JP2014076223A - Image signal processing device and electronic endoscope system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image signal processing device and an electronic endoscope system capable of improving coloring of a saturation part of an image.SOLUTION: An image signal processing device includes: an image pick-up device for picking up a subject irradiated with predetermined narrow band light and outputting an image signal; a color conversion part for converting the image signal into a primary color signal of R, G, and B; a saturation determination part for determining whether or not the image signal is saturated; and an image generation part for generating an image of the subject based on the primary color signal. The color conversion part has a first color matrix coefficient set so that a specific structure of the subject is emphasized by the narrow band light and a second color matrix coefficient set so that the strength of each primary color signal increases as a luminance value of a pixel of the image pick-up device increases. When it is determined that the image signal is not saturated, the color conversion is performed using the first color matrix coefficient. When it is determined that the image signal is saturated, the color conversion is performed using the second color matrix coefficient.

Description

  The present invention relates to an electronic endoscope system capable of observing a narrowband light image, and more particularly to an image signal processing apparatus and an electronic endoscope system that suitably reduce coloring in a saturated portion of a narrowband light image.

  In the medical device field, an electronic endoscope system is known that generates and displays an enhanced image (narrowband light image) of a specific part in a body cavity by irradiating the body cavity with narrowband light. In this type of electronic endoscope system, the timing of saturation of each color signal of the CCD differs depending on the spectral sensitivity of a complementary color filter of a CCD (Charge Coupled Device) and the spectral characteristics of a light source lamp, a light guide, and the like. In addition, the color balance may be lost in the saturated portion of the image, and coloring may occur in the observed image displayed on the monitor. Therefore, various countermeasures for suppressing this coloring have been proposed.

  The observation target by the narrow-band light image is various parts in the living body such as the digestive tract, and blood vessel enhancement is performed in the image processing, so that saturation of color signals including a wavelength band in which hemoglobin is absorbed is accelerated. Therefore, for example, in the electronic endoscope system described in Patent Document 1, the charge accumulation amount of the CCD in the wavelength range of the red system of 400 to 700 nm among the image signals output from the CCD is adjusted by the wavelength calibration filter. The red color component is not saturated first.

Japanese Patent No. 4169957

  However, when a wavelength calibration filter is added as in the electronic endoscope system described in Patent Document 1, it is necessary to review the optical design and change signal processing in the system. Furthermore, an increase in cost due to the addition of a filter is inevitable.

  The present invention has been made in view of the above, and an image signal processing apparatus capable of reducing coloring of a saturated portion of an image without adding a new member such as a wavelength calibration filter in narrowband light observation. And it aims at providing an electronic endoscope system.

  In one embodiment of the present invention, a narrowband light emitting unit that emits predetermined narrowband light toward a light guide that guides light for irradiating the subject, and a subject that is irradiated with the predetermined narrowband light An image sensor that picks up an image and outputs an image signal; a color converter that converts the image signal output from the image sensor into primary color signals of R, G, and B; and determines whether the image signal is saturated A saturation determination unit; and an image generation unit that generates an image of the subject based on the primary color signal color-converted by the color conversion unit, the color conversion unit so that the specific structure of the subject is emphasized by the narrowband light A first color matrix coefficient that is set, and a second color matrix coefficient that is set so that the intensity of each primary color signal increases as the luminance value of the pixel of the image sensor increases. The image signal is not saturated When it is determined that the image signal is color-converted using the first color matrix coefficient, and the image signal is color-converted using the second color matrix coefficient when the saturation determination unit determines that the image signal is saturated A processing device is provided.

  According to the above configuration, it is possible to perform color conversion of the image signal so as to suppress variations in the intensity of the primary color signals of R, G, and B in the saturated portion of the image and generate an image in which coloring in the saturated portion is reduced. it can.

