Monitor calibration

Abstract

Method for reproducing digital color images on a monitor (4) in false color representation, - wherein the color images are captured using an image sensor (2) of an endoscopic image acquisition system (1) in a color image acquisition mode (15), - wherein an image processing unit (3) of the image acquisition system (1), which is arranged in a camera control unit (9) mediating between an endoscope (10) of the image acquisition system (1) and the monitor (4), generates respective image signals (8) from the recorded color images, which are supplied to an image signal input (5) of the monitor (4) in order to reproduce the color images live on the monitor (4) in false color representation, - and wherein the image processing unit (3) calculates a respective false color representation of the color images, based on image data recorded with the image sensor (2) and on the basis of at least one stored false color which is assigned to a specific image area, characterized in that - that before the actual reproduction of the color images on the monitor (4) a digital color test image (6) is displayed on the monitor (4) which has at least one stored false color that is used for the false color display, - that a digital image (7) of the color test image (6) displayed on the monitor (4) is captured by means of the image sensor (2) and compared with the original color test image (6), - that, depending on a determined deviation between the image (7) and the original digital color test image (6), at least one color compensation parameter (20) is determined and - that subsequently, in the color image capture mode (15), at least one color compensation parameter (20) is used to adjust the image signals (8) generated in the color image capture mode (15) before these image signals (8) are transmitted to the monitor (4), - so that the image signals (8) are color-adapted to the monitor (4) used, and thus a color-accurate reproduction of the at least one false color stored on the monitor (4) can be achieved.

Description

[0001] The invention relates to a method for displaying (typically digital) color images on a monitor in false color, in which the color images are captured by an image sensor of an endoscopic image acquisition system. For this purpose, the color images captured in a color image acquisition mode are displayed live on a monitor in false color so that the user can view them. An image processing unit of the image acquisition system, which is arranged in a camera control unit that mediates between the endoscope and the monitor, generates respective image signals from the color images. These signals are fed to an image signal input of the monitor to display the color images live on the monitor in false color.For this purpose, the image processing unit calculates a false-color representation of the color images, based on image data captured by the image sensor and on at least one stored false color. In this process, the image signals can be transmitted to the monitor, particularly in the form of video signals.

[0002] Furthermore, the invention relates to an associated endoscopic image acquisition system comprising an image sensor and an image processing unit, wherein the image processing unit is arranged in an associated camera control unit (CCU) and is designed to output an image signal to an external monitor. The image sensor can, for example, be designed as part of an endoscope of the image acquisition system or be arranged in a separate camera head.

[0003] Methods like the one described above are well-known and are used, for example, in endoscopy to display an image captured with an endoscope on a monitor to a surgeon during an operation. Especially when the captured images are color-processed, there is often a desire to ensure that the color settings or distribution on the monitor image are not distorted. Such color-accurate reproduction is particularly important when the surgeon needs to make a decision based on the colors displayed on the monitor, such as identifying the type of tissue being observed with the endoscope, which is marked with fluorescent markers. This is because, as mentioned, the displayed colors may be false colors determined by the camera control unit of the image acquisition system.

[0004] It has now become apparent that when users operate such an endoscopy system with different monitors rather than always using the same one, colors are often not reproduced optimally. This is because the physical properties of the monitor, particularly the color reproduction technology used (OLED, LED, LCD), directly influence the display of the video image and thus the subjective impression of the user viewing the video image on the monitor / display. In other words, different monitors can vary, especially with regard to the color spectrum they can reproduce. Therefore, when using different monitors—without adjusting the video signal, i.e., with a constant video signal—variations occur in the displayed colors, i.e., the subjective color impression, and the tonal curve.The aforementioned color casts or unsatisfactory brightness perceptions can therefore occur if the video signal is not optimally adjusted to the monitor.

[0005] To still achieve accurate color reproduction, it has become common practice to manually adjust settings on the monitor using test patterns, in order to achieve the best possible match between the displayed image and a target specification. However, such a manual adjustment procedure is usually complicated and time-consuming, partly because it requires a thorough knowledge of the monitor's menus for adjusting color reproduction.

[0006] Reproduction methods relevant to the invention are known, for example, from US 10,205,940 B1 and US 2012 0127 324 A1. US 10,205,940 B1 already describes an approach for capturing a test image using a camera. GB 2,503,052 A describes an approach for automatically reading calibration data from a QR code that can be read with an optical scanner, in order to take this data into account during color calibration using an associated color chart that bears the QR code.

[0007] Based on this, the object of the invention is to improve the user-friendliness of a method as described above, in particular by simplifying the described adjustment process on the monitor. A further objective of the invention is to improve the color fidelity and the perceived brightness of the images displayed by the monitor.

[0008] To solve this problem, the features of claim 1 are provided according to the invention for an image reproduction method. In particular, it is thus proposed according to the invention to solve the problem in a method of the type mentioned at the outset that a digital color test image is displayed on the monitor before the actual reproduction of the color images (in color image capture mode) and that this color test image has at least one stored false color which is used for the false color display.Furthermore, it is provided that a digital image of the color test pattern displayed on the monitor is captured by the image sensor of the endoscope of the image acquisition system and compared with the original color test pattern. Depending on the determined deviation between the image and the original digital color test pattern, at least one color compensation parameter is determined. Finally, in color image acquisition mode, this determined at least one color compensation parameter is used to adjust the image signals generated in color image acquisition mode, before these image signals are transmitted to the monitor. As a result, the image signals are color-adapted to the monitor being used, and a color-accurate reproduction of the at least one stored false color on the monitor can be achieved.

[0009] The reproduction of the color test image on the monitor, as well as the determination of at least one color compensation parameter, can be carried out in a test image mode, which may differ from the color image capture mode, as will be explained later.

[0010] The term "capturing the displayed color test image" can be understood here in particular as the sensory capture of the color test image displayed on the monitor by means of an image sensor, especially the image capture system.

[0011] The color test image(s) can be stored, for example, in the internal memory of a camera control unit of the image acquisition system. The camera control unit can transmit the color test image to the monitor for display. This allows the digital image of the color test image displayed on the monitor to be captured, particularly by the image sensor of the image acquisition system.

[0012] The determination or modification of the color compensation parameter can be carried out in particular by an initial calculation or a recalculation.

[0013] This method makes it possible to achieve color-accurate reproduction. This can be understood as reproduction that does not distort the desired color impression intended for the color images, but rather reproduces it without color deviation. In other words, the method can, for example, ensure that a specific false color, assigned to a particular image area (perhaps through appropriate image processing performed by the camera control unit), is reproduced correctly on the monitor, that is, with the lowest possible color deviation.

