Image acquisition method using autofocus and associated visualization system or image acquisition device

Abstract

Image acquisition method, wherein image data, in particular in the form of a video image data stream, are recorded with a first image sensor (2a) and with a second image sensor (2b) of a visualization system (1) which has an imaging optic (3) with a focusing optic (4) and - wherein, prior to the acquisition of the image data, autofocus is performed by detuning the focusing optics (4), characterized in that - that during autofocus image data from the first and second image sensors (2a, 2b) are evaluated and - that the two image sensors (2a, 2b) are read out at different times during autofocus.

Description

[0001] The invention relates to an image acquisition method in which image data, in particular in the form of a (respective) video image data stream, is acquired separately by each of the two image sensors (i.e., with each image sensor separately) using a first image sensor and a second image sensor of a visualization system (which can, for example, be configured as an endoscopic or microscopic visualization system) which has an imaging optic with a focusing optic. Before the image data is acquired, autofocus is performed by adjusting the focusing optic. For example, image information can thus be acquired with the respective image sensor at at least two measurement times, wherein different working or imaging distances are set at the at least two measurement times using an optical group of the visualization system or the aforementioned imaging optic.

[0002] The invention further relates to an associated visualization system (in particular its image acquisition device), which may in particular comprise an endoscope or a microscope and a camera control unit (CCU). The visualization system / image acquisition device comprises a first image sensor, a second image sensor, an imaging optic with a tunable focusing optic (with which the spatial position of an instantaneous focal plane, which is currently being imaged onto the respective image sensor by the imaging system, can be changed), an image processing unit (for processing image data that is captured / sensorially detected by the respective image sensor), and a controller (for controlling the two image sensors, the focusing optic, and the image processing unit).In this system, the controller is designed and configured to capture image data from each of the two image sensors in an image acquisition mode, specifically in the form of a video image data stream and / or in parallel / simultaneously. If necessary, it can perform autofocus in an autofocus mode before capturing the image data by adjusting the focusing optics. The focusing optics can, for example, comprise axially movable focusing lenses or lens groups, or at least one tunable lens with a variable focal length. The tunable lens can be, for example, a membrane lens and / or an optofluidic lens, or an elastically deformable elastomer lens.

[0003] It is a well-established practice in autofocus systems to cyclically capture images with an image sensor while a focusing lens moves along a path (as uniformly as possible). The resulting images can then be evaluated for sharpness (contrast). After the relevant focus area along the z-axis has been optically scanned in this way (z-scan), the focusing lens can be moved to the position that yielded the highest contrast value, thus capturing the sharpest possible image of the object currently being observed by the system.

[0004] In this approach, the traverse speed of the focus group and the frame rate of the image sensor limit the speed at which autofocus can be performed, or the spatial accuracy / resolution, which corresponds to the sampling distance along the traverse path of the focusing optics between two captured autofocus images.

[0005] If the frame rate is set too low, the distances along the focus path may become too large, and the optimal focus point—that is, the current best-focus plane—may be skipped, meaning it is not correctly located. This can be extremely disruptive for the surgeon, especially when using a visualization system in medical applications. Conversely, if the frame rate is increased too much, the maximum shutter speed drops significantly, resulting in (i) insufficient light reaching the image sensor, (ii) inadequate image quality during autofocus, and / or (iii) increased data transmission and / or (iv) increased image processing requirements.

[0006] WO 2016 055 177 A1 discloses a microscope with a main image sensor and two further separate image sensors arranged in a common plane, the two image sensors serving to implement image-based autofocus. The two image sensors arranged in the same plane scan different planes in the object space, as they are positioned at different distances from a shared imaging optic.

[0007] Based on this, the invention aims to enable improved use of a visualization system as described above and to propose a method and an associated image acquisition device that can reliably and quickly deliver sharp images even with changing working distances between the image acquisition device and the object to be recorded.

[0008] To solve the aforementioned problems, the features of claim 1 are provided according to the invention. In particular, to solve the aforementioned problem in an image acquisition method, wherein image data, especially in the form of a video image data stream, is acquired by a first image sensor and a second image sensor of a visualization system comprising an imaging optic with a focusing optic, and wherein autofocus is performed by detuning the focusing optic prior to the acquisition of the image data, it is proposed that image data from the first and second sensors are evaluated during the autofocus and that the two image sensors are read out at different times during the autofocus. Thus, there is a time offset between the two respective readout times.However, since the focusing optics have continued to adjust during this time interval and thus optically detect a new scanning plane, the respective focus planes that the respective image sensor detects / optically scans at the respective readout time differ in such a case.

[0009] In addition to the staggered readout of the two image sensors, it is also possible for the two image sensors to have different imaging distances relative to the shared imaging optics. For example, the two image sensors can be located at slightly different distances from a shared imaging optic. Due to these different imaging distances, it is possible to achieve that, for a specific misalignment of the focusing optics, different, spatially separated focal planes are detected by the respective image sensors. In other words, for a given misalignment of the focusing optics, the two image sensors then detect different, spatially separated focal planes. In such a case, the two image sensors can even be read out simultaneously.However, even with simultaneous readout, two different focus planes can be optically scanned / captured with the respective image sensor.

[0010] Using autofocus, which can be operated in an autofocus mode, the visualization system can thus automatically and independently focus on a new working distance. The method according to the invention offers the technical advantage that the new focal plane, on which the visualization system must focus, can be found faster and more precisely than previously possible. A phase shift between the two image sensors, which arises from the time-shifted readout and / or the different image distances, can, for example, only be active / maintained during autofocus, such as when the two image sensors are read out with a time shift only in autofocus mode, but not in a subsequent image acquisition mode. However, the phase shift can also persist during image acquisition mode, in which case the phase shift can be compensated for in subsequent image processing, if necessary.

[0011] As a result of autofocus, the focusing optics can be optimally adjusted to the current focus plane. This setting can then be maintained for both image sensors, ensuring that both are sharply focused on the current object / focus plane. This allows both image sensors to deliver sharp images as desired in subsequent image capture modes.

[0012] If, however, the two image sensors have different imaging distances with respect to the imaging optics (optionally as explained above), so that they detect different focal planes for a given adjustment of the focusing optics, a time offset is not absolutely necessary (but is mandatory in the embodiment according to claim 1 of the invention): Because even with simultaneous readout, the two image sensors then each scan different focal planes, as mentioned, which also allows more spatial sampling points along the z-axis (= different z-coordinates of the currently detected focal plane) to be obtained per unit of time compared to a situation in which only one of the two sensors is used for autofocus.

