Patent Publication Number: US-2018045948-A1

Title: Stereo image pickup unit

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of PCT/JP2016/076432 filed on Sep. 8, 2016 and claims benefit of Japanese Application No. 2015-246015 filed in Japan on Dec. 17, 2015, the entire contents of which are incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a stereo image pickup unit that acquires two picked-up images having parallax. 
     2. Description of the Related Art 
     In recent years, in a field of medical endoscopes and industrial endoscopes, a need for stereoscopic observation of a subject with use of a stereo image pickup unit has been increasing. 
     As a configuration of a distal end portion of an endoscope using the stereo image pickup unit, for example, Japanese Patent Application Laid-Open Publication No. H8-29701 discloses a technology in which an objective lens unit is fitted into a transparent hole provided on a distal end member and a CCD unit is further fitted into the transparent hole. Two objective lens systems (objective optical systems) are integrally mounted on the objective lens unit, and two CCDs (image pickup devices) are integrally mounted on the CCD unit. For example, as disclosed in Japanese Patent Application Laid-Open Publication No. H8-29701, each of the image pickup devices is typically positioned and fixed to a holder through an individual centering glass. In other words, the centering glass corresponding to each of the image pickup devices is held by the holder, and each of the image pickup devices is positioned on the corresponding centering glass, and is then bonded to the centering glass, thereby being held. 
     SUMMARY OF THE INVENTION 
     A stereo image pickup unit according to an aspect of the present invention includes: a first image pickup device configured to receive a first optical image formed by a first objective optical system; a second image pickup device configured to receive a second optical image formed by a second objective optical system that is paired with the first objective optical system; a single optical member that is disposed on optical paths of the respective first and second optical images and to which light receiving surfaces of the respective first and second image pickup devices are positioned and fixed through bonding; and a single holding frame that includes a holding portion, a first objective optical system holding hole, and a second objective optical system holding hole. The holding portion holds the optical member, the first objective optical system holding hole holds the first objective optical system, and the second objective optical system holding hole holds the second objective optical system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating an entire configuration of an endoscope system; 
         FIG. 2  is an end surface view of a distal end portion of an endoscope; 
         FIG. 3  is a cross-sectional diagram taken along line III-III in  FIG. 2 ; 
         FIG. 4  is an enlarged cross-sectional diagram of a stereo image pickup unit; and 
         FIG. 5  is an exposed perspective view illustrating the stereo image pickup unit from proximal end side. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     An embodiment of the present invention is described below with reference to drawings. The drawings relate to the embodiment of the present invention.  FIG. 1  is a perspective view illustrating an entire configuration of an endoscope system.  FIG. 2  is an end surface view of a distal end portion of an endoscope.  FIG. 3  is a cross-sectional diagram taken along line III-III in  FIG. 2 .  FIG. 4  is an enlarged cross-sectional diagram of a stereo image pickup unit.  FIG. 5  is an exposed perspective view illustrating the stereo image pickup unit from proximal end side. 
     An endoscope system  1  illustrated in  FIG. 1  includes a stereoscopic endoscope  2 , a processor  3 , and a monitor  5 . The stereoscopic endoscope  2  stereoscopically picks up an image of a subject from different viewpoints. The stereoscopic endoscope  2  is detachably connected to the processor  3 . The monitor  5  serves as a display apparatus that displays an image signal generated by the processor  3 , as an endoscope image. 
     The stereoscopic endoscope  2  according to the present embodiment is, for example, a rigid endoscope applied to laparoscopic surgeries. The stereoscopic endoscope  2  includes an elongated insertion section  6 , an operation section  7 , and a universal cable  8 . The operation section  7  is provided continuously to proximal end side of the insertion section  6 . The universal cable  8  extends from the operation section  7  and is connected to the processor  3 . 
     The insertion section  6  mainly includes a distal end portion  11 , a bending portion  12 , and a rigid tube portion  13  that are continuously provided in order from distal end side. The distal end portion  11  is configured of a metal member made of stainless steel or the like. The rigid tube portion  13  is configured of a metal tube made of stainless steel or the like. 
