JP4475936B2 - Electronic endoscope device - Google Patents

Description

  The present invention relates to a videoscope (electronic endoscope) having an image sensor and an electronic endoscope apparatus including a processor to which the videoscope is connected, and in particular, a pixel signal read from an image sensor provided at the tip of the videoscope. The present invention relates to signal processing for generating a color video signal based on the above.

The electronic endoscope apparatus generates a digital video signal (for example, luminance signal Y, color difference signals Cb, Cr) in a format (for example, 4: 2: 2 format) according to a predetermined video standard in the video scope, A configuration for outputting a digital video signal to a processor is known (see, for example, Patent Documents 1, 2, and 3). Also, a configuration is known in which an adapter is provided between a video scope and a processor due to a difference in the format of transmitted data (see Patent Document 4).
Japanese Patent Laid-Open No. 2000-261821 (FIG. 1) JP-A-5-236480 (FIG. 1) JP-A-5-316513 (FIG. 1) JP-A-5-176886 (FIG. 1)

  When a digital video signal is generated in a video scope, the circuit configuration becomes complicated, the manufacturing cost increases, and downsizing of the scope size becomes difficult. In particular, since a large number of multiplication circuits are required to generate a digital video signal, the circuit configuration is necessarily complicated. Further, the larger the information amount of the pixel signal read out from the image sensor, the higher the signal transmission rate (frequency), which causes noise (EMC) that becomes an electric circuit failure in the medical device. Furthermore, when a digital video signal is output to a processor in accordance with the TV standard or the like, the number of transmission signal lines cannot be reduced, causing noise. Also, since the image quality, resolution, color reproducibility, etc. are all determined on the video scope side, there are restrictions when changing the color reproducibility on the processor side.

  The electronic endoscope apparatus according to the present invention can simplify the circuit configuration in the video scope, realize noise generation, prevent image quality deterioration, stabilize the signal transmission speed to the processor, and provide pixel characteristics of the image sensor. This is an electronic endoscope apparatus including a video scope and a processor capable of displaying a subject image having a desired color reproducibility irrespective of the above. The video scope includes an image sensor, a signal reading unit, a digital conversion processing unit, a digital pixel signal output unit, and a memory. The processor of the electronic endoscope apparatus according to the present invention connected to the video scope includes a video signal generating means for generating a color video signal based on a plurality of color element digital pixel signals.

  The image sensor is provided with a color filter configured by regularly arranging a plurality of color elements related to the color video signal according to the position of the pixel. For example, primary colors (R, G, B) are arranged. ) Filters and complementary color (G, Ye, Cy, Mg) filters are provided. The signal reading means reads a series of analog pixel signals composed of pixel signals corresponding to a plurality of color elements from the image sensor. For example, the signal reading means reads a series of digital pixel signals according to a single-plate simultaneous color difference line sequential method. In this case, the complementary color filter is configured by regularly arranging blocks composed of four color elements, cyan, magenta, green, and yellow, in accordance with the color difference line sequential method. The digital conversion means converts the series of analog pixel signals into a series of digital pixel signals according to a clock pulse signal having a predetermined frequency. For example, each digital pixel signal is represented as data of a predetermined number of bits. Also, the frequency (sampling frequency) at the time of digital conversion depends on the number of pixels of the image sensor, the readout method, and the like.

  The digital pixel signal output means of the present invention does not output the digital luminance signal Y, the color difference signals RY, BY, or the analog pixel signal to the outside of the video scope, but directly outputs the digital pixel signal to the outside. Output. That is, the digital pixel signal output means generates a plurality of color element-corresponding digital pixel signals by separating the pixel signals for each predetermined color element based on a series of digital pixel signals, and generates a clock having a frequency lower than the predetermined frequency. According to the pulse signal, a plurality of color element-corresponding digital pixel signals are separated and output to the outside as they are. What is necessary is just to select suitably the number of systems which isolate | separate and transmit as needed. For example, the digital pixel signal output means separates a series of digital pixel signals into a first pixel signal and a second pixel signal each composed of pixel signals corresponding to the same number of color elements, and two transmissions It may be output to the outside through a route. Alternatively, when the color filter is composed of blocks composed of four color elements, the digital pixel signal may be output separately in four systems. When the digital pixel signal is a parallel signal, the digital pixel signal output means includes a parallel / serial conversion means for converting the plurality of color element corresponding digital pixel signals from a parallel signal to a serial signal for serial transmission. May be.

