Abstract:
An endoscope apparatus comprises: an endoscope comprising an imaging device that forms color image signals of a body to be observed; a Y/C signal processing circuit that forms brightness/color difference signals from a color image signal obtained by the imaging device; a storage portion that stores Y/C matrix data for forming a spectral image based on the brightness/color difference signals; and a Y/C spectral image forming circuit that conducts matrix calculation by the Y/C matrix data of the storage portion and the brightness/color difference signals output from the Y/C signal processing circuit and forms a spectral image of an arbitrarily selected wavelength range.

Description:
This Nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). JP 2005-060199 filed in Japan on Mar. 4, 2005, the entire contents of which is hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an endoscope apparatus, more particularly, a constitution used in medical fields for forming and displaying a spectral image (video) made up of image information of arbitrarily selected wavelength ranges. 
   2. Description of the Related Art 
   Recently, in a electronic endoscope apparatus which uses a solid imaging device, spectral imaging combined with a narrow band pass filter on the basis of a spectral reflectance in alimentary canal (gastric mucosa and the like), namely, a narrow band filter built-in an electronic endoscope apparatus (Narrow Band Imaging-NBI) has become the focus of attention. In place of rotational filters of R (red), G (green) and B (blue) by a frame sequential method, this system is provided with band pass filters of three narrow bands (wavelengths), outputs sequentially illumination light via these narrow bandpass filters, and conducts processing the same as in the case of red (R), green (G) and blue (B) signals while changing respective weightings to three signals obtained from these illumination lights, thereby forming a spectral image. This spectral image is able to realize micro-structures and the like in gastrointestinal tracts such as the stomach and large intestine, which would otherwise not be realized. 
   In contrast, unlike the frame sequential method using the above-described narrow band pass filters, as described in Japanese Published Unexamined Patent Application No. 2003-93336, it has been proposed that in the simultaneous method in which micro-mosaic color filters are arranged on a solid imaging device, a spectral image is formed by the computing process on the basis of image signals obtained from white light. In this method, the relationship between numeric data of the respective R, G, and B color sensitivity characteristics and numeric data of spectral characteristics of a specific narrow bandpass is determined as matrix data (coefficient sets) and computing is made for the matrix data and the R, G and B signals to obtain spectral image signals artificially via the narrow bandpass filters. Where a spectral image is formed by such computing, it is not necessary to provide a plurality of filters corresponding to desired wavelength ranges and to provide these change-over arrangements, thereby successfully avoiding increases in the size of a system and reducing cost. 
   However, in forming a spectral image by the endoscope apparatus, underlying color image signals are R (red), G (green) and B (blue) signals. When a solid imaging device is used, for example, a complementary color-type CCD having color filters Mg, Ye, Cy and G, Mg (magenta), Ye (yellow), Cy (cyan), and G (green) signals are often converted to a brightness (Y) signal and a color difference (C) signal (Y/C signals) for processing. Also, the Y/C signals must be subjected to color conversion to RGB signals. Further, where an elementary color-type CCD having RGB color filters is used, RGB signals are converted to Y/C signals due to matters related to a variety of signal processings and circuit configurations at subsequent steps. In this case, it is necessary to make RGB signals from Y/C signals. Such color conversion processings are in principle redundant, and such a problem is brought about whereby repeated color conversion may cause deterioration in quality of images and complicate the circuit configuration. 
   On the other hand, recently, endoscope apparatuses in which different types of endoscopes (scope) are connected to a single endoscope have been used. In this case, Y/C signals or RGB signals are outputted from the endoscope, and a spectral image may not be formed depending on output formats of the endoscope. Therefore, user-friendly endoscope apparatuses have been demanded in view of such circumstances. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in view of the above problem, and an object of the invention is to provide a user-friendly endoscope apparatus capable of forming a spectral image directly from Y/C signals and also obtaining a spectral image from either Y/C signals or RGB signals. 
   In order to attain the above object, an endoscope apparatus according to the first aspect of the invention comprises an endoscope comprising an imaging device that forms color image signals of a body to be observed; a Y/C signal processing circuit that forms brightness/color difference signals from a color image signal obtained by the imaging device; a first storage portion that stores Y/C matrix data for forming a spectral image based on the brightness/color difference signals; and a Y/C spectral image forming circuit that conducts matrix calculation by the Y/C matrix data of the storage portion and the brightness/color difference signals output from the Y/C signal processing circuit and forms a spectral image of an arbitrarily selected wavelength range. 
   An endoscope apparatus according to the second aspect of the invention comprises: an endoscope comprising an imaging device that forms color image signals of a body to be observed; an image signal processing circuit comprising one of (i) a Y/C signal processing circuit that forms brightness/color difference signals from a color image signal obtained from the imaging device and (ii) an RGB signal processing circuit that forms RGB signals from a color image signal obtained from the imaging device; a first storage portion that stores Y/C matrix data for forming a spectral image based on the brightness/color difference signals; a Y/C spectral image forming circuit that conducts matrix calculation by the Y/C matrix data of the storage portion and the brightness/color difference signals output from the Y/C signal processing circuit and forms a spectral image of a first arbitrarily selected wavelength range; a second storage portion that stores RGB matrix data for forming a spectral image based on the RGB signals (the first and second storage portions may be the same or different); and an RGB spectral image forming circuit that conducts matrix calculation by the RGB matrix data of the storage portion and the RGB signals output from the RGB signal processing circuit and forms a spectral image of a second arbitrarily selected wavelength range, wherein either the Y/C spectral image forming circuit or the RGB spectral image forming circuit can be selected. 