     The insertion section  6  is a section to be inserted into a body. A stereo image pickup unit  30  (see  FIG. 3  and the like) that stereoscopically picks up an image inside the subject is incorporated in the distal end portion  11 . Further, image pickup cable bundles  39   l  and  39   r  (see  FIG. 3 ), a light guide bundle (not illustrated), and the like are inserted into the bending portion  12  and the rigid tube portion  13 . The image pickup cable bundles  39   l  and  39   r  are electrically connected to the stereo image pickup unit  30 . The light guide bundle transmits illumination light to the distal end portion  11 . Note that, as the stereoscopic endoscope  2  according to the present embodiment, a rigid endoscope in which the proximal end side of the bending portion  12  is configured of the rigid tube portion  13  is exemplified; however, the stereoscopic endoscope  2  is not limited to the rigid endoscope, and the stereoscopic endoscope  2  may be a flexible endoscope in which the proximal end side of the bending portion  12  is configured of a flexible tube portion having flexibility. 
     An angle lever  15  to remotely operate the bending portion  12  is provided on the operation section  7 , and various kinds of switches  16  to operate a light source apparatus of the processor  3 , a video system center, and the like are further provided on the operation section  7 . 
     The angle lever  15  is bending operation means that bendably operates the bending portion  12  of the insertion section  6  in four directions of up, down, right, and left, in this case. Note that the bending portion  12  is not limited to the configuration bendable in the four directions of up, down, right, and left, and may be configured to be bendably operated in, for example, two directions of only up and down, or only right and left. 
     Next, a configuration of the distal end portion of such a stereoscopic endoscope  2  is described in detail with reference to  FIGS. 2 and 3 . 
     As illustrated in  FIG. 3 , the distal end portion  11  includes a distal end portion body  20  having a substantially columnar shape, and a distal end cylinder  21  that has a substantially cylindrical shape and has a distal end fixed to the distal end portion body  20 . Here, the distal end of the distal end cylinder  21  is fitted to an outer periphery of the distal end portion body  20 , and a distal end surface  11   a  of the distal end portion  11  is formed of an end surface of the distal end portion body  20  exposed from the distal end cylinder  21 . 
     As illustrated in  FIGS. 2 and 3 , paired observation through holes  23   l  and  23   r  that open on the distal end surface  11   a  are provided side by side (in other words, in a lateral bending direction of the bending portion  12 ) on the distal end portion body  20 . Paired objective optical systems (first and second objective optical systems  31   l  and  31   r ) that configure the stereo image pickup unit  30  are respectively held by the left and right observation through holes  23   l  and  23   r . This forms observation windows  24   l  and  24   r  on the distal end surface  11   a  of the distal end portion  11 . 
     In addition, for example, as illustrated in  FIG. 2 , paired illumination through holes  25   l  and  25   r  that open on the distal end surface  11   a  are provided side by side on upper side of the observation through holes  23   l  and  23   r  (in other words, on upper side in a vertical bending direction of the bending portion  12 ) on the distal end portion body  20 . Paired illumination optical systems  27   l  and  27   r  that are optically connected to the unillustrated light guide bundle are respectively held by the left and right illumination through holes  25   l  and  25   r . This forms illumination windows  26   l  and  26   r  on the distal end surface  11   a  of the distal end portion  11 . 
     As illustrated in  FIG. 3  to  FIG. 5 , the stereo image pickup unit  30  includes: a first image pickup device  32   l  that receives an optical image (a first optical image) formed by the first objective optical system  31   l ; a second image pickup device  32   r  that receives an optical image (a second optical image) formed by the second objective optical system  31   r ; a single centering glass  34  that is disposed on optical paths of the respective first and second optical images, and serves as an optical member to which light receiving surfaces  32   la  and  32   ra  of the respective first and second image pickup devices  32   l  and  32   r  are aligned and fixed through bonding; and a holding frame  35  that holds the first and second image pickup devices  32   l  and  32   r  through the centering glass  34 . 
     Each of the first and second image pickup devices  32   l  and  32   r  is configured of a solid-state image pickup device such as a CCD (charge coupled device) and a CMOS (complementary metal oxide semiconductor). Cover glasses  33   l  and  33   r  to respectively protect the light receiving surfaces  32   la  and  32   ra  are respectively bonded to the first and second image pickup devices  32   l  and  32   r.    
     Further, flexible print circuit boards (FPC boards)  38   l  and  38   r  are respectively electrically connected to terminal parts (not illustrated) provided on the first and second image pickup devices  32   l  and  32   r . For example, various kinds of electronic components such as a digital IC to generate a driving signal of the image pickup device, an IC driving power-supply stabilization capacitor to stabilize a driving power supply of the digital IC, and a resistor are mounted on each of the FPC boards  38   l  and  38   r  through soldering, etc. In addition, the image pickup cable bundles  39   l  and  39   r  are respectively electrically connected to the FPC boards  38   l  and  38   r.    