  Furthermore, in the electronic endoscope apparatus of the present invention, a video scope is provided with a memory capable of storing data relating to pixel sensitivity information of the image sensor, and the processor is adapted to the plurality of color elements based on the data relating to the pixel sensitivity information. Video signal generating means for generating a color video signal from the digital pixel signal is provided. The pixel sensitivity information represents a spectral transmission characteristic (pixel sensitivity characteristic) of light caused by a color filter or the like, and the color tone of the subject image displayed changes according to the spectral distribution characteristic. In the present invention, a color video signal is generated so that a subject image having a predetermined color tone is displayed regardless of the pixel sensitivity characteristics of the image sensor.

  Since it is not necessary to provide a multiplication circuit that is necessary for generating luminance and color difference signals and that increases the circuit configuration, the circuit configuration in the video scope is simplified. In addition, since the clock pulse frequency at the time of external output is reduced, noise generation can be suppressed, and by adjusting the number of signal lines to be separated, the transmission rate is stable regardless of the number of pixels of the image sensor. It becomes possible to output a digital pixel signal to the outside. In addition, since the digital video signal itself is not output to the outside, the image quality adjustment range is expanded.

  A color video signal can be generated in consideration of pixel sensitivity characteristics, and a subject image having a desired color tone can be displayed regardless of the type of the image sensor.

  In the case where the color filter is configured by regularly arranging blocks of four color elements, cyan, magenta, green, and yellow, the video signal generation unit is configured to correspond to the digital elements corresponding to the plurality of color elements. An addition / subtraction circuit for generating luminance and color signals from the pixel signals, matrix coefficient setting means for setting matrix coefficients according to the data of the pixel sensitivity information, and the luminance and color signals in a matrix according to the set matrix coefficients It is preferable to provide an R, G, B conversion circuit for converting into R, G, B primary color signals by calculation.

  Regarding color adjustment, it is desirable that color adjustment processing is performed in a stage before the luminance Y and the color difference signals RY and BY are generated. For example, the video signal generating means includes a correction coefficient setting means for setting a correction coefficient of each color element corresponding digital pixel signal according to the pixel sensitivity information data, and a correction coefficient corresponding to the plurality of color element corresponding digital pixel signals. And an addition / subtraction circuit that generates luminance and color signals, and an R, G, and B conversion circuit that converts the luminance and color signals into R, G, and B primary color signals by matrix calculation according to a set matrix coefficient. It is good to have.

  As a configuration for separating a series of digital pixel signals and outputting them to the outside, for example, a configuration may be adopted in which downsampling is performed with pixel delay. In this case, the digital pixel signal output means includes pixel delay means for delaying a series of digital pixel signals by a predetermined pixel, and thinning processing means for down-sampling the series of digital pixel signals.

  The circuit configuration in the video scope can be simplified, noise generation and image quality degradation can be suppressed, the signal transmission speed to the processor can be stabilized, and the subject image of the desired color tone can be displayed regardless of the characteristics of the image sensor. Can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of a video scope in the electronic endoscope apparatus according to the present embodiment. FIG. 2 is a block diagram of a processor in the electronic endoscope apparatus.

  The electronic endoscope apparatus includes a video scope 10 having a CCD (Charge-Coupled Device) 12 and a processor 40 that processes an image signal sent from the video scope 10 and displays a subject image. A monitor 70 is connected to the processor 40. The video scope 10 is detachably connected to the processor 40, and when an examination, surgery, or the like is started, the insertion portion of the video scope 10 is inserted into the body.

  Light emitted from a lamp (not shown) provided in the processor 40 is emitted from the distal end portion 10 </ b> A of the videoscope 10 via a light guide (not shown) provided in the videoscope 10. Thereby, illumination light is irradiated to the observation region S.

  The light reflected from the observation region S reaches the light receiving region 12A of the CCD 12, and an optical image of the observation region S is thereby formed in the light receiving region 12A of the CCD 12. In the present embodiment, a single-plate simultaneous type is applied as a color imaging method, and yellow (Ye), cyan (Cy), magenta (Mg), and green (G) color elements are present on the light receiving region 12A of the CCD 12. The complementary color filters 13 arranged in a checkered pattern are arranged so as to correspond to the respective pixel positions of the light receiving region 12A. The color filter 13 is configured by regularly arranging blocks B including color elements Cy, Ye, Mg, and G as one unit. Here, the interline transfer method is applied as the charge transfer method, and the pixels (color elements) on the light receiving region 12A are arranged according to the interline transfer method.

