Beam splitter system for the film industry

Abstract

The beam splitter system (1) consists of a receiving lens (3), at least two cameras (12, 12') and a relay unit (2) with at least one beam splitter element (7), a first relay optic (6) and at least two second relay optics (8, 8a). The receiving lens (3) provides a real aerial image (4) which is imaged by the first relay optic (6), wherein the at least one beam splitter element (7) divides the imaging beam path (9) of the first relay optic (6) into at least two imaging paths (10, 10a), and the at least two second relay optics (8, 8a) image the aerial image (4) in the at least two second imaging paths (10, 10a) each onto a sensor (11, 11a) of the at least two cameras (12, 12a), and the beam splitter system (1) further comprises a device which is configured to selectively modify the image (4) to be imaged in at least one of the at least two imaging paths (10, 10a).

Description

TECHNICAL FIELDThe invention relates to a beam splitter system for the film industry. In particular, the invention relates to a beam splitter system having the features of claim 1.PRIOR ARTIn the media industry, it is becoming increasingly important to provide evaluations with different parameters from one and the same movie project. This can relate firstly to the frame rate, that is to say the number of images recorded per second, but also the aspect ratio of a movie, to name just two examples.Thus, motion pictures have a frame rate of 24 pictures per second, while television production runs in Europe at 25 pictures / s and in the USA 30 pictures / s are common. Image rates of 60 images / s are usually used for the Internet. These different image rates are usually adjusted by periodic repetition of images starting from a single sequence of moving images, by digital interpolation or by changing the playback speed. Such conversions are often associated with disturbing quality losses, however, or can be very complicated, as in the case of interpolation.Conventional films also usually have a horizontal orientation, i.e. the horizontal edge of the picture window is longer than the vertical. Common aspect ratios are often 16:9, 4:3 or 2.4:1. vertical aspect ratios are required predominantly for social media evaluations, often in an aspect ratio of 9:16.In order to implement this required aspect ratio, a vertical image section is usually determined from the horizontal recorded image and cut accordingly laterally. The disadvantage here is that a considerable trimming is necessary for a vertical orientation. In addition, a section that is too narrow to represent a scene in an comprehensible manner is often specified by a pure image trimming at 9:16. It is therefore advantageous if the vertical aspect ratio is formed not only from a partial region of the origin image with horizontal orientation, but can itself have an image height which is greater than the image height of the horizontally oriented output image.An obvious solution would be to place two cameras with identical recording lenses next to one another, wherein one is rotated through 90° about the optical axis and thereby create two recordings with the required parameters or to let the cameras positioned next to one another run with different image rates if an evaluation with different image rates is required. However, a disadvantage here is that professional film cameras usually have a width of 15 cm or more and the lateral offset caused in this way is too large. For example, this would mean that a performer is looking into the lens of one camera during a close-up while he is looking laterally past the other camera.Currently, such requirements, especially when different image rates or different exposure times are required, are often implemented with stereoscopic mirror systems in which two cameras with identical objectives are used, one camera filming into a semi-transparent splitter mirror and the other through it. By using a beam splitter mirror and the adjustment options of such a rig, in particular the possibility of determining the lateral offset of the two cameras, it is possible to reduce this offset completely to zero and to record two completely identical images with both cameras. If the frame rate, the exposure time, the aspect ratio or other parameters are now changed on one of the two cameras, recordings with the requirements listed above can be realized. Stereoscopic mirror systems, however, are complicated to operate, require specialists, are costly to obtain and contain a large number of possible sources of error.WO 01 / 86348 A1 discloses a multiplexed camera which divides an imaging beam by means of relay optics and beam splitters and passes it to up to four cameras. The cameras run in synchronization with one another in order then to generate new image sequences from the individual recordings, which are generated predominantly by the interlace of the individual images of the respective cameras. In practice, however, it is often necessary to set significantly more parameters in a very differentiated manner in addition to the image rate, exposure time and focus presented here in order to obtain the currently desired recording variants.U.S. Pat. No. 5,900,942 A presents a multi-spectral image system with which multi-spectral recording variants of a scene can be produced. In this case, an intermediate image is divided by means of relay optics, beam splitters and filters in such a way that different spectral ranges of the same output image are made available to the sensors of different cameras.DE 10 2012 005 939 A1 achieves different imaging variants by a beam splitter element, which is introduced into the beam path of a zoom lens and forwards the light to two sensors, in particular in order to achieve different polarization variants of the two recordings. Such an embodiment works without intermediate imaging and does not allow the use of interchangeable lenses.U.S. Pat. No. 8,320,047 B2 presents a system which splits the beam of an objective into a plurality of image sensors at different light intensities.The object of the invention is therefore to provide at least two independent cameras or camera sensors with the image circle of a scene with an identical point of view, wherein at least one of the images to be imaged on the at least two sensors is modified.This object is achieved by the beam splitter system according to claim 1, which is designed to image an image or an image sequence (film sequence) of a scene with an identical viewpoint on the sensors of at least two cameras and to thereby selectively modify the images to be imaged on the sensors of the at least two cameras with respect to one another. The image modification can be effected directly in the imaging paths of the beam splitter system or can be achieved by setting or positioning the at least two cameras with respect to one another.Advantageous refinements of the invention are the subject matter of claims 2 to 20.GENERAL DESCRIPTIONGeneral ConstructionConventional recording objectives can also generate a real aerial image from the emitted or reflected radiation of a scene in addition to a direct imaging onto an imaging sensor. If such a recording lens is separated from the camera on the lens mount, a relay unit can be inserted between the recording lens and the camera in the imaging beam path, which relay unit images the aerial image onto the sensor of a camera. In this case, the recording lens which generates the aerial image can be both a fixed focal length lens and a zoom lens. A relay unit is often designed in two parts, consisting of a first relay optics and a second relay optics. Such a two-part embodiment is often designed such that the first relay optics image the aerial image substantially to infinity.The beam splitter system according to the invention comprises a relay unit having a first relay optical unit and at least two second relay optical units. Furthermore, the beam splitter system has a recording objective on the light inlet side, which is mounted on the relay unit by means of its objective mount. In the imaging beam path, a real aerial image is provided, which is positively refracted by the first relay optics or imaged to infinity and is divided by a beam splitter element into two imaging paths, which are respectively formed from the transmission and the reflection of the imaging beam path. Such a beam splitter element can be designed as a splitter plate, splitter prism or splitter cube. The splitting ratio and splitting behavior of the beam splitter element between transmission and reflection are described in greater detail below.By means of a second relay optical unit, which is positioned in the first imaging path of the transmitted radiation, the aerial image is imaged onto the sensor of the first camera. By means of a further second relay optical unit, which is positioned in the reflected, second imaging path, the aerial image is imaged onto the sensor of the second camera. In this case, the cameras are likewise mounted on the relay unit in a separable (detachable) manner via their camera mount.The relay unit can be advantageously designed as its own assembly in its own housing, to which the recording lens and the two cameras can be detachably mounted (flange-mounted). In this case, the relay unit comprises a camera-side mount for fastening the recording lens, furthermore the first relay lens, the beam splitter element, a second relay lens per imaging path and a lens-side mount for recording a camera in each case. A unit is defined as a camera, which has its own sensor and generates images by converting a light radiation into electrical signals, which are processed in the unit and recorded internally or externally. Such a camera has a mount on the camera side for fastening recording lenses, wherein the recording lenses are not part of the camera.By means of the relay unit according to the invention, two identical image circuits of an aerial image can be imaged on the respective sensors of the two cameras. If a modification is now carried out on at least one of the images to be imaged onto the sensors of the two cameras by a further device in the relay unit or by further settings in the relay unit or on at least one of the two cameras, two variants of a moving image sequence can be generated. These possible modifications are explained in more detail below.The relay unit forms a complete beam splitter system with the detachably attachable (flangeable) recording objective and the detachably attachable (flangeable) cameras. In this case, the relay unit is the central unit in which the center of gravity of the complete beam splitter system is also located. It is therefore expedient for the relay unit to have connection devices for a camera stand or other camera carrying devices on its underside or on the outer sides. These can be screw threads in particular. To these, displacement plates can be mounted for balancing a complete beam splitter system.In addition to the described light entry and light exit, the relay unit advantageously has a housing which is opaque to light and is completely closed in order to prevent the entry of scattered light.It is also possible to place further beam splitter elements in the parallel beam path, which beam splitter elements split the light into further imaging paths, which are imaged onto the sensors