Abstract:
An electronic endoscope has a light source that radiates illuminating light, a movie-image processor, a still-image processor, an image-change processor, and provisional image displayer. The still-image processor that alternately reads odd-line image-pixel signals and even-line image-pixel signals over two field interval to generate a still image on the basis of one frame worth of image-pixel signals generated by a one-time still image exposure. The illuminating light being blocked for a latter filed interval in the two field interval. The image change processor switches between a performance of the movie-image processor for displaying the movie-image and a performance of the still-image processor for displaying the still-image. While the still-image processor reads the odd-line and even-line image-pixel signals over the two field intervals, the provisional image displayer displays a provisional image on the basis of at least one of odd-field image-pixel signals and even-field image-pixel signals, which are obtained by an exposure before the still image exposure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic endoscope having a video-scope and a video-processor, especially, it relates to a signal process for displaying an observed image while recording a still image. 
     2. Description of the Related Art 
     In an electronic endoscope, an interline-transfer (IT) CCD is used to display a movie image on a monitor, wherein odd-field image-pixel signals and even-field image-pixel signals are alternately read from the CCD for one-field reading interval. When displaying or recording a still image generated by a one-time exposure, a shading or blind member is driven so as to block light that is emitted from a lamp and directed to an object, for a one-field reading interval. Thus, odd-line image-pixel signals and even-line image pixel signals are read from the CCD in order, for one-frame (two-field) reading interval, so that a high-quality still image is obtained without a blur. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an electronic endoscope system that is capable of smoothly and continuously displaying an observed image without an interruption of an image-display while recording a still image. 
     An electronic endoscope according to the present invention has a light source that radiates illuminating light, a movie-image processor, and a still-image processor. The movie-image processor alternately reads odd-field image-pixel signals corresponding to an odd-field and even-field image-pixel signals corresponding to an even-field to generate a movie-image. For example, one field worth of image-pixel signals is temporarily stored in a memory as image data and is updated in each filed interval. The still-image processor that alternately reads odd-line image-pixel signals and even-line image-pixel signals over two field interval to generate a still image on the basis of one frame worth of image-pixel signals generated by a one-time exposure (herein, designated as “still-image exposure”). The illuminating light being blocked for a latter filed interval in the two field interval. For example, blocking member such as a chopper is applied. As for an adjustment of an exposure-time, for example, a rotary shutter that has an aperture and a shading portion are provided. The aperture and the shading portion are formed so as to alternately pass and block the illuminating light, and that rotates so as to adjust an exposure-time. 
     The electronic endoscope has further has an image change processor and a provisional image displayer. The image change processor switches a performance of the movie-image processor for displaying the movie-image and a performance of the still-image processor for displaying the still-image. For example, a switch button for displaying and/or recording a still image is provided on the video-scope. While the still-image processor reads the odd-line and even-line image-pixel signals over the two field intervals, the provisional image displayer displays a provisional image on the basis of at least one of odd-field image-pixel signals and even-field image-pixel signals, which are obtained by an exposure before the still image exposure, namely, the one-time exposure for recording a still image. 
     While the odd-line and even-line image-pixel signals are read over the two field interval, the observed image is displayed regardless of the block of the illuminating light. Therefore, a blank interval wherein the observed image is not displayed and a screen becomes black does not occur, and the operator can properly continue a work such as an operation using an electronic endoscope when recording a still image. 
     To display the provisional image by adjusting an update-timing, for example, the provisional image displayer changes an update interval of the image data from one field interval to two field intervals when the performance of the still image processor is started. Optionally, the provisional image displayer stops an update of the image data while the one frame worth of pixel-image signals, generated by the still image exposure, is read over the two field interval. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood from the description of the preferred embodiments of the invention set forth below together with the accompanying drawings, in which: 
         FIG. 1  is a block diagram of an electronic endoscope according to a first embodiment; 
         FIG. 2  is a plan view of a rotary shutter; 
         FIG. 3  is a plan view of a chopper; 
         FIG. 4  is a view showing a timing chart of a recording process; and 
         FIG. 5  is a view showing a timing chart of a recording process according to a second embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the preferred embodiments of the present invention are described with reference to the attached drawings. 
       FIG. 1  is a block diagram of an electronic endoscope according to the first embodiment. 
     The electronic endoscope has a video-scope  50  with a CCD  54 , and a video-processor  10  that has a lamp  12  and processes image-pixel signals read from the CCD  54 . The video-scope  50  is detachably connected to the video-processor  10 ; and a monitor  52  and a recorder  53  that records a still image are connected to the video-processor  10 . 