   An endoscope apparatus according to the third aspect of the invention comprises a processor unit detachably connected to the endoscope on the second aspect of the invention, wherein the image signal processing circuit is disposed in the endoscope, both of the Y/C spectral image forming circuit and the RGB spectral image forming circuit are disposed in the processor unit, and in the processor unit, either the Y/C spectral image forming circuit or the RGB spectral image forming circuit is selected based on an identification information on the endoscope. 
   In the above constitution according to the first aspect of the invention, since the relationship (conversion coefficient) between the Y/C signals of brightness (Y)/color difference (R−Y and B−Y) and the RGB signals has been conventionally known, matrix coefficients for computing λ1, λ2 and λ3 signals of the selected wavelength range from the Y/C signals have been previously determined on the basis of the relationship mentioned above and the relationship (conversion coefficient) between the λ1, λ2 and λ3 signals of the selected wavelength range and the RGB signals. The matrix data (coefficient sets) is stored in a computing memory on the processor unit. Then, when an operator selects three-wavelength ranges (narrow band) (one wavelength range may be selected) for forming a spectral image, matrix data corresponding to the three-wavelength ranges is read from the memory. Then, λ1, λ2 and λ3 signals are formed by the matrix data and the Y/C signals output from the DSP and others, thereby making it possible to display on a monitor the spectral image in combination with the three-wavelength ranges selected. 
   Further, in the above constitutions according to the second and third aspects of the invention, the processor unit connected to the endoscope can include both the Y/C spectral image forming circuit and the RGB spectral image forming circuit. Where, for example, the endoscope connected thereto outputs Y/C signals or RGB signals, spectral images respectively corresponding thereto can be formed. In addition, there is a case where the Y/C signals and the RGB signals are formed during signal processing in a single processor unit. In this case, it is possible to form a spectral image from both of these signals, whenever appropriate. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing the constitution of the endoscope apparatus according to the embodiment 1 of the present invention; 
       FIG. 2  is a graph showing one example of the wavelength range of spectral images formed in the embodiment 1, together with the spectral sensitivity characteristics of the complementary color-type CCD; 
       FIG. 3  is a graph showing one example of the wavelength range of spectral images formed in the embodiment 1, together with the reflection spectrum of a living body; and 
       FIG. 4  is a block diagram showing the constitution of the endoscope apparatus in the embodiment 2. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a constitution of the electronic endoscope apparatus of the embodiment 1. As shown in  FIG. 1 , the electronic endoscope apparatus is constituted so that a scope (electronic endoscope)  10  is connected to a processor unit  12  in a freely attachable and detachable way and a light source  14  is arranged on the processor unit  12 . Further, there is a case where the light source  14  is arranged on a light source unit, which is a separate body. The scope  10  is provided on the end with a CCD  15  which is a solid imaging device, and a complementary color-type CCD having, for example, color filters of Mg, Ye and Cy are used as the CCD  15  on an imaging surface. 
   The CCD  15  is provided with a CCD driving circuit  16  for forming a driving pulse on the basis of synchronizing signals, a CDS/AGC (correlated dual sampling/automatic gain control) circuit  17  for sampling and amplifying an image (video) signal input from the CCD  15  the image signal and an A/D converter  18 . Also provided are a microcomputer  20  and a memory (ROM)  21  for controlling various circuits inside the scope  10  and also controlling communications with the processor unit  12 . Identification information on the type of color filters of the CCD  15  (complementary color-type CCD or elementary color-type CCD) and the signal output mode is stored in the memory  21 . Further, the scope  10  is provided at the end with an illumination window  23 , and the illumination window  23  is connected to the light source  14  by a light guide  24 . 
   The processor unit  12  is provided with a DSP (digital signal processor)  25  (corresponding to the Y/C signal processing circuit) which imparts a variety of image processings to digitally converted image signals. In the DSP  25 , Y/C signals constituted by a brightness (Y) signal and a color difference [C(R−Y,B−Y)] signal are formed and output from output signals (Mg, Ye, Cy and G signals) of the CCD  15 . The DSP  25  is provided with a color space conversion processing circuit  29  (corresponding to the Y/C spectral image forming circuit) for conducting matrix calculation for a spectral image via the selector  26  (other terminal). The spectral image signals of selected wavelength ranges of λ1, λ2 and λ3 are output from a color space conversion processing circuit  29 . At the post-stage of the color space conversion processing circuit  29 , a mode selector  30  for selecting either the spectral image (monochrome mode) made up of one wavelength range (narrow band) or the spectral image (three-color mode) made up of three wavelength ranges (the mode selector may be provided with a two color mode by which two colors are selected), a color conversion circuit  31  for inputting image signals (λ1, λ2 and λ3) made up of one wavelength range or three wavelength ranges as Rs, Gs and Bs signals in order to conduct a processing which corresponds to conventional RGB signals and for converting these Rs, Gs and Bs signals to Y/C signals, and a signal processing circuit  32  for conducting a variety of other signal processing (mirror image process, mask generation, character generation and the like), and a D/A converter  33 . Further, the DSP  25  may be arranged on the scope  10 . 
   A microcomputer  35  is also provided which communicates with the scope  10  and also controls various circuits inside the processor unit  12 , reading matrix data from a memory  36  (corresponding to the first storage portion) to supply the data to the color space conversion processing circuit  29 . Matrix (coefficient) data table) for forming a spectral image on the basis of Y/C signals are stored in the memory  36 . According to the embodiment, table 1 below shows one example of the matrix data accommodated in the memory  36 . 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
               TABLE 1 
             