of further cameras by means of further second relay optics. This is useful when more than two recordings with respectively different settings or modifications are desired.Express reference is made to the possibility of such refinements having more than one beam splitter element and more than two imaging paths. However, for the sake of simplicity, the possible embodiments and refinements will be explained below on the basis of beam splitter systems having only two imaging paths and two cameras.Relay OpticsThe first relay optics and the at least two second relay optics of the beam splitter system according to the invention advantageously have the same or almost the same focal length, provided that an essentially parallel beam path is provided between the two optics. This ensures that the imaged image size at the respective sensors of the two cameras corresponds to the size of the aerial image.It may also be useful to determine the focal length of the at least two second relay optics slightly greater than that of the first relay optics, in order to avoid or reduce, for example, vignetting or edge blur due to the relay transmission. The imaged image at the respective sensors is thus slightly larger than the aerial image. For this purpose, the focal length of the second relay optics is to be selected to be greater in a range from 0 to 10% than the focal length of the first relay optics, in order to obtain the basic character of the focal length of the recording objective.However, it is also possible for the focal lengths of the first relay optics and of the second relay optics to be significantly different, in order, for example, to adapt the image circle of the recording objective to the sensor size of the cameras. In this case, the focal lengths of the two second relay optics of the two imaging paths can also be designed differently, for example if the sensor sizes of the two cameras are different from one another and are intended to be adapted or if an enlarged image section is desired on a camera.In the film industry, a photographing lens is often designed to fill the image window of a movie camera or a sensor of a camera having a size of super 35 mm in the image. This recording format has a defined size of 24.89 x 18.66 mm and results from the maximum usable area of the individual image fields in film cameras, which are arranged at a distance of four perforation holes in the vertical image orientation. A recording objective which can fully image the format Super 35 thus has an image circle of at least 31.1 mm or of 32 mm. Since Super 35 recording objectives are a widely used standard, it is advantageous if the relay unit with the first relay optics and the two second relay optics can likewise image an image circle of at least 31.1 mm or 32 mm on the respective sensors. Advantageously, the transmission should be even somewhat larger, for example with an image circle diameter of 34-35 mm in order to create space, to shift a sensor section with a size of super35 slightly in the horizontal and / or vertical direction, in order to align the two receptacles congruently with one another, for example.In an advantageous embodiment, at least one of the second relay optics can be interchangeably mounted in one of the imaging paths in order to allow the use of a longer focal length for this second relay optics and to enlarge the imaging of this imaging path. It is also conceivable to use a zoom lens as second relay optics in at least one of the two imaging paths.The first relay optics are focused on the focal plane of the aerial image. This focus adjustment can be rigid or adjustable. A matching as a rigid design can be achieved, for example, by tight manufacturing tolerances or by shims. A variable setting can be implemented by means of a worm, a fine thread, an internal focusing or a floating element. Since the contact dimension of the first relay optics is primarily adjusted in this case, a focusing device with a small adjustment range of a few tenths of a mm is usually sufficient.The focusing of the at least two second relay optics onto the sensor plane of the respective cameras can be embodied to be rigid or adjustable. A matching as a rigid design can be achieved, for example, by tight manufacturing tolerances or by shims. A variable adjustment possibility by means of a focusing device is advantageous here. This can be done by means of a worm, an internal focusing or a floating element. Since the contact dimension of the second relay optics is primarily adjusted in this case, a focusing device with a very small adjustment range of a few tenths of a mm is usually sufficient. This can be realized, for example, by means of a fine thread on the lens unit of the respective second relay optics, which determines the axial displacement of the lens unit by means of an axially guided adjusting ring. Such an adjustment is advantageously self-locking or fixable so that the contact dimension of the second relay optics does not adjust during the picking up or transport of the system.The focusing options described here serve primarily to tune the first relay optics and the second relay optics in the respective imaging paths to one another, to the sensor planes of the cameras and to the recording lens.By means of an adjustable focusing device of at least one of the two second relay optics, manufacturing tolerances with respect to the contact dimension of the cameras can be adapted to one another and compensated for, for example. A further advantage of adjustable focusing of the second relay optics results if the cameras record the light in different spectral ranges, in particular if one of the cameras records the visible light, while the other records the spectral range of infrared or near infrared. Due to the different refractive behavior of different spectral ranges, it is advantageous if the focusing of at least one of the two second relay optics can be individually adapted to the focusing of the other imaging path. Ideally, both second relay optics have such a focusing device, since both cameras can thus be tuned completely and independently of one another. A further application is the targeted setting of a slightly different focal plane of the image on the sensor plane at one of the second relay optics, in order to increase the depth of focus, for example. If the focus at one of the second relay optics is slightly adjusted, this camera records a slightly different focal plane than the other camera. In this case, the distance between these two focal planes can be determined such that the focal depth ranges of both recordings are each still minimally superimposed. There are thus image areas imaged by one camera with the highest possible sharpness that border image areas imaged by the other camera with the highest possible sharpness.In photography, a focus stacking method is well known for increasing the depth of field. In this case, from a plurality of images which are recorded successively with a respectively slightly shifted focal planes, the respectively most sharp image parts are merged to form a new image with an increased depth of focus.Such a method can likewise be used for motion picture sequences by means of the beam splitter system according to the invention. By electronically selecting and combining the respectively most sharp image regions of each individual image of the two image variants, a new image sequence with an increased depth of focus is created.With regard to the light intensity of the relay unit, it should be noted that the maximum transmittable diaphragm aperture is determined both by the light intensity of the recording lens and by the light intensity of the first relay optics and the second relay optics. The maximum light intensity of the overall system can only be as great as the maximum light intensity of the least luminous component. If, for example, the relay unit, consisting of a first relay optics and at least two second relay optics, has a diaphragm 4 as the largest opening and the recording objective has a diaphragm 1.4, then the maximally transmissive opening amounts to a diaphragm 4, even if a larger diaphragm opening than a diaphragm 4 is set at the recording objective. If the aperture is changed in the range of 1.4 and 4 at the recording objective, then no change of the image is to be detected; in particular, the depth of focus and the Bokeh do not change. In this case, the depth of field corresponding to a diaphragm 4 is always shown. Changes in the depth of focus become visible only when an aperture value greater than 4 is set at the recording lens.It is therefore advantageous if the relay unit itself has the greatest possible light intensity, for example a diaphragm 2, since otherwise the recording lenses mounted on the beam splitter system are greatly limited in their maximum light intensity and recordings with a small depth of focus are no longer possible, since they are not transmitted by the beam splitter system.The desired aperture of a photograph is preferably adjusted at the photographing lens. This is advantageous because both imaging paths thus have the same aperture setting and thus the same depth of field. Since the photographing lens is familiar to a cameraman, he can make the diaphragm setting as usual.However, it is also conceivable for the diaphragm setting to be carried out on the first relay optical unit. Here too, the selected aperture would be the same for both imaging paths. A change in the aperture setting at the respective second relay optics is also possible, but has the result that the depth of focus is no longer the same for differently selected apertures in the image of both cameras.It can thus be stated that the aperture can be determined on one or more of the following optical units: on the recording objective, on the first relay optical unit and / or on the at least two second relay optical units, even if it is advantageous in most cases to set the aperture on the recording objective.Filterings to Adjust the ExposureThe actual exposure time of motion picture cameras can be defined as an absolute value or as a relative value, depending on the image rate, and can be at most the value of second / image rate. In conventional film cameras, the exposure time is determined by a circular diaphragm which usually has a sector angle of 180°. Therefore, the exposure time is often half the maximum exposure time, which corresponds to a time of 1 / 48 s for example, in the case of 24 images per second, even in the case of digital motion picture cameras. If both cameras are set to a relative exposure time, the respective exposure time is dependent on the frame rate.For example, the exposure time for a 180° shutter at 24 fps (frames per second) is 1 / 48 s and at 60 fps is 1 / 120 s. Thus, during an exposure process, significantly more light impinges on the sensor of the camera running at 24 fps, namely by a factor of 2.5, which corresponds to approximately 1.3 diaphragms. If the sensors have the same sensitivity and the beam splitter has a ratio of 50:50 between transmission and reflection, the light intensity of the two imaging paths must be matched to one another.In order to compensate for this difference in the exposure time, it is advantageous if the light intensity is adjusted by means of a gray filter which is inserted after the beam splitting into the imaging