  Furthermore, the saturation determination unit may be configured to determine whether the image signal is saturated based on whether the intensity of the image signal is equal to or higher than a predetermined threshold. The narrowband light emitting unit includes a light source that emits predetermined broadband light, a plurality of types of narrowband optical filters that split the broadband light into narrowband light having different spectral characteristics, and a plurality of types of narrowband optical filters. A filter designating unit for designating any one of the filters, and a filter arranging unit for arranging the designated narrowband optical filter in the optical path of the broadband light, and the color conversion unit is provided for each of the plurality of types of narrowband optical filters. On the other hand, the first color matrix coefficient and the second color matrix coefficient corresponding to each spectral characteristic are provided, and the first color matrix coefficient and the second color matrix coefficient are determined according to the designated narrow band optical filter. A configuration may be selected. Furthermore, it is arranged between a broadband light emitting unit that emits predetermined broadband light toward the light guide, the light guide, the narrow band light emitting unit, and the broadband light emitting unit, and the light guide has predetermined narrow band light or Irradiating light selecting means for selectively allowing predetermined broadband light to enter, and the color conversion unit includes a first color matrix coefficient and a second color when the predetermined broadband light is selected by the irradiation light selecting means. The color conversion may be performed using a third color matrix coefficient different from the color matrix coefficient.

  From another viewpoint, according to one embodiment of the present invention, an electronic endoscope system including the image signal processing device configured as described above, and an electronic endoscope having a light guide and an image sensor. Can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the image signal processing apparatus and electronic endoscope system which can improve coloring of the saturated part of an image, without adding new members, such as a wavelength calibration filter, are provided.

FIG. 1 is a block diagram showing a configuration of an electronic endoscope system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of a rotary filter turret mounted on a processor included in the electronic endoscope system according to the embodiment of the present invention. 3A to 3C are diagrams showing spectral characteristics of each optical filter of the rotary filter turret according to the embodiment of the present invention. 4A and 4B are diagrams conceptually illustrating color conversion processing by a color conversion circuit mounted on a processor according to an embodiment of the present invention. FIGS. 5A and 5C are diagrams showing a specific configuration of color matrix coefficients according to an embodiment of the present invention. FIGS. 5B and 5D are diagrams using color matrix coefficients. It is a graph which shows transition of the saturation state of each primary color signal of the image at the time of color conversion. FIG. 6 is a diagram showing a flowchart of color conversion processing according to an embodiment of the present invention.

  Hereinafter, an electronic endoscope system according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an electronic endoscope system 1 according to the present embodiment. As shown in FIG. 1, the electronic endoscope system 1 is a medical imaging system, and includes an electronic endoscope 100, a processor 200, and a monitor 300. The proximal end of the electronic endoscope 100 is connected to the processor 200. The processor 200 is an image signal processing apparatus that illuminates a body cavity that does not reach natural light via the electronic endoscope 100 and processes an image signal output from the electronic endoscope 100 to generate an image. In another embodiment, a light source device that emits illumination light may be configured separately from the processor 200.

  As shown in FIG. 1, the processor 200 includes a system controller 202 and a timing controller 204. The system controller 202 controls each component of the electronic endoscope system 1. The timing controller 204 outputs a clock pulse for adjusting the signal processing timing to each circuit in the electronic endoscope system 1.

  The lamp 208 radiates light in a wavelength range mainly extending from the visible light region to the invisible infrared region after being started by the lamp power igniter 206. As the lamp 208, a high-intensity lamp such as a xenon lamp, a halogen lamp, a mercury lamp, or a metal halide lamp is suitable. The illumination light radiated from the lamp 208 is condensed by the condenser lens 210 and adjusted to an appropriate amount of light through the diaphragm 212.

  A motor 214 is mechanically connected to the diaphragm 212 via a transmission mechanism (not shown) such as an arm or a gear. The motor 214 is a DC motor, for example, and is driven under the drive control of the driver 216. The diaphragm 212 is operated by the motor 214 to change the opening degree so that the image displayed on the display screen of the monitor 300 has an appropriate brightness, and the amount of illumination light emitted from the lamp 208 is changed according to the opening degree. Adjust. The appropriate reference for the brightness of the image is changed according to the brightness adjustment operation performed by the operator on the front panel 218 or the hand operation unit (not shown) of the electronic endoscope 100.

  Various forms of the configuration of the front panel 218 are assumed. Specific examples of the configuration of the front panel 218 include a hardware key for each function mounted on the front surface of the processor 200, a touch panel GUI (Graphical User Interface), a combination of a hardware key and a GUI, and the like.