             
                 
                 
             
             
                 
               Parameter 
               k py   
               k pcr   
               k pcb   
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               p1 
               0.000008 
               −0.0002 
               0.000802 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               p18 
               0.00241 
               0.006147 
               −0.00289 
             
             
                 
               p19 
               0.00603 
               0.005843 
               −0.00294 
             
             
                 
               p20 
               0.001037 
               0.005427 
               −0.00294 
             
             
                 
               p21 
               0.001549 
               0.004912 
               −0.00288 
             
             
                 
               p22 
               0.002132 
               0.004283 
               −0.00277 
             
             
                 
               p23 
               0.002767 
               0.003563 
               −0.00263 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               p43 
               0.00708 
               −0.00139 
               −0.00149 
             
             
                 
               p44 
               0.007294 
               −0.00165 
               −0.0014 
             
             
                 
               p45 
               0.007484 
               −0.00188 
               −0.00132 
             
             
                 
               p46 
               0.007638 
               −0.00206 
               −0.00124 
             
             
                 
               p47 
               0.007732 
               −0.00219 
               −0.00116 
             
             
                 
               p48 
               0.007792 
               −0.00228 
               −0.00108 
             
             
                 
               p49 
               0.007834 
               −0.00234 
               −0.00102 
             
             
                 
               p50 
               0.007864 
               −0.00237 
               −0.00098 
             
             
                 
               p51 
               0.007903 
               −0.00238 
               −0.00097 
             
             
                 
               p52 
               0.007956 
               −0.00238 
               −0.00097 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               p61 
               0.008051 
               −0.00216 
               −0.00094 
             
             
                 
                 
             
           
        
       
     
   
   Matrix data shown in the above Table 1 is made up of 61-wavelength range parameters (coefficient sets) p1 to p61 in which, for example, the wavelength range from 400 nm to 700 nm is divided at 5 nm intervals. The parameters p1-p61 are constituted by coefficients, k py , k pcr  and k pcb  (p corresponds to p1-p61) for matrix calculation. 
   Then, in the color space conversion processing circuit  29 , matrix calculation is conducted according to the following mathematical formula 1 represented by the coefficients k py , k pcr  and k pcb , and Y/C signals (R−Y=Cr and B−Y=Cb) output from the DSP  25 . 
   
