Electronic endoscope, endoscope light source unit, endoscope processor and electronic endoscope system

Abstract

An electronic endoscope system comprising an electronic endoscope (40) and an endoscope light source unit (30), wherein the electronic endoscope (40) comprises an imaging device (43) having a first pixel covered by a first color filter that transmits a first light component that reaches a predetermined depth below an organ wall according to the position of the object to be observed, characterized in that the first light component belongs to one of three primary colors and the imaging device (43) further comprises: - a second pixel covered by a second color filter which transmits a second light component belonging to the same primary color as the first light component and whose wavelength band is different from that of the first light component; - a third pixel covered by a third color filter which transmits a third light component belonging to a primary color different from the primary color of the first light component; and - a fourth pixel covered by a fourth color filter which transmits a fourth light component belonging to a primary color different from the primary colors of the first light component and the third light component, and that the endoscope light source unit (30) comprises: - a light source (31) which emits illuminating light onto an object; - a light source filter (33) which filters out a light component within a predetermined wavelength band from the illumination light; and - a filter drive (34, 35, 36) which introduces the light source filter (33) into the beam path of the illumination light or removes it from it.

Description

[0001] The invention relates to an electronic endoscope, an endoscope light source unit, an endoscope processor and an electronic endoscope system which enable an organ image to be acquired and the acquired image to be displayed.

[0002] It is well known that the depth to which light penetrates beneath an organ wall depends on the wavelength of the light. If light with a short wavelength is irradiated onto an organ and this light only reaches a superficial area beneath the organ wall, the intensity of the light reflected by tissue located in this superficial organ area is comparatively strong, as in Fig. 6 is indicated by the reference symbol "Ts". However, if light with a long wavelength reaches a deeper organ region, the intensity of the light reflected by tissue located in this deep organ region is comparatively strong. This is Fig. 6 is indicated by the reference symbol “Td”.

[0003] If light in a narrow, short-wavelength band is irradiated onto an organ, tissue located in a superficial area beneath the organ wall, such as a capillary vessel, can be clearly visualized. An endoscope system that captures an image of such an organ region advantageously utilizes the property described above. However, such an endoscope system is typically comparatively complex in design. One example of this is an image acquisition system that operates according to the half-frame or partial-frame sequence method.

[0004] Document US 4,885,634 A discloses an endoscope device having a device for generating color image signals for a normal color display from image signals acquired using a solid-state image pickup element under an illumination device covering the visible light range, and output terminals configured to output those image signals based exclusively on specific wavelength components. The endoscope device enables a monochrome image related to a specific wavelength range to be displayed along with a normal color image.

[0005] The document US 2004 / 0186351 A1 discloses a fluorescence endoscope system for simultaneously providing normal light observation based on reflected light and fluorescence observation based on light with wavelengths in the infrared spectrum.

[0006] Document JP 2004-228662 A discloses an image sensor having a plurality of two-dimensionally arranged light-receiving elements. A filter for transmitting light of a specific wavelength band is attached to each of the light-receiving elements. This filter includes four types of filters: a B filter for transmitting light of a blue wavelength band, a G1 filter for transmitting light of a comparatively short green wavelength band, a G2 filter for transmitting light of a comparatively long green wavelength band, and an R filter for transmitting light of a red wavelength band.

[0007] Document US 5 604 530 A discloses a solid-state image sensing device for an endoscope and an endoscopic image pickup device.

[0008] The object of the invention is to provide an electronic endoscope system comprising an electronic endoscope and an endoscope light source unit and an endoscope processor, which enable an image of organ tissue to be recorded and displayed using a comparatively simple structure.

[0009] The invention solves this problem by the subject matter of the independent claims. Advantageous further developments are specified in the subclaims.

[0010] The invention provides an electronic endoscope with an imaging device. The imaging device has a first pixel. The first pixel is covered by a first color filter. A first component penetrates the first color filter. The first light component reaches a depth below an organ wall predetermined according to the position of the object.

[0011] The wavelength of the first light component lies in a wavelength band between 400 nm and 450 nm.