  Irradiation light that has passed through the aperture 212 enters the rotary filter turret 213. FIG. 2 is a diagram showing a configuration of the rotary filter turret 213. As shown in FIG. 2, the rotary filter turret 213 is a disk-shaped member, and has a plurality of optical filters F1 to F3 and an aperture AP arranged in the circumferential direction. An optical filter is not attached to the aperture AP. The aperture AP may be replaced with a filter that transmits light in the entire visible light region.

  FIG. 3 shows an example of the spectral characteristics of the optical filters F1 to F3. In FIG. 3, the vertical axis indicates the spectral transmittance (normalized and no unit), and the horizontal axis indicates the wavelength (unit: nm). As shown in FIG. 3A, the optical filter F1 is a narrow band optical filter having a transmission peak with a narrow half-value width in three wavelength regions. As shown in FIG. 3B, the optical filter F2 is a narrow-band optical filter having a transmission peak with a narrow half-value width in a wavelength range suitable for absorption of hemoglobin, for example. As shown in FIG. 3C, the optical filter F3 is a narrow band having a transmission peak with a narrow half-value width in a wavelength range corresponding to a specific structure (for example, a gastric gland duct structure) different from the optical filter F2. It is an optical filter. Each narrowband optical filter has, for example, detection (a filter having a spectral characteristic suitable for finding a lesion from a wide range in a body cavity) or a detailed examination (spectral characteristic suitable for examining a found lesion). Filter) and the like.

  The motor 215 is a step motor that is driven under the drive control of the driver 216, for example, and is mechanically coupled to the rotary filter turret 213 via a transmission mechanism (not shown) such as an arm or a gear. The motor 215 rotates the rotary filter turret 213 by an angle corresponding to the applied voltage (pulse).

  The surgeon can rotate the rotary filter turret 213 through a filter switching operation on the front panel 218 or an operation of a filter switching button 114 installed on the hand operation unit of the electronic endoscope 100. In FIG. 1, the connection between the filter switching button 114 and other blocks is omitted in order to simplify the drawing.

  The rotary filter turret 213 rotates 90 ° each time a filter switching operation is performed, and selectively inserts the optical filters F1, F2, F3, and the aperture AP into the illumination optical path. In the vicinity of the outer peripheral edge of the rotary filter turret 213, a position detection hole H for detecting the home position is formed.

  The system controller 202 recognizes which optical filter or aperture AP is arranged in the illumination optical path based on the detection of the position detection hole H through the photo interrupter FI and the number of pulses applied to the motor 215.

  The irradiation light is split into specific narrowband light by an optical filter (any one of F1 to F3) arranged in the illumination optical path, and enters an incident end of an LCB (Light Carrying Bundle) 102. When the aperture AP is disposed in the illumination optical path, the irradiation light that has passed through the stop 212 (that is, broadband white light including the visible light region) is directly incident on the incident end of the LCB 102.

  Irradiation light incident on the incident end of the LCB 102 propagates by repeating total reflection in the LCB 102. Irradiation light propagating through the LCB 102 is emitted from the emission end of the LCB 102 arranged at the tip of the electronic endoscope 100. Irradiation light emitted from the emission end of the LCB 102 reaches the subject via the light distribution lens 104. The reflected light from the subject forms an optical image at each pixel on the light receiving surface of the solid-state image sensor 108 via the objective lens 106.

  The solid-state image sensor 108 is, for example, an interlaced single-plate color CCD image sensor having a complementary color checkered pixel arrangement. The solid-state image sensor 108 accumulates an optical image formed by each pixel on the light receiving surface as a charge corresponding to the amount of light, and obtains an image signal corresponding to each complementary color of yellow Ye, cyan Cy, green G, and magenta Mg. .

  The solid-state imaging device 108 generates and outputs mixed signals Wr, Gb, Wb, and Gr by adding image signals of two pixels adjacent in the vertical direction in order to substantially improve sensitivity and frame rate. The mixed signal is input to the endoscope side signal processing circuit 112 after signal amplification by the preamplifier 110. Note that the color array of the solid-state image sensor 108 may be, for example, a Bayer type. Further, the solid-state image sensor 108 may be replaced with a CMOS (Complementary Metal Oxide Semiconductor) image sensor.