[0014] The technical advantages of this method lie in the fact that manual monitor adjustment (sometimes also referred to as calibration) by the user is unnecessary for the purpose of accurate color reproduction. In other words, a desired color reproduction can always be achieved on the monitor, regardless of which monitor the user is currently using with the image capture system.

[0015] An image acquisition system configured according to the invention can thus achieve consistently high color reproduction quality with different monitors. The only requirement for this is that the image output of the respective monitor is first measured using the image acquisition system or another camera by applying the described method (by sensorially capturing the color test image displayed on the monitor) and that at least one color compensation parameter is determined in order to optimally adapt the image signals (before transmission to the monitor) to the monitor currently being used with the image acquisition system.

[0016] A characteristic feature of a method according to the invention is that the image signal (which can be, in particular, a video signal) transmitted to the monitor is adjusted based on a determined color compensation parameter, so that the connected monitor displays a desired color image, regardless of the monitor's currently randomly set adjustment parameters. This is because the monitor's currently (randomly) set adjustment parameters (which the user may even have changed manually or unintentionally) are already taken into account (in advance) by the sensor's detection of the color test image displayed on the monitor and are therefore largely irrelevant. Accordingly, manual adjustment of the adjustment parameters can be omitted in the vast majority of cases.

[0017] In other words, the inventive method can produce a color-accurate image reproduction on the monitor used, especially even if no adjustment is made to the monitor itself, since it is often sufficient to simply adjust the image signals using the determined color compensation parameter, which are then transmitted to the monitor for the purpose of image reproduction.

[0018] The method according to the invention can be implemented, for example, with a simple SDI video connection, which is characterized by the fact that no control signals or audio signals, but only a video signal, are transmitted to the monitor. This is because such a connection also allows the image / video signals transmitted from the camera control unit to the monitor to be adjusted before transmission, as described above. In other words, the image transmission interface used between the camera control unit and the monitor to transmit the image signals does not necessarily have to offer the possibility of also transmitting control signals to the monitor. However, such transmission of control signals or adjustment parameters can be provided as an add-on, as will be explained in more detail below.

[0019] The image signal in question can in particular be a video signal, i.e. the image acquisition system can in particular be a video acquisition system, especially an endoscopic one.

[0020] Determining the deviation(s) between the color test image and the captured image can preferably be automated by the image acquisition system itself, in particular by an image processing unit. This unit can, in particular, automatically adjust / calculate at least one color compensation parameter.

[0021] The color test pattern can also include multiple color patches with different colors, allowing for the simultaneous measurement of several colors. Furthermore, an entire series of color test patterns can be used and measured. These color test patterns can, for example, be displayed in rapid succession on the monitor and captured with an image sensor to precisely measure larger color spaces in a short time and determine corresponding color compensation parameters for different colors.

[0022] As will be explained in more detail below, the invention distinguishes between color compensation parameters, monitor parameters, and adjustment parameters: A color compensation parameter, as defined by the invention, can serve to adjust the color of the image signals transmitted to the monitor. Monitor parameters, on the other hand, can be parameters that are currently set in the monitor (and influence the image reproduction) and can be queried by the monitor. Adjustment parameters, in this context, can be understood as setting values ​​that are transmitted to the monitor with the purpose of adjusting / changing the image reproduction on the monitor for a given image signal (in particular, in addition to the prior adjustment of the image signal). A monitor parameter can also be changed by transmitting an adjustment parameter.

[0023] The method according to the invention can be used in particular for the following specific application: In consultation with users, color matrices can be developed to represent the tissue types recorded by the image acquisition system (e.g., endoscopic camera system) using false colors, thus enabling the surgeon to identify different tissue types based on unambiguous colors. For this purpose, a video signal provided by the image acquisition system can be output via a video interface and forwarded to a connected monitor to display the video signal on the monitor. The monitor processes the video signal to generate image data from it, which serves to display individual frames on the monitor.The processing of the video signal by the monitor, as well as the monitor's physical properties, have a significant influence on how the video image is displayed and the resulting subjective color impression for the user. Depending on the monitor being used, colors, the white point, or a tonal curve may not be displayed optimally. In this case, the user will notice a color cast and / or an unsatisfactory brightness impression (i.e., color deviations in the monitor image). If a method according to the invention is used to adapt the image signals to the monitor being used before transmission, such color deviations can be avoided.As a result, the operator always sees a correct representation of the false colors of the color matrix on the monitor, largely independent of which monitor is currently being used with the endoscopic image acquisition system and how this monitor is (randomly) adjusted / calibrated.

[0024] For example, a camera control unit (CCU) of the image acquisition system can automatically determine the image compensation parameter and then automatically adjust the video signal transmitted to the monitor based on this parameter to ensure optimal color reproduction. Manual monitor adjustment by the user can then be avoided or no longer necessary.

[0025] Preferably, the inventive method may include a contrast calibration and / or a tone curve adjustment when adjusting the image signals generated in color image capture mode using at least one color compensation parameter, particularly beforehand. These steps can thus be performed either before determining the at least one color compensation parameter or during the adjustment of the image signals using the determined at least one color compensation parameter. This is because correct contrast and / or tone value reproduction is often a prerequisite for a meaningful subsequent adjustment of the image signals to be transmitted to the monitor. A tone curve can be understood here, in particular, as the relationship between an input color (the original color of a captured object) and the corresponding output color (the reproduction of the input color in the monitor image).In a normal color representation, the tone curve is typically a straight line; however, in a false color representation as intended by the invention, this tone curve can also be non-linear.

[0026] If, for example, the model of the monitor used is precisely known, perhaps due to an electronic query performed by the CCU (e.g., via DDC) or due to a user-selected monitor model from a catalog stored electronically in the image acquisition system, then a first, particularly coarse, pre-correction of the image signals to be output to the monitor can be performed based on this information alone. Following such a query or user input, the method according to the invention can then be applied in a subsequent step (including sensorial detection of a color test image displayed on the monitor) to further correct the monitor's color reproduction, i.e., in particular to perform a final fine-tuning of the color reproduction.However, it can also be provided that manual user input and / or the (especially automatic) electronic query performed by the image acquisition system can be skipped. In this case, the method according to the invention is applied directly, and coarse and fine adjustments are performed automatically in one step by appropriately adjusting the image signals. Such an adjustment of image signals according to the invention can include contrast settings and color adjustments.