path of the camera running at 24 fps. Gray filters change only the light intensity, but not the character of a light beam, and are frequently available in third aperture stages, but sometimes also only in full aperture stages. In both cases, the gray filter is used to adapt the light intensity, which is closest to the arithmetic value of the required light reduction. In the example listed above, if only full aperture stages are available, this is a gray filter with a reduction of one aperture stage.Small aperture differences of less than one aperture can be completely corrected in postproduction in the so-called light determination. Thus, both cameras now have a correct and largely matched exposure and provide two otherwise identical recordings, one with an image rate of 24 fps and the other of 60 fps.Instead of using a gray filter, it is also possible to use a beam splitter element for modifying the light intensity of the imaging paths, which beam splitter element has a division ratio of 66.6:33.3, for example, and assigns twice the light intensity to the path of the camera running at 60 fps. In this case too, the exposure would be adapted by one full aperture stage to that of the other path, which can be completely compensated for in the light determination of the recording.It is likewise possible to adapt the exposure time of the camera running at 24 fps to the exposure time of the camera running at 60 fps, so that both sensors expose each time for the same length of time. However, the relative motion blur of the two recordings is no longer equal to one another. Thus, the camera running at 24 fps would have a less quiet scroll that can act "stroboskobobe-like.". This may possibly be required in such a way that, otherwise, it is recommended to adapt the exposure by means of gray filters and / or the division ratio of the beam splitter element.Compensation of the exposure by masking the second relay optics of the camera running at 24 fps by one full aperture or more precisely by 1.2 aperture steps is therefore not expedient, since the depth of focus of this imaging path changes as a result and is therefore no longer identical to the second imaging path. If necessary, this may be so desired in a concrete manner, but should otherwise be avoided.Use of other filtersTo achieve different imaging variants of a scene, besides gray filters, a plurality of different filters can be used to modify one or both imaging paths. These can also be, for example, filters which block specific regions of the visible or invisible light spectrum, in particular those which block exclusively the region of infrared or near infrared or pass only this spectral range, which is explained in more detail below.It is also conceivable to use effect filters, such as star filters or streak filters, which generate a star image or a stripe in bright, punctiform image areas. Likewise, at least one of the imaging paths can be modified by means of soft-focus filters, low-contrast filters, color effect filters or gradient filters. A further field of application of filtering can be achieved by using polarization filters, in particular for generating cross-polarized images, which will be explained in more detail below.Advantageously, filters of each imaging path can be placed between the beam splitter element and the second relay optics for this purpose. If the first relay optics is designed such that it images the aerial image substantially to infinity, the thickness of the filter glass has no influence on the image. However, it is also possible to position a filter in the imaging path between the respective second relay optics and the sensor or to integrate it into the second relay optics.The filters can be, for example, screw filters, foil filters, round or angular filter disks or have other embodiments. In this case, at least one imaging path should have such a filtering capability in order to enable adaptation of the exposure and / or further modifications to the other imaging path. Ideally, each imaging path has its own independent filtering capability.Advantageously, the filters can be inserted interchangeably into a filter holder and can be fixed therein, for example by clamping or a screw ring. Such a filter holder can be designed, for example, as a filter insert which is mounted in a guide which is oriented perpendicularly to the optical axis of the imaging path. The positioning of a filter by means of the filter holder can advantageously be fixed in the relay unit by means of a screw connection, a latching or a clamping in such a way that the filter is held securely in its position during the receiving or transport. The filter holder is advantageously connected to the relay unit in a light-tight manner in order to prevent undesired light entry.When polarization filters, leaf filters, star filters or gradient filters are used, the angle of rotation of the filter can be determined centered about the optical axis, since the filter delivers different results depending on the angle of rotation set. It is therefore advantageous if a cameraman can determine and adjust the angle of rotation of filters during recordings themselves.This is achieved in that the filter holder is mounted with a pivot bearing, preferably with a circumferential bearing ring, which enables rotation and fixing of the set angle of rotation of the filter about the optical axis. Advantageously, the setting of the angle of rotation can also be determined in the case of an already inserted filter holder. This can be achieved, for example, by transmitting the filter rotational position by means of a toothing, a toothed belt or a friction wheel. The fixing of the set rotation can be effected in a self-locking manner, by clamping or locking.If a specific filter is introduced into only one of the two imaging paths, recording variants can be realized with otherwise identical recording settings, which then each have the filter characteristic or do not have these in the filterless variant. In postproduction, by mixing the two images, any intermediate value of the filtered and unfiltered version can be determined and rendered accordingly. It is likewise possible to generate a dynamic transition from the filtered version to the unfiltered version or vice versa by means of a cross-fade. The cameraman or director is thus given the option of determining the intensity of a filtering or the time and duration of a dynamic change of such a filtering after the actual recording completely freely, corresponding to the curative requirements.Use of Different Beam SplittersThe determination of the light intensity of the at least two imaging paths can be established and modified not only by using gray filters but also by means of the division ratio of the beam splitter element.An obvious possibility is to design the beam splitter element as a 50:50 division, whereby two imaging paths equivalent in their light intensity are generated. If a different light intensity is desired for the respective imaging paths, because, for example, the exposure times are different, the assignment of the light quantity per imaging path can be modified and defined by means of the division ratio of the beam splitter element.In a beam splitter element with a 50:50 division, the light loss per imaging path is in each case one aperture, while in a 75:25 division it is approximately 0.4 aperture stages for one imaging path and two apertures for the other imaging path. If a beam splitter ratio is thus selected which reproduces as exactly as possible the differences in the exposure settings of the two cameras, this ensures the greatest possible use of the light present, because different exposures do not have to be compensated by gray filters.Since the beam splitter element has an important role in compensating for exposure differences, the beam splitter element is advantageously designed such that it is connected to the relay unit in a separable (detachable) manner and variants with different graduation ratios or graduation properties can be used and fixed in a positionally accurate manner. This is advantageously achieved by means of a registration which engages in a positively locking manner in a receptacle of the relay unit. Such a receptacle should be fixable in the relay unit, for example by clamping, screwing or locking. The beam splitter holder is advantageously designed such that it is to be connected to the relay unit in a light-tight manner in order to prevent undesired light entry.By using beam splitter elements with matched division ratios, it is possible to completely or partially compensate for differences in the exposure time, the sensor sensitivity, the aperture setting, a different filtering or in the imaging of different spectral ranges.The two imaging paths can likewise also be modified by means of polarizing beam splitters, in which the splitting ratio is determined by the polarization angle of the entering light.A further possibility of modifying the imaging paths can be achieved by means of a beam splitter element in which the splitting ratios are determined by the wavelength of the entering light, in particular with a cut-off wavelength between 700 and 780 nm. The incoming light is divided into visible light and infrared light by such a beam splitter. A prerequisite for the recording of infrared light by the sensor of the corresponding camera is that it does not have its own IR blocking filter.Regardless of the light loss, which is given by the splitting ratio between transmission and reflection at the beam splitter element, the system also has an additional low light loss, which arises as a result of residual reflections during the passage of the light beam at surfaces with different refractive indices and in the glass itself. Since this is very small, it will not be explained in greater detail here.Any desired combinations of the above-mentioned modification possibilities are also possible for adjusting the exposure. If, for example, distinct differences between the two exposure times are desired, it is expedient to achieve a rough adaptation of the exposure first by means of a suitable division ratio of the beam splitter element, since the respective maximum light intensity is thereby conducted to the sensors of the cameras. Fine tuning can subsequently be achieved by an additional use of gray filters. A first predetermination of the splitting ratio at the beam splitter element is also useful insofar as beam splitting plates, beam splitting prisms or beam splitting cubes are often available only with a few splitting ratios and can therefore be tuned less finely than is possible with gray filters.An adaptation of the exposure by means of the exposure time of the sensor is not expedient in most cases, since the characteristic of the representation of moving objects thereby changes insofar as the motion blur is no longer represented identically.Recordings of Motion Picture Sequences in Different Spectral RangesDigital motion picture camera sensors are usually designed to be sensitive to visible spectrum light, but to be insensitive to other spectral ranges, particularly infrared and near infrared light. This is usually achieved by a short-pass filter which is mounted in front of or on the sensor and no longer transmits light radiation from a limit wavelength of approximately 780 nm. It is also referred