  The timing controller 204 supplies clock pulses to the endoscope side signal processing circuit 112 according to the timing control by the system controller 202. The endoscope side signal processing circuit 112 controls driving of the solid-state imaging device 108 at a timing synchronized with a frame rate of a video processed on the processor 200 side, according to a clock pulse supplied from the timing controller 204. The image signal input to the endoscope side signal processing circuit 112 is subjected to AD conversion after predetermined analog signal processing, and then input to the processor side signal processing circuit 220.

  The processor side signal processing circuit 220 includes a saturation detection circuit 222, a color conversion circuit 224, an image processing circuit 226, and a memory 228. The image signal (mixed signal (Wb, Gb, Gr, Wr)) input to the processor side signal processing circuit 220 is sent to the color conversion circuit 224. The color conversion circuit 224 converts the image signal input to the processor side signal processing circuit 220 into a primary color signal (RGB) using a predetermined color matrix coefficient stored in the memory 228. The image signal is sent to the saturation detection circuit 222 in the color conversion circuit 224. The saturation detection circuit 222 detects whether each image signal is saturated, and generates a detection result as saturation information. Specifically, the saturation detection circuit 222 determines whether or not the intensity of each image signal is equal to or greater than a predetermined threshold, and detects that the image signal is saturated when the intensity is equal to or greater than the threshold. Then, the saturation detection circuit 222 generates a saturation detection signal indicating the detection result of saturation of each image signal. Examples of the saturation detection signal include a bit signal indicating the presence or absence of saturation of each image signal.

  Based on the saturation detection signal generated by the saturation detection circuit 222, the color conversion circuit 224 performs color conversion again by switching the color matrix coefficient for the mixed signal detected as being saturated, and the color-converted primary color signal Is output to the image processing circuit 226. Specific processing contents of the color conversion circuit 224 in this embodiment will be described later.

  The image processing circuit 226 performs predetermined image processing such as γ correction and edge enhancement on the input primary color signal, and stores it in a frame memory (not shown) corresponding to each color of R, G, and B for each color signal. Buffer. The image processing circuit 226 sweeps out each buffered color signal from the frame memory at a timing controlled by the timing controller 204, and the video conforms to a predetermined standard such as NTSC (National Television System Committee) or PAL (Phase Alternating Line). Convert to signal. The converted video signals are sequentially output to the monitor 300, whereby the subject image is displayed on the display screen of the monitor 300.

  The memory 228 stores color matrix coefficients associated with the optical filters F1 to F3 of the rotary filter turret 213. As described above, in narrow-band light observation in a living body such as the digestive tract, an image signal including a wavelength band in which hemoglobin is absorbed is large in order to emphasize the blood vessel of the subject. That is, in the present embodiment, the mixed signal Wb tends to be saturated first. Therefore, in this embodiment, different color matrix coefficients are used for each optical filter depending on whether the mixed signal Wb is not saturated or saturated. For convenience of explanation, among the color matrix coefficients related to the optical filter F1, the color matrix coefficient used when the mixed signal Wb is not saturated is M11, and the color matrix coefficient used when the mixed signal Wb is saturated is M12. And Similarly, M21 and M22 are prepared for the color matrix coefficients related to the optical filter F2, and M31 and M32 are prepared for the color matrix coefficients related to the optical filter F3. Further, M40 is prepared as a color matrix coefficient for the aperture AP (that is, for white light). The specific configuration of color matrix coefficients and details of color conversion processing will be described later.

  The system controller 202 recognizes which optical filter or aperture AP is arranged in the illumination optical path based on the detection of the position detection hole H through the photo interrupter FI and the number of pulses applied to the motor 215. Note that when the electronic endoscope system 1 is activated, the aperture AP is inserted into the illumination optical path. Specifically, the system controller 202 detects the position detection hole H by rotating the rotary filter turret 213 through drive control with respect to the motor 215 when the system is started, and the opening AP is inserted into the illumination optical path. Thus, the rotary filter turret 213 is rotated by a predetermined angle from the detection position of the position detection hole H.

  The system controller 202 controls the color conversion circuit 224 based on the recognition result of which one of the optical filter and the aperture AP is arranged in the illumination optical path. The color conversion circuit 224 acquires an appropriate color matrix coefficient from the memory 228 based on the control signal from the system controller 202 and the saturation detection signal from the saturation detection circuit 222 and performs color conversion processing.

