JP2016034416A - Endoscope apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately perform color reproduction of an observation image without being affected by a change with time of a scope.SOLUTION: During the white balance adjustment, an auxiliary light source which is switched from a main lamp is used, and color correction processing is performed by a matrix operation using an initial matrix coefficient so as to calculate R, G, and B image signal values (Rt, Gt, and Bt). A matrix table indicating the correspondence between the R, G, B image signal values that change by a change with time of a scope and the matrix coefficient is stored beforehand, the matrix coefficient prepared for the image signal values (Rd, Gd, and Bd) substantially the same as the R, G, and B image signal values (Rt, Gt, and Bt) is selected, and is used for the color correction processing in an image signal processing circuit.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an endoscope apparatus that images a subject such as an inner wall of an organ using a scope (endoscope) and performs treatment, and more particularly, to color correction and color adjustment processing with respect to changes over time of the scope.

  In an endoscope apparatus, a video scope having an image sensor such as a CCD or CMOS at the tip is inserted into the body, and an inner wall of an organ is imaged. R, G, and B color image signals are generated by performing white balance adjustment, color conversion processing, and the like on the pixel signals read from the image sensor.

  The spectral transmission characteristic of the light guide (fiber bundle) provided in the video scope deteriorates with time, and affects the image quality and color reproducibility of the observed image. In order to prevent such a change with time of the scope, a dedicated filter for cutting light in a specific wavelength region is arranged in the optical path.

  On the other hand, by performing color correction processing on the image signal, color reproducibility can be maintained regardless of the temporal change of the scope. For example, the videoscope usage status, such as the videoscope usage time and the number of sterilization processes, is detected, a matrix coefficient is set according to the scope usage status, and color correction processing is performed by multiplying the image signal by the matrix coefficient (patent) Reference 1).

JP 2009-285191 A

  The installation of the dedicated filter causes the manufacturing process of the endoscope apparatus to become complicated and costly. In addition, with respect to the light source for illumination, the spectral distribution characteristics are deteriorated due to a change with time, which affects the color reproducibility. Therefore, even if the matrix coefficient is set in consideration of the scope usage time, it is difficult to realize appropriate color reproduction.

  Therefore, it is required to accurately detect a change in the color component of the image signal accompanying a change in the scope with time and set a matrix coefficient suitable for the change.

  The endoscope apparatus of the present invention, a scope having a light guide, an image signal processing unit that performs matrix calculation processing on a pixel signal read from an image sensor provided at the distal end of the scope, and radiates illumination light. A reference light source that can be switched to the main light source, a color adjustment unit that sets a matrix coefficient used for matrix calculation processing, a value of a color image signal accompanied by a color component change caused by a temporal change of the light guide, and a change in the color component And a memory for storing a matrix table showing a correspondence relationship with the matrix coefficient for compensating for. In the image signal processing unit, for example, matrix calculation is performed in color correction processing for a color image signal. The reference light source can be constituted by an auxiliary light source, for example.

  In the present invention, the color adjustment unit switches from the main light source to the reference light source, and selects a matrix coefficient corresponding to the reference color image signal obtained by the reference light source based on the matrix table. Here, the “matrix coefficient that compensates for the color component change of the color image signal value” represents a matrix coefficient that realizes the same color reproducibility as or near to the color reproducibility when there is no temporal change of the light guide. . When a matrix coefficient is set from the reference color image signal based on the auxiliary light source, the main light source is switched, and color correction processing based on the set matrix coefficient can be executed. A matrix table for each scope model may be prepared.

  The reference color image signal color adjusting unit can set a predetermined initial matrix coefficient in accordance with switching from the main light source to the reference light source. For example, the color adjustment unit switches from the main light source to the reference light source and selects the matrix coefficient before the white balance adjustment processing. In this case, it is possible to set a matrix coefficient corresponding to the white subject.