     
       
         
           
             
               
                 
                   [ 
                   
                     
                       
                         
                           λ 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                     
                     
                       
                         
                           λ 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                     
                     
                       
                         
                           λ 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           3 
                         
                       
                     
                   
                   ] 
                 
                 = 
                 
                   
                     [ 
                     
                       
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                             ⁢ 
                             y 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                             ⁢ 
                             cr 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             cb 
                           
                         
                       
                       
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             y 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                             ⁢ 
                             cr 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                             ⁢ 
                             cb 
                           
                         
                       
                       
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             3 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             y 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             3 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             cr 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             3 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             cb 
                           
                         
                       
                     
                     ] 
                   
                   × 
                   
                     [ 
                     
                       
                         
                           y 
                         
                       
                       
                         
                           Cr 
                         
                       
                       
                         
                           Cb 
                         
                       
                     
                     ] 
                   
                 
               
             
             
               
                 [ 
                 
                   Mathematical 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Formula 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
                 ] 
               
             
           
         
       
     
   
   More specifically, where, for example, the parameter p21 (center wavelength 500 nm), p45 (center wavelength 620 nm) and p51 (center wavelength 650 nm) shown in Table 1 are selected as λ1, λ2 and λ3, (−0.001549, 0.004912, −0.00288) of p21, (0.007484, −0.00188, −0.00132) of p45 and (0.007903, −0.00238, −0.00097) of p51 may be substituted as coefficients (k py , k pcr  and k pcb ). 
   Further, a color signal processing circuit  38  for forming ordinary color images (videos) not for spectral images and a D/A converter  39  are connected and arranged on the other terminal of the selector  26 . 
   The embodiment 1 is constituted as described above. In the scope  10  shown in  FIG. 1 , the CCD driving circuit  16  drives the CCD  15 , by which imaging signals of a body to be observed are output from the CCD  15 . The signals are subjected to the correlated dual sampling and amplification at the CDS/AGC circuit  17 , and then supplied via the A/D converter  18  to the DSP  25  of the processor unit  12  as a digital signal. In the DSP  25 , gamma processing is given to output signals from the scope  10  and also color conversion processing is given to signals obtained via color filters of Mg, Ye, Cy and G, thereby forming Y/C signals made up of a brightness (Y) signal and a color difference (R−Y,B−Y) signal. Output of the DSP  25  is usually supplied to the color signal processing circuit  38  by the selector  26 . The output is subjected to the signal processing similar to the conventional processing and supplied via the D/A converter  39  to a monitor and color images of an ordinary body to be observed are displayed on the monitor. 
   Upon depression of an operating switch arranged on an operation portion and others for forming spectral images, the selector  26  changes Y/C signals output from the DSP  25  so as to supply them to a color space conversion processing circuit  29 . At this time, an operator selects three wavelength ranges corresponding to signals of λ1, λ2 and λ3, and the microcomputer  35  reads matrix (coefficient) data corresponding to three selected wavelength ranges from the memory  36  (Table 1) and supplies the data to a color space conversion processing circuit  29 . 
   In the color space conversion processing circuit  29 , in order to form spectral images, matrix calculation is conducted according to the above mathematical formula 1. Where p21 (center wavelength 500 nm), p45 (center wavelength 620 nm) and p51 (center wavelength 652 nm) are selected, for example, as three wavelength ranges (λ1, λ2 and λ3), signals λ1, λ2 and λ3 are determined by matrix calculation according to the following mathematical formula 2 represented by RGB signals. 
   