[0013] The method according to the invention can also be applied to three or more image sensors that are read out at different times and / or arranged at different imaging distances, so that each image sensor captures image data from a different (currently set) focus plane. The more image sensors used in the method, the greater the technical effect achieved with regard to accelerating the autofocus (time required to find the best focus plane).

[0014] The image acquisition process can therefore switch back and forth between an autofocus mode, in which a z-scan is performed to find a current best focus plane, and an image acquisition mode. As a result of the autofocus, the focusing optics are adjusted so that they focus on the newly determined position z0 of the current best focus plane (which corresponds to a specific adjustment of the focusing optics). In the subsequent image acquisition mode, this adjustment of the focusing optics can then be maintained until a new autofocus is performed. The restart of the autofocus can be triggered by image processing or evaluation (which, for example, detects insufficient image sharpness) that is continuously performed by a controller of the visualization system, or, for example, by external user input.

[0015] In image acquisition mode, the two image sensors can preferably be read out synchronously; however, a time offset can also be acceptable in image acquisition mode, especially if the respective image data will be fused into a new image anyway using subsequent image processing: For example, in image acquisition mode, a fluorescence image captured with the first image sensor can be overlaid as an "image overlay" onto a white light image recorded with the second image sensor. Another example is stereoscopic images, which are each derived from two individual images taken with the first and second image sensors (preferably at the same time, i.e., synchronously).

[0016] If both image sensors operate at a constant and identical refresh rate during autofocus, the time offset or interval between the first image captured by the first sensor and the second image captured immediately afterward by the second sensor will remain constant. However, if the image sensors operate at different refresh rates, this time interval can change during the autofocus process.

[0017] The closer the capture times of the first and second images are, the smaller the z-distances that can be resolved with autofocus. Conversely, with smaller z-distances, the duration of the z-scan automatically increases for a predefined length in the z-direction that is to be optically and stepwise scanned with autofocus.One possible implementation of the method therefore proposes that the position z0 of the current best focus plane is first roughly determined using both image sensors at a high traverse speed of the focus group and / or at a first (slow) frame rate (first z-scan, performed with both image sensors). Subsequently, to determine z0 (position of the best focus plane) more precisely, a second z-scan, for example a fine scan, is performed again with both image sensors at a slow traverse speed of the focus group and / or at a second frame rate higher than the first. This allows for both speed and accuracy in finding the position.

[0018] In a further advantageous embodiment, it can be provided that during autofocus, the position of a focal plane of the imaging optics is shifted in a z-scan along an optical z-axis by adjusting the focusing optics, in order to set / find an instantaneous best focus plane to be used in the subsequent acquisition of image data. Alternatively or additionally, it can be provided that the autofocus is performed to determine the position z0 of an instantaneous best focus plane. This allows for the recording of reliably sharp images in the subsequent image acquisition mode.

[0019] Alternatively or additionally, the autofocus can be performed to determine an adjustment of the focusing optics corresponding to the current best focus plane. A significant advantage of this is that it reduces the reaction time required for the system to automatically adjust the focus position to changing working distances. This considerably improves the user-friendliness of the visualization system.

[0020] In a further advantageous embodiment, it can be provided that during autofocus, a first image is captured with the first image sensor at time t1 and a second image is captured with the second image sensor at time t2, in particular while the focusing optics are being adjusted, preferably in such a way that the respective positions z1 and z2 of the focus plane differ at times t1 and t2.

[0021] The advantage of this autofocus design is that the effective frame rate available for quickly and accurately finding the best focus plane is increased compared to the frame rate at which the individual image sensors operate. This is because the time offset between the respective capture times, when images are taken with the first and second image sensors during autofocus, results in a sequence of images available for evaluation with shorter intervals between them. This increases the resolution in the z-direction achievable when determining the position z0 of the current best focus plane.

[0022] To determine the current best focus plane, a parameter relevant to autofocus, such as image contrast and / or sharpness of the image sequence captured by the respective image sensor, can be evaluated in a known manner. However, the following autofocus methods can also be used by the visualization system to determine the best focus plane: a) contrast autofocus (a contrast value is used to determine the plane with the highest sharpness); b) phase detection autofocus (by comparing the phase difference between two images). Such approaches can be implemented at the sensor level of each individual image sensor used by the system, provided the respective image sensor supports such a function, or by image analysis of the two images of a stereo system, or, for example, by analyzing two images that are separately captured by the visualization system in different spectral ranges.

[0023] In particular, it can be provided that during autofocus, a sequence of images is captured with both the first and second image sensors, which are then evaluated together to determine the best focus plane. The images of the first and second sequences differ with respect to their respective capture times and / or their respective corresponding focus planes (this corresponds to the z-coordinate on which the focusing optics are focused at the time of capture).

[0024] In a further advantageous embodiment, it can be provided that a time offset t2-t1 between successive measurement times t1 and t2, at which the first image and the second image are each taken, is at least 10%, preferably more than 25%, of a time interval between two directly successive individual images of the first or second image sequence.

[0025] For example, if the frame rate of the first image sequence is a constant 50 Hz, a single image is captured every 20 ms with the first image sensor. The time offset should then be at least 2 ms (10%), but preferably at least 5 ms (25%). The most uniform spatial scanning of the focal planes along the z-axis is achieved in a z-scan performed at a nearly continuous speed when the time offset is approximately or exactly half the time interval between two images when both image sensors are operated at the same frame rate. This ensures that the scanned focal planes exhibit approximately equal spatial distances along the z-axis.

[0026] Preferably, the images in each image sequence can be captured at a constant frame rate. This frame rate can correspond to the maximum frame rate achievable with the respective image sensor at the currently set image resolution.

[0027] In a further advantageous embodiment, it can be provided that, within the autofocus process, a first image sequence is captured with the first image sensor and a second image sequence is captured with the second image sensor. Preferably, to determine the position z0 of the instantaneous best-focus plane, both image sequences are evaluated together, in particular by comparing individual frames of the two image sequences.

[0028] This makes it particularly advantageous, for example by comparing the individual images of the two image sequences, to quickly detect the corresponding best focus plane of the recorded image sequences.

[0029] In a further advantageous embodiment, it can be provided that the recording of the first image sequence is triggered in time by a first synchronization signal and the recording of the second image sequence is triggered in time by a second synchronization signal, wherein the first and the second synchronization signals show a time offset.

