Abstract:
An encapsulated endoscope including: MOS imaging device having a pixel section of a plurality of pixels disposed two-dimensionally in rows and columns, each pixel with a photodiode and MOS transistor where a signal from the photodiode is amplified and outputted as a pixel signal, a sole and exclusive vertical scanning section for generating row select signals to select pixels of said pixel section by rows and to cause each pixel signal to be outputted to a plurality of vertical signal lines provided for each column, and a horizontal scanning circuit for causing selective outputting of each pixel signal outputted onto the plurality of vertical signal lines; an illumination light source section; a light source control section for controlling light emitting amount or emitting time of the illumination light source; and a drive control/signal processing unit for controlling the light source control section to illuminate an object by said illumination light source section during a predetermined time and causing the pixel signals of said MOS imaging device to be outputted thereafter.

Description:
[0001]     This application claims benefit of Japanese Patent Application No. 2005-313961 filed in Japan on Oct. 28, 2005, the contents of which are incorporated by this reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to an encapsulated endoscope.  
         [0003]     It is generally known to provide a vertical scanning circuit for electronic shutter as a means for controlling exposure amount in solid-state imaging apparatus that are used in various imaging apparatus. The construction and method of controlling exposure amount will be described below of a prior-art solid-state imaging apparatus (area sensor) disclosed in Japanese Patent Application Laid-Open Hei-5-227489.  FIG. 1  is a block diagram of an overall construction of area sensor  40  as disclosed in the above publication. The area sensor  40  includes: a pixel section  13  having a plurality of pixels two-dimensionally disposed in rows and columns; a vertical scanning circuit  15  (hereinafter referred to as read vertical scanning circuit) for selecting a row of the pixel signals of the pixel section  13  to be read and sequentially switching the selected row; a vertical scanning line  16  for connecting between the pixel section  13  and the read vertical scanning circuit  15 ; a vertical scanning circuit  42  (hereinafter referred to as electronic shutter vertical scanning circuit) for resetting charge signals accumulated at the pixels; a vertical scanning line  16 ′ for connecting between the pixel section  13  and the electronic shutter vertical scanning circuit  42 ; a vertical signal line  17  onto which the pixel signals of the rows to be read, selected at the read vertical scanning circuit  15  are outputted; a horizontal read circuit  14  for sequentially outputting the signals outputted onto the vertical signal line  17 ; and an operation control section  19  for controlling operation of the area sensor  40 .  
         [0004]     The pixel section  13  consists of a light-receiving pixel region  11  and a light-blocked pixel region  12 . The read vertical scanning circuit  15  is provided to the left of the pixel section  13  while the electronic shutter vertical scanning circuit  42  is provided to the right of the pixel section  13 .  
         [0005]      FIG. 2  is a timing chart for explaining an exposure amount control operation when light is continuously irradiated onto the area sensor  40 . Supposing that the scanning direction of the read vertical scanning circuit  15  and the electronic shutter vertical scanning circuit  42  of the area sensor  40  is from the upper portion to the lower portion of the pixel section  13 , the signals accumulated at the pixels are reset once between n-th and (n+1)-th frames as shown in the timing chart of the reset signal output and pixel region output of  FIG. 2 , and pixel signals accumulated again after the resetting are read out. The exposure time (exposure time  1 , exposure time  2 ) for thus read pixel signals is time from the resetting to the readout, i.e., the time difference between the reset timing of a-th row and the read timing of a-th row.  
         [0006]     Such exposure time then is proportional to the number of rows occurring between the row (b-th row in the illustrated example) where pixel signals are being reset by the electronic shutter scanning circuit  42  at a point in time t 1  when pixel signals (a-th row in the illustrated example) are read out by the read scanning circuit  15  and the row (a-th row) where the pixel signals are being read out by the read scanning circuit  15 . The exposure time, therefore, is controlled by changing such number of rows.  