     
       
         
           
             
               
                 
                   [ 
                   
                     
                       
                         
                           λ 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                     
                     
                       
                         
                           λ 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                     
                     
                       
                         
                           λ 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           3 
                         
                       
                     
                   
                   ] 
                 
                 = 
                 
                   
                     [ 
                     
                       
                         
                           
                             - 
                             0.001549 
                           
                         
                         
                           0.004912 
                         
                         
                           
                             - 
                             0.00288 
                           
                         
                       
                       
                         
                           0.007484 
                         
                         
                           
                             - 
                             0.00188 
                           
                         
                         
                           
                             - 
                             0.00132 
                           
                         
                       
                       
                         
                           0.007903 
                         
                         
                           
                             - 
                             0.00238 
                           
                         
                         
                           
                             - 
                             0.00097 
                           
                         
                       
                     
                     ] 
                   
                   × 
                   
                     [ 
                     
                       
                         
                           Y 
                         
                       
                       
                         
                           Cr 
                         
                       
                       
                         
                           Cb 
                         
                       
                     
                     ] 
                   
                 
               
             
             
               
                 [ 
                 
                   Mathematical 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   formula 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
                 ] 
               
             
           
         
       
     
   
   Then, where a three-color mode is selected by the mode selector  30 , the above signals of λ1, λ2 and λ3 are supplied to the color conversion circuit  31  as signals of Rs (=λ1), Gs (=λ2) and Bs (=λ3). Where a monochrome mode is selected, any one of the above signals of λ1, λ2 and λ3 is supplied to the color conversion circuit  31  as the signal of Rs (=λ2), Gs (=λ2) or Bs (=λ2) (for example, λ2 is selected). In the color conversion circuit  31 , signals of λ1, λ2 and λ3 as Rs, Gs and Bs signals are converted to Y/C signals (Y, Rs−Y and Bs−Y), and the Y/C signals are supplied to a monitor and others via the signal processing circuit  32  and the D/A converter  33 . 
   As described above, spectral images displayed on a monitor and others are constituted by color components of the wavelength ranges shown in  FIG. 2  and  FIG. 3 . More specifically,  FIG. 2  is a conceptual diagram in which three wavelength ranges forming spectral images are superimposed on the spectral sensitivity characteristics of color filters on the CCD  15  (complementary color-type CCD) (the color filter is not in agreement with the sensitivity graduation of wavelength ranges corresponding to λ1, λ2 and λ3 signals). Further,  FIG. 3  is a conceptual diagram in which three wavelength ranges are superimposed on the reflection spectrum of a living body. The wavelengths of p21, p45 and p51 selected as λ1, λ2 and λ3 signals in the embodiment 1 are color signals having the wavelength range of approximately ±10 nm, with the center wavelength being 500 nm, 620 nm and 650 nm in sequence, as illustrated in the diagram. Displayed are spectral images (moving image and still image) constituted by a combinations of colors of the three wavelength ranges. 
   Next, a description is given for case in which the above matrix coefficient data (Y/C matrix data) shown in Table 1 can be determined from the matrix coefficients (RGB matrix data) where spectral images are formed by matrix calculation for RGB signals. More specifically, in general, the relationships between the RGB signals and the Y/C signals are expressed by the following mathematical formulae 3 and 4. 
   
     
       
         
           
             
               
                 
                   [ 
                   
                     
                       
                         R 
                       
                     
                     
                       
                         G 
                       
                     
                     
                       
                         B 
                       
                     
                   
                   ] 
                 
                 = 
                 
                   
                     [ 
                     
                       
                         
                           Ry 
                         
                         
                           Rr 
                         
                         
                           Rb 
                         
                       
                       
                         
                           Gy 
                         
                         
                           Gr 
                         
                         
                           Gb 
                         
                       
                       
                         
                           By 
                         
                         
                           Br 
                         
                         
                           Bb 
                         
                       
                     
                     ] 
                   
                   × 
                   
                     [ 
                     
                       
                         
                           Y 
                         
                       
                       
                         
                           Cr 
                         
                       
                       
                         
                           Cb 
                         
                       
                     
                     ] 
                   
                   ⁢ 
                   
                     ( 
                     
                       
                         [ 
                         
                           
                             
                               Ry 
                             
                             
                               Rr 
                             
                             
                               Rb 
                             
                           
                           
                             
                               Gy 
                             
                             
                               Gr 
                             
                             
                               Gb 
                             
                           
                           
                             
                               By 
                             
                             
                               Br 
                             
                             
                               Bb 
                             
                           
                         
                         ] 
                       
                       = 
                       
                         [ 
                         
                           
                             
                               1.164 
                             
                             
                               0 
                             
                             
                               1.596 
                             
                           
                           
                             
                               1.164 
                             
                             
                               
                                 - 
                                 0.391 
                               
                             
                             
                               
                                 - 
                                 0.813 
                               
                             
                           
                           
                             