[0030] This makes it particularly advantageous, for example, to be able to evaluate the image information at different measurement times.

[0031] Alternatively or additionally, it may be provided that the second synchronization signal is generated by means of a phase shift of a shared synchronization signal.

[0032] For example, it can be implemented that the phase shift is activated during autofocus or permanently used by the sensors and compensated for in subsequent video processing. This can be particularly advantageous, for instance, to make the entire sensor array with at least two sensors behave like a single sensor with a higher frame rate.

[0033] For example, it can also be provided that the first image sensor is triggered with the common synchronization signal (which then serves as the first synchronization signal), while in a second signal path the second synchronization signal is generated from the common synchronization signal by means of a phase shift. A phase shift here can be understood in particular as a time delay of the synchronization signal. A phase shifter device can be designed for this purpose.

[0034] In a further advantageous embodiment, it can be provided that image data recorded during autofocus with the first image sensor and / or with the second image sensor are first adapted via an image processing algorithm before the adapted image data are evaluated within the framework of the autofocus, in particular wherein the image data are adapted with regard to an optical perspective and / or processed in such a way that a comparison of the first and the second image is simplified.

[0035] If the visualization system is designed for stereoscopic vision, for example, so that the first and second image sensors capture an object from (slightly) different spatial directions, the images in each sequence may differ slightly in relation to the scene being observed, such as in terms of image section or perspective / angle. Such deviations can be taken into account when evaluating the two image sequences. For instance, each sequence can be subjected to a separate image processing algorithm that makes the images more comparable, perhaps by comparing only specific sections of the captured images with regard to an evaluation criterion (e.g., "optimal image sharpness").This can, for example, simplify a contrast comparison of the images, which can be advantageous in order to quickly and reliably find the best focus plane.

[0036] This method can, for example, generate a third image sequence from the first and second image sequences, in which the respective images from the first and second sequences follow one another. The third image sequence can then be evaluated to determine the position z0.

[0037] During autofocus, the first sensor can have, or be operated at, a refresh rate that matches the refresh rate of the second sensor. However, different refresh rates can also be used, in which case the time offset between the first images from the first sensor and the second images from the second sensor will vary.

[0038] In a further advantageous embodiment, it can be provided that the adjustment speed of the focusing optics is changed during autofocus, preferably wherein the adjustment speed of the focusing optics is slowed down when passing through the z-scan as the current best focus plane is approached.

[0039] If the refresh rate of both image sensors is kept constant in such a procedure, a higher spatial resolution can still be achieved in the area of ​​the best focus plane when determining the position z0, because with lower adjustment speed and the associated (momentary) lower speed of the z-scan, the spatial distance between the individual focus planes optically scanned by the two image sensors decreases, so that the possible spatial resolution in the z-direction increases.

[0040] Furthermore, it may be provided, for example, that during a process and / or adjustment of the focusing optics, intermediate images are generated by the second or further sensors in relation to the first / other sensors.

[0041] Particularly advantageous, for example, is that increasing the adjustment speed of the optical group allows for a faster sharp image and / or faster evaluation of the recorded image information with regard to the highest contrast, and a faster reaching of an autofocus point.

[0042] In a further advantageous embodiment, it can be provided that the procedure is executed fully automatically by a controller of the visualization system, in particular without user input, especially as soon as the controller independently recognizes that the current image quality of the image data just recorded with the visualization system no longer meets the specified requirements.

[0043] In other words, the controller can be configured to use image analysis of the image data captured in image acquisition mode to detect when the working distance between the visualization system and a currently observed object has changed so significantly that refocusing using autofocus is advisable. In this case, the controller then initiates autofocus mode and performs an autofocus operation. Such refocusing can also be triggered, for example, by sensors that detect a change in the working distance, and / or by an external system, such as an external camera system, and / or by a robotic arm movement (where the robot arm moves the two image sensors and thus changes the working distance).Accordingly, in such a case the controller can interrupt the imaging process (but it does not necessarily have to) and can then perform the autofocus so that image data with sufficient sharpness can be captured again.

[0044] In a further advantageous embodiment, the first image sensor and the second image sensor can be implemented by two non-overlapping, preferably adjacent, areas of an active sensor surface of a single image sensor chip of the visualization system. In such a case, the two sensor surfaces are thus located in one plane and therefore typically at the same imaging distance to the imaging optics. Consequently, the two areas of the single image sensor chip are read out with a time offset during autofocus in order to achieve the advantages of the invention.

[0045] Such a configuration of the method is particularly suitable for a stereoscopic visualization system where a single image sensor (with a correspondingly large format) detects two parallel optical channels / two imaging beam paths used for stereoscopic imaging. In such a case, with a sufficiently large image sensor, one half of the active sensor area can detect a left optical channel and an adjacent second half of the active sensor area detects a right optical channel of the visualization system. In such an application, the time-shifted readout according to the invention can also be used to increase the accuracy and / or speed of the autofocus.In this case, during autofocus (as well as during the subsequent actual imaging), individual images are recorded with the respective area of ​​the single image sensor, but at different times during autofocus, especially while the focusing optics are being adjusted.

[0046] In one design, it may therefore be provided that the two image sensors are used to capture stereoscopic images.

[0047] A particular advantage arises from the fact that the time-shifted readout of the image sensors only takes place during autofocus mode (improved approximation to the best focus plane), while in the context of stereoscopic vision, simultaneous readout of both image sensors can be used to simultaneously obtain image pairs for stereo imaging.

[0048] Alternatively or additionally, the two image sensors can be used to detect spectrally different wavelength ranges. In particular, the imaging beam path of the imaging optics can be split by means of a spectrally selective beam splitter into a first imaging beam path detected by the first image sensor and a second imaging beam path, spatially separate and detected by the second image sensor.

[0049] It should be explicitly mentioned here that both approaches can be combined, meaning that, for example, in stereoscopic imaging, a spectral image and a white light image can be captured simultaneously with a visualization system configured according to the invention. If such a system has, for example, a total of four image sensors (e.g., two monochrome image sensors for capturing respective spectral images and two color image sensors for capturing respective white light images), then, if necessary, all four image sensors can be read out in such a time-shifted manner during autofocus that at a specific capture time, only one of the four image sensors is recording an image. In this way, compared to using only one sensor at its maximum frame rate, an improvement in the spatial resolution of the autofocus of a factor of four can ideally be achieved.