         [0007]     In addition, of imaging apparatus for taking images of a dark part for example in the body cavity, there is a method of controlling exposure amount by controlling an emission of light source.  FIG. 3  shows an encapsulated endoscope where such exposure amount control method is used as disclosed in Japanese Patent Application Laid-Open 2005-552.  
         [0008]     As shown in  FIG. 3 , an encapsulated endoscope  2  disclosed in the above publication has an outward appearance of a capsule-type tablet form. It includes a case  3  for example of a resin formed into a capsule having a substantially oval longitudinal section. A front portion of case  3  is formed of a transparent member  3   a . At the interior of the case  3 , the encapsulated endoscope  2  has its main portion where the following members are disposed. In particular, disposed in a front portion facing the transparent member  3   a  are: a light source  6  for example of LED for illuminating an object to be taken such as a digestive organ within the body cavity; an observation optical system  8  (hereinafter referred to as objective lens) for forming an optical image of the object illuminated by the light source  6 ; and an area sensor  40  consisting for example of CCD or CMOS sensor for taking an image through the objective lens  8  and effecting predetermined photoelectric conversion processing to generate image signals. Disposed from there toward the back are: a light source drive control section  5  receiving output from the area sensor  40  for controlling light amount or light-emitting time of and driving the light source  6 ; a drive control/signal processing unit  9  having a drive control circuit and signal processing circuit of the area sensor  40 ; a communication unit  10  receiving image signals outputted from the drive control/signal processing unit  9  to transmit/output the same to a predetermined receiving/record ing apparatus (not shown) provided at the outside of the body cavity for example with using a wireless communication; and a power supply  4  consisting of power supply batteries  4   a  and  4   b.    
         [0009]     Of thus constructed encapsulated endoscope  2 , the light source drive control section  5  determines light emitting conditions (emitting light amount and/or emitting time) of the light source  6  based on the output signals of the area sensor  40  and drives the light source  6  based on the determined light emitting conditions using the drive signals from the drive control/signal processing unit  9 .  
         [0010]      FIG. 4  shows drive timing (timing of light source drive current) of the light source  6  and the drive timing (timing of pixel region output) of the area sensor  40 . In a dark part such as in the body cavity, light does not enter the area sensor  40  unless the light source  6  is caused to emit. In other words, the emitting time of the light source  6  is the exposure time of the area sensor  40 . Accordingly, the exposure amount of the area sensor  40  can be controlled by controlling the light emitting conditions of the light source  6 .  
         [0011]     In the case where MOS imaging device is mounted on an encapsulated endoscope and the exposure amount is controlled at the light source, an electronic shutter function provided at an ordinary MOS imaging device is unnecessary because the interior of the body cavity is dark. On the other hand, there is a limit on the length and/or thickness of an encapsulated endoscope, since the encapsulated endoscope is to take images at the interior of the body cavity. For this reason, size reduction of MOS imaging device is a necessity when downsizing of the encapsulated endoscope is considered.  
       SUMMARY OF THE INVENTION  
       [0012]     It is an object of the present invention to provide an encapsulated endoscope capable of further downsizing with mounting MOS imaging device having a suitable structure.  
         [0013]     In a first aspect of the invention, there is provided an encapsulated endoscope including: MOS imaging device having a pixel section of a plurality of pixels disposed two-dimensionally in rows and columns, each pixel with a photodiode and MOS transistor where a signal from the photodiode is amplified and outputted as a pixel signal, a sole and exclusive vertical scanning section for generating row select signals to select pixels of the pixel section by rows and to cause each pixel signal to be outputted to a plurality of vertical signal lines provided for each column, and a horizontal scanning circuit for causing selective outputting of each pixel signal outputted onto the plurality of vertical signal lines; an illumination light source section; a light source control section for controlling light emitting amount or emitting time of the illumination light source section; and a drive control/signal processing unit for controlling the light source control section to illuminate an object by said illumination light source section during a predetermined time and causing the pixel signals of said MOS imaging device to be outputted thereafter.  
