exposure setting, so that different areas of the image produced by the camera may also be exposed differently.Furthermore, insufficient synchronization between the camera and the background playback device can lead to a so-called tearing effect in the image produced by the camera, if the representation of the virtual background is updated during an exposure and ultimately two different representations of the virtual background are depicted in the same image.

[0014] It is therefore an object of the invention to provide possibilities for recording a representation of a virtual background, which is reproduced by a background playback device in a virtual image recording studio, by which uniformly illuminated images of the representation of the virtual background can be generated and image errors arising due to updates of the representation can be avoided.

[0015] This problem is solved by a camera according to claim 1, a background playback device according to claim 12 and a method according to claim 13.

[0016] In general, this problem is solved by a method for reproducing a representation of a virtual background using a background playback device for a recording with a camera in a virtual image recording studio, wherein the reproduction of the representation of the virtual background is controlled according to a time schedule and wherein the camera records the reproduction of the representation of the virtual background according to a sequence of exposure times. Furthermore, in the method, the time schedule for the reproduction of the representation of the virtual background and the sequence of exposure times are synchronized with each other.

[0017] To enable such synchronization of the timing control of the virtual background rendering and the sequence of exposure times, the camera and the background playback device can be linked, in particular via a network. Such a link can specifically allow synchronization of time signals between the camera and the background playback device via a suitable network protocol, for example, PTP (Precision Time Protocol), as will be explained further below.

[0018] In some embodiments of this method, the background rendering device can comprise a plurality of actively illuminated pixel elements, in particular a plurality of light-emitting diodes, forming a two-dimensional arrangement. In particular, the actively illuminated pixel elements can be individually and / or in groups of pixel elements controlled to render the virtual background.

[0019] In some embodiments, the background display device can further be configured as an LED wall and the pixel elements as light-emitting diodes or LED units. The LEDs of such an LED wall can, for example, be configured as LEDs (Light Emitting Diodes) or as organic light-emitting diodes (OLEDs). Furthermore, in an LED wall, the individual pixel elements that together generate the virtual background can be formed by individual LEDs. However, the individual pixel elements can also be formed by individual LED units, each LED unit comprising, in particular, several, especially three, LEDs.For example, a light-emitting diode (LED) unit can also comprise three, four, or more LEDs, wherein the multiple LEDs of an LED unit can, in particular, have different emission spectra and can optionally be equipped with a color mixer. Furthermore, such an LED unit can be provided in such a way that the individual LEDs of the LED unit can be selectively controlled in order to generate a desired color of the pixel element formed by the LED unit. In particular, an LED unit can comprise a red light-emitting LED, a green light-emitting LED, and a blue light-emitting LED.

[0020] In some embodiments, the pixel elements may be individually controllable to generate the virtual background. In particular, by controlling the pixel elements, the color and / or brightness of each pixel element can be adjusted, allowing a section or point of the virtual background represented by that pixel element to be set to the desired color and / or brightness.

[0021] In some embodiments, the background rendering device can extend in a vertical and / or horizontal orientation, particularly with continuous or quasi-continuous transitions. For example, the background rendering device may extend vertically in a plane behind the real subject to reproduce the virtual background behind the real subject. Alternatively or additionally, the background rendering device may extend at least partially in a horizontal orientation, so that the virtual background can also be reproduced over the real subject, for example.Furthermore, the background display device can be designed to surround and cover the real subject in order to enable the most complete possible reproduction of the virtual background over a wide angular range. In a section where the background display device transitions from a vertical to a horizontal orientation, it can also be curved and / or arched. Particularly when the background display device is composed of several panels, the panels can be arranged into various geometries, such as arched shapes, to create a desired environment for a shot in the virtual image-capture studio. In some embodiments, the background display device may also be arranged section by section on the floor of the virtual image-capture studio.Even in such sections, the background playback device can extend, particularly in a horizontal orientation.

[0022] In some embodiments, the background rendering device can further be configured to illuminate the real subject. In particular, this background rendering device can serve to illuminate the real subject in addition to any other lighting in the virtual image-capture studio. For example, this can ensure that the real subject casts the expected shadow when light sources, such as a streetlamp, are present in the virtual background, by rendering the streetlamp in the virtual background as if it were illuminated by a real streetlamp.However, the background playback device can also be configured to emit light section by section to illuminate a scene and, in a sense, to act as a spotlight, while in other sections the background playback device can reproduce the display of the virtual background.

[0023] In some embodiments, the background playback device can also be configured to vary the display of the virtual background during recording, particularly during the recording of a scene, in conjunction with the camera. Specifically, this allows events occurring in the virtual background during camera recording to be played back directly by the background playback device, enabling an actor, unlike in a green screen recording, to react to these events and adjust their performance accordingly. Consequently, the background playback device can be configured to play back a film sequence during camera recording, which can be recorded directly by the camera. Subsequent overlaying of the camera recording with a predefined background is therefore no longer necessary.

[0024] The camera can be, for example, an analog or a digital camera and may contain a light-sensitive element, which could be, for example, film or an image sensor. In particular, the camera may be a moving image camera (also known as a motion picture camera), designed to produce a sequence of recorded images. Each recorded image can correspond to a separate exposure of the light-sensitive element, so that two consecutive images can be separated by an exposure pause in which light is either blocked or not taken into account.

[0025] In particular, a camera designed as a moving image camera can produce successive images at a specific or adjustable frame rate, so that a specific frame rate, the reciprocal of the frame rate, is available for each image. The exposure time can correspond to the portion of the frame rate during which the light-sensitive element is exposed to light. For the remaining portion of the frame rate, the light-sensitive element can be protected from light exposure, for example, by mechanically closing a camera shutter or by considering only the charge generated on the sensor's light-sensitive elements as a result of light exposure during the exposure time, while disregarding charge generated outside the exposure time, in order to create a digital image data set.This can be achieved, for example, by clearing the charge of the sensor elements before a planned exposure using a suitable circuit, or by resetting it to a reference value. The exposure and image capture then begin with completely discharged sensor elements, and the sensor elements are read out after the exposure time has elapsed. Such a circuit for reading out an image sensor is described, for example, in DE 10 2010 035 811 A1.

[0026] In general, the exposure time can thus correspond to the duration of an exposure during which a light-sensitive element of the camera is exposed to light. Furthermore, the camera's exposure time can extend from the beginning of photoelectric or photochemical signal generation in a first light-sensitive area to the end of this signal generation in a final light-sensitive area of ​​the camera. This is particularly useful when the camera has a so-called global shutter, in which all areas of the light-sensitive element are read out simultaneously and / or protected from light, so that the exposure in every area of ​​the light-sensitive element can begin and end at the same time.

[0027] However, it is also possible to expose different areas, and in particular different rows of light-sensitive sensor elements, of a camera's image sensor sequentially, for example, by reading out the individual rows of the image sensor one after the other. In such a successive row-by-row readout of an image sensor, for instance, one row of sensor elements can be exposed first, with the exposure of a subsequent row beginning as soon as the exposure of the preceding row is complete and the readout of the charge generated during the exposure in the preceding row has begun. The exposure times of the individual rows of the image sensor can thus be offset from one another. Such a readout and exposure of the sensor element rows enables, in particular, the electronic simulation of a mechanical rolling lens shutter.A rolling shutter is a lens shutter in which the opening of a lens shutter moves across or along the light-sensitive element—film or an image sensor—so that different areas of the light-sensitive element are exposed to light and then closed again at different times. With such a mechanical or electronic rolling shutter, the exposure times can ultimately be the same for all areas or lines of the light-sensitive element, although the starting times of the exposures for the individual areas or lines can differ.

[0028] Exposure time can generally correspond to the exposure time set by a camera operator on the camera, and in the case of an electronic camera with an image sensor, the term specifically refers to the duration of the exposure of a particular sensor element. In the case of a rolling shutter, this is specifically the duration of the exposure of the sensor elements in each row, whereby the exposure times of the different rows can be offset from each other and the exposures of the individual rows can begin at different times. The time interval from the start time of the exposure of the first sensor element (e.g., the first sensor row) to the end time of the exposure of the last sensor element (e.g., the last row) is called the exposure time.The exposure window (of the last sensor row) can therefore be described as the exposure window, so that in a rolling shutter, due to the staggered exposure times of the individual rows of sensor elements, the exposure window can ultimately be longer than the individual exposure time. Similarly, in a mechanical rolling shutter, the exposure time can refer to the duration for which a particular point of the camera's light-sensitive element—film or image sensor—is exposed to light during a single image capture. Even in a mechanical rolling shutter, the exposure time is shorter than the camera's exposure window, which defines the time interval from the start of exposure of the first exposed area of ​​the light-sensitive element to the end of exposure of the last exposed area of ​​the light-sensitive element.

