Electronic endoscope

Abstract

Electronic endoscope, comprising: - a video observation unit (10) having a first image sensor (12A) and a second image sensor (12B); - a light supply device that selectively irradiates an object to be observed with white light and with excitation light; - a first color filter (13A) arranged in a beam path directed toward the first image sensor (12A) and having a spectral transmission characteristic such that it transmits light in a first wavelength range corresponding to the color blue; - a second color filter (13B) arranged in a beam path directed toward the second image sensor (12B) and having a spectral transmission characteristic such that it transmits light in a second wavelength range corresponding to the colors green and red; - a first signal processor (40) which generates standard image video signals corresponding to a standard observation image based on image pixel signals generated by the white light and read out from the first and second image sensors (12A, 12B); - a second signal processor (36) which generates narrowband video signals corresponding to a narrowband image based on image pixel signals generated by the part of the excitation light reflected from the object and read out from the first image sensor (12A); and - a third signal processor (38) which generates autofluorescence video signals corresponding to an autofluorescence image based on image pixel signals generated by the autofluorescence light emitted by the object and read out from the second image sensor (12B).

Description

[0001] The invention relates to an electronic endoscope capable of displaying, in addition to a normal full-color image, an autofluorescence image for diagnosing a pathological change, e.g., cancer, as well as an observation image generated by light whose wavelengths lie in a narrow wavelength band within visible light.

[0002] In addition to a normal full-color image, also referred to as a standard full-color image, an electronic endoscope can display a so-called "narrowband image," which is generated by light in a narrow wavelength range. Capillaries located near the surface of the epithelial layer reflect light of short wavelengths. In contrast, organs located deeper in the epithelial layer reflect light of longer wavelengths. Therefore, using a color filter that transmits light of short wavelengths or long wavelengths, capillaries or organs in the epithelial layer can be clearly displayed in a narrowband image.

[0003] When irradiated with light whose wavelengths are in the ultraviolet range or close to it (hereinafter referred to as "excitation light"), a fluorescent light-based image (hereinafter referred to as an "autofluorescence image") can also be displayed on a monitor. For example, tissue present in the epithelial layer contains a fluorescent substance that emits fluorescent light when irradiated with excitation light (hereinafter referred to as "autofluorescence light"). An object image can be formed on an image sensor by the fluorescent light passing through an objective lens. Since the amount of autofluorescence light emitted by a pathologically changed area or a piece of abnormal tissue is weaker than that emitted by normal tissue, the luminance of the pathologically changed area or the area surrounding it in an autofluorescence image is comparatively small.The pathological change can thus be easily detected by comparing it with the standard full-color image obtained with white light.

[0004] To display the standard image and the narrow-band image, for example, two rotating color filters, each with different color elements, are arranged coaxially along a beam path. The image is generated using the color sequence method. One of the color filters has a spectral transmission characteristic corresponding to human vision, while the other color filter has a spectral transmission characteristic that provides a distribution of several discrete, narrow-band wavelength ranges. When displaying the standard image, the color filters are moved perpendicular to the aforementioned beam path so that one color filter, corresponding to human perception, is positioned in the beam path. When displaying the narrow-band image, the other color filter is positioned in the beam path.In order to display the autofluorescence image, the other color filter mentioned is also replaced by a filter designed for the autofluorescence image.

[0005] Document JP H10-309282 A discloses a fluorescence observation device that generates excitation light in a wavelength range corresponding to the color blue from an excitation light source 6 of a light source 1 and irradiates the excitation light onto an observed part through an endoscope 2. Images of the observed part by means of the fluorescent light and the reflected light are imaged through the endoscope 2 by means of a camera 3. In this case, the fluorescent light image is separated into images of a wavelength range corresponding to the color red and a wavelength range corresponding to the color green, and they are imaged using CCDs 17 and 18. The reflected light image is imaged using a variable-sensitivity CCD 19, the sensitivity of which is adjusted by a sensitivity adjustment device 20. Based on these image signals, image processing is performed at an image processing block 4.By adjusting the intensity of the reflected image in the wavelength range corresponding to the color blue, a normal observation image and a fluorescence observation image whose quality is the same as that of a white light image are generated, and these images are overlapped to be displayed on a display 5.