[0027] According to the invention, the problem can also be solved by further advantageous embodiments according to the dependent claims.

[0028] For example, the color test image can be displayed on the monitor by feeding it to the image processing unit of the image acquisition system. In particular, the image acquisition system itself can provide the color test image. The image processing unit can then generate corresponding image signals from the color test image, which are transmitted to the monitor to display the color test image. The color test image (or images) can, for example, be stored in the internal memory of the image acquisition system and / or be retrieved by the image acquisition system from an external source. Alternatively, the color test image can also be provided by the user. The only important thing is that the color test image (or a precisely known one) is displayed by the monitor that will later be used with the image acquisition system.

[0029] The image of the color test pattern displayed on the monitor can be captured, for example, by the image sensor of the image acquisition system. Depending on the endoscopy system used, a chip-in-tip endoscope can be employed, whose distally positioned image sensor measures the monitor, or a separate camera head, as used in endoscopes that have only an imaging optic distally and a corresponding relay optic in the endoscope shaft.

[0030] When capturing the color test pattern displayed on the monitor, the image sensor or image acquisition system can preferably be operated in a test pattern mode. This mode may differ from the color image acquisition mode used in normal operation. For example, the test pattern mode may be designed so that the images captured by the image sensor are not transmitted to the monitor, but are instead processed by the image processing unit to determine at least one color compensation parameter. In this case, the normal image transmission chain from the image sensor to the monitor is interrupted, unlike in the normal color image acquisition mode, where the images captured by the image sensor are transmitted to the monitor as image signals and can thus be displayed live on the monitor.

[0031] However, it is also possible to capture the image with a separate image sensor. In this case, the image can subsequently be transferred to the image processing unit. Instead of capturing the color test image displayed on the monitor with the image sensor of the image acquisition system, a separate image sensor / camera can be used. This can be connected to the image acquisition system directly, via an adapter, or using wireless transmission technology (e.g., radio or optical). Specifically, it can be connected to a camera control unit of the image acquisition system to electronically transmit the image to the system.

[0032] Alternatively, it would also be conceivable to use a separate image sensor, connected to the camera control unit via an interface, to measure the display of the test images on the monitor. In both cases, the measurement data from a previously known image sensor (whose exact physical data / properties are known) is transmitted to the camera control unit, which processes this data. The result of this processing is the determination of a deviation between the desired display of the color test image and the actual measured display on the monitor, as produced by the monitor currently connected to the camera control unit. Understandably, this display will vary depending on which monitor is connected to the camera control unit and how that monitor is currently calibrated.

[0033] At least one color compensation parameter can, for example, modify the image signal in such a way as to reduce a color difference that exists between the reproduction of the color test image on the monitor and the (underlying digital) color test image for a user.

[0034] It can further be provided that the image processing unit, particularly in normal color image acquisition mode, generates the image signals taking into account at least one color compensation parameter. In particular, in color image acquisition mode, the determined at least one color compensation parameter can be retained unchanged, for example, regardless of dynamic changes in the color images captured by the image sensor.

[0035] After performing the color test image measurement in a test image mode, the image acquisition system can subsequently switch to or be placed in the normal color image acquisition mode in order to reproduce color-accurate images with the currently connected and just measured monitor based on at least one color compensation parameter determined with the color test image measurement.

[0036] Another variant of the procedure involves determining at least one color compensation parameter and then adjusting an image signal generated from the color test image using this parameter to produce a modified display of the test image on the monitor. Subsequently, the image sensor can capture another image of the modified test image displayed on the monitor, and the determination of the at least one color compensation parameter can be repeated. This involves iteratively performing multiple color compensation parameter determinations based on each color test image measurement. In other words, the steps described above can be repeated iteratively until a termination criterion is met. For example, the iteration can be repeated until the deviation between the displayed image and the original test image falls below a predefined threshold.The original color test image can be used unchanged at all times.

[0037] The approach described above thus involves an additional loop that can be executed during color test pattern measurement to gradually adjust the color error of the color test pattern's reproduction on the monitor by adjusting the image signal transmitted to the monitor. In normal operating mode (color image acquisition mode), the color compensation parameter, or a set of color compensation parameters, determined when the loop is terminated can then be used.

[0038] The method can be further improved if the image sensor is calibrated (particularly by means of white balance) shortly before the image is captured. However, it is preferred if the method according to the invention uses an image sensor that has absolute calibration, which may, for example, have already been performed during the manufacturing of the image sensor. In this case, calibration before capturing the image can be omitted.

[0039] As already explained, at least one color compensation parameter can be, in particular, a set of color compensation parameters. Preferably, such a set includes at least two of the following parameters: color tone value or tone curve; gamma factor for color gamma correction; image contrast; image brightness; color matrix value, in particular HSV value; color correction value; color saturation; color profile; in particular ICC profile; image sharpness. Based on such color compensation parameters, determined from the measurement of the color test image displayed on the monitor, the image signals transmitted to the monitor in color image capture mode can be adjusted even before transmission.For example, if a comparison of the image with the original color test image reveals that the monitor uses a specific, previously known color profile or tone curve, these parameters can be taken into account by the image processing unit when generating the image signals in color image capture mode.

[0040] This can also be achieved by storing a set of pre-defined color reproduction profiles in the camera control unit, each profile characterizing the color reproduction provided by a specific (pre-defined) monitor type. The camera control unit, more precisely the image processing unit, can then select the color reproduction profile that most closely matches the connected monitor from the determined deviation between the image and the original digital color test image, in the sense of a "best-match" selection. The color compensation parameter can then be determined based on the selected best-match color reproduction profile. Thus, when determining at least one color compensation parameter, a stored set of monitor color profiles can be used, each profile characterizing the color reproduction provided by a specific monitor type.Furthermore, based on the determined deviation between the image (and the original digital color test image), one of the stored color reproduction profiles can be selected and used to determine at least one color compensation parameter.

[0041] The adjustment of the image signals fed to the monitor's image signal input to display a color image on the monitor can be achieved, in particular, by adjusting stored look-up tables (LUTs), whose values ​​are taken into account when the image signals are generated (by the image processing unit). For example, such tables can contain output RGB values ​​that are mapped to a specific input RGB value (from a captured image).

[0042] In a method according to the invention, it can further be provided that at least one monitor parameter is queried from the monitor via a communication interface between the image acquisition system and the monitor, for example based on a bidirectional HDMI DDC connection, and that this at least one monitor parameter is taken into account by the image processing unit when generating the image signals. Such a query can be carried out automatically by the image acquisition system, more precisely by the camera control unit, particularly in the described test pattern mode.

