Abstract:
An endoscope camera head includes: an image pickup device that is configured to capture an image of an optical image and output an imaging signal containing the captured image; and a lens member that includes a lens for forming the optical image on the image pickup device, wherein the image pickup device is fixed to the lens member at a position in which the center of an image circle of the lens and the center of an image pickup area of the image pickup device coincide with each other.

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
       [0001]    The present disclosure relates to the subject matters contained in Japanese Patent Application No. 2008-069723 filed on Mar. 18, 2008, which are incorporated herein by reference in its entirety. 
       FIELD 
       [0002]    The present invention relates to an endoscope camera head and a method for manufacturing the endoscope camera head. 
       BACKGROUND 
       [0003]    Endoscopes are used to observe inside a subject to be observed by inserting the endoscopes inside the subject. The known endoscopes include a medical endoscope for observing inside a body cavity and an industrial endoscope for observing inside a structure such as a pipe or a machine. Such an endoscope has a camera head (also called an insertion section) that is inserted into the body cavity or the structure, a camera control unit (also called an endoscope body) for processing a signal received from the camera head, and a cable that connects the camera head and the camera control unit. 
         [0004]    An example of the conventional electronic endoscope is disclosed in JP-2002-301012-A. The electronic endoscope disclosed in this publication is provided with a camera head including a cover glass that is disposed in front of a CCD (Charge Coupled Devices) and an optical lens that is disposed in front of the cover glass. 
         [0005]    In the conventional endoscope, as the electronic endoscope disclosed in the aforementioned publication, the optical lens and the CCD are fixed in its position in the camera head. 
         [0006]    However, in the conventional endoscope, positions of the optical lens and the CCD are fixed so that an image pickup area of the CCD is positioned within an image circle (a circular range in which light transmitted thorough the optical lens is imaged on the CCD) of the optical lens. 
         [0007]    In this case, as shown in  FIG. 12A , when the image pickup area AR of the CCD is deviated form the image circle C, the image formed by the optical lens might be deviated from the image pickup area AR of the CCD, whereby an image loss may be caused. Hence, in the conventional camera head, in order to assure the position of the image pickup area AR of the CCD to be within the image circle C, a margin is set by increasing a size of the image circle C, as shown in  FIG. 12B . Accordingly, in the conventional camera head, the size of the optical lens should be set by a predetermined value, and thus it is difficult to reduce an exterior size of the camera head that houses the optical lens. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    A general configuration that implements the various feature of the invention will be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. 
           [0009]      FIG. 1  is a block diagram showing a primary configuration of a camera apparatus according to an embodiment of the invention. 
           [0010]      FIG. 2  is a sectional side view of a head casing showing a primary configuration of the inside of a camera head. 
           [0011]      FIG. 3  is a side view showing an image pickup unit. 
           [0012]      FIG. 4  is a diagram showing an example of an image pickup unit and a chart used in a CCD positioning. 
           [0013]      FIG. 5  is a diagram showing an example of relation between the image circle and the image pickup area. 
           [0014]      FIG. 6  is a diagram showing an example of a monitor and an image displayed thereon. 
           [0015]      FIG. 7  is a diagram showing an example of a front end part structure of a different camera head. 
           [0016]      FIG. 8  is a sectional side view of a head casing additionally showing a primary configuration of the inside of the different camera head. 
           [0017]      FIG. 9  is a perspective view showing a configuration of a camera head in a different camera apparatus according to the invention. 
           [0018]      FIG. 10  is a side view showing a TAB CCO. 
           [0019]      FIG. 11  is a perspective view showing a CCD and a cover glass before CCD positioning. 
           [0020]      FIGS. 12A and 12B  are diagrams showing an example of relation between an image circle and an image pickup area, wherein  FIG. 12A  is a diagram showing an example of a case where the image pickup area is deviated from the image circle, and  FIG. 12B  is a diagram showing an example of a case where the image pickup area is included in the image circle and the image circle has a margin. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0021]    Hereinafter, embodiments of the invention will be described. In the following description, the same or similar components will be referenced by the same reference numerals, and detailed description thereof will be omitted. 