[0006] Document EP 1 258 221 A2 discloses that, in the light source unit 3A, a switching filter section 14, which switches the RGB filter for normal light observation and a filter for fluorescence observation to the optical path, is arranged in front of the lamp 12. When the fluorescence imaging mode is selected, excitation light in a part of the blue wavelength band is supplied to the electronic endoscope 2A, and the excitation light reflected from the object side is shielded from the CCD 28 by the excitation light cut-off filter 27 to obtain the fluorescence image. The signal of the fluorescence image and the signals of the two reflected light images set in a predetermined wavelength band are passed through the image processing circuit 38, where a matrix circuit is provided for appropriately allocating the color signals of the R, G, and B channels.Thus, the images on the monitor 5 can be displayed in pseudocolors in color tones that allow easy identification of normal tissue and pathologically affected tissue.

[0007] Document US 5 986 271 A discloses a fluorescence imaging system that provides an illuminated image of an object exposed to a fluorescent dye and a fluorescence image of the object.

[0008] Document EP 1 177 761 A2 discloses a fluorescent image display method and an apparatus for carrying out the same.

[0009] The object of the invention is to provide an electronic endoscope system which is capable of displaying a standard full-color image, a narrow-band image and an autofluorescence image sharply and clearly.

[0010] The invention solves this problem by the subject matter of the independent claims. Advantageous further developments are specified in the subclaims.

[0011] An electronic endoscope according to the invention has a video observation unit with a first image sensor and a second image sensor, and a light supply device that selectively emits white light or excitation light onto an object to be observed, e.g., a body part. The electronic endoscope further has a first color filter and a second color filter. The first color filter is arranged in a beam path directed toward the first image sensor and has a spectral transmission characteristic such that it transmits light in a first wavelength range corresponding to the color blue. The second color filter is arranged in a beam path directed toward the second image sensor and has a spectral transmission characteristic such that it transmits light in a second wavelength range corresponding to the colors green and red. The electronic endoscope has a first signal processor, a second signal processor, and a third signal processor.The first signal processor generates standard image video signals corresponding to a standard observation image based on image pixel signals generated by the white light and read from the first and second image sensors. The second signal processor generates narrowband image video signals corresponding to a narrowband image based on image pixel signals generated by the portion of the excitation light reflected from the object and read from the first image memory. The third signal processor generates autofluorescence video signals corresponding to an autofluorescence image based on image pixel signals generated by the autofluorescence light emitted from the object and read from the second image sensor.

[0012] For example, the first wavelength range is set to a range that does not exceed a cutoff wavelength in a range between 450 nm and 550 nm. The second wavelength range is advantageously set to a range that lies above this cutoff wavelength.

[0013] In an advantageous embodiment, a change element is provided for changing the observation mode. This change element is actuated to set a standard observation mode for displaying the standard observation image or a special observation mode for displaying the autofluorescence image and the narrowband image.

[0014] To clearly express a color change, in an advantageous embodiment, the first color filter contains a plurality of first color elements whose spectral distribution curves have different spectral peaks. Accordingly, the second color filter can contain a plurality of second color elements whose spectral distribution curves have different spectral peaks. For example, the first color filter contains three color elements with spectral peaks distributed at equal intervals from one another. The second color filter contains, for example, two or three color elements with spectral peaks distributed at equal intervals from one another.

[0015] To obtain the standard observation image, the narrowband image, and the autofluorescence image using a single optical system, for example, a single objective optical system that generates an object image and a beam splitter can be provided. The beam splitter splits the light passing through the objective optical system into light in the first wavelength range and light in the second wavelength range. An object image is generated on the first image sensor by the light in the first wavelength range, while an object image is generated on the second image sensor by the light in the second wavelength range.