  In the light receiving area 12A of the CCD 12, the optical image of the observation site S is converted into a series of analog pixel signals composed of a plurality of pixel signals corresponding to the colors passing through the color elements of the complementary color filter 13, and 1 frame / frame at a predetermined time interval. An image signal for one field is read out. In the present embodiment, the NTSC system is applied as the color television system, and image signals for one frame (one field every 1/60 second interval) are sequentially read out every 1/30 second interval. In addition, a color difference line sequential method is applied as a simultaneous single-plate type, and reading is performed while adding two pixels along the vertical direction, and signals are switched while alternately changing combinations of adjacent scanning lines in odd and even fields. read out. Thus, a series of analog pixel signals G1 + Y1, Mg1 + Cy1, G2 + Y2, Mg2 + Cy2,... Are output from the CCD 12 in a state where two adjacent pixels along the vertical direction of the CCD 12 are combined. The CCD drive circuit 17 outputs a clock pulse signal to the CCD 12 in order to read out a series of analog prime signals at a predetermined frequency.

  A series of read analog pixel signals is sent to the A / D conversion circuit 14. A series of analog pixel signals are converted into a series of digital pixel signals in accordance with a clock pulse signal having a frequency f (= 14 MHz). Here, each digital pixel signal is represented as 10-bit data. A series of digital pixel signals is sent to the signal output unit 24.

  In the signal output unit 24, a series of digital pixel signals output from the A / D conversion circuit 14 are separated in two directions, input to the downsampling circuit 18 via the pixel delay circuit 16, and the downsampling circuit 19 as it is. Sent to. In the pixel delay circuit 16, a delay process is performed for two pixels of the CCD 12 with respect to a series of digital pixel signals (hereinafter referred to as a first series of digital pixel signals). As a result, the first series of digital pixel signals is shifted by two pixels (G + Y) with respect to the series of digital pixel signals (hereinafter referred to as the second series of digital pixel signals) input to the downsampling 19. Yes.

  In the downsampling circuits 18 and 19, the first series of digital pixel signals is based on a clock frequency (= f / 2) that is half of the readout clock frequency (= f) of the pixel signals for the CCD 12 and the A / D conversion circuit 14. And downsampling processing (thinning-out processing) is performed on the second series of digital pixel signals. Here, the sampling timings for the downsampling circuits 18 and 19 are synchronized, and the first series of digital image signals are shifted by two pixels by the delay processing circuit 16, so that only the color elements G and Y are used. A pixel signal composed of pixel signals (hereinafter, referred to as a first color element-corresponding digital pixel signal (G1 + Y1, G2 + Y2,...)) Is output from the downsampling 18. On the other hand, the second series of digital pixel signals is referred to as a pixel signal composed of pixel signals corresponding to only the color elements Mg and G (hereinafter referred to as second color element corresponding digital pixel signals (Mg1 + Cy1, Mg2 + Cy2,...)). ) And output from the downsampling circuit 19.

  The first and second color element-corresponding digital pixel signals are converted from parallel signals to serial signals in serial conversion circuits 20 and 22, respectively. The first and second image signals subjected to serial conversion are output from the video scope 10 toward serial-parallel conversion circuits 42 and 44 in the processor 10, respectively.

  The memory 15 stores sensitivity information data of the CCD 12, and the data is read when connected to the processor 40. Here, the sensitivity information of the CCD 12 is pixel information regarding spectral transmission characteristics according to the material of the color filter 13 and the properties of the filler injected into the CCD 12. The spectral transmission characteristics (spectral distribution characteristics of transmitted light) arranged on the CCD differ depending on the type of the CCD, and for example, a specific color such as red or blue is emphasized. In the present embodiment, it is assumed that the spectral transmission characteristics are such that red and green are emphasized.

The digital pixel signals corresponding to the first and second color elements sent to the processor 40 are converted from serial signals to parallel signals in the serial-parallel conversion circuits 42 and 44, respectively, and sent to the addition circuit 46 and the subtraction circuit 48, respectively. It is done. In the adder circuit 46 and the subtractor circuit 48, first, the correction coefficients γ, δ, θ, and ε are multiplied to the first and second color element corresponding digital pixel signals.

(G1 + Y1) → γ × (G1 + Ye1)
(Mg1 + Cy1) → δ × (Mg1 + Cy1)
(G2 + Y2) → θ × (G2 + Ye2)
(Mg2 + Cy2) → ε × (Mg2 + Cy2) (1)

Thereby, the spectral transmission characteristics are corrected.