         [0022]      FIG. 1  is a block diagram showing a configuration of a camera apparatus  100  according to an embodiment of the invention.  FIG. 2  is a sectional side view of a head casing showing inside of a camera head.  FIG. 3  is a side view showing an image pickup unit. 
         [0023]    As shown in  FIG. 1 , the camera apparatus  100  has a camera head  1 , a camera control unit  2  (hereinafter simply referred to as “CCU”), and a camera cable  3  that connects the camera head  1  and the camera control unit  2 . 
         [0024]    The camera head  1 , as shown in  FIG. 2 , has an image pickup unit  10 , a substrate holder  17 , a position fixing ring  13 , a circuit board  20 , a wire  23 , and a head casing  30 . The camera head  1  is configured so that the head casing  30  houses the image pickup unit  10 , the substrate holder  17 , the position fixing ring  18 , the circuit board  20 , and the wire  23 . 
         [0025]    The image pickup unit  10 , as shown in  FIG. 3 , has a lens block  11  and a CCD  13 . As described later, by CCD positioning the center of an image circle  51  is made to coincide with the center of an image pickup area  52 , and the CCD  13  is fixedly attached to the lens block  11  by an optical adhesive  12 . 
         [0026]    The lens block  11  has a lens barrel section  15  as a tubular member housing optical lenses  8  and  9  therein and a cover glass  16  having a cylindrical shape fixedly attached to one axial end portion of the lens barrel section  15 . In addition, the CCD  13  is fixedly attached by the optical adhesive  12  to a section  16   a  (see  FIG. 11 ) on a side of the cover glass  16  that is not attached to the lens barrel section  15 . 
         [0027]    The CCD  13  is an image pickup device that generates an imaging signal based on an optical image formed by the optical lenses  8  and  9  and outputs the imaging signal to the outside through the lead wire  14 . In addition, the CCD  13  is formed by a TAB CCD (a CCD of which a chip size is substantially equal to a package size thereof). 
         [0028]    The lead wire  14  is soldered to a circuit board  20 , and is provided so as to output the imaging signal generated from the CCD  13  and supply power and drive pulse from the circuit board  20  to the CCD  13 . 
         [0029]    In addition, the image pickup unit  10  is housed in the head casing  30  in a state where the position fixing is ring  18  is mounted on the lens barrel section  15 . The position fixing ring  18  is a tubular member having a size corresponding to inner circumference of the head casing  30 , and is for fixing a position thereof in the head casing  30  of the image pickup unit  10 . 
         [0030]    The substrate holder  17  is a member fixedly attached to an end of the CCD  13  of an opposite side that is not fixedly attached to the lens block  11 , and fixing a position thereof by inserting the circuit board  20  therein. On the circuit board  20 , circuit line patterns to which the imaging signal output from the CCD  13  is input are formed on each of an upper surface and a lower surface thereof, and electronic components  21  and  22  for processing the imaging signal is mounted on the line pattern. The circuit board  20  is connected to the CCD  13  through the lead wire  14 , and is connected to the cable  3  through a wire  23 . The wire  23  fixedly attached to the circuit board  20  and the cable  3  by being soldered. 
         [0031]    The head casing  30  is integrally formed by combining a front cover  31 , a barrel member  32  in which the front cover  31  is mounted on a front end portion thereof, a barrel member  33  in which the barrel member  32  is mounted on a front end portion thereof. In addition, in the head casing  30 , in order from the rear end portion of the barrel member  33 , the image pickup unit  10  in which the position fixing ring  18  is mounted on the lens barrel section  15 , the substrate holder  17 , the circuit board  20 , and the front end portion of the cable  3  connected to the wire  23  are inserted, and coking  3   a  is locked by a locking portion  33   a  of the barrel member  33 . 
         [0032]    The CCU  2  has a drive circuit  2   a  generating a drive signal for driving the CCD  13 , and a signal processing circuit  2   b  performing amplification of the imaging signal input from the camera head  1  through the camera cable  3 , D/A conversion, video signal generation for displaying an image on a display device, and the like. 