[0016] When using two lenses, however, a first lens lens, for example, is provided, which generates an object image on the first image sensor, and a second lens lens, which generates an object image on the second image sensor. An edge filter, for example, is arranged on the front side of the second lens lens. The edge filter blocks the light in the first wavelength range.

[0017] In another advantageous embodiment, a single light source is provided. The light source emits white light with a spectral distribution extending across the wavelength range of visible light. In this case, an excitation light color filter and a filter driver can be provided. The excitation light color filter transmits light in a wavelength range corresponding to the excitation light. The filter driver selectively positions the excitation light color filter in the beam path or outside the beam path. For example, the filter driver positions the excitation light color filter in the beam path when a standard observation mode is set to display the standard observation image. In contrast, the filter driver positions the excitation light color filter outside the beam path when a special observation mode is set to display the autofluorescence image and the narrowband image.

[0018] When using a laser, however, a white light source that emits white light with a spectral distribution extending over the wavelength range of visible light, a laser that emits the excitation light, optics that direct the excitation light into the beam path of the white light, and a laser driver that switches the laser on and off are provided.

[0019] In a preferred embodiment, a fourth signal processor is provided that processes the autofluorescence video signals and the narrowband image video signals such that the autofluorescence image and the narrowband image can be displayed separately and simultaneously on a monitor. When using a single monitor, for example, a fifth signal processor can be provided that selectively outputs the standard image video signals or a set consisting of the narrowband image video signals and the autofluorescence video signals.

[0020] The invention is described below using preferred embodiments with reference to the figures. In these figures: Fig. 1 is a block diagram of an electronic endoscope showing a first embodiment; Fig. 2 the spectral transmission characteristic of a first color filter; Fig. 3 the color element arrangement of the first color filter; Fig. 4 the spectral transmission characteristic of a second color filter; Fig. 5 the color element arrangement of the second color filter; Fig. 6 the spectral transmission characteristic of a blue filter; Fig. 7 the spectral distribution of the light passing through the blue filter; Fig. 8 the spectral distribution of the autofluorescence light; Fig. 9A and Fig. 9B Screen images on the monitor; Fig. 10 is a flowchart of a main process performed by a video processor; Fig. 11 a timing diagram related to the main process; Fig. 12 is a block diagram of an electronic endoscope showing a second embodiment; Fig. 13 the spectral distribution characteristics of a laser; Fig. 14 the spectral transmission characteristic of an edge filter; Fig. 15 shows the spectral transmission characteristic of a second color filter according to the second embodiment; and Fig. 16 the color element arrangement of the second color filter. Description of preferred embodiments

[0021] Preferred embodiments are described below with reference to the figures.

[0022] Fig. 1 is a block diagram of an electronic endoscope according to a first embodiment. The electronic endoscope has a video observation unit (videoscope) 10 and a video or image processor 30. A monitor 70 is connected to the video processor 30. The video observation unit 10 is detachably attached to the video processor 20.

[0023] In the video processor 30, a lamp 32, e.g., a xenon lamp, emits white light. The spectral distribution of the white light is essentially uniform and extends across the visible light range. The white light emitted by the lamp 32 enters an entrance surface 14a of a light guide 14 via a converging lens 34. The light guide 14 is an optical fiber bundle provided in the video observation unit 10. The light guide 14 guides light to the distal end of the video observation unit 10. The light emerging from the light guide 14 is emitted from the distal end of the video observation unit 10 via a diverging lens 16. In this way, the observed body part is illuminated. Light reflected from the observed body part passes through an objective lens 18 into a dichroic prism 20, which is arranged in the end of the video observation unit 10.

[0024] The dichroic prism 20 splits the reflected light into light with wavelengths greater than 500 nm corresponding to the blue color, and light with wavelengths equal to or less than 500 nm corresponding to the green and red colors. The light corresponding to the blue color is directed to a first CCD 12A, while the light corresponding to the green and red colors is directed to a second CCD 12B.