[0012] The invention further provides an endoscope light source unit including a light source, a light source filter, and a filter drive. The light source emits illumination light onto an object. The light source filter filters out a light component within a predetermined wavelength band from the illumination light. The filter drive inserts the light source filter into the beam path of the illumination light. Alternatively, the filter drive removes the light source filter from the beam path.

[0013] A light component whose wavelength is shorter than 550 nm can penetrate the light source filter.

[0014] The invention further provides an endoscope processor with an input unit and a signal processing unit. The input unit detects an input provided by the user, which selects one of a plurality of predetermined display modes. The signal processing unit performs contour enhancement processing only for a pixel signal generated by the first pixel. This processing for contour enhancement of said pixel signal is performed when a display mode for displaying a narrowband image is selected, which constitutes one of the predetermined display modes.

[0015] The invention, along with its features and advantages, is explained below with reference to the figures, in which: Fig. 1 is a block diagram showing the internal structure of an electronic endoscope system including an electronic endoscope, an endoscope light source unit, and an endoscope processor according to an embodiment of the invention; Fig. 2 the spectral characteristics of the light source filter; Fig. 3 the spectral characteristics of the color filters; Fig. 4 the arrangement of the color filters on the receiving surface; Fig. 5 is a flowchart describing the signal processing performed by an endoscope processor to display a standard image or a narrowband image; and Fig. 6 a diagram showing the different depths that light of different wavelengths reaches beneath an organ wall. Description of a preferred embodiment

[0016] The invention is described below using an embodiment with reference to the figures.

[0017] Fig. 1 shows an electronic endoscope system 10 including an endoscope processor 20, an electronic endoscope 40, and a monitor 50. The endoscope processor 20 is connected to the electronic endoscope 40 and the monitor 50. A light source unit 30 is housed in the endoscope processor 20. The light source unit 30 emits light to illuminate an object (not shown). The light emitted by the light source unit 30 is irradiated onto the object via a light guide 41 housed in the electronic endoscope 40.

[0018] An imaging device 43, e.g., a CCD image sensor, is mounted in the tip end of an insertion tube 42 of the endoscope 40. The imaging device 43 captures an optical image of the object. The imaging device 43 then generates an image signal corresponding to the captured optical image. This image signal is sent to the endoscope processor 20. An image signal processing unit 21 is included in the endoscope processor 20. The image signal processing unit 21 processes the image signal in a predetermined manner. The thus processed image signal is sent to the monitor 50. The image is then displayed on the monitor 50 based on the sent image signal.

[0019] The light source unit 30 includes a light source 31, a condenser lens 32, a light source filter 33, a filter drive mechanism 34, a motor 35, and a position detector 36. The light source 31 emits white light. The condenser lens 32 is mounted in the light path leading from the light source 31 to the entrance end of the light guide 41. The condenser lens 32 focuses the light onto the entrance end of the light guide 41, causing the light to fall onto the entrance end.

[0020] The light source filter 33 is held by the filter drive mechanism 34. The filter drive mechanism 34 can move the light source filter 33. In this way, the light source filter 33 can be inserted into and removed from the beam path. The movement of the light source filter 33 is achieved by appropriately controlling the motor 35. The motor 35 is controlled by a system controller 22.

[0021] The filter drive mechanism 34 is equipped with the position detector 36. The position detector 36 detects the position of the light source filter 33. The position of the light source filter 33 is sent to the system controller 22 as a signal from the position detector 36. The system controller 22 controls the motor 35 based on the position of the light source filter 33.

[0022] As in Fig. As shown in Figure 2, the light source filter 33 is made of a material that blocks the red light component and part of the green light component, while transmitting the other part of the green light component and the blue light component. For example, this material transmits light components whose wavelengths are shorter than 550 nm.

[0023] If the light source filter 33 is inserted into the beam path, a portion of the green light component and the blue light component present in the white light fall onto the entrance end of the light guide 41. If, however, the light source filter 33 is removed from the beam path, the entire white light falls onto the entrance end of the light guide 41.