         [0033]    In the camera apparatus  100 , the camera head  1  is inserted into the inside of a subject, an optical image of the inside of the subject is imaged on the CCD  13  by optical lenses  8  and  9 , and an imaging signal based on the optical image is output from the CCD  13 . The imaging signal is processed by electronic components on the circuit board  20  through the lead wire  14 , and then is input from the wire  23  to the CCU  2  through the camera cable  3 . 
         [0034]    Furthermore, a video signal output from the CCU  2  is guided to the display device not shown in the drawings, and thus the subject taken by the camera head  1  can be observed by displaying an image on the display device. 
         [0035]    However, as described above, the image pickup unit  10  is manufactured by performing the CCD positioning that makes the center of the image circle  51  coincide with the center of the image pickup area  52 , and fixedly attaching the CCD  13  to the lens block  11  in a state where both of the centers coincide with each other. The CCD positioning is performed as follows. 
         [0036]    In the CCD positioning according to embodiment, as shown in  FIG. 4 , a chart S for adjusting the position is used. The chart S is depicted on a planar wall, in which on a rectangular area S 1  having a size capable of being captured by the image pickup unit  10 , a cross line S 2  passing through a center point S 0  thereof and a positioning circle  53  centered on the center point S 0  are depicted. 
         [0037]    When the chart S is captured by the image pickup unit  10 , the optical image of the chart S is imaged on the CCD  13  by the optical lenses  8  and  9 . Accordingly, a monitor  71  is provided as shown in  FIG. 6 , and the imaging signal of the CCD  13  is guided into the monitor  71  through the lead wire  14 , the circuit board  20 , the wire  23 , and the cable  3 . Thus, it is possible to display a chart image SA showing the chart S on a display section  72  of the monitor  71 . On the display section  72 , a cross-shaped mark P previously showing a center position of the display section  72  is depicted. 
         [0038]    When the CCD positioning is performed, first, as shown in  FIG. 4 , the front end side of the lens block  11  to which the CCD  13  is not fixedly attached is made to face toward the chart S, and then the lens barrel section  15  is held by a predetermined holding member. At this time, the CCD  13  is held together with the lens barrel section  15  so that the chart image SA is displayed on the display section  72 , and thus the position of the lens barrel section  15  is determined so that an optical axis t 0  of the optical lenses  8  and  9  points to the center point S 0  of the chart S. 
         [0039]    The image taken by the CCD  13  can be displayed on the display section  72  of the monitor  71 , and thus the CCD positioning is performed while observing the display section  72 . Then, the position of the CCD  13  is adjusted so that the center point SAO of the chart image SA coincides with the center point P of the display section  72 . At the time when the center point S 0  of the chart image SA coincides with the center point P, moving the position of the CCD  13  is stopped, the CCD  13  is adhered to the cover glass  16  by the optical adhesive  12  in a state where the center point S 0  coincides with the center point P. 
         [0040]    Since the optical axis t 0  of the optical lenses  8  and  9  points to the center point S 0  of the chart S, the center  51   a  of the image circle  51  of the optical lenses  8  and  9  overlaps with the center point P of the display section  72 . Then, by adjusting the position of the CCD  13  as described above, position of the CCD  13  is adjusted with respect to the optical axis t 0  of the optical lenses  8  and  9 , and thus as shown in  FIG. 5 , it is possible to make the center  51   a  of the image circle  51  of the lenses  8  and  9  coincide with the center  52   a  of the image pickup area  52  of the CCD  13 . The camera head  1  is manufactured by fixedly attaching the CCD  13  to the cover glass  16  in the state where both of the centers coincide with each other. 
         [0041]    With such a configuration, it is possible to obtain the image pickup unit  10  formed so that the center  51   a  of the image circle  51  coincides with the center  52   a  of the image pickup area  52 . 
         [0042]    As described above, in the camera head  1 , the CCD  13  is fixedly attached to the lens block  11  in the state where the center  51   a  of the image circle  51  coincides with the center  52   a  of the image pickup area  52  by the CCD positioning. Thus, it is not necessary to make the image circle  51  have an unnecessary margin set so that the image pickup area  52  is not deviated from the image circle  51 . Specifically, as shown in  FIG. 5 , the image pickup area  52  has a rectangular shape, but it is possible to decrease a size of the image circle  51  as small as possible in a condition where four corners thereof are entirely overlapped with a circumferential edge of the image circle  51 . Accordingly, the image pickup area  52  is just fitted to the inside of the image circle  51 , and thus loss of the image taken by the CCD  13  is not caused. 
         [0043]    As a result, since the image circle  51  decreases as the unnecessary margin of the image circle  51  is not needed. Thus, it is possible to downsize the exteriors of the optical lenses  8  and  9 , and thereby it is also possible to narrow the lens barrel section  15  housing the optical lenses  8  and  9 . Accordingly, it is also possible to reduce the size of the head casing  30  housing the image pickup unit  10 , and it is also possible to downsize the exterior of the camera head  1 , whereby downsizing is achieved. 
         [0044]    Meanwhile,  FIG. 9  shows a camera head  200  in relation to the camera head  1 . The camera head  200  has a CCD unit  201  having a CCD  201   a  fixed thereon and having a cylindrical shape, a screw section  202   a  provided on one end portion thereof, a lens barrel section  202  housing an optical lens  202   b , a barrel member  203  for integrating the CCD unit  201  and the lens barrel section  202 . 
         [0045]    The camera head  200  is manufactured by mounting respectively the CCD unit  201  and the lens barrel section  202  on both side of the barrel member  203 . However, positions of the CCD  201   a  and the lens  202   b  are determined under the condition where the image pickup area of the CCD  201   a  is just not deviated from the image circle of the lens  202   b , that is, the image pickup area of the CCD  201   a  is just included in the image circle. In this camera head  200 , in order to make the image pickup area of the CCD  201   a  be certainly included in the image circle even when the center of the image circle of the lens  202   b  is deviated from the center of the image pickup area of the CCD  201   a  or an exterior size of the CCD  201   a  is not uniform, it has been needed to secure a margin by properly increasing a size of the image circle. Hence, it is necessary to increase a size of the lens  200   b , and thus it is very difficult to downsize the exterior of the barrel member  203 . 
         [0046]    However, the camera head  1  is manufactured by performing the aforementioned CCD positioning that makes the center  51   a  of the image circle  51  coincide with the center  52   a  of the image pickup area  52 , and adhering the CCD  13  to the cover glass  16  in that state. With such a configuration, the camera head  1  is not effected by non-uniformity in the exterior size of the CCD, and by deviation between the center of the image pickup area and a center a of the image circle similar to the camera head  200 . Thus, there is no unnecessary margin of the image circle  51 . As the unnecessary margin of the image circle  51  is eliminated, it is possible to design to downsize the optical lenses  8  and  9 . Thus, it is possible to downsize the exterior of the camera head  1 . 
         [0047]    In particular, as shown in  FIG. 10 , the CCD  13  is formed by the TAB CCD of which a size of a chip  13   b  is substantially equal to a size of a package  13   a  (for example, in a case of 1/10 CCD, about 2 mm×2 mm). In this case, a part that have an influence caused by non-uniformity in the exterior size on the image pickup area decreases. Therefore, it is possible to more downsize the image circle  51 , and thus it is further advantageous in downsizing of the camera head  1 . 
         [0048]    Furthermore, as the image pickup unit  10  is downsized, the head casing  30  can have more space therein, and thus the camera head  1  is appropriate to a medical endoscope  60  that needs a plurality of members as shown in  FIG. 7 . The medical endoscope  60  has an objective lens  61 , a water-jet nozzle  62 , an exhaust nozzle  63 , a light guide  64 , and a forceps channel  65 . 
         [0049]    Furthermore, the image pickup unit  10  is downsized, and thus, as shown in  FIG. 8 , is appropriate to an endoscope camera head  55  that has an illumination LED  51  and the image pickup unit  10  in a head casing  35  and can illuminate the subject by using the illumination LED  51 . The head casing  35  is formed of a barrel member  31  and a barrel member  32 . 
         [0050]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.