  Further, the addition circuit 46 adds the corrected first and second color element corresponding digital pixel signals to generate a luminance signal Y. On the other hand, in the subtraction circuit 48, the corrected first and second color element corresponding digital pixel signals are subtracted according to the scanning field (even field / odd field). As a result, the color signal Cr and the color signal Cb corresponding to blue in the nth scanning line corresponding to red (R) are generated. The luminance signal Y is sent to the R, G, B conversion circuit 52 as it is. On the other hand, the color signals Cb and Cr are sent to the RGB conversion circuit 52 via the one-line delay circuit 50 and are sent to the RGB conversion circuit 52 as they are.

In the RGB conversion circuit 52, primary color signals (R, G, B) are generated based on the luminance signal Y and the color difference signals Cb, Cr by matrix calculation using the following equations. However, α and β are matrix coefficients, and the color tone of the subject image is determined according to the value of the matrix coefficient.

R = Cr + α × Y
G = Y—Cr—Cb
B = Cb + β × (Y−Cr) (2)

The R, G, and B signals are stored in R, G, and B memories 54, 56, and 58, respectively, and then sent to a luminance / color difference signal (Y, RY, BY) conversion circuit 60.

  In the luminance / color difference signal conversion circuit 60, the luminance signal Y and the color difference signals (RY, BY) are generated based on the transmitted R, G, B signals. The luminance and color difference signals are converted into analog signals by the D / A conversion circuit 62 and then output to the monitor 70. As a result, the observation image is displayed on the monitor 70.

  The pulse generator 45 outputs a signal for reading out the digital pixel signal at a predetermined frequency to the CCD driving circuit 17 and the downsampling circuits 18 and 19.

  In the processor 40, a control signal is sent from the CPU 64 to the addition circuit 46, the subtraction circuit 48, and the R, G, B conversion circuit 52 based on the pixel information data sent from the video scope 10. Thereby, the values of correction coefficients γ, δ, θ, ε, α, and β for the digital pixel signal are determined. In the present embodiment, the correction coefficients γ, δ, θ, ε, α, and β are determined so that a subject image with a predetermined color tone is displayed regardless of the type of the CCD 12.

  As described above, according to the present embodiment, the signal output including the A / D conversion circuit 14, the pixel delay circuit 16, and the downsampling circuits 18 and 19 in the video scope 10 having the CCD 12 provided with the color filter 13. Part 24. A series of digital pixel signals output from the A / D conversion circuit 14 at a predetermined frequency f includes a first color element corresponding digital pixel signal composed of pixel signals corresponding to the color element (G + Y), and a color element ( The second color element-corresponding digital pixel signal composed of pixel signals according to (Mg + Cy), and in accordance with the transmission rate according to f / 2, the processor is directly separated via two signal lines. 40.

  Further, the video scope 10 stores data related to pixel sensitivity information in the memory 15, and when the data is read from the memory 15, the R, G, B primary color signals are corrected with correction coefficients γ, δ, θ, ε, It is generated according to the values of α and β. Then, a color video signal is generated based on the R, G, and B primary color signals.

  Since it is only necessary to provide a pixel delay circuit and a downsampling processing circuit in the video scope 10, the configuration of the scope-side signal processing circuit can be simplified. Also in the processor. There is no need to provide a pixel delay circuit and a downsampling circuit.

  Even when the types of the CCDs 12, that is, the video scopes 10 are different, it is possible to display a subject image with a certain color tone. In addition, since a digital pixel signal, not an analog pixel signal, is output to the processor 40, color adjustment can be performed in a state where no image quality deterioration has occurred.

  Since the digital pixel signal is separated and the transmission rate is lowered and the digital pixel signal is output to the processor 40, noise generation can be suppressed. In addition, a digital pixel signal can be output at a stable transmission rate without being affected by the number of pixels of the CCD 12. In particular, since serial data is transferred in parallel, noise generation can be reduced by reducing the number of signal lines, and a digital pixel signal can be output at a constant transmission rate.

  In this embodiment, the color difference line sequential method is applied, but other pixel readout methods may be applied. In addition, a primary color filter may be applied to the color filter instead of the complementary color filter. That is, a filter in which a plurality of color elements are regularly arranged may be used.

  Instead of serial transmission, the parallel signal may be output to the processor 40. Further, the digital pixel signal may be separated and the output timing adjusted by a configuration other than the pixel delay circuit and the downsizing circuit.

  Only the matrix coefficient of the R, G, B conversion circuit or the correction coefficient in the addition / subtraction circuit may be adjusted.

