Patent Publication Number: US-2012026271-A1

Title: Optical disc recording device and method for drawing image on optical disc

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of PCT International Application PCT/JP2010/001640 filed on Mar. 9, 2010, which claims priority to Japanese Patent Application No. 2009-096739 filed on Apr. 13, 2009. The disclosures of these applications including the specifications, the drawings, and the claims are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     The present disclosure generally relates to techniques of irradiating a color changeable layer which is formed on a label side of an optical disc and changes in color due to heat or light with a laser beam to form a visible image on the label side. 
     Japanese Patent Publication No. 2006-302503 discloses an optical disc recording device configured to form a visible image, that is, textual information or graphics perceptible by eyes on a data recording side of an optical disc. In this optical disc recording device, writing to the optical disc is disabled before forming the visible image in order to prevent the visible image from being overwritten with other data. 
     Moreover, in recent years, the technique of irradiating a color changeable layer on a label side of an optical disc with a laser beam to form a visible image on the label side has been proposed. 
     SUMMARY 
     Here, when on a label side on which a visible image has already been formed, another visible image is formed, the already formed visible image may be destroyed by overwriting with the another visible image. Moreover, when a visible image is formed on a scratched label side, the formed visible image overlaps scratches, which may render the image less visible. 
     In view of the foregoing, the present invention may be advantageous when destruction of a visible image which has already been formed is prevented when a visible image is formed on a label side of an optical disc. The present invention may also be advantageous when formation of a highly visible image on a label side of an optical disc is ensured. 
     Thus, an example of the present invention is an optical disc drawing process in which a color changeable layer which is formed on a label side of an optical disc and changes in color due to heat or light is irradiated with a laser beam to form a visible image in a visible image drawing area of the label side, the optical disc drawing process including: a reflected light amount acquiring process of acquiring a reflected light amount of the laser beam with which the color changeable layer is irradiated from at least one irradiation position included in a predetermined drawing determination area of the visible image drawing area; and an operation process of comparing the reflected light amount acquired from the at least one irradiation position by the reflected light amount acquiring process with a predetermined threshold value to determine whether or not the drawing determination area is suitable for formation of the visible image, wherein the visible image is not formed in the drawing determination area when the operation process determines that the drawing determination area is unsuitable for the formation of the visible image. 
     In the optical disc, in an irradiation position unsuitable for formation of a visible image such as an irradiation position in which a visible image has already been formed or an irradiation position in which a scratch has been formed, the reflected light amount of the laser beam may be greater or less than the range of the reflected light amount of an irradiation position suitable for the formation of the visible image. Thus, according to the above example, whether or not a drawing determination area is suitable for formation of a visible image is determined based on a result of comparison between the reflected light amount of the laser beam and a predetermined threshold value. When the drawing determination area is determined to be unsuitable for the formation of the visible image, the visible image is not formed in the drawing determination area. This can prevent destruction of the already formed visible image and formation of a less visible image. 
     According to the present invention, whether or not a drawing determination area is suitable for formation of a visible image is determined based on a result of comparison between the reflected light amount of the laser beam and a predetermined threshold value, and the visible image is not formed in the drawing determination area when the drawing determination area is determined to be unsuitable for the formation of the visible image, so that destruction of the already formed visible image and formation of a less visible image can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a configuration of an optical disc recording device according to an embodiment of the present invention. 
         FIG. 2  is a view illustrating a moving range of an optical head in a pickup section. 
         FIG. 3  is a view illustrating a configuration of a label side of an optical disc. 
         FIG. 4  is a view illustrating an example of division of the visible image drawing area. 
         FIG. 5  is a view illustrating an example of a reflected light amount acquired by a reflected light amount acquiring section when a visible image has already been recorded in a visible image drawing area of the optical disc. 
         FIG. 6  is a view illustrating an example of a reflected light amount acquired by the reflected light amount acquiring section when the visible image drawing area of the optical disc has a defect such as a scratch. 
         FIG. 7  is a flow chart illustrating operation of the optical disc recording device to form the visible image. 
         FIG. 8  is a flow chart illustrating a process in S 1100  of  FIG. 7 . 
         FIG. 9  is a flow chart illustrating a process in S 1200  of  FIG. 7 . 
         FIG. 10  is a flow chart illustrating a process in S 1300  of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present invention will be described below with reference to the drawings. 
     As illustrated in  FIG. 1 , an optical disc recording device  100  of the embodiment of the present invention includes a rotating section  102 , a pickup section  117 , a worm gear  119 , a stepping motor  120 , and an integrated circuit  300 , and is configured to write data to an optical disc  200 . The integrated circuit  300  may include a plurality of chips, or may include one chip. Moreover, the optical disc recording device  100  is connected to a host personal computer (not shown). 