  An endoscope color adjustment apparatus according to the present invention radiates illumination light, an image signal processing unit that performs matrix calculation processing on pixel signals read from an image sensor provided at a distal end portion of a scope having a light guide, and the like. A light source switching control unit that controls switching between the main light source and the quasi-light source, and a color adjustment unit that sets a matrix coefficient used for matrix calculation processing. The color adjustment unit responds to switching from the main light source to the reference light source. The reference color obtained by the reference light source based on a matrix table showing the correspondence between the color image signal value accompanied by the color component change caused by the light guide change over time and the matrix coefficient for compensating the color component change A matrix coefficient corresponding to the image signal is selected.

  As described above, according to the present invention, it is possible to appropriately reproduce the color of the observation image without being affected by the temporal change of the scope.

It is a block diagram of the electronic endoscope apparatus which is this embodiment. It is a flowchart of the white balance adjustment process accompanied by a color correction process. It is the figure which showed the matrix table showing the correspondence of the pixel signal value of R, G, B reflecting the time-dependent change of a light guide, and the matrix coefficient according to it. It is the figure which showed the optical characteristic of the light guide. It is the figure which showed the time-dependent change of the light guide.

  Below, the electronic endoscope system which is this embodiment is demonstrated with reference to drawings.

  FIG. 1 is a block diagram of an electronic endoscope apparatus according to this embodiment.

  The electronic endoscope apparatus includes a video scope 10 and a processor 30, and the video scope 10 can be detachably connected to the processor 30. A monitor 60 is connected to the processor 30.

  The processor 30 includes a main lamp (main light source) 48 such as a xenon lamp, and the main lamp 48 used during normal endoscope observation is driven by a lamp driving circuit 43. The light emitted from the main lamp 48 enters the incident end of the light guide 11 provided in the video scope 10 through the condenser lens 45. The auxiliary light source 49 is an auxiliary lamp composed of an LED or the like, and can be switched to the main lamp 48 by a driving mechanism (not shown) to emit illumination light. Light emitted from the light guide 11 is irradiated from the distal end portion 10T of the scope toward the subject (observation target) via the light distribution lens 21.

  The illumination light reflected from the subject is imaged by the objective lens 13 provided at the scope tip 10T, and a subject image is formed on the light receiving surface of the image sensor (CCD, CMOS, etc.) 12. The image sensor 12 is driven by the drive circuit 17, and pixel signals for one frame / field are read from the image sensor 12 at predetermined time intervals (for example, 1/30 second and 1/60 second intervals). Here, the image sensor 12 is provided with a color filter (not shown) in which color elements such as Cy, Mg, Ye, G, or R, G, B are arranged.

  A series of pixel signals read from the image sensor 12 is input to the initial circuit 15 via the amplifier 14 and digitized. The image signal processing circuit 16 performs image signal processing such as gamma correction processing, color conversion processing, and white balance processing on the series of digital pixel signals. As a result, R, G, and B color image signals are generated.

  The image signal transmitted to the processor 30 is subjected to predetermined processing in the pre-stage signal processing circuit 32 and then temporarily stored in the image memory 34. Then, the post-stage signal processing circuit 36 performs contour enhancement processing, superimposition processing, and the like on the image signal. By outputting the image signal as a video signal to the monitor 60, the observation image is displayed on the monitor 60 in real time.

  A system control circuit 40 including a CPU, a ROM, a RAM, and the like outputs a control signal to the timing generator 38, the subsequent signal processing circuit 36, and the like, and controls the operation of the processor 30 while the processor 30 is in the power-on state. The operation control program is stored in advance in the ROM.

  When the video scope 10 is connected to the processor 30, the system control circuit 40 communicates with the scope controller 19 and acquires data relating to scope characteristics (resolution, scope model / type, etc.) stored in the memory 20. The scope controller 19 outputs a control signal to the timing generator 18 and the like, and controls the operation of the video scope 10.