[0024] The insertion and removal of the light source filter 33 begins when the user operates a changeover switch 44 mounted on the electronic endoscope 40. The changeover switch 44 is connected to the system controller 22. The system controller 22 controls the motor 35 according to the user's operation of the changeover switch 44 so that the light source filter 33 is inserted into or removed from the light path.

[0025] The light emitted from the exit end of the light guide 41 illuminates a peripheral area near the tip end of the insertion tube 42 through a diverging lens 45. The imaging device 43 captures an optical image of the illuminated object through an objective lens 46. A driver 23 controls the imaging device 43 to perform a corresponding image capture operation. The imaging device 43 then generates an image signal.

[0026] A plurality of pixels constitute a receiving surface of the imaging device 43. When the imaging device 43 performs the above-mentioned image pickup operation, each pixel generates a pixel signal corresponding to the amount of light received. The image signal thus includes a plurality of pixel signals generated by the pixels.

[0027] Each pixel is covered with a red filter, a green filter, a first blue filter, or a second blue filter. As shown in Fig. As shown in Figure 3, the first blue filter transmits a blue light component whose wavelength lies within a wavelength band of 400 nm to 450 nm (cf. B1). The second blue filter transmits a blue light component whose wavelength lies within a wavelength band of 450 nm to 500 nm (cf. B2). The green filter transmits a green light component whose wavelength lies within a wavelength band of 500 nm to 600 nm (cf. G). The red filter transmits a red light component whose wavelength lies within a wavelength band of 600 nm to 700 nm (cf. R).

[0028] As in Fig. As shown in Figure 4, the red filter (R) and the first blue filter (B1) are arranged repeatedly and alternately, i.e., in a nested manner, along a first column. The green filter (G) and the second blue filter (B2) are arranged repeatedly and alternately (nested) along a second column. The first and second columns are again arranged repeatedly and alternately (nested). Furthermore, the second blue filter is arranged in the same row as the red filter, while the first blue filter is arranged in the same row as the green filter.

[0029] The pixel signal generated by each pixel covered with the corresponding color filter represents a signal corresponding to the amount of the received color light component that passes through the corresponding color filter. Accordingly, a pixel covered with the red filter generates an R signal component corresponding to the amount of the received red light component. A pixel covered with the green filter generates a G signal component corresponding to the amount of the received green light component. A pixel covered with the first blue filter generates a B1 signal component corresponding to the amount of the received blue light component having a specific wavelength. A pixel covered with the second blue filter generates a B2 signal component corresponding to the amount of the received blue light component having a wavelength different from the above-mentioned wavelength.The R, G, B1 and B2 signal components are sent to the image signal processing unit 21.

[0030] When the light source filter 33 is located in the beam path, the intensity level of the R signal component is substantially zero, since in this case the red light component is not radiated onto the object.

[0031] The image signal processing unit 21 includes a first signal processing circuit 24, a second signal processing circuit 25, a narrowband image processing circuit 26 (hereinafter also referred to as NBI circuit), a normal or standard image processing circuit 27 (hereinafter also referred to as NI circuit), and a switching circuit 28.

[0032] The image signal containing the R, G, B1, and B2 signal components is sent to the first signal processing circuit 24. The first signal processing circuit 24 converts the image signal from an analog signal to a digital signal and performs predetermined signal processing on the digital signal.

[0033] The thus processed image signal is sent to either the NBI circuit 26 or the NI circuit 27. The first signal processing circuit 24, the NBI circuit 26, and the NI circuit 27 are connected to a timing controller 29. The timing controller 29 controls the signal processing performed in the first signal processing circuit 24, the NBI circuit 26, and the NI circuit 27, respectively. Furthermore, the timing controller 29 determines whether the first signal processing circuit 24 sends the image signal to the NBI circuit 26 or the NI circuit 27.

[0034] The timing controller 29 is connected to the system controller 22. The system controller 22 controls the operation of the timing controller 29. To change the circuit to which the image signal is sent, the system controller 22 controls the timing controller 29 according to the input made to the change switch 44. In this way, the circuit to which the image signal is sent is determined.

