Abstract:
An endoscope processor comprising a signal receiver, an average calculator, a difference calculator, an emphasizer, a synthesizer, and an output block is provided. The signal receiver receives an image signal generated by an imaging device. The image signal comprises a plurality of pixel signals. The average calculator calculates a signal average value. The difference calculator calculates a signal difference value. The emphasizer calculates an emphasized value by multiplying the signal difference value by a predetermined gain. The synthesizer generates an emphasized image signal, in which the pixel signal for each pixel is replaced with the sum of the emphasized value for each pixel and the signal average value.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to image signal processing that enables a user to discriminate a desired object from an entire image captured with an electronic endoscope. 
         [0003]    2. Description of the Related Art 
         [0004]    An electronic endoscope, having an imaging device at the end of an insertion tube, is used for medical examinations, industrial examinations, and so on. Light is irradiated from the end of the insertion tube to illuminate an object for observation. An optical image formed by the reflected light is captured by the imaging device, and the captured image is displayed on a monitor. 
         [0005]    A medical endoscope is used for identifying abnormal tissue or a lesion of internal organs. The appearance of abnormal tissue or a lesion is different from that of healthy tissue. Based on the user&#39;s observation, the abnormal tissue or lesion can be identified. 
         [0006]    However, the outer appearance of a lesion that exists deep under the surface of an organ is not clearly defined from that of healthy tissue. Therefore, it is often difficult to distinguish such a lesion. 
       SUMMARY OF THE INVENTION 
       [0007]    Therefore, an object of the present invention is to provide an endoscope processor that carries out signal processing on the image signal generated by an electronic endoscope in order that a lesion is easily distinguishable from a displayed image which corresponds to the image signal. 
         [0008]    According to the present invention, an endoscope processor comprising a signal receiver, an average calculator, a difference calculator, an emphasizer, synthesizer, and an output block is provided. The signal receiver receives an image signal. The image signal is generated based on an optical image captured at a light receiving surface on an imaging device. The image signal comprises a plurality of pixel signals. The pixel signals are generated by a plurality of pixels according to the amounts of received light. The plurality of the pixels are arranged on the light receiving surface on the imaging device. The average calculator calculates the signal average value. The signal average value is the average of the signal levels of the pixel signals that one frame of one field of the image signal comprises. The difference calculator calculates a signal difference value. The signal difference value is the difference between the signal level of the pixel signal for the each pixel and the signal level of the signal average value. The emphasizer calculates an emphasized value by multiplying the signal difference value by a predetermined gain. The synthesizer generates an emphasized image signal. In the emphasized image signal, the pixel signal for each pixel is replaced with the sum of the emphasized value for each pixel and the signal average value. The output block outputs the emphasized image signal. 
         [0009]    Further, the average calculator calculates the signal average value using the pixel signals, which are filtered according to their signal level, by a higher or lower limit, or both. 
         [0010]    Further, each of the pixels is covered with a first or second color filter. First and second pixels are covered with the first and second color filter, respectively. The first and second pixels generate first and second pixel signals, respectively. The average calculator calculates first and second signal average values. The first and second signal average values are the signal average values corresponding to the first and second pixel signals, respectively. The difference calculator calculates first and second signal difference values. The first and second signal values are the signal difference values corresponding to the first and second pixel signals, respectively. The emphasizer calculates first and second emphasized values. The first and second emphasized values are emphasized values corresponding to the first and second pixel signals, respectively. The synthesizer generates the emphasized image signal. In the emphasized image signal, the first and second pixel signals are replaced with the sum of the first and second emphasized values for each pixel and the first and second signal average values, respectively. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The objects and advantages of the present invention will be better understood from the following description, with reference to the accompanying drawings in which: 
           [0012]      FIG. 1  is a block diagram showing the internal structure of an endoscope system having an endoscope processor as an embodiment of the present invention; 
           [0013]      FIG. 2  is a block diagram showing the internal structure of the image signal processing block; and 
           [0014]      FIG. 3  is a flowchart describing the emphasizing image process, as carried out by the image signal processing block. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    The present invention is described below with reference to the embodiments shown in the drawings. 
         [0016]    In  FIG. 1 , an endoscope system  10  comprises an endoscope processor  20 , an electronic endoscope  40 , and a monitor  50 . The endoscope processor  20  is connected to the electronic endoscope  40  and the monitor  50  via connectors (not depicted). 