  The processor 30 performs automatic light control processing so that the brightness of the displayed subject image is maintained at an appropriate level. The system control circuit 40 detects the luminance level of the read pixel signal and controls the motor driver 42 based on the difference from the reference luminance value. A diaphragm 46 driven by a motor 44 is provided between the main lamp 48 and the light guide 11, and the amount of illumination light is adjusted by adjusting the opening of the diaphragm 46.

  The front panel 50 of the processor 30 is provided with a calibration button (not shown), and the system control circuit 40 detects an operation on the calibration button. When performing the white balance adjustment process, the operator inserts the scope distal end portion 10T into the cylindrical instrument 100 for white balance adjustment, and operates the calibration button. The cylindrical bottom surface of the cylindrical instrument 100 is white, and is used as a white subject when white balance adjustment is performed.

  In the present embodiment, when white balance adjustment is performed, the color component changes of the R, G, and B image signals accompanying the temporal change of the light guide 11 of the video scope 10, that is, the relative output levels of the R, G, and B image signals, respectively. Detect changes in Then, the image signal processing circuit 16 performs color correction and color adjustment processing according to the color component change amount of the R, G, and B image signals.

  Specifically, the relative output level (color level) of the R, G, and B image signals is adjusted by multiplying the image signal by a matrix coefficient so as to compensate for the color change of the image signal value. The color correction process is based on the following equation. However, Rin, Gin, and Bin are R, G, and B image signal values before correction, M is a matrix, Kr1 to Kr3, Kg1 to Kg3, and Kb1 to Kb3 are matrix coefficients, and Rout, Gout, and Bout are color corrections. The subsequent R, G, B image signal values are represented.

  Hereinafter, the color correction process will be described with reference to FIGS.

  FIG. 2 is a flowchart of the white balance adjustment process accompanied by the color correction process. FIG. 3 is a diagram showing a matrix table that represents the correspondence between R, G, and B pixel signal values reflecting the temporal change of the light guide and the corresponding matrix coefficients. FIG. 4 is a diagram showing a change with time of the light guide.

  When the calibration button is operated with the video scope 10 set on the cylindrical instrument 100, the light source used for illumination is switched from the main lamp 48 to the auxiliary light source 49 (S101). Then, an initial matrix coefficient is set as a matrix coefficient used for color correction processing (S102). The initial matrix coefficient is a matrix coefficient that serves as a reference when it is assumed that the light guide does not change with time. Here, a value such that Rin: Gin: Bin is 1: 1: 1 (for example, Kr1 in the above equation). = Kg2 = Kb3 = 1, otherwise 0) is preset.

  In step S103, R, G, and B image signal values (Rt, Gt, and Bt) based on the initial matrix coefficients are calculated as R, G, and B image signals (reference color image signals) that are referred to in color correction processing. The The R, G, B image signal values (Rt, Gt, Bt) are obtained, for example, by extracting a part of the observation image area and calculating an average value for each color. When the light guide 11 is changed over time, the R, G, B image signal values (Rt, Gt, Bt) based on the initial matrix coefficients are changed in color components accompanying the change over time, that is, R, There is a change in the ratio of the G and B image signal values.

  In FIG. 4, the spectral transmission characteristics of the light guide 11 when the light guide 11 has not changed with time with respect to R, G, and B light are represented by distribution curves “RS”, “GS”, and “BS”, respectively. (FIG. 4A). When the accumulated usage time reaches a certain level as the video scope 10 is used, the spectral transmission characteristics of the light guide 11 deteriorate. Here, the spectral transmission characteristics “RS ′”, “GS ′”, and “BS ′” in which the relative sensitivity in the short wavelength region is lower than before are shown (FIG. 4B). As a result, the spectral transmission characteristic T of the entire illumination light also changes to T ′, and changes to yellowish light.