[0035] The NI circuit 27 performs predetermined signal processing on the image signal, such as color separation, white balance, interpolation, gamma correction, and Y / C processing. The B1 and B2 signal components are summed, thereby generating a signal corresponding to the blue light component. The predetermined signal processing is performed on this generated signal corresponding to the blue light component. When the B1 and B2 signal components are summed, the two aforementioned signal components are weighted separately. The weights by which the B1 and B2 signal components are multiplied are modified according to a user input, which the user performs on a control panel (not shown) or on a keyboard 37 connected to the timing controller 29.

[0036] On the other hand, the NBI circuit 26 performs color separation, interpolation, and gamma correction on the image signal. After gamma correction, the NBI circuit 26 performs contour enhancement or edge enhancement processing only on the B1 signal component. Furthermore, the NBI circuit 26 also performs Y / C processing on the B1 signal component (which has previously been contour enhanced), the B2 signal component, and the G signal component. The NBI circuit 26 can also operate to amplify the B1 signal component that has previously undergone contour enhancement, and then use the amplified B1 signal component for Y / C processing instead of the unamplified B1 signal component. A gain factor by which the B1 signal component is amplified can be modified by an input made by the user on the control panel or keyboard 37.

[0037] The image signal to which the NI circuit 27 or the NBI circuit 26 has performed the above-described signal processing is sent to the switching circuit 28. The switching circuit 28 sends the image signal output from either the NI circuit 27 or the NBI circuit 26 to the second signal processing circuit 25.

[0038] The second signal processing circuit 25 converts the transmitted image signal into a composite video signal. The second signal processing circuit 25 also performs predetermined signal processing, such as D / A conversion, clamping, and blanking.

[0039] The thus processed composite video signal is output to the monitor 50. As described above, the imaged object is then displayed on the monitor 50. When white light is irradiated onto the object, a normal or standard image of the object is displayed based on the image signal to which the NI circuit 27 has performed the above-described signal processing. On the other hand, when blue / green light is irradiated onto the object by inserting the light source filter 33 into the light path, a narrow-band image of the object is displayed based on the image signal to which the NBI circuit 26 has performed the above-described signal processing. In the narrow-band image, tissue located at a certain depth below the organ wall is enhanced.

[0040] In the following, with reference to the flow chart according to Fig.5 explains signal processing performed by the endoscope processor 20 for displaying a standard image or a narrowband image.

[0041] In step S100, the entire endoscope system is initialized. During this initialization, the imaging device 43 is enabled to capture an optical image, the light source 31 is enabled to emit white light, and the image signal processing unit 21 is enabled to perform the above-described signal processing.

[0042] After initialization, the process proceeds to step S101. In step S101, it is determined whether the change switch 44 is set to the standard image display mode (hereinafter referred to as the standard image mode) or the narrowband image display mode (hereinafter referred to as the narrowband image mode).

[0043] If the changeover switch 44 is switched to the narrowband image mode, the process proceeds to step S102. In step S102, the light source filter 33 is inserted into the optical path. Then, the process proceeds to step S103. In step S103, the image signal generated by the imaging device 43 is sent to the NBI circuit 26, where the image signal is subjected to narrowband image (NBI) processing. NBI processing represents the signal processing performed by the NBI circuit 26, including the contour enhancement performed only on the B1 signal component.

[0044] After the NBI processing, the process proceeds to step S104. In step S104, the switching circuit 28 switches to the NBI circuit 26 to display the narrowband image.

[0045] If the change switch 44 is set to the standard image mode in step S101, the process proceeds to step S105. In step S105, the light source filter 33 is removed from the optical path of the light emitted by the light source 31. The process then proceeds to step S106. In step S106, the image signal generated by the imaging device 43 is sent to the NI circuit 27, where standard image or NI processing is then performed on the transmitted image signal. NI processing represents the signal processing performed by the NI circuit 27.

[0046] After the NI processing, the process proceeds to step S107. In step S107, the switching circuit 28 switches to the NI circuit 27 to display the standard image.