[0029] In a global shutter, where the charge of all light-sensitive sensor elements of an image sensor is read out simultaneously, the exposure window can correspond to the exposure time. More generally, in both a rolling shutter and a global shutter, an exposure pause can occur between two successive exposure windows. During this pause, any incident light is not converted into a sensor signal by any of the sensor elements of an image sensor, or the light-sensitive element is mechanically protected from light.

[0030] By synchronizing the timing of the virtual background display's rendering with the sequence of exposure times, the problems mentioned earlier can be addressed. Specifically, synchronizing the rendering time can involve adjusting the frequency and / or timing or phase of the background display's control signal, or the control signal for parts of it. For example, the phase of update points at which the virtual background's rendering is changed by the background display can be adjusted based on the exposure times, and in particular, such that the rendering changes only outside the exposure time and / or exposure window of the camera, thus avoiding the tearing effect described earlier.Synchronizing the sequence of exposure times can involve adjusting the frequency of successive exposures, adjusting the timing or phase of each exposure, or adjusting the duration of each exposure. For example, adjusting the phase of the start time of an exposure within an image capture time can shift the camera's exposure window and / or exposure time within that timeframe, resulting in a change in the rendering of the virtual background outside the camera's exposure window.

[0031] For example, by synchronizing the timing of the background playback device and the sequence of camera exposure times, the exposure times can be further coordinated with a light pulse frequency of the background playback device, which it uses to reproduce the virtual background, in such a way that each area of ​​the camera's light-sensitive element, and in particular each line of sensor elements of an image sensor, registers the same number of light pulses during an exposure time. This can, for example, prevent brightness differences between different lines of the image sensor if the lines are exposed and / or read out at different times.

[0032] Furthermore, the camera's frame rate and the background playback device's refresh rate can be coordinated so that the camera can capture an initial image of the virtual background during each exposure, and then capture a second image of the virtual background, modified from the first, in the subsequent exposure. The frame rate can thus correspond to the refresh rate. However, it is also possible for the frame rate to be higher than the refresh rate, and in particular to be an integer multiple, for example, two or four times the refresh rate, so that the camera can, for instance, generate two images of the first image and two images of the second image.

[0033] Further embodiments can be found in the claims, the description and the drawings.

[0034] The invention further relates to a method for reproducing a representation of a virtual background by means of a background reproduction device, in particular a background reproduction device as disclosed herein, for a recording with a camera, in particular a camera as disclosed herein, in a virtual image recording studio. In this method, the representation of the virtual background is reproduced intermittently according to a light pulse frequency and recorded according to an exposure time of the camera. Furthermore, in the method, the exposure time of the camera is set as a function of the light pulse frequency of the background reproduction device, or the light pulse frequency of the background reproduction device is set as a function of the exposure time of the camera.In this method, the camera's exposure time and / or the light pulse frequency of the background playback device is also set such that the exposure time corresponds to an integer multiple of the reciprocal of the light pulse frequency.

[0035] As already explained, the background playback device can be configured to reproduce the virtual background in a pulsating manner with a specific and / or adjustable light pulse frequency, whereby this light pulse frequency can be many times higher than the image acquisition frequency. In particular, the light pulse frequency can correspond to an integer multiple of the camera's image acquisition frequency, and, for example, with a camera image acquisition frequency of 60 fps (frames per second) or 60 Hz, the background playback device can be operated with a light pulse frequency of 1920 Hz or 3840 Hz, while with an image acquisition frequency of 50 Hz, for example, 1600 Hz or 3200 Hz can be provided as the light pulse frequency. This also applies to image acquisition frequencies of 24 Hz or 60 Hz.For example, the background playback device can be operated at 24 fps with a light pulse frequency of 1920 Hz or 3840 Hz.

[0036] While the light pulse frequency of the background playback device can be synchronized with the camera's image acquisition frequency, which can also correspond to the update frequency of the background playback device, the camera's exposure time can, in principle, be freely adjustable and correspond to any fraction of the image acquisition time. Therefore, the camera's exposure time, or an exposure window during which, for example, individual lines of an image sensor operating as an electronic rolling shutter are exposed sequentially with the set exposure time, can be independent of the image acquisition frequency. Consequently, despite the synchronization between the camera's image acquisition frequency and the light pulse frequency, there can be no integer relationship between the light pulse frequency of the background playback device and the camera's exposure time.

[0037] However, since, especially in cameras with a rolling lens shutter, different areas of a light-sensitive element, for example different lines of an image sensor, can be exposed at different times, the lack of a connection between the exposure time and the light pulse frequency means that different numbers and / or different irregularly incomplete light pulses can be registered in different lines of sensor elements during an image capture, which can lead to a modulation of the brightness across the different areas or lines in the image of the virtual background produced by the camera.

[0038] However, by synchronizing the camera's exposure time and the light pulse frequency of the background playback device such that the exposure time corresponds to an integer multiple of the reciprocal of the light pulse frequency, it is possible, for example, to ensure that each line of a line-by-line exposed and readout image sensor registers the same number of light pulses during an exposure, thus preventing modulation across the image sensor's lines. In particular, such synchronization also ensures that, even with a phase shift between the start times of the individual exposures of the image sensor's lines, the portion of a light pulse that is still registered in that line at the beginning of an exposure in a particular line is clipped.In total, each line can therefore capture a constant, integer number of complete light pulses. Specifically, synchronization can be achieved such that the exposure time is an integer multiple of the reciprocal of the light pulse frequency greater than one. Accordingly, each line of the image sensor can capture at least two light pulses for each exposure.

[0039] Synchronization of the camera's exposure time and the background playback device's light pulse frequency can be achieved by adjusting the exposure time on the camera or by adjusting the light pulse frequency on the background playback device. Adjusting the exposure time on the camera can, for example, be done automatically by setting the exposure time to an integer multiple of the reciprocal of the light pulse frequency. Alternatively, the adjustment can be made manually on the camera, for example, by displaying user-selectable permissible exposure times that are integer multiples of the reciprocal of the light pulse frequency.The background playback device can also be designed to automatically adjust the light pulse frequency according to the camera's exposure time and / or to display a selection of possible light pulse frequencies to the user, from which the user can choose.

[0040] In some embodiments, the method can further determine the camera's exposure time and / or the light pulse frequency of the background playback device. For example, the light pulse frequency of the background playback device can be transmitted to the camera so that the camera and / or a camera control unit can determine permissible exposure times that are multiples of the reciprocal of the light pulse frequency. The permissible exposure times can be displayed, for example, on the camera, particularly on a display, so that a user can manually select between the permissible exposure times.Alternatively, the camera's exposure time can be transmitted to the background playback device, so that, for example, a control unit of the background playback device can adjust the light pulse frequency so that the exposure time corresponds to an integer multiple of the reciprocal of the light pulse frequency, or corresponding light pulse frequencies can be displayed to the user and offered for selection.

[0041] Furthermore, a method for reproducing a representation of a virtual background by means of a background playback device, in particular a background playback device as disclosed herein, for a recording with a camera, in particular a camera as disclosed herein, in a virtual image recording studio is disclosed, wherein the representation is changed at update times and recorded according to a respective exposure of the camera. In this method, exposure pauses of the camera between successive exposures are set depending on the update times of the background playback device, or the update times of the background playback device are set depending on exposure pauses of the camera between successive exposures.Furthermore, the respective settings for the exposure pauses and / or the update times are such that a change in the display of the virtual background occurs during a camera exposure pause.

[0042] By coordinating the update times with the camera's exposure pauses, it is particularly important to ensure that the virtual background is not altered at the same time as a section or line of the camera's light-sensitive element—an image sensor or film—is exposed. Changing the representation during exposure, especially in cameras with a rolling shutter, can lead to some lines or sections of the light-sensitive element recording the originally displayed image while others register the altered image. Consequently, the final image produced by the camera may contain different sections of the virtual background, making the image appear split into two parts.

[0043] However, by coordinating the update times with the camera's exposure pauses, this so-called tearing effect can be avoided, as the image is only updated during the exposure pauses. During a single exposure, the camera can thus capture unchanged representations of the virtual background, ensuring that the same representation of the virtual background is captured in each line of an image sensor.

[0044] To achieve this, the camera's frame rate can be synchronized with the update rate of the background playback device—that is, the rate at which the background playback device changes the display of the virtual background. For this purpose, the frame rate can be equal to the update rate or chosen as an integer multiple of the frame rate. Furthermore, a phase of the camera's exposure time and / or exposure pause within a frame can be set such that the update times of the background playback device coincide with the camera's exposure pauses.As an alternative to adjusting the camera settings, the update times on the background playback device can also be synchronized with the camera's exposure pauses by offsetting them from the start of an exposure and / or exposure window in such a way that the virtual background display changes during the camera's exposure pauses. Such coordination between the update times and the exposure pauses can be achieved, in particular, by linking the camera and the background playback device in a network, so that the respective time signals of the camera and the background playback device can be synchronized with each other via a suitable network protocol, such as PTP (Precision Time Protocol).Furthermore, by ensuring that the camera's frame rate and the background playback device's refresh rate are identical, the refresh times and exposure pauses can repeat at the same frequency, so that subsequent refresh times always coincide with a corresponding exposure pause. This can also be achieved if the frame rate is chosen as an integer multiple of the refresh rate. Even with such a match between the refresh rate and the frame rate, it is still possible for a subsequent refresh time to coincide with a camera exposure pause, provided that the preceding refresh time also coincided with an exposure pause.