  Here, FIGS. 4A and 4B are conceptual diagrams of color conversion processing by the color conversion circuit 224. FIG. 4A, the left diagram shows the intensity distribution P of the mixed signals Wr, Gb, Wb, and Gr, and the central diagram shows the optical filter of the rotary filter turret 213 arranged in the illumination optical path (for convenience, the optical filter F1). The right figure shows the color matrix coefficient M (3 × 4 matrix) used in the color conversion processing by the color conversion circuit 224. In the left diagram of FIG. 4A, the vertical axis represents intensity (no unit because it is normalized), and the horizontal axis represents wavelength (unit: nm). In the central diagram of FIG. 4A, the vertical axis indicates the spectral transmittance (no unit because it is normalized), and the horizontal axis indicates the wavelength (unit: nm). The intensity distribution P is a wavelength and intensity calculated when spectral characteristics corresponding to two pixels adjacent to each other in the vertical direction of the on-chip color filter of the solid-state image sensor 108 are applied to the formula of the two-pixel addition process. Is a distribution showing the relationship.

  FIG. 4B shows an intensity distribution P ′ indicating the relationship between the wavelength and the intensity obtained by multiplying the intensity distribution P, the spectral characteristic F, and the color matrix coefficient M shown in FIG. In FIG. 4B, the vertical axis represents intensity (no unit because it is normalized), and the horizontal axis represents wavelength (unit: nm).

  In the present embodiment, the intensity distribution P ′ is changed by setting the color matrix coefficient M corresponding to the spectral characteristic F shown in FIG. 4A, and is highlighted on the display screen of the monitor 300. The specific structure of the living body is changed. Note that the color matrix coefficient M shown in FIG. 4A is changed by switching the color matrix coefficient used in the color conversion processing by the color conversion circuit 224.

  Further, the spectral characteristic F shown in FIG. 4A is changed by operating the front panel 218 or the filter switching button 114 to switch the optical path arrangement filter. That is, changing the specific structure of the living body to be highlighted on the display screen of the monitor 300 (changing the intensity distribution P ′) is achieved by switching the optical path arrangement filter. For example, when observing a narrow band light with a specific structure that is difficult to highlight with the spectral characteristics of the optical filter F1, the operator switches the optical path arrangement filter to the optical filter F2 or F3. Thereby, it is possible to display a narrowband light image having a specific structure that is difficult to highlight with the spectral characteristics of the optical filter F <b> 1 on the display screen of the monitor 300.

  FIGS. 5A to 5D show a specific configuration example of color matrix coefficients in the present embodiment, and luminance values and intensities of pixels of primary color signals R, G, and B after color conversion processing when the coefficients are used. It is a figure which shows the relationship. FIG. 5A shows color matrix coefficients used when the mixed signal Wb is not saturated, and FIG. 5B is a graph when color conversion processing is performed using the color matrix coefficients. is there. FIG. 5C shows color matrix coefficients used when the mixed signal Wb is saturated. FIG. 5D shows a case where color conversion processing is performed using the color matrix coefficients. It is a graph. The luminance value of the pixel on the horizontal axis of each graph is an average value of the luminance values of the mixed signals Wb, Gb, Gr, and Wr that are the source of color conversion. The intensity on the vertical axis of the graph is the signal intensity of each primary color signal after color conversion using color matrix coefficients. That is, by changing each component of the color matrix coefficient, the intensity of each primary color signal also changes.

  As shown in FIG. 5B, when the color matrix coefficient of FIG. 5A is used (that is, when the mixed signal Wb is not saturated), the primary color signal R increases the luminance value of the pixel. Along with this, the strength increases, reaches the maximum value at the position indicated by P in the graph, and is saturated. In the present embodiment, when the intensity of the primary color signal reaches the maximum value, it is regarded as saturation. Even if the luminance value of the pixel further increases, the intensity of the primary color signal R does not change, and the primary color signal R remains saturated. Here, in the image displayed on the monitor 300, a portion where the primary color signal is saturated is referred to as a saturated portion. As shown in FIG. 5B, the intensities of the primary color signals G and B change without correlation when the primary color signal R reaches saturation and the luminance value of the pixel further increases. For this reason, coloring occurs due to variations in the intensity of each primary color signal R, G, B in the saturated portion of the image. Therefore, in the present embodiment, when the mixed signal Wb is saturated, the color matrix used for color conversion is switched to the color matrix coefficient shown in FIG. By increasing the intensity of the non-primary color signals G and B toward the saturation as the luminance value of the pixel increases, the intensity variation of the primary color signals R, G, and B is suppressed to reduce coloring.