It is a block diagram of the video scope in the electronic endoscope apparatus which is this embodiment. It is a block diagram of the processor in an electronic endoscope apparatus.

Explanation of symbols

10 Videoscope 12 CCD (Image sensor)
13 Color filter 14 A / D conversion circuit (digital conversion means)
15 memory 16 pixel delay circuit 17 CCD drive circuit (signal reading means)
18, 19 Downsampling circuit 24 Signal output unit (digital pixel signal output means)
40 processor 46 addition circuit 48 subtraction circuit 52 R, G, B conversion circuit α, β matrix coefficient

Claims (6)

An electronic endoscope apparatus having a video scope and a processor,
The video scope is
An image pickup device having a plurality of color elements related to a color video signal and provided with a color filter configured by regularly arranging blocks of cyan, magenta, green, and yellow, which are four color elements When,
A signal for reading a series of analog pixel signals from the image sensor by adding two pixels along the vertical direction while alternately changing the combination of adjacent scanning lines in the odd and even fields according to the color difference line sequential method. Reading means;
Digital conversion means for converting the series of analog pixel signals into a series of digital pixel signals according to a clock pulse signal having a predetermined frequency;
The series of digital pixel signals includes a first color element corresponding digital pixel signal corresponding to two color elements of green, yellow, cyan, and magenta, and a second color element corresponding to the remaining two color elements. A digital pixel signal output that is separated into digital pixel signals and outputs the digital pixel signals corresponding to the first and second color elements to the outside separately through two transmission paths in accordance with a clock pulse signal having a frequency lower than the predetermined frequency. Means,
A memory for storing data relating to pixel sensitivity information of the image sensor,
The processor is
Based on the data related to the pixel sensitivity information, a color video signal is generated from the first and second color element-corresponding digital pixel signals so as to display a subject image in a predetermined color tone regardless of the pixel sensitivity characteristics of the image sensor. An electronic endoscope apparatus comprising a video signal generating means. The digital pixel signal output means comprises:
Pixel delay means for delaying the series of digital pixel signals by two pixels;
Previous SL series of digital pixel signals and said pixel delay a series of pixel signals were, electrons in the claim 1, characterized in that it comprises a thinning processing means for down-sampling according to the frequency of half said predetermined frequency Endoscopic device. The first color element corresponding digital pixel signal is a pixel signal corresponding to green and yellow color elements, and the second color element corresponding digital pixel signal is a pixel signal corresponding to cyan and magenta. The electronic endoscope apparatus according to claim 1, wherein the electronic endoscope apparatus is characterized. The video signal generation means is
Correction coefficient setting means for setting a correction coefficient of the first and second color element corresponding digital pixel signals according to the data of the pixel sensitivity information;
An addition / subtraction circuit that multiplies the correction coefficient corresponding to the plurality of color element-corresponding digital pixel signals to generate luminance and color signals, and
Matrix coefficient setting means for setting a matrix coefficient in accordance with the pixel sensitivity information data;
The electronic endoscope according to claim 1, further comprising: an R, G, B conversion circuit that converts the luminance and color signals into R, G, and B primary color signals by matrix calculation according to set matrix coefficients. apparatus. An image pickup device having a plurality of color elements related to a color video signal and provided with a color filter configured by regularly arranging blocks of cyan, magenta, green, and yellow, which are four color elements When,
A signal for reading a series of analog pixel signals from the image sensor by adding two pixels along the vertical direction while alternately changing the combination of adjacent scanning lines in the odd and even fields according to the color difference line sequential method. Reading means;
Digital conversion means for converting the series of analog pixel signals into a series of digital pixel signals according to a clock pulse signal having a predetermined frequency;
The series of digital pixel signals includes a first color element corresponding digital pixel signal corresponding to two color elements of green, yellow, cyan, and magenta, and a second color element corresponding to the remaining two color elements. A digital pixel signal output that is separated into digital pixel signals and outputs the digital pixel signals corresponding to the first and second color elements to the outside separately through two transmission paths in accordance with a clock pulse signal having a frequency lower than the predetermined frequency. Means,
A video scope of an electronic endoscope apparatus, comprising: a memory that stores data relating to pixel sensitivity information of the image sensor. A processor connected to the video scope of the electronic endoscope apparatus according to claim 5,
Based on the data related to the pixel sensitivity information, a color video signal is generated from the first and second color element-corresponding digital pixel signals so as to display a subject image in a predetermined color tone regardless of the pixel sensitivity characteristics of the image sensor. A processor for an electronic endoscope apparatus, comprising a video signal generating means.

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