[0043] The at least one monitor parameter may include one, but preferably at least two, of the following parameters: manufacturer code, product identification number or serial number, date of manufacture, screen size, preset gamma factor, color characteristic, color space size, screen resolution, timing characteristic, refresh rate, pixel clock, line frequency, product identification.

[0044] It may therefore be provided, in particular, that the color compensation parameter is determined taking into account at least one queried monitor parameter that was queried from the monitor beforehand (especially by the camera control unit).

[0045] Based on at least one (queried) monitor parameter and / or the specified deviation between the image and the color test pattern, a color reproduction profile can be selected from a set of color reproduction profiles stored for various monitors. The image signals can then be generated in color image acquisition mode based on this selected color reproduction profile. It is preferred that the selected color reproduction profile be further / more precisely adapted to the actual monitor used, based on the specified deviation between the image and the color test pattern. This allows the color accuracy of the reproduction on the monitor to be further improved. These process steps can preferably be performed automatically by the image processing unit.The described refinement of a selected color reproduction profile thus enables even better color reproduction, especially when the actual color reproduction profile of the monitor currently in use still shows certain deviations from the selected color reproduction profile (which may correspond to a best match with respect to the monitor currently in use, but does not necessarily have to be identical to the actual color reproduction profile of the monitor currently connected).

[0046] As previously mentioned, the process is designed so that the image processing unit calculates a false-color representation of the color images based on image data captured by the image sensor and on at least one stored false color. Therefore, it is also advantageous that the color test image contains such a stored false color, which is used for the false-color representation. This allows for a very accurate color reproduction of this false color.

[0047] Depending on the deviation between the image and the original color test image, at least one adjustment parameter can be transmitted to the monitor, allowing the monitor's color reproduction to be adjusted for a given image signal. This adjustment can be made in addition to changes to the image signals already made by the image processing unit before they are transmitted to the monitor.

[0048] The at least one adjustment parameter can include one, preferably at least two, of the following parameters: monitor profile, color space, color saturation, contrast, gamma, and backlight. In other words, the camera control unit can be configured to automatically adjust the monitor's adjustment parameters based on the detected deviation, thus changing the color reproduction of a given image signal on the monitor. This is equivalent to manual monitor adjustment by the user, but has the advantage that it can be performed by the image acquisition system itself.

[0049] For example, a so-called Monitor Control Command Set (MCCS) exists, which defines a binary protocol for controlling the properties of a monitor using a host device such as a PC or a camera control unit. Such a protocol can be used, for example, within the scope of the invention to transmit adjustment parameters to the monitor. These adjustment parameters can also be transmitted from the camera control unit to the monitor via a bidirectional interface (e.g., HDMI connection), particularly to modify / adjust the image display on the monitor in addition to adjusting the image signals.

[0050] Another embodiment of the method proposes that the color test pattern be displayed on the monitor as a series of different color test patterns. This can be done within fractions of a second if the sensor recording the color test patterns delivers a sufficiently high frame rate. The color test pattern(s) can also include color bars for determining contrast and / or tonal values. It is also possible that, for example, each of the color test patterns contains only a specific color.

[0051] The color test image, or one of the color test images, can also contain multiple colors, particularly arranged in geometric color fields. In such a case, it is advantageous if the respective color test image contains a geometric structure, for example, a cross, that allows the extraction of the color reproduction of the test image within the image (which can include not only the monitor image but also the surrounding environment) using an image recognition algorithm. Such a structure can still enable this extraction even if the image is blurry.

[0052] Determining the deviation between the image and the color test image can include a plausibility check. For this purpose, the image acquisition system can preferably use an evaluation of image data from the image, in particular a brightness distribution, and / or based on pattern recognition by the monitor in the image, to provide the user with a notification to realign the image sensor and / or the monitor if the plausibility check is negative. This prevents user error when capturing the image and thus avoids faulty color compensation.

[0053] Determining the deviation between the image and the color test pattern can further include a calculation step that performs a time-averaging, particularly to eliminate screen flicker or other variations in image reproduction. Alternatively or additionally, individual defective pixels of the monitor can also be disregarded when determining the deviation, especially by filtering out outlier pixels.

[0054] To solve the problem, the features of independent device claim 14 are also provided according to the invention. In particular, it is thus proposed according to the invention to solve the problem in an image acquisition system of the type described at the outset that the image processing unit of the image acquisition system is configured to adjust the image signal in a color image acquisition mode before transmission to the monitor using a color compensation parameter, which was determined by means of a method according to the invention as described above and / or according to one of method claims 1 to 13.

[0055] Such an image acquisition system can also include at least two monitors, which is advantageous in numerous applications. In this case, the at least two monitors can be connected to and controlled by a central camera control unit (CCU) of the system. Each of the at least two monitors can then be optically measured in test pattern mode using the previously described method according to the invention, in order to determine at least one (monitor-specific) color compensation parameter for each of the at least two monitors in advance. In the subsequent color image acquisition mode, the image signals generated by the image sensor can then be adjusted for the respective monitor based on the (respective) at least one color compensation parameter, even before these (adjusted) image signals are transmitted to the respective monitor.For example, if different monitors are used in the image acquisition system, the reproduction of predefined false colors can be optimized for each monitor, meaning the color error of each monitor can be reduced. This eliminates the need for time-consuming manual adjustment or calibration of each individual monitor.

[0056] Preferably, the image acquisition system, in particular the image processing unit, is configured to execute at least some, but preferably all, of the previously described process (especially automatically). The image acquisition system can guide the user through appropriate (e.g., visual or acoustic) user feedback when capturing the image of the color test pattern displayed on the monitor, particularly when the user captures the image with the image sensor of the image acquisition system. Switching between test pattern mode and normal color image capture mode can be initiated by user input to the image acquisition system. The image processing unit can preferably be arranged in a camera control unit of the image acquisition system.

[0057] Preferably, the camera control unit of the image acquisition system also includes a processing unit for determining at least one color compensation parameter. The camera control unit may also preferably have internal memory in which at least one color test image and / or the described color reproduction profiles are stored.

[0058] The image acquisition system can also be configured to automatically switch off any lighting used in color image acquisition mode when a color test pattern is being transmitted from the camera control unit to the monitor in test pattern mode. This allows the image of the color test pattern displayed on the monitor to be captured by the image acquisition system without distracting light reflections.