         [0014]     In a second aspect of the invention, the pixel section in the encapsulated endoscope according to the first aspect comprises a rectangular region with its center at a position corresponding to a substantial center of the MOS imaging device as a light-receiving pixel region, and a region surrounding the light-receiving pixel region as a light-blocked pixel region.  
         [0015]     In a third aspect of the invention, the vertical scanning section in the encapsulated endoscope according to the first or second aspect has a first vertical scanning unit corresponding to odd rows of the pixel section and a second vertical scanning unit corresponding to even rows of the pixel section, the first vertical scanning unit and the second vertical scanning unit being disposed at regions opposing each other with the pixel section between them. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a block diagram schematically showing construction of a prior-art area sensor.  
         [0017]      FIG. 2  is a timing chart for explaining reset period and read period in the prior-art area sensor shown in  FIG. 1 .  
         [0018]      FIG. 3  is a block diagram schematically showing construction of the electrical circuit of a prior-art encapsulated endoscope.  
         [0019]      FIG. 4  is a timing chart for explaining light source drive period and read period of the prior-art encapsulated endoscope shown in  FIG. 3 .  
         [0020]      FIG. 5  is a block diagram schematically showing construction of the electrical circuit of an encapsulated endoscope according to a first embodiment of the invention.  
         [0021]      FIG. 6  is a top view schematically showing construction of MOS image sensor to be mounted on the encapsulated endoscope according to the first embodiment shown in  FIG. 5 .  
         [0022]      FIGS. 7A and 7B  are a block diagram schematically showing construction of the electrical circuit of an encapsulated endoscope according to a second embodiment of the invention and a schematically shown front view as seen from the object side of the encapsulated endoscope, respectively.  
         [0023]      FIG. 8  is a block diagram showing construction of MOS image sensor to be mounted on the encapsulated endoscope according to the second embodiment.  
         [0024]      FIG. 9  is a block diagram showing construction of MOS image sensor to be mounted on an encapsulated endoscope according to a third embodiment of the invention.  
         [0025]      FIG. 10  is a block diagram schematically showing the construction of pixel section and vertical scanning section of MOS image sensor in the encapsulated endoscope according to the first embodiment shown in  FIG. 6 .  
         [0026]      FIG. 11  is a block diagram schematically showing construction of the pixel section, first vertical scanning unit, and second vertical scanning unit of MOS image sensor in the encapsulated endoscope according to the third embodiment shown in  FIG. 9 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
       [0027]     A description will be given below of some embodiments with reference to the drawings. A first embodiment of the encapsulated endoscope according to the present invention will now be described.  FIG. 5  is a block diagram schematically showing construction of the electrical circuit of an encapsulated endoscope  2  according to the first embodiment, where like or corresponding components as in the prior-art encapsulated endoscope  2  shown in  FIG. 3  are denoted by like reference numerals. The construction and drive operation of the encapsulated endoscope according to the first embodiment shown in  FIG. 5  are substantially identical to the construction and drive operation of the prior-art encapsulated endoscope shown in  FIG. 3 , and MOS image sensor  1  is suitably used as the area sensor therein. Further, since exposure amount thereof is controlled at the light source side, an exposure amount control at MOS image sensor  1  is not to be effected.  