[0045] Furthermore, the invention relates to a camera for recording a representation of a virtual background, which is intermittently reproduced in a virtual image recording studio by means of an associated background playback device according to a light pulse frequency. The camera comprises an interface for receiving a value of the light pulse frequency of the associated background playback device and a control device, wherein the control device is configured to control the camera according to an adjustable exposure time. The control device is further configured to determine several permissible exposure times depending on the received value of the light pulse frequency.

[0046] In particular, the camera's interface can be configured to receive the light pulse frequency from the background playback device, either wired or wirelessly. For example, the camera's interface can receive the light pulse frequency directly from the background playback device, which may also have its own interface. Alternatively, the light pulse frequency of the background playback device can be entered via a user input on the camera, allowing the control unit to determine the permissible exposure times based on this user input. For this purpose, the camera's control unit can be connected to the camera's interface. Furthermore, the control unit can be configured as a CPU (Central Processing Unit) and / or microprocessor.By designing the control unit to determine several permissible exposure times depending on the value of the light pulse frequency, it can be ensured, in particular, that when a permissible exposure time is set during an exposure, the same number of light pulses are registered at different areas or lines of a light-sensitive element of the camera, for example, a film or an image sensor, when the different areas are exposed to light for that exposure time. Permissible exposure times are determined such that an integer number of light pulses from the background playback device are registered during an exposure time.By matching the exposure time to the light pulse frequency of the background playback device in this way, modulations of brightness in an image of the virtual background generated by the camera can be avoided in particular.

[0047] In some embodiments, the camera may have an electronic or mechanical rolling lens shutter.

[0048] An electronic rolling shutter is described, for example, in DE 10 2010 035 811 A1.

[0049] Such an electronic rolling shutter can be formed by an image sensor that has a multitude of light-sensitive sensor elements arranged in rows and columns, with the image sensor being read out line by line. To enable this, the exposures for the individual exposures can be slightly offset in time, so that the respective exposure times of the individual lines are shifted without this shift being directly related to the camera's frame rate. In particular, such control of the image sensor can simulate a mechanical rolling shutter, in which a mechanical lens shutter can be successively moved to close an aperture, so that individual areas of a film or image sensor of the camera are exposed at different times.Even with a mechanical rolling shutter, differences in the number of light pulses received at various positions on the film or image sensor can occur. However, a rolling shutter can be used, particularly in motion picture cameras, to create moving image recordings and to depict natural-looking movements in the resulting image sequences.

[0050] In some embodiments, the camera can have an image sensor with a plurality of light-sensitive sensor elements. The image sensor can, in particular, be a CMOS image sensor and / or have a pixel matrix comprising a plurality of pixels arranged in multiple rows and columns. Each pixel can be configured to generate an electrical charge from light incident during an exposure. Furthermore, the image sensor can include a readout device configured to read out, row by row, the electrical charge generated at the pixels of the pixel matrix during the exposure and convert it into a corresponding digital pixel value. The pixel values ​​of the pixel matrix can then be output as a digital data set. As already explained, such a row-read image sensor can, in particular, form an electronic rolling shutter.

[0051] The control unit is designed to determine the permissible exposure times such that the permissible exposure times correspond to integer multiples of the reciprocal of the light pulse frequency. In particular, the permissible exposure times can be defined by integer multiples of the reciprocal of the light pulse frequency greater than one.

[0052] For example, the camera might be designed to capture images at a frame rate of 24 Hz (24 fps), while the background playback device operates at a light pulse frequency of 1920 Hz. In this case, eighty light pulses can be generated per captured image or during each frame rate. Therefore, in this example, eighty permissible exposure times can be determined, each with a duration of n x 1 / 1920 Hz, where n = 1 to 80.

[0053] By selecting permissible exposure times in this way, it can be ensured that a complete, integer number of light pulses are registered in each exposure time. Particularly in cameras with a rolling shutter, this ensures that the same number of light pulses are captured in each area or line of the light-sensitive element—film or image sensor—during an exposure, thus preventing modulation of brightness in the image of the virtual background produced by the camera.

[0054] The camera's control unit can be configured to determine all permissible exposure times that are integer multiples of the reciprocal of the light pulse frequency. However, the control unit can also be configured to consider an upper and / or lower limit for the permissible exposure times and, for example, to process only exposure times that fall within the upper and / or lower limit. In particular, at least only exposure times that are less than or equal to the image acquisition time can be considered. This will be explained in more detail below.

[0055] In some embodiments, the control unit can be configured to determine the multiple permissible exposure times such that they lie within a predetermined permissible range. In particular, only those integer multiples of the reciprocal of the light pulse frequency that lie within the predetermined permissible range can be considered. The control unit can also be configured to take into account limits on the adjustable exposure times. In addition to the aforementioned upper limit of the exposure time, which is the total image acquisition time, a lower limit can be defined, for example, by a camera-specific and / or sensor-specific minimum exposure time that enables image acquisition with signals above mere noise.

[0056] In some embodiments, the control device can be configured to determine the permissible exposure times computationally or by looking them up in a table. For example, the control device can be connected to a memory, in particular a non-volatile memory and / or semiconductor memory, in which permissible exposure times for different light pulse frequencies are stored. In particular, the memory can contain a table for each of the various, especially common, light pulse frequencies, which includes the permissible exposure times for that light pulse frequency. Alternatively, the control device can also be configured to calculate a light pulse duration as a minimum permissible exposure time based on the light pulse frequency, in order to then determine all permissible exposure times as integer multiples of the light pulse duration.

[0057] Furthermore, the control device can be configured to control the camera according to one of the specified permissible exposure times. In particular, the control device can control an image sensor, a readout of an image sensor, or a lens shutter such that individual lines or areas of a light-sensitive element of the camera, film, or image sensor are exposed according to one of the specified permissible exposure times. The control device can therefore be configured to automatically set a permissible exposure time on the camera.

[0058] In some embodiments, the camera may also include a playback device for transmitting information to a user and be configured to display information about the specific permissible exposure times on the playback device. For example, the camera may include a display on which such information is shown. The information may be displayed, in particular, on an electronic viewfinder of the camera or on a separate display arranged on the outside of the camera housing. Such a display may also be configured as a touchscreen, allowing a user to directly adjust settings, such as the exposure time, on the display or playback device.

[0059] In some embodiments, the information may represent values ​​of the permissible exposure times and / or values ​​of the opening angles of a lens shutter of the camera.

[0060] In particular, the permissible exposure times and / or a permissible exposure time can be displayed directly on the playback device, with integer multiples of these times also representing permissible exposure times. However, instead of an exposure time, for example for a rolling shutter, an opening angle of the lens shutter can also be displayed, whereby the respective opening angle can correspond to an angle whose fraction of 360° can correspond to a fraction of a permissible exposure time in relation to the camera's image acquisition time. Thus, for example, in the embodiment described above, with a light pulse frequency of 1920 Hz and an image acquisition frequency of 24 Hz, 80 light pulses per image acquisition can be generated, so that an opening angle of a lens shutter, corresponding to a permissible exposure time, can be defined by an integer multiple of 360° / 80 = 4.5°.

[0061] In some embodiments, the control unit can be connected to an input device configured to receive a user input specifying an exposure time and transmitting it to the control unit. The control unit can then be configured to set the exposure time on the camera. In particular, such an input device can also be connected to the camera's interface to transmit, for example, a user input specifying the light pulse frequency of the background playback device to the camera.

[0062] The input device may, for example, include a touchscreen and / or knobs or buttons to enable user input. The input device may also include, for example, a rotary dial to set an exposure time. In particular, the input device may interact with the aforementioned playback device, for example, by using a touchscreen to both display information about permissible exposure times and to receive user input.

[0063] In principle, the exposure time to be set can be any value and does not necessarily have to correspond to one of the specified permissible exposure times. The control unit can therefore be designed to set an exposure time for the camera, independently of any received light pulse frequency. However, the exposure time to be set for the camera can also be a selection of permissible exposure times, particularly if the permissible exposure times are displayed on the camera's playback device and the user selects one of these permissible exposure times.

[0064] In some embodiments, the control unit can further be configured to set the exposure time only if it is a permissible exposure time. In such embodiments, the user can therefore only choose between permissible exposure times, whereas the control unit can prevent the setting of an impermissible exposure time. In particular, this can be achieved by displaying only the specific permissible exposure times, especially taking into account their respective limits, on the playback device and offering them to the user for selection, so that the user can only set permissible exposure times anyway.This can also be achieved, for example, by making the exposure time on the camera adjustable in increments, whereby the steps can be automatically set to the reciprocal of the received light pulse frequency by means of the control device. For example, in some embodiments, a steplessly rotatable control wheel, particularly as part of the aforementioned input device, can be provided for setting the exposure time on the camera, whereby the steps can be automatically set to the respective permissible exposure times by the control device.