     The pickup section  117  includes an optical head  116 , a tracking actuator  115 , a lug section  118 , and springs  123   a,    123   b  (illustrated in  FIG. 2 ). 
     The optical head  116  includes a laser  108 , a coupling lens  109 , a polarization beam splitter  110 , a photodetector  113 , a detection lens  122 , a focus actuator  114 , a tracking actuator  115 , and an objective lens  112 . A laser beam  111  generated by the laser  108  passes through the coupling lens  109  by which a parallel ray is provided. Then, the parallel ray passes through the polarization beam splitter  110 , and is applied to a surface of the optical disc  200  while being focused on the surface of the optical disc  200  by the objective lens  112 . Light reflected on the surface of the optical disc  200  passes through the objective lens  112 , the polarization beam splitter  110 , and the detection lens  122 , and enters the photodetector  113 . The photodetector  113  outputs an electric signal based on the amount of the reflected light. 
     The focus actuator  114  of the optical head  116  includes a focusing coil and a focusing permanent magnet. The objective lens  112  is attached to a movable section of the focus actuator  114 . When a voltage is applied to the focusing coil of the focus actuator  114 , a current flows over the focusing coil, and the focusing coil receives magnetic force from the focusing permanent magnet. In this way, the objective lens  112  moves in a vertical direction to the surface of the optical disc  200 . 
     The tracking actuator  115  includes a tracking coil and a tracking permanent magnet, where when a voltage is applied to the tracking coil, a current flows over the tracking coil, and the tracking coil receives magnetic force from the tracking permanent magnet. In this way, the optical head  116  horizontally moves in a radial direction relative to the surface of the optical disc  200 . 
     The lug section  118  engages with the worm gear  119  which is fixed to an axis of the stepping motor  120 . When the stepping motor  120  rotates, the worm gear  119  also rotates, thereby moving the lug section  118  along teeth of the worm gear  119  in the radial direction of the optical disc  200 . 
       FIG. 2  illustrates a moving range of the optical head  116  in the pickup section  117 . In  FIG. 2 , reference number  200  indicates a cross section of the optical disc. The optical disc  200  has a data recording side on an upper side and a label side on a lower side in  FIG. 2 . The label side is provided with a color changeable layer which changes in color due to heat or light. The springs  123   a,    123   b  are provided on both edges of the optical head  116  in the radial direction. The spring  123   a  is located radially inside the spring  123   b.  In a state in which a tracking control section  104  does not apply a voltage to the tracking coil of the tracking actuator  115 , the springs  123   a,    123   b  hold the optical head  116  at a center position between the springs  123   a,    123   b.  Note that in  FIG. 2 , like reference symbols are used to designate elements having functions similar to those of  FIG. 1 . 
     Here, when the expansion widths of the springs  123   a,    123   b  in the radial direction are d 1 , d 2 , respectively, application of a voltage to the tracking coil allows the optical head  116  to move over a range from a position located by d 1  radially inside the center position between the springs  123   a,    123   b  to a position located by d 2  radially outside the center position. That is, the optical head  116  can move over a distance represented by the sum of d 1  and d 2  with the pickup section  117  being fixed. Thus, an irradiation position P of the laser beam  111  can also move over a distance represented by the sum of d 1  and d 2  with the pickup section  117  being fixed. 
     The pickup section  117  moves over a distance L 1  in one step by rotating the stepping motor  120  and the worm gear  119 . 
     The integrated circuit  300  includes a spindle control section  101 , an operation section  103 , a tracking control section  104 , a focus control section  105 , a reflected light amount acquiring section  106 , an error signal generating section  121 , and a traverse control section  107 . 
     The spindle control section  101  controls the rotating section  102 . 
     The operation section  103  performs later-described various operations. 
     The tracking control section  104  controls the tracking actuator  115 . 
     The focus control section  105  controls the focus actuator  114 . 
     Based on the electric signal output from the photodetector  113 , the reflected light amount acquiring section  106  acquires the reflected light amount of the laser beam  111  with which the optical disc  200  is irradiated. 
     Based on the electric signal output from the photodetector  113 , the error signal generating section  121  generates a focus error signal and a tracking error signal. 
     The traverse control section  107  controls the stepping motor  120 . 