         [0017]    The whole structure of the endoscope system  10  is briefly explained. A light source  21  for illuminating an object (not depicted) is housed in the endoscope processor  20 . The light emitted from the light source  21  is irradiated onto an object (not depicted) via a light guide  41  housed in the electronic endoscope  40 . 
         [0018]    An imaging device  42 , such as a CCD image sensor, is mounted in the electronic endoscope  40 . The image of an object which is irradiated by the illumination light is captured by the imaging device  42 . Subsequently, an image signal corresponding to the image of the captured object is generated by the imaging device  42 . The image signal is sent to the endoscope processor  20 , where predetermined signal processing is carried out on the image signal. The image signal, having undergone the predetermined signal processing, is converted into a composite video signal and sent to the monitor  50 , where the resulting image is displayed. 
         [0019]    Next, each component of the endoscope system  10  is explained in detail, as follows: A diaphragm  22  and a condenser lens  23  are mounted in the optical path from the light source  21  to the incident end  41   a  of the light guide  41 . The light, which is composed almost entirely of parallel light beams emitted by the light source  21 , is made incident on, and condensed onto the incident end  41   a  by the condenser lens  23 . 
         [0020]    The intensity of the light, made incident on the incident end  41   a , is controlled by adjusting the diaphragm  22 . The diaphragm  22  is adjusted by a motor  25 . The movement of the motor  25  is controlled by the diaphragm circuit  24 . The diaphragm circuit  24  is connected to an image signal processing block  30  via a system controller  26 . The image signal processing block  30  detects the magnitude of light received in a captured image of an object based on the image signal generated by the imaging device  42 . The diaphragm circuit  24  calculates the necessary degree of adjustment for the motor  25  based on the magnitude of light received. 
         [0021]    A power circuit  27 , which supplies power to the light source  21 , is electrically connected to the system controller  26 . A control signal for switching the light source  21  on and off is output from the system controller  26  to the power circuit  27 . Consequently, the lighting status (on and off) of the light source  21  is controlled by the system controller  26 . 
         [0022]    Further, the system controller  26  outputs a driving signal necessary for driving the imaging device  42 , to an imaging device driving circuit  28 . The imaging device  42 , which is driven by the imaging device driving circuit  28 , generates an image signal corresponding to the captured image of an object. 
         [0023]    Further, the system controller  26  controls the activity of the whole endoscope processor  20 . An image signal processing block  30  is also controlled by the system controller  26 , as described later. 
         [0024]    The light made incident on the incident end  41   a  is transmitted to the exit end  41   b  via the light guide  41 . The transmitted light illuminates a peripheral area around the head end of the insertion tube of the electronic endoscope  40  after passing through a diffuser lens  43 . An optical image of the illuminated object is focused onto the light receiving surface of the imaging device  42  by an object lens  44 . 
         [0025]    A plurality of pixels (not depicted) is arranged in two dimensions on the light receiving surface of the imaging device  42 . Each pixel is covered with red, green, or blue color filter. Only red, green, or blue light components are able to pass through the red, green, and blue color filters, respectively. A light component produced by one of the color filters is made incident on the pixel that is covered by that color filter. Each pixel generates a pixel signal in accordance with the magnitude of the detected light component. 
         [0026]    The image signal of one frame or one field captured by the imaging device  42  comprises a plurality of pixel signals generated by the plurality of the pixels on the light receiving surface. 
         [0027]    The image signal generated by the imaging device  42  is sent to the image signal processing block  30  housed in the endoscope processor  20 . The image signal processing block  30  carries out normal image processing or emphasizing image processing on the image signal so that a normal image or an emphasized image is displayed on the monitor  50 , respectively. The normal image is the same as that of the captured image. The emphasized image is a partially-emphasized image of the normal image. 
         [0028]    As shown in  FIG. 2 , the image signal processing block  30  comprises a first signal processing block  31 , an extraction block  32 , an average calculation block  33 , a difference calculation block  34 , an emphasizing block  35 , a synthesizing block  36 , and a second signal processing block  37 . 
         [0029]    When the emphasizing image processing is carried out, the first signal processing block  31 , the extraction block  32 , the average calculation block  33 , the difference calculation block  34 , the emphasizing block  35 , the synthesizing block  36 , and the second signal processing block  37  function, as described later. On the other hand, when the normal image processing is carried out, only the first and second signal processing blocks  31 ,  37  function. 
         [0030]    The image signal generated by the imaging device  42  is sent to the first signal processing block  31 . The first signal processing block  31  carries out predetermined signal processing, which includes color separation processing and color interpolation processing. 