[0025] A first color filter 13A, which transmits light in a first wavelength range, is arranged on the front side of a light-receiving surface of the first CCD 12A. In contrast, a second color filter 13B, which transmits light in a second wavelength range, is arranged on the front side of a light-receiving surface of the second CCD 12B. A CCD driver 17 outputs clock pulse signals of a predetermined frequency to the first and second CCDs 12A and 12B, so that image pixel signals are sequentially read out from the first and second CCDs 12A and 12B, respectively. The image pixel signals read out from the CCD 12A are supplied to a narrowband signal processor 36 and a standard image signal processor 40. In contrast, the image pixel signals read out from the CCD 12B are supplied to an autofluorescence signal processor 38 and the standard image signal processor 40.In the present embodiment, the method using a chip-integrated color filter is used as the image generation method.

[0026] In the standard image signal processor 40, based on the image pixel signals supplied from the first CCD 12A and the image pixel signals supplied from the second CCD 12B, video signals conforming to a video standard (hereinafter referred to as "standard image video signals"), such as NTSC signals, are generated to display a normal full-color image or standard full-color image. In the narrowband signal processor 36, based on the image pixel signals read out from the CCD 12A, video signals for displaying the narrowband image (hereinafter referred to as "narrowband image video signals" or "NBI video signals" for short) are generated. Then, in the autofluorescence signal processor 38, based on the image pixel signals read out from the CCD 12B, video signals for displaying the autofluorescence image (hereinafter referred to as "autofluorescence video signals") are generated.Amplification is performed in the autofluorescence signal processor 38 because the intensity of the autofluorescence radiation is weak.

[0027] A blue filter 48 is a plate-shaped filter that only transmits excitation light. A motor 46 moves the blue filter 48 so that it is selectively inserted into and removed from the beam path.

[0028] A mode button 19 is provided on the video observation unit 10 for changing the observation mode. Thus, a standard observation mode, in which the standard or normal image is displayed, or a special observation mode, in which the autofluorescence image and the narrowband image are displayed, can be selectively set. When the mode button 19 is pressed, a detection signal is supplied to a system control circuit 44.

[0029] A video signal circuit (switching circuit) 42 selectively outputs the standard image video signals generated in the standard image signal processor 40 or two video signals: the NBI video signals generated in the narrowband signal processor 36 and the autofluorescence video signals generated in the autofluorescence signal processor 38. The system control circuit 44 controls the video processor 30 and outputs control signals to a CCD driver 17, the video signal circuit 42, the lamp 32, and other system components. The system control circuit 44 receives data containing information about the video observation unit 10 and stored in a ROM 15 of the video observation unit 10.

[0030] With reference to the Fig. 2 to 9, the characteristics of the first and second color filters 13A and 13B are explained below.

[0031] Fig. 2 shows the spectral transmission characteristic of the first color filter 13A. Fig. 3 shows the color element arrangement of the first color filter 13A.

[0032] As in Fig. 3, three color elements B1, B2 and B3 are arranged in a checkerboard array. In Fig. Figure 2 shows the spectral distribution curves of the three color elements B1, B2, and B3, which have their spectral maximum values ​​or peaks at 420 nm, 450 nm, and 480 nm, respectively, and each have a specified wavelength range. The wavelength ranges or bands of the color elements B1, B2, and B3 are set to ranges approximately from 400 nm to 440 nm, approximately from 430 nm to 470 nm, and approximately from 460 nm to 500 nm, respectively. The adjacent distribution curves partially overlap.

[0033] Fig. 4 shows the spectral transmission characteristic of the second color filter 13B. Fig. 5 shows the color element arrangement of the second color filter 13B.