     &lt;Spindle Control&gt; 
     The optical disc recording device  100  having the configuration described above performs spindle control in a way described below. To start rotation of the optical disc  200 , the spindle control section  101  outputs, based on a rotation control instruction from the operation section  103 , a current to the rotating section  102  to accelerate the rotation. This accelerates the rotation of the optical disc  200 . When the rotation is started, the operation section  103  receives a rotation speed signal from the spindle control section  101 , and gives an instruction as to a current value to the spindle control section  101  so that the number of rotations is set to a predetermined value. The spindle control section  101  outputs the current value to the rotating section  102 . As a result, the optical disc  200  is accelerated, decelerated, or is kept at a certain multiplied speed, so that the optical disc  200  rotates at a predetermined number of rotations. 
     &lt;Focus Control•Tracking Control&gt; 
     Focus control is performed by the operation section  103  and the focus control section  105 , where the operation section  103  uses the focus error signal generated by the error signal generating section  121  to perform an operation required for the focus control, and the focus control section  105  uses a result of the operation to control the focus actuator  114 . The focus control section  105  supplies a current based on the result of the operation to the focusing coil of the focus actuator  114 , thereby controlling the focus actuator  114 . 
     Tracking control is performed by the operation section  103  and the tracking control section  104 , where the operation section  103  uses the tracking error signal generated by the error signal generating section  121  to perform an operation required for the tracking control, and the tracking control section  104  uses a result of the operation to control the tracking actuator  115 . The tracking control section  104  supplies a current based on the result of the operation to the tracking coil of the tracking actuator  115 , thereby controlling the tracking actuator  115 . 
     &lt;Formation of Visible Image&gt; 
     In the optical disc recording device  100 , the color changeable layer on the label side of the optical disc  200  is irradiated with the laser beam  111  to form a visible image on the label side. 
     To form the visible image, a current is supplied to the tracking coil of the tracking actuator  115 , so that the optical head  116  moves back and forth by a given width equal to or less than the sum of d 1  and d 2 . During this period, the optical disc  200  is rotating, so that the optical disc  200  is irradiated with the recording laser beam  111  such that the laser beam  111  moves back and forth by the given width and traces a circular arc on the optical disc  200 . Thus, continuous irradiation of a continuous arcuate area with the laser beam  111  at a same power allows the color changeable layer to change in color to have a same tone, and an arcuate visible image having a given width equal to or less than the sum of d 1  and d 2  to be formed. Moreover, controlling a current supplied to the laser  108  can produce light and shade within a continuous arc. The stepping motor  120  is rotated to move the pickup section  117  so that the entirety of the optical disc  200  is irradiated with the laser beam  111  with the optical head  116  moving back and forth by a given width equal to or less than the sum of d 1  and d 2 , which can form the visible image on the entirety of the optical disc  200 . 
     Nun, the configuration of the label side of the optical disc  200  will be described with reference to  FIG. 3 . The label side of the optical disc  200  includes three areas, that is, an area  201 , an area  202 , and an area  203 . 
     The area  201  is located at an innermost circumference of the optical disc  200 , is not provided with the color changeable layer, and has high reflectivity. In the area  201  (hereinafter referred to as a lead-in area  201 ), innermost circumference information has been recorded by forming pits and lands into a spiral track. The innermost circumference information is composed of information indicating that a surface storing the innermost circumference information is a label side of a disk supporting visible image drawing, pigment information of the disk  200 , and information indicating an optimal value of the laser beam  111 . 
     Note that the area  201  may be provided with the color changeable layer. In this case, an unrecorded portion of the area  201  has the same reflectivity as the areas  202 ,  203 . 
     The area  202  is provided with the color changeable layer, and can store symbols  204  when irradiated with the laser beam  111 . 
     The area  203  (hereinafter referred to as a visible image drawing area  203 ) is provided with the color changeable layer, as in the case of the area  202 , and is an area in which an image is to be drawn. No track exists in the area  202  and the area  203 . 
     The border between the area  202  and the area  203  is a recording start position in the radial direction when an image is recorded in the optical disc  200 . 
     To form a visible image, the operation section  103  divides the visible image drawing area  203  into a plurality of divided areas, specifies each divided area as an independent drawing determination area, and determines whether or not each divided area (each drawing determination area) is suitable for formation of the visible image. The optical disc recording device  100  does not form the visible image in a divided area (a drawing determination area) which has been determined by the operation section  103  to be unsuitable for the formation of the visible image. The determination is made based on the reflected light amount of the laser beam at a plurality of irradiation positions included in each divided area. 