[0050] To solve the aforementioned problem, the features of dependent claim 12, which relates to an image acquisition method, can also be used according to the invention. This method provides that image data (in particular in the form of a video image data stream) are acquired in an image acquisition mode using at least one image sensor of a visualization system which has an imaging optic with a focusing optic, and that autofocus is performed by detuning the focusing optic before the image data is acquired in the image acquisition mode.To solve the aforementioned problem, the invention proposes that during autofocus, the at least one image sensor is read out at different measurement times, and that at each of these measurement times, less image data (particularly due to a reduced color depth compared to the image acquisition mode) is read out and used for evaluation than is read out for individual images in the subsequent image acquisition mode. This fundamental approach can also be applied to the previously described method according to claim 1, i.e., also when using two or more image sensors during autofocus.

[0051] Alternatively or additionally, according to the second alternative of claim 12, the invention provides that the at least one image sensor is operated during autofocus at a first frame rate that is higher than a second frame rate at which the at least one image sensor is operated in the subsequent image acquisition mode. This also reduces the amount of image data, which can then be used to accelerate the autofocus because this reduced image data can be read out and processed more quickly. This is particularly advantageous for systems where computing power is limited.

[0052] In this approach according to claim 12, the frame rate (more precisely, the temporal frequency at which the respective image sensor captures image data for different focal planes) can be increased by reducing the spatial resolution of the image sensor used during autofocus. If, however, an image sensor already supports higher frame rates at the same resolution than those required for subsequent image acquisition (typically 60 Hz), this can be utilized during autofocus. In image acquisition mode, multiple frames can be removed, if necessary, to generate a desired frame rate on the monitor / in the video image data stream.

[0053] When utilizing a higher frame rate compared to image capture mode during autofocus, the image sensor can also be switched to a lower (spatial) resolution to enable an even higher frame rate. It can also be advantageous to operate the image sensor in a so-called "binning mode," where adjacent image elements or image areas, or even individual pixels, are combined in terms of signal processing. This improves the signal-to-noise ratio, with pixel merging occurring row by row, column by column, or block by block. Such approaches can at least partially compensate for the reduced sensitivity of the image sensor that automatically accompanies a higher frame rate. Furthermore, this can further enhance the previously described positive effect on the speed and spatial accuracy of the autofocus.Finally, all of this can be applied to each of the at least two image sensors, provided the system has at least two image sensors that can then be read out with a time delay. However, increasing the frame rate during autofocus can also be used independently with just a single image sensor to speed up the autofocus process.

[0054] In this method according to claim 12, it can also be provided that, by adjusting the focusing optics, the position of a focal plane of the imaging optics in a z-scan is shifted along an optical z-axis in order to set an instantaneous best focus plane. Likewise, the autofocus can also be used here to determine a position z0 of the instantaneous best focus plane and / or an adjustment of the focusing optics that corresponds to the instantaneous best focus plane.

[0055] The autofocus process can be stopped once the z0 position has been determined and / or the focusing optics have been adjusted to the current best focus plane (actual calculation of the z0 value is not strictly necessary). With the focusing optics adjusted in this way, high-quality image data can then be captured in image capture mode.

[0056] A particular advantage of this method is that less data needs to be read out at the respective measurement point during autofocus (= autofocus mode) than during the subsequent actual image capture. This makes it possible to operate at least one image sensor at a higher frame rate during autofocus than during the subsequent actual image capture (image capture mode), thus achieving a higher spatial z-resolution.

[0057] If this method uses two image sensors that, as described above, can be read out at different times during autofocus, each of these image sensors can operate at a higher frame rate than during subsequent image acquisition mode. In other words, during autofocus, each of these two image sensors can operate at a first frame rate that is higher than the second frame rate at which the respective image sensor operates in the subsequent image acquisition mode. And, of course, this approach is also applicable to a visualization system that has only a single image sensor but can simultaneously record at least two different images, for example, for stereoscopic vision, with that single image sensor (e.g., due to a division of the active sensor area into at least two image areas).

[0058] As already mentioned, to determine the position z0 of the current best focus plane, an autofocus value, such as a contrast and / or sharpness of the respective image information captured in the autofocus, can be read out and evaluated.

[0059] In a further advantageous embodiment, it can be provided that the respective image information, which is captured by the at least one image sensor at the different measurement times, is a reduced image information obtained by reading and not reading pixels of the at least one image sensor row by row and / or column by column, in particular alternating.

[0060] This method may therefore only require a single image sensor for autofocus, yet an improvement in autofocus performance can still be achieved. This is because the image sensor in question, which is read out with less image information and / or a higher frame rate in autofocus mode, can thus be one of at least two sensors of the visualization system used (for example, a color image sensor, while the visualization system also has another monochrome image sensor that is operated in parallel with the color image sensor during the actual image capture, for example to capture a spectral image, but is not used for autofocus).

[0061] Reducing the amount of image information to be processed in autofocus mode can be achieved in various ways. For example, the image information determined at the respective measurement time by the at least one image sensor during autofocus can be based on a subset of image pixels of the image sensor. Such a subset can be defined, in particular, by a subset of rows and / or columns of the image sensor and / or by a specific segmentation of the active sensor area of ​​the image sensor.

[0062] The available image information, which defines the maximum image resolution, can be limited by the maximum number of pixels in the sensor array. In such a case, combining several pixels into a larger unit can result in reduced image information. This can be achieved, for example, through "pixel binning," where adjacent pixels are combined, particularly with the help of software, to create a new (virtual) pixel that is essentially the sum of the individual pixels combined. Furthermore, multiple pixels can be combined into a larger unit through techniques such as cropping and / or windowing / framing.All such configurations can lead to a reduction in the image information to be processed in autofocus mode, thus achieving a higher frame rate and therefore a higher spatial resolution in optical scanning and / or faster autofocus (for a given adjustment speed of the focusing optics).

[0063] The inventive approach therefore proposes, in particular, that the image information acquired at the respective measurement time in order to determine the current best focus plane is reduced compared to the image information acquired in the subsequent image acquisition mode with the same sensor. For example, the resolution of the images acquired sensorially with the visualization system, more precisely with the at least one image sensor, during autofocus can be reduced compared to the image resolution used in the subsequent image acquisition mode.

[0064] The visualization system can, for example, include a switching device that enables the autofocus function. If the visualization system has two image sensors, the switching device can be configured to switch at least one of the two image sensors to an autofocus mode in which only a portion of the image information that is generally available to the sensor is read out at a specific measurement point during autofocus. The switching device can also preferably increase the frame rate of the affected image sensor so that images are recorded at shorter intervals during autofocus with that sensor than in the subsequent image capture mode.