[0034] As in Fig. As shown in Figure 5, the three color elements G, O, and R are arranged in a checkerboard array. Fig. Figure 4 shows the spectral distribution curves of the three color elements G, O, and R, which have their spectral peaks at 540 nm, 600 nm, and 660 nm, respectively, and each have a specified wavelength range. The wavelength ranges or bands of the color elements G, O, and R are set to ranges approximately from 500 nm to 580 nm, approximately from 560 nm to 640 nm, and approximately from 620 nm to 700 nm, respectively. The adjacent distribution curves partially overlap.

[0035] In standard observation mode, the blue filter 48 is moved out of the beam path. Consequently, white light emitted by the lamp 32 enters the light guide 14 directly, and the reflected light entering the dichroic prism 20 is separated into light with wavelengths greater than 500 nm and light with wavelengths equal to or less than 500 nm. Since the first color filter 13A transmits light with wavelengths greater than 500 nm and the color filter 13B transmits light with wavelengths equal to or less than 500 nm (see [Fig. 13A]), the first color filter 13A transmits light with wavelengths equal to or less than 500 nm. Fig. 2 and Fig. 4), image pixel signals corresponding to the color blue are generated in the first CCD 12A by mixing a series of image pixel signals related to the color elements B1, B2 and B3, while image pixel signals corresponding to the color green and red are generated in the second CCD 12B.

[0036] Then, in the standard image signal processor 40, standard image video signals are generated based on the image pixel signals read from the first CCD 12A and the image pixel signals read from the second CCD 12B. The video signal circuit 42 outputs the standard image video signals to the monitor 70. The standard observation image is thus displayed on the monitor 70.

[0037] Fig. 6 shows the spectral transmission characteristics of the blue filter 48. Fig. 7 shows the spectral distribution of the light passing through the blue filter 48, ie the excitation light. Fig. Figure 8 shows the spectral distribution of the autofluorescence light.

[0038] In the special observation mode, the blue filter 48, which is used in Fig. 6, is arranged in the beam path. Consequently, light with the spectral transmission characteristic shown in Fig. 7, ie, light in a wavelength range from 400 nm to 500 nm, is radiated onto the observed body part in the form of “excitation light”. The autofluorescence light is emitted from the observed body part, which Fig. 8 has the spectral distribution characteristic shown.

[0039] As in Fig. 1, the reflected part of the excitation light is directed by the dichroic prism 20 onto the first CCD 12A and passes through the first color filter 13A. The first color filter 13A has the Fig. 2. In contrast, the autofluorescence light is emitted at wavelengths in the range of approximately 500 nm to 700 nm (cf. Fig. 8) is directed through the dichroic prism 20 onto the second CCD 12A and passes through the second color filter 13B (cf. Fig. 4). Thus, image pixel signals corresponding to the narrowband image are generated in the first CCD 12A, and image pixel signals corresponding to the autofluorescence image are generated in the second CCD 12B.

[0040] In the narrowband signal processor 36, the NBI video signals are generated based on the image pixel signals read from the first CCD 12A. In contrast, in the autofluorescence signal processor, the autofluorescence video signals are generated based on the image pixel signals read from the second CCD 12B. In the video signal circuit 42, image processing is performed on the NBI video signals and the autofluorescence video signals to display the narrowband image and the autofluorescence image simultaneously and separately. The processed video signals are output to the monitor 70.

[0041] The Fig. 9A and Fig. 9B show screen images on the monitor 70. In Fig. 9A shows a screen on which the standard observation image is displayed. In Fig. Figure 9B shows a screen displaying the narrowband image and the autofluorescence image.

[0042] Fig. 10 is a flowchart showing the main process performed in the video processor 30. Fig. Figure 11 shows a timing diagram related to this main process.

[0043] In step S101, an initialization is performed for each individual circuit by turning on the power supply. In step S102, it is determined whether the standard observation mode has been selected by pressing the mode button 19.

