Abstract:
An electronic apparatus has a motor and a disc-shaped readable member rotationally driven by the motor and having at least one first slit therein and an optical amount adjusting slit having an arcuate shape with a radius of curvature identical to that of a rotational path of the readable member. A detecting device detects rotation of the readable member and has a light emitting element and a light receiving element sandwiching therebetween the readable member so that light is projected through the at least one first slit once for each revolution of the readable member.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an electronic apparatus for detecting a position of a movable object member of, for example, an indicator, a mirror or the like.  
         [0003]     2. Description of the Related Art  
         [0004]     In recent years, in electronic apparatus, positioning control of a movable object member is an important technology and higher positioning accuracy is requested. As a method of carrying out positioning control of a movable object member, there is generally adopted a method of detecting position information of a moving member moved by drive force of an actuator and controlling movement of the moving member by feedback control based on the position information to thereby position the movable object member moving in cooperation with the moving member.  
         [0005]     Further, in detecting a position of a moving member, for example, there are used an optical type encoder of an absolute type and an encoder of an incremental type. According to the optical type encoder of the absolute type, absolute position information is provided by a rotational position. Meanwhile, as shown by  FIG. 2 , the encoder of the incremental type is provided with a member to be read  2  having two rows of slits  2   a  at equal intervals for detecting a change in a rotational amount and having a slit  2   b  constituting a reference position for detecting absolute position information. Two signal shaving phases which differ by 90 degree are provided by way of the slits  2   a  and therefore, a single signal multiplied by four is provided therefrom to thereby achieve a resolution multiplied by four.  
         [0006]      FIG. 3  shows an example of a structure for providing a rotational output by using an encoder of an incremental type. The structure is constituted by an actuator  16  which is a DC motor, a rotating shaft  100  for transmitting the rotational output of the actuator  16 , detecting means having a pair of a light emitting element  8   a  and a light receiving element  8   b , a member to be read  2  only the center of which is fixed to one side of the rotating shaft  100  by screwing or striking and an indicator  27  fixed to other side of the rotating shaft  100  by screwing or striking and operating as a movable object member. An absolute position of the indicator  27  is controlled based on a reference signal of the slit  2   b  constituting a reference of the member to be read  2 .  
         [0007]     However, according to the conventional electronic apparatus having position detecting apparatus, when the member to be read and the movable object member are attached to the rotating shaft, the rotating shaft is fixed to a hole portion of the member to be read by screwing or striking. Accordingly, there poses a problem that although positions of attaching the both members are determined in a radius direction, by the rotating shaft as a guide, a positional relationship of the slit constituting the reference of the member to be read and the movable object member is shifted in a peripheral direction. When the positional relationship is shifted, it is difficult to detect the absolute position information of the movable object member, as a result, regardless of the fact that the moving member is accurately positioned based on-the information of the member to be read, the movable object member is positioned to a position different from a desired position. An amount of the shift of the positional relationship between the slit constituting the reference of the member to be read and the movable object member, is dispersed also among products.  
         [0008]     In order to eliminate the shift of the positional relationship between the slit constituting the reference of the member to be read and the movable object member in the peripheral direction, the positional relationship between the slit constituting the reference of the member to be read and the movable object member must be adjusted. The adjustment is carried out by taking time by a skilled worker and therefore, it is difficult to adjust the positional relationship simply. Therefore, a number of steps of adjusting and the like is increased and fabrication cost is also increased. Therefore, the method is not a method suitable for mass production.  
       SUMMARY OF THE INVENTION  
       [0009]     Hence, it is an object of the invention to eliminate a deviation in a positional relationship in a peripheral direction between a slit constituting a reference of a member to be read and a movable object member when the member to be read and the movable object member are attached to a moving member of, for example, a rotating shaft or the like, dispense with adjustment of the shift in the positional relationship therebetween, promote mass production performance and promote positional accuracy of the movable object member.  
         [0010]     In order to resolve the above-described problem, according to an aspect of the invention, there is provided an electronic apparatus having a position detecting apparatus, the electronic apparatus comprising a movable object member having various functions, an actuator having a moving member moved to drive the movable object member, a member to be read for providing information with regard to a state of moving the movable object member, and a guide member for fixing the movable object member, the actuator and the member to be read. The aspect of the invention is characterized in that the member to be read and the movable object member are attached by the same guide member, or the member to be read and the movable object member are integrally formed such that a positional relationship between a slit constituting a reference of the member to be read and the movable object member is not shifted.  
         [0011]     By fixing the movable object member and the member to be read by the guide member, the shift in the positional relationship between the slit constituting the reference of the member to be read and the movable object member is eliminated, further, adjustment of positions of attaching the both members is dispensed with, mass production performance is promoted and the dispersion in the positional relationship between the slit constituting the reference of the member to be read and the movable object member can be reduced. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is an outline sectional view for explaining a constitution of an electronic apparatus according to Embodiment 1 of the invention;  
         [0013]      FIG. 2  is an outline top view for explaining a member to be read according to a conventional example;  
         [0014]      FIG. 3  is an outline sectional view for explaining a constitution of an electronic apparatus having a moving member, a member to be read and a movable object member according to a conventional example;  
         [0015]      FIG. 4  is a block diagram for explaining a constitution of an electronic apparatus according to the invention;  
         [0016]      FIG. 5  is an outline top view for explaining a member to be read of the electronic apparatus according to Embodiment 1 of the invention;  
         [0017]      FIG. 6  is an outline sectional view for explaining a constitution of an electronic apparatus according to Embodiment 2 of the invention;  
         [0018]      FIG. 7  is an outline top view for explaining a constitution of an electronic apparatus according to Embodiment 3 of the invention;  
         [0019]      FIG. 8  illustrates an outline top view and an outline sectional view for explaining a constitution of an electronic apparatus according to Embodiment 4 of the invention;  
         [0020]      FIG. 9  illustrates an outline top view and an outline sectional view for explaining a constitution of an electronic apparatus according to Embodiment 5 of the invention;  
         [0021]      FIG. 10  is an outline top view for explaining a constitution of an electronic apparatus according to Embodiment 6 of the invention;  
         [0022]      FIG. 11  is an outline sectional view for explaining a constitution of an electronic apparatus according to Embodiment 7 of the invention; and  
         [0023]      FIG. 12  is an outline top view for explaining the constitution of the electronic apparatus according to Embodiment 7 of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     A detailed explanation will be given of embodiments to which the invention is applied as follows.  
       Embodiment 1  
       [0025]      FIG. 4  shows a block diagram of an electronic apparatus according to the invention. A control circuit  30  outputs a control signal for instructing start, stop, regular rotation or reverse rotation of an actuator  16  to a drive circuit  31 . The drive circuit  31  receives the control signal and inputs a drive signal based on the control signal to the actuator  16 . The actuator  16  is driven by the drive signal and provides a moving member  60  with movement such as rotation or reciprocal movement. A member to be read  2  is similarly rotated or reciprocally moved in cooperation with the movement of the moving member  60 . Detecting means  8  detects the rotation or the reciprocal movement of the member to be read  2 . Further, the detecting means  8  is provided with a light emitting element and a light receiving element such as phototransistors. The detecting means  8  outputs a detected signal based on a state of the rotation or the reciprocal movement of the member to be read  2  by receiving information emitted from the light emitting element by the light receiving element. A counter circuit  32  calculates a moving amount based on the detected signal detected by the detecting means  8  and outputs the moving amount to the control circuit  30 . The control circuit  30  compares the detected signal with a designated moving amount and outputs the control signal such that the moving member  60  gets proximate to the desired position.  
         [0026]      FIG. 1  is an outline sectional view showing a constitution of an electronic apparatus according to Embodiment 1 of the invention, particularly explaining, in details, the actuator  16 , the moving member  60 , the member to be read  2  and the detecting means  8  shown by block diagram at  FIG. 4 . Further,  FIG. 5  is an outline top view of the member to be read  2  used in Embodiment 1. The actuator  16  is firmly fixed to an upper face of a support plate  52  by a screw. Further, the actuator  16  may be adhered or welded thereto so far as the actuator  16  can be fixed thereto firmly. Although various motors are utilized for the actuator  16 , here, an explanation will be given of a case of using an ultrasonic motor.  
         [0027]     In the ultrasonic motor  16 , a vibrator  12  is fitted to a center shaft  14 . A piezoelectric element  11  is adhered to a lower face of the vibrator  12 . Meanwhile, a plurality of projections  13  are provided to an upper face of the vibrator  12 . A rotor  51  is arranged on an upper side of the vibrator  12  to be brought into contact with the projections  13 . A bearing is provided at center of the rotor  51  and the bearing is inserted with the center shaft  14 . By constituting in this way, oscillation of the vibrator  12  is transmitted to the projections  13  and the rotor  51  is rotated with the center shaft  14  as center of rotation. An upper portion of the rotor  51  is pressed by a pressurizing spring  15  such that the rotor  51  is brought into contact with the projections  13  with constant pressing force. According to the ultrasonic motor  16 , a drive signal is applied to the piezoelectric element  11  to thereby oscillate the vibrator  12 , the oscillation is converted into rotational movement by friction between the projections  13  and the rotor  51  to thereby rotate the rotor  51 . Further, there is used the principle of the ultrasonic motor  16  disclosed in, for example, Japanese Patent Laid-Open No. 170772/1995.  
         [0028]     Two pieces of guide members  4  are fitted to the rotor  51  operating as the moving member  60  moved to rotate at locations of the upper face deviated from the center of rotation. The guide members  4  are rotated along with the rotor  51  and therefore, it is preferable to take an equal angular interval therebetween at equal distances from the center. There is provided a stepped difference portion lower than the central portion by one step at the upper face of the rotor  51 . The member to be read  2  is arranged at the stepped difference portion. At this occasion, guide holes  2   c  are perforated such that the guide member  4  can be fitted to the member to be read  2 . The member to be read  2  is perforated with slits  2   a  at equal intervals to constitute equal angles in view from the center of rotation as shown by, for example,  FIG. 5 . Further, the member to be read  2  is also perforated with a slit  2   b  of a reference position for indicating one turn. As shown by  FIG. 1 , for example, the guide holes  2   c  of the member to be read  2  are fitted to the guide member  4 , further, the guide members  4  is fitted to a movable object member  6  fixed to the rotor  51  and rotating along with the rotor  51 . As the movable object member  6 , there is, for example, a mirror or the like. In the following, an explanation will mainly be given of a case of using a mirror. The mirror  6  is also provided with guide holes  6   a  similar to those of the member to be read  2  and the guide holes  6   a  of the mirror  6  are fitted to the guide members  4 . At this occasion, the guide holes  2   c  and  6   a  are provided to the member to be read  2  and the mirror  6  such that the slit  2   b  constituting the reference of the member to be read  2  and the mirror  6  are brought into a predetermined positional relationship.  
         [0029]     The detecting means  8  for detecting rotation is provided with a light emitting element  8   a  and a light receiving element  8   b . The light emitting element  8   a  and the light receiving element  8   b  are provided to be opposed to each other to sandwich the member to be read  2  from above and from below. The guide members  4  determine positions in the radius direction and positions in the peripheral direction of the member to be read  2  and the mirror  6  relative to the rotor  51  to thereby prevent a shift in the positional relationship between the slit  2   b  constituting the reference of the member to be read  2  and the mirror  6  when the member to be read  2  and the mirror  6  are attached. Therefore, in an assembled state, operational accuracy of the mirror  6  is promoted and adjustment of positions of attaching the member to be read  2  and the mirror  6  is dispensed with. The guide members  4  are deviated from the center of rotation in order to reduce play angle produced by dimensional tolerance between the guide member  4  and the guide holes  2   c  and the  6   a . Therefore, the operational accuracy of the mirror  6  can further be promoted.  
         [0030]     Further, by using the ultrasonic motor  16  in the method of driving the above-described structure, there is realized the electronic apparatus having the ultrasonic motor operating the mirror  6  with high accuracy. By using the ultrasonic motor, there can be realized the electronic apparatus excellent in positional accuracy and response and saving power.  
       Embodiment 2  
       [0031]     An explanation will be given of Embodiment 2 in reference to  FIG. 6 . Embodiment 2 is characterized in that a rotating shaft  5   a  operating as a moving member, a member to be read  5   b  and an indicator  5   c  constituting a movable object member are integrally formed.  
         [0032]     In  FIG. 6 , the rotating shaft  5   a  operating as a moving member is molded integrally with the indicator  5   c  constituting the movable object member and the member to be read  5   b  by injection molding of plastic. Although a lower portion of the rotating shaft  5   a  is omitted, the lower portion may be constructed by an actuator such as an ultrasonic motor for driving to rotate the rotating shaft  5   a  or a power transmission mechanism by gears for transmitting power of a drive source. As detecting means  8  for detecting rotation, the light emitting element  8   a  and the light receiving element  8   b  are provided to sandwich the member to be read  5   b.    
         [0033]     According to the above-described constitution, assembling of the member to be read  5   b  and the indicator  5   c  is dispensed with and a shift in a positional relationship of a slit constituting a reference of the member to be read  5   b  and the indicator  5   c  can be prevented. Therefore, adjustment of positions of attaching the member to be read  5   b  and the indicator  5   c  is dispensed with. Further, in this case, owing to the structure in which the member to be read  5   b , the indicator  5   c  and the rotating shaft  5   a  are integrally formed, a total of the structure can be downsized, further, assembling steps can be saved.  
       Embodiment 3  
       [0034]     An explanation will be given of Embodiment 3 in reference to  FIG. 7 .  
         [0035]     Embodiment 3 of  FIG. 7  is constituted by the motor  16  constituting a drive source, a rotating shaft  9  of the motor constituting a moving member, the member to be read  2  attached to the rotating shaft  9 , an indicator  27  constituting a movable object member attached to the rotating shaft  9 , a guide member  9   a  formed integrally with the rotating shaft  9  and the detecting means  8  having the light emitting element  8   a  and the light receiving element  8   b  provided to sandwich the member to be read  2 .  
         [0036]     According to the rotating shaft  9 , a motor side thereof is provided with a section in a circular shape and an end portion side thereof is provided with a section in a noncircular shape. The noncircular shape may be any shape so far as the shape is not a circular shape. Here, there is constituted a structure in which the shape is constituted by a semicircular shape, a portion of the rotating shaft  9  is worked by machining or the like, a portion of the semicircular shape operates as the guide member  9   a  and the guide member  9   a  is formed integrally with the rotating shaft  9 . The member to be read  2  and the indicator  27  are provided with guide holes  2   c  and  27   a  having shapes similar to the noncircular shape. There is constituted a structure in which the guide member  9   a  is driven into the guide hole  2   c  of the member to be read  2  and the guide member  9   a  is driven into the guide hole  27   a  of the indicator  27 .  
         [0037]     According to Embodiment 3 having the above-described constitution, when both of the member to be read  2  and the indicator  27  are attached to the rotating shaft  9 , the guide member  9   a  integral with the rotating shaft  9  constitutes a guide in the peripheral direction to thereby prevent a shift in a positional relationship between the slit  2   b  constituting the reference of the member to be read  2  and the indicator  27 . Therefore, adjustment of positions of attaching the member to be read  2  and the indicator  27  is dispensed with and operational accuracy of the indicator  27  is promoted.  
         [0038]     Further, according to Embodiment 3, it is not necessary to provide two pieces of the guide members as in Embodiment 1, the guide member  9   a  is integral with the rotating shaft  9  and therefore, a number of parts can be reduced.  
       Embodiment 4  
       [0039]     An explanation will be given of Embodiment 4 in reference to  FIG. 8 .  
         [0040]     Embodiment of  FIG. 8  is constituted by the motor  16  constituting a drive source, the rotating shaft  100  of the motor  16  constituting the moving member, the member to be read  2  attached to the rotating shaft  100 , the indicator  27  constituting the movable object member attached to the member to be read  2 , a guide member  2   e  formed integrally with the member to be read  2  and the light emitting element  8   a  and the light receiving element  8   b  provided to sandwich the member to be read  2 .  
         [0041]     The member to be read  2  is provided with a recess portion  2   d  at a rotational center portion on a lower face side thereof and the rotating shaft  100  is fitted to the recess portion  2   d  of the member to be read  2 . The guide member  2   e  is integrally formed with the rotational center portion on an upper face side of the member to be read  2 . The guide member  2   e  is provided with a section in a noncircular shape, which is a semicircular shape in this case. The indicator  27  is provided with a guide hole  27   a  having a shape similar to that of the section in the noncircular shape. The indicator  27  is fixed by fitting the guide hole  27   a  to the guide member  2   e.    
         [0042]     According to Embodiment 4 having the above-described constitution, when the member to be read  2  and the indicator  27  are attached to the rotating shaft  100 , the guide member  2   e  integral with the member to be read  2 , constitutes a guide in the peripheral direction to thereby prevent a shift in a positional relationship between a slit constituting the reference of the member to be read  2  and the indicator  27 . Therefore, adjustment of positions of attaching the member to be read  2  and the indicator  27  is dispensed with and operational accuracy of the indicator  27  is promoted.  
       Embodiment 5  
       [0043]      FIG. 9  shows an optical filter with an ultrasonic motor as a drive source.  
         [0044]     The ultrasonic motor is constituted by the vibrator  12  constituted by adhering the piezoelectric element  11  to a lower face of an elastic member, the projections  13  provided at the upper face of the vibrator  12 , the rotor  51  arranged to be brought into contact with the projection  13 , the center shaft  14  fixed with the vibrator  12  for enabling to rotate the rotor  51  and the pressurizing spring  15  for pressing the rotor  51 . According to the ultrasonic motor, a drive signal is applied to the piezoelectric element  11  to thereby oscillate the vibrator  12 , the oscillation is converted into rotational movement by friction between the projections  13  and the rotor  51  to thereby rotate the rotor  51 . In this case, the rotor  51  operates as the moving member.  
         [0045]     In this case, the movable object member is constituted by an eccentric cam  23  and guide members  23   a  are integrally formed therewith at locations deviated from the center of rotation of the eccentric cam  23 . The guide members  23   a  penetrate the guide holes  2   c  of the member to be read  2  and are driven into the rotor  51 . An urge spring  18  is connected to one end face of a straight moving base  19  and urges the straight moving base  19  to a side of the eccentric cam  23  in contact with other end face of the straight moving base  19 . The straight moving base  19  is provided with a multilayered film filter  20 . An input port  21  of an optical fiber and an output port  22  of an optical fiber are arranged to sandwich the multilayered film filter  20 .  
         [0046]     Further, there is provided the detecting means  8  having the light emitting element  8   a  and the light receiving element  8   b  provided to be opposed to each other to sandwich the member to be read  2 .  
         [0047]     In  FIG. 9 , when the eccentric cam  23  is rotated in one direction by the ultrasonic motor, the straight moving base  19  is moved to the right side by the urge force of the urge spring  18 , thereafter, when the ultrasonic motor is rotated in other direction, the eccentric cam  23  is also rotated in the other direction and the straight moving base  19  is pressed by the eccentric cam  23  and is moved to the left side by overcoming the urge force of the urge spring  18 . Thereby, the multilayered film filter  20  is moved in the left and right direction to thereby control states of wavelength, intensity, presence or absence or the like of light outputted from the input port  21  of the optical fiber and transmitted through the multilayered film filter  20 .  
         [0048]     In this case, the guide members  23   a  are integrally formed with the eccentric cam and therefore, a number of parts can be reduced and the guide members  23   a  prevent a shift in a positional relationship between the member to be read  2  and the eccentric cam  23 . Therefore, adjustment of positions of attaching the member to be read  2  and the eccentric cam  23  is dispensed with and the operational accuracy of the eccentric cam  23  and also operational accuracy of the multilayered film filter  20  are promoted.  
       Embodiment 6  
       [0049]     An explanation will be given of Embodiment 6 in reference to  FIG. 10 .  FIG. 10  shows a constitution of a variable attenuator for adjusting an optical amount of light, which is constituted by the rotating shaft  100  rotated by drive force of the actuator  16  and constituting a moving member, a member to be read  40   a  fitted to the rotating shaft  100 , slits  40   aa  at equal intervals as well as a slit  40   ab  constituting a reference formed by an etching process, an optical amount adjusting slit  40   b  constituting a movable object member formed integrally with the member to be read  40   a  by the etching process, an optical fiber input port  21  and an optical fiber output port  22  provided to sandwich the optical amount adjusting slit  40   b  and the detecting means  8  having the light emitting element  8   a  and the light receiving element  8   b  provided to sandwich the member to be read  2 .  
         [0050]     The optical amount adjusting slit  40   b  is provided on a circle concentric with the center of rotation and, in this case, formed in a shape in which a width in the radius direction is slenderized toward one side in the peripheral direction. An optical signal outputted from the optical fiber input port  21  is inputted to the optical fiber output port  22  via the optical amount adjusting slit  40   b.    
         [0051]     When the rotating shaft  100  is driven by the actuator  16 , the member to be read  40   a  and the optical amount adjusting slit  40   b  are also rotated. The width of the optical slit  40   b  between the optical fibers differ depending on the position of the optical amount adjusting slit  40   b . Therefore, the optical amount of the optical signal transmitting through the optical amount adjusting slit  40   b  can be changed by the rotational angle. The position of the rotating shaft  100  is detected by the detecting means  8  having the light emitting element  8   a  and the light receiving element  8   b  provided to be opposed to each other to sandwich the member to be read  40   a . There is constituted a variable attenuator for adjusting the optical amount by controlling the position.  
         [0052]     The member to be read  40   a  and the optical amount adjusting slit  40   b  are integrally formed and therefore, a shift in a positional relationship between the slit  40   a  b constituting the reference of the member to be read  40   a  and the optical amount adjusting slit  40   b  can be prevented. Therefore, adjustment of positions of attaching the member to be read  40   a  and the optical amount adjusting slit  40   b  is dispensed with and the optical amount adjusting accuracy is promoted.  
         [0053]     Although in this case, the optical amount adjusting slit  40   b  is provided continuously in the peripheral direction, for example, a plurality of circular slits having different diameters may continuously be provided in the peripheral direction.  
       Embodiment 7  
       [0054]     An explanation will be given of Embodiment 7 in reference to  FIG. 11  and  FIG. 12 .  
         [0055]      FIG. 11  is an outline sectional view for explaining a constitution in which drive force of the ultrasonic motor is transmitted to a rotating shaft  41   a  constituting a movable member via a transmission mechanism  25  to thereby move the indicator  27  constituting the movable object member moved in cooperation with the rotating shaft  41   a.    
         [0056]     The ultrasonic motor is constituted by the vibrator  12  constituted by adhering the piezoelectric element  11  to a lower face of an elastic member, the projections  13  provided at an upper face of the vibrator  12 , the rotor  51  arranged to be brought into contact with the projections  13 , the center shaft  14  fixed to the vibrator  12  for enabling to rotate the rotor  51  and the pressurizing spring  15  for pressing the rotor  51 . According to the ultrasonic motor, the vibrator  12  is oscillated by applying a drive signal to the piezoelectric element  11  and the oscillation is converted into rotational movement by friction between the projections  13  and the rotor  51  to thereby rotate the rotor  51 .  
         [0057]     In this case, the rotational force of the rotor  51  rotates the rotating shaft  41   a  via the power transmission mechanism  25  such as gears. The rotating shaft  41   a  is attached with the indicator  27  constituting the movable object member. A portion of the rotating shaft  41   a  attached with the indicator  27 , operates as a guide member  41   c  in a noncircular sectional shape similar to that of the rotating shaft shown in Embodiment 3 and is fitted with the indicator  27  having the guide hole  27   a  having a similar shape. Further, a gear  41   d  for directly transmitting rotational force of the power transmission mechanism  25  to the rotating shaft  41   a , is integrally formed with the rotating shaft  41   a . Rotation is detected by the light emitting element  8   a , the light receiving element  8   b  and a member to be read  41   b  integrally formed with the gear  41   d  for directly transmitting the rotational force of the power transmission mechanism  25  to the rotating shaft  45   a.    
         [0058]      FIG. 12  is an outline top view of the member to be read  41   b  integrally formed with the gear  41   d  for directly transmitting the rotational force of the power transmission mechanism  25  to the rotating shaft  45   a  and the rotating shaft  41   a . An outer periphery of a circular disk is inscribed with teeth and on its inner side, there are provided slits  41   ba  at equal intervals for providing rotational angle information and a slit  41   bb  constituting a reference for providing an absolute position. The rotating shaft  41   a  is integrally formed with the center of rotation of the member to be read  41   b  and the guide member  41   c  is integrally formed with the rotating shaft  41   a.    
         [0059]     The gear  41   d  for directly transmitting the rotational force of the power transmission mechanism  25  to the rotating shaft  41   a , the member to be read  41   b , the rotating shaft  41   a  and the guide member  41   c  are integrally formed and therefore, small-sized formation can be achieved and a reduction in cost can be achieved by reducing assembling steps. Further, the guide member  41   c  formed integrally with the rotating shaft  41   a  prevents a shift in a positional relationship between the indicator  27  and the slit  41   bb  constituting the reference of the member to be read  41   b . Therefore, promotion of operational accuracy of the indicator  27  can be achieved and adjustment of positions of attaching the slit  41   bb  constituting the reference of the member to be read  41   b  and the indicator  27  is dispensed with.  
         [0060]     Further, the kind of the encoder is not limited to the above-described incremental type but may be the absolute type and the principle is not limited to the optical type.  
         [0061]     As described above, according to the invention, by fixing the member to be read by the guide members, the shift in the positional relationship between the slit constituting the reference of the member to be read and the movable object member can be eliminated. Thereby, the operational accuracy of the movable object member is promoted, further, the step for adjusting the shift in the positional relationship between the slit constituting the reference of the member to be read and the movable object member, is dispensed with and mass production performance can be promoted. Further, also with regard to the positional relationship between the slit constituting the reference of the member to be read and the movable object member, the dispersion can be reduced.