  Matrix coefficients used in the color correction process are set to values that compensate for color component changes in R, G, and B image signal values. For example, when the spectral transmission characteristic of the light guide 11 is lowered as shown in FIG. 4, the value of the B component image signal is relatively reduced. In order to compensate for this, the values of Kb1, Kb2, Kb3, Kr3, Kg3, and Kb3 are set larger than the matrix coefficient values when the spectral distribution characteristics of the light guide 11 are not degraded.

  By the way, the amount of change of the image signal value accompanying the change with time of the light guide 11 differs depending on the difference in the accumulated usage time of the video scope 10. Therefore, it is necessary to set the matrix coefficient in accordance with the amount of change in the image signal value that varies depending on the cumulative usage time. Further, the temporal change of the light guide 11 varies depending on the type of the light guide, that is, the model (type) of the video scope 10.

  FIG. 3 shows a matrix table showing the correspondence between R, G, and B image signal values (Rd, Gd, and Bd) as the videoscope 10 is used and the corresponding matrix coefficients. Here, the image signal values (Rd, Gd, Bd) calculated at predetermined time intervals while actually using the video scope 10 are measured in advance before the sale of the endoscope apparatus product, and the measured values are measured. The matrix coefficient adapted to is calculated.

  In the first measurement immediately after the start of use, the image signal value (Rd, Gd, Bd) does not include the color change amount, so the same value as the initial matrix coefficient is set. Then, image signal values (Rd, Gd, Bd) are measured up to the n-th time, and matrix coefficients corresponding to the image signal values are calculated. A matrix table representing the correspondence between the measured image signal values (Rd, Gd, Bd) and the calculated matrix coefficients is stored in advance in the nonvolatile memory 37.

  The measurement time interval is set to a time interval in which the color change amounts of the R, G, and B image signals clearly appear. An auxiliary light source 49 is used for measuring image signal values (Rd, Gd, Bd) measured in advance.

  Further, in order to correspond to the model (type) of the video scope 10, a matrix coefficient is calculated and stored in advance for each model of the video scope 10. FIG. 3 shows matrix coefficients corresponding to image signal values (Rd, Gd, Bd) for two different types of video scopes M1 and M2. Note that the matrix coefficients corresponding to the first image signal values (Rd, Gd, Bd) in M1 and M2 are the same as the initial matrix coefficient values here.

  In step S104, the matrix table stored in advance in the memory 37 is referred to, and the R, G, B image signal values (Rt, Gt, Bt) based on the initial matrix coefficients match or are closest to each other. An image signal value (Rt, Gt, Bt) is selected, and a matrix coefficient corresponding to it is selected.

  The system control circuit 40 outputs matrix coefficient data to the scope controller 19, and the scope controller 19 controls the image signal processing circuit 16 to set the matrix coefficient for color correction processing to the selected matrix coefficient. To do. As a result, the image signal processing circuit 16 calculates image signal values (Rout, Gout, Bout) based on the selected matrix coefficient.

  In step S105, the auxiliary light source 49 is switched to the main lamp 48 at the end of the color correction process, and the white balance adjustment process is executed. In the white balance adjustment processing, gain processing is performed so that the image signal values (Rout, Gout, Bout) are 1: 1: 1 in a state where the color correction processing is performed. Thereby, the color change of the R, G, and B image signals due to the temporal change of the main lamp 48 is compensated.

  As described above, according to the present embodiment, when adjusting the white balance, the main lamp 48 is switched to the auxiliary light source 49 and the color correction processing is executed by the matrix calculation using the initial matrix coefficient, which is used when referring to the matrix table. R, G, B image signal values (Rt, Gt, Bt) are calculated. A matrix table showing the correspondence between R, G, B image signal values that change with time-dependent changes in scope and matrix coefficients is stored in advance, and R, G, B image signal values (Rt, Gt, Bt) and Matrix coefficients prepared for substantially the same image signal values (Rd, Gd, Bd) are selected and used for color correction processing in the image signal processing circuit 16.