[0059] 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.

[0060] 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.

[0061] It shows: Fig. 1 a schematic view of an image acquisition system according to the invention with an attached external monitor, wherein the image acquisition system is currently being operated in a test pattern mode, Fig. 2 a schematic flowchart illustrating individual process steps of an image acquisition method according to the invention, Fig. 3 possible configurations of the connection between the camera control unit of the image acquisition system Fig. 1 and connected monitor Fig. 4 the image acquisition system Fig. 1 during normal color image capture mode and Fig. 5 another image acquisition system with a central camera control unit that can supply two separate monitors A and B with image signals via respective cables.

[0062] The Fig. Figure 4 shows an image acquisition system 1 according to the invention, which includes an image sensor 2 as part of an endoscope 10 and an image processing unit 3 for outputting an image signal 8 to an external monitor 4 connected via a transmission cable 18. In the example of the Fig. 4 The image processing unit 3 is arranged in a camera control unit 9, which mediates between the endoscope 10 and the monitor 4. In the Fig. In the situation shown in Figure 4, the image acquisition system 1 is currently operating in a color image acquisition mode 15, which corresponds to the normal operating mode. In this mode, color images of the object 19 observed with the endoscope 10 are recorded by the image sensor 2 and displayed live as a video on the monitor 4.

[0063] The in Fig. The image signals 8a transmitted via the left transmission cable 18 from the endoscope 10 to the camera control unit 9 are processed by the camera control unit 9, specifically by its image processing unit 3, and converted into processed image signals 8b, which are transmitted via the right transmission cable 18 to the monitor 4 for display to the user. As will be explained in more detail later, the image signals 8b are not only processed but also color-adapted to the monitor 4; that is, the color spectrum of the image signals 8b differs from the original image signals 8a supplied by the endoscope 10.

[0064] The camera control unit 9 also has an internal memory 12 in which a whole series of different and previously known color test images 6a, 6b, 6c are stored.

[0065] By means of user input 24 (cf. Fig. 2) Can the user disconnect the image capture system 1 from the one in Fig. 4. Switch the color image capture mode 15 shown in section 4 to a so-called test image mode 16, which is in Fig. Figure 1 illustrates: In this second mode 16, the user can use the image sensor 2 of the endoscope 10 to record a digital image 7 of the monitor 4 and thus of the live monitor image currently displayed on the monitor 4. To improve the color accuracy of the reproduction of the color images captured by the image sensor 2 on the monitor 4, the invention provides that, before the actual reproduction of the color images on the monitor 4 in color image capture mode 15 (as just illustrated with reference to the Fig. 4 described), first a digital color test image 6, which is stored in the internal memory 12, is displayed on the monitor 4. For this purpose (as described in Fig. (1 illustrated by the arrows) the color test image 6 is obtained from the internal memory 12 and (on the input side) fed to the image processing unit 3, which generates a corresponding image signal 8b from it, which is fed to the image signal input 5 of the monitor 4.

[0066] That means in the Fig. In the example shown, the image acquisition system 1 itself provides the color test image 6. However, it would also be conceivable that the color test image 6 is stored in the monitor 4 or in some other memory that the monitor 4 can access. To carry out the method according to the invention, it is only crucial that a previously known color test image with precisely known color characteristics is displayed on the monitor 4 and subsequently recorded by an image sensor 2. The color test image 6 displayed on the monitor 4 would therefore not necessarily have to be recorded by the image sensor 2 of the image acquisition system 1; rather, it would also be possible to use a separate image sensor for this purpose.

[0067] To obtain more precise information about the color reproduction of monitor 4, the digital image 7 (see the dashed box in) is used. Fig. 1), which was recorded with the image sensor 2 of the endoscope 10 and which - as in Fig. Figure 1 illustrates this – in addition to the environment of the monitor 4 and the monitor 4 itself, the color test image 6' displayed by the monitor 4 is also shown, compared with the original color test image 6 as stored in the internal memory 12. For this purpose, the camera control unit 9 has a processing unit 11, which can retrieve the original digital color test image 6 from the internal memory 12 and the digital image 7 that was just recorded by the image sensor 2. The processing unit 11 then determines at least one color compensation parameter 20 based on a deviation it detects between the image 7 and the original digital color test image 6. The processing unit 11 temporarily stores this determined color compensation parameter 20 in a memory.

[0068] As in Fig. As can be seen in test pattern mode 16, the image transmission chain from image sensor 2 to monitor 4 is interrupted, since the (unprocessed) image signal 8a supplied by image sensor 2 is only fed to the calculation unit 11, but not to the image processing unit 3. The latter merely processes the color test pattern 6, in the form of image signal 8c, in order to generate image signal 8b, which is fed to monitor 4 in test pattern mode 16. Fig. 1 The image processing unit 3 thus generates image signals 8b from the color test image 6, which are transmitted to the monitor 4 to display the color test image 6.

[0069] In the Fig. In the situation shown in section 1, the image acquisition system 1 also switches off the lighting that normally emanates from the endoscope 10 when (as in Fig. 4) Color images are captured in normal color image capture mode 15. This ensures that no disturbing light reflections are observed on the monitor 4 when the color test image 6' displayed on the monitor 4 is recorded with the endoscope 10, as shown in Fig. 1 shown.

[0070] In normal color image capture mode 15, which is in Fig. As illustrated in Figure 4, the image transmission chain is intact, so that the image signals 8a reach the image processing unit 3 of the camera control unit 9 from the image sensor 2. However, a characteristic feature of the image reproduction method according to the invention presented here is precisely that the color compensation parameter 20, which according to Fig. 1 was determined in test pattern mode 16, now subsequently in color image capture mode 15 according to Fig. 4 is used to adjust the image signals 8a generated by the image sensor 2 in this mode 15. This adjustment is performed by the image processing unit 3, which uses the at least one color compensation parameter 20 provided to it by the computing unit 11 in color image acquisition mode 15, as indicated by arrow 20 in Fig. 4 is illustrated.

[0071] During normal operation in color image capture mode 15, the image capture system 1 no longer needs to rely on the color test image 6 (which is still stored in memory 12). As in Fig. As illustrated in Figure 4, the image signals 8a are adapted to the new (color-corrected) image signals 8b with at least one color compensation parameter 20, before the latter are transmitted to the monitor 4 using the right transmission cable 18.