[0065] Furthermore, in some embodiments, the control unit can be configured to set one of the closest permissible exposure times to the exposure time to be set if the exposure time to be set is not a permissible exposure time. In such embodiments, the user can therefore, in principle, freely set an exposure time, while the control unit can, if necessary, adjust the exposure time to a permissible exposure time. This ensures that the image produced by the camera is generated with an exposure time approximately equal to the user's desired exposure time, while simultaneously guaranteeing that all areas or lines of a photosensitive element in the camera register a consistent number of light pulses during image capture.

[0066] In some embodiments, the control unit can be configured to automatically set a permissible exposure time depending on the light pulse frequency. For example, the control unit can be configured to automatically set a permissible exposure time closest to the currently set exposure time after receiving the light pulse frequency from the background playback device. This also ensures that a user-defined exposure time preset is taken into account, while simultaneously preventing unwanted modulations in the virtual background renderings caused by unequal numbers of light pulses received in different areas or lines of a photosensitive element.

[0067] The invention further relates to a background playback device for a virtual image recording studio, which is configured to display a representation of a virtual background behind a real subject for a photograph taken with an associated camera. The background playback device has a control unit configured to drive the background playback device to an intermittent display of the virtual background according to an adjustable light pulse frequency. Furthermore, the background playback device has an interface configured to receive a value of a set exposure time from the associated camera, and the control unit is configured to adjust the light pulse frequency of the background playback device depending on the received value of the set exposure time from the associated camera.

[0068] By adjusting the light pulse frequency via the background playback device's control unit, it is ultimately possible to synchronize the background playback device's light pulse frequency with the camera's exposure time. In this case, however, the camera's exposure time can be freely selected, as the necessary adjustment is ultimately made at the background playback device. The background playback device's interface can also be configured to receive the exposure time of the associated camera wirelessly or via a wired connection. Furthermore, the interface can be configured to receive the exposure time directly from the associated camera, or it can be configured to receive the camera's exposure time via user input.

[0069] The control unit of the background playback device is designed to adjust the light pulse frequency such that it corresponds to an integer multiple of the reciprocal of the received value of the set exposure time. This ensures that, during a camera exposure, each area and / or each line of a light-sensitive element of the camera, in particular a film or an image sensor, is exposed to the same number of light pulses, thus preventing any brightness modulations in the image of the virtual background produced by the camera.

[0070] In conjunction with such an adjustable background playback device, the associated camera may, in particular, have an electronic or mechanical rolling lens shutter, so that different areas or lines of a light-sensitive element of the camera can be exposed at different times. Furthermore, the camera may, in particular, have an image sensor with a plurality of light-sensitive sensor elements arranged in several rows and columns, wherein these rows can, in particular, be exposed row by row and successively for a respective, constant exposure time.

[0071] The control device can further be configured, in particular, to adjust the light pulse frequency such that the light pulse frequency corresponds to an integer multiple of the reciprocal of the received value of the set exposure time, greater than one. Furthermore, the control device can also be configured to take into account an upper limit and / or a lower limit of the adjustable light pulse frequency.

[0072] In some embodiments, the control unit of the background playback device may be configured to automatically adjust the light pulse frequency of the background playback device, or the control unit may be configured to transmit information about permissible light pulse frequencies to a user in order to select one of the permissible light pulse frequencies based on user input. For this purpose, the background playback device may also include, in particular, an input device and / or a playback device to transmit information to the user and / or receive user input. The playback device and / or the input device may, for example, be configured as a display and / or touchscreen.

[0073] In some embodiments, the background display device can comprise a plurality of actively illuminated pixel elements, in particular light-emitting diodes, forming a two-dimensional arrangement. Furthermore, the background display device can have the features already described above for a background display device for a virtual image capture studio.

[0074] Furthermore, a background playback device can be provided for a virtual image recording studio, which is designed to display a virtual background behind a real subject for a photograph taken with an associated camera. The background playback device has a control unit designed to change the display of the virtual background at adjustable update intervals. The background playback device also has an interface designed to receive information about exposure intervals between successive exposures from the associated camera. The control unit is designed to adjust the update intervals of the background playback device based on the received information about the exposure intervals from the associated camera.

[0075] In particular, the control unit of the background playback device can be configured to change the display of the virtual background at a predefined and / or adjustable update frequency. In this context, the control unit can be configured to modify the contained image information according to the display rendered by the background playback device when the display of the virtual background is changed or updated.

[0076] For example, information about exposure intervals between successive exposures of the assigned camera can include the exposure time and / or the frame rate of the assigned camera. The interface of the background playback device can also be configured to receive this information directly from the camera or via user input. Communication between the camera and the interface of the background playback device can be wireless or wired.

[0077] Furthermore, the information about the exposure pauses can include the start time of an exposure period and / or an exposure window within a camera image capture and / or the phase of the exposure period within a camera image capture period. During a camera capture, in which the camera generates images of the virtual background at a predetermined or adjustable frame rate, the exposure window can also be repeated periodically at the frame rate, with exposure pauses positioned between the exposure windows.By transmitting information about the start and duration of an exposure window, the exposure window can be temporally located within an image capture. This allows, for example, the display of the virtual background outside the exposure window to be changed at the background playback device by shifting the update times relative to the start and / or end of the exposure window. Specifically, the display of the virtual background can be modified by the background playback device's control unit at an update frequency that corresponds to the image acquisition frequency of the associated camera and / or an integer fraction of that frequency.This ensures that subsequent, periodically recurring update times also fall within exposure pauses of the assigned camera by shifting an update time once relative to an exposure window, in order to move this update time into an exposure pause.

[0078] To enable the transmission of information about the camera's exposure pauses to the background playback device, the background playback device and the camera can be linked, particularly in a network. Such a link can allow synchronization of the update points and exposure times via a suitable network protocol, such as PTP (Precision Time Protocol). For this purpose, the network can include, in addition to the camera and the background playback device, a timing device that can function as a reference clock (also known as a grandmaster clock). Alternatively, however, the timing device of either the camera or the background playback device can also serve as the reference clock in the network.To control the synchronization between the camera and the background playback device, a network control unit may be provided, which may, for example, include a microprocessor and be configured to determine corresponding delays between the time signals of the camera and / or the background playback device and the time signals of the reference clock, and to approximate the time signals of the camera and / or the background playback device to the time signals of the reference clock. Alternatively, the control unit of the background playback device and / or a control unit of the camera may also be configured to perform the synchronization between the time signals of the camera and the time signals of the background playback device.In particular, the control unit of the camera and the background playback unit can be configured to perform synchronization, which forms the reference clock in the network.

[0079] Furthermore, in some embodiments, the control unit of the background playback device can be configured to set the update times in such a way that a change in the display of the virtual background occurs during an exposure break of the associated camera.

[0080] As previously explained, this type of control of the background playback device ensures that the virtual background display does not change within a single exposure or exposure window of the associated camera, thus preventing two or more virtual background representations from being captured in a single image. Instead, this synchronization between the virtual background display update and the camera's exposure pauses ensures that an unchanged virtual background representation is displayed for the entire duration of an exposure, so that only a single virtual background representation is captured during each image acquisition.

[0081] In some embodiments, the received information about the exposure pauses of the associated camera can represent the start, or the start and duration, of at least one exposure pause. In particular, the information can represent the start, or the start and duration, of at least one single exposure pause or a series of successive exposure pauses. For example, the update points can be adjusted by means of the background playback control unit such that the display of the virtual background is changed immediately after the start of an exposure pause, and thus at a time when the subsequent exposure has not yet begun.When receiving information about the start and duration of the exposure break, it may also be necessary to place the update times in the middle of an exposure break in order to prevent possible imaging effects, for example due to a slight fluctuation in the update frequency.

[0082] In particular, the received information about exposure pauses can include information about the time of each exposure pause, or information about the frequency and phase of successive exposure pauses. The received information about exposure pauses can also include information about the duration of each exposure pause. Furthermore, the received information about exposure pauses can also include information about the frequency and phase of successive exposures, as well as information about the duration of each exposure, so that the times of successive exposure pauses can be indirectly determined.

[0083] In some embodiments, the background display device may comprise a plurality of actively illuminating pixel elements, in particular light-emitting diodes, forming a two-dimensional arrangement.

[0084] In particular, the pixel elements can be arranged in a planar configuration and / or a regular grid. Furthermore, the background display device can be designed as an LED and comprise a multitude of light-emitting diodes, in particular LEDs (Light Emitting Diodes) or organic light-emitting diodes (OLEDs).

[0085] In some embodiments, the background display unit can comprise several identical panels, each with a plurality of pixel elements arranged on it. Such panels can also be referred to as panels.