[0044] If it is determined in step S102 that the standard observation mode is selected, the process proceeds to step S106, in which the blue filter 48 is moved out of the optical path. Then, in step S107, the standard image video signals are generated in the standard image signal processor 40. In step S108, the video signal circuit 42 is switched to output the standard image video signals to the monitor 70.

[0045] If, however, it is determined in step S102 that the special observation mode is selected, the process proceeds to step S103, where the motor 46 drives the blue filter 48 to move it into the beam path. In step S104, the NBI video signals and the autofluorescence video signals are generated in the narrowband signal processor 36 and the autofluorescence signal processor 38, respectively. In step S105, the video signal circuit 42 is switched to output the NBI video signals and the autofluorescence video signals to the monitor 70.

[0046] In the first embodiment, the dichroic prism 20, the first CCD 12A with the first color filter 13A, and the second CCD 12B with the second color filter 13B are arranged in the end piece 10A of the video observation unit 10. The first color filter 13A transmits only light with wavelengths equal to or less than 500 nm. This produces the blue components in the standard image video signals and also the narrowband image video signals. The second color filter 13B transmits only light with wavelengths greater than 500 nm. This produces the blue components and red components in the standard image video signals. Furthermore, the autofluorescence video signals are also obtained. Since the chip-integrated color filter method (and not the color sequence method like the RGB sequence method) is used, the image to be viewed can be displayed clearly and distinctly without the image becoming blurred or fuzzy by means of a simple construction.In addition, the narrowband image and the autofluorescence image are displayed separately.

[0047] As in Fig. As shown in Figure 2, in the first color filter 13A, the three spectral peaks of the three color elements B1, B2, and B3 are distributed at equal distances from each other. Thus, a subtle color change can be clearly displayed in the narrowband image, whereby the colors in the observed body part can be faithfully reproduced. Similarly, in the second color filter 13B, the three spectral peaks of the three color elements G, O, and R are distributed at equal distances from each other, as shown in Figure 2. Fig. 4 shows. This allows a subtle color change to be displayed in the autofluorescence image.

[0048] With reference to the Fig. A second embodiment is described below with reference to Figures 12 to 15. The second embodiment differs from the first embodiment in that a laser and a color filter consisting of two color elements are used.

[0049] Fig. 12 is a block diagram of an electronic endoscope according to a second embodiment. A video observation unit (videoscope) 10' has a first CCD 12'A and a second CCD 12'B arranged parallel to each other so as to face the observed body part. Furthermore, the video observation unit 10' has a first objective lens 18'A and a second objective lens 18'B, which face the first CCD 13'A and the second CCD 13'B, respectively. The objective lens 18'B is covered with a cut-off filter CF, which blocks the excitation light. A processor 30' includes a half mirror 35, a laser 47, and a laser driver 49.

[0050] Fig. Figure 13 shows the spectral distribution characteristics of the laser 47. The laser 47 emits light consisting of three light components with spectral maximum values ​​or peaks at 408 nm, 445 nm and 488 nm, respectively, as shown in Fig. 3. This spectral distribution characteristic corresponds to the spectral transmission characteristic of a color filter 13'A, which in turn corresponds to the spectral transmission characteristic of the color filter 13A provided in the first embodiment (cf. Fig. 2). The semi-transparent mirror 35, arranged between the lamp 32 and the converging lens 34, transmits the white light emitted from the lamp 32 to the entrance surface 14a of the light guide 14. Furthermore, the semi-transparent mirror 35 reflects the light or laser beam emitted by the laser 47 and directs it onto the entrance surface 14a of the light guide 14. Fig. 14 shows the spectral passband characteristics of the edge filter CF. As in Fig. As shown in Figure 14, the CF filter only transmits light with wavelengths greater than 500 nm. The reflected portion of the excitation light is thus blocked by the CF filter.

[0051] Fig. 15 shows the spectral transmission characteristic of the second color filter 13'B. Fig. 16 shows the color element arrangement of the second color filter 13'B. As in Fig. As shown in Figure 16, the color filter 13'B consists of color elements G and R arranged in a checkerboard pattern. The spectral transmission characteristic results from the Fig. 15, which have a maximum value at a wavelength of 550 nm and at a wavelength of 650 nm, respectively.