[0072] The in the Fig. 1 and Fig. The image acquisition system 1 shown in Figure 4 is therefore characterized by the fact that its image processing unit 3 is configured to perform the following functions: Fig. In the color image capture mode 15 shown, the image signal 8a supplied by the image sensor 2 is adjusted before transmission to the monitor 4 using the (previously determined and meanwhile stored) color compensation parameter 20, which was determined as described above on the basis of a method according to the invention.

[0073] By adjusting the image signal 8 using the color compensation parameter 20, the latter is modified so that the colors displayed by the monitor 4 correspond much more closely to the colors recorded by the image sensor 2 in color image capture mode 15. In other words, the color difference between the displayed color image and the actual color image captured by the image sensor 2 is reduced. This applies particularly to the color test image 6 when it is displayed as in Fig. 1 shown with the image sensor 2 of the endoscope 10, which is recorded.

[0074] As long as the color monitor 4 is neither replaced nor misaligned, it may be sufficient, for example, to keep at least one previously determined color compensation parameter 20 unchanged in color image acquisition mode 15, so that the image processing unit 3 always adjusts the input image signals 8a in the same way, i.e., in particular, independently of changes in the color images currently being recorded with the image sensor 2. If, on the other hand, the monitor 4 is replaced, the color test pattern 6 can be adjusted by applying test pattern mode 16 (as in Fig. (1 illustrated) are displayed again on the monitor 4, and the inventive method can be repeated to determine an updated color compensation parameter 20 that describes how the new monitor 4 distorts the color reproduction (more or less). Such a procedure is also useful after certain periods of time, since the monitor's color reproduction can change over time, for example, due to aging processes. It is understood that the inventive method makes it possible to improve the color reproduction on the monitor 4 in all these cases without having to access the monitor 4 directly.

[0075] The Fig. Figure 3 shows two possible configurations (a) and (b) for transmitting the image signals 8 from the camera control unit 9 to the monitor 4: In variant (a), the image signals 8 and further control signals 21 for controlling the monitor 4 are transmitted via a single video cable 23, with the signals 8 and 21 being transmitted serially. This is possible, for example, if the camera control unit 9 has a serializer. In variant (b), on the other hand, a separate control line 22 is provided in addition to an image signal transmission line 24, via which control signals 21 can be transmitted in parallel with the image signals 8.

[0076] The method according to the invention can also be used, for example, if no control signals 21 are transmitted from the image acquisition system 1 to the monitor 4. This is because, to adjust the color reproduction on the monitor 4, it is sufficient to adjust the image signals 8 to be transmitted to the monitor 4 using the previously determined color compensation parameter 20 before their transmission. Therefore, direct control of the monitor 4 is not absolutely necessary and can even be omitted entirely.

[0077] Like the dashed line at reference oak 20 in Fig. As illustrated in Figure 1, it can optionally be provided that an image signal 8c, generated from the color test image 6, is adjusted using at least one previously determined color compensation parameter 20 in order to produce an adjusted reproduction 6' of the color test image 6 on the monitor 4. This makes it possible to subsequently capture another image 7 of the adjusted color test image 6'' now displayed on the monitor 4 using the image sensor 2 of the endoscope 10. This adjusted color test image 6'' is then based on an image signal 8b, which was generated from the image signal 8c by the image processing unit 3, taking into account the color compensation parameter 20 (see Figure 1). Fig. 1) This allows the color reproduction on the monitor 4 to be adjusted step by step so that the deviation between the original test image 6 and the actual reproduction 6' on the monitor 4 is gradually reduced.

[0078] The previously described process steps can thus be iteratively executed by the image acquisition system 1, for example until a termination criterion is reached, as described in Fig. Figure 2 shows the process steps described there. A) Start the color calibration by switching to test pattern mode 16; B) Transmitting the test pattern 6 from the camera control unit 9 to the monitor 4; C) Recording the test pattern 6 displayed on the monitor 4 using the image sensor 2 of the endoscope 10 (or using another image sensor); D) Determination of the deviation between the recorded digital image 7 of the color test image 6' displayed on the monitor 4 and the original digital color test image 6 (by the calculation unit 11); E) Determination of at least one color compensation parameter 20 from the determined deviation between image 7 and color test image 6; F) Output of image signals 8b adjusted by means of the color compensation parameter 20 to the monitor 4 in color image capture mode 15;

[0079] As in Fig. As illustrated in Figure 2, the switch between the two modes 15 and 16 can be initiated, for example, by a manual user input 24 at the image acquisition system 1. As the dashed line illustrates, the loop of process features A) to E) can also be executed iteratively (i.e., multiple times) if a termination criterion has not yet been reached in step E), for example, because the determined deviation between the color test image 6 and the image 7 is still too large. As explained previously, during this iterative execution, the image signal 8c generated from the color test image 6 can be adjusted using a previously determined color compensation parameter 20 in order to adjust the display of the test image 6 on the monitor 4 and thus, for example, reduce the color difference between the color test image 6 and the image 7 (which reflects the image reproduction 6' on the monitor 4).

[0080] Another variant provides that the image processing unit 3, when determining at least one color compensation parameter 20, uses a stored set of color reproduction profiles; here, each of the color reproduction profiles characterizes the color reproduction of a specific monitor type. This means that, based on the previously determined deviation between the image 7 and the color test image 6, the image processing unit 3 can determine which of the stored color reproduction profiles best corresponds to the currently connected monitor 4 and thus take this color reproduction profile into account when adjusting the image signals 8 in color image acquisition mode 15.

[0081] With the in Fig. The transmission cable 18 shown in Figure 3 between the camera control unit 9 and the monitor 4 can be used to implement a communication interface 14 between the image acquisition system 1 and the monitor 4, which can be designed, for example, as an HDMI-DDC connection. This enables the image acquisition system 1, more precisely the camera control unit 9, to actively query monitor parameters from the monitor 4 in order to obtain further information about the monitor 4 and thus about its color reproduction. Such monitor parameters can be, for example, a specific manufacturer code, a product identification number, a preset gamma factor, or other color characteristics. Such monitor parameters can be helpful so that the image processing unit 3 can select the profile from the stored color reproduction profiles that best matches the monitor 4 and / or to optimally adapt the image signals 8b to the monitor 4.

[0082] In the method according to the invention, it is particularly preferred if a complete set of color compensation parameters 20 is extracted from the comparison between the color test image 6' recorded as image 7 and the original digital color test image 6. This set is then used to adjust the image signals 8b in the color image acquisition mode 15. For example, look-up tables with color values, such as HSV values, stored in the image processing unit 3 can be adjusted based on the determined deviation between image 7 and the color test image 6 in order to reduce or eliminate the observed color deviation as much as possible. Furthermore, an adjustment of image signals 8 according to the invention can also include, for example, adjusting image contrast, image brightness, or image sharpness.

