Abstract:
A turntable provided in the carousel changer has a plurality of trays provided around its rotating shaft. The turntable is provided with an annular rib including a plurality of recessed portions and a plurality of raised portions. A sensor is provided to have the rib passed therethrough and detects recessed portions and raised portions in the rib as the turntable is driven by a motor to rotate. The controller receives a detection result by the sensor and controls the motor based on the ratio of the widths of a raised portion and a recessed portion adjacent to each other in the rib. Therefore, this carousel changer can accurately stop a tray carrying an optical disk desired to be reproduced in a prescribed position.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to carousel changers, and more specifically, to a carousel changer including a turntable having a plurality of trays to carry a plurality of disks thereon. 
     2. Description of the Related Art 
     A carousel changer is provided in a CD player, a DVD player or the like that serves as an optical disk changer. As shown in  FIG. 5 , a carousel changer  30  includes a turntable  20 . The turntable  20  has a plurality of trays  1  around its rotating shaft  11 . The trays each carry an optical disk such as a CD and a DVD thereon. The turntable  20  rotates counter-clockwise in  FIG. 5  and transports a tray having an optical disk desired to be reproduced onto a reproducing device  13 . An annular rack rail  8  is provided under the turntable  20 . The rack rail  8  is engaged with a pinion gear  7  attached to a motor  12 , and the turntable  20  is driven by the motor  12  to rotate. The carousel changer  30  further includes an annular rib R 10  and a sensor  9  provided under the turntable  20 . The rib R 10  and the sensor  9  are used to place the center of a tray  1  carrying thereon an optical disk (that the user desires to reproduce) in the center of a support unit  14  in the reproducing device  13 . 
       FIG. 6  is a sectional view taken along line VI-VI in  FIG. 5 . The rib R 10  includes a plurality of recessed portions A 1  and a plurality of raised portions B 1 . The recessed portions A 1  and the raised portions B 1  are used to identify the tray numbers of the trays  1 , and place the center of a tray  1  in the center of the support unit  14 . The sensor  9  has the rib R 10  passed therethrough (though not in contact), detects recessed portions A 1  and raised portions B 1  of the rib R 10  and outputs the result of detection to a controller  40 . The controller  40  determines the tray number and stopping position of each of the trays  1  based on the detection result output from the sensor  9  and controls the motor  12  accordingly. 
       FIG. 7  is a partly developed view of the annular rib R 10  shown in  FIG. 6 . The rib R 10  has a stop area SA for stopping each tray  1  so that the center of the tray  1  is placed in the center of the support unit  14  and a count area CA for specifying the tray number of each tray  1 . The turntable  20  in  FIG. 5  includes six trays  1 , and therefore the rib R 10  includes six stop areas SA and six count areas CA. The stop area SA is made of a recessed portion A SA  indicating a stopping position and two raised areas B SA  having the recessed portion A SA  therebetween. When the recessed portion A SA  is subjected to the sensor  9 , the center of a tray  1  is placed in the center of the support unit  14 . The count area CA is made of a plurality of recessed portions A CA  and a plurality of raised portions B CA . In  FIG. 7 , the plurality of raised portions B CA  represent a tray number. When for example there are four such raised portions B CA , the count area CA indicates tray number “4.” 
     Referring to  FIG. 8 , it will be described how the carousel changer  30  operates to exchange an optical disk on a tray of number  3  (hereinafter as “tray No. 3”) with an optical disk on a tray of number  4  (hereinafter as “tray No. 4”). 