to as an IR blocking filter, which most sensors of digital cameras have.In part, these filters are firmly cemented to the sensor, but in part they are also removable. If such a short-pass filter is removed and replaced by a complementary long-pass filter, which transmits the light only from a limit wavelength of approximately 780 nm, then such a camera records only infrared light, in particular near infrared light, while visible light is no longer imaged. A certain selectivity is given in the boundary region due to the filter. In part, the cut-off wavelengths in the photograph and film are also in a range up to 700 nm. The fields of application presented therefore also apply to spectral ranges which are not separated exactly at 780 nm and lie in the range from 700 nm to 780 nm.If the imaging paths of both cameras are now equipped with complementary long-pass and short-pass filters having a limit wavelength of 700 nm to 780 nm, identical congruent images of a scene can be recorded, which differ in that one camera records only visible light and the other records only IR light.If the IR short-pass filter, which is usually mounted in front of or on the sensor, is removed in a camera or if the sensor does not have such a filter, then a long-pass filter, which is then necessary and blocks the range of visible light, can be placed at different locations in the imaging path of the infrared path. On the one hand, it can be positioned directly in front of the sensor, but equally well be arranged in the imaging path between the beam splitter element and the second relay optics, in particular in the filter holder provided for this purpose.In addition to the color channels red, green, blue of the visible light, a congruent additional infrared channel is thus created and assigned to the moving image sequence. This can contain additional image information or contain, as an additional auxiliary channel, for example, masks for separating image elements, markings or information about depth pitches of a scene.As an example for obtaining additional image information, it can be mentioned that leaves of plants are displayed, for example, almost white in an infrared photograph, while a blue sky is usually imaged black. With such an effect, it is possible, for example, to rotate so-called "day for night" scenes. During this, a scene is recorded in daylight, which represents a night scene in the finished film. Such image effects can be converted by imaging a black or almost black sky of an infrared recording. For this purpose, the color channels red, green and blue of one camera are digitally combined with the infrared channel of the other camera after the recording until the desired image effect is achieved, in particular in order to feed colored picture elements to a shaded infrared channel.In one development, one or more light sources are assigned to the beam splitter system, which is adapted such that they emit either only visible light or only infrared, in particular near-infrared light.In particular in the case of LEDs, light sources are known which emit exclusively near-infrared light. If a background of a scene is illuminated exclusively with such a light source, while a foreground is illuminated exclusively with visible light and a sufficient separation is ensured by the spatial distance of foreground and background, masks can be generated with the aid of the infrared channel, with which masks a foreground element of the foreground recorded with visible light can be isolated. This can then later be combined, for example, with another background image, the image signal of the infrared channel being used as a mask.If a light source emits both visible light and infrared light, it can be filtered by a corresponding short-pass filter or long-pass filter, which is positioned in the light outlet, in such a way that it emits only visible light or infrared light.A further application can be achieved, for example, by illuminating a performer from a soft, diffuse light source which emits light of the visible spectrum exclusively. With a further, but punctiform and hard light source, which illuminates the performer exclusively in the near infrared spectrum, a mask can be produced in the infrared channel, which mask corresponds to a light distribution of strong sunlight. If the image signal of the soft representation of the visible light is now split into two different color determinations, one corresponding to a darker shadow representation and the other light direct sunlight, a mixed image can be produced with the aid of the mask of the infrared channel, which mixed image shows the performer in bright sunlight with corresponding shadow effects. Both the intensity and the time and the duration of a transition of such a light effect can be determined accurately later in the postproduction and offer the cameraman or the director a great freedom of design at a later time than the actual recording.In a further development of the invention, the associated light source is a projector which projects patterns exclusively in the infrared light onto a display device or a scene. These patterns can be, for example, checkerboard patterns, lines or irregular structures that are imaged exclusively on the sensor of the infrared-sensitive camera and have no influence on the recording of the visible light of the other camera. These patterns can be used via digital analysis methods to generate depth information of a scene from the image signals. It is therefore possible to generate a completely independent depth channel with the aid of such a method in addition to the color representation of a scene.Cross-polarized photographA further refinement of the beam splitter system is provided by the assignment of one or more light sources which emit polarized light and are combined with additional polarized filtering within the beam splitter system.In the cross-polarized photograph, an object or a displayor is illuminated by one or more light sources, the beams of which are polarized in a defined direction by means of a polarization filter. If a plurality of light sources are used, these advantageously have an identical polarization orientation. In front of the recording lens of a camera, a second polarization filter is arranged, the orientation of which is arranged rotated by 90° with respect to the polarization direction of the light source. This completely suppresses reflections of highlighters and only the diffuse portion of the light is imaged. The impression of a completely matt image effect is produced which no longer has any reflections from a light source and appears completely softly illuminated.By means of the beam splitter system according to the invention and associated polarized light sources, it is thus possible to realize two otherwise identical recordings of a scene, wherein a cross-polarized image is recorded in one imaging path and an image with highlighters is recorded in the other imaging path. This is achieved by arranging, for example, in the first imaging path between the beam splitter element and the second relay optical unit a polarization filter which is rotated by 90° with respect to the polarization of the light source. No polarization filter is placed in the second imaging path or this polarization filter has the same orientation as the polarization of the light source. Accordingly, the highlight lights in this imaging path are not erased but are also imaged. Thus, one camera captures a highlight-free, cross-polarized matte image while the other camera records a "normal" image effect with highlighters.In computer animation, cross-polarized recordings from performers are required as textures that are projected or "mapped" onto digital bodies or objects. Since the two images differ with otherwise identical camera settings only in that one variant has highlight images, while the other does not show them, the highlight images can be isolated by subtracting the two images and are thus likewise available as an additional image channel for computer animation. A cross-polarized texture and channel with reflections and highlighters are thus provided for further processing. In addition to the use as textures in computer animation, such cross-polarized images can also be used as visual effects, since the image effect, due to the absence of highlighters, becomes a rather non-effective and "non-home" character and even faces often act "aliased".Instead of being modified by one or more polarization filters, the imaging paths can also be modified by means of a polarizing beam splitter element, in which the splitting ratio is determined by the polarization angle of the entering light. As already mentioned, the beam splitter elements can be advantageously exchanged and positioned and fixed depending on the application.Registration and Adjustment of the Sensor SectionAdvantageously, both the recording lens and the cameras are mounted on the relay unit in a separable (detachable) manner. It is thus made possible for a cameraman to select a specific recording objective preferred by him from a multiplicity of fixed focal lengths or zoom lenses and also to be able to freely determine the focal lengths of the recording objective.Likewise, it can select for recording from different camera types depending on its preference or the requirements of the project. In this case, different camera types can also be used for the two imaging paths. For example, a special slow motion camera can be selected for one imaging path and a further camera with a normal frame rate can be selected for the second imaging path.If the recording lens is detachably connected to the relay unit, the relay unit advantageously has a camera-side mount on the light inlet side, which mount can be, in particular, a PL mount or an LPL mount, but also another known mount that is established on the market, which is customary for professional film optics. This can also be, for example, a canon EF, canon RF, nikon F, nikon Z, fuji or sony E mount. By using adapters, a plurality of lenses with a specific mounting standard can also be adapted to different mounts on the camera side.If one or both cameras are also connected to the relay unit in a separable manner, it is advantageous if these cameras each have a mount on the lens side on the imaging paths of the light exit, which mount engages in the mounts of the cameras and can be locked there in a fixing manner. Such a mount can be, in particular, a PL mount, an LPL mount or another common mount, such as, for example, Canon EF, Canon RF, Nikon F, Nikon Z or Sony E mount.Current digital film cameras are often very compact and light. It is therefore possible for the weight of the cameras to be completely supported by the camera-side mount, for example by a PL or LPL mount. For additional further fixing, the cameras can be fixed to the relay unit by means of additional supporting or stabilizing elements. This is helpful, for example, if the lock on the mount of the camera cannot completely prevent a slight rotation about the optical axis. Even a slight lateral displacement perpendicular to the optical axis cannot be completely prevented due to the tolerances of such mounts and can likewise be completely fixed by such further support elements.If the same sensor section is set at the cameras, the images recorded by the cameras are largely