[0065] Regarding the visualization system, it should be noted that it can of course have a focus actuator for adjusting the focusing optics and / or a zoom actuator for setting an optical zoom.

[0066] To solve the aforementioned problem, the invention also provides the features of dependent claim 14, which relates to a visualization system. This visualization system can comprise an endoscope or a microscope; it further comprises a first image sensor, a second image sensor, imaging optics with tunable focusing optics, an image processing unit, and a controller. The controller can be configured to record image data, in particular in the form of a video image data stream, with each of the two image sensors in an image acquisition mode, particularly in parallel / simultaneously, and, if necessary, to perform autofocus by detuning the focusing optics before recording the image data in an autofocus mode. It can also be provided, for example, that the controller outputs / transmits recorded image data to an external device.

[0067] To solve the aforementioned problem, it is further proposed according to the invention that the controller is configured to execute a method as previously described and / or claimed herein according to one of claims 1 to 13.

[0068] This visualization system allows for the highly advantageous realization of the previously described benefits of the image acquisition method according to the invention. For example, it makes it possible to implement the aforementioned advantages during endoscopic or stereoscopic procedures, thereby facilitating and increasing the efficiency of the entire procedure because the autofocus is performed robustly and quickly by the system.

[0069] It has already been mentioned that the two image sensors can be spatially separated from each other or can be formed by a respective area of ​​an active sensor surface of a single image sensor chip. Alternatively or additionally, it can be provided that the two image sensors each detect an imaging beam path that is generated by the common imaging optics.

[0070] For example, it is particularly advantageous to use different image sensors. Furthermore, it can be arranged that the two image sensors are connected to a common data stream channel. This allows, for example, rapid movements and / or changes in the captured image to be detected and visualized.

[0071] Alternatively or additionally, it can be provided that the two image sensors detect spectrally different imaging light, in particular after division by means of a spectrally selective beam splitter.

[0072] The two image sensors can, for example, be arranged in relation to their respective imaging optics in such a way that both image sensors detect an identical object plane. An advantage of such a design is that the two imaging optics create two separate optical channels that can be used for stereoscopic imaging (see...). Fig. 14).

[0073] Alternatively or additionally, the two image sensors can be designed to offer different spectral sensitivities. The advantage of this is that different wavelength ranges can then be captured / imaged by the image sensors, and / or that the quality of the image data acquired by the image sensors can be improved, for example, by adapting their spectral sensitivities to each other, and that the wavelength range that can be imaged by the image sensors can be expanded.

[0074] Alternatively or additionally, it may be provided that the two image sensors offer different spatial resolution and / or that the two image sensors offer different refresh rates.

[0075] The invention will now be described in more detail with reference to exemplary embodiments, but is not limited to these embodiments. Further embodiments of the invention can be derived from the following description of a preferred embodiment in conjunction with the general description, the claims, and the drawings.

[0076] In the following description of various preferred embodiments of the invention, elements that are identical in function are given identical reference numerals even if they differ in design or shape.

[0077] It shows: Fig. 1 an autofocus method for finding a best focus plane, as is known from the prior art, Fig. 2 the internal structure of an imaging and focusing optic, as it can be used in a method according to the invention, Fig. 3 a first example of how an image acquisition method according to the invention can be advantageously used in a visualization system with two separate image sensors, Fig. 4 another example of a method according to the invention, Fig. Figure 5 illustrates the essential technical advantages of the AF approach according to the invention. Fig. Figure 6 shows different operating modes in which the respective image sensor of a visualization system according to the invention can be operated in different modes. Fig. Figures 7-9 illustrate different ways of reading out an image sensor of a visualization system according to the invention. Fig. Figure 10 shows a typical application situation in which a visualization system according to the invention can be used effectively, and finally the Fig. 11-16 possible embodiments of visualization systems according to the invention, each of which can be set up to carry out an autofocus method according to the invention.

[0078] Fig. Figure 1 schematically illustrates the situation in which an object 18, for example a specific surgical field, is observed with a visualization system 1 such as a microscope, where the object 18 is currently located at a specific working distance 17 measured from the first optical surface of the system 1. The system 1 visibly features an imaging optic 3 that generates imaging rays which can be recorded / sensorially detected by two different image sensors. In order to record sharp images of the object 18, the system 1 performs an autofocus in a known manner, whereby a focusing lens is detuned such that the instantaneous focal plane 5 (i.e., the plane in object space that is sharply imaged onto the respective image sensor 2 for the given instantaneous position of the focusing lens) shifts along the optical z-axis 6 shown.At the same time, the respective image contrast of the recorded image is electronically measured, so that the image in the lower half of the image is displayed. Fig. The contrast curve shown in Figure 1 shows that a so-called best focus plane 7 exists for object 18 at the z-coordinate z0, which provides the best image contrast. The points on the curve illustrate the different focus planes 5 that were optically scanned by system 1. In such an optical scan to determine the best focus plane, only one image sensor is read out.

[0079] Fig. Figure 2 illustrates how such a z-scan can be implemented optically. As can be seen, during autofocus, a focusing optic 4, as part of a more complex imaging optic 3 (which generates images of the object 18 on the image sensor 2 shown), is detuned by means of a focus actuator 22, which in turn is controlled by a controller 15. The system 1 also has a zoom actuator 21, which allows an optical zoom to be set during imaging. The image contrast values ​​to be determined during autofocus (AF) are determined by an image processing unit 14, which reads the associated image sensor 2 electronically.

[0080] Performing such a Z-scan is complex and therefore takes a certain amount of time. In a specific application situation, such as in Fig. Figure 10 shows when the visualization system 1 is used to observe an operational area and the working distance 17 changes very frequently (as soon as the in Fig. (10 shown robot arm 27, which carries the system 1, is moved), it would be of great advantage to accelerate the autofocus and thus switch back to the actual image recording mode as quickly as possible, in which high-resolution and sharp images of the operating area can then be recorded as a live video stream using the system 1.

[0081] Fig. Figure 3 shows a first example of an image acquisition method or a visualization system 1 designed according to the invention. This system 1 already exhibits, like that of the Fig. 1 two separate image sensors 2a and 2b and an associated imaging optic 3 with a focusing optic 4. With each of the two image sensors 2a and 2b, a respective video image data stream can be generated, i.e. a sequence of images, whereby the individual images can be captured at different times with the respective sensor 2a / 2b.