     When there is an optical disk on the tray with tray No.  3  on the support unit  14 , the sensor  9  detects the recessed portion A SA3  in the stop area SA 3  in the rib R 10 . Herein, the stop area SA 3  refers to a stop area for the tray No.  3 . The turntable  20  is stopped as the sensor  9  is subjected to (detects) the recessed portion A SA3  in the stop area SA 3 , the center of the disk on the tray No.  3  is positioned on the support unit  14 . At time t 1 , a command to reproduce the disk on the tray No.  4  is externally given. At the time, the controller  40  supplies positive voltage V 1  to the motor  12 . In response to the applied positive voltage V 1 , the motor  12  drives the turntable  20  to start to rotate counter-clockwise. Immediately after time t 1 , the sensor  9  detects the raised portion B SA3  in the stop area SA 3 . At time t 2 , the sensor  9  detects the recessed portion A CA4  in the count area CA 4  for the tray No.  4 . At the time, the controller  40  determines that the raised portion B SA3  has passed the sensor  9  and the sensor  9  has started detecting the count area CA 4 . The controller  40  counts up the tray numbers by one each at time t 3 , t 4 , t 5 , and t 6  when the sensor  9  detects a raised portion B CA4 . In the count area CA 4 , the sensor  9  repeatedly detects the raised portion B CA4  and the recessed portion B CA4 . If the sensor  9  cannot detect a raised portion B CA4  after starting detecting the recessed portion A CA4  for a prescribed period Δt, the controller  40  ends counting up of the tray numbers, and identifies the tray number. In  FIG. 8 , at time t 8  the prescribed period Δt after time t 7 , the controller  40  specifies the tray number as “4.” 
     At time t 9 , the sensor  9  detects a raised portion B SA4  in the stop area SA 4 . The stop area SA 4  is a stop area for the tray No.  4 , and therefore the controller  40  determines that the stop area for the tray No.  4  has been entered. At the time, the controller  40  lowers the voltage supplied to the motor  12  from the voltage V 1  to V 2  and lowers the rotating speed of the turntable  20  accordingly. At time t 10  when the sensor  9  detects the recessed portion A SA4  in the stop area SA 4 , the controller  40  temporarily supplies negative voltage V 3  to the motor  12  to apply the “brake” and then stops supplying voltage. This stops the turntable  20 . 
     The conventional carousel changer  30  determines the count end time for the tray number whether the prescribed period Δt elapses after the sensor  9  starts detecting a recessed portion A CA  in the count area CA. Therefore, when the rotating speed of the turntable  20  changes by friction or the like caused by the pinion gear  7  or the rack rail  8 , the count end time could be mistakenly determined. Since the width of the recessed portion A CA  must be secured for the prescribed period Δt, the width of the raised portions B CA  used for counting the tray numbers cannot be increased. When the tray number is “6,” at least six raised portions B CA  must be provided in the count area CA, and the recessed portion A CA  having the width corresponding to the prescribed time Δt must be provided in the count area CA. As a result, the width of the raised portion B CA  is limited. It is difficult to form a raised portion B CA  having a small width, and the portion with the small width is not strong enough. 
     In order to secure a strong rib, a rib R 1  having a stop area SA and a rib R 2  having a count area CA as shown in  FIG. 9  may be used to control the rotation of the turntable  20 . In this case, the tray number is determined by counting the recessed portions A CA  in the rib R 2 , so that the width of raised portions B CA  does not have to be small. However, the use of the two ribs necessitates the use of two sensors, which pushes up the manufacturing cost. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a carousel changer that can accurately stop a tray having an optical disk desired to be reproduced in a prescribed position. 
     A carousel changer according to the invention includes a turntable, a motor, a rib, a sensor, and a controller. The turntable is provided with a plurality of trays each carrying a disk around its rotating shaft. The motor rotates the turntable. The rib is formed annularly at the turntable and includes a plurality of recessed portions and a plurality of raised portions for indicating the position of the plurality of trays at the turntable. The sensor detects the recessed portions and the raised portions when the turntable rotates. The controller controls the motor based on the ratio of the width of the recessed portion and the width of the raised portion obtained as a detection result by the sensor. 
     The carousel changer according to the invention detects the widths of the recessed portion and the raised portion formed at the turntable while the turntable rotates, and the position of the plurality of trays at the turntable can be identified based on comparison between the widths of the recessed portion and the raised portion. Therefore, the carousel changer can determine the position of the trays more accurately than the conventional carousel changer. 
     The controller preferably controls the motor based on the ratio of the widths of the recessed portion and the raised portion adjacent to each other. 