[0047] After step S104 or S107, the process proceeds to step S108. In step S108, the composite video signal is generated based on the image signal (subjected to NBI processing or NI processing). The composite video signal is then sent to the monitor 50.

[0048] In step S109, it is determined whether an input command to terminate the observation performed by the electronic endoscope 40 is present. If such an input command to terminate is present, the image display processing is terminated. Otherwise, the process returns to step S101. Steps S101 to S109 are repeated until an input command to terminate is present.

[0049] In the above-described embodiment, a specific tissue under the organ wall can be clearly observed without using a rotating color filter used in an image pickup system that uses a field-sequential scanning method. Since the electronic endoscope system 10 employs a single-chip image pickup system rather than a field-sequential scanning system, a high-quality image can be displayed, enabling even more precise diagnosis. Since the entire mechanism provided in the electronic endoscope system 10 is simpler than that of an endoscope system that uses a field-sequential scanning method, the entire mechanism can be simplified, and maintenance and repair can be made relatively easy.

[0050] The following describes the individual functions of the electronic endoscope 40, the light source unit 30 and the endoscope processor 20, which form the electronic endoscope system 10.

[0051] First, the function of the electronic endoscope 40 is described.

[0052] In the above-described embodiment, the electronic endoscope 40 can generate an image signal corresponding to a narrow-band image even when white light is irradiated onto the object. This is because, with a portion of the pixels covered with a color filter that transmits a received light component in a specific wavelength band, a pixel signal can be generated corresponding to the amount of the received light component having that specific wavelength band that reaches a desired depth below the organ wall.

[0053] Specifically, the electronic endoscope can generate a pixel signal corresponding to the amount of a received light component whose wavelength lies within a wavelength band of 400 nm to 500 nm. The light component whose wavelength lies within a wavelength band of 400 nm to 500 nm reaches a depth below the organ wall where capillaries exist. In this way, a precise image of a capillary vessel, which is an important observation target, can be displayed in detail.

[0054] In addition, a pixel covered with the first blue filter can generate a pixel signal corresponding to the amount of a received light component with a wavelength of approximately 420 nm. A light component with a wavelength of approximately 420 nm is most strongly absorbed by hemoglobin. This allows the image of the capillary to be displayed in even greater detail. Furthermore, an image of a bleeding body part can be displayed clearly and distinctly.

[0055] In the above-described embodiment, the electronic endoscope 40 can accurately generate not only an image signal corresponding to a narrowband image but also an image signal corresponding to a normal or standard image. To display a narrowband image, conventionally, only the first or second blue filter is used for an imaging device. With such an imaging device, a standard image cannot be accurately displayed because the blue light component of an object irradiated with white light cannot be fully captured by generating only a pixel signal corresponding to the received light passing through the first or second blue filter.However, as described above, the electronic endoscope 40 can generate image signals corresponding to a precise standard image because the blue light component can be detected by summing pixel signals generated by pixels separately covered by the first and second blue filters.

[0056] Thus, in the electronic endoscope 40 of the above-described embodiment, four pixels arranged in two rows and two columns are each separately covered with the red filter, the green filter, the first blue filter, or the second blue filter. In this way, an image can be displayed that has identical resolutions in the column direction and the row direction.

[0057] In the electronic endoscope 40 according to the embodiment described above, the first blue filter and the second blue filter are used. Light in a wavelength band from 400 nm to 450 nm passes through the first blue filter, so that a capillary vessel located superficially beneath the organ wall, i.e., only a short distance beneath the organ wall, can be imaged. Light in a wavelength band from 450 nm to 500 nm passes through the second blue filter. However, any filters that transmit light in a specific wavelength band can be used, provided this light reaches the depth at which the tissue to be viewed is located beneath the organ wall.

[0058] Furthermore, in the electronic endoscope 40 according to the above-described embodiment, the B1 or B2 signal component may be generated to display a narrow-band image related to the blue light component. However, it is also possible to generate a red or green signal component corresponding to the red or green light component lying in a narrow wavelength band by applying a red or green filter to some pixels that transmits only the red or green light component within the predetermined narrow wavelength band.