[0052] If the standard observation mode is selected, the laser 47 is controlled so that it does not emit a laser beam. The observed body part is illuminated by the light emitted by the lamp 32. In the CCD 12'A, light of a short wavelength, namely light corresponding to the color blue (B), reaches the light-receiving surface through the color filter 13'A, which is the same as the first color filter 13A according to the first embodiment (see FIG. Fig. 2). In contrast, in the CCD 12'B, light of long wavelength, namely light corresponding to the colors green (G) and red (R), reaches the light receiving surface through the edge filter CF and the second color filter 13'B (cf. Fig. 14 and Fig. 15). Similarly to the first embodiment, the standard image video signals are generated in the standard image signal processor, and the standard observation image is displayed on the monitor 70.

[0053] If the special observation mode is selected, the laser 47 is activated and the lamp 32 is turned off, so that the body part being examined is irradiated with the laser beam. The reflected light is blocked by the edge filter CF, and the second color filter 13'B only transmits light with a wavelength greater than 500 nm (see Fig. Fig. 15). In contrast, the color filter 13'A transmits light with a wavelength shorter than 500 nm, namely the reflected part of the excitation light (cf. Fig.2). The reflected portion of the excitation light thus reaches the light-receiving surface of the first CCD 12'A, while the autofluorescence light reaches the light-receiving surface of the second CCD 12'B. Similar to the first embodiment, the NBI video signals and the autofluorescence video signals are generated in the narrowband signal processor 36 and the autofluorescence signal processor 38, so that both the narrowband image and the autofluorescence image are displayed on the monitor 70.

[0054] Optionally, the first color filter can also be designed to transmit light with a short wavelength, corresponding to the color blue. The second color filter can be designed to transmit light with medium and long wavelengths, corresponding to the colors green and red. The number of color elements can be specified as desired.