                               1.164 
                             
                             
                               2.018 
                             
                             
                               0 
                             
                           
                         
                         ] 
                       
                     
                     ) 
                   
                   ⁢ 
                   
                       
                       
                   
                 
               
             
             
               
                 [ 
                 
                   Mathematical 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Formula 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   3 
                 
                 ] 
               
             
           
           
             
               
                 
                   [ 
                   
                     
                       
                         Y 
                       
                     
                     
                       
                         Cr 
                       
                     
                     
                       
                         Cb 
                       
                     
                   
                   ] 
                 
                 = 
                 
                   
                     [ 
                     
                       
                         
                           Yr 
                         
                         
                           Yg 
                         
                         
                           Yb 
                         
                       
                       
                         
                           Crr 
                         
                         
                           Crg 
                         
                         
                           Crb 
                         
                       
                       
                         
                           Cbr 
                         
                         
                           Cbg 
                         
                         
                           Cbb 
                         
                       
                     
                     ] 
                   
                   × 
                   
                     [ 
                     
                       
                         
                           R 
                         
                       
                       
                         
                           G 
                         
                       
                       
                         
                           B 
                         
                       
                     
                     ] 
                   
                   ⁢ 
                   
                     ( 
                     
                       
                         [ 
                         
                           
                             
                               Yr 
                             
                             
                               Yg 
                             
                             
                               Yb 
                             
                           
                           
                             
                               Crr 
                             
                             
                               Crg 
                             
                             
                               Crb 
                             
                           
                           
                             
                               Cbr 
                             
                             
                               Cbg 
                             
                             
                               Cbb 
                             
                           
                         
                         ] 
                       
                       = 
                       
                         [ 
                         
                           
                             
                               
                                 
                                     
                                 
                                 ⁢ 
                                 .257 
                               
                             
                             
                               
                                 
                                     
                                 
                                 ⁢ 
                                 .501 
                               
                             
                             
                               
                                 
                                     
                                 
                                 ⁢ 
                                 .098 
                               
                             
                           
                           
                             
                               
                                 - 
                                 
                                     
                                 
                                 ⁢ 
                                 .148 
                               
                             
                             
                               
                                 - 
                                 
                                     
                                 
                                 ⁢ 
                                 .291 
                               
                             
                             
                               
                                 
                                     
                                 
                                 ⁢ 
                                 .439 
                               
                             
                           
                           
                             
                               
                                 
                                     
                                 
                                 ⁢ 
                                 .439 
                               
                             
                             
                               
                                 - 
                                 
                                     
                                 
                                 ⁢ 
                                 .368 
                               
                             
                             
                               
                                 - 
                                 
                                     
                                 
                                 ⁢ 
                                 .071 
                               
                             
                           
                         
                         ] 
                       
                     
                     ) 
                   
                 
               
             
             
               
                 [ 
                 
                   Mathematical 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Formula 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   4 
                 
                 ] 
               
             
           
         
       
     
   
   Then, when consideration is given to signals of λ1, λ2 and λ3 of narrow band image (NBI), matrix calculation based on RGB signals is represented by the following mathematical formula 5, and between the Y/C signals and λ1, λ2 and λ3 signals, the following mathematical formula 6 is established. 
                   [           λ   ⁢           ⁢   1               λ   ⁢           ⁢   2               λ   ⁢           ⁢   3           ]     =       [           k   ⁢           ⁢   1   ⁢   r           k   ⁢           ⁢   1   ⁢   g           k   ⁢           ⁢   1   ⁢           ⁢   b               k   ⁢           ⁢   2   ⁢           ⁢   r           k   ⁢           ⁢   2   ⁢   g           k   ⁢           ⁢   2   ⁢   b               k   ⁢           ⁢   3   ⁢           ⁢   r           k   ⁢           ⁢   3   ⁢           ⁢   g           k   ⁢           ⁢   3   ⁢           ⁢   b           ]     ×     [         R           G           B         ]               [     Mathematical   ⁢           ⁢   Formula   ⁢           ⁢   5     ]                 [         Y           Cr           Cb         ]     =       [         Yr         Yg   ,         Yb           Crr       Crg       Crb           Cbr       Cbg       Cbb         ]     ×     [           λ   ⁢           ⁢   1               λ   ⁢           ⁢   2               λ   ⁢           ⁢   3           ]               [     Mathematical   ⁢           ⁢   Formula   ⁢           ⁢   6     ]               
The above mathematical formulae 5 and 6 are summarized to give the following mathematical formula 7.
 