         [0028]      FIG. 6  is a block diagram schematically showing construction of MOS image sensor  1  to be mounted on the encapsulated endoscope according to the first embodiment, where like or corresponding components as in the prior-art area sensor shown in  FIG. 1  are denoted by like reference numerals. The MOS image sensor  1  includes: a pixel section  13  having a plurality of pixels two-dimensionally disposed in rows and columns, each pixel containing a photodiode for effecting photoelectric conversion and an amplifying MOS transistor where the optically produced charge generated at the photodiode is changed to voltage and amplified to be outputted; a read vertical scanning section  15  for selecting rows to be read out of the pixel signals of the pixel section  13  and sequentially switching the rows to be selected; a vertical scanning line  16  connecting between the pixel section  13  and the read vertical scanning section  15 ; a vertical signal line  17  to which the pixel signals of the read rows, selected at the read vertical scanning section  15  are outputted; a horizontal read circuit  14  for sequentially outputting the signals outputted onto the vertical signal line  17 ; and an operation control section  19  for controlling operation of MOS image sensor  1 . The pixel section  13  consists of a light-receiving pixel region  11  and a light-blocked pixel region  12 , and the vertical scanning section  15  is provided to the left of the pixel section  13 .  
         [0029]     Since exposure amount of the encapsulated endoscope  2  according to the first embodiment shown in  FIG. 5  is controlled at the light source side, MOS image sensor  1  is not required to mount a vertical scanning circuit for electronic shutter which is to provide an exposure amount control function. Accordingly, due to the fact that a vertical scanning circuit for electronic shutter is not mounted, the sensor area can be made smaller as compared to the prior-art MOS image sensor so that size of the interior of the encapsulated endoscope can be reduced.  
       Second Embodiment  
       [0030]     A second embodiment of the invention will now be described.  FIG. 7A  is a block diagram schematically showing construction of the electrical circuit of an encapsulated endoscope  2  according to the second embodiment, where like or corresponding components as in the encapsulated endoscope according to the first embodiment shown in  FIG. 5  are denoted by like reference numerals. The construction and drive operation of the encapsulated endoscope according to the second embodiment is identical to the construction and drive operation of the encapsulated endoscope according to the first embodiment shown in  FIG. 5 .  FIG. 7B  shows a front view as seen from the object side of the encapsulated endoscope  2  according to the second embodiment shown in  FIG. 7A , where the center of MOS image sensor  1  is denoted by numeral  31 , the center of the light-receiving pixel region  11  of the pixel section  13  by  32 , the central axis of the encapsulated endoscope  2  by  20 , and the center of the objective lens  8  by  28 . It should be noted that  FIG. 7B  is a schematic representation of MOS image sensor  1 .  
         [0031]     As can be seen form  FIG. 7B , a substantial coincidence in disposition is achieved of the central axis  20  of the encapsulated endoscope  2 , center  31  of MOS image sensor, center  32  of the light-receiving pixel region of the pixel section  13 , and center  28  of the objective lens  8 .  
         [0032]      FIG. 8  is a block diagram showing construction of MOS image sensor  1  to be mounted on the encapsulated endoscope according to the second embodiment. Although the fundamental construction of MOS image sensor according to the second embodiment is identical to the MOS image sensor  1  according to the first embodiment shown in  FIG. 6 , there is a difference in that a light-blocked pixel region  12   a  on the side opposite to the side on which the vertical scanning section  15  of the pixel section  13  is located is made wider as compared to a light-blocked pixel region  12   b  on the vertical scanning section  15  side, thereby a substantial coincidence is achieved of the center  31  of MOS image sensor  1  and the center  32  of the light-receiving pixel region  11 .  
         [0033]     The shape of the objective lens  8  in the encapsulated endoscope is a factor in determining the shape of the encapsulated endoscope  2 . To reduce the size of the encapsulated endoscope  2 , it is desirable that the objective lens  8  be disposed within the capsule case  3  as shown in  FIG. 7B  so that the center  28  of the objective lens  8  and the central axis  20  of the encapsulated endoscope  2  substantially coincide. For this reason, MOS image sensor  1  as shown in  FIG. 8  is disposed in the encapsulated endoscope  2  so that the center  31  thereof and the central axis  20  of the encapsulated endoscope  2  substantially coincide, so as to result the construction of the encapsulated endoscope where a substantial coincidence is achieved of the center  31  of MOS image sensor  1 , the center  32  of light-receiving pixel region  11 , the central axis  20  of the encapsulated endoscope  2 , and the center  28  of the objective lens  8 . It is thereby possible to effectively use the space at the interior of the encapsulated endoscope, and a further downsizing of the encapsulated endoscope is feasible.  