[0059] The function of the light source unit 30 is described below.

[0060] In the embodiment described above, tissue lying superficially beneath the organ wall can be observed by detecting the blue light component of the light reflected from the object. Typically, the sensitivity of an imaging device, such as a CCD, to the blue light component is lower than to the red or green light components. Accordingly, to generate an image signal corresponding to a narrowband image obtained with a blue light component, a larger amount of light is preferably irradiated onto the object. On the other hand, with a view to protecting the irradiated organ from damage, such as a burn, it is advantageous to irradiate the organ with as little light as possible.The light source unit 30 used in the above-described embodiment is capable of emitting light from which the red light component, which is primarily responsible for organ damage due to burns, is removed. Thus, even when the light source 31 emits a comparatively high amount of light to display a clear narrow-band image, organ burns can be prevented.

[0061] As described in more detail later, the endoscope processor 20 generates the composite video signal corresponding to a narrowband image based not only on the B1 and B2 signal components, but also on the G signal component. In the prior art, it was difficult to generate B1 and B2 signal components with signal intensities high enough to display a clear and distinct narrowband image without saturating the G signal component. This was because, when white light was irradiated onto the organ, the amount of the blue light component received in the imaging device was smaller than that of the green light component. To solve this problem, the light source unit 30 filters out part of the green light component from the white light emitted by the light source 31.Accordingly, the light source unit 30 is capable of emitting B1, B2, and G signal components in nearly equal amounts of light, so that B1 and B2 signal components with sufficiently high signal intensity can be generated without simultaneously saturating the G signal component.

[0062] In the light source unit 30 of the above-described embodiment, the light component whose wavelength is shorter than 500 nm passes through the light source filter 33. However, other optical filters are also applicable, which enable the imaging device 43 to generate the B1, B2, and G signal components with nearly equal signal intensities.

[0063] The function of the endoscope processor 20 is described below.

[0064] In the prior art, an electronic endoscope system displays a narrowband image in a single color because the narrowband image is generated by irradiating an object exclusively with light within a narrow wavelength band. In contrast, in the above-described embodiment, the endoscope processor 20 generates an image signal corresponding to a narrowband image based on pixel signals that not only correspond to the light quantities of the received light components within a narrow wavelength band but also include the light quantities of other received light components. The endoscope processor 20 is thus capable of displaying a narrowband image more vividly than a conventional endoscope processor.

[0065] On the other hand, if pixel signals corresponding to the light quantities of received light components of a predetermined narrow wavelength band and the light quantities of received light components of a different wavelength band are used simultaneously to display a narrowband image, a conventional endoscope system has so far been unable to display the tissue the user wishes to observe clearly enough due to the different sensitivities of the imaging device used therein to the wavelength bands in question. In particular, the sensitivity to the blue light component is lower than the sensitivities to the red and green light components. Consequently, tissue that primarily reflects the blue light component is invisible in the entire narrowband image.In contrast, in the endoscope processor 20 according to the above-described embodiment, an image signal corresponding to a narrowband image is generated using the B1 signal component, which has undergone contour enhancement processing, as well as other signal components. Thus, a narrowband image can be displayed using other primary color signal components, while clearly displaying the tissue to be observed, such as a capillary vessel.

[0066] In the above-described embodiment, the endoscope processor 20 generates an image signal corresponding to the blue light component based on the B1 and B2 signal components. Accordingly, both a standard image and a narrowband image can be accurately displayed on the monitor.

[0067] In the endoscope processor 20 of the above-described embodiment, the weights by which the B1 and B2 signal components are multiplied can be changed. Accordingly, a standard image with an enhanced color tone can be displayed on the monitor 50.

[0068] In the above-described embodiment, the endoscope processor 20 performs Y / C processing on the B1 signal component (which has previously been contour-enhanced), the B2 signal component, and the G signal component in the NBI circuit 26. However, it is also possible to perform Y / C processing not only on the above-mentioned color signal components but also on the R signal component. The signal intensity of the R signal component is substantially zero when the light source filter 33 is inserted into the optical path in the narrowband image mode, so that the R signal component can be excluded from the Y / C processing in the NBI circuit 26 to save computing time. However, if white light is incident on the object even without using the light source unit 30 and the signal intensity of the R signal component exceeds zero, it is advantageous to also use the R signal component for Y / C processing.