[0082] Such a system 1 could, for example, be like in Fig. Figure 11 shows a configuration with a proximal first image sensor 2a and a second distal image sensor 2b. Starting from a cover glass 30, which allows oblique viewing, the imaging rays first pass through a complex imaging optic 3 consisting of several rod lenses 32 and then enter a spectrally selective beam splitter 10, which has a spectrally selective mirror surface 31 (cf. Figure 11). Fig. 11) This allows spectrally different images to be recorded with the two image sensors 2a and 2b. For example, the beam splitter 10 can be designed such that image sensor 2a records white light images, i.e., visible wavelengths, while the second image sensor 2b detects invisible spectral images in the near-infrared.

[0083] One can also recognize in Fig. 11, that with the aid of the beam splitter 10 the imaging beam path generated by the imaging optics 3 is split into a first imaging beam path 11a, which is detected by the first image sensor 2a, and into a second imaging beam path 11b, which is detected by the second image sensor 2b. This allows the two image sensors 2a and 2b to each detect spectrally different wavelength ranges.

[0084] The Fig. Figure 12 shows the visualization system 1 of the Fig. Figure 11 shows a view from below. As can be seen, the visualization system 1 has two separate optical channels 34a and 34b, so that each of the two spatially separated image sensors 2a, 2b can sensorially capture stereo images in the respective spectral range.

[0085] The Fig. Figure 13 shows the spectrally selective beam splitter 10 with the internal mirror surface 31 in detail, which is formed by a first prism 33a. The imaging rays generated by the imaging optics 3 enter the first prism 33a through the entrance surface A, with visible wavelengths passing through the mirror surface 31, then through the second prism 33b, and finally exiting at the end surface B. Wavelengths in the NIR range, on the other hand, are reflected by the mirror surface 31 and, after further internal reflection (see Figure 13), exit the first prism 33a. Fig. 11), from the exit surface C of the front prism 33a.

[0086] How to suggest something using the dotted lines in the Fig. In the inventive method, when the autofocus is performed (which occurs before the actual images are captured in the subsequent image acquisition mode), not only image data from the first image sensor 2a but also image data from the second image sensor 2b are evaluated. The two image sensors 2a and 2b are read out alternately and with a time offset from each other, specifically while the focusing optics 4 are being detuned, i.e., while the z-scan is being performed. Therefore, the two image sensors 2a and 2b optically scan different focus planes 5 at different focus distances alternately. The respective step size (compare the block arrow in Fig. 3) chosen to be similarly small as in the example of the Fig. 1, so the number of z-positions that can be optically scanned during the Z-scan approximately doubles, because now two image sensors 2a, 2b are used in parallel.

[0087] As a result, the effective step size (black block arrow) that can be achieved using the method according to the invention is reduced. This allows for a more precise resolution in the z-direction when determining the best focus plane 7. In the lower graph of the Fig. The black dots belong to the first image sensor 2a, while the optical scanning points, which are represented as circles in the graphs, belong to the second image sensor 2b.

[0088] Unlike the state-of-the-art example according to Fig. 1 is used in the example of the Fig. For example, to capture the focal plane 5 at position z1, the first image sensor 2a is read out at time t1, while the subsequent focal plane 5 at position z2 is optically scanned by the second image sensor 2b, which is read out at a different time t2 after the focusing optics 4 have been adjusted accordingly. This results not only in a spatial distance Δz between the two focal planes 5, but also in a temporal offset Δt = t2-t1 between the first image, which is captured with the first image sensor 2a while the focusing optics 4 is focused on position z1, and the second image, captured with the second image sensor 2b while the focusing optics 4 is focused on position z2.

[0089] Not shown in the figures is a further embodiment of the method according to the invention in which both of the Fig. The three image sensors 2a and 2b shown are read out simultaneously, but exhibit a slight spatial offset Δz (e.g., in the z-direction shown) (i.e., they are spatially offset from each other). This means that the image sensors 2a and 2b are positioned at different imaging distances from the imaging optics 3. Therefore, when read out simultaneously, they optically scan spaced focal planes 5. In this case, at each scanning / readout time, two different focal planes 5 are always spatially captured by the two image sensors 2a and 2b. Their spatial separation, taking into account the offset Δz, results from the optical imaging equation. As a result, an equally high spatial resolution can be achieved in determining z0 in this way, similar to the example of... Fig. 3.

[0090] How a comparison of Fig. 1 and Fig. As shown in section 4, the step size of the respective z-scan, which is realized using the respective image sensor 2a / 2b, could also be increased. In this case, despite a step size twice as large (compared to Fig. 1) The same number of z-positions are optically scanned because two image sensors 2a and 2b are now used in parallel but phase-shifted and / or spatially offset from each other when optically scanning the focus planes 5. If, for example, the frame rate is increased and the travel speed of the focus lens 4 is increased in such a case, the Fig. The z-scan shown in section 4 can be performed in a shorter time. This time saving (compared to the approach pursued in the prior art according to Fig. 1, where only a single sensor is used during autofocus or two image sensors are read out simultaneously) is in the Fig. 5 illustrated: Fig. Figure 5 illustrates the time required to perform a complete z-scan and determine the best focus plane 7. The dashed line shows the corresponding curve for the approach according to the invention.

[0091] Fig. Figure 6 illustrates the two different modes in which a visualization system according to the invention can be operated. In normal image acquisition mode, the respective image sensor 2 is exposed for a specific exposure time A and then electronically read out within a specific readout time B. The total time A+B thus corresponds to the time required to capture an image (frame). According to the inventive approach, it can now be provided that when the system 1 switches to AF mode, the image sensor 2, which is used for optically scanning the focus planes 5, is operated at an increased frame rate, as shown in the upper half of the Fig. Figure 6 illustrates this. In this case, the image sensor 2, for example due to its lower resolution, can capture two images within a time span that is normally used to record one image of a continuous video image data stream. It is understood that this also allows for a higher z-resolution or an acceleration of the autofocus even when using only a single image sensor, because the higher frame rate allows either more optical sampling points to be acquired along the z-axis 6 or a certain number of optical sampling points to be traversed more quickly along a predetermined path along the z-axis 6.