  The color matrix coefficients of the present embodiment shown in FIG. 5C are set so that the primary color signal R is saturated at substantially the same timing when the mixed signal Wb is saturated, and is shown in FIG. 5D. Thus, when the primary color signal R reaches saturation at the position indicated by P (that is, when the mixed signal Wb is saturated) and the luminance value of the pixel further increases, the intensities of the primary color signals G and B are both linearly It is set to increase and go toward saturation. For this reason, in the saturated portion of the image displayed on the monitor 300, variations in intensity of the primary color signals R, G, and B can be suppressed, and coloring can be reduced.

  Next, details of the color conversion processing in the present embodiment will be described. FIG. 6 is a diagram showing a flowchart of the color conversion processing of the color conversion circuit 224 in the present embodiment. The color conversion circuit 224 performs the processing of this flowchart for each input mixed signal (that is, for each pixel). For convenience of explanation, the processing step is abbreviated as “S” in the description and drawings in this specification. First, the color conversion circuit 224 determines whether an optical filter is arranged in the illumination optical path based on a control signal from the system controller 202 (S101).

  When the aperture AP is disposed in the illumination optical path (S101: No), color conversion processing is performed on the mixed signal to be processed using the color matrix coefficient M40 for white light (S103), and this flowchart is performed. The process ends. The color conversion circuit 224 repeats the above processing according to this flowchart for subsequent mixed signals.

  When the aperture AP is arranged in the illumination optical path, the subject is irradiated with broadband white light including a visible light region. The solid-state image sensor 108 receives reflected light from a subject irradiated with white light and converts it into an image signal. The image signal undergoes signal processing in each circuit of the preamplifier 110, the endoscope side signal processing circuit 112, and the processor side signal processing circuit 220, and is output to the monitor 300. A normal color image is displayed on the display screen of the monitor 300. Is displayed.

  On the other hand, when the optical filter F1, F2 or F3 is arranged in the illumination optical path (S101: Yes), the process proceeds to S105. In S105, the saturation detection circuit 222 determines whether the input image signal (that is, the mixed signal Wb) is saturated, and generates a saturation detection signal. When it is determined that the mixed signal Wb is not saturated, the process proceeds to S107, and when it is determined that the mixed signal Wb is saturated (that is, when a saturation detection signal is generated), the process is performed. The process proceeds to S109.

  In S107, the color conversion circuit 224 acquires any one of the color matrix coefficients M11, M21, and M31 from the memory 228 according to the optical filter disposed in the illumination optical path, and uses the acquired color matrix coefficient. Then, the color conversion process of the mixed signal is performed to generate the primary color signal, and the process of this flowchart is finished.

  In S109, the color conversion circuit 224 acquires any one of the color matrix coefficients M12, M22, and M32 from the memory 228 according to the optical filter disposed in the illumination optical path, and uses the acquired color matrix coefficient. Then, the color conversion process of the mixed signal is performed to generate the primary color signal, and the process of this flowchart is finished. Similar to the case where the aperture AP is arranged in the illumination optical path, even when the optical filter F1, F2, or F3 is arranged in the illumination optical path, the color conversion circuit 224 performs the following mixed signal in accordance with this flowchart. Repeat the above process.

  As described above, according to the present embodiment, when the image signal (that is, the mixed signal Wb) is not saturated, the color matrix coefficients M11, M21, and M31 are used to appropriately enhance the blood vessel to be observed. When the image signal (that is, the mixed signal Wb) is saturated, color matrix coefficients M12, M22, and M32 are used to reduce unnatural coloring in the saturated portion. Since color conversion processing for generating an image is performed, an observation object is easy to see, and an image contributing to more accurate diagnosis can be displayed on the monitor 300.