     When a lamp switch button (not shown) is turned ON, a lamp controller  11  supplies electric power to the lamp  12  so that the lamp  12  radiates illuminating light. Light emitted from the lamp  12  enters the incidence surface  51 A of a light-guide  51  via a rotary shutter  15  and a collecting lens  16 . The light-guide  51  is constructed of a fiber-optic bundle for directing the light to a tip end of the video-scope  10 . The light exits from the end portion  51 B of the light-guide  51 , and illuminates an observed object via a diffusion lens (not shown). 
     Light, reflected on the object, reaches the CCD  54  via an objective lens (not shown), so that an object image is formed on the photo-sensitive area of the CCD  54 . A color filter, checkered by four color elements of Yellow (Y), Magenta (M), Cyan (C), and Green (G), is arranged on the photo-receiving area such that the four color elements are opposite to pixels arranged in the photo-sensitive area. Based on the light passing through each color element, analog image-pixel signals are generated by the photoelectric transformation effect. The generated image-pixel signals are read from the CCD  54  at regular time intervals in accordance with clock pulse signals output from a CCD driver  54 . A timing control circuit  58  in the video-scope  50  adjusts an output-timing of the clock pulse signals. 
     The CCD  54  is an interline-transfer CCD, and as for the color imaging method using an on-chip color filter, the so called “color difference lines sequential system” is applied. Therefore, while displaying a movie image, the photo-generated charges in pixels neighboring each other are mixed, and odd-field image-pixel signals and even-field image-pixel signals are alternately read from the CCD  54 . The NTSC (or PAL) standard is herein applied as the TV standard, accordingly, the odd or even field image-pixel signals are read from the CCD  54  at a 1/60 (or 1/50) second time interval, and are then fed to an amplifier  55 . The image-pixel signals are amplified in the amplifier  55  and are subjected to given processes in a first signal processing circuit  57 . The processed image-pixel signals are fed to a second signal processing circuit  28 . 
     In the second signal processing circuit  28 , various processes, such a gamma correction process, a white balance process, and soon, are carried out on the image-pixel signals, so that digital image signals are generated and temporarily stored in an image memory  29  as digital image data. The digital image signals are read from the image memory and video signals such as NTSC signals are output to the monitor  52  at a given timing, thus an observed image is displayed on the monitor  52  as a movie image. 
     On the other hand, when displaying a still image on the monitor  52  and recording the still image in the recorder  53  by depressing a freeze button  53 A on the video-scope  50 , a one-time reading process, wherein one frame worth of image-pixel signals is generated by a one-time exposure, is performed. When electric charges are accumulated by a one-time exposure, image-pixel signals corresponding to an odd-line in the pixel-array are read from the CCD  54  over one-field reading interval, next, image-pixel signals corresponding to an even-line in the pixel array are read from the CCD  54  over one-field reading interval. One field worth of odd-line image-pixel signals and one field worth of even-line image-pixel signals are respectively fed to the amplifier  55 , the first signal processing circuit  57 , and the second signal processing circuit  28 . Then, odd-field image signals and even-field image signals are respectively output to the monitor  52 . Also, one field worth of odd-line image-pixel signals and one field worth of even-line image-pixel signals, which are processed in the second signal processing circuit  28 , are fed to the recorder  53  as still image data. 
     A system control circuit  22  including a CPU (not shown) controls each circuit in the video-processor  10 , and outputs control signals to the lamp controller  11 , the second signal processing circuit  28 , and so on. A timing control circuit, provided in the video-processor  10  (not shown), outputs clock pulse signals to each circuit in the video-processor  10  to adjust a process-timing, and outputs synchronous signals which are added to the video signals, to the second signal processing circuit  28 . The system control circuit  22  controls an output-timing of the clock pulse signals fed to each circuit. For example, the system control circuit  22  adjusts an output-timing of clock pulse signals, which are output to the image memory  28  in accordance with the operation of the freeze button  53 A to renew or rewrite image data, and adjusts an output-timing of clock pulse signals, which are output from the CCD driver  59  to drive the CCD  54 . 
     A scope controller  56 , provided in the video-scope  50 , controls the first signal processing circuit  55  and the timing control circuit  58 . The timing control circuit  58  outputs driving signals to the CCD driver  59  in accordance with the control signals output from the scope controller  56 . Thus, the reading process of the image-pixel signals is controlled. When the video-scope  50  is connected to the video-processor  10 , data are transmitted between the video-scope  50  and the video-processor  10 . 
     The rotary shutter  15  is attached to a motor (not shown), and rotates at a constant speed on the basis of driving signals fed from a motor driver  23 . A chopper  17 , which shades or blocks the light to be directed to the end portion of the video-scope  50 , is provided between the rotary shutter  15  and the collecting lens  16 , and has a DC solenoid (herein, not shown). The chopper  17  motions in accordance with a series of pulse signals fed from a PWM driving circuit  24 . 
       FIG. 2  is a plan view of the rotary shutter  15 .  FIG. 3  is a plan view of the chopper  17 . 