   
     
       
         
           
             
               
                 
                   [ 
                   
                     
                       
                         Y 
                       
                     
                     
                       
                         Cr 
                       
                     
                     
                       
                         Cb 
                       
                     
                   
                   ] 
                 
                 = 
                 
                   
                     [ 
                     
                       
                         
                           Yr 
                         
                         
                           Yg 
                         
                         
                           Yb 
                         
                       
                       
                         
                           Crr 
                         
                         
                           Crg 
                         
                         
                           Crb 
                         
                       
                       
                         
                           Cbr 
                         
                         
                           Cbg 
                         
                         
                           Cbb 
                         
                       
                     
                     ] 
                   
                   × 
                   
                       
                   
                   ⁢ 
                   
                     
 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     [ 
                     
                       
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             r 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             g 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             b 
                           
                         
                       
                       
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             r 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             g 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             b 
                           
                         
                       
                       
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             3 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             r 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             3 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             g 
                           
                         
                         
                           
                             k 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             3 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             b 
                           
                         
                       
                     
                     ] 
                   
                   ⁢ 
                   
                       
                     
                       × 
                       
                         [ 
                         
                           
                             
                               R 
                             
                           
                           
                             
                               G 
                             
                           
                           
                             
                               B 
                             
                           
                         
                         ] 
                       
                     
                   
                 
               
             
             
               
                 [ 
                 
                   Mathematical 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Formula 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   7 
                 
                 ] 
               
             
           
         
       
     
   
   Therefore, as is apparent from the mathematical formula 7, the matrix coefficients shown in Table 1 according to the embodiment are determined by RGB matrix data (data of Table 2 to be explained later) and coefficients of the mathematical formula 4. 
     FIG. 4  shows the constitution of the endoscope apparatus according to the embodiment 2, which is designed so that a spectral image can be formed by both Y/C signals and RGB signals. As shown in  FIG. 4 , the endoscope apparatus according to the embodiment 2 is provided with, for example, a scope  10 A having an elementary color-type CCD  15 A with RGB color filters and DSP  25 A (corresponding to the RGB signal processing circuit) which outputs RGB signals as a color image signal, a scope  10 B having an elementary color-type CCD  15 B and DSP  25 B (corresponding to the Y/C signal processing circuit) which converts RGB signals through color conversion processing to Y/C signals for output, and a scope  10 C having a complementary color-type CCD  15 C with Mg, Ye, Cy and G color filters and DSP  25 C (corresponding to the Y/C signal processing circuit) which converts Mg, Ye, Cy and G signals through the color conversion processing to Y/C signals for output. 
   The processor  42  is provided with a color space conversion processing circuit  29  (corresponding to the Y/C spectral image forming circuit) for conducting matrix calculation for Y/C signals via the selector  43  as with the embodiment 1, a mode selector  30 A and a color conversion circuit  31 A for converting Rs, Gs and Bs signals to which λ1, λ2 and λ3 signals are substituted, as they are, to Y/C signals as a Y/C spectral image forming circuit. It is also provided with a color space conversion processing circuit  44  (corresponding to the RGB spectral image forming circuit) for conducting matrix calculation for RGB signals as an RGB spectral image forming circuit, a mode selector  30 B and a color conversion circuit  31 B for converting Rs, Gs and Bs signals (λ1, λ2 and λ3 signals) to Y/C signals. Further, the Y/C matrix data Pc shown in the above Table 1 and the RGB matrix data Pd shown in the following Table 2 are stored in the memory  36  (corresponding to the first and second storage portions) which is connected to the microcomputer  35 . 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
               TABLE 2 
             
             
                 
                 
             
             
                 
               Parameter 
               k pr   
               k pg   
               k pb   
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               p1 
               0.000083 
               −0.00188 
               0.003592 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               p18 
               −0.00115 
               0.000569 
               0.003325 
             
             
                 
               p19 
               −0.00118 
               0.001149 
               0.002771 
             
             
                 
               p20 
               −0.00118 
               0.001731 
               0.0022 
             
             
                 
               p21 
               −0.00119 
               0.002346 
               0.0016 
             
             
                 
               p22 
               −0.00119 
               0.00298 
               0.000983 
             
             
                 
               p23 
               −0.00119 
               0.003633 
               0.000352 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               p43 
               0.003236 
               0.001377 
               −0.00159 
             