         [0031]    In the color separation processing, the image signal is separated into red, green, and blue signal components, which are pixel signals categorized in accordance with their specific magnitude of red, green, and blue light components, respectively. At this point, each pixel signal consists of only one of red, green, or blue color signal component because each pixel can directly generate only one color signal component corresponding to its covering color filter. 
         [0032]    During the color interpolation processing, in addition to the generated color signal component, two additional color signal components inherent within each pixel signal prior to the color interpolation processing, are synthesized. For example, in a pixel signal generated by a pixel covered with a green color filter and consisting of a green color signal component, the red and blue color signal components corresponding to the pixel are synthesized. Each pixel signal then consists of all three color signal components. 
         [0033]    Further, the image signal, which is an analog signal, is converted to image data, which is digital data. 
         [0034]    When normal image processing is carried out, the image data is sent from the first signal processing block  31  to the second signal processing block  37 . When emphasizing image processing is carried out, the image data is sent from the first signal processing block  31  to the extraction block  32  and the difference calculation block  34 . 
         [0035]    The extraction block  32  determines whether the data levels of red, green, and blue data components for each pixel for an entire image are within the predetermined range or not. The red, green, and blue data components are digital data converted from the red, green, and blue signal components, respectively. The data level of each color data component corresponds to the signal level of each color signal component. 
         [0036]    Higher and lower limits of a predetermined range for the red data component, hereinafter referred to as HLr and LLr, respectively, are predetermined and memorized in a ROM (not depicted). Similarly, higher and lower limits of a predetermined range for the green data component, hereinafter referred to as HLg and LLg, respectively, are predetermined and memorized in the ROM. Similarly, higher and lower limits of a predetermined range for the blue data component, hereinafter referred to as HLb and LLb, respectively, are predetermined and memorized in the ROM. The extraction block  32  reads the HLr, LLr, HLg, LLg, HLb, and LLb from the ROM. 
         [0037]    The extraction block  32  extracts a red data component whose data level is in the range between HLr and LLr. The extracted red data component is sent to the average calculation block  33 . Similarly, the extraction block  32  extracts a green data component whose data level is in the range between HLg and LLg. The extracted green data component is sent to the average calculation block  33 . Similarly, the extraction block  32  extracts a blue data component whose data level is in the range between HLb and LLb. The extracted blue data component is sent to the average calculation block  33 . 
         [0038]    The average calculation block  33  calculates the average value of a plurality of the received red data components within one field or frame of image data, hereinafter referred to as the red average value. Similarly, the average calculation block  33  calculates the average value of a plurality of the received green data components within one field or frame of image data, hereinafter referred to as the green average value. Similarly, the average calculation block  33  calculates the average value of a plurality of the received blue data components within one field or frame of image data, hereinafter referred to as the blue average value. The data of red, green, and blue average value is sent to the difference calculation block  34  and the synthesizing block  36 . 
         [0039]    The difference calculation block  34  also receives the image data, as described above. The difference calculation block  34  calculates a red difference value for each pixel by subtracting the received red average value from each of all the data level of the red data components included in one frame or one field of the image data corresponding to that red average value. Similarly, the difference calculation block  34  calculates a green difference value for each pixel by subtracting the received green average value from each of all the data level of the green data components included in one frame or one field of the image data corresponding to that green average value. Similarly, the difference calculation block  34  calculates a blue difference value for each pixel by subtracting the received blue average value from each of all the data level of the blue data components included in one frame or one field of the image data corresponding to that blue average value. 
         [0040]    The data of the red, green, and blue difference values is sent to the emphasizing block  35 . The emphasizing block  35  calculates red, green, and blue emphasized values for each pixel by multiplying the red, green, and blue difference values by a predetermined gain of more than one. 
         [0041]    The data of the red, green, and blue emphasized value is sent to the synthesizing block  36 . In addition, the data of the red, green, and blue average values is also sent to the synthesizing block  36 , as described above. 
         [0042]    The synthesizing block  36  generates emphasized image data that corresponds to the emphasized image. The emphasized image data is generated based on the red, green, and blue emphasized values and the red, green, and blue average values. How the synthesized image data is generated is explained in detail below. 