[0086] Furthermore, the background playback device can have the features of a background playback device for a virtual image recording studio, as explained above in connection with the synchronization of camera exposure times and light pulse frequencies of the background playback device.

[0087] In some embodiments, the control unit of the background playback device may further be connected to a memory in which at least one next representation of the virtual background is stored, wherein the control unit may be configured to reproduce the stored next representation in order to change the representation of the virtual background.

[0088] For example, the control unit can include a driver for controlling one or more actively illuminated pixel elements, which incorporates an internal buffer RAM. The memory and / or buffer RAM can thus form a shadow register into which a new image, or the next rendering of the virtual background, can be written while a previous rendering is still being displayed. The next rendering therefore does not need to be generated and transferred to the control unit via a long path, but can be changed directly and synchronously across the entire background rendering unit by essentially holding the respective next rendering in memory. In particular, this can enable rapid changes to the rendering of the virtual background, ensuring that the rendering can be reliably changed during an exposure pause of the associated camera.

[0089] Furthermore, a camera can be designed to capture a representation of a virtual background, which is displayed in a virtual image-capturing studio by means of an associated background playback device and changes at update times. The camera has an interface configured to receive information about the update times of the associated background playback device, and the camera has a control unit configured to control the camera according to an adjustable exposure time. The control unit is also configured to set exposure pauses for the camera depending on the received information about the update times.

[0090] The camera's exposure pauses can be adjusted directly or indirectly, particularly via the control unit. However, the camera's exposure pauses can also be adjusted—directly or indirectly—in such a way that the timing and duration of each exposure pause are defined and synchronized with the update times of the associated background playback device. To adjust the exposure pauses indirectly, the frequency and phase of successive exposure times and / or exposure windows, as well as the duration of each exposure time and / or exposure window, can be set.Exposure pauses can be repeated periodically, in particular with an adjustable image acquisition frequency, a frequency at which the camera generates images of the representation of the virtual background, whereby the respective time periods of the successive exposure pauses can be determined by the respective phase position of the exposure pause in relation to the start of an image acquisition.

[0091] Synchronization between exposure pauses and update times can also be achieved via a network encompassing the camera and the background playback device. Again, synchronization via PTP (Precision Time Protocol) can be used.

[0092] In some embodiments, the camera's control unit can be configured to adjust the camera's exposure pauses such that an exposure pause occurs during each change in the virtual background display. In such embodiments, the background playback device can therefore modify the virtual background display unaffected at the respective update time, and the camera's control unit can use the information about these update times to adjust the camera's exposure pauses accordingly. In particular, this can be achieved by a corresponding phase shift of an exposure window, during which a light-sensitive element of the camera is exposed, relative to the update times of the background playback device.The update times of the background playback device can be determined, in particular periodically, by an update frequency of the background playback device, while the exposure pauses can be determined by an image acquisition frequency of the camera. In particular, the image acquisition frequency and the update frequency can correspond to each other, and the camera's control unit can also be configured to adjust the image acquisition frequency such that it corresponds to the update frequency of the background playback device or to an integer multiple of the update frequency. For this purpose, the camera's interface can also be configured to receive the update frequency or information about the update frequency from the background playback device.

[0093] The invention will below be explained purely by way of example with reference to embodiments shown in the drawings.

[0094] They show: Fig. 1 a schematic representation of a recording system for an image recording studio with a background playback device for displaying a representation of a virtual background and with a camera, Fig. 2 a schematic representation of a camera intended for recording in the image recording studio, Fig. 3 a schematic representation of an image sensor of the camera, Figs. 4A and 4B are respective schematic representations to illustrate a line-by-line readout of the image sensor and a temporal superposition of the readout with light pulses generated by the background playback device for displaying the representation of the virtual background, Figs. 5A to 5 are respective schematic representations to illustrate a mechanical rolling lens shutter, Fig.Figures 6A and 6Beine are a schematic representation illustrating the temporal sequence for changing the virtual background display and a tearing effect in a camera-generated image of the virtual background, and Figures 7A and 7Beine are a schematic representation illustrating the temporal synchronization of camera exposure pauses with update times of the background playback device for changing the virtual background display.

[0095] Fig. 1 Figure 1 schematically shows a virtual image recording studio 13 in which a scene, particularly in the form of a moving image recording and / or a photograph, can be recorded using an associated camera 23. The camera 23 can, for example, be configured as a video camera to capture moving images that can be stored as a sequence of images generated by the camera 23. For this purpose, the camera 23 has a lens 59, which can be configured as an interchangeable lens that can be optionally attached to a housing of the camera 23. This allows the use of a lens 59 that is optimally adapted to the environment in the image recording studio 13 in order to create the best possible recordings.In the housing of the camera 23, in particular an image sensor 53 with several light-sensitive sensor elements 55 can be arranged, onto which light entering through an aperture of a diaphragm can be directed by means of a lens system or at least one lens to produce an image 73 (see also . Fig. 2 and 7B ).

[0096] Furthermore, a background display system 11 with a background display device 15 is arranged in the image recording studio 13, which together with the camera 23 forms a recording system 10. The background display device 15 comprises an active lighting device 31 designed as an LED wall 33 and is configured to display a representation 19 of a virtual background 21 for recording with the camera 23. For this purpose, the lighting device 31 or the LED wall 33 has a plurality of actively illuminated pixel elements 35, which are arranged next to each other in a two-dimensional arrangement. For example, the pixel elements 35 can be designed as individually controllable LEDs 44 or as individually controllable LED units, each of which can comprise several, in particular three, LEDs 44.In particular, the pixel elements 35 may be configured as light-emitting diode (LED) units, each with three LEDs 44, wherein one of the three LEDs 44 can emit red light, one LED 44 green light, and one LED 44 blue light. The LED unit may also include a color mixer to allow the color and / or brightness emitted by each pixel element 35 to be adjusted by individually controlling the LEDs 44 within the LED unit. The LEDs 44 may, for example, be configured as LEDs or as organic light-emitting diodes (OLEDs). Background playback devices may also be used in the image capture studio 13 to display a virtual background, generating the display by means of rear projection.

[0097] The background display unit 15 comprises a plurality of panels 41, which can also be referred to as panels. Each panel 41 of the plurality of panels 41 has a plurality of actively illuminated pixel elements 35 arranged on it, so that a section of the representation 19 of the virtual background 21 can be displayed on each panel 41. The panels 41 are, in particular, rectangular and / or square and borderless, so that the representation 19 of the virtual background 21 can also be displayed at the transitions between panels 41 without visible interruptions. The panels 41 are furthermore arranged in a two-dimensional matrix to form the background display unit 15.

[0098] The representation 19 of the virtual background 21 here exemplifies a three-dimensional scene 43 with objects 91, 92, 93, and 94, three trees, and a path, which can be generated by appropriately controlling the pixel elements 35, in particular by appropriately adjusting their respective color and brightness. The three-dimensional scene 43 is projected onto the essentially two-dimensional arrangement of the pixel elements 35 of the lighting device 31, whereby, in particular, the objects 91, 92, and 93 appear at different distances from the lighting device 31 or the background display device 11 in order to replicate the three-dimensionality of a real background corresponding to the virtual background 21.

[0099] In particular, the display 19 of the virtual background 21 by means of the background playback device 15 serves to create a background for a recording of a real subject 17, for example, an actor, in front of which a recording can be made or a film scene can be performed. This allows, in principle, any landscapes, rooms, or environments to be created in the image recording studio 13, in front of or within which a scene, for example, for a feature film, is to be filmed. Furthermore, it is possible to display movements in the virtual background 21, for example, a passing car, by controlling the pixel elements 35 over time, to which the actor 17 can react more easily and effectively compared to acting in front of a green screen.

[0100] The background display device 15 extends essentially vertically, allowing the actor 17 to move in front of the virtual background 21. However, to display the virtual background 21 more comprehensively, the background display device 15 can also extend around or above the actor 17, and in particular, the background display device 15 can have a horizontal orientation above the actor 17. To surround the actor 17 or to create a transition from the shown vertical orientation to a horizontal orientation, the background display device 15, the lighting device 31, or the LED wall 33 can also be curved or arched, at least in sections.

[0101] In addition to displaying the virtual background 21, the background playback device 15 can also be used to illuminate the real subject 17, thereby, for example, supporting additional studio lighting in the image-capturing studio 13. Furthermore, by illuminating the real subject 17 using the background playback device 15, the interaction of the real subject 17 or the actor 17 with light sources present in the virtual background 21, such as lanterns or lamps, can be improved by the real subject 17 casting a shadow that corresponds to the lighting conditions visible in an image produced by the camera 23.