congruent. Smaller differences can result from the position of the sensors, which are not positioned completely congruently in the imaging paths or due to assembly inaccuracies of the mounts and / or of the two second relay optics. This can result in a slight offset in the image signals of the cameras. This can be in particular a translation, a rotation and / or a difference in scale.Such minor differences in the imaging of the two imaging paths can be compensated electronically in post-production by digitally comparing the images of both cameras with one another and electronically adapting the geometry of the images with respect to one another. One speaks of an electronic registration which ensures that the two cameras image a scene completely congruently with one another.An alternative to electronic registration is mechanical registration. For this purpose, the beam splitter system can comprise a mechanical displacement device which makes the sensor of at least one camera displaceable in the horizontal and / or vertical direction parallel to the sensor plane. For example, the displacement device can comprise at least one bearing device which is designed to mount the light-exit-side, objective-side mount on the relay unit in a plane perpendicular to the imaging path in a displaceable manner. This can be implemented, for example, with a guide, a linear guide, a cross roller bearing or a slide. A camera mounted on the lens-side mount can thereby be displaced (moved) in the plane perpendicular to the imaging path (and parallel to the sensor plane) in the horizontal and / or vertical direction, as a result of which the sensor section is also displaced with respect to the imaging path in the horizontal and / or vertical direction. The displacement device described here thus allows the sensor or the sensor section to be easily displaced with respect to the imaging path of the relay unit and thus brought into the desired position.It is advantageous from a design standpoint to provide a first horizontal displacement device for the camera of the first imaging path, which device enables displacement of the camera or of the sensor (sensor section) parallel to the horizontal sensor edge, and a second vertical displacement device for the camera of the second imaging path, which device enables displacement of the camera or of the sensor (sensor section) in the vertical direction. As a result, both a horizontal and a vertical displacement can be implemented with a comparatively low construction outlay. Alternatively, it is also conceivable that the first displacement device for the camera of the first imaging path and / or the second displacement device for the camera of the second imaging path are each designed to (individually) displace the cameras in the vertical and horizontal directions. This alternative embodiment is more complicated in terms of construction, but more flexible in terms of handling, since both cameras can be individually displaced in the horizontal and vertical directions. Independently of the specific embodiments of the displacement devices described here, the latter can furthermore comprise a fine adjustment for the displacement in the horizontal and / or vertical direction. Such a fine adjustment of the displacement can be realized, for example, with one or more adjustment spindle(s). A displacement, once determined and set, should also be fixable in this case. This can be done either in a self-locking manner, for example by a self-locking adjustment spindle, clamping or locking of the displacement device.By means of a horizontal displacement of the sensor section at the objective-side mount of the relay unit of one imaging path and a vertical displacement at the objective-side mount of the other imaging path, a very precise registration of the two images with respect to one another can already be achieved. To set this mechanical displacement, the image signals of the cameras can be superimposed, for example, so that the coverage of the signals becomes visible and can be adjusted accordingly.Such a mechanical registration is already sufficient for a large number of applications. If a pixel-accurate registration is required, this can be achieved by an electronic further fine adaptation in the mail production at a later point in time.It can also be advantageous to provide a mechanical adjustment possibility for the rotation of a camera about the optical axis in order to also compensate for small differences in the rotation of the images with respect to one another. For this purpose, the beam splitter system can furthermore have a rotation device which is designed to mount the objective-side mount on the light exit side of the relay unit for the first imaging path and / or second imaging path rotatably about the optical axis of the respective imaging path. If a camera is flange-mounted on the respective mount (as a result of which a rotation starting position is defined), the image on the sensor can likewise be rotated by the rotation of the mount relative to the imaging path. It is advantageous if the rotation of such a mount can also be fixed. This can be realized, for example, by clamping or by means of a self-locking fine adjustment, for example, via an adjustment spindle of the rotation device.The horizontal and vertical setting of the sensor section presented here only requires a setting range of a few tenths of a millimeter, since it only brings into registration the otherwise identical image sections of the sensors. If the adjustment range of the horizontal and / or vertical displacement device is increased to an adjustment path of a few millimeters, this can also be used for adapting image sections, as presented below.Use for different image sectionsUsually, if different aspect ratios are required for the evaluation of a scene, a maximum large sensor surface is selected for the recording, from which the two aspect ratios can be formed by means of image cropping. This is customary, for example, if a film project having an aspect ratio of 2.4:1 is evaluated in the motion picture as a so-called cinemap and an aspect ratio of 16:9 is additionally to be provided for the television. In this case, a maximum sensor area is usually exposed, from which both formats are then formed by trimming. This is relatively simple to implement in this case, since both evaluations have a horizontal orientation. That is, the horizontal image side is longer than the vertical one in both cases.For the evaluation in social media, a vertical image orientation is increasingly required, often in an aspect ratio of 9:16. If it is desired to create such an aspect ratio of 9:16 from a pure image clipping of a horizontally oriented output image, this results in a loss of a considerable portion of the image information on the image sides. This can result in a scene no longer being displayed in an understandable manner, for example if players who are located laterally in the image are no longer being displayed by the image clipping.It is more advantageous if a second vertically oriented image section is already recorded during the recording, which image section uses the sensor as extensively as possible. This can be achieved by mounting one of the cameras, for example on its mount, rotated through 90° about the optical axis of the imaging path. In this case, one camera takes a horizontal image orientation and the other a vertical image orientation. The images overlap in a region in the center of the image, but both use an identically large sensor area which is considerably larger than if the vertical orientation were formed merely by image trimming.A PL mount or an LPL mount are conventional connections between a camera and recording lenses of professional film equipment. In addition to a guide ring which centers the objective with respect to the sensor, they also have a registration pin which engages in a guide slot which is rotated through 90°. By means of this pin, recording lenses can be connected to a camera at a defined angle, which can be rotated by + / -90°, or by 180°. Conversely, a camera can also be fastened to a lens-side PL or LPL mount, as the relay unit can have, rotated by 90°. Thus, by means of a PL or LPL mount, a change from a horizontal to a vertical image orientation can easily be achieved by a rotation on the mount by 90°, in that the camera is no longer mounted on the relay unit in an upright manner, but rotated by 90°.If the relay unit does not have a PL or LPL mount, but rather, for example, a mount from Canon, Nikon or Sony or another manufacturer, then the objective-side mount of the relay unit of at least one of the cameras can be mounted mechanically by the above-described rotation device in such a way that it can be rotated through 90° about the optical axis. This rotation can advantageously be locked at 90°.If the sensor of one camera records a vertical image orientation and the sensor of the other camera records a horizontal image orientation, this can lead to the respective image sections not being optimally matched to the horizontal orientation, in particular in their vertical orientation. If, for example, a human is depicted in both variants, the head would presumably be depicted relatively close to the upper image edge in a horizontal orientation. If the image section is rotated only centrally by 90° on the other camera with a vertical alignment, then the head of the displayor would be positioned relatively "deep" in the image in this case.This is referred to as a "headroom", the distance a head or object has to from the upper edge of the image. For aesthetic reasons, this is adapted accordingly in different aspect ratios so that the vertical placement of a performer acts in a consistent manner for both evaluations. For this purpose, it is advantageous if the vertical image section of the cameras can be adapted to one another so that a voiced head room is achieved in both cases.Such an adjustment of the head room can be determined and adjusted by means of the vertical displacement device explained above. In this case, the image section of the vertical orientation can be shifted in such a way that the image content is placed "higher", or the displayed image section of the horizontal orientation can be shifted in such a way that the image content is placed "lower".For the corresponding positioning, it is advantageous if both the recording objective and the relay unit can represent or transmit an image circle which is larger than the sensor surface used for imaging in order to ensure sufficient space for such a displacement.It can likewise be advantageous if at least one camera is also designed to be adjustable in the imaged horizontal image section, in order, for example, to position an important image element horizontally in such a way that it becomes visible as clearly as possible.It is also conceivable that the resolutions, sensor sizes or the pixel density of the cameras are different when creating different aspect ratios. For example, it may be useful to record an aspect ratio of 2.4:1 with the maximum possible resolution using a very high-resolution camera for a high-resolution kino evaluation, while the other camera records with a significantly lower resolution, which is however sufficient, for example, for the requirements of social media evaluations. It is also possible, of course, to