         [0043]    The synthesizing block  36  calculates the sum of the red average value and the red emphasized value for each pixel. The sum of the red average value and the red emphasized value is designated as the magnitude of the red light component in the emphasized image for each pixel. Similarly, the synthesizing block  36  calculates the sum of the green average value and the green emphasized value for each pixel. The sum of the green average value and the green emphasized value is designated as the magnitude of the green light component in the emphasized image for each pixel. Similarly, the synthesizing block  36  calculates the sum of the blue average value and the blue emphasized value for each pixel. The sum of the blue average value and the blue emphasized value is designated as the magnitude of the blue light component in the emphasized image for each pixel. 
         [0044]    The emphasized image data is then sent to the second signal processing block  37 . The second signal processing block  37  carries out predetermined signal processing, such as contrast adjustment processing and enhancement processing, on the emphasized image data. In addition, D/A conversion processing is carried out for the emphasized image data, which is subsequently converted to an analog signal. Further, a composite video signal, which includes the image signal and a synchronizing signal is generated. 
         [0045]    Incidentally, when normal image processing is carried out, the image data is sent from the first signal processing block  31  directly to the second signal processing block  37 , which carries out predetermined data processing on the received image data and generates a composite video signal corresponding to the normal image. 
         [0046]    The composite video signal is sent to the monitor  50 , where an image based on the composite video signal is displayed. 
         [0047]    The emphasizing image processing is carried out by the image signal processing block  30 , as explained below in relation to the flowchart in  FIG. 3 . The emphasizing image processing starts when a user inputs a command to start the emphasizing image processing. 
         [0048]    At step S 100 , the first signal processing block  31  receives one frame or one field of an image signal from the imaging device  42 . At step S 101 , the first signal processing block  31  carries out predetermined signal processing, which includes color separation processing and color interpolation processing. At this point red, green, and blue data components for each pixel are generated. After finishing the predetermined signal processing, the process proceeds to step S 102 . 
         [0049]    At step S 102 , the extraction block  32  determines whether or not the data levels of red, green, and blue data components, which one frame or one field of the image data includes, are within the predetermined range. The extraction block  32  extracts the red, green, and blue data components which are within the predetermined range. After the extraction, the process proceeds to step S 103 . 
         [0050]    At step S 103 , the average calculation block  33  calculates the red, green, and blue average values based on a plurality of the extracted red, green, and blue data components, respectively. After calculation of the average values, the process proceeds to step S 104 . 
         [0051]    At step S 104 , the difference calculation block  34  calculates the red, green, and blue difference values based on the average values calculated at step S 103  and the data level of red, green, and blue data components for each pixel. After calculation of the difference values, the process proceeds to step S 105 . 
         [0052]    At step S 105 , the emphasizing block  35  calculates the red, green, and blue emphasized values for each pixel by multiplying the red, green, and blue difference values by the predetermined gain. After calculation of the emphasized values, the process proceeds to step S 106 . 
         [0053]    At step S 106 , the synthesizing block  36  generates emphasized image data based on the red, green, and blue average values calculated at step S 103  and the red, green, and blue emphasized values calculated at step S 105 . For the emphasized image data, the sum of the red emphasized value for each pixel and the red average value is designated as the magnitude of the red light component for each pixel. Similarly, in the emphasized image data, the sum of the green emphasized value for each pixel and the green average value is designated as the magnitude of the green light component for each pixel. Similarly, in the emphasized image data, the sum of the blue emphasized value for each pixel and the blue average value is designated as the magnitude of the blue light component for each pixel. After generation of the emphasized image data, the process proceeds to step S 107 . 
         [0054]    At step S 107 , the second signal processing block  37  carries out predetermined signal processing including contrast adjustment processing and enhancement processing, on the emphasized image data, and generates a composite video signal. The second signal processing block  37  then sends the composite video signal to the monitor  50 , where an image corresponding to the composite video signal is displayed. 
         [0055]    At step S 108 , it is determined whether there is an input command to finish the emphasizing image processing present. If there is, the emphasizing image processing for the image signal finishes. If there is not, the process returns to step S 100 . The processes from step S 100  to step S 108  are repeated until there is an input command to finish the emphasizing image processing present. 
         [0056]    In the above embodiment, an unclear image can be converted into a clear image. Accordingly, a lesion that is not distinguishable in a normal image can be displayed more clearly, as described below. 
         [0057]    Consider an example where a mass of capillaries or an adenoma has formed under the surface of a lesion, such as a polyp. A doctor identifies such a lesion by observing the appearance of the mass of capillaries or adenoma. However, it is difficult to observe a mass of capillaries because both the surface of the internal organ and capillaries is reddish. In addition, it is difficult to identify a bulge, which is characteristic of an adenoma, because there is little change of color or brightness in the bulge. 