         [0034]     Also from the viewpoint of packaging, since the center  31  of MOS image sensor  1  and the center  32  of light-receiving pixel region  11  substantially coincide, an extra space is not required in the positioning of MOS image sensor  1  with respect to the observation optical system. A further downsizing of the encapsulated endoscope is thereby possible.  
       Third Embodiment  
       [0035]     A third embodiment of the invention will now be described.  FIG. 9  is a block diagram showing construction of MOS image sensor  1  to be mounted on an encapsulated endoscope  2  according to the third embodiment. The MOS image sensor  1  according to the third embodiment includes: a pixel section  13  having a plurality of pixels two-dimensionally disposed in rows and columns: a first vertical scanning unit  23  for selecting odd rows to be read of the pixel signals of the pixel section  13  and for sequentially switching the row to be selected; a first vertical scanning line  24  for connecting between the pixel section  13  and the first vertical scanning unit  23 ; a second vertical scanning unit  22  for selecting even rows to be read of the pixel signals of the pixel section  13  and for sequentially switching the row to be selected; a second vertical scanning line  21  for connecting between the pixel section  13  and the second vertical scanning unit  22 ; a vertical signal line  17  onto which the pixel signals of the row to be read, selected at the first vertical scanning unit  23  and the second vertical scanning unit  22  are outputted; a horizontal read circuit  14  for sequentially outputting the signals outputted onto the vertical signal line  17 ; and an operation control unit  19  for controlling operation of MOS image sensor  1 .  
         [0036]     The pixel section  13  consists of a light-receiving pixel region  11  and a light-blocked pixel region  12 . The first vertical scanning unit  23  is provided to the left side of the pixel section  13  while the second vertical scanning unit  22  is provided to the right side of the pixel section  13 . Since exposure amount is controlled at the light source side, a vertical scanning circuit for electronic shutter is not mounted. Further, it is constructed so as to achieve coincidence of the center  31  of MOS image sensor  1  and the center  32  of light-receiving pixel region  11 . It should be noted that the first and second vertical scanning units  22 ,  23  constitute a vertical scanning section.  
         [0037]     In order to explain construction of the first and second vertical scanning units of MOS image sensor and mode of connection between the pixel section and the first and second vertical scanning units of the third embodiment, a description will be first given by way of  FIG. 10  of construction of the vertical scanning section  15  of MOS image sensor  1  and connecting mode of the vertical scanning line  16  for connecting between the pixel section  13  and the vertical scanning section  15  in the first embodiment shown in  FIG. 6 . In the connecting mode of the first embodiment shown in  FIG. 10 , a scanning stage part of the vertical scanning section corresponding to one row of the vertical scanning section  15  conforms to one row of the pixel section  13 , where a light-receiving region corresponding to one row of the pixel section  13  is denoted by numeral  26 , and a scanning stage part of the vertical scanning section corresponding to one row is denoted by numeral  25 .  
         [0038]     Of MOS image sensor  1  in the third embodiment shown in  FIG. 9 ,  FIG. 11  shows construction of the pixel section  13  and the first vertical scanning unit  23 , the connecting mode of the first vertical scanning line  24  for connecting between the pixel section  13  and the first vertical scanning unit  23 , construction of the second vertical scanning unit  22 , and the connecting mode of the second vertical scanning line  21  for connecting between the pixel section  13  and the second vertical scanning unit  22 . In the third embodiment shown in  FIG. 11 , a scanning stage part of one row of the first vertical scanning unit  23  corresponds to one row of the odd rows of the pixel section  13 , and a scanning stage part of one row of the second vertical scanning unit  22  corresponds to one row of the even rows of the pixel section  13 . A light-receiving region corresponding to one row of the odd rows of the pixel section  13  is denoted by numeral  26 , and a scanning stage part of the first vertical scanning unit  23  corresponding to one row of the odd rows by  27 .  