     Note that, in the present embodiment, the first and second image pickup devices  32   l  and  32   r , the FPC boards  38   l  and  38   r  on which the various kinds of electronic components are mounted, and distal ends of the respective image pickup cables  39   l  and  39   r  that are respectively electrically connected to the FPC boards  38   l  and  38   r  are integrally covered with a single cover body  42 . 
     The centering glass  34  is configured of a transparent glass substrate that extends in the lateral direction of the distal end portion  11 . The light receiving surfaces  32   la  and  32   ra  of the first and second image pickup devices  32   l  and  32   r  are fixed to the centering glass  34  through the cover glasses  33   l  and  33   r , respectively. 
     More specifically, the cover glasses  33   l  and  33   r  respectively adhered to the light receiving surfaces  32   la  and  32   ra  are bonded to the centering glass  34  with an ultraviolet curable transparent adhesive (a UV adhesive) or the like. As a result, the first and second image pickup devices  32   l  and  32   r  are positioned and fixed to the centering glass  34  while being separated from each other with a predetermined interval. Further, a distal end of the cover body  42  is fixed to a glass holding portion  36 . 
     The holding frame  35  is configured of, for example, a columnar metal member that has a substantially round cornered rectangular cross-sectional surface (for example, see  FIG. 5 ). The glass holding portion  36  is recessed on the proximal end side of the holding frame  35 , and the centering glass  34  is fixed to the glass holding portion  36  with an adhesive or the like. 
     Further, for example, as illustrated in  FIGS. 3 and 4 , a first objective optical system holding hole  37   l  and a second objective optical system holding hole  37   r  are provided side by side with a preset interval in between, on the holding frame  35 . Distal ends of the respective first and second objective optical system holding holes  37   l  and  37   r  are opened on an end surface (the distal end surface  11   a ) of the holding frame  35 , and proximal ends are configured of through holes that communicate with the glass holding portion  36 . 
     The first and second objective optical systems  31   l  and  31   r  are respectively held by the first and second objective optical system holding holes  37   l  and  37   r  while being unitized as first and second objective optical system units  40   l  and  40   r.    
     In other words, the first and second objective optical systems  31   l  and  31   r  are respectively held by first and second lens frames  41   l  and  41   r , thereby respectively configuring the first and second objective optical system units  40   l  and  40   r . Further, the first and second objective optical system units  40   l  and  40   r  are respectively positioned and fixed inside the first and second objective optical system holding holes  37   l  and  37   r  with an adhesive or the like, which causes the first and second objective optical systems  31   l  and  31   r  and the first and second image pickup devices  32   l  and  32   r  to be integrally held by the single holding frame  35 . 
     In this case, to correct a slight machining error, a slight assembly error, and the like of each portion to optimize relative positions (such as a distance between optical axes and tilt angles) of the first and second objective optical systems  31   l  and  31   r , one of the first and second objective optical system holding holes  37   l  and  37   r  (for example, the first objective optical system holding hole  37   l ) is configured of a through hole larger in diameter than the other hole (for example, the second objective optical system holding hole  37   r ). In other words, for example, as illustrated in  FIG. 4 , in the present embodiment, the first objective optical system holding hole  37   l  is configured of a through hole having an inner diameter that is obtained by adding a predetermined adjustment margin Δr to an inner diameter r that receives the first lens frame  41   l  substantially without a gap. On the other hand, the second objective optical system holding hole  37   r  is configured of a through hole having the inner diameter r that receives the second lens frame  41   r  substantially without a gap. Further, the first objective optical system unit  40   l  is bonded and fixed inside the first objective optical system holding hole  37   l  while the distance between the optical axes, the tilt angle, and the like are slightly adjusted with respect to the second objective optical system unit  40   r.    
     Next, an example of a method of assembling the stereo image pickup unit  30  having such a configuration is described. 
     In the method of assembling the stereo image pickup unit  30 , first, the first and second image pickup devices  32   l  and  32   r  are positioned and fixed to the centering glass  34  through the UV adhesive. 
     In this case, the relative positions of the first and second image pickup devices  32   l  and  32   r  on the centering glass  34  are accurately positioned (centered) through, for example, observation of photoelectric conversion devices and the like disposed on the light receiving surfaces  32   la  and  32   ra  of the respective first and second image pickup devices  32   l  and  32   r  through the centering glass  34  under a microscope. Thereafter, in the positioned state in the above-described manner, ultraviolet rays are applied to cure the UV adhesive, which fixes the first and second image pickup devices  32   l  and  32   r  (more specifically, the cover glasses  33   l  and  33   r ) to the centering glass  34 . 