[0083] In addition to querying monitor parameters, the image processing unit 3 can also be configured to transmit at least one adjustment parameter to the monitor 4 in order to directly modify the color reproduction of the monitor 4, which the monitor 4 generates, for example, for a specific image signal 8 that can correspond to a specific image color. In this case, the image acquisition system 1 actively controls the monitor 4 (especially in addition to adjusting the supplied image signals 8) and thus changes the physical color reproduction of the monitor 4 for a given image signal 8, i.e., the color that the monitor 4 outputs for this image signal 8.

[0084] To enable the most optimal possible adjustment of the color reproduction of the monitor 4, it is also advantageous if a whole series of different color test images 6 are displayed on the monitor 4 and each is examined for deviations using the method according to the invention, for example, in order to determine respective color compensation parameters 20 for different colors. If the respective color test image 6 has a certain geometric structure that can be recognized by the image acquisition system 1 in the image 7, then, for example, by applying simple image recognition algorithms, the color reproduction 6' of the color test image 6 that the monitor 4 generates can be extracted from within the image 7, since the image 7, as in Fig. Figure 1 shows that, in addition to monitor 4, it usually also includes the rest of the surroundings.

[0085] To use test pattern mode 16 according to Fig. To make the process more user-friendly, a plausibility check step can also be performed when determining the deviation between image 7 and color test image 6, which gives the user feedback if the image sensor 2 is not correctly aligned on the monitor 4.

[0086] Furthermore, determining the deviation between image 7 and color test image 6 can also include further calculation steps, such as a time averaging between different images 7 and / or filtering out individual pixels of the monitor 4 that are, for example, recognized as faulty by the image acquisition system 1.

[0087] The Fig. Figure 5 finally shows the possible case in which an image acquisition system according to the invention has at least two separate monitors A and B, which can be operated in parallel / synchronously in color image acquisition mode 15 with optimized color reproduction. For this purpose, as in the Fig. As indicated in section 5, each monitor A and B is first individually measured serially using the image sensor 2, and at least one color compensation parameter 20 is determined for the currently measured monitor 4 based on the respective captured image 7. Once the color compensation parameters 20 have been determined for both monitors A and B, they can then be used in color image capture mode 15 (i.e., when a scene to be displayed on both monitors is recorded with the image capture system 1) to adapt the respective image signals 8aA and 8aB (which are intended for transmission to the respective monitor A / B) into the image signals 8bA and 8bB (as in Fig. 4 for one monitor (illustrated).

[0088] A typical procedure for implementing the method according to the invention could, in the case of Fig. For example, the procedure 5 could look like this: display the respective color test image 6A / 6B on monitors A and B; record a digital image 7 of the respective monitor A; for each monitor A / B: compare the respective recorded image 7A / 7B with the original color test image 6A / 6B and determine the respective deviation; determine at least one color compensation parameter 20 from the respective deviation; use the respective color compensation parameter 20 in normal color image acquisition mode 15 to adjust the respective image signal 8, which is to be transmitted to the respective monitor 4. With such a procedure, the color test images 6A / 6B can be identical or different, depending on which color representation the respective monitor 4 is to be used for. However, even with identical color test images 6, the respective determined deviation and thus the respective (at least one) color compensation parameter 20A / 20B can be different, e.g.if only one of the monitors A / B is misaligned or shows any other deviation in its color reproduction.

[0089] In summary, to improve the color reproduction of color images captured by an image acquisition system 1 in a color image acquisition mode 15 on an external monitor 4, it is proposed that the image acquisition system 1 be switched to a test pattern mode 16, in which the image acquisition system 1 determines at least one color compensation parameter 20 based on at least one sensorially detected / captured digital image 7 of a color test pattern 6 displayed on the monitor 4, and that the image acquisition system 1 is subsequently switched to the color image acquisition mode 15 and, in this color image acquisition mode 15, adjusts image signals 8a, which are generated from color images captured by an image sensor 2 of the image acquisition system 1, based on the color compensation parameter 20 determined in the test pattern mode 16, before these adjusted image signals 8b are transmitted to the monitor 4 (see the Fig. 1 and Fig. 4). Reference symbol list 1 Image acquisition system 2 image sensors 3 Image processing unit 4 Monitor 5 Video signal input 6 Color test image 7 digital image / reproduction (out of 4) 8 Image signal (generated by 3, for transmitting digital images to 4, in particular for transmitting 6) 9 Camera control unit 10 Endoscope 11 Calculation unit 12 GB internal storage 13 Image signal line (for transmitting image signals from 1 / 3 to 4) 14 Communication interface (between 1 and 4) 15 color image capture modes 16 Test pattern mode 17 Imaging optics 18 transmission cables 19 objects 20 color compensation parameters 21 control signals 22 Control line 23 video cables 24 User input (at 1, especially at 10 / 3)