Claims

[1] An electronic endoscope system comprising an electronic endoscope (40) and an endoscope light source unit (30), wherein the electronic endoscope (40) comprises an imaging device (43) having a first pixel covered by a first color filter that transmits a first light component that reaches a predetermined depth below an organ wall according to the position of the object to be observed, characterized by that the first light component belongs to one of three primary colors and the imaging device (43) further comprises: - a second pixel covered by a second color filter which transmits a second light component belonging to the same primary color as the first light component and whose wavelength band is different from that of the first light component; - a third pixel covered by a third color filter which transmits a third light component belonging to a primary color different from the primary color of the first light component; and - a fourth pixel covered by a fourth color filter which transmits a fourth light component belonging to a primary color different from the primary colors of the first light component and the third light component, and that the endoscope light source unit (30) comprises: - a light source (31) which emits illuminating light onto an object; - a light source filter (33) which filters out a light component within a predetermined wavelength band from the illumination light; and - a filter drive (34, 35, 36) which introduces the light source filter (33) into the beam path of the illumination light or removes it from it. [2] Electronic endoscope system according to claim 1, wherein - the imaging device (43) has a first pixel row formed by a repeating and alternating arrangement of the first and third pixels along a first direction, and a second pixel row formed by a repeating and alternating arrangement of the second and fourth pixels along said first direction, and - the first pixel row and the second pixel row are repeatedly and alternately arranged along a second direction perpendicular to the first direction on a receiving surface of the imaging device (43). [3] An electronic endoscope system according to any one of the preceding claims, wherein the wavelength of the first light component is within a wavelength band between 400 nm and 450 nm. [4] The electronic endoscope system according to any one of claims 1 to 3, wherein the wavelength of the second light component is within a wavelength band between 450 nm and 500 nm, the wavelength of the third light component is within a wavelength band between 500 nm and 600 nm, and the wavelength of the fourth light component is within a wavelength band between 600 nm and 700 nm. [5] Electronic endoscope system according to one of the preceding claims, wherein the light source filter (33) is designed to transmit a blue light component or a green light component. [6] An electronic endoscope system according to any one of the preceding claims, wherein the light source filter (33) is configured to transmit a light component having a wavelength shorter than 550 nm. [7] Endoscope processor (20), comprising: - an input unit (44) for detecting an input made by the user, by means of which one of several predetermined display modes for displaying an image recorded with an electronic endoscope (40) of the electronic endoscope system according to one of the preceding claims can be selected; and - a signal processing unit (21) which performs contour enhancement processing only for a pixel signal generated by the first pixel when a narrowband image mode which is one of the predetermined display modes is selected. [8] The endoscope processor (20) according to claim 7, wherein the signal processing unit (21) generates a first image signal including a first color signal component of the first light component by summing the first and second pixel signals generated by the first and second pixels when the imaging device (43) captures an optical image of the object. [9] An endoscope processor (20) according to claim 8, wherein the first and second pixel signals can be weighted separately from one another and the weights by which the first and second pixel signals are multiplied can be changed when summing the first and second pixel signals to generate the first color signal component. [10] Electronic endoscope system according to one of claims 1 to 6, comprising: - an input unit (44) for detecting an input made by the user, by means of which one of several predetermined display modes for displaying an image recorded with the imaging device (43) can be selected; and - a signal processing unit (21) which performs contour enhancement processing only for a pixel signal generated by the first pixel when a narrowband image mode which is one of the predetermined display modes is selected. [11] The electronic endoscope system according to claim 10, wherein the light source filter (33) filters out the fourth light component and a part of the third light component from the illumination light; and wherein the filter drive (34, 35, 36) brings the light source filter (33) into the optical path of the illumination light when the narrowband image mode is selected.

Images