combine different image rates, exposure times, filterings and different aspect ratios with one another as desired.Synchronization of the camerasIn the case of simultaneous recording by two or more cameras of the beam splitter system, it is advantageous if the cameras are coupled to one another in such a way that they can share control signals, clock signals, time signals or metadata with one another.This includes the possibility of starting and stopping the recording of a moving image sequence of the cameras at the same time in order to record an identical time window of a real event. This can be achieved by a start or stop signal being transmitted simultaneously to the at least two cameras by a remote switch.Another customary method for simultaneously triggering and stopping a recording of two or more cameras is a so-called master-slave connection of the cameras. Here, one of the cameras is determined as a master camera, while the others are determined as slave cameras. Settings or control signals are sent from the master camera to the slave cameras and executed simultaneously. Such a connection is usually made via a control line, frequently via an Ethernet protocol or Bluetooth.It is advantageous, especially with regard to the further processing and evaluation of the film clips produced by the cameras, if the recorded moving image sequences have as uniform a formatting as possible, or uniform metadata. It can thus be achieved that a sequence of cuts from the recording material of one camera to the recording material of the other camera can be transmitted automatically or largely automatically. It is thus possible with comparatively little effort to produce a second version of a film which has the desired variance, which is defined for example by a different image rate or a different aspect ratio.Therefore, the film clips recorded by the cameras should have equal clip names, contain equal time stamps and run in phase with each other at the same frame rate of the cameras. Identical time stamps can be achieved by connecting the cameras to an external timer or by synchronizing their internal clocks with one another.If both cameras have the same frame frequency, these should advantageously also record a moving image sequence in the same phase. This means that the recording of each individual image of a moving image sequence begins at the same time and is ended at the same time at a later time. For example, the motion blur of an object in motion is thus also imaged identically by both cameras.The synchronization of the exposure phases of the cameras can be achieved via an external sync generator which supplies a common clock signal to the cameras. Depending on the camera type, such synchronization is often also possible in master-slave mode.In contrast to being in phase-stable, it can mean that the exposure start and / or the exposure end of the recordings of the individual images is not simultaneous. This is the case, for example, when two cameras are running with the same frame rate but with different exposure times. In this case, both the start and the end of an individual image exposure or both events cannot take place simultaneously, depending on how these two exposure windows are situated with respect to one another in time.It is also expressly possible for both cameras to run phase-shifted with respect to one another. This can mean, for example, that the one camera starts an exposure, while the second simultaneously ends its exposure, and vice versa. In the case of a phase-shifted recording with a 180° shutter in each case, both cameras are exposed for the same length and record the light in oppositely directed time windows which do not overlap in time.This can be used if, for example, light sources are also assigned to the system in such a way that they are likewise synchronized with the exposure frequencies of the cameras and in the process illuminate a scene in a pulsed manner and in each case only in the exposure phase of one or the other camera. Thus, light sources are possible which become visible only on one or the other variant of an image sequence. For example, two completely different light variants can be recorded from one scene in this way. These can be combined with one another during the cut in any mixing ratio or combined with one another as a dynamic transition at any desired point in time and with any desired crossfade duration.If a camera does not run with the same but with a multiple of the image rate of the other camera, then depending on the camera type a phase-stable coupling of the cameras is usually also possible and should be used as far as possible.If the exposure phases of the cameras can no longer be synchronized on account of different image rates, then slice sequences of a variant can likewise be generated quickly and largely automatically with the aid of the time stamps of the individual images and the assignment of clip names.With regard to the (mechanical) embodiment of the beam splitter system according to the invention, it should be added in addition that the beam splitter system can comprise not only a flangeable recording lens and flangeable cameras, which are connected to the relay unit by means of standardized mounts. It is likewise also possible for both the cameras and the recording lens to be combined with the relay unit in a non-separable unit and to form a one-piece beam splitter system. If, for example, the cameras are integrated into the system, a very compact design can be achieved as a result, since electronic components can be combined and each camera does not have to have its own housing, its own image processing and its own image recording. The exact mechanical alignment of the sensors, in particular with regard to their congruity, can also be implemented more easily in a closed system.An advantage of integrating the recording objective into a closed system of a one-piece beam splitter device is, for example, that the pupil positions of the recording objective and the first relay optics can be better matched to one another on the aerial image. Such a matching of the pupil positions is clearly easier to implement if objectives which are not freely selectable and already existing on the market are used. It is likewise possible that only the recording lens or also only one or more cameras with the relay unit are not configured to be separable.BRIEF DESCRIPTION OF THE FIGURESThe invention is explained in more detail below merely by way of example with reference to the figures. FIG. 1 shows a schematic illustration of an embodiment of a beam splitter system according to the invention having a relay unit, a recording objective which can be mounted detachably on the relay unit, and two cameras which can be mounted detachably. FIG. 2 shows a schematic cross-sectional illustration of a further embodiment of a beam splitter system according to the invention, which is designed as a one-piece beam splitter system. FIG. 3 shows a simplified schematic cross-sectional illustration of a detailed view of the relay unit of a beam splitter system having two beam splitter elements and more than two imaging paths. FIG. 4 shows an arrangement of different sensor sections of both recording cameras of a beam splitter system according to the invention. FIG. 5 shows a greatly simplified perspective illustration of a vertical and horizontal displacement device of the mounts on the relay unit. FIG. 6 shows a simplified schematic illustration of an embodiment of a beam splitter system according to the invention with an associated illumination device.DETAILED DESCRIPTION OF THE FIGURESFIG. 1 shows an embodiment of a beam splitter system 1 according to the invention in a simplified form. The radiation 5 emitted or reflected by a scene to be recorded (not shown in FIGS. 1, 2 and 3 ) penetrates through the recording lens 3 into the relay unit 2 and is imaged as a real aerial image 4 in the beam path. Such a photographing lens 3 may be a fixed focal distance or a zoom lens.The aerial image 4 is positively refracted by the first relay optical unit 6 or imaged to infinity. An imaging to infinity is advantageous in that the imaging does not change due to the insertion of plane-parallel optical elements in the imaging beam path.The first relay optics 6 is tuned to the second relay optics 8, 8 ain such a way that there is a sufficient distance between them along the optical axis so that at least one beam splitter element 7 can be inserted therebetween, which splits the imaging beam path 9 into a transmitted imaging path 10 and a reflected imaging path 10 a. Advantageously, the beam path between the first relay optics 6 and the two second relay optics 8, 8 ais substantially parallel.By means of the second relay optics 8 of the transmitted imaging path 10, the imaging beam path of the aerial image 4 is imaged on the sensor 11 of the camera 12. By means of the second relay optics 8 aof the reflected imaging path 10 a, the imaging beam path of the aerial image 4 is further imaged on the sensor 11 aof the camera 12 a.An identical image circle of an identical point of view is thus made available to both sensors 11, 11 a. Provided that the beam path between the first relay optics 6 and the second relay optics 8, 8 ais substantially parallel, the focal lengths of the first relay optics 6 and the associated second relay optics 8, 8 aare selected to be substantially the same so that the image imaged on the respective sensors 11, 11 ahas the same size as the aerial image 4. It is also possible for one of the two second relay optics 8, 8 ato have a focal length that is significantly different from the other of the two second relay optics 8, 8 ato record an enlarged image section or to compensate for a difference in size of the sensors 11, 11 aof different types of the cameras 12, 12 a, for example. In principle, any ratio of focal lengths of the first relay optics 6 to the second relay optics 8, 8 ais possible.The recording lens 3 is detachably (detachably) connected to the relay unit 2, wherein the recording lens 3 has a lens-side mount 14 on the radiation exit side, which engages on the relay unit 2 in a camera-side mount 15 and can be connected and locked in a positive-locking, rotationally secure manner. Such an objective-side mount 14 and the corresponding camera-side mount 15 are advantageously existing standard connections, as are used, for example, by the companies ARRI, Panavision, Sony, Canon, Nikon or Fuji. An advantageous embodiment is the standard of a PL mount or an LPL mount used worldwide in the professional film sector as such an objective-side mount 14 or camera-side mount 15.The cameras 12, 12 amounted on the relay unit 2 advantageously likewise have a standardized camera-side mount 15 a, 15 bwhich engages in an objective-side mount 14 a, 14 bof the relay unit 2 and can be connected and locked with the latter in a positive-locking, rotationally fixed manner. This connection is advantageously likewise designed as an existing standard connection and has mounts from the companies ARRI, Panavision, Sony, Canon, Nikon or Fuji. Here too, a PL mount or LPL mount as the defacto standard of the film industry is an advantageous solution.The second relay optics 8, 8 aeach have a focusing unit 16, 16 a, by means of which a displacement of the relay optics 8, 8 ain the axial direction along the