     In a next step, the centering glass  34  holding the first and second image pickup devices  32   l  and  32   r  is fixed to the glass holding portion  36  provided on the holding frame  35 , with an adhesive or the like. At this time, the centering glass  34  is adjusted such that, for example, the second image pickup device  32   r  is positioned at a predetermined position with respect to the second objective optical system holding hole  37   r  that does not include the adjustment margin Δr. 
     In a next step, the second objective optical system unit  40   r  is positioned and fixed inside the second objective optical system holding hole  37   r . In other words, the second objective optical system unit  40   r  inserted into the second objective optical system holding hole  37   r  is adjusted in the optical axis direction (is focused) under observation of the second optical image formed on the second image pickup device  32   r , and is then fixed with an adhesive or the like. 
     In next step, the first objective optical system unit  40   l  is positioned and fixed inside the first objective optical system holding hole  37   l . In other words, the first objective optical system unit  40   l  inserted into the first objective optical system holding hole  37   l  is adjusted in the optical axis direction (is focused) under observation of the first optical image formed on the first image pickup device  32   l . Further, the first objective optical system unit  40   l  is adjusted in relative position (such as the distance between the optical axes and the tilt angle) with respect to the second objective optical system unit  40   r  within a range of the adjustment margin set in the first objective optical system holding hole  37   l , based on comparison between the first optical image formed on the first image pickup device  32   l  and the second optical image formed on the second image pickup device  32   r . The first objective optical system unit  40   l  is then fixed with the adhesive or the like. 
     According to such an embodiment, the respective light receiving surfaces  32   la  and  32   ra  of the first image pickup device  32   l  that receives the first optical image formed by the first objective optical system  31   l  and the second image pickup device  32   r  that receives the second optical image formed by the second objective optical system  31   r , are positioned and fixed, with an adhesive or the like, to the single centering glass  34  that is disposed on the optical paths of the respective first and second optical images. The first and second image pickup devices  32   l  and  32   r  are held by the holding frame  35  through the centering glass  34 . As a result, it is possible to acquire two picked-up images with appropriate parallax through a simple configuration. 
     In other words, the first and second image pickup devices  32   l  and  32   r  are positioned and fixed to the single centering glass  34  and are held by the holding frame  35 , which makes it possible to reduce the number of components to simplify the configuration, as compared with a case where the first and second image pickup devices are positioned and fixed to the holding frame through individual centering glasses. Further, the relative positions of the first and second image pickup devices  32   l  and  32   r  are determined on the single centering glass  34  that is smaller in thermal expansion and thermal contraction than the metal holding frame  35 , which makes it possible to accurately position the first and second image pickup devices  32   l  and  32   r  at appropriate parallax positions. Therefore, it is possible to acquire two picked-up images with appropriate parallax. In addition, in the configuration in which the first and second image pickup devices  32   l  and  32   r  are fixed to the single centering glass  34 , it is possible to prevent the distance between the optical axes of the first and second image pickup devices  32   l  and  32   r  from becoming excessively large, and to prevent three-dimensional appearance in stereoscopic observation from becoming excessively high, as compared with a configuration in which the first and second image pickup devices  32   l  and  32   r  are fixed to individual centering glasses. 
     In this case, the first objective optical system holding hole  37   l  that holds the first objective optical system  31   l  and the second objective optical system holding hole  37   r  that holds the second objective optical system  31   r  are provided on the holding frame  35 , which allows the single holding frame  35  to hold not only the first and second image pickup devices  32   l  and  32   r  but also the first and second objective optical systems  31   l  and  31   r . This makes it possible to achieve further simplification of the configuration. In addition, providing the first and second objective optical system holding holes  37   l  and  37   r  on the single holding frame  35  makes it possible to prevent the distance between the optical axes from becoming excessively large. 
     Moreover, the first and second objective optical systems  31   l  and  31   r  are assembled to the holding frame  35  while being respectively held by the first and second lens frames  41   l  and  41   r  with high accuracy and respectively unitized as the first and second objective optical system units  40   l  and  40   r . This makes it possible to improve attachment accuracy of the first and second objective optical systems  31   l  and  31   r  with respect to the holding frame  35 . 
     Further, providing the adjustment margin in one of the first and second objective optical system holding holes  37   l  and  37   r  makes it possible to easily achieves relative positional adjustment of the first and second objective optical systems  31   l  and  31   r , even when the first and second objective optical system holding holes  37   l  and  37   r  are provided on the single holding frame  35 . 
     Note that the present invention may be variously modified and alternated without limitation to the above-described embodiment, and such modifications and alternations are also included in the technical scope of the present invention.