[0092] The Fig. Figures 7-9 illustrate how such a higher frame rate can be achieved during autofocus with a typical image sensor 2. In normal image capture mode, the image sensor 2 can, for example, be used as shown in Fig. Figure 7 shows that the sensor can be operated at full resolution, so that all pixels 23 of the image sensor 2 are read out. However, using pixel binning, several pixels 23 can then be combined into pixel areas 24 in autofocus mode. While this reduces the spatial resolution of the image sensor 2, it allows the image sensor 2 to be read out electronically more quickly, thus enabling a higher frame rate during autofocus.

[0093] In addition or alternatively, as in Fig. Figure 9 shows that only a specific area 13 of the image sensor 2 (then, for example, at full resolution) is read out during autofocus. In the example of the Fig. For example, in step 9, outer image areas were ignored (image cropping). This also allows for a higher frame rate from the image sensor. Another option, which can be used additionally or alternatively, is to reduce the color depth with which the image sensor electronically captures images during autofocus. This also speeds up the time it takes to capture images during autofocus. During the actual subsequent image capture, after autofocus has been performed, the color depth can then be increased again, resulting in images with a lower frame rate.

[0094] As in the Fig. 3 and Fig. As indicated in 4, to determine the best focus plane 7 or to adjust the focusing optics 4 as best as possible (in order to produce a sharp image of the object 8), both image sequences 8a and 8b, which are supplied by the first and second image sensors 2a / 2b respectively, are jointly evaluated by an image processing unit 14 of the system 1.

[0095] In the Fig. 3 and Fig. In the four examples shown, the two image sensors 2a, 2b are operated with a phase shift of 180°, resulting in spatially uniform scanning because the focal planes 5 exhibit the same spatial offset on both sides. Such an approach is recommended when the position of the best focus plane is not precisely known.

[0096] Fig. Figure 16 illustrates that even if only a single image sensor chip 16 is present, which is read out during autofocus, an acceleration can already be achieved if the image sensor 2 (e.g. at lower resolution) is read out with an increased frame rate.

[0097] The visualization system according to the invention Fig. Figures 14 (side view) and 15 (bottom view) show, like that of the Fig. 16 only have a single image sensor chip 16. However, during autofocus, the one in the Fig. 14 and Fig. Figure 15 illustrates the left area 13a of the active sensor area 12 of the image sensor chip 16 as a first image sensor 2a and the second area 13b as a second image sensor 2b. If these two adjacent but non-overlapping areas 13a, 13b are read out alternately and with a time delay while the focusing optics 4 are adjusted, images can be recorded with the two areas 13a, 13b each, which optically scan the respective different focal planes 5.

[0098] It should be taken into account that this visualization system 1 also complies with the Fig. 14 and Fig. The sensor 15 has two optical channels 34a and 34b, so that each of the two image areas 13a and 13b can sensorially capture a separate image of the observed object 18 (generated using the respective optical channel 34a / 34b). These separate images differ slightly in perspective with respect to the object 18, which, as is known, can be used in image acquisition mode to capture stereo images. During autofocus, however, these different perspectives can be taken into account by the image processing unit 14, so that even with such slightly differing images, the focal plane 5 for which the best image sharpness can be achieved can be identified.

[0099] With previously known autofocus methods, only one sensor is used for autofocus in a stereo system, which is why such a misalignment of the two images is not a problem. In a stereo system like the one from... Fig. However, it can be exploited that the two image areas 13a and 13b become perspectively congruent as soon as the focal plane is reached.

[0100] It would be conceivable to include in each of the two stereo images (taken with image areas 13a and 13b respectively - cf. Fig. 14) To overlay a circular area or other object (using image processing). These objects / circular areas will then merge once both optical channels are in focus. This reflects the fact that, depending on the system configuration, the focal plane is simultaneously the convergence plane (both optics show (at least approximately) the same image area). However, these two planes can be set differently, either optically or through subsequent image processing.

[0101] Some previously known systems that still use an eyepiece instead of a screen to visualize the observed object area employ a laser coupled into the two optical channels. In the focal plane, and thus also in the convergence plane (the planes are usually adjusted so that they are congruent), two laser points coincide, and the user receives direct visual feedback that the focal plane lies where the two laser beams overlap. According to the invention, this previously known approach can also be artificially generated without the use of a physically present laser by simply superimposing an object onto the image using signal processing. This is because the superimposed objects also overlap in the focal plane.The invention therefore proposes in particular to display a virtual object in both image areas in order to provide direct visual feedback to the user, which allows a conclusion to be drawn about the position of the current focal plane.

[0102] It should also be mentioned that the in the Fig. 14 and Fig. The optics shown in Figure 15 have a division into an image area 13a on the left and an image area 13b on the right (cf. Fig. 14). However, it is quite conceivable and possible not to arrange the two optics / the two optical channels next to each other (i.e., along the y-axis in Fig. 14), but one on top of the other (along the x-axis in Fig. 14). Even in such a case, only a single image sensor can be used, which then has a first active area 13a and a second active area 14a arranged below it, in order to realize a visualization system 1 according to the invention.

[0103] In summary, to accelerate and / or increase the accuracy of an autofocus, it is proposed to read out two image sensors 2a and 2b, each capable of capturing images of an object 18 to be focused, alternately during the autofocus process, so that the respective image data recorded when reading out each image sensor 2a, 2b can be evaluated in order to determine a best focus plane 7 directly or indirectly and to adjust a focusing optic 4 of the associated visualization system 1 accordingly, so that subsequently sharp images of the object 18, preferably in the form of a respective video image data stream, can be recorded with both image sensors 2a and 2b.In addition, or alternatively, it is proposed to operate an image sensor 2a / 2b, which is operated at a certain frame rate during normal image data acquisition, at an increased frame rate / image rate during autofocus in order to accelerate the autofocus (compare . Fig. 3). Reference symbol list 1 Visualization system (especially designed as an endoscope or microscope or macroscope) 2 image sensors 3 Imaging optics 4 Focusing optics 5 Focus level 6 z-axis 7 Best focus level 8 image sequence 9 Synchronization signal (to trigger image capture) 10 spectrally selective beam splitters 11 Imaging beam path 12 active sensor area (out of 2 / 16) 13 area (out of 12) 14 Image processing unit 15 controllers 16 image sensor chip 17 Working distance 18 objects 19 Contrast value 20 focus distance 21 Zoom actuator 22 Focus actuator 23 pixels 24 pixel areas 25 operating tables 26 patients 27 robot arm 28-inch screen 29 Microscope 30 Cover glass 31 spectrally selective mirror surface (out of 10) 32 rod lens 33 prisms 34 optical channels z0 = spatial position of 7