     In this case, the carousel changer according to the invention can accurately determine the position of the trays based on the ratio of the widths of the recessed portion and the raised portion adjacent to each other. Therefore, the carousel changer according to the invention can determine the position of the trays more readily and accurately. 
     The controller preferably includes a timer. The timer counts time for which the sensor detects the recessed portion or the raised portion to obtain the width of said recessed portion or the raised portion. 
     In this way, the widths of the recessed portion and the raised portion are determined based on the count value of the timer during detection. Therefore, the widths of the recessed portion and the raised portion can be obtained more easily. 
     The rib preferably includes a plurality of count areas and a plurality of stop areas. The plurality of count areas are each for identifying one of the trays. The plurality of stop areas are for stopping the rotation of the turntable when the plurality of trays come to a prescribed position. The stop areas are alternated with said count areas. The controller determines that the sensor ends detection of the count area and starts to detect the stop area when the width of the raised portion is at most the width of the adjacent recessed portion upon detecting in the count area, and the controller determines that the sensor ends detection of the stop area and starts to detect the count area when the width of the raised portion is at most the width of the adjacent recessed portion upon detecting in the stop area. 
     In this way, the carousel changer can identify each of the plurality of trays by the count area and can see each of the trays in a prescribed position by the stop area. In the rib, the count areas and the stop areas are alternately arranged. Therefore, when a tray identified by the count area is a tray with a disk the user desires to reproduce thereon, the carousel changer can stop the tray in a prescribed position by the stop area adjacent to the count area. 
     The controller preferably identifies each of the plurality of trays based on the number of recessed portions or raised portions detected by the sensor while the sensor detects in the count area. 
     In this way, the plurality of trays can be identified based on the number of the recessed portions or raised portions in the count area. For example, when there are four recessed portions in a count area, the tray has “4” as the tray number. In this way, the tray can be identified easily and accurately. 
     The number of recessed portions or raised portions in the count area is different from the number of recessed portions or raised portions in the stop area. 
     In this way, the controller does not mistake the count areas with the stop areas. Therefore, it can be prevented that the controller will mistakenly identify the tray based on the number of the recessed portions or raised portions in the stop area. 
     These and other objects and advantages of the present invention will become clear from the following description with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a carousel changer according to an embodiment of the invention; 
         FIG. 2  is a developed view of the rib shown in  FIG. 1 ; 
         FIG. 3  is a flowchart for use in illustration of the operation of the carousel changer shown in  FIG. 1 ; 
         FIG. 4  is a timing chart for use in illustration of the carousel changer shown in  FIG. 1 ; 
         FIG. 5  is a top view of a conventional carousel changer; 
         FIG. 6  is a sectional view taken along line VI-VI in  FIG. 5 ; 
         FIG. 7  is a partly developed view of the rib shown in  FIG. 5 ; 
         FIG. 8  is a timing chart for use in illustration of the operation of the carousel changer shown in  FIG. 5 ; and 
         FIG. 9  is a developed view of another rib in a conventional carousel changer. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, an embodiment of the invention will be described in conjunction with the accompanying drawings in which the same or corresponding portions are denoted by the same reference characters and their descriptions apply likewise. 
     Referring to  FIG. 1 , a carousel changer  80  according to the embodiment of the invention includes a turntable  20 , a motor  12  that rotates the turntable  20 , a pinion gear  7  provided to the motor  12 , a rack rail  8  engaged with the pinion gear  7 , a rib R 20 , a sensor  9 , a waveform-shaping device  60 , a controller  50 , and a motor driver  70 . 
     The turntable  20  is provided with a plurality of trays  1  around its rotating shaft for carrying a plurality of optical disks thereon, which is the same as that in  FIG. 5 . The sensor  9  includes an infrared-emitting diode  91  and a phototransistor  92 . The infrared-emitting diode  91  outputs infrared radiation to the phototransistor  92 . When there is nothing obstructing between the infrared-emitting diode  91  and the phototransistor  92 , the phototransistor  92  receives the infrared radiation and the sensor  9  outputs a signal ΦA. 