  The above is the description of the embodiment of the present invention. The present invention is not limited to the above configuration, and various modifications are possible within the scope of the technical idea of the present invention. The number of optical filters arranged in the illumination optical path, spectral characteristics, color matrix coefficients, etc. Is not limited to that of the present embodiment, and can be changed as appropriate. For example, the color matrix coefficients of this embodiment shown in FIG. 5C are set so that the primary color signal R is saturated at substantially the same timing when the mixed signal Wb is saturated. It is not necessary to configure so that the saturation of the primary color signal R matches.

  In the present embodiment, the color matrix coefficient used when the mixed signal Wb is saturated is configured such that the intensity of the primary color signal that is not saturated increases linearly and goes toward saturation. However, the configuration is not limited to a configuration in which the intensity of the unsaturated primary color signal has a predetermined correlation and goes toward saturation, and increases linearly.

  Also, in the above description, assuming that the R component of each primary color signal is saturated first when the luminance value of the pixel is increased, displaying an image subjected to blood vessel enhancement or the like in narrowband light observation Although the preferred embodiment has been described, even when other primary color signals are saturated first, switching to a color matrix coefficient that increases the intensity of the unsaturated primary color signal as described above according to the saturated primary color signal. By adopting the configuration, it is possible to reduce coloring in the saturated portion of the display image.

  In the above description, the case where the intensity of the primary color signal reaches the maximum value is regarded as saturation. However, the structure may be regarded as saturation when the intensity of the primary color signal exceeds a predetermined threshold. In the above description, the memory 228 for storing the color matrix coefficients is arranged outside the color conversion circuit 224. However, the color conversion circuit 224 may have the memory 228.

DESCRIPTION OF SYMBOLS 1 Electronic endoscope system 100 Electronic endoscope 200 Processor 202 System controller 213 Rotary filter turret 220 Processor side signal processing circuit 222 Saturation detection circuit 224 Color conversion circuit 226 Image processing circuit 228 Memory 300 Monitor FI Photo interrupter

Claims (5)

A narrowband light emitting unit that emits predetermined narrowband light toward a light guide that guides light for illuminating the subject;
An image sensor that images the subject irradiated with the predetermined narrowband light and outputs an image signal;
A color conversion unit for color-converting the image signal output from the image sensor into R, G, and B primary color signals;
A saturation determination unit for determining whether or not the image signal is saturated;
An image generation unit that generates an image of the subject based on a primary color signal color-converted by the color conversion unit;
With
The color converter is
The first color matrix coefficient set so that the specific structure of the subject is emphasized by the narrowband light, and the intensity of each primary color signal increase as the luminance value of the pixel of the image sensor increases. A second color matrix coefficient set to
When the saturation determination unit determines that the image signal is not saturated, color conversion is performed using the first color matrix coefficient, and the saturation determination unit determines that the image signal is saturated. An image signal processing apparatus characterized in that color conversion is performed using the second color matrix coefficient.   The image signal according to claim 1, wherein the saturation determination unit determines whether or not the image signal is saturated based on whether or not the intensity of the image signal is equal to or greater than a predetermined threshold. Processing equipment. The narrow-band light emitting part is
A light source that emits predetermined broadband light;
A plurality of types of narrowband optical filters that split the broadband light into narrowband light having different spectral characteristics;
Filter designating means for designating any one of the plurality of types of narrowband optical filters;
Filter arrangement means for arranging the designated narrowband optical filter in the optical path of the broadband light, wherein the color conversion unit corresponds to each spectral characteristic for each of the plurality of types of narrowband optical filters. The first color matrix coefficient and the second color matrix coefficient are selected, and the first color matrix coefficient and the second color matrix coefficient are selected according to the designated narrowband optical filter. The image signal processing apparatus according to claim 1, wherein: A broadband light emitting section for emitting the predetermined broadband light toward the light guide;
Irradiation light selection means that is arranged between the light guide and the narrowband light emitting section and the broadband light emitting section, and selectively makes the predetermined narrowband light or the predetermined broadband light incident on the lightguide. And comprising
The color conversion unit uses a third color matrix coefficient different from the first color matrix coefficient and the second color matrix coefficient when the predetermined broadband light is selected by the irradiation light selection unit. The image signal processing apparatus according to claim 3, wherein color conversion is performed. The image signal processing device according to any one of claims 1 to 4,
An electronic endoscope having the light guide and the imaging device;
An electronic endoscope system comprising:

Images