respective imaging paths 10, 10 ais possible. By this displacement, the second relay optics 8, 8 acan be adjusted (independently of one another) in each case such that the image is focused on the respective sensors 11, 11 a. The respective focusing units 16, 16 aare advantageously configured such that they can be locked or self-locking, so that an adjustment during the recording is not possible unintentionally, which is not shown in more detail in the illustration, however. The respective focusing units 16, 16a serve merely for coordinating the contact dimension of the second relay optics 8, 8a with the respective sensors 11, 11a.Instead of the focusing units 16, 16a for the second relay optics 8, 8a, the adjustment of the contact dimension can also be carried out by means of shims or a closely tolerated production. The actual focus adjustment of a scene is however effected at the recording lens 3.Both imaging paths 10, 10 acan be assigned a filter 21, 21 a, which is arranged between the beam splitter element 7 and the second relay optics 8, 8 a. Such a filter 21, 21a is advantageously designed such that it can be exchanged and can be individually determined and used depending on the desired filtering. These may be gray filters, polarization filters, long pass filters, short pass filters, soft drawing filters, star filters, leak filters or further filters. It may often be desirable for only one of the mapping paths 10, 10 ato have such filtering, since two different variants can be recorded in this way, in each case with and without filtering.A sync generator 25 can be connected to both cameras 12, 12 aand supplies these with clock signals and / or time code information, so that the cameras 12, 12 acan run in phase, phase-stable or phase-shifted with respect to one another. In the case of an in-phase recording, both cameras 12, 12 arun at the same frame frequency and the start of the recording of each individual image takes place simultaneously, as does the end of the recording of each individual image. In the case of a phase-stable recording, the exposure time of both cameras 12, 12 acan be different, as can the starting point and / or the end point of an exposure process of a single image. Nevertheless, the time relationships of the respective start and end of an individual image recording to one another remain constant. In the case of a phase-shifted recording, the sensor 11, 11 aof one camera 12, 12 ais exposed, while the other sensor 11, 11 ais not exposed, and vice versa. Instead of a sync generator 25, a direct connection, not shown here, is also possible as a master-slave connection between the cameras 12, 12 a.The beam splitter element 7 can have a division ratio of 50:50 or else any other division ratio. Advantageously, the beam splitter element 7 is connected to the relay unit 2 in a separable (replaceable) manner by means of a beam splitter holder 13, so that different beam splitter elements 7 having different splitting ratios can be positioned and fixed in the imaging beam path as required. Advantageously, the beam splitter holder 13 of the beam splitter element 7 engages in a form-fitting manner in the relay unit 2 and enables a precisely fitting positioning in the beam path. The changing device of the beam splitter element 7 and of the beam splitter holder 13 is not shown in detail.The embodiment shown in FIG. 2 differs from the embodiment shown in FIG. 1 essentially in that both the recording lens 3 and the cameras 12, 12 awith the associated sensors 11, 11 aare integrated into the beam splitter system. The recording lens 3 can be designed as a fixed focal distance or zoom lens.By integrating the cameras 12, 12 ainto the beam splitter system 1, it is possible in particular to combine the electronics of the cameras 12, 12 aand to synchronize them more easily with one another. The use of a fixedly installed recording objective 3 also facilitates the optical design of the first relay optics 6 matched thereto.In principle, one or more of the cameras 12, 12 acan be separately or fixedly integrated into the beam splitter system 1. Likewise, the recording objective 3 can be designed as a separable or fixed component of the system.FIG. 3 shows an embodiment in which the beam path 9, which is imaged substantially to infinity by the first relay optical unit 6, is divided by a first beam-splitting element 7 into a transmitted first imaging path 10 and a reflected, second imaging path 10 a, which generates an image on the sensor 11 aof the camera 12 aby means of a second relay optical unit 8 a. The transmitted imaging path is further divided by means of a second beam splitter element 7 aand imaged by the relay optics 8, 8 bon the sensors 11, 11 bof the cameras 12, 12 b.In this embodiment, identical image circles of the image of aerial image 4 of recording lens 3 are provided to the three cameras 12, 12 a, 12 b, respectively. The exemplary embodiment shows that more than two imaging beam paths are also possible.FIG. 4 shows two image circles 18, 18 awhich are imaged on the sensor plane of the cameras 12, 12 a. Advantageously, the intermediate image generated by the recording lens 3 and the image circles 18, 18a transmitted by the first relay optics 6 and the second relay optics 8, 8a are larger than the image windows 26, 28, 28a, 28b, which are recorded as sensor sections by the sensors 11, 11a of the cameras 12, 12a.This makes it possible to shift the image windows 26, 28, 28 a, 28 bin the horizontal and / or vertical direction slightly within the available image circles 18, 18 a. By means of this displacement, the registration of the two specific sensor sections can be brought into registration with one another or an image section can be modified.The left-hand illustration shows a schematic illustration of an image setter 27 which is imaged by the recording objective 3 and by means of the relay optics 6, 8, 8a on one of the two sensors 11, 11a, in a horizontally oriented image window with an aspect ratio of 16:9. The dashed line shows a vertical cut-out from the horizontal image window 26 a, as may be desired, for example, for use in the area of social media, since a vertical aspect ratio of 9:16 is often used here. It is evident that the pure trimming to an aspect ratio of 9:16 would trim the image on both sides by more than one third in each case and elementary regions of the image are lost.The right-hand illustration of FIG. 4 shows the identical image circle 18 a, as is provided in the second imaging path, and the image of the presenter 27 ain an identical size. The vertically oriented image window 28 is achieved by mounting the camera 11, 11 aof an imaging beam path rotated through 90° about the optical axis. This is possible by means of the PL or LPL mounts already described, since these have a groove which is rotated through 90° in each case and in which a recording pin on the camera mount engages.It is also shown that the display device 27 ais positioned relatively "deep" in the vertically oriented image window 28 and the area above its head to the upper image edge is comparatively large. It is therefore advantageous if at least one of the cameras 12, 12a has a displacement device with which the vertical image section can be determined and set. Such a shifted vertically oriented image window 28 adisplays a downwardly shifted image section that shows less space above the display head and acts more organically.Such a vertical displacement can be achieved by making the mount of the relay unit 2 on the objective side displaceable and fixable in the imaging path of a second relay optical unit 8, 8 aparallel to the vertical image edge of the sensor 11, 11 a. This is explained in more detail below in FIG. 6.It is also conceivable that a shifted and reduced vertically oriented image window 28 bis determined. This can be done by reducing the area of the recorded sensor section or, for example, also by means of a camera 12, 12 aof a different type, which has a sensor 11, 11 awith a lower resolution, since a lower resolution is often sufficient for an evaluation in social media channels.FIG. 5 shows a simplified perspective illustration of a beam splitter system 1 having a recording objective 3 and two cameras 12, 12 awhich are connected to the relay unit 2 which has a vertical and a horizontal displacement device 19, 20. The two camera-side mounts 15, 15 aof the cameras 12, 12 aengage with the lens-side mounts 14, 14 aof the relay unit 2 and are locked there.By means of the horizontal displacement device 20, the objective-side mount 14 rigidly fastened to it can be displaced in the horizontal direction parallel to the sensor plane. In this case, only the mount 14 on the objective side is displaced, and the second relay optics (not shown here) assigned to it remains fixed centrally in the optical axis. By displacing the lens-side mount 14, the camera 12 together with its sensor 11 is also displaced relative to the transmitted imaging path, whereby the position of the image on the sensor section is likewise displaced. This setting can be used for registering the two sensors 11, 11 ain a horizontal alignment or for determining a changed horizontal image section.By means of the vertical displacement device 19, the objective-side mount 14a rigidly fastened to it can be displaced in the vertical direction parallel to the sensor plane. Only the mount 14a on the objective side is displaced here; the second relay optics (not shown here) assigned to it remains fixed centrally in the optical axis of the reflected imaging path. By displacing the lens-side mount 14 a, the camera 12 atogether with its sensor 11 ais also displaced relative to the reflected imaging path, as a result of which the position of the image on the sensor section is likewise displaced. This setting can be used for registering the two sensors 11, 11 ain the vertical orientation or for determining a changed vertical section.Such a displacement device 19, 20 can be designed, for example, by means of a sliding guide, a linear guide, a slide or a cross roller bearing. Advantageously, the determination of the displacement is possible precisely by means of a fine adjustment, not shown here, for example via a threaded spindle. Only a displacement of a few tenths of a millimeter is necessary for registration, and the adjustment range should comprise a few mm for the determination of an image section. Advantageously, the determined and set displacements can also be fixed, for example by means of a self-locking embodiment, a clamping, a screw connection or a latching, which is not shown here.It is also conceivable that the horizontal displacement is carried out on the reflected imaging path and the vertical displacement is carried out on the transmitted imaging path. Likewise, a displacement device can also be provided on one or both imaging paths, which displacement device enables adjustment in the horizontal and vertical direction, as is known in cross tables.An advantageous further development is the possibility of also offering a rotation about the center of one of the lens-side mounts 14, 14 avia a device not shown in any more detail in FIG. 5. Such rotation can be used to fine-tune the registration of minimum rotational errors in the image of the two cameras 12, 12 a, or to bring the sensor alignment into a vertical or horizontal alignment by a