     The waveform-shaping device  60  converts the signal ΦA output from the sensor  9  into a digital signal ΦB. The controller  50  receives the digital signal ΦB, determines the tray number and the stopping position, and outputs control signals ΦC 1  to ΦC 3  to the motor driver  70 . The control signal ΦC 1  is used to normally rotate the motor  12 . The normal rotation of the motor  12  causes the turntable  20  to rotate counter-clockwise. The control signal ΦC 2  is used to reversely rotate the motor  12 . The control signal ΦC 3  is used to lower the rotating speed of the motor  12 . The controller  50  includes a timer  51  and memories M 1  to M 3 . The memories M 1  and M 2  store the count value of the timer  51 . The memory M 3  is used to specify a tray number. The operation of the timer  51  and the memories M 1  to M 3  will be described later. The motor driver  70  receives the control signals ΦC 1  to ΦC 3  and outputs a signal ΦD for having the motor  12  to rotate the pinion gear  7  to the motor  12 . The other configuration is the same as that shown in  FIG. 5 . 
       FIG. 2  is a partly developed view of the rib R 20  shown in  FIG. 1 . Referring to  FIG. 2 , the rib R 20  includes stop areas SA and count areas CA both as many as the number of the trays  1  provided at the turntable  20 . The stop area SA includes a plurality of recessed portions A SA  and a plurality of raised portions B SA . The count area CA also includes a plurality of recessed portions A CA  and a plurality of raised portions B CA . The raised portion B SA  and the recessed portion A SA  have widths that satisfy the following expression (1), and the raised portion B CA  and the recessed portion A CA  have widths that satisfy the following expression (2):
 Width of raised portion B SA &gt;width of recessed portion A SA   (1) Width of raised portion B CA &gt;width of recessed portion A CA   (2) 
     When the turntable  20  rotates counter-clockwise, the rib R 20  moves in the X-direction with respect to the sensor  9 . Therefore, the sensor  9  detects the recessed portions A CA  and the raised portions B CA  in the count area CA after detecting the recessed portions A SA  and the raised portions B SA  in the stop area SA. The stop area SA has a boundary raised portion BB SA  and a boundary recessed portion BA SA  adjacent to the next count area CA. The boundary raised portion BB SA  and the boundary recessed portion BA SA  have widths that satisfy the following expression (3):
 
Width of boundary raised portion BB SA ≦width of boundary recessed portion BA SA   (3)
 
     The count area CA also has a boundary raised portion BB CA  and a boundary recessed portion BA CA  adjacent to the next stop area SA. The boundary raised portion BB CA  and the boundary recessed portion BA CA  have widths that satisfy the following expression (4):
 
Width of boundary raised portion BB CA ≦width of boundary recessed portion BA CA   (4)
 
     In the count area CA of the rib R 20 , the tray number is identified based on the recessed portions A CA . The width of the raised portion B CA  can be broaden as compared to the conventional rib R 10  that allows the tray number to be identified based on the raised portions B CA . Therefore, the strength of the rib can be improved. 
     It will be described how the carousel changer  80  operates to exchange an optical disk on the tray No.  3  with an optical disk on the tray No.  4 . 
     Referring to  FIGS. 3 and 4 , at time t 1 , the carousel changer receives a reproducing command for the optical disk on the tray No.  4 . The controller  50  rotates the turntable  20 , and carries out the count area determining operation (S 100 ) of determining when the area subjected to the sensor  9  changes from a stop area SA to a count area CA, the counting operation (S 200 ) of counting the tray numbers in the count area, and the stopping operation (S 300 ) of stopping the turntable  20  while the center of the optical disk on the tray No.  4  is placed in the center of the support unit  14 . 