     Here, the reflected light amount is acquired while the tracking actuator  115  allows the optical head  116  to move back and forth by the width which is the sum of d 1  and d 2 . For example, the tracking actuator  115  allows the irradiation position P of the laser beam  111  to move back and forth by the width which is the sum of d 1  and d 2 , and the rotation of the stepping motor  120  allows the pickup section  117  to move by the sum of d 1  and d 2  per rotation. In this way, the reflected light amount of the entirety of the optical disc  200  can be obtained within a short time which is a product of time required for one rotation of the optical disc  200  and a value obtained by dividing the width in a radial direction of the visible image drawing area  203  by the sum of d 1  and d 2 . Note that the reflected light amount may be acquired by allowing the optical head  116  to move back and forth by a width smaller than the sum of d 1  and d 2 . 
     Next, an example of division of the visible image drawing area  203  is illustrated in  FIG. 4 . In  FIG. 4 , the visible image drawing area  203  is divided into 6 portions in a circumferential direction, and is divided into 3 portions in a radial direction, so that a total of 18 divided areas are formed. The radial position of each divided area is specified based on a travel distance from the innermost circumference by the rotation of the stepping motor  120 , that is, a value input to the stepping motor  120 . 
     Moreover, the position of each divided area in the circumferential direction is specified based on the rotation speed signal input to the rotating section  102  from the spindle control section  101 . In  FIG. 4 , an example of the rotation speed signal is shown. In this example, the rotation speed signal is a pulse rising six times per rotation, and one cycle of the pulse is assigned to one divided area, so that the position of each divided area in the circumferential direction is specified. For example, when the optical disc  200  is rotated at a certain angular velocity, the irradiation position of the laser beam  111  can be specified to be in A 4  at a pulse rise after three pulse rises from a pulse rise of when the irradiation position of the laser beam  111  is in A 1 . 
     Note that when the optical disc  200  is rotated at a certain angular velocity, the rotation speed signal is not limited to the pulse signal, but the positional relationship in the circumferential direction of each divided area and the predetermined position can be specified based on any signal as long as the signal indicates time elapsed since the irradiation position of the laser beam  111  was located at a predetermined position. The predetermined position may be at any position in the circumferential direction. When the rotating speed of the optical disc  200  in acquiring the reflected light amount is set to be higher than the rotating speed in forming a visible image on the label side, the acquisition time of the reflected light amount of the entirety of the optical disc  200  can be shortened. 
     Next, a method for determining whether or not each divided area is suitable for formation of a visible image will be described. 
       FIG. 5  illustrates an example of a reflected light amount acquired by the reflected light amount acquiring section  106  when a visible image has already been recorded in the visible image drawing area  203  of the optical disc  200 . The reflected light amount of an irradiation position in the visible image drawing area  203  in which a visible image has not been recorded is equal to or less than an unrecorded state determining threshold value, whereas the reflected light amount of an irradiation position in the visible image drawing area  203  in which a visible image has been recorded is greater than the unrecorded state determining threshold value. 
     Therefore, the operation section  103  determines that a divided area including an irradiation position in which a reflected light amount greater than the unrecorded state determining threshold value is acquired is an area in which a visible image has already been formed, and which is not suitable for formation of a new visible image. 
     Note that the ratio of the number of irradiation positions in which the reflected light amount is greater than the unrecorded state determining threshold value to the number of irradiation positions in which the reflected light amount is equal to or less than the unrecorded state determining threshold value may be computed for each divided area to determine that a divided area in which the computed ratio is greater than a predetermined value is an area in which a visible image has already been formed, and which is unsuitable for formation of a new visible image. 
       FIG. 6  illustrates an example of a reflected light amount acquired by the reflected light amount acquiring section  106  when the visible image drawing area  203  of the optical disc  200  has a defect such as a scratch. When the optical disc  200  is normal, the reflected light amount has a value which is small but is close to a certain amount in an unrecorded area. A value slightly less than the above-described value is used as a defect-free state determining threshold value to measure the reflected light amount with the optical disc  200  being rotated. In this case, in an irradiation position including no defect, the reflected light amount is equal to or greater than the defect-free state determining threshold value, and in an irradiation position including a defect, the reflected light amount is less than the defect-free state determining threshold value. 
     Thus, the operation section  103  determines that a divided area including an irradiation position in which a reflected light amount less than the defect-free state determining threshold value is acquired is an area including a defect and unsuitable for formation of a visible image. 
     Note that the ratio of the number of irradiation positions in which the reflected light amount is less than the defect-free state determining threshold value to the number of irradiation positions in which the reflected light amount is equal to or greater than the defect-free state determining threshold value may be computