Abstract:
An optical-type rotational body position detection apparatus includes a body being rotational in a predetermined angle at each predetermined time interval to cross an optical axis between fixed light emitting and detecting units, including a standard position hole on a rotational locus crossing the axis, and configured such that after rotating the body at one interval from a standard position at which the hole coincides with the axis, a periphery of the hole is positioned outside the periphery at the standard position. The apparatus further includes a restriction unit on a support to cross the axis and to permit light passing and to restrict a diameter of the passing light. The restriction unit restricts the diameter of the passing light to be smaller than a minimum distance within a positional displacement tolerable error range of the hole after the predetermined angled rotation of the body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2008-191643, filed Jul. 25, 2008, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an optical-type rotational body position detection apparatus 
         [0004]    2. Description of the Related Art 
         [0005]    An optical-type rotational body position detection apparatus is already known from, for example, Japanese Patent Application KOKAI Publication No. 2000-162335. 
         [0006]    This publication discloses an apparatus for optically detecting standard positions of a second wheel, a minute wheel and an hour wheel in order to detect standard positions of a second hand, a minute hand and an hour hand in a hand type wrist watch, that is, an optical-type rotational body position detection apparatus. 
         [0007]    The second wheel of the hand type wrist watch is rotated in a unit of a predetermined angle at each of predetermined time intervals by a first driving system which includes a first driving motor and a plurality of intermediate wheels. Each of the minute wheel and the hour wheel of the hand type wrist watch is rotated in a unit of a predetermined angle at each of predetermined time intervals by a second driving system which includes a second driving motor and a plurality of intermediate wheels. The second wheel, the minute wheel and the hour wheel are coaxially rotatably supported by a main plate. The optical-type rotational body position detection apparatus includes a light emitting device functioning as a light emitting unit, and a light receiving device functioning as a eight detecting unit, which are disposed in both sides of the second wheel, minute wheel and hour wheel. 
         [0008]    A standard position light transmission hole is formed in each of the second wheel, minute wheel and hour wheel so that the light transmission hole is positioned on a rotational locus on each wheel, which intersects an optical axis connecting the light emitting device and the light receiving device. 
         [0009]    With the above-described conventional optical-type rotational body position detection apparatus which is combined with the conventional hand-type wrist watch, when a need has occurred to set the standard positions of the second hand, minute hand and hour hand (i.e. the standard positions of the second wheel, minute wheel and hour wheel), the second wheel is rotated by the first driving system and the minute wheel and hour wheel are rotated by the second driving system while light is being emitted by the light emitting device. When the standard position light transmission holes of the second wheel, minute wheel and hour wheel coincide with the above-described optical axis during the rotations of these wheels, the light receiving device can detect the light from the light emitting device and it is recognized that at this time the second hand, minute hand and hour hand (i.e. the second wheel, minute wheel and hour wheel) are set at their standard positions. 
         [0010]    However, owing to the manufacturing tolerable error of each of the second wheel, minute wheel and hour wheel, the manufacturing tolerable error of each of the plural intermediate wheels of the first driving system and the manufacturing tolerable error of each of the plural intermediate wheels of the second driving system, back-lashes occur in each of the combination of the second wheel and the various intermediate wheels of the first driving system and the combination of the minute wheel, and hour wheel and the various intermediate wheels of the second driving system. In addition, the standard position light transmission hole of each of the second wheel, minute wheel and hour wheel has a manufacturing tolerable error. 
         [0011]    Thus, even if the standard position light transmission hole of each of the second wheel, minute wheel and hour wheel coincides with the above-described optical axis and the light receiving device can detect the light from the light emitting device so that it is detected that the second wheel, minute wheel and hour wheel are positioned at their standard positions (i.e. the second hand, minute hand and hour hand are positioned at their standard positions), it is possible that the center of the standard position light transmission hole of each of the second wheel, minute wheel and hour wheel does not coincide with the above-described optical axis and hence the second hand, minute hand and hour hand are slightly displaced from their standard positions. This means that, in the case where the standard positions of the hour hand, minute hand and second hand are at 0 hour: 0 minute: and 0 second, the second hand, minute hand and hour hand do not completely overlap with each other at these standard positions. 
         [0012]    The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide an optical-type rotational body position detection apparatus which can detect the position of a rotational body more precisely than in the prior art. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    According to an aspect of the present invention, an optical-type rotational body position detection apparatus comprises: a light emitting unit which is configured to emit light; a light detecting unit which is configured to detect light; a fixing support member which supports the light emitting unit and the light detecting unit such that the light emitting unit and the light detecting unit are mutually opposed to and spaced apart from each other, and that light from the light emitting unit is detected by the light detecting unit; a rotational body which rotates in a predetermined angle at each of predetermined time intervals to cross an optical axis connecting the light emitting unit and the light detecting unit, which includes a standard position light transmission hole disposed on a rotational locus crossing the optical axis, and which is configured such that after the rotational body takes one rotational movement over the predetermined angle within the predetermined time interval from a standard position at which a center of the standard position light transmission hole coincides with the optical axis, a peripheral edge of the standard position light transmission hole is positioned outside the peripheral edge of the standard position light transmission hole positioned at the standard position; and a light transmission restriction unit which is integrally provided on the fixing support member, which is disposed at a position crossing the optical axis, which permits passing of light, and which restricts a diameter of the passing light. 
         [0014]    The light transmission restriction unit restricts the diameter of the light passing therethrough in such a manner that the diameter of the passing light is restricted to a diameter which is smaller than a minimum distance from the peripheral edge of the standard position light transmission hole to the optical axis within a range of a tolerable error of a positional displacement caused in the standard position light transmission hole by the one rotational movement over the predetermined angle with the predetermined time interval of the rotational body. 
         [0015]    Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0016]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
           [0017]      FIG. 1  is a plan view which schematically shows the external appearance of a hand type wrist watch which is combined with an optical-type rotational body position detection apparatus according to an embodiment of the present invention; 
           [0018]      FIG. 2  is a vertical cross-sectional view which schematically shows a main part of a time-piece module of the hand type wrist watch shown in  FIG. 1 ; 
           [0019]      FIG. 3  is a back side view which schematically shows a second wheel, parts of a first driving system for driving the second wheel, and parts of a second driving system for driving a minute wheel and an hour wheel in the time-piece module shown in  FIG. 2 ; 
           [0020]      FIG. 4  is a vertical cross-sectional view which schematically shows, in enlarged scale, the mutually coaxially rotatably disposed second wheel, minute wheel and hour wheel, and an intermediate wheel of the second diving system for driving the minute wheel and hour wheel in the time-piece module shown in  FIG. 2 , these wheels being disposed at standard positions where standard position light transmission holes of the respective wheels are made to coincide with an optical axis between a light emitting unit and a light detecting unit; 
           [0021]      FIG. 5  is a schematic exploded view showing the standard position light: transmission holes which are formed in the second wheel, minute wheel, hour wheel and intermediate wheel shown in  FIG. 4 , which are depicted as being separated from each other; 
           [0022]      FIG. 6  is an enlarged view showing, in enlarged scale, the second wheel shown in  FIG. 5 ; 
           [0023]      FIG. 7  shows a signal pattern which is obtained by the combination of the light emitting unit and light detecting unit via a plurality of light transmission holes including a standard position light transmission hole in the second wheel while the second wheel shown in  FIG. 6  is being rotated; 
           [0024]      FIG. 8  schematically shows the state in which the standard position light transmission hole of the second wheel shown in  FIG. 6  has been rotated and moved from the optical axis between the light emitting unit and light detecting unit in accordance with the rotation of the second wheel of  FIG. 6  over a predetermined rotation angle of a single predetermined time interval; 
           [0025]      FIG. 9  shows, in enlarged scale, the standard position light transmission holes of the second wheel, minute wheel, hour wheel and intermediate wheel of the second driving system for the minute wheel and hour wheel, which are disposed at the standard positions in  FIG. 4 , together with a light transmission restriction hole of a light transmission restriction unit of the optical-type rotational body position detection apparatus according to the embodiment of the invention; 
           [0026]      FIG. 10  is a vertical cross-sectional view showing, in engaged scale, a part of the time-piece module of  FIG. 2  along line X-X in  FIG. 9 ; 
           [0027]      FIG. 11  shows, in enlarged scale, the state in which the standard position light transmission hole of the second wheel is moved away from the other standard position transmission holes and the light transmission restriction hole of the night transmission restriction unit, after the rotation of the second wheel over a predetermined rotation angle of a single predetermined time interval in  FIG. 9 ; 
           [0028]      FIG. 12  is an enlarged vertical cross-sectional view, taken along line XII-XII in  FIG. 11 , of a part of the time-piece module of  FIG. 2  in the state of 
           [0029]      FIG. 13  shows, in enlarged scale as in  FIG. 11 , the state in which the standard position light transmission hole of the second wheel is moved away from the other standard position transmission holes and the light transmission restriction hole of the light transmission restriction unit, after the second wheel is rotated, with a rotational movement tolerable error, over a predetermined rotation angle of a single predetermined time interval in  FIG. 9 ; 
           [0030]      FIGS. 14A ,  14 B,  14 C,  14 D,  145 ,  14 F,  14 G,  14 H,  14 I,  14 J,  14 K,  14 L and  14 M schematically show the state in which a plurality of arcuate light transmission holes formed in the second wheel and light-blocking portions therebetween cooperate with the optical axis, while the second wheel rotates from the standard position, where the standard position light transmission hole of the second wheel coincides with the optical axis between the light emitting unit and light detecting unit, to a position immediately before the second wheel completes a single rotation by a predetermined number of times of rotation over a predetermined rotation angle of a predetermined time interval; 
           [0031]      FIG. 15  is a circuit diagram which schematically shows the circuit structure of the hand type wrist watch shown in  FIG. 1 ; 
           [0032]      FIG. 16  is a flow chart of the procedure for disposing the second wheel, or a kind of rotational body, in the time-piece module of the hand type wrist watch of  FIG. 1  at the standard position by the optical-type rotational body position detection apparatus according to the embodiment of the present invention; 
           [0033]      FIG. 17  is an enlarged view similar to  FIG. 9 , showing a time-piece module of the hand type wrist watch of  FIG. 1 , which is combined with an optical-type rotational body position detection apparatus according to an embodiment of the invention involving a first modification of the light transmission restriction unit; 
           [0034]      FIG. 18  is a vertical cross-sectional view similar to  FIG. 10 , taken along line XVIII-XVIII in  FIG. 17 ; 
           [0035]      FIG. 19  is an enlarged view similar to  FIG. 11 , showing the time-piece module of the hand type wrist watch of  FIG. 1 , which is combined with the optical-type rotational body position detection apparatus according to the embodiment of the invention involving the first modification of the light transmission restriction unit; 
           [0036]      FIG. 20  is a vertical cross-sectional view similar to  FIG. 12 , taken along line XX-XX in  FIG. 19 ; 
           [0037]      FIG. 21  is a vertical cross-sectional view similar to  FIG. 10 , showing a time-piece module of the hand type wrist watch of  FIG. 1 , which is combined with an optical-type rotational body position detection apparatus according to an embodiment of the invention involving a second modification of the light transmission restriction unit; 
           [0038]      FIG. 22  is a vertical cross-sectional view similar to  FIG. 10 , showing a time-piece module of the hand type wrist watch of  FIG. 1 , which is combined with an optical-type rotational body position detection apparatus according to an embodiment of the invention involving a third modification of the light transmission restriction unit; 
           [0039]      FIG. 23  is a vertical cross-sectional view similar to  FIG. 12 , showing the time-piece module of  FIG. 22 ; and 
           [0040]      FIG. 24  is an enlarged view similar to  FIG. 6 , showing a modification of a plurality of arcuate light transmission holes, which are used along with the standard position light transmission hole in the second wheel that is used as a kind of rotational body, and light-blocking portions between the arcuate light transmission holes in a time-piece module of the hand type wrist watch of  FIG. 1  which is combined with an optical-type rotational body position detection apparatus according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiment 1 
       [0041]      FIG. 1  schematically shows the external appearance of a hand type wrist watch which is combined with an optical-type rotational body position detection apparatus according to an embodiment of the present invention.  FIG. 2  schematically shows a cross section of a main part of a time-piece module of the hand type wrist watch shown in  FIG. 1 . 
         [0042]    The hand type wrist watch includes a time-piece module  1  which is accommodated in the inner space of a substantially cylindrical watch case TK. The time-piece module  1  includes a dial plate  5 ; a second hand  2 , a minute hand  3  and a hour hand  4  which are rotated  25  over the surface of the dial plate  5 ; and time-piece movement  8  for driving the second hand  2 , minute hand  3  and hour hand  4 , the time-piece movement  8  being disposed between an upper housing  6  and a lower housing on the back side of the dial plate  5 . 
         [0043]    In the inner space of the watch case TK, an opening on the dial plate  5  side is covered with a watch glass. In this inner space, an opening on the side opposite to the dial plate  5  is covered with a case back. A pair of strap attachment portions, to which proximal end portions of a pair of watch straps are attached, are formed at two diametrically opposed parts of the watch case TK on the peripheral surface of the watch case TK. In addition, a plurality of push buttons for causing the time-piece module  1  to execute various functions are disposed between the paired strap attachment portions on the peripheral surface of the watch case TK. 
         [0044]    The dial plate  5  is formed of a light transmissive material. The time-piece module  1  includes a solar panel  9  between the upper housing  6  and the dial plate  5 . The time-piece movement  8  includes a circuit board  10  which is disposed along the inner surface of the lower housing  7 , and a support board  33  which is disposed along the inner surface of the upper housing  6 . A battery (not shown) is held on the circuit board  10 . Electricity, which is generated by the solar panel  9 , is accumulated in the battery. 
         [0045]    The time-piece movement  8  includes, between the upper housing  6  and the support board  33  on the inside of the upper housing  6 , on one hand, and the circuit board  10  on the inside of the lower housing  7 , on the other hand, a main plate  14 , a train wheel bridge  15 , a center wheel bridge  16  and a minute wheel hold plate  34 , which support a first driving system  11  for rotating and driving the second hand  2  and a second driving system  12  for rotating and driving the minute hand  3  and hour hand  4 . The time-piece movement  8  further includes a position detector  13  for detecting the positions of the second hand  2 , minute hand  3  and hour hand  4 . 
         [0046]    The main plate  14 , train wheel bridge  15  and center wheel bridge  16  support a second wheel (fourth wheel)  20 , a minute wheel (center wheel)  25  and an hour wheel  27  such that these wheels are mutually concentric and rotatable to each other. 
         [0047]    As shown in  FIG. 4  in enlarged scale, the second wheel  20  includes a second hand shaft  20   a  which penetrates the minute wheel hold plate  34 , support board  33 , upper housing  6 , solar panel  9  and a hand shaft pass hole  5   a  of the dial plate  5 . The second hand  2  is fixed to an outer end of the second hand shaft  20   a , which projects to the outside of the dial plate  5 . The minute wheel  25  includes a cylindrical minute hand shaft  25   a  which penetrates the minute wheel hold plate  34 , support board  33 , upper housing  6 , solar panel  9  and the hand shaft pass hole  5   a  of the dial plate  5  along the outer peripheral surface of the second hand shaft  20   a . The minute hand  3  is fixed to an outer end of the minute hand shaft  25   a , which projects to the outside of the dial plate  5 . Further, the hour wheel  27  includes a cylindrical hour hand shaft  27   a  which penetrates the minute wheel hold plate  31 , support hoard  33 , upper housing  6 , solar panel  9  and hand shaft pass hole  5   a  of the dial plate  5  along the outer peripheral surface of the minute hand shaft  25   a . The hour hand  4  is fixed to an outer end of the hour hand shaft  27   a , which projects to the outside of the dial plate  5 . 
         [0048]    As shown in  FIG. 2  and  FIG. 3 , the first driving system  11  includes a first stepping motor  17 , and a fifth wheel  18  which is rotatably supported on the train wheel bridge  15  and transmits a torque from the first stepping motor  17  to the second wheel (fourth wheel)  20 . 
         [0049]    The first stepping motor  17  includes a stator  17   b  around which a coil  17   a  is wound; a rotor  17   c  which is supported to be rotatable relative to the stator  17   b ; and a rotor output wheel  17   d  which is fixed concentric to the rotor  17   c . The rotor  17   c  is equipped with a permanent magnet which is magnetized in a constant state. The coil  17   a , which is supplied with electric current from the above-described battery (not shown), generates a magnetic field. By the magnetic field that is led to the stator  17   b , the rotor  17   c  is rotated stepwise in units of 180 20  . The rotation of the rotor  17   c  is transmitted to the second wheel (fourth wheel)  20  via the fifth wheel  18 , and further transmitted to the second hand  2  via the second hand shaft  20   a.    
         [0050]    The second wheel  20  is provided with a first light transmission hole portion  21  which is used in order to detect the standard position of the second wheel  20  in cooperation with the position detector  13 . The details of the first light transmission hole portion  21  will be described later. 
         [0051]    As shown in  FIG. 2  and  FIG. 3 , the second driving system  12  includes a second stepping motor  22 ; an intermediate wheel  23  which is rotatably supported on the main plate  14  and train wheel bridge  15  and to which a torque from the second stepping motor  22  is transmitted; and a third wheel  24  which is rotatably supported on the main plate  14  and center wheel bridge  16  and transmits a torque from the intermediate wheel  23  to the minute wheel (center wheel)  25 . 
         [0052]    As shown in  FIG. 2  to  FIG. 4 , the second driving system  12  includes the second stepping motor  22 ; the intermediate wheel  23  which is rotated by the second stepping motor  22 ; the third wheel  24  which is rotated by the intermediate wheel  23 ; the minute wheel  25  that is the center wheel, which is rotated by the third wheel  24 ; a minute wheel  26  which is rotated by the minute wheel  25 ; and the hour wheel  27  which is rotated by the minute wheel  26 . The minute hand  3  is attached t the minute hand shaft  25   a  of the minute wheel  25 , and the hour hard  4  is attached to the hour hand shaft  27   a  of the hour wheel  27 . 
         [0053]    As shown in  FIG. 3 , the second stepping motor  22  includes a coil  22   a , a stator  22   b  and a rotor  22   c . Like the first stepping motor  17 , electric current is supplied to the coil  22   a  to generate a magnetic field. The magnetic field, which is generated by the coil  22   a , is led to the stator  22   b . By the magnetic field that is led to the stator  22   b , the rotor  22   c , which includes a permanent magnet that is magnetized (i.e. polarized with an N pole and an S pole) in a constant state, is rotated stepwise in units of 180°. 
         [0054]    As shown in  FIG. 2  and  FIG. 3 , the intermediate wheel  23  rotates in mesh with a rotor pinion  22   d  of the rotor  22   c  of the second stepping motor  22 . As shown in  FIG. 5 , the intermediate wheel  23  is provided with a fourth light transmission hole portion  30 . The third wheel  24  rotates in mesh with a pinion  23   a  of the intermediate wheel  23 , and the minute wheel  25  rotates in mesh with a pinion  24   a  of the third wheel  24 . As shown in  FIG. 2  and  FIG. 4 , the second hand shaft  20   a  of the second wheel  20  is rotatably inserted in a central portion of the minute wheel  25 , and the upwardly projecting cylindrical minute hand shaft  25   a  is provided at the central portion of the minute wheel  25 . 
         [0055]    As shown in  FIG. 2 , the minute hand shaft  25   a  Is configured to project upward through the through-holes  5   a  of the upper housing  6 , solar panel  9  and dial plate  5 , and the minute hand  3  is attached to the projecting distal end portion thereof, as shown in  FIG. 4 . Thereby, the minute wheel  25  is disposed coaxial with the second wheel  20  in the state in which the minute wheel  25  overlaps the second wheel  20  on the lower side. In addition, as shown in  FIG. 5 , the minute wheel  25  is provided with a second light transmission hole portion  28 . 
         [0056]    As shown in  FIG. 2 , the minute wheel  26  is held by the minute wheel hold plate  34  so as to be rotatable together with the hour wheel  27 . In this state, the minute wheel  26  rotates in mesh with the pinion  25   a  of the minute wheel  25 . As shown in  FIG. 2 , the hour wheel  27  rotates in mesh with a pinion  26   a  of the minute wheel  26 . As shown in  FIG. 4 , the minute hand shaft  25   a  of the minute wheel  25  is rotatably inserted in a central portion of the hour wheel  27 , and the upwardly projecting cylindrical hour hand shaft  27   a  is provided at the central portion of the hour wheel  27 . 
         [0057]    As shown in  FIG. 2 , the hour hand shaft  27   a  is configured to project upward through the through-holes  5   a  of the minute wheel hold plate  34 , upper housing  6 , solar panel  9  and dial plate  5 , and the hour hand  4  is attached to the projecting distal end portion thereof, as shown in  FIG. 4 . Thereby, the hour wheel  27  is disposed coaxial with the second wheel  20  and minute wheel  25  in the state in which the hour wheel  27  overlaps the minute wheel  25  on the lower side. In addition, as shown in  FIG. 5 , the hour wheel  27  is provided with a third light transmission hole portion  29 . 
         [0058]    In the meantime, a hand position detection apparatus, which detects the positions of the hand wheels in this watch, is configured to optically detect, by the position detector  13 , the positions of the first to fourth light transmission hole portions  21  and  28  to  30  which are provided in the second wheel  20 , minute wheel  25 , hour wheel  27  and intermediate wheel  23 , thereby detecting the rotational positions of the second wheel  20 , minute wheel  25 , hour wheel  27  and intermediate wheel  23 . Thus, the hand position detection apparatus determines the rotational positions of the second hand  2 , minute hand  3  and hour hand  4 . 
         [0059]    Specifically, as shown in  FIG. 2 ,  FIG. 4  and  FIG. 10 , the position detector  13  includes a light emitting device  31  and a light receiving device  32 . A detection position P is provided on an optical axis  13   a  which connects the light emitting device  31  and light receiving device  32 . The light emitting device  31  is composed of an LED (light-emitting diode) and, as shown in  FIG. 2 ,  FIG. 4  and  FIG. 10 , the light emitting device  31  is provided on the support board  33  on the lower surface of the upper-side upper housing  6  at a position where the second wheel  20 , minute wheel  25  and hour wheel  27  coaxially overlap and also the intermediate wheel  23  partly overlaps. The light receiving device  32  is composed of a photo-transistor, and is provided on the circuit board  10  on the lower side (the upper side in  FIG. 2 ) at a position corresponding to the light emitting device  31 . 
         [0060]    Thereby, as shown in  FIG. 2 ,  FIG. 4  and  FIG. 10 , when all the first to fourth light transmission hole portions  21  and  28  to  30  of the second wheel  20 , minute wheel  25 , hour wheel  27  and intermediate wheel  23  have come to correspond on the optical axis  13   a , the light receiving device  32  receives light from the light emitting device  31  through the first to fourth light transmission hole portions  21  and  28  to  30 , and thus the position detector  13  is configured to detect the rotational positions of the second wheel  20 , minute wheel  25  and hour wheel  27 . 
         [0061]    In this case, as shown in  FIG. 6 , the first light transmission hole portion  21  of the second wheel  20  includes a first circular hole  21   a  which is a standard hole provided at a standard position (0°) of the second wheel  20 ; second and third elongated holes  21   b  and  21   c  which are provided on both sides of the first circular hole  21   a , that is, on both the hand rotating direction side of the second hand  2  and the opposite direction side thereof with respect to the first circular hole  21   a , with first and second high-blocking portions  21   d  and  21   e  having different distances being interposed; and a third light-blocking portion  21   f  which is positioned on a diagonal of the first circular hole  21   a  between the second and third elongated holes  21   b  and  21   c.    
         [0062]    As shown in  FIG. 6 , the first circular hole  21   a  is formed to have a hole diameter of about 0.3 to 0.4 mm, (a width of about 12° relative to the circumference of the second wheel  20 ), taking into account the diameter of about 3 to 5 mm of the second wheel  20 . Of the second and third elongated holes  21   b  and  21   c , the second elongated hole  21   b  is formed, as shown in  FIG. 6 , in an arcuate shape corresponding to the rotational movement locus of the first circular hole  21   a  from an approximately 48° position (8-step position, i.e. 8-second position) in a counterclockwise direction, with the center of the first circuit hole  21   a  being set as a standard (0°), to an approximately 168° position (28-step position, i.e. 28-second position). 
         [0063]    The third elongated hole  21   c , as shown in  FIG. 6 , is formed in an arcuate shape corresponding to the rotational movement locus of the first circular hole  21   a  from an approximately 192° position (32-step position, i.e. 32-second position) in the counterclockwise direction, with the center of the first circuit hole  21   a  being set as the standard (0°), to an approximately 300° position (50-step position, i.e. 50-second position). In this case, of the first and second light-blocking portions  21   d  and  21   e,  the first light-blocking portion  21   d , which is positioned on the side (the counterclockwise side in  FIG. 6 ) opposite to the hand rotating direction side of the second hand  2 , is provided, as shown in  FIG. 6 , with an interval of about three times the diameter (12° width) of the first circular hole  21   a , that is, with a width interval of substantially about 36° in a range from the standard position (0° position) that is the center of the first circular hole  21   a  to an about 48° position (8-step position, i.e. 8-second position) counterclockwise. 
         [0064]    The second light-blocking portion  21   e , which is positioned on the hand rotating direction side of the second hand  2 , is provided with an interval which is longer than the interval of the first light-blocking portion  21   d  by a distance corresponding to the diameter of the first circular hole  21   a , that is, about four times the diameter of the first circular hole  21   a , to be more specific, with a width interval of substantially about 48° in a range from the standard position (0° position) that is the center of the first circular hole  21   a  to an about 60° position (50-step position, i.e. 50-second position) clockwise The third light-blocking portion  21   f , as shown in  FIG. 6 , is formed to have substantially the same size as the diameter of tie first circular hole  21   a , and the third light-blocking portion  21   f  is positioned on the diagonal of the first circular hole  21   a  between the second and third elongated holes  21   b  and  21   c.    
         [0065]    The first light-blocking portion  21   d  corresponds to a part of the third elongated hole  21   c  that is located on a diagonal of the first light-blocking portion  21   d . The second light-blocking portion  21   e  corresponds to a part of the second elongated hole  21   b  that is located on a diagonal of the second light-blocking portion  21   e . The third light-blocking portion  21   f  corresponds to the first circular hole  21   a  that is located on a diagonal of the third light-blocking portion  21   f . Accordingly, the second wheel  20  is configured such that if the second wheel  20  rotates over 180° (half rotation) in the state in which any one of the first to third light-blocking portions  21   d  to  21   f  corresponds to the detection position P of the position detector  13  (the position where the light emitting device  31  and light receiving device  32  are opposed to each other), any one of the first circular hole  21   a  and second and third elongated holes  21   b  and  21   c  necessarily corresponds to the detection position P of the position detector  13 . 
         [0066]    The second wheel  20  rotates in units of one step (rotation angle=6° rotation time=1 second). When the position detector  13  performs detection in every two seconds (2 steps) while the second wheel  20  rotates by 60 steps (rotation angle=360°: rotation time=60 seconds), a detection pattern as shown in  FIG. 7  is obtained by the detector  13 . Specifically, when the second wheel  20  is at a 0-second position (0°), the position detector  13  detects the first circular hole  21   a . When the second wheel  20  is between a 2-second position (12°) and a 6-second position (36°), the position detector  13  is blocked by the first light-blocking portion  21   d , and an undetection state, in which no light is detected by the position detector  13 , continues three times. 
         [0067]    When the second wheel  20  is between an 8-second position (48°) and a 28-second position (168°), the position detector  13  continuously detects the second elongated hole  21   b . When the second wheel  20  is at a 30-second position (180°), the detector  13  is blocked by the third light-blocking portion  21   f , and there comes an undetection state in which no light can be detected by the position detector  13 . When the second wheel  20  is between a 32-second position (192°) and a 50-second position (300°), the position detector  13  continuously detects the third elongated hole  21   c . When the second wheel  20  is between a 52-second position (312°) and a 58-second position (348°), the position detector  13  is blocked by the second light-blocking portion  21   e , and an undetection state, in which no light can be detected by the position detector  13 , continues four times. 
         [0068]    On the other hand, as shown in  FIG. 5 , the second light transmission hole portion  28  of the minute wheel  25  is a single circular hole which is provided at the standard position (0°) of the minute wheel  25 . The circular hole of the second light transmission hole portion  28  has substantially the same size as the first circular hole  21   a  of the second wheel  20 , and is provided at a position corresponding to the first circular hole  21   a  of the second wheel  20 . The third light transmission hole portion  29  of the hour wheel  27  comprises eleven circular holes which are provided at intervals of 30° along the circumference from the standard position (0°) of the hour wheel  27 . As shown in  FIG. 5 , a fourth light-blocking portion  29   a  is provided between the circular hole at the standard position and the eleventh circular hole, that is, at an eleven o&#39;clock position. 
         [0069]    The fourth light transmission hole portion  30  of the intermediate wheel  23 , as shown in  FIG. 5 , is a single circular hole which corresponds to the single circular hole that is the second light transmission hole portion  28  of the minute wheel  25 . The circular hole of the fourth light transmission hole portion  30  has substantially the same size as each of the first circular hole  21   a  of the second wheel  20  and the circular hole that is the second light transmission hole portion  28  of the minute wheel  25 . Thereby, the intermediate wheel  23 , minute wheel  25  end hour wheel  27  of the second driving system  12  are configured such that all the second to fourth light transmission hole portions  28  to  30  overlap a, the detection position P of the position detector  13  every hour on the hour of the hour hand  4  (0 o&#39;clock, one o&#39;clock, two o&#39;clock, three o&#39;clock, four o&#39;clock, five o&#39;clock, six o&#39;clock, seventh o&#39;clock, eight o&#39;clock, nine o&#39;clock, ten o&#39;clock, and eleven o&#39;clock), except the eleven o&#39;clock position. 
         [0070]    As shown in  FIG. 9  and  FIG. 10 , the hand position detection apparatus is configured such that the detection position P of the position detector  13  is provided at a location where all the second wheel  20 , minute wheel  25  and hour wheel  27  overlap and the third wheel  24  is nearby, and such that the first to fourth light transmission hole portions  21  and  28  to  30  overlap on the optical axis  13   a  of the detection position P and the detection position P is provided at a position corresponding to an opening portion  34   a  of the minute wheel hold plate  34 , an opening portion  14   a  of the main plate  24  and a light leak restriction hole  15   a  that is an opening portion of the train wheel bridge  15 . 
         [0071]    The hand position detection apparatus is thus configured to detect the rotation positions of the second wheel  20 , minute wheel  25  and hour wheel  27  when the light from the light emitting device  31  of the position detector  13  is transmitted through all the first to fourth light transmission hole portions  21  and  28  to  30 , the opening portion  34   a  of the minute wheel hold plate  34 , the opening portion  14   a  of the main plate  14  and the light leak restriction hole  15   a  of the train wheel bridge  15 , and is received by the light receiving device  32 . 
         [0072]    In this case, as shown in  FIG. 10 , the light emitting device  31  is provided on the lower surface of the support board  33  that is provided under the upper housing  6 . Specifically, a pair of electrodes  33   a  and  33   b  is provided on the lower surface of the support board  33 . An upper side electrode of the light emitting device  31  is disposed on and connected to one electrode  33   a , and a lower side electrode of the light emitting device  31  is connected to the other electrode  33   b  over a lead line  33   c . In this state, the light emitting device  31  is covered with a mold resin  33   d . The light emitting device  31  is configured such that the mold resin  33   d  is inserted in the opening portion  34   a , which is provided in the minute wheel hold plate  34 , and is disposed near the hour wheel  27  that is positioned thereunder. 
         [0073]    The light receiving device  32 , as shown in  FIG. 10 , is provided in an attachment recess portion  10   a  of the circuit board  10  that is provided on the lower housing  7 , such that the light receiving device  32  is opposed to the light emitting device  31 . Specifically, a pair of electrodes  10   b  and  10   c  is provided on the upper surface of the circuit board  10 . A lower side electrode of the light receiving device  32  is disposed on and connected to one electrode  10   b , and an upper side electrode of the light receiving device  32  is connected to the other electrode  10   c  over a lead line  10   d . In this state, the light receiving device  32  is covered with a mold resin  10   e.    
         [0074]    The light receiving device  32  is configured in the following fashion. As shown in  FIG. 10 , the mold resin  10   e  protrudes to the upper side of the circuit board  10 , and the protruding part of the mold resin is inserted in a receiving recess portion  15   b  which is provided in the lower surface of the train wheel bridge  15 . The protruding part of the mold resin  10   e  is disposed close to the light leak restriction hole  15   a  of the train wheel bridge  15 . 
         [0075]    Thereby, in the position detector  13 , as shown in  FIG. 9  and  FIG. 10 , the detection position P is provided on the optical axis  13   a  which connects the centers of the light emitting device  31  and light receiving device  32 . Specifically, as shown in  FIG. 9  and  FIG. 10 , the detection position P is configured to be a columnar space region having a center axis corresponding to the optical axis  13   a , and the diameter of the columnar space region is substantially equal to the diameter of the light leak restriction hole  15   a  of the train wheel bridge  15 , which will be described later. 
         [0076]    The main plate  14 , as shown in  FIG. 10 , is fixed between the hour wheel  27  and minute wheel  25 , and is provided with the opening portion  14   a  in which the third wheel  24  that is near the detection position P is rotatably disposed. The main plate  14  is configured such that the main plate  14 , together with the train wheel bridge  15 , rotatably supports the hour wheel  27 , minute wheel  25  and third wheel  24  in the state in which the hour wheel  27 , minute wheel  25  and third wheel  24  are disposed close to each other without being put in contact. The train wheel bridge  15  is fixed between the circuit board  10  and the second wheel  20  and is configured such that the train wheel bridge  15 , together with the main plate  14 , rotatably supports the hour wheel  27 , intermediate wheel  23  and second wheel  20  in the state in which the hour wheel  27 , intermediate wheel  23  and second wheel  20  are disposed close to each other without being put in contact. 
         [0077]    In the meantime, as shown in  FIG. 9  to  FIG. 10 , the second wheel  20 , minute wheel  25 , hour wheel  27  and intermediate wheel  23  are configured such that at the standard position (the position of 0 hour; 0 minute: 0 second) the first to fourth light transmission hole portions  21  and  28  to  30  (overlap the opening portion  34   a  of the minute wheel hold plate  34 , the opening portion  14   a  of the main plate  14  and the light leak restriction hole  15   a  of the train wheel bridge  15 , which are positioned at the detection position P of the detector  13 . 
         [0078]    As regards the second wheel  20 , minute wheel  25 , hour wheel  27  and intermediate wheel  23 , if the second wheel  20  rotates from the standard position (0°: 0 second) by two steps (12°: 2 seconds), as shown in  FIG. 11  and  FIG. 12 , the first circular hole  21   a  that is the standard hole of the first light transmission hole portion  21  is substantially completely apart from the detection position P of the detector  13 , and the second wheel  20  is configured to block the light from the light emitting device  31 . 
         [0079]    In this case, if the second wheel  20  rotates from the standard position (0°: 0 second) by one step (6°: 1 second), as shown in  FIG. 8 , the first circular hole  21   a  that is the standard hole does not completely apart from the detection position P of the position detector  13 , and about half the light from the light emitting device  31  passes through the first circular hole  21   a  and is received by the light receiving device  32 . Thus, the position detector  13  is configured to execute light detection each time the second wheel rotates by two steps, when the position detector  13  detects the rotation position of the second wheel  20 . 
         [0080]    In the meantime, the light leak restriction hole  15   a  which is provided in the train wheel bridge  15  is configured in the following fashion. When the first circular hole  21   a  that is the standard hole of the second wheel  20  corresponds to the detection position P and the light receiving device  32  receives the light from the light emitting device  31 , the second wheel  20  rotates by a minimum angle (12°) at every timing (2 seconds) when the position detector  13  performs light detection, and, as shown in  FIG. 12  and  FIG. 13 , the first circular hole  21   a  rotates to a position where the first circular hole  21   a  is completely apart from the detection position P. The light leak restriction hole  15   a  is configured to prevent light leak from this rotated and moved first circular hole  21   a.    
         [0081]    Specifically, as shown in  FIG. 12  and  FIG. 13 , the light leak restriction hole  15   a  of the train wheel bridge  15  is formed such that a light transmission region E 1  thereof, through which light passes, is narrowed by a maximum displacement amount R 1 , in consideration of the maximum displacement amount R 1  in rotational movement of the first circular hole  21   a  which is caused by the rotation of the second wheel  20  when the second wheel  20  rotates by a minimum angle (12°) at every timing (2 seconds) of light detection by the position detector  13  and the first circular hole  21   a  rotates to a position where the first circular hole  21   a  is completely apart from the detection position P. The displacement amount R 1  of the first circular hole  21   a  occurs due to the precision in fabrication of the second wheel  20  or back-lash. 
         [0082]    Such a displacement amount R 1  similarly occurs with respect to the second and third elongated holes  21   b  and  21   c  in the first light transmission hole portion  21  of the second wheel  20 . Furthermore, as regards the second to fourth light transmission hole portions  28  to  30  of the minute wheel  25 , hour wheel  27  and intermediate wheel  23 , displacement amounts R 2  to R 2  similarly occur. However, the minute wheel  25  of the second driving system  12  rotates by one step (6°) in every one minute, and light detection is performed by the position detector  13  in every one step. 
         [0083]    Accordingly, if the minute wheel  25  rotates by one step, the intermediate wheel  23  rotates by 30° in interlock with the rotation of the minute wheel  25 . Thereby, even if the second Light transmission hole portion  28  is not completely apart from the detection position P of the position detector  13 , the fourth light transmission hole portion  30  of the intermediate wheel  23  moves greatly away from the detection position P, thereby blocking the light from the light emitting device  31  by the intermediate wheel  23 . Thus, light detection by the position detector  13  can be performed in every one step (one minute) of the minute wheel  25 . 
         [0084]    Next, referring to  FIG. 14 , a description is given of a basic second wheel position detection operation for detecting the standard position (“00” second position) of the second wheel  20 . 
         [0085]    In this basic second wheel position detection operation, the minute wheel  25 , hour wheel  27  and intermediate wheel  23  of the second driving system  12  are ignored.  FIG. 14A  to  FIG. 14M  show the correspondence between the rotation position of the second wheel  20  and the detection position P of the position detector  13  when the second wheel  20  rotates in units of two steps (rotation angle: 12°). 
         [0086]    The object of detecting the standard position of the second wheel  20  is to detect the standard position (0°: 0 second) of the second wheel  20  shown in  FIG. 14A . That is, the object is to detect the position where the first circular hole  21   a  of the first light transmission hole portion  21  of the second wheel  20  coincides with the detection position P of the position detector  13 . The state in which the second wheel  20  is at the standard position is the state of  FIG. 14A . In this state, the first circular hole  21   a  of the first light transmission hole portion  21  of the second wheel  20  coincides with the detection position P of the position detector  43 , and fight can he detected by the detector  13 . 
         [0087]    To begin with, if the second wheel  20  rotates by two steps in the state of  FIG. 14A  and the rotation angle becomes 12°, the first circular hole  21   a  is displaced clockwise from the detection position P, as shown in  FIG. 14B , and a part of the first light-blocking portion  21   d  corresponds to the detection position P. Thus, no light can be detected by the position detector  13 , and there comes an undetection state as indicated by the 2-second position in  FIG. 8 . Similarly, until the second wheel,  20  rotates in units of two steps and the rotation angle becomes 36°, as shown in  FIG. 14C  and  FIG. 14D , a part of the first light-blocking portion  21   d  corresponds to the detection position P. Thus, no light can he detected by the detector  13 , and the undetection state continues three times, as indicated by the 3-second position to 6-second position in  FIG. 6 . 
         [0088]    Then, if the second wheel  20  rotates by two steps and the rotation angle becomes 48°, as shown in  FIG. 14E , a part of the second elongated hole  21   b  of the first light transmission hole portion  21  of the second wheel  20  corresponds to the detection position P of the position detector  13 . Thus, light can be detected by the detector  13 , as indicated by the 8-second position in FIG  6 . Similarly, until the second wheel  20  rotates in units of two steps and the rotation angle becomes 168°, as shown in  FIG. 14F , a part of the second elongated hole  21   b  corresponds to the detection position P. Thus, light can continuously be detected by the detector  13 , as indicated by the 10-second position to 28-second position in  FIG. 6 . 
         [0089]    In this state, if the second wheel  20  further rotates by two steps and the rotation angle becomes 180°, as shown in  FIG. 14G , the second elongated hole  21   b  is displaced clockwise from the detection position P, and a part of the third light-blocking portion  21   f  corresponds to the detection position P. Thus, no light can be detected by the detector  13 , and there comes an undetection state as indicated by the 30-second position in  FIG. 6 . Then, as shown in  FIG. 14H , if the second wheel  20  rotates by two steps and the rotation angle becomes 192°, a part of the third elongated hole  21   c  of the first light transmission hole portion  21  of the second wheel  20  corresponds to the detection position P of the detector  13 . Thus, light can be detected by the detector  13 , as indicated by the 32-second position in  FIG. 6 . 
         [0090]    Then, until the second wheel  20  rotates in units of two steps and the rotation angle becomes 300°, as shown in  FIG. 14I , a part of the third elongated hole  21   c  corresponds to the detection position P of the detector  13 . Thus, light can continuously be detected by the position detector  13 , as indicated by the 34-second position to 50-second position in  FIG. 6 . Then, as shown in  FIG. 14J , if the third elongated hole  21   c  is displaced clockwise from the detection position P and a part of the second light-blocking portion  21   e  corresponds to the detection position P, no light can be detected by the detector  13  and there comes an undetection state as indicated by the 52-second position in  FIG. 6 . 
         [0091]    Similarly, until the second wheel  20  rotates in units of two steps and the rotation angle becomes 348°, as shown in  FIG. 14K  and  FIG. 14M , a part of the second light-blocking portion  21   e  corresponds to the detection position P. Thus, no light can be detected by the position detector  13 , and the undetection state continues four times, as indicated by the 54-second position to 58-second position in  FIG. 6 . If the second wheel  20  rotates by two steps in this state and the rotation angle becomes 360°, the first circular hole  21   a  corresponds to the detection position P of the position detector  13 , as shown in  FIG. 14A . Thus, light can be detected by the detector  13 , as indicated by the 0-second position in  FIG. 6 . 
         [0092]    As has been described above, in the state of  FIG. 14A , the light is detected by the position detector  13 . In the states of  FIG. 14B  to  FIG. 14D , the light cannot he detected by the detector  13  three times in succession. In the states shown in  FIG. 14E  and  FIG. 14F , the light can continuously be detected by the detector  13 . In the state of  FIG. 14G , no light can he detected by the detector  13 . In the states shown in  FIG. 14E  and  FIG. 14I , the light can continuously be detected by the detector  13 . In the states of  FIG. 14J  to  FIG. 14M , no light can be detected by the detector  13  four times in succession. 
         [0093]    The undetection state in which no light can be detected is the state of  FIG. 14B  to  FIG. 14D  and the state of  FIG. 14J  to  FIG. 14M . If attention is paid to these two states, in the case where light detection is executed in units of two steps, the undetection state continues three times in the former and the undetection state continues four times in the latter, and it is understood that the number of times of continuous undetection differs between the former and the latter. By counting the undetection state in which no light can be detected continuously, the standard position can be specified. 
         [0094]    Specifically, the light detection for the second wheel  20  is executed in units of two steps (two seconds). If the undetection state continues four times and light detection is successfully executed the next time, the position at which the light detection is executed is the standard position (0°). However, if the undetection state is counted from the state of  FIG. 14B , the undetection state continues three times until there comes the state of  FIG. 14D , and light can be detected in the following state of  FIG. 14E . In this case, since the undetection state does not continue four times, the position at which the light is detected is not the standard position. This is the basic second wheel position detection operation for detecting the standard position of the second wheel  20 . 
         [0095]    On the other hand, in the basic hand position detection operation for detecting the standard position of the minute wheel  25 , as shown in  FIG. 3  to  FIG. 5 , when the minute wheel  25  rotates by one step (6°), the intermediate wheel  23  rotates by 30°. When the minute wheel  25  rotates by 60 steps (360°: one rotation), the second light transmission hole portion  28  of the minute wheel  25  and the fourth light transmission hole portion  30  of the intermediate wheel  23  overlap at the detection position P. If light is detected by the position detector  13  at this time, the minute wheel  25  is at the standard position (0 minute). 
         [0096]    In the basic hand position detection operation for detecting the standard position of the hour wheel  27 , the third light transmission hole portion  29  of the hour wheel  27 , the second light transmission hole portion  28  of the minute wheel  25  and the fourth light transmission hole portion  30  overlap at the detection position P every hour on the hour, except the eleven o&#39;clock position. If light is detected by the detector  13  at this time, it is on the hour, except the eleven o&#39;clock position. At the eleven o&#39;clock position, no light is detected by the detector  13 . If light is detected by the detector  13  one hour after eleven o&#39;clock, the hour wheel  27  is at the standard position (0 hour) at the twelve o&#39;clock position. 
         [0097]    Next, referring to a block diagram of  FIG. 15 , the circuit structure of the present hand type wrist watch is described. 
         [0098]    This circuit structure includes a CPU (central processing unit)  35  which executes an overall circuit control; a ROM (read-only memory)  36  which stores predetermined programs; a RAM (random access memory)  37  which stores process data; an oscillator  38  which generates pulses for operating the CPU  35 ; and a frequency divider  39  which converts pulses, which are generated by the oscillator  38 , to proper frequencies (proper frequencies for operating the CPU  35 ). 
         [0099]    The circuit structure further includes timepiece movement  8  which rotates the hands (second hand  2 , minute hand  3  and hour hand  4 ), and a position detector  13  including a light emitting device  31  which emits light, and a light receiving device  32  which receives light from the light emitting device  31 . In this case, the CPU  35  reads out a program which is prestored in them ROM  36 , and cutouts predetermined driving pulses to the coils  17   a  and  22   a  of the first and second stepping motors  17  and  22  of the timepiece movement  8 . 
         [0100]    The circuit structure further includes, in addition to the above components, a power source  40  such as a solar panel  9  or a battery for supplying power; an antenna  41  which receives standard time radio waves; a detector  42  which executes a wave detection process of the received standard time radio waves; a lighting unit  43  which illuminates a time display; a lighting unit driver  44  for driving the lighting unit  43 ; a speaker  45  which produces sound; a buzzer circuit  46  for driving the speaker  45 ; and a plurality of button switches SW which selectively switch various modes. 
         [0101]    Next, referring to  FIG. 16 , a description is given of the basic second wheel position detecting process (the basic second hand position detecting process) for detecting the standard position of the second wheel  20  in the present hand type wrist watch. 
         [0102]    This basic second wheel position detecting process is a process of detecting the standard position (0°) of the second wheel  20 , that is, the position where the first circular hole  21   a  of the first light transmission hole portion  21  of the second wheel  20  coincides with the detection position P of the position detector  13 , as shown in  FIG. 14A . In this case, it is assumed that the second to fourth light transmission hole portions  28  to  30  of the minute wheel  25 , hour wheel  27  and intermediate wheel  23  of the second driving system  12  coincide with the detection position P of the position detector  13 , and remain at rest. 
         [0103]    If the second wheel position detecting process is started, the number of times of continuous undetection, which has previously been detected by the position detector  13 , is cleared, and an undetection flag is set at “0” (step S 1 ). Then, the second wheel  20  is moved by two steps (step S 2 ). The light emitting device  31  of the position detector  13  is made to emit light (step S 3 ), and it is detected whether the light from the light emitting device  31  is received by the light receiving device  32 , thereby determining whether light is detected by the position detector  13  or not (step S 4 ). 
         [0104]    At this time, in the case where any one of the first circular hole  21   a , second elongated hole  21   b  and third elongated hole  21   c  of the first light transmission hole portion  21  of the second wheel  20  coincides with the detection position P of the position detector  13  and the light is detected by the detector  13 , the second wheel  20  is moved in units of two steps until any one of the first to third light-blocking portions  21   d  to  21   f  of the second wheel  20  comes to correspond to the detection position P of the detector  13 , the light from the light emitting device  31  is not received by the light receiving device  32  and there comes an undetection state in which no light is detected by the detector  13 . 
         [0105]    In step S 4 , if any one of the first to third light-blocking portions  21   d  to  21   f  of the second wheel  20  corresponds to the detection position P of the detector  13  and there comes the undetection state in which no light is detected by the detector  13 , the undetection state is counted as the number of continuous undetection and the undetection flag is set at “1” (step S 5 ). It is then determined whether the undetection state has continued four times or not (step S 6 ). 
         [0106]    The reason for this is that if the undetection state continues four times, as shown in  FIG. 14J  to  FIG. 14M , and subsequently light is detected by the detector  13 , as shown in  FIG. 14A , the position at this time can be specified as the standard position of the second wheel  20 . For example, in the state from  FIG. 14B  to  FIG. 14D , since a part of the first light-blocking portion  21   d  of the second wheel  20  corresponds to the detection position P, the number of continuous undetection by the detector  13  is three. However, if the second wheel  20  subsequently rotates by two steps, a part of the second elongated hole  21   b  of the second wheel  20  corresponds to the detection position P and the light is detected by the detector  13 . At this time, the process returns to step S 2 , and the above-described operation is repeated. 
         [0107]    Similarly, in the state of  FIG. 14G , since the third light-blocking portion  21   f  of the second wheel  20  corresponds to the detection position P of the detector  13 , no light is detected by the detector  13 . However, if the second wheel  20  subsequently rotates by two steps, a part of the third elongated hole  21   c  of the second wheel  20  corresponds to the detection position P and light is detected by the detector  13 . Thus, at this time, too, the process returns to step S 2 , and the above-described operation is repeated. When the second wheel  20  rotates from the state of  FIG. 14J  to the state of  FIG. 14M , since parts of the second light-blocking portion  21   e  of the second wheel  20  continuously correspond to the detection position P, the undetection by the detector  13  continues four times. 
         [0108]    At this time, the second wheel  20  is rotated by two steps (step S 7 ), and the light emitting device  31  of the detector  13  is made to emit light (step S 8 ). To detect whether the light receiving device  32  receives the light of the light emitting device  31  or not, it is judged that whether there is the light detection of the detector  13  or not (step S 9 ). In step S 9 , if light is detected by the detector  13 , the first circular hole  21   a  of the first light transmission hole portion  21  of the second wheel  20  coincides with the detection position P, and it is determined that the second wheel  20  is at the standard position (0°) Thus, transition is made to the normal hand rotation, and the present process is finished. 
         [0109]    In this case, in step S 9 , it is assumed that the second to fourth light transmission hole portions  28  to  30  of the minute wheel  25 , hour wheel  27  and intermediate wheel  23  coincide with the detection position P of the detector  13 . Therefore, the light detection of the detector  13  is invariably performed. But, in a case if the second to fourth light transmission hole portions  28  to  30  of the minute wheel  25 , hour wheel  27  and intermediate wheel  23  do not coincide with the detection position P of the detector  13 , the light detection of the detector  13  is not performed, a time and minute hands position detection process will start. 
         [0110]    In the hour hand position detecting process, light detection by the detector  13  is executed in units of one step of the minute wheel  25 . If light is detected by the detector  13  when the minute wheel  25  has made a single rotation (360°: one minute), it is determined that the minute hand  3  is at the standard position. Besides, if light is detected by the detector  13  when the hour wheel  21  rotates by one hour (30°), except the eleven o&#39;clock position, it is determined that the hour hand  4  is on the hour. If no light is detected by the detector  13  at the eleven o&#39;clock position and subsequently light is detected by the detector  13 , it is determined that the hour hand  4  is at the standard position that is the twelve o&#39;clock position. 
         [0111]    As has been described above, according to the hand position detection apparatus, in the case of detecting the positions of the second wheel  20 , minute wheel  25  and hour wheel  27  by the position detector  13  that includes the light emitting device  31  and light receiving device  32 , the light from the light emitting device  31  can he received by the light receiving device  32  through the opening portion  14   a  of the main plate  4  and the light leak restriction hole  15   a  of the strain wheel bridge  15  when the first to fourth light transmission hole portions  21  and  28  to  30  of the second wheel  20 , minute wheel  25 , hour wheel  27  and intermediate wheel  23  have come to correspond to the detection position P on the optical axis  13   a.    
         [0112]    In this hand position detection apparatus, the detector  13  executes light detection in the state in which the second wheel  20  is rotated by a minimum angle (12°) at a timing of light detection by the detector  13 , for example, in units of two seconds (two steps), and the first circular hole  21   a  that is the standard hole is rotated and moved to a position away from the detection position P. In this case, even if the first circular hole  21   a  is not completely apart from the detection position P, leak light from the first circular hole  21   a  can he restricted by the light leak restriction hole  15   a  of the stain wheel bridge  15 . Therefore, erroneous detection due to leak light can be prevented at the time of light detection by the detector  13 , and thereby the rotational positions of the second wheel  20 , minute wheel  25  and hour wheel  27  can exactly be detected. 
         [0113]    Specifically, when the second wheel  20  rotates by a minimum angle in accordance with the timing (every two seconds) of light detection by the detector  13  and the first circular hole  21   a  that is the standard hole is rotated and moved to a position that is substantially completely away from the detection position P, even if displacement occurs in the rotational movement of the first circular hole  21   a  of the second wheel  20  due to the precision in fabrication of the second wheel  20  or back-lash, the light leak restriction hole  15   a  can prevent light leak due to such displacement. 
         [0114]    To be more specific, the light transmission region E 1  of the light leak restriction hole  15   a , through which light passes, is formed to be narrower by the maximum displacement amount R 1 , in consideration of the maximum displacement amount R 1  in rotational movement of the first circular hole  21   a  which is caused by the rotation of the second wheel  20 . Thus, when the second wheel  20  rotates by a minimum angle, even if the first circular hole  21   a  is not sufficiently rotated and moved due to the displacement amount R 1  and part of the light from the light emitting device  31  passes through the first circular hole  21   a , the leak light which has passed can surely be blocked by the light leak restriction hole  15   a  of the strain wheel bridge  15 . 
         [0115]    In this hand position detection apparatus, the light leak restriction hole  15   a  is a circular through-hole that is provided in the train wheel bridge  15 , which rotatably supports, together with the main plate  14 , the second wheel  20 , intermediate wheel  23  and minute wheel  25 , the light leak restriction hole  15   a  being provided at a position corresponding to the detection position P on the optical axis  13   a  that connects the light emitting device  31  and light receiving device  32 . Thus, there is no need to use a special member, and the existing structure can be used. Therefore, the optical axis  13   a , which connects the light emitting device  31  and light receiving device  32 , is not made longer, and the entire apparatus can be fabricated in compact size. 
         [0116]    In this hand position detection apparatus, the light receiving device  32  of the position detector  13  is disposed in the attachment recess portion  10   a  that is povided in the upper surface of the circuit board  10 , and the light receiving device  32  is covered with the mold resin  10   e . Even though the mold resin  10   e  protrudes to the upper side of the circuit board  10 , the protruding portion of the mold resin  10   e  is inserted in the receiving recess portion  15   b  which is provided in the lower surface of the train wheel bridge  15 . By this structure, too, the length of the optical axis  13   a , which connects the light emitting device  31  and light receiving device  32 , can be decreased, and the entire apparatus can be reduced in thickness. 
         [0117]    In this case, the light emitting device  31  of the detector  13  is disposed on the support substrate  33  that is disposed under the upper housing  6 , and is covered with the mold resin  33   d . The mold resin  33   d  is inserted in the opening portion  34   a , which is provided in the minute wheel hold plate  34  that is positioned thereunder. By this structure, too, the length of the optical axis  13   a , which connects the light emitting device  31  and light receiving device  32 , can be decreased, and the entire apparatus can be reduced in thickness. 
       Embodiment 2 
       [0118]    Next, referring to  FIG. 17  to  FIG. 20 , a description is given of Embodiment 2 of the hand type wrist watch to which the invention is applied. The same parts as those in the Embodiment 1 shown in  FIG. 1  to  FIG. 16  are denoted by like reference numerals, and a description thereof is omitted. 
         [0119]    In this wrist watch, in addition to the provision of the light leak restriction hole  15   a  of the strain to wheel bridge  15 , a light leak restriction hole  50  is also provided in the minute wheel hold plate  34  on the upper housing  6  side. In the other respects, the structure of Embodiment 2 is substantially the same as that of Embodiment 1. 
         [0120]    In this case, as shown in  FIG. 18  and  FIG. 20 , the support substrate  33  is disposed on the upper side of the minute wheel hold plate  34 . Like Embodiment 1, the light emitting device  31  is provided on the lower surface of the support substrate  33 . Specifically, like the Embodiment 1, a pair of electrodes  33   a  and  33   b  is provided on the lower surface of the support board  33 . An upper side electrode of the light emitting device  31  is disposed on and connected to one electrode  33   a , and a lower side electrode of the light emitting device  31  is connected to the other electrode  33   b  over a lead line  33   c . In this state, the light emitting device  31  is covered with a mold resin  33   d.    
         [0121]    A device receiving recess portion  51 , in which the mold resin  33   d  is inserted, is provided on the upper side of the minute wheel hold plate  34 , near which the light emitting device  31  is disposed, as shown in  FIG. 18  and  FIG. 20 . The minute wheel hold plate  34  at the device receiving recess portion  51  is provided with a light leak restriction hole  50  at a position corresponding to the detection position P of the detector  13 . The light leak restriction hole  50  is configured to correspond to the third light transmission hole portion  29  of the hour wheel  27  when the third light transmission hole portion  29  of the hour wheel  27 , which is disposed near the lower surface of the minute wheel hold plate  34 , has come to correspond to the detection position P. 
         [0122]    In this case, the size of a light transmission region E 3  of the light leak restriction hole  50  differs between the case in which the displacement amount R 1  of the first circular hole  21   a , which occurs due to the precision in fabrication of the second wheel  20  or back-lash, is greater than a displacement amount R 3  of the third light transmission hole portion  29 , which occurs due to the precision in fabrication of the hour wheel  27  or back-lash (R 1 &gt;R 3 ), and the case in which the displacement amount R 1  of the first circular hole  21   a  of the second wheel  20  is less than the displacement amount R 3  of the third light transmission hole portion  29  of the hour wheel  27  (R 1 &lt;R 3 ). 
         [0123]    For example, in the case where the displacement amount R 1  of the first circular hole  21   a  of the second wheel  20  is greater than the displacement amount R 3  of the third light transmission hole portion  29  of the hour wheel  27  (R 1 &gt;R 3 ), the light leak restriction hole  50  is formed in the same fashion as in Embodiment 1. Specifically, the light leak restriction hole  50  in this case (R 1 &gt;R 3 ) is configured in the following fashion. When the first circular hole  21   a  that is the standard hole of the second wheel  20  corresponds to the detection position P and the light receiving device  32  receives light from the light emitting device  31 , the second wheel  20  rotates by a minimum angle (12°) at every timing (2 seconds) of light detection by the position detector  13 , and the first circular hole  21   a  rotates to a position where the first circular hole  21   a  is completely apart, from the detection position P. The light leak restriction hole  50  in this case (R 1 &gt;R 3 ) is configured to prevent light leak from this rotated and moved first circular hole  21   a.    
         [0124]    To be more specific, as shown in  FIG. 12  and  FIG. 13 , the light transmission region E 3  of the light leak restriction hole  50 , through which light passes, is formed to be narrower by the maximum displacement amount R 1 , in consideration of the maximum displacement amount R 1  in rotational movement of the first circular hole  21   a  which is caused by the rotation of the second wheel  20 , when the second wheel  20  rotates by the minimum angle (12°) at every timing (2 seconds) of light detection by the detector  13  and the first circular hole  21   a  rotates to a position where the first circular hole  21   a  is apart from the detection position P. 
         [0125]    On the other hand, in the case where the displacement amount R 3  of the third light transmission hole portion  29  of the hour wheel  27  is greater than the displacement amount R 1  of the first circular hole  21   a  of the second wheel  20  (R 1 &lt; 53 ) the light leak restriction hole  50  is formed in accordance with the displacement amount  53  of the third light transmission hole portion  29  of the hour wheel  27 . Specifically, as shown in  FIG. 17  and  FIG. 18 , the light leak restriction hole  50  in this case (R 1 &lt;R 3 ) causes light from the light emitting device  31  to be radiated on the third light transmission hole portion  29 , when the third light transmission hole portion  29  of the hour wheel  27  has come to correspond to the optical axis  13   a  at the detection position P. 
         [0126]    In addition, as shown in  FIG. 19  and  FIG. 20 , the light leak restriction hole  50  in this case (R 1 &lt;R 3 ) is configured such that when the hour wheel  27  rotates by the minimum angle (30°) at every timing (one hour) of light detection by the detector  13  and the third light transmission hole portion  29  rotates to a position where the third light transmission hole portion  29  is completely apart from the detection position P, the light leak restriction hole  50  prevents light from the light emitting device  31  from being radiated on the third light transmission hole portion  29 , thus preventing light leak from the third light transmission hole portion  29 . 
         [0127]    To be more specific, as shown in  FIG. 20 , the light transmission region E 3  of the light leak restriction hole  50 , through which light passes, is formed to be narrower by the maximum displacement amount R 3 , in consideration of the maximum displacement amount R 3  in rotational movement of the third light transmission hole portion  29  which is caused by the rotation of the hour wheel  27 , when the hour wheel  27  rotates by the minimum angle (30°) at every timing (one hour) of light detection by the detector  13  and the third light transmission hole portion  29  rotates to a position where the third light transmission hole portion  29  is completely apart from the detection position P. 
         [0128]    According to this hand position detection apparatus, when the positions of the positions of the second wheel  20 , minute wheel  25  and hour wheel  27  are detected by the position detector  13  that includes the light from the light emitting device  31  and the light receiving device  32 , the light from the light emitting device  31  can be received by the light receiving device  32  through the light leak restriction hole  50  of the minute wheel hold plate  34 , the opening portion  14   a  of the main plate  14  and the light leak restriction hole  15   a  of the train wheel bridge  15  when the first to fourth light transmission hole portions  21  and  28  to  30  of the second wheel  20 , minute wheel  25 , hour wheel  27  and intermediate wheel  23  have come to correspond to the detection position P on the optical axis  13   a.    
         [0129]    In addition, according to this hand position detection apparatus, like Embodiment 1, in the case where the displacement amount R 1  of the first circular hole  21   a  of the second wheel  20  is greater than the displacement amount R 3  of the third light transmission hole portion  29  of the hour wheel  27  (R 1 &gt;R 3 ), when light detection is performed by the detector  13  in the state in which the second wheel  20  rotates by the minimum angle (12°) at the timing, e.g. every two seconds, of light detection by the detector  13  and the first circular hole  21   a  that is the standard hole is rotated and moved to a position that is substantially completely away from the detection position P, even if displacement occurs in the rotational movement of the first circular hole  21 , the light leak restriction hole  50  of the minute wheel hold plate  34 , together with the light leak restriction hole  15   a  of the train wheel bridge  15 , can prevent light leak from the first circular hole  21   a.    
         [0130]    Besides, in the case where the displacement amount R 3  of the third light transmission hole portion  29  of the hour wheel  27  is greater than the displacement amount R 1  of the first circular hole  21   a  of the second wheel  20  (R 1 &lt;R 3 ), when light detection is performed by the detector  13  in the state in which the hour wheel  27  rotates by the minimum angle (30°) at the timing, e.g. every one hour, of light detection by the detector  13  and the third light transmission hole portion  29  is rotated and moved to a position that is substantially completely away from the detection position P, even if displacement occurs in the rotational movement of the third light transmission hole portion  29 , the light leak restriction hole  50  of the minute wheel hold plate  34 , together with the light leak restriction hole  15   a  of the train wheel bridge  15 , can prevent light leak from the third light transmission hole portion  29 . 
         [0131]    Therefore, at the time of light detection by the detector  13 , light leak at the third light transmission hole portion  29  of the hour wheel  27  and the first circular hole  21   a  of the second wheel  20  can surely be prevented by the light leak restriction hole  50  of the minute wheel hold plate  34  and the light leak restriction hole  15   a  of the train wheel bridge  15 . Thereby, erroneous detection due to leak light can be prevented more surely than in Embodiment 1, and the rotational positions of the second wheel  20 , minute wheel  25  and hour wheel  27  can be detected more exactly than in the Embodiment 1. 
         [0132]    In Embodiment 2, the description has been given of the case in which the light leak restriction hole  15   a  is provided in the train wheel bridge  15 , and the light leak restriction hole  50  is provided in the minute wheel hold plate  34 . However, as shown in  FIG. 21 , for example, such a structure may be adopted that a light leak restriction hole  55  is also provided in the main plate  14 . The light leak restriction hole  55  of the main plate  14 , as shown in  FIG. 21 , causes the light, which has passed through the third light transmission hole portion  29 , to be radiated on the second light transmission hole portion  28  and fourth light transmission hole portion  30 , when the third light transmission hole portion  29  of the hour wheel  27 , the second light transmission hole portion  28  of the minute wheel  25  and the fourth light transmission hole portion  30  of the intermediate wheel  23  have come to correspond to the optical axis  13   a  at the detection position P. 
         [0133]    The size of a light transmission region E 2  of the light leak restriction hole  55  of the main plate  14  differs between the case in which the displacement amount R 1  of the first circular hole  21   a , which occurs due to the precision in fabrication of the second wheel  20  or back-lash, is greater than each of displacement amounts R 2  and R 4  of the second and fourth light transmission hole portions  28  and  30 , which occur due to the precision in fabrication of the minute wheel  25  and intermediate wheel  23  or back-lash (R 1 &gt;R 2 , R 4 ), and the case in which the displacement amount R 1  of the first circular hole  21   a  of the second wheel  20  is less than each of displacement amounts R 2  and R 4  of the second and fourth light transmission hole portions  28  and  30  of the minute wheel  25  and intermediate wheel  23  or back-lash (R 1 &lt;R 2 , R 4 ). 
         [0134]    For example, in the case where the displacement amount R 1  of the first circular hole  21   a  of the second wheel  20  is greater than each of displacement amounts R 2  and R 4  of the second and fourth light transmission hole portions  28  and  30  of the minute wheel  25  and intermediate wheel  23  (R 1 &gt;R 2 , R 4 ), the light leak restriction hole  55  is formed in the same fashion as in Embodiment 1. Specifically, the light leak restriction hole  55  in this case (R 1 &gt;R 2 , R 4 ) is configured to pass light from the light emitting device  31  when the first circular hole  21   a  that is the standard hole of the second wheel  20  has come to correspond to the detection position P, and to prevent light leak from the first circular hole  21   a  when the second wheel  20  rotates by the minimum angle (12°) at every timing (2 seconds) of light detection by the detector  13  and the first circular hole la rotates to a position where the first circular hole  21   a  is completely apart from the detection position P. 
         [0135]    To be more specific, the light transmission region E 2  of the light leak restriction hole  55 , through which light passes, is formed to he narrower by the maximum displacement amount R 1 , in consideration of the maximum displacement amount R 1  in rotational movement of the first circular hole  21   a  which is caused by the rotation of the second wheel  20 , when the second wheel  20  rotates by the minimum angle (12°) at every timing (2 seconds) of light detection by the detector  13  and the first circular hole  21   a  rotates to a position where the first circular hole  21   a  is apart from the detection position P, as shown in  FIG. 12  and  FIG. 13 . 
         [0136]    On the other hand, in the case where each of displacement amounts R 2  and R 4  of the second and fourth light transmission hole portions  28  and  30  of the minute wheel  25  and intermediate wheel  23  is greater than the displacement amount R 1  of the first circular hole  21   a  of the second wheel  20  (R 1 &lt;R 2 , R 4 ), the light leak restriction hole  55  is formed in accordance with the displacement amounts R 2  and R 4  of the second and fourth light transmission hole portions  28  and  30  of the minute wheel  25  and intermediate wheel  23 . Specifically, as shown in  FIG. 21 , the light leak restriction hole  55  in this case (R 1 &lt;R 2 , R 4 ) causes light from the light emitting device  31  to he radiated on the second and fourth light transmission hole portions  28  and  30 , when the second and fourth light transmission hole portions  28  and  30  of the minute wheel  25  and intermediate wheel  23  have come to correspond to the optical axis  13   a  at the detection position P. 
         [0137]    In addition, the light leak restriction hole  55  in this case (R 1 &lt;R 2 , R 4 ) is configured in the following fashion. As shown in  FIG. 21 , the minute wheel  25  rotates by the minimum angle (6°) at every timing (1 step: one minute) of light detection by the detector  13  and the intermediate wheel  23  rotates by the minimum angle (30°). The second light transmission hole portion  28  of the minute wheel  25  is rotated and moved to a position which is slightly displaced from the detection position P, and the fourth light transmission hole portion  30  of the intermediate wheel  23  is rotated and moved to a position which is completely away from the detection position P. The light leak restriction hole  55  in this case (R 1 &lt;R 2 , R 4 ) is configured such that even if light from the light emitting device  31  passes through the third light transmission hole portion  29  and second light transmission hole portion  28 , the light is blocked by the intermediate wheel  23 . 
         [0138]    In this case, the light transmission region E 2 , E 4  of the light leak restriction hole  55  of the main plate  14 , through which light passes, is formed to he narrower by the maximum displacement amounts R 2  and R 4 , in consideration of the maximum displacement amounts R 2  and R 4  in rotational movement or the second and fourth light transmission hole portions  28  and  30  which are caused by the rotations of the minute wheel  25  and intermediate wheel  23 , when the minute wheel  25  rotates by 60 steps (360°: one rotation) and the second light transmission hole portion  28  rotates and moves to a position near the detection position P and when the intermediate wheel  23  rotates by 30° at every 1 step and the fourth light transmission hole portion  30  rotates and moves to a position near the detection position P. 
         [0139]    This hand position detection apparatus is configured such that the light leak restriction hole  15   a  is provided in the train wheel bridge  15  and the light leak restriction hole  50  is provided in the minute wheel hold plate  34 , and moreover the light leak restriction hole  55  is provided in the main plate  14 . Thus, when the light detection is performed by the detector  13 , light leak at the third light transmission hole portion  29  of the hour wheel  27 , the second light transmission hole portion  28  of the minute wheel  25 , the fourth light transmission hole portion  30  of the intermediate wheel  23  and the first circular hole  21   a  of the second wheel  20  can more surely be prevented by the light leak restriction hole  55  of the main plate  14 , the light leak restriction hole  50  of the minute wheel hold plate  34  and the light leak restriction hole  15   a  of the train wheel bridge  15 . Thereby, erroneous detection cue to leak light can be prevented more surely than in Embodiment 2, and the rotational positions of the second wheel  20 , minute wheel  25  and hour wheel  27  can be detected more exactly than in Embodiment 2. 
         [0140]    In the above-described Embodiment 2 and modification thereof, the light leak restriction hole  50  is provided in the minute wheel hold plate  34 , and the light leak restriction hole  55  is provided in the main plate  14 , in addition to the provision of the light leak restriction hole  15   a  in the train wheel bridge  15 . Alternatively, such a structure may be adopted that the light leak restriction hole is provided in any one of the train wheel bridge  15 , minute wheel hold plate  34  and main plate  14 . With this structure, too, the same advantageous effect as in the Embodiment 1 can be obtained. 
       Embodiment 3 
       [0141]    Next, referring to  FIG. 22  to  FIG. 23 , a description is given of Embodiment 3 of the hand type wrist watch to which the invention is applied. The same parts as those in Embodiment 1 shown in  FIG. 1  to  FIG. 16  are denoted by like reference numerals, and a description thereof is omitted. 
         [0142]    In this wrist watch, a train wheel bridge  60  is formed of a transparent synthetic resin, and a light leak restriction member  61  is provided on the upper surface of the train wheel bridge  60 . In the other respects, the structure of Embodiment 3 is the same as that of the Embodiment 1. 
         [0143]    Specifically, the light leak restriction member  61  is configured such that a light-blocking layer  62  is provided on the upper surface of the transparent train wheel bridge  60 , except a predetermined region, that is, except the light transmission region E 1 . The light-blocking layer  62  is a film which blocks light, such as a print layer, an evaporation-deposition layer, a metal plating layer or an opaque resin sheet. Like Embodiment 1, the light leak restriction member  61  is provided with the light transmission region E 1  at a position corresponding to the detection position P of the detector  13 . The light transmission region E 1  of the light leak restriction member  61 , through which light passes, is narrowed by a maximum displacement amount R 1 , in consideration of the maximum displacement amount R 1  in rotational movement of the first circular hole  21   a  which is caused by the rotation of the second wheel  20  when the second wheel  20  rotates by the minimum angle (12°) and the first circular hole  21   a  rotates to a position where the first circular hole  21   a  is completely apart from the detection position P. 
         [0144]    Like Embodiment 1, in this hand position detection apparatus, too, when the second wheel  20  rotates by the minimum angle and the first circular hole  21   a  that is the standard hole is rotated and moved to a position that is substantially completely apart from the detection position P, even if displacement occurs in the rotational movement of the first circular hole  21   a  of the second wheel  20  due to the precision in fabrication of the second wheel  20  or back-lash, the light leak restriction member  61  can prevent light leak due to such displacement. Therefore, erroneous detection due to leak light can he prevented at the time of light detection by the detector  13 , and the rotational positions of the second wheel  20 , minute wheel  25  and hour wheel  27  can exactly be detected. 
         [0145]    To be more specific, the light transmission region E 1  of the light leak restriction member  61 , through which light passes, is formed to be narrower by the maximum displacement amount R 1 , in consideration of the maximum displacement amount R 1  in rotational movement of the first circular hole  21   a  which is caused by the rotation of the second wheel  20 . Thus, when the second wheel  20  rotates by the minimum angle, even if displacement occurs in the rotational movement of the first circular hole  21   a  and part of the light from the light emitting device  31  passes through the first circular hole  21   a , the leak light which has passed can surely be blocked by the light-blocking layer  62  of the light leak restriction member  61  of the strain wheel bridge  15 . 
         [0146]    In the above-described Embodiment 3, the description has been given of the case in which the train wheel bridge  60  is formed of a transparent synthetic resin and the light leak restriction member  61 , which is formed of the light-blocking layer  62 , is provided on the upper surface of the train wheel bridge  60 . Alternatively, for example, such a structure may be adopted that the minute wheel hold plate  34  and main plate  14  are formed of a transparent synthetic resin, and a light leak restriction member that is formed of a light-blocking layer is provided on one surface of each of the minute wheel hold plate  34  and main plate  14 . 
         [0147]    In the above-described Embodiments 1 to 3 and modifications thereof, the description has been given of the case in which the light leak restriction hole  55 ,  15   a ,  50  or the light leak restriction member  61  is provided in the main plate  14 , train wheel bridge  15  and minute wheel hold plate  34 , which are disposed between the light emitting device  31  and light receiving device  32  of the detector  13 . Alternatively, such a structure may be adopted that the surface of the mold resin  33   d  of the light emitting device  31  or the surface of the mold resin  10   e  of the light receiving device  32  is provided with a light leak restriction member  61  which is provided with a light-blocking layer  62 , except a predetermined region (light transmission region) thereof. 
         [0148]    Furthermore, in the above-described Embodiments 1 to 3 and modifications thereof, the description has been given of the case in which the first light transmission hole portion  21  of the second wheel  20  is provided with the second and third elongated holes  21   b  and  21   c  on both sides of the first circular hole  21   a  that is the standard hole. Alternatively, as in a modification shown in  FIG. 24 , for example, such a structure may be adopted that the second elongated hole  21   b  of the first light transmission hole portion  21  of the second wheel  20  is divided into two elongated holes  65   a  and  65   b , and the third elongated hole  21   c  is divided into two elongated holes  66   a  and  66   b.    
         [0149]    In this case, a fifth light-blocking portion  67  is provided between the two elongated holes  65   a  and  65   b  of the second elongated hole  21   b , and a sixth light-blocking portion  68  is provided between the two elongated holes  66   a  and  66   b  of the third elongated hole  21   c . In the case where this second wheel  20  is applied to the hand position detection apparatus, substantially the same advantageous effect as in the Embodiments 1 to 3 and modifications thereof can be obtained. 
         [0150]    In the above-described Embodiments 1 to 3 and modifications thereof, the invention is applied to the hand type wrist watch. However, the invention is not necessarily applied to the wrist watch, but is applicable to various hand type timepieces, such as a traveling clock, an alarm clock, a desk clock, and a wall clock. 
         [0151]    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.