rotation of 90°.Figure 5 also shows two inserted filter holders 22, 22a mounted on the relay unit 2. The filter holders 22, 22 apreferably also comprise a cover plate which protects the relay unit 2 from light entering at this location. By way of example, a screw connection is shown here in simplified form, with which the filter holders 22, 22 acan be fastened to the relay unit. This is merely one of many possible embodiments; likewise, catches, clamps or locks are conceivable.The inserted beam splitter holder 13 is also shown in a simplified manner. This advantageously comprises a cover plate which protects the relay unit 2 from light entering at this location. By way of example, a screw connection is shown here in simplified form, with which the beam splitter holder 13 is fastened to the relay unit 2. This is merely one of many possible embodiments; likewise, catches, clamps or locks are conceivable.FIG. 6 shows a simplified schematic illustration of an embodiment of a beam splitter system 1 according to the invention with an associated illumination device 23, 23 a, 23 b, 24, 24 a, 24 b. A display device 27 is illuminated by a light source 23, which emits light of the visible spectrum exclusively or is filtered by means of a filter 24 onto the spectrum of the visible light, for example by means of a short-pass filter, which has a cut-off wavelength in the range from 700 nm to 780 nm.The background 29 is illuminated by a light source 23 awhich emits exclusively infrared or near infrared light or is filtered by means of a filter 24 ato the spectrum of the infrared light, for example by means of a long-pass filter which has a limit wavelength in the range from 700 nm to 780 nm.The cameras 12, 12 aare likewise designed by corresponding long-pass and short-pass filters having a cut-off wavelength in the range from 700 nm to 780 nm in such a way that the one camera records exclusively visible light and the other camera records exclusively infrared light. The radiation emitted by the light source 23 is thus not visible to the camera sensitive to infrared light, while the radiation emitted by the light source 23a is not visible to the camera sensitive to visible light. The background 29 illuminated by the infrared light can thereby be used as a pure mask channel, for example in order to later combine the display device 27 with a new background.In a further example of application, a soft, diffuse surface element 23 emits exclusively visible light onto a display device 27 or a scene by means of a filter 24 or by virtue of its luminous property. A further, punctiform, hard light source 23 b, due to its luminous property or due to a filter 24 b, emits exclusively infrared or near-infrared light onto the display device 27. Thus, one of the cameras 12, 12a records a soft, diffusely illuminated image of the display device 27, while the other records a hard course of light as its own mask channel in the infrared spectrum, which contains no portions of the visible light. If the record of the diffusely illuminated channel of visible light is divided into two light voices in the image processing, one corresponding to that of a dark shadow portion and the other corresponding to that of a bright, bright sunlight, these two light voices can be combined with the mask signal of the infrared recording to form an impression in which the display device 27 is in a bright sunlight.A development of the associated illumination device can be achieved if the cameras 12, 12 aare recorded with phase offset with respect to one another and the light sources 23, 23 a, 23 bare synchronized with the cameras 12, 12 aand emit a pulsating light. The exposure of the first camera 12 takes place in a time window in which the other camera 12 ais not recording and vice versa. The light sources 23, 23 a, 23 bemend the light as periodic light pulses which are synchronized such that the light sources emit their light exclusively during each exposure phase of the first camera 12 or exclusively during each exposure phase of the second camera 12 a. It is thus possible to record image sequences with completely different illumination situations and later to combine them as desired, mix them or implement them as crossfade.The application examples presented here represent only by way of example a multiplicity of applications of the beam splitter system 1 according to the invention and of an associated illumination device. For example, one or more of the light sources 23, 23 a, 23 bmay be polarized by polarizing filters 24, 24 a, 24 b. If a polarization filter (not shown here) is likewise placed in one of the imaging paths of the cameras 12, 12 a, said polarization filter having a polarization direction rotated by 90°, this camera records a cross-polarized version of the image in which the highlight lights are extinguished.List of reference characters1 Beam splitter system 2 relay unit 3 recording lens 4 aerial image 5 radiation 6 first relay optics 7, 7 abeam splitter element 8, 8 a, 8 bsecond relay optics 9 imaging beam path 10 first imaging path 10 asecond imaging path 10 bthird imaging path 11, 11 a, 11 bsensor 12, 12 a, 12 bcamera 13 beam splitter holder 14, 14 a, 14 bfocus-side mount 15, 15 a, 15 bcamera-side mount 16, 16 afocusing device 18, 18 aimage circle 19 vertical displacement device 20 horizontal displacement device 21, 21 a, 21 bfilter 22, 22 afilter holder 23, 23 a, 23 blight source 24, 24 a, 24 blight source filter 25 sync generator 26 horizontally oriented image window 26 avertical cut-out of horizontal image window 27, 27 adisplayor 28 vertically oriented image window 28 a, Vertically oriented window 28b shifted and reduced vertically oriented window 29 background

Claims

Beam splitter system (1) comprising a recording objective (3), at least two cameras (12, 12') and a relay unit (2) having at least one beam splitter element (7), a first relay optical unit (6) and at least two second relay optical units (8, 8a), characterized in that the recording objective (3) provides a real aerial image (4) which is imaged by the first relay optical unit (6), wherein the at least one beam splitter element (7) divides the imaging beam path (9) of the first relay optical unit (6) into at least two imaging paths (10, 10a), and the at least two second relay optical units (8, 8a) in the at least two imaging paths (10, 10a) each image the aerial image (4) onto a sensor (11, 11a) of the at least two cameras (12, 12a), wherein the focal length of the first relay optical unit (6) does not differ from the focal lengths of the at least two second relay optical units (8, 8a) by more than 10%, and the beam splitter system (1) further comprises a device which is designed to selectively modify the image (4) to be imaged in at least one of the at least two imaging paths (10, 10a).Beam splitter system (1) according to Claim 1, characterized in that the beam splitter element (7) is mounted in the relay unit (2) in a releasable manner in a predefined position in the imaging beam path (9).Beam splitter system (1) according to Claim 1 or 2, characterized in that the beam splitter element (7) splits the imaging beam path (9) of the first relay optical unit (6) according to a predefined intensity ratio and / or according to the polarization of the imaging beam and / or a desired spectral range of the imaging beam.Beam splitter system (1) according to one of the preceding claims, characterized in that the device comprises at least one filter (21, 21a), which is arranged behind the beam splitter element (7) in at least one of the two imaging paths (10, 10a).Beam splitter system (1) according to Claim 4, characterized in that the at least one filter (21, 21a) is arranged such that it can be changed between the beam splitter element (7) and the at least one second relay optical unit (8, 8a).Beam splitter system (1) according to claim 4 or 5, characterised in that the at least one filter (21, 21a) is mounted rotatably about the optical axis of the imaging path and its rotational position can be adjusted from the outside.Beam splitter system (1) according to one of Claims 4 to 6, characterized in that the at least one filter (21, 21a) is a grey filter, a polarization filter and / or a long-pass or short-pass filter.Beam splitter system (1) according to Claim 7, characterized in that the limit wavelength of the long-pass or short-pass filter is in the range from 700 nm - 780 nm.Beam splitter system (1) according to one of the preceding claims, characterized in that the first relay optical unit (6) and the at least two second relay optical units (8, 8a) are designed to transmit an image circle of at least 32 mm diameter.Beam splitter system (1) according to one of the preceding claims, characterized in that the first relay optical unit (6) and the at least two second relay optical units (8, 8a) are designed to transmit a light intensity of at least one aperture 2.Beam splitter system (1) according to one of the preceding claims, characterized in that at least one of the second relay optics (8, 8a) can be displaced and fixed along the optical axis in order to tune the focus of this optics to the sensor plane (11, 11a).Beam splitter system (1) according to Claim 11, characterized in that the displacement of the at least one second relay optical unit (8, 8a) with respect to the other relay optical unit (8, 8a) can be adjusted in such a way that the depth of focus regions of the two receptacles partially overlap.Beam splitter system (1) according to one of the preceding claims, characterized in that the recording objective (3) and / or at least one of the cameras (12, 12a) is connected to the relay unit (2) in a separable manner.Beam splitter system (1) according to Claim 13, characterized in that the recording objective (3) and / or at least one of the cameras (12, 12a) is connected to the relay unit (2) by means of a standard mount.Beam splitter system (1) according to Claim 14, characterized in that the standard mount is a PL or LPL mount.Beam splitter system (1) according to one of the preceding claims, characterized in that the sensors (11, 11a) of the cameras (12, 12a) are synchronized with respect to one another in terms of time.Beam splitter system (1) according to one of the preceding claims, characterized in that the beam splitter system (1) has a displacement device (19, 20) which is designed to displace at least one of the cameras (12, 12a) parallel to its sensor plane in the horizontal and / or vertical direction.Beam splitter system (1) according to one of the preceding claims, characterized in that the beam splitter system (1) has a device which is designed to rotate at least one of the cameras (12, 12a) by 90° about the optical axis with respect to a predefined starting position.Beam splitter system (1) according to one of the preceding claims, characterized in that the sensors (11, 11a) of the cameras (12, 12a) are set such that they record the same image sections and / or have the same exposure times.Beam splitter system (1) according to one of the preceding claims, characterized in that the beam splitter system (1) further comprises an illumination device which is designed to emit light of a predetermined polarization direction and / or light of a specific spectral range and / or pulsating light which is synchronized with the frame rate of at least one camera.

Images