[0102] In order to generate the representation 19 of the virtual background 21 and to control the pixel elements 35 for displaying the representation, the background display device 15 has a control unit 37 (e.g., a microprocessor or central processing unit, CPU) which is connected to a memory 39. In particular, a model of the virtual background 21 can be stored in the memory 39, so that the control unit 37 can generate the virtual background 21 based on the model. Furthermore, the control unit 37 can be configured to project the virtual background 21 onto the background display device 15 and, in particular, the two-dimensional arrangement of the pixel elements 35.

[0103] Furthermore, in order to enable the background playback device 15 to reproduce time-changing representations 19 of the virtual background 21 as directly as possible and without time loss, at least one subsequent representation 19b can be stored in the memory 39, wherein the control device 37 can be configured to reproduce the subsequent representation 19b stored in the memory 37 in order to change the representation 19 of the virtual background 21 (see also Fig. 6B In particular, the next representation 19b does not need to be generated only when playback is to take place; instead, the control unit 37 can directly control the pixel elements 35 to display the next representation 19b. For example, the control unit 37 can be configured to generate the next representation 19b of the virtual background 21 during the playback of a representation 19, based on the model stored in the memory 39, and write it to the memory 39 in order to be able to access the next representation 19b immediately when playback is required.

[0104] Furthermore, to enable communication between the components of the recording system 10, the background playback device 15 has an interface 103 through which information I can be received from the associated camera 23. This information I can, for example, be transmitted directly from the camera 23 via a wireless and / or wired connection or entered by a user at the interface 103. In particular, information I about an exposure time E and / or an exposure interval Q between two exposures of the associated camera 23 can be transmitted to the background playback device 15 via the interface 103, as explained in more detail below.

[0105] One possible configuration of the assigned camera is in Fig. 2 The camera 23 is shown schematically. It has a camera body 53 to which a lens 59 is attached. The lens 59 can be designed as an interchangeable lens, allowing different lenses 59 to be attached to the camera body 53 and ensuring that the optimal lens 59 is always selected for each shot. The lens 59 has three lens rings 81, by means of which various parameters of the lens 59 can be adjusted. For example, the focus distance, focal length, zoom factor, and / or aperture, in particular the opening of an iris diaphragm, can be adjusted by rotating one of the lens rings 81. The camera 23 can be designed as a motion picture camera or video camera to produce a successive sequence of images 73, which can, for example, be played back as a film.

[0106] To adjust the lens rings 81, a lens ring drive unit 85 is connected to the camera body 53 via a support rod 87. This unit has a separate lens adjustment motor 83 for each of the lens rings 81. These lens adjustment motors 83 allow the lens rings 81 to be rotated, thereby enabling adjustments to the lens 59. In particular, the lens ring drive unit 85 can be operated remotely, allowing the aforementioned lens parameters to be set or changed remotely.

[0107] A further playback device 49 is arranged on the camera body 53, via which information I about the camera 23 settings can be displayed to a user. The playback device 49 can, in particular, be a display. The camera 23 also has an input device 51 arranged on the camera body 53, via which the user can make settings of the camera 23. In particular, an exposure time E of the camera 23 can be set via the input device 51, and a control device 25 connected to the input device 51 can be configured to control the camera 23 according to the entered exposure time E. In particular, the playback device 49 and the input device 51 can be formed by a touchscreen, via which information I can be displayed to the user and user input can be received.

[0108] To image the light arriving through the lens 59, the camera 23 further comprises an image sensor 1 arranged within the camera body 53. This image sensor 1 can, for example, be based on CMOS or CCD technology and have a plurality of light-sensitive sensor elements 55, which can be arranged in several rows 14 and columns 16 (see also Fig. 3 Furthermore, the camera 23 has a readout circuit 97, which is configured to read, process, digitize, and output the signals from the respective sensor elements 55 to or via a signal output 99. For this purpose, the readout circuit 97 can, in particular, include amplifiers, multiplexers, analog-to-digital converters, buffer memory, and / or microcontrollers. Ultimately, the camera 23 can thus generate an image data set B, which corresponds to the image or a representation of a field of view of the camera 23, and the image data set B can be output via the signal output 99. In order to check the field of view of the camera 23 and to be able to align the camera 23 with a respective image section, a viewfinder 79 is also arranged on the camera body 53, through which a camera operator can look.

[0109] Furthermore, the camera 23 has an interface 101 for receiving information I and / or data from the background playback device 15, whereby wireless and / or wired communication or user input may be provided. In particular, the received information I may include update times 61, at which the background playback device 15 changes the display 21 of the virtual background 21, or a light pulse frequency P of the background playback device 15, according to which the background playback device 15 intermittently displays the display 19 of the virtual background 21. This is also explained in more detail below.

[0110] Fig. 3 Figure 1 shows an exemplary representation of the image sensor 1 of the camera 23. The image sensor 1 has a plurality of pixels 54 arranged in rows 14 and columns 16, each pixel 54 forming a light-sensitive sensor element 55 to convert incident light into electrical charge during an exposure (see Figure 1). Fig. 3 The reading of such an image sensor 1 can, for example, be performed row by row, for which a row addressing logic 3 is provided. The sensor elements 55 of a row 12 can be coupled via a row selection line 6 to a respective column line 18, which is assigned to the pixels 54 arranged in a column 16. Via the column lines 18, the signals of the light-sensitive sensor elements 55 of a row 14 can be transmitted to a column amplifier 4, by means of which the generated signals can be amplified and then further processed, in particular digitized.

[0111] The time sequence with respect to a time t of such a line-by-line readout of the image sensor 1 is described in the lower section of Fig. 4A The image sensor is read out as follows: First, in a first row 14a of the image sensor 1, the charges of the light-sensitive sensor elements 55 are reset or cleared in a step R. This ensures that only light incident on the sensor elements 55 during a defined exposure time E is included in the image data set B output by the camera 23. After the sensor elements 55 have been reset, the sensor elements 55 arranged in row 14a are exposed for the exposure time E. In the subsequent step S, an electrical charge is generated on the sensor elements 55 depending on the amount of light incident on them during the exposure time E.After the defined exposure time E, a step C follows in the initially addressed line 14a, in which the electrical charges generated on the sensor elements 55 of line 14a during the exposure time E are read out. For this purpose, line 14 can be coupled with the column line 18 (see also ). Fig. 3 ).

[0112] To minimize the readout time for image sensor 1, the sensor elements 55 arranged in the following row 14b are reset in step R while charge is still being generated on the sensor elements 55 of row 14a. The reset R of row 14b is synchronized with the exposure time E such that the reset R of the sensor elements 55 in row 14b is completed precisely when step S for generating the electrical charge is finished for the sensor elements 55 of row 14a. This allows the sensor elements 55 of row 14b to be exposed, again for exposure time E, as soon as the readout C of the generated electrical charge begins for the sensor elements 55 of row 14a, and the sensor elements 55 of row 14b to be read out after exposure time E by coupling them to the column line 18.These steps R, S and C for reading the image sensor 1 are then described in the following lines 14c, 14d and 14e as well as the further ones in . Fig. 4 The process of successively processing the unshown lines 14 of the image sensor 1 was carried out in order to finally generate a figure 73 of the representation 19 of the virtual background 21 or an image data set B.

[0113] Due to this line-by-line readout of the image sensor 1, the camera 23 is operated with an electronic rolling shutter 27, since the individual lines 14a, 14b, 14c, 14d, and 14e are exposed at different times, and the respective exposure times E of the individual lines 14a, 14b, 14c, 14d, and 14e are shifted relative to each other by the exposure time E. In particular, when the camera 23 is used to create moving image recordings, such an electronic rolling shutter 27 can be provided in order to depict a natural sequence of motion in images 73 generated by the camera 23 or in a sequence of such images 73. In such a rolling lens shutter 27, in addition to the exposure time E with which the individual lines 14a, 14b, 14c, 14d and 14e are exposed, an exposure window W can also be assigned to the image sensor 1, which specifies the duration orThe time interval is defined from the start time of the exposure of a first sensor element 55 or the first row 14a to an end time of the exposure of a last sensor element 55 or a last row 14 of the image sensor. The exposure window W of the image sensor 1 is thus defined in the Fig. 4A The electronic rolling lens shutter 27 shown is longer than the exposure time E.

[0114] In the upper section of the Fig. 4A It is further illustrated that the control unit 37 of the background playback device 15 can be configured to control the background playback device 15 to an intermittent playback of the representation 19 of the virtual background 21 according to an adjustable light pulse frequency P. In this respect, the representation 19 can be displayed in a pulsating manner, whereby a plurality of light pulses 65 can be displayed during each exposure time E, such that a light pulse duration L of the individual light pulses 65 can be less than the exposure time E of the lines 14 of the image sensor 1. The light pulse frequency P can also be synchronized, in particular, with an image acquisition frequency F of the camera 23, in that the light pulse frequency P can correspond to a multiple of the image acquisition frequency F (see also Fig. 6A and 7AThe image acquisition frequency F of camera 23 can also be referred to as the frame rate and indicates how many images the assigned camera 23 produces per second. For example, with a common image acquisition frequency of 24 fps or 24 Hz, the light pulse frequency P may be 1920 Hz or 3840 Hz.