         [0058]    However, the endoscope processor  20  generates an emphasized image, in which a small difference of brightness and color in the normal image is emphasized by magnifying the difference between the average values of the red, green, and blue signal components and the red, green, and blue signal components for each pixel. Accordingly, a doctor is easily able to identify a lesion such as a polyp without relying on skill. 
         [0059]    In an image captured by an endoscope, the size of a lesion is generally much smaller than that of a normal organ, and the number of pixels corresponding to a lesion is much less than that of a normal organ. Consequently, in the above embodiment, the red, green, and blue average values are substantially equal to the average values of red, green, and blue data components of the pixels corresponding to a normal organ. Therefore, the average value can be regarded as a standard value of color data components corresponding to a normal organ. In the above embodiment, by generating the emphasized image data based on such average values, a lesion will be more distinguishable from a normal organ. 
         [0060]    In addition, the color of the organ can be altered by adjusting the predetermined gains for multiplying the red, green, and blue difference values. In prior art, the pigment of a specified color, such as indigo, is used as a coloring in order to enhance the edges of an entire image. However, an image where an edge is enhanced by changing the level of a color in the image can be displayed without using a pigment. 
         [0061]    In the above embodiment, the emphasized image data is generated by carrying out a calculation involving average values, difference values, and emphasized values for all of the red, green, and blue data components. However, even if the emphasized image data is generated by carrying out a calculation of their values for at least one color data component, an effect similar to the above embodiment can still be achieved. 
         [0062]    In the above embodiment, each pixel of the imaging device  42  is covered with either a red, green, or blue color filter, and the emphasized image data is generated based on the red, green, and blue data components. However, each pixel of the imaging device  42  can also be covered with another color filter and the emphasized image data can be generated based on the color data components corresponding to the color filter covering the pixel. 
         [0063]    In the above embodiment, the emphasized image data is generated based on red, green, and blue data components. However, the emphasized image data can also be generated based on other data components used to synthesize a color received at each pixel. For example, a luminance data component and a color difference data component for each pixel can be generated based on the red, green, and blue signal components for each pixel and the emphasized image data can be generated by carrying out the calculation of average values, difference values, and emphasized values on the luminance signal component and the color difference signal component. 
         [0064]    In the above embodiment, the red average value is calculated using only red data components of which the data level is within the range between HLr and LLr, and the green average value is calculated using only green data components of which the data level is within the range between HLg and LLg, and the blue average value is calculated using only blue data components of which the data level is within the range between HLb and LLb. However, it is possible that the red, green, and blue average values could be calculated using red, green, and blue data components which have been filtered according to their signal level, using a higher limit, or a lower limit, or have not been filtered at all. 
         [0065]    However, it is preferable to calculate the average value while excluding data components of which the data level is higher than an upper limit or lower than a lower limit. Generally speaking, if a pixel detects a component which is extremely dark or extremely bright, it does not corresponding to an object which needs to be observed. In addition, the average value may be too low or too high if there are many pixels which are extremely dark or extremely bright, respectively. Consequently, an emphasized image based on the average value of all the detected data components may be too dark or bright to correctly observe an object when compared to the emphasized image based on the average value of the data components within a predetermined range. 
         [0066]    The above embodiment can be implemented by installing a computer program for emphasizing an image onto an all-purpose endoscope processor. The program for emphasizing an image comprises a controller code segment for receiving, an average calculation block code segment, a difference calculation code segment, an emphasizing block code segment, a synthesizing block code segment, and a driver code segment for the output. 
         [0067]    In the above embodiment, the endoscope processor  20  carries out signal processing on the image signal generated by the electronic endoscope  40 , which comprises an insert tube to be inserted from outside. However, the endoscope processor can also carry out signal processing on an image signal generated by any other electronic endoscope, such as a capsule endoscope. 
         [0068]    Furthermore, in the above embodiment, the endoscope processor  20  receives the image signal, and carries out the above signal processing on the received image signal in real time. However, an endoscope image playback apparatus, which receives an image signal stored in internal or external memory, then carries out the above signal processing, including the emphasizing image processing, on the stored image signal while playing back the stored images. 
         [0069]    Although the embodiments of the present invention have been described herein with reference to the accompanying drawings, obviously many modifications and changes may be made by those skilled in this art without departing from the scope of the invention. 
         [0070]    The present disclosure relates to subject matter contained in Japanese Patent Application No. 2006-136541 (filed on May 16, 2006), which is expressly incorporated herein, by reference, in its entirety.