  In this way, by setting the matrix coefficient so as to compensate for the color component change of the R, G, B image signal values caused by the scope change over time, the same value as the R, G, B image signal value without change over time is obtained. Image signal values (Rout, Gout, Bout) are obtained, and the color reproducibility of the observation image is maintained.

  The amount of change in the R, G, and B image signals due to the change with time of the scope varies depending on the accumulated usage time of the video scope 10 and also varies depending on the model, but a matrix coefficient is prepared for each scope usage status and model. By storing and referring to the matrix table in advance, an appropriate matrix coefficient can be selected in various endoscope work situations.

  The spectral distribution characteristics of a main lamp that is frequently replaced change with time, and the amount of change in R, G, and B image signal values varies depending on the cumulative lamp usage time, model, and the like. In addition, the spectral distribution characteristics are different before and after replacement. However, by using an emergency auxiliary light source that is rarely used in place of the main lamp, the color correction process can be performed without being affected by the temporal change of the main lamp. In particular, it is possible to prevent an excessive gain process from being performed by combining a change with time of the scope and a change with time of the main lamp during white balance.

  In addition, by performing color correction processing at the time of white balance adjustment, it is possible to automatically perform imaging based on a white subject, and to set an appropriate initial matrix coefficient. On the other hand, by using an auxiliary light source that does not substantially change over time for color correction processing, color correction processing can be performed without providing a dedicated light source.

  The color correction process can be integrated with the color conversion process, and the matrix coefficient can be set according to a change with time, and may be performed when a color image signal value corresponding to the color space is calculated. It is also possible to perform color correction processing at times other than during white balance adjustment. Color correction processing may be performed on color image signals other than R, G, and B.

DESCRIPTION OF SYMBOLS 10 Videoscope 11 Light guide 12 Image sensor 16 Image signal processing circuit (image signal processing part)
19 Scope controller 40 System control circuit (color adjustment unit, light source switching control unit)
48 Main lamp (main light source)
49 Auxiliary light source (reference light source)
M matrix

Claims (7)

A scope having a light guide;
An image signal processing unit that performs matrix calculation processing on a pixel signal read from an image sensor provided at the distal end of the scope;
A reference light source that emits illumination light and is switchable with the main light source;
A color adjustment unit for setting a matrix coefficient used for matrix calculation processing;
A memory for storing a matrix table showing a correspondence relationship between a value of a color image signal accompanied by a color component change caused by a change in the light guide with time and a matrix coefficient for compensating the color component change;
The endoscope apparatus, wherein the color adjustment unit switches from the main light source to the reference light source and selects a matrix coefficient corresponding to a reference color image signal obtained by the reference light source based on a matrix table.   The endoscope apparatus according to claim 1, wherein the color adjustment unit sets a predetermined initial matrix coefficient in accordance with switching from the main light source to the reference light source.   The endoscope apparatus according to claim 1, wherein the color adjustment unit switches from the main light source to the reference light source and selects a matrix coefficient before white balance adjustment processing.   The endoscope apparatus according to any one of claims 1 to 3, wherein the color adjustment unit switches from the reference light source to the main light source after selecting a matrix coefficient.   The endoscope apparatus according to any one of claims 1 to 4, wherein a matrix table for each scope model is stored in the memory.   The endoscope apparatus according to claim 1, wherein the reference light source is an auxiliary light source. An image signal processing unit that performs matrix calculation processing on pixel signals read from an image sensor provided at the distal end of a scope having a light guide;
A light source switching control unit that controls switching between a main light source that emits illumination light and a quasi-light source;
A color adjustment unit for setting a matrix coefficient used for matrix calculation processing,
In response to switching from the main light source to the reference light source, the color adjusting unit compensates for the color component change and the value of the color image signal accompanied by the color component change caused by the change of the light guide with time. And a matrix coefficient corresponding to a reference color image signal obtained by the reference light source is selected on the basis of a matrix table showing a correspondence relationship between

Images