[0115] While the light pulse frequency P can be synchronized with the image acquisition frequency F of camera 23, the exposure time E of camera 23 is fundamentally freely selectable and is not directly determined by the image acquisition frequency F or an image acquisition time D that corresponds to the reciprocal of the image acquisition frequency F. Accordingly, even if the light pulse frequency P and the image acquisition frequency F are matched, there is fundamentally no direct synchronization between the exposure time E and the light pulse frequency P. However, this can be, as Fig. 4A This illustrates that, particularly in the case of a rolling shutter 27, each of the lines 14a, 14b, 14c, 14d, and 14e of the image sensor 1 registers a different number of light pulses 65 or different proportions of incomplete light pulses 65 during the respective exposure time E. The lines 14a, 14b, 14c, 14d, and 14e of the image sensor 1 can thus be exposed to different degrees by the background display device 15, so that undesired brightness modulations can appear in Figure 73 of the virtual background 21 generated by the camera 23, for example, different lines of Figure 73 may exhibit different brightness levels due to the different number of detected light pulses 65.

[0116] The same problem can also arise in principle with a camera 23 with a mechanical rolling lens shutter 27, as shown by the Fig. 5A bis 5D This is illustrated. In such a mechanical rolling lens shutter 27, an opening 28 can be provided which is successively moved over a light-sensitive element 29 of the camera 23, for example an image sensor or film, so that different areas 30 and 30a of the light-sensitive element 29 are exposed to light at different times by the opening 28. Fig. 5A The light-sensitive element 29 is completely covered by the lens shutter 27, while the lens shutter 27 is in Fig. 5B has already been moved far enough along the direction of arrow 105 that a first area 30 of the light-sensitive element 29 can be exposed. In Fig. 5C The entire light-sensitive element 29 is arranged in line with the opening 28, so that the entire light-sensitive element 29 is exposed to light. Fig. 5D If, however, the lens shutter 27 is moved further, the first area 30 is already covered by the shutter 27, whereas a final area 30a of the light-sensitive element 29 can still be exposed. Thus, even with such a mechanical rolling lens shutter 27, areas 30 and 30a are exposed for the same exposure time E, but at different times. Therefore, the modulation described above can also occur in an image 73 produced by the camera 23, due to different numbers of registered light pulses 65 or different proportions of incompletely registered light pulses 65 in areas 30 and 30a.

[0117] To address this problem, it may be possible, in particular, to adjust the exposure time E of the camera 23 as a function of the light pulse frequency P of the background playback device 15, or the light pulse frequency P of the background playback device 15 as a function of the exposure time E of the camera 23, such that the exposure time E corresponds to an integer multiple of the reciprocal of the light pulse frequency P. In particular, the exposure time E can be adjusted such that the exposure time E corresponds to an integer multiple of a light pulse duration L, where this integer multiple may, in particular, be greater than one. This can be determined based on the Fig. 4B illustrated.

[0118] How Fig. 4B As shown, by adjusting the exposure time E in this way, it can be achieved that during each exposure time E an integer number of complete light pulses 65 is registered, which can in particular be greater than one. In the illustration shown, the synchronization between the exposure time E or the respective starting points of the exposure in lines 14a, 14b, 14c, 14d and 14e and the light pulses 65 is chosen such that the sensor elements 55 of each line 14 of the image sensor 1 register an integer number of always complete light pulses 65.Even if the start of the exposure time E is shifted relative to the start of a light pulse 65, meaning that part of the first light pulse 65 registered in a line 14 is truncated, the exposure time E can be chosen to be an integer multiple of the reciprocal of the light pulse frequency P. This ensures that precisely the part of a light pulse 65 truncated at the beginning of the exposure time E is still registered at the end of the exposure time E in the respective line 14 and, accordingly, in each of the lines 14 of the image sensor 1. Therefore, by choosing the exposure time E in this way, it can be ensured that the same number of complete light pulses 65 are registered in each line 14 of the image sensor 1, and the modulations described above in Figure 73, which the camera 23 generates from the representation 19 of the virtual background 21, can be avoided.

[0119] As mentioned above, to enable such an adjustment of the exposure time E and / or the light pulse frequency P, the camera 23 can have an interface 101 for receiving information I from the background playback device 15. Furthermore, the background playback device 15 can have an interface 103 for receiving information I from the camera 23. For example, the control unit 25 of the camera 23 can be configured to determine several permissible exposure times E depending on a received value of the light pulse frequency P. In this respect, the light pulse frequency P can be transmitted to the control unit 25 of the camera 23 via the interface 101 and the information I, for example, directly through communication with the background playback device 15 or through user input.The control device 25 can then be configured to determine the permissible exposure times E as exposure times E that correspond to an integer multiple of the reciprocal of the light pulse frequency P or an integer multiple of the light pulse duration L. For this purpose, the control device 25 can, for example, be configured to calculate the permissible exposure times E or to look them up in a memory 47 to which the control device 25 is connected. As already explained, for such permissible exposure times E, it can be ensured that the same number of light pulses 65 are registered in each line 14 of the image sensor 1 or in each area 30 or 30a of a light-sensitive element 29. Thus, for example, at an image acquisition rate of 24 fps or 24 fps, the following results:24 Hz and a light pulse frequency P of 1920 Hz, a total of 80 light pulses 65 per recorded image are generated by the background playback device 15, so that in this case 80 permissible exposure times E with a respective duration of nx 1 / 1920 Hz, where n equals 1 to 80, can be determined.

[0120] To set a permissible exposure time determined in this way on the camera 23, the control unit 25 of the camera 23 can, for example, be configured to automatically set a permissible exposure time E. For instance, the control unit 25 can set the permissible exposure time E that is closest to a currently set exposure time E. Furthermore, the control unit 25 can also be configured to display the determined permissible exposure times E on the playback unit 49 of the camera 23, so that a user can select one of the permissible exposure times E, in particular by means of the input unit 51, and transmit it to the control unit 25. The control unit 25 can then set the permissible exposure time E on the camera 23.The control unit 25 can also be configured to set an exposure time E set by a user at the input unit 51 only if this set exposure time E corresponds to a permissible exposure time E. Otherwise, the control unit 25 can, for example, set the permissible exposure time E that is closest to the exposure time E set by the user. It can also be provided that, after permissible exposure times E have been determined using the input unit 51, only permissible exposure times E can be set at the input unit 51. For this purpose, a grid of permissible exposure times E can, for example, be displayed on the playback unit 49, from which the user can select via the input unit 51.It may also be provided that exposure times E can be set stepwise by means of the input device 51, whereby the control device 25 may be designed to set the steps to permissible exposure times E.

[0121] As an alternative to setting the exposure time E on the camera 23, the control unit 37 of the background playback unit 15 can also receive information I about the exposure time E of the camera 23 via the interface 103 and adjust the light pulse frequency P depending on the value of the received exposure E set on the camera 23. The control unit 37 of the background playback unit 15 is configured to adjust the light pulse frequency P such that the light pulse frequency P corresponds to an integer multiple of the reciprocal of the received value of the set exposure time E. Such an adjustment of the light pulse frequency P can also ensure that an integer number of light pulses 65 are ultimately registered in each of the lines 14 of the image sensor 1 of the camera 23 during the set exposure time E.Adjusting the light pulse frequency P at the background playback device 15 also allows a camera operator to freely and without restriction set the exposure time E at the camera 23, for example, using the input device 51. By adjusting the light pulse frequency P at the background playback device 15, it can be ensured that, at the set exposure time E, each line 14 of an image sensor 1 or each area 30 or 30a of a light-sensitive element 29 of the camera 23 registers the same number of light pulses 65 during an exposure. The setting of the light pulse frequency P can be automatic, or various permissible light pulse frequencies can be displayed to allow a user to set a permissible light pulse frequency.

[0122] Another problem regarding the synchronization between the background playback device 15 and the camera 23 can arise from the fact that the background playback device 15 may be configured to display changing representations 19 of the virtual background 21. For example, the control unit 37 of the background playback device 15 may be configured to change the representation 19 with a predefined or adjustable update frequency A in order to, for example, display movements in the virtual background 21. For this purpose, the representation 19 can be, as Fig. 6A illustrated, are changed at the respective update times 61. Again, the update frequency A can be synchronized with the image acquisition frequency F of the camera 23, so that in principle each image 73, which the camera 23 generates from the representation 19 of the virtual background 21, can be assigned a respective representation 19 of the virtual background 21.

[0123] However, the problem arises here as well that the exposure window W of camera 23 mentioned above, i.e., a time window during which at least one area 30 or 30a of a light-sensitive element 29 or a line 14 of an image sensor 1 is exposed to light, is determined by the set exposure time E and is not fundamentally linked to the image acquisition frequency F or the image acquisition duration D. Therefore, even if the update frequency A of the background playback device 15 is synchronized with the image acquisition frequency F of camera 23, a so-called tearing effect can occur in the images 73 of the background playback device 15 generated by camera 23 if the update times 61 fall within the exposure window B of the image sensor 1 or the light-sensitive element 29, for example, of film, of camera 23.