Claims

[1] Image acquisition method, wherein image data, in particular in the form of a video image data stream, are recorded with a first image sensor (2a) and with a second image sensor (2b) of a visualization system (1) which has an imaging optic (3) with a focusing optic (4) and - wherein, prior to the acquisition of the image data, autofocus is performed by detuning the focusing optics (4), characterized by , - that during autofocus image data from the first and second image sensors (2a, 2b) are evaluated and - that the two image sensors (2a, 2b) are read out at different times during autofocus. [2] Image acquisition method according to claim 1, wherein during autofocus, the position of a focus plane (5) of the imaging optics (3) in a z-scan is shifted along an optical z-axis (6) by adjusting the focusing optics (4) in order to set / find an instantaneous best focus plane (7) to be used in the subsequent acquisition of the image data and / or - that the autofocus is performed to determine a position z0 of the instantaneous best focus plane (7) and / or an adjustment of the focusing optics (4) corresponding to an instantaneous best focus plane (7). [3] Image acquisition method according to one of the preceding claims, wherein during autofocus a first image is captured at time t1 with the first image sensor (2a) and a second image is captured at time t2 with the second image sensor (2b), in particular while the focusing optics (4) are being adjusted, - preferably such that the respective positions z1 and z2 of the focal plane (5) differ at times t1 and t2. [4] Image acquisition method according to one of the preceding claims, wherein a time offset t2-t1 between successive measurement times t1 and t2, at which the first image and the second image are respectively taken, is at least 10%, preferably more than 25%, of a time interval between two directly successive individual images of the first or second image sequence. [5] Image acquisition method according to one of the preceding claims, wherein, within the scope of autofocus, a first image sequence (8a) is acquired with the first image sensor (2a) and a second image sequence (8b) is acquired with the second image sensor (2b), - preferably wherein to determine the position z0 of the instantaneous best focus plane (7) both image sequences (8a, 8b) are evaluated together, in particular by comparing individual images of the two image sequences (8a, 8b). [6] Image acquisition method according to one of the preceding claims, wherein the recording of the first image sequence (8a) is triggered in time by a first synchronization signal (9a) and the recording of the second image sequence (8b) is triggered by a second synchronization signal (9b), and wherein - the first and second synchronization signals (9a, 9b) show a time offset and / or wherein the second synchronization signal (9b) is generated by means of a phase shift of a shared synchronization signal (9a). [7] Image acquisition method according to one of the preceding claims, wherein during autofocus, image data acquired with the first image sensor (2a) and / or with the second image sensor (2b) are first adapted by an image processing algorithm before the image data adapted in this way are evaluated within the framework of the autofocus, - in particular where the image data is adjusted with regard to an optical perspective and / or processed in such a way as to simplify a comparison of the first and second images. [8] Image acquisition method according to one of the preceding claims, wherein during autofocus the adjustment speed of the focusing optics (4) is changed, - preferably wherein the adjustment speed of the focusing optics (4) is slowed down when passing through the z-scan as it approaches the instantaneous best focus plane (7). [9] Image acquisition method according to one of the preceding claims, wherein the method is executed fully automatically by a controller of the visualization system (1), in particular without user input, - especially as soon as the controller independently recognizes that the current image quality of the image data just recorded with the visualization system (1) no longer meets the specified requirements. [10] Image acquisition method according to one of the preceding claims, wherein the first image sensor (2a) and the second image sensor (2b) are realized by two non-overlapping, preferably adjacent, areas (13a, 13b) of an active sensor area (12) of a single image sensor chip (16) of the visualization system (1) and wherein the two areas (13a, 13b) of the single image sensor chip (16) are read out at different times during autofocus. [11] Image acquisition method according to one of the preceding claims, wherein the two image sensors (2a, 2b) are used to, - to take stereoscopic images and / or - to detect spectrally different wavelength ranges using sensors, in particular where an imaging beam path of the imaging optics (3) is divided by means of a spectrally selective beam splitter (10) into a first imaging beam path (11a) detected by the first image sensor (2a) and into a second imaging beam path (11b) detected spatially separately by the second image sensor (2b). [12] Image acquisition method, in particular according to claim 1, wherein image data, in particular in the form of a video image data stream, are acquired in an image acquisition mode with at least one image sensor (2a, 2b) of a visualization system (1) which has an imaging optic (3) with a focusing optic (4) - wherein, prior to capturing the image data in image capture mode, autofocus is performed by detuning the focusing optics (4), characterized by , - that during autofocus, at least one image sensor (2a, 2b) is read out at different measurement times, and that at each of these measurement times less image data is read out and used for evaluation than is read out for individual images in the subsequent image acquisition mode and / or - that the at least one image sensor (2a, 2b) is operated during autofocus with a first frame rate that is higher than a second frame rate with which the at least one image sensor (2a, 2b) is operated in the subsequent image capture mode. [13] Image acquisition method according to claim 12, - wherein each image information acquired by the at least one image sensor (2a, 2b) at the different measurement times is a reduced image information obtained by reading and not reading pixels of the at least one image sensor (2a, 2b) row by row and / or column by column and / or block by block, in particular alternating, and / or - wherein a respective image information, which is captured with the at least one image sensor (2a, 2b) at the different measurement times, is captured on the basis of a “binning mode” with the respective image sensor (2a, 2b), in which “binning mode” adjacent image areas or individual pixels are combined in terms of signal technology. [14] Visualization system (1), in particular comprising an endoscope or a microscope, with a first image sensor (2a), a second image sensor (2b), an imaging optic (3) with a tunable focusing optic (4), an image processing unit (14) and a controller (15), - wherein the controller (15) is configured to record image data, in particular in the form of a respective video image data stream, in particular in parallel / simultaneously with each of the two image sensors (2a, 2b) in an image recording mode and, if necessary, to perform an autofocus by detuning the focusing optics (4) before recording the image data in an autofocus mode, characterized by , - that the controller (15) is further configured to perform a method according to one of the preceding claims. [15] Visualization system (1) according to the preceding claim, wherein the two image sensors (2a, 2b) - are spatially separated from each other or - are formed by a respective area (13a, 13b) of an active sensor area (12) of a single image sensor chip (16) and / or - to sensorially detect a respective imaging beam path (11a, 11b) that is generated with the common imaging optics (3) and / or - to sensorially detect and / or spectrally different imaging light, especially after splitting by means of a spectrally selective beam splitter (10). - offer different spectral sensitivity and / or spatial resolution and / or refresh rates.

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