     The rotary shutter  15  is constructed of an aperture  15 A that passes the light from the lamp  12  and a shading portion  15 B that shades or shields the light. The aperture  15 A is formed such that a pair of arc-shaped holes is opposite to each other. The rotary shutter  15  rotates by one-rotation in one-frame reading interval (= 1/30 or 1/25 second). Therefore, the half-circle  15 P of the rotary shutter  15  corresponds to one-field reading interval (= 1/60 or 1/50 second). While the rotary shutter  15  rotates by a half-rotation, the aperture  15 A and shading portion  15 B pass the light-path of the light emitted from the lamp  12 , in turn. Thus, an exposure interval and a shading interval alternately occur in one-field reading interval, which functions like an electronic shutter. 
     When displaying and recording the still image, one frame worth of image-pixel signals is obtained by light passing through one aperture  15 A, namely, by rotating the rotary shutter  15  by a half-rotation. Then, the obtained one frame worth of image-pixel signals is read from the CCD  54  over the one-frame reading interval (= 1/30 or 1/25 second). Since the other aperture  15 A passes the light-path for the remaining interval (= 1/60 or 1/50 second), the chopper  17  moves so as to block the illuminating light when the other aperture  15 A passes the light-path. 
     In  FIG. 3 , the non-shading position of the chopper  17 , which enables light to pass through one arc-shaped hole of the aperture  15 A, is shown by a solid line, whereas the shading position of the chopper  17 , which blocks the light when the other arc-shaped hole of aperture  15 A passes the light-path, is shown by a broken line. The chopper  17  is a pivot-type solenoid, and has a DC solenoid  17 A and a plate member  17 B, which pivots around a center axis  17 C. When the chopper  17  motions so as to shade the illuminating light, an end portion  17 D of the plate member  17 B covers the light-path or the aperture  15 A of the rotary shutter  15 . The PWM driving circuit  24  is a PWM controller, which outputs a sequence of pulse signals to the solenoid  17 A. 
       FIG. 4  is a view showing a timing chart of the recording process. 
     In a state where the freeze button  53 A is not pressed, namely, a movie image is displayed, odd-field image-pixel signals and even-field image-pixel signals are alternately read from the CCD  54  at a 1/60 (or 1/50) of a second interval while mixing adjacent pixel signals, as described above. Since the CCD  54  is an interline type CCD, the photo-generated charges, which are accumulated by a given exposure-timing, are read in the next exposure-timing. For example, image-pixel signals, which are accumulated at “n−1” of the exposure-timing and correspond to the even-field, are read from the CCD  54  at “n” of the exposure-timing, as shown in  FIG. 4 . Clock pulse signals, which update the image data in the image memory  29 , are output to the image memory  29  at 1/60 (or 1/50) time interval. 
     When the freeze button  53 A is pressed to start recording a still image, all pixel signals, which are obtained during a one-time exposure time (in  FIG. 4 , the signals in the order of “n”), are read from the CCD  54  over a one-frame reading interval. Concretely, odd-line image-pixel signals and even-line image-pixel signals are read from the CCD  54 , in turn, over two field intervals. During the reading of all image-pixel signals, the chopper  17  motions to block the illuminating light. 
     Further, when the recording process is performed, the output-interval of the clock pulse signals for update is changed from one-field interval to two-field (one-frame) intervals. The two-field intervals are based on pulse signals “SP”, which are output at an exposure-time just before an exposure-time for recording the still image. Consequently, the odd-field image-pixel signals and the even-field image-pixel signals are respectively used to display the observed image over two field intervals. An observed image, formed by the odd-field image-pixel signals, is displayed for 1/30 (or 1/25) of a second, and an observed image, formed by the even-field image-pixel signals, is also displayed for 1/30 ( 1/25) of a second. After the one frame worth of image-pixel signals (odd-line image-pixel signals and even-line image-pixel signals) are read from the CCD  54 , the interval of the update returns to one field interval. 
     With reference to  FIG. 5 , the second embodiment is explained. The second embodiment is different from the first embodiment in that image data is not renewed while recording the still image. 
       FIG. 5  is a view showing a timing chart of a recording process according to the second embodiment. 
     When the recording process is started by depressing the freeze button  53 A, as shown in  FIG. 5 , clock pulse signals for update are not output to the image memory  29  over two-field intervals. Then, odd-field image-pixel signals, obtained by an exposure just before the exposure for recording the still image, are used to display the observed image until the one frame worth of image-pixel signals for the still image is read from the CCD  54 . 
     Finally, it will be understood by those skilled in the arts that the foregoing description is of preferred embodiments of the device, and that various changes and modifications may be made to the present invention without departing from the spirit and scope thereof. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No. 2005-056979 (filed on Mar. 2, 2005), which is expressly incorporated herein, by reference, in its entirety.