     At time t 1 , the controller  50  carries out count area determining operation (S 100 ). More specifically, at time t 1 , the controller  50  pulls the control signal ΦC 1  to an H (logical high) level, the control signal ΦC 2  to an L (logical low) level, and the control signal ΦC 3  to an L level (S 1 ). The motor driver  70  receives the control signals ΦC 1  to ΦC 3  and outputs the signal ΦD at positive voltage V 1  to the motor  12 . The motor  12  normally rotates in response to the signal ΦD. As a result, the turntable  20  starts to rotate counter-clockwise. 
     After the controller  50  outputs the control signals ΦC 1  to ΦC 3 , the controller  50  determines whether or not the digital signal ΦB output from the waveform-shaping device  60  is at an L level (S 2 ). If the digital signal ΦB is at an H level, the signal ΦA output from the sensor  9  is also at an H level, and the phototransistor  92  receives infrared radiation output from the infrared-emitting diode  91 . Therefore, when the digital signal ΦB is at the H level, the recessed portion A SA3  in the stop area SA 3  is between the infrared-emitting diode  91  and the phototransistor  92 . Herein, the stop area SA 3  is a stop area for the tray with the tray No.  3 . The controller  50  repeats the operation in step S 2  until the signal ΦB attains an L level. 
     At time t 2 , the raised portion B SA3  is through the sensor  9 . At the time, the infrared radiation is obstructed by the raised portion B SA3  and does not reach the phototransistor  92 , and therefore the digital signal ΦB attains an L level. The controller  50  resets the timer  51  in response to the digital signal ΦB at the L level (S 3 ). After being reset, the timer  51  starts counting up. Then, the controller  50  determines whether or not the digital signal ΦB has attained an H level (S 4 ). If the received digital signal ΦB is at an L level, the operation in step S 4  is repeated until the  5  digital signal ΦB attains an H level. 
     At time t 3 , the recessed portion A SA3  is subjected to the sensor  9 , and the digital signal ΦB attains an H level. The controller  50  stores the count value of the timer  51  from time t 2  to t 3  in the memory M 1  (S 5 ). The controller  50  obtains the width of the raised portion B SA3  based on the count value from time t 2  to t 3 . 
     The controller  50  again resets the timer  51  (S 6 ), and then determines whether or not the digital signal ΦB is at an L level (S 7 ). The controller  50  repeats the operation in step S 7  until the digital signal ΦB attains an L level. At time t 4 , the boundary raised portion BB SA3  is through the sensor  9 , and therefore the digital signal ΦB attains an L level. At the time, the controller  50  stores the count value from time t 3  to t 4  in the memory M 2  (S 8 ). The count value stored in step S 8  indicates the width of recessed portion A SA3.    
     The controller  50  then determines whether or not the count value stored in the memory M 1  in step S 5  is greater than the count value stored in the memory M 2  (S 9 ). If the count value in the memory M 1  is greater than the count value in the memory M 2 , the width of the raised portion B SA3  is greater than the width of the recessed portion A SA3 , which satisfies the expression (1). Therefore, at time t 4 , the controller  50  determines that the stop area SA 3  is subjected to the sensor  9 . At the time, the controller  50  returns to step S 3 . The controller  50  repeats the operation in and after step S 3  until the count value in the memory M 1  is equal to or lower than the count value in the memory M 2 . 
     At time t 4 , the controller  50  resets the timer  51  (S 3 ), and determines that the digital signal ΦB has attained an H level at time t 5  (S 4 ). The controller therefore stores the count value obtained from time t 4  to t 6  in the memory M 1  as the width of the boundary raised portion BB SA3  (S 5 ). The digital signal ΦB attains an L level at time t 6  (S 8 ), and the count value from time t 5  to t 6  is stored in the memory M 2  as the width of the boundary recessed portion BA SA3 . As a result of comparison between the count values in step S 9 , the boundary raised portion BB SA3  is equal to or smaller than the boundary recessed portion BA SA3 , which satisfies the expression (3). At the time, the controller  50  determines that the stop area SA 3  passes the sensor  9  and the count area CA 4  is to enter the sensor  9 . At time t 6 , the controller  50  switches from the count area determining operation (S 100 ) to the counting operation (S 200 ). 
     In the counting operation (S 200 ), the controller  50  specifies the tray number of the tray to come next onto the support unit  14 . In the count area CA, the tray number is represented by the number of recessed portions A CA , and therefore the controller  50  specifies the number of recessed portions A CA  in the count area CA. More specifically, at time t 6 , the controller  50  resets the memory M 3  (S 100 ) and the timer  51  (S 100 ). Then, the controller  50  measures the width of the raised portion B CA4 . More specifically, the controller  50  determines whether or not the digital signal ΦB is at an H level (S 12 ). At time t 6 , the digital signal ΦB is at an L level. When the digital signal ΦB is at an L level, the controller  50  repeats the operation in step S 12  until the digital signal ΦB attains an H level. At time t 7 , the controller  50  determines that the digital signal ΦB is at an H level (S 12 ). At the time, the controller  50  stores the timer count value from time t 6  to t 7  as the width of the raised portion B CA4  in the memory M 1  (S 13 ). After the timer count value is stored in the memory M 1 , the controller  50  resets the timer  51  (S 14 ). 
     The controller  50  measures the width of the recessed portion A CA4 . More specifically, the controller  50  determines whether or not the digital signal ΦB is at an L level (S 15 ). At time t 7 , the digital signal ΦB is at an H level. The controller  50  repeats the operation in step S 15  until the digital signal ΦB attains an L level. At time t 8 , the digital signal ΦB attains an L level. At the time, the controller  50  stores the timer count value from time t 7  to t 8  as the width of the recessed portion A CA4  in the memory M 2  (S 16 ). 
     After step S 16 , the controller  50  determines whether or not the timer count value stored in the memory M 1 , i.e., the width of the raised portion B CA4  is greater than the timer count value stored in the memory M 2 , i.e., the width of the recessed portion A CA4  (S 17 ). At time t 8 , the timer count value in the memory M 1  is greater than the timer count value in the memory M 2 , which satisfies the above expression (2). At the time, the controller  50  increases the value in the memory M 3  by 1 (S 18 ). 
     After the increase, the operation of the controller  50  returns to step S 11 . The controller  50  repeats the operation in and after step S 11  until the count value in the memory M 1  is equal to or lower than the count value in the memory M 2  in step S 17 . There are six recessed portions A CA4  from time t 7  to t 9 , and during the period, the count value in the memory M 1  is larger than the count value in the memory M 2  in step S 17 . Therefore, at time t 9 , the controller  50  sets the count value in the memory M 3  to “6” (S 18 ). 
     From time t 9  to t 10 , the controller  50  stores the count value in the memory M 1  as the width of the boundary raised portion BB CA4  (S 11  to S 13 ), and from time t 10  to t 11 , the controller  50  stores the count value in the memory M 2  as the width of the boundary recessed portion BA CA4  (S 14  to S 16 ). As a result of comparison in step S 17 , the count value in the memory M 1  is equal to or lower than the count value in the memory M 2 . Since the result in step S 17  satisfies the above expression (4), the controller  50  determines that the count area CA 4  is over. 
     The controller  50  specifies the tray number (S 19 ). The controller  50  calculates the tray number according to the following expression (5):
 
Tray number=count value in memory M3−2  (5)
 
     Since the count value in the memory M 3  is 6 at time t 11 , the controller  50  obtains the tray number as “ 4 .” The reason why the recessed portions A CA4  are formed so that the count value in the memory M 3  (=6) should be larger than the tray number (=4) will be described later. After the tray number is obtained, the controller  50  determines whether or not the specified tray number is the same as the tray number for which the user has given a command for reproducing (S 20 ). The tray number specified by the user is stored in a memory that is not shown in the controller  50 . When the tray number specified by the user is different from the tray number obtained in step S 19 , the tray coming next onto the support unit  14  as the turntable  20  rotates is not the tray specified by the user. Therefore, the controller  50  returns to step S 10  and repeats the counting operation (S 200 ). More specifically, the turntable  20  continues to rotate until the tray number obtained in step S 19  matches the tray number specified by the user. According to the embodiment, the user specifies the tray number “4,” which coincides with the tray number obtained in step S 19 . Consequently, the controller  50  ends the counting operation (S 200 ), and starts the stopping operation (S 300 ). 
     Note that in step S 20  if the tray number specified by the user is different from the tray number obtained in step S 19 , and the controller  50  repeats the counting operation in S 200 , the stop areas SA and the count areas CA are not confused without having to return to the count area determining operation in S 100 . If the counting operation in S 200  is carried out in the stop areas SA 1  to SA 6  of the trays No. 1  to No. 6 , the count value in the memory M 3  is always “2.” Meanwhile, if the counting operation in S 200  is carried out in the count areas CA 1  to CA 6  of the trays No. 1  to No. 6 , the count value is from “3” to “8” and does not coincide with the count value in the stop areas SA 1  to SA 6 . This is because the recessed portion A CA  is formed so that the count value in the count area CA is greater than the count value “2” in the stop area SA. Consequently, when the controller  50  carries out the counting operation in S 200 , the stop areas SA and the count areas CA are not confused, and the tray number can be accurately specified. 
     According to the embodiment, although in the count area CA, the count value equals the tray number+2, the recessed portions A CA  need only be formed so that the count value in the stop area SA and the count value in the count area CA are different. 
     In the stopping operation, the controller  50  carries out the operation for stopping the turntable  20  so that the center of a disk on the tray No.  4  is placed in the center of the support unit  14  of the reproducing device  13  (S 300 ). More specifically, at time t 11 , the controller  50  pulls the control signal ΦC 3  to an H level (S 21 ). The control signal ΦC 3  is used to lower the rotating speed of the motor  12 . The control signals ΦC 1  and ΦC 3  are at an H level, so that the motor driver  70  lowers the voltage of the signal ΦD output to the motor  12  from V 1  to V 2 . The motor  12  receives the signal ΦD at the voltage V 2  and lowers the rotating speed of the turntable  20 . This is for the purpose of placing the center of a disk on the tray No.  4  readily and accurately in the center of the support unit  14 . 
     The controller  50  then determines whether or not the digital signal ΦB is at an H level (S 22 ). At time t 11 , the digital signal ΦB is at an L level. The controller  50  repeats the operation in step S 22  until the digital signal ΦB attains an H level. At time t 12 , the recessed portion A SA4  is subjected to the sensor  9  and the digital signal ΦB attains an H level. At the time, the controller  50  pulls the signal ΦC 1  to an L level, and the signal ΦC 2  to an H level (S 23 ). At time t 12 , the motor driver  70  receives the L level signal ΦC 1  and the H level signal ΦC 2 , and pulls the voltage of the output signal ΦD to negative voltage V 3 . The motor  12  receives the negative voltage V 3  and tries to reversely rotate. The turntable  20  that has normally rotated (counter-clockwise) then tries to reversely rotate (clockwise) by the motor  12 . Consequently, the rotating speed of the turntable  20  is lowered. The controller  50  outputs the signal ΦC 2  as a pulse and stops the turntable  20 . At time t 12 , the controller  50  resets the timer  51  (S 24 ), and maintains the signal ΦC 2  at an H level until the timer  51  counts 20 msec (S 25 ). At time t 13  after the timer  51  has counted 20 msec, the controller  50  pulls all the control signals ΦC 1  to ΦC 3  to an L level (S 26 ). By the above operation, at t 13 , the controller  50  can stop the turntable  20  while the center of the disk on the tray No.  4  is placed in the center of the support unit  14 . 
     According to the embodiment, in the count area determining operation in S 100  and the counting operation in S 200 , the controller  50  compares the width of the raised portion in the rib R 20  in  FIG. 4  to the width of the adjacent recessed portion on the right. However, the width may be compared to the width of the adjacent recessed portion on the left. 
     The embodiment of the invention has been shown and described simply by way of illustrating the present invention. Therefore, the invention is not limited to the embodiment described above and various changes and modifications may be made therein without departing from the scope of the invention.