Claims

[1] Method for displaying digital color images on a monitor (4) in false color representation, - wherein the color images are captured using an image sensor (2) of an endoscopic image acquisition system (1) in a color image acquisition mode (15), - wherein an image processing unit (3) of the image acquisition system (1), which is arranged in a camera control unit (9) mediating between an endoscope (10) of the image acquisition system (1) and the monitor (4), generates respective image signals (8) from the recorded color images, which are supplied to an image signal input (5) of the monitor (4) in order to reproduce the color images live on the monitor (4) in false color representation, - and wherein the image processing unit (3) calculates a respective false color representation of the color images, based on image data recorded with the image sensor (2) and on the basis of at least one stored false color which is assigned to a specific image area, characterized by , - that before the actual reproduction of the color images on the monitor (4) a digital color test image (6) is displayed on the monitor (4) which has at least one stored false color that is used for the false color display, - that a digital image (7) of the color test image (6) displayed on the monitor (4) is captured by means of the image sensor (2) and compared with the original color test image (6), - that, depending on a determined deviation between the image (7) and the original digital color test image (6), at least one color compensation parameter (20) is determined and - that subsequently, in the color image capture mode (15), at least one color compensation parameter (20) is used to adjust the image signals (8) generated in the color image capture mode (15) before these image signals (8) are transmitted to the monitor (4), - so that the image signals (8) are color-adapted to the monitor (4) used, and thus a color-accurate reproduction of the at least one false color stored on the monitor (4) can be achieved. [2] Method according to claim 1, wherein the color test image (6) is displayed on the monitor (4) by supplying the color test image (6) to the image processing unit (3) of the image acquisition system (1), - in particular wherein the image acquisition system (1) provides the color test image (6) and the image processing unit (3) generates image signals (8) from the color test image (6) which are transmitted to the monitor (4) to display the color test image (6). [3] Method according to claim 1 or 2, - wherein the image (7) is captured with the image sensor (2) of the image acquisition system (1), preferably wherein the image sensor (2) is operated in a test image mode (16), or - wherein the image (7) is captured with a separate image sensor (2), preferably and transferred to the image processing unit (3). [4] Method according to one of the preceding claims, wherein the at least one color compensation parameter (20) modifies the image signal (8) such that a color difference that exists between the reproduction (6') of the color test image (6) on the monitor (4) and the color test image (6) for a user is reduced and / or - wherein the image processing unit (3), in particular in the color image acquisition mode (15), generates the image signals (8) taking into account the at least one color compensation parameter (20), - in particular, in the color image capture mode (15), the determined at least one color compensation parameter (20) is retained unchanged, especially independently of dynamic changes in the color images captured with the image sensor (2). [5] Method according to one of the preceding claims, wherein, after determining the at least one color compensation parameter (20), an image signal (8c) generated from the color test pattern (6) is adjusted using the at least one color compensation parameter (20) to produce an adapted reproduction (6') of the color test pattern (6) on the monitor (4), - in particular, where a new image (7) of the adapted color test image (6) displayed on the monitor (4) is subsequently taken with the image sensor (2) and the determination of at least one color compensation parameter (20) is repeated, - preferably wherein these steps are iteratively repeated until a termination criterion is reached, in particular until the deviation between image (7) and original color test image (6) falls below a set requirement, - in particular, where the color test image (6) is not changed. [6] Method according to any one of the preceding claims, - where at least one color compensation parameter (20) is a set of color compensation parameters (20), - preferably wherein the set includes at least two of the following parameters: color tone value or tone curve; gamma factor for color gamma correction; image contrast; image brightness; color matrix value, in particular HSV value; color correction value; color saturation; color profile, in particular ICC profile; image sharpness. [7] Method according to any one of the preceding claims, - wherein, in determining the at least one color compensation parameter (20), a stored set of color reproduction profiles is used, each of which characterizes a color reproduction that a particular monitor type provides and - that, based on the determined deviation between the image (7) and the original digital color test image (6), one of the stored color reproduction profiles is selected and used to determine at least one color compensation parameter (20). [8] Method according to one of the preceding claims, wherein at least one monitor parameter is queried from the monitor (4) via a communication interface (14) between the image acquisition system (1) and the monitor (4), for example based on an HDMI DDC connection, and the at least one monitor parameter is taken into account by the image processing unit (3) when generating the image signals (8), - in particular wherein the at least one monitor parameter comprises one, preferably at least two, of the following parameters: manufacturer code, product identification number or serial number, date of manufacture, screen size, preset gamma factor, color characteristic, color space size, screen resolution, timing characteristic, refresh rate, pixel clock, line frequency, product identification. [9] Method according to one of the preceding claims, wherein based on - of at least one monitor parameter and / or - based on the specific deviation between image (7) and color test image (6), a color reproduction profile is selected from a set of color reproduction profiles stored for different monitors, and the image signals (8) are generated on the basis of this selected color reproduction profile, - preferably wherein the selected color reproduction profile is further adapted to the actual monitor (4) used based on the determined deviation between image (7) and color test image (6). [10] Method according to one of the preceding claims, wherein, depending on the deviation between the image (7) and the original color test image (6), at least one adjustment parameter is transmitted to the monitor (4) with which the color reproduction of the monitor (4) can be adjusted for a given image signal (8), in particular in addition to the modification of the image signals (8) by the image processing unit (3), - in particular wherein the at least one adjustment parameter comprises one, preferably at least two, of the following parameters: monitor profile, color space, color saturation, contrast, gamma backlight. [11] Method according to one of the preceding claims, wherein the color test image (6) is displayed on the monitor (4) in the form of a series of different color test images (6) and / or - wherein the color test image(s) (6) or color test images (6) include color bars for determining contrast and / or tonal values, - in particular, where each of the color test images (6) contains only one specific color and / or - wherein the color test image (6) or one of the color test images (6) has / have several colors, in particular arranged in geometric color fields and / or - contains at least one geometric structure, for example a cross, which allows the extraction of the color reproduction (6') of the color test image (6) within the image (7) by means of an image recognition algorithm, preferably even when the image (7) has a blur. [12] Method according to one of the preceding claims, wherein the determination of the deviation between image (7) and color test image (6) comprises a plausibility check step, - preferably wherein the image acquisition system (1) provides the user with a hint to realign the image sensor (2) and / or the monitor (4) based on an evaluation of image data of the image (7), in particular a brightness distribution, and / or on the basis of a pattern recognition of the monitor (4) in the image (7), if the plausibility check is negative. [13] Method according to one of the preceding claims, wherein the determination of the deviation between image (7) and color test image (6) comprises a calculation step, - which implements a time averaging, in particular to eliminate screen flicker or other variations in image reproduction, and / or - the individual defective pixel of the monitor (4), in particular by filtering out outlier pixels, is disregarded when determining the deviation. [14] Endoscopic imaging system (1), which - an image sensor (2) and - an image processing unit (3) for outputting an image signal (8) to an external monitor (4) comprises, - wherein the image processing unit (3) is arranged in a camera control unit (9) which mediates between the endoscope (10) and the monitor (4), and - wherein the image sensor (2) is designed as part of an endoscope (10) of the image acquisition system (1) or is arranged in a separate camera head, characterized by , - that the image processing unit (3) is configured to adjust the image signal (8) in a color image acquisition mode (15) before transmission to the monitor (4) using a color compensation parameter (20) which was determined by a method according to one of the preceding claims 1 to 13. [15] Image acquisition system (1) according to the preceding claim, wherein the image processing unit (3) is arranged in a camera control unit (9) of the image acquisition system (1), - preferably wherein the camera control unit (9) has a calculation unit (11) for determining the at least one color compensation parameter (20) and / or an internal memory (12) in which a color test image (6) is stored and / or - wherein the image acquisition system (1) is configured to automatically switch off any lighting used in color image acquisition mode (15) when a color test image (6) is being transmitted from the camera control unit (9) to the monitor (4).

Images