             
                 
               p44 
               0.003656 
               0.000671 
               −0.00126 
             
             
                 
               p45 
               0.004022 
               0.000068 
               −0.00097 
             
             
                 
               p46 
               0.004342 
               −0.00046 
               −0.00073 
             
             
                 
               p47 
               0.00459 
               −0.00088 
               −0.00051 
             
             
                 
               p48 
               0.004779 
               −0.00121 
               −0.00034 
             
             
                 
               p49 
               0.004922 
               −0.00148 
               −0.00018 
             
             
                 
               p50 
               0.005048 
               −0.00172 
               −3.6E−05 
             
             
                 
               p51 
               0.005152 
               −0.00192 
               0.000088 
             
             
                 
               p52 
               0.005215 
               −0.00207 
               0.000217 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               . 
               . 
               . 
               . 
             
             
                 
               p61 
               0.00548 
               −0.00229 
               0.00453 
             
             
                 
                 
             
           
        
       
     
   
   As with the matrix data Pc shown in Table 1, the matrix data Pd in Table 2 is also data in which the wavelength range from 400 nm to 700 nm is divided into 61 wavelength range parameters (coefficient sets) p1 to p61 and constituted by the matrix coefficients k pr , k pg  and k pb  corresponding to these parameters p1 to p61. In the color space conversion processing circuit  44 , matrix calculation is conducted according to the above mathematical formula 5 represented by the coefficients k pr , k pg  and k pb  and RGB signals input from the endoscope  10 A, thereby forming a spectral image. 
   More specifically, where the parameter p21 (center wavelength 500 nm), p45 (center wavelength 620 nm) and p51 (center wavelength 650 nm) shown in Table 2 are selected as with the above, (−0.00119, 0.002346, 0.0016) of p21, (0.004022, 0.000068, −0.00097) of p45 and (0.005152, −0.00192, 0.000088) of p51 may be substituted as coefficients (k pr , k pg  and k pb ). 
   The embodiment 2 is constituted as described above. When any one of the scopes  10 A to  10 C shown in  FIG. 4  is connected to the processor unit  42 , the microcomputer  35  of the processor unit  42  makes communications with the microcomputer ( 20 ) of the scopes  10 A to  10 C, thereby obtaining the identification information on the signal output mode of these scopes. When the selector  43  is changed on the basis of the information and the scope  10 A is connected, a color space conversion processing circuit  44  is selected. In this instance, RGB matrix data Pd is read from the memory  36 , and a spectral image is formed by λ1, λ2 and λ3 signals of three wavelength ranges (three-color mode) or of one wavelength range (monochrome mode) selected by the matrix data Pd and RGB signals. 
   On the other hand, where the scope  10 B or  10 C, is connected, the selector  43  selects the color space conversion processing circuit  29 . In this instance, Y/C matrix data Pc is read from the memory  36 , and a spectral image is formed by λ1, λ2 and λ3 signals of three wavelength ranges or of one wavelength range selected by the matrix data Pc and Y/C signals. In such a manner, in the embodiment 2, any of the scopes  10 A to  10 C, different in output mode can be used by connecting to a single processor unit  42 . 
   The endoscope apparatus according to Embodiment 2 may be constituted so that the identification information on signal output mode of the scopes  10 A,  10 B and  10 C is recognized by analyzing image signals obtained by the CCD  15  through  15 C or judging identification forming components, etc., arranged in the connector connection part in connection not by communications with microcomputers. 
   Further, in the endoscope apparatus, there is a case where both Y/C signals and RGB signals are formed by a single processor unit depending on the constitution of signal processing circuits such as DSP inside the processor unit. In this case, the Y/C spectral image forming circuit and the RGB spectral image forming circuit are selectively used to form and display a spectral image of the either circuit by utilizing Y/C signals and RGB signals as in the case according to Embodiment 2. 
   Since the endoscope apparatus of the present invention is able to form a spectral image directly from Y/C signals, it is advantageous in that circuits can be configured simply. Further, according to the second and third aspects of the invention, a spectral image can be obtained either from Y/C signals or RGB signals, and an endoscope different in a signal outputting mode can be connected for use, thereby providing a convenient endoscope apparatus. 
   The entire disclosure of each and every foreign patent application from which the benefit of foreign priority has been claimed in the present application is incorporated herein by reference, as if fully set forth.