[0124] How Fig. 6B As shown, such a tearing effect can manifest itself in particular in the fact that in the image 73 generated by the camera 23, a first representation 19a of the virtual background 21 is depicted in a first area 73a, while after a change 63 of the representation 19 of the virtual background 21 falling within the exposure window W, the subsequent representation 19b of the virtual background 21 is already depicted in an area 73b of the image 73, with representation 19b being shown here shifted relative to representation 19a for illustrative purposes. The image 73 can thus be perceived as being torn into areas 73a and 73b.

[0125] To avoid this effect as well, it may be possible to adjust the exposure pauses Q of camera 23 depending on the update times 61 of the background playback device 15, or vice versa, such that a change 63 in the display 19 of the virtual background 21 occurs during an exposure pause Q of camera 23. This can be achieved by means of Fig. 7A illustrated.

[0126] In particular, the interface 103 of the background playback device 15 may be configured to receive information I about the exposure pauses Q from the camera 23, and the control unit 37 of the background playback device 15 may be configured to set the update times 61 depending on the received information I about the exposure pauses Q of the associated camera 23, and in particular to set them such that the update times 61 are located within the exposure pauses Q. For this purpose, the information I about the exposure pauses Q may, for example, represent the start or the start and duration of at least one exposure pause Q.Therefore, the information I can, for example, include a specific time of each exposure pause Q and / or the image acquisition rate F, so that subsequent exposure pauses Q can be determined based on the time of the first exposure pause Q. Furthermore, the information I can include the phase of the exposure pause Q and the image acquisition rate F, so that the temporal position of successive exposure pauses Q, which can also be repeated at the image acquisition rate F, can be determined. Additionally, the information I can include information about the exposure time E and / or the duration of the exposure window W, in order to determine the exposure pause Q as a time window between two successive exposure windows W.By allowing the control unit 37 to shift the update times 61, as it were, into the exposure pauses Q of the camera 23, a tearing effect in the image 73 produced by the camera 23 can be avoided, and it can be ensured that all lines 14 of the image sensor 1 or all areas 30a and 30b of the light-sensitive element 29 of the camera 23 register the same representation 19 (cf. . Fig. 7B ).

[0127] As an alternative to setting the update times 61 at the background playback device 15, the interface 101 of the camera 23 can also be configured to receive information I about the update times 61 of the background playback device 15. Accordingly, the control unit 25 of the camera 23 can be configured to set the exposure pauses Q of the camera 23 depending on the received information I about the update times 61. For example, the control unit 25 of the camera 23 can be configured to determine the phase of the exposure pauses Q within the image acquisition time D such that the exposure pause Q overlaps with the update time 61.By synchronizing the image acquisition frequency F of the camera 23 and the update frequency A of the background playback device 15, it can be ensured that all update times 61 of the background playback device 15 coincide with the respective exposure pauses Q of the camera 23. Accordingly, a tearing effect can also be avoided by controlling the camera 23 in this way.

[0128] To achieve reliable synchronization between the timing control of the background playback device 15 and the exposure times E of the camera 23, it may be possible, in particular, to link the camera 23 and the background playback device 15 via a network. Such a link can, for example, make it possible to synchronize the time signals of the camera 23 and the background playback device 15 via a suitable network protocol, such as PTP (Precision Time Protocol), in order to reliably align the update times A of the background playback device 15 with the exposure pauses Q of the camera 23. Bezugszeichenliste

[0129] 1 Image sensor 3 Row addressing logic 4 Column amplifier 6 Row selection line 10 Recording system 11 Background playback system 13 Image recording studio 14 Row 15 Background playback device 16 Column 17 Real subject, actor 18 Column line 19 Display 19a Display 19b Display 21 Virtual background 23 Camera 25 Control device 27 Rolling lens shutter 28 Aperture 29 Light-sensitive element 30 Area 30a Area 31 Lighting device 33 LED wall 35 Pixel element 37 Control device 39 Memory 41 Panel 43 Three-dimensional scene 44 Light-emitting diode 47 Memory 49 Playback device 51 Input device 53 Camera body 54 Pixel 55 Light-sensitive sensor element 59 Camera lensInterchangeable lens 61 Update time 63 Change of display 65 Light pulse 73 Image 73a Area of ​​the image 73b Area of ​​the image 79 Viewfinder 81 Lens ring 83 Lens actuator 85 Lens ring drive unit 87 Support rod 91 First object 92 Second object 93 Third object 94 Fourth object 97 Readout circuit 99 Signal output 101 Interface 103 Interface 105 Arrow A Update frequency B Image data set C Readout D Image capture time E Exposure time F Image capture frequency I Information P Light pulse frequency L Light pulse duration W Exposure window Q Exposure pause S Expose t Time R Reset

Claims

1. A camera (23) for a recording of a representation (19) of a virtual background (21) that is intermittently displayed in a virtual image recording studio (13) on an associated background display device (15) in accordance with a light pulse frequency (P), wherein the camera (23) comprises an interface (101) for receiving a value of the light pulse frequency (P) of the associated background display device (15) and a control device (25), wherein the control device (25) is configured to control the camera (23) in accordance with a settable exposure time (E), and wherein the control device (25) is configured to determine a plurality of permitted exposure times (E) in dependence on the received value of the light pulse frequency (P), wherein the control device (25) is configured to determine the permitted exposure times (E) such that the permitted exposure times (E) correspond to an integer multiple of the reciprocal of the light pulse frequency (P).

2. A camera (23) according to claim 1, wherein the camera (23) has an electronic rolling lens shutter or a mechanical rolling lens shutter (27).

3. A camera (23) according to claim 1 or claim 2, wherein the camera (23) has an image sensor (1) comprising a plurality of light-sensitive sensor elements (55).

4. A camera (23) according to any one of the preceding claims, wherein the control device (25) is configured to determine the plurality of permitted exposure times (E) such that the permitted exposure times (E) lie within a predetermined permitted range.

5. A camera (23) according to any one of the preceding claims, wherein the control device (25) is configured to determine the permitted exposure times (E) computationally or by looking up in a table.

6. A camera (23) according to any one of the preceding claims, wherein the camera (23) has a display device (49) for transmitting information (I) to a user and is configured to display information (I) about the determined permitted exposure times (E) on the display device (49).

7. A camera (23) according to claim 6, wherein the information (I) represents values of the permitted exposure times (E) and / or values of opening angles of a lens shutter (27) of the camera (23).

8. A camera (23) according to any one of the preceding claims, wherein the control device (25) is connected to an input device (51) which is configured to receive, through a user input, an exposure time (E) to be set and to transmit the latter to the control device (25), wherein the control device (25) is configured to set the exposure time (E) to be set at the camera (23).

9. A camera (23) according to claim 8, wherein the control device (25) is configured to set the exposure time (E) to be set only when the exposure time (E) to be set is a permitted exposure time (E).

10. A camera (23) according to claim 8 or claim 9, wherein the control device (25) is configured to set a permitted exposure time (E) which is closest to the exposure time (E) to be set when the exposure time (E) to be set is not a permitted exposure time (E).

11. A camera (23) according to any one of the preceding claims, wherein the control device (25) is configured to automatically set a permitted exposure time (E) in dependence on the light pulse frequency (P).

12. A background display device (15) for a virtual image recording studio (13) that is configured to display, behind a real subject (17), a representation (19) of a virtual background (21) for a recording by means of an associated camera (23), wherein the background display device (15) has a control device (37) which is configured to control the background display device (15) to intermittently display the representation (19) of the virtual background (21) in accordance with a settable light pulse frequency (P), wherein the background display device (15) has an interface (103) which is configured to receive a value of a set exposure time (E) of the associated camera (23), and wherein the control device (37) is configured to set the light pulse frequency (P) of the background display device (15) in dependence on the received value of the set exposure time (E) of the associated camera (23), wherein the control device (37) is configured to set the light pulse frequency (P) such that the light pulse frequency (P) corresponds to an integer multiple of the reciprocal of the received value of the set exposure time (E).

13. A method of displaying a representation (19) of a virtual background (21) by means of a background display device (15), in particular a background display device (15) according to claim 12, for a recording by a camera (23), in particular a camera (23) according to any one of the claims 1 to 11, in a virtual image recording studio (13), wherein the representation (19) is intermittently displayed in accordance with a light pulse frequency (P) and is intermittently recorded in accordance with an exposure time (E) of the camera (23), comprising the step: setting the exposure time (E) of the camera (23) in dependence on the light pulse frequency (P) of the background display device (15) or setting the light pulse frequency (P) of the background display device (15) in dependence on the exposure time (E) of the camera (23) such that the exposure time (E) corresponds to an integer multiple of the reciprocal of the light pulse frequency (P).