         [0039]     Of the MOS image sensor according to the third embodiment as shown in  FIGS. 9 and 11 , the first vertical scanning unit  23  for selecting odd rows and the second vertical scanning unit  22  for selecting even rows are disposed to the left side and to the right side, respectively, of the pixel section  13 . An extent of width corresponding to two rows of the pixel section  13  can be secured as the vertical length of each scanning stage part of the first and second vertical scanning units  22 ,  23  that is necessary for scanning of one row of the pixel section  13 .  
         [0040]     For this reason, as shown in  FIG. 11 , the horizontal length of the first vertical scanning unit  23  and the second vertical scanning unit  22  in MOS image sensor according to the third embodiment can be made shorter as compared to the vertical scanning section  15  in MOS image sensor according to the first embodiment shown in  FIG. 10 .  
         [0041]     By suitably disposing the circuits, then, the horizontal length of the vertical scanning section  15  of MOS image sensor according to the first embodiment and the horizontal length combining the first vertical scanning unit  23  and the second vertical scanning unit  22  of MOS image sensor according to the third embodiment can be made substantially the same so that an area increase of MOS image sensor  1  may be reduced to a minimum.  
         [0042]     By disposing MOS image sensor  1  according to the third embodiment having such construction into the encapsulated endoscope  2  according to the second embodiment  2  shown in  FIG. 7A  so that the center  31  of MOS image sensor  1  and the central axis  20  of the encapsulated endoscope  2  substantially coincide, the encapsulated endoscope  2  is obtained as having construction where a substantial coincidence is achieved of the center  31  of MOS image sensor  1 , the center  32  of the light-receiving pixel region  11 , the central axis  20  of the encapsulated endoscope  2 , and the center  28  of the objective lens  8 . An effective use of the space at the interior of the encapsulated endoscope is thereby possible, and a further downsizing of the encapsulated endoscope  2  is feasible.  
         [0043]     In the encapsulated endoscope according to the third embodiment, since the center  31  of MOS image sensor  1  and the center  32  of the light-receiving pixel region  11  coincide, the positioning of MOS image sensor  1  with respect to an observation optical system at the time of packaging can be effected without requiring an extra space. For this reason, a further downsizing of the encapsulated endoscope  2  is possible. Further, the degree of freedom is increased of the disposition of the light-receiving pixel region  11  and the light-blocked pixel region  12  in the case where coincidence is achieved of the center  31  of MOS image sensor  1  and the center  32  of the light-receiving pixel region  11 .  
         [0044]     As has been described by way of the above embodiments, in accordance with the first aspect of the invention, the exposure amount control of MOS imaging device is effected by a light-source control section, and by a sole vertical scanning section, row select signals having one-to-one correspondence to each row of the pixel section are generated without providing a vertical scanning section for electronic shutter which has conventionally been disposed as a separate vertical scanning circuit for example at a position opposite to a vertical scanning section with the pixel section between them. A downsizing of the encapsulated endoscope is possible by using MOS imaging device having the sole vertical scanning section where thus generated row select signals are the signals for designating the rows to be read out of the pixel signals.  
         [0045]     In accordance with the second aspect of the invention, since the center of the light-receiving pixel region of the pixel section and the center of MOS imaging device substantially coincide, the positioning of MOS imaging device with respect to the encapsulated endoscope can be effected without requiring an extra space, whereby a further downsizing of the encapsulated endoscope is possible. In accordance with the third aspect of the invention, since it is readily possible to achieve coincidence of the center of the light-receiving pixel region and the center of MOS imaging device, the positioning of MOS imaging device with respect to the encapsulated endoscope is easy without requiring an extra space, whereby a further downsizing of the encapsulated endoscope is possible.