Claims

[1] Electronic endoscope comprising: - a video observation unit (10) having a first image sensor (12A) and a second image sensor (12B); - a light supply device that selectively irradiates an object to be observed with white light and with excitation light; - a first color filter (13A) arranged in a beam path directed toward the first image sensor (12A) and having a spectral transmission characteristic such that it transmits light in a first wavelength range corresponding to the color blue; - a second color filter (13B) arranged in a beam path directed toward the second image sensor (12B) and having a spectral transmission characteristic such that it transmits light in a second wavelength range corresponding to the colors green and red; - a first signal processor (40) which generates standard image video signals corresponding to a standard observation image based on image pixel signals generated by the white light and read out from the first and second image sensors (12A, 12B); - a second signal processor (36) which generates narrowband video signals corresponding to a narrowband image based on image pixel signals generated by the part of the excitation light reflected from the object and read out from the first image sensor (12A); and - a third signal processor (38) which generates autofluorescence video signals corresponding to an autofluorescence image based on image pixel signals generated by the autofluorescence light emitted by the object and read out from the second image sensor (12B). [2] An electronic endoscope according to claim 1, wherein the first wavelength range is set to a range not exceeding a cutoff wavelength between 450 nm and 550 nm, and the second wavelength range is set to a range exceeding the cutoff wavelength. [3] An electronic endoscope according to claim 1 or 2, wherein the first color filter (13A) includes a plurality of first color elements (B1, B2, B3) whose spectral distribution curves have different spectral peaks. [4] An electronic endoscope according to claim 3, wherein the first color filter (13A) includes three color elements (B1, B2, B3) whose spectral peaks are distributed at equal intervals from each other. [5] An electronic endoscope according to any one of the preceding claims, wherein the second color filter (13B) includes a plurality of second color elements (G, O, R) whose spectral distribution curves have different spectral peaks. [6] An electronic endoscope according to claim 5, wherein the second color filter (13B) includes two or three color elements (G, O, R) whose spectral peaks are distributed at equal intervals from each other. [7] Electronic endoscope according to one of the preceding claims, further comprising: - a single objective optic (18) producing an object image; and - a beam splitter (20) which separates the light passing through the objective optics (18) into light lying in the first wavelength range and light lying in the second wavelength range, wherein an object image is generated on the first image sensor (12A) by the light lying in the first wavelength range and an object image is generated on the second image sensor (12B) by the light lying in the second wavelength range. [8] An electronic endoscope according to any one of claims 1 to 6, further comprising: - a first lens optics (18'A) which forms an object image on the first image sensor (12'A); and - a second lens optics (18'B) which produces an object image on the second image sensor (12'B). [9] The electronic endoscope according to claim 8, further comprising an edge filter (CF) arranged on the front side of the second objective optics (18'B) and blocking the light in the first wavelength range. [10] An electronic endoscope according to any one of the preceding claims, wherein the light supply device comprises: - a light source (32) emitting white light with a distribution extending over the wavelengths of visible light; - an excitation light color filter (48) which transmits light in a wavelength range corresponding to the excitation light; and - a filter drive (46) which selectively arranges the excitation light color filter (48) in the beam path and outside the beam path. [11] The electronic endoscope according to claim 10, wherein the filter drive (46) places the excitation light color filter (48) outside the optical path when a standard observation mode is set to display the standard observation image, and the filter drive (46) places the excitation light color filter (48) in the optical path when a special observation mode is set to display the autofluorescence image and the narrowband image. [12] An electronic endoscope according to any one of claims 1 to 9, wherein the light source comprises: - a white light source (32) emitting white light with a distribution extending over the wavelengths of visible light; - a laser (47) which emits the excitation light; - an optic that directs the excitation light onto the beam path of the white light; and - a laser driver (49) that switches the laser (47) on and off. [13] An electronic endoscope according to claim 12, wherein the laser driver (49) turns off the laser (47) when a standard observation mode is set to display the standard observation image, and the laser driver (49) turns on the laser (47) when the special observation mode is set to display the autofluorescence image and the narrow band image. [14] Electronic endoscope according to one of the preceding claims, further comprising a fourth signal processor which processes the autofluorescence video signals and the narrowband image video signals such that the autofluorescence image and the narrowband image can be displayed simultaneously and separately from one another on a monitor (70). [15] An electronic endoscope according to any preceding claim, further comprising a fifth signal processor (42) selectively outputting the standard image video signals or a set consisting of the narrowband image video signals and the autofluorescence video signals. [16] An electronic endoscope according to any preceding claim, further comprising a changing member (19) operable to set a standard observation mode for displaying the standard observation image or a special observation mode for displaying the autofluorescence image and the narrow band image. [17] Video processor (30) connectable to a video observation unit (10), the video observation unit (10) comprising: - a first image sensor (12A); - a second image sensor (12B); - a first color filter (13A) arranged in a beam path directed toward the first image sensor (12A) and having a spectral transmission characteristic such that it transmits light in a first wavelength range corresponding to the color blue; and - a second color filter (13B) arranged in a beam path directed toward the second image sensor (12B) and having a spectral transmission characteristic such that it transmits light in a second wavelength range corresponding to the colors green and red, wherein the video processor (30) comprises: - a light supply device that selectively irradiates an object to be observed with white light and with excitation light; - a first signal processor (40) which generates standard image video signals corresponding to a standard observation image based on image pixel signals generated by the white light and read out from the first and second image sensors (12A, 12B); - a second signal processor (36) which generates narrowband video signals corresponding to a narrowband image based on image pixel signals generated by the part of the excitation light reflected from the object and read out from the first image sensor (12A); and - a third signal processor (38) which generates autofluorescence video signals corresponding to an autofluorescence image based on image pixel signals generated by the autofluorescence light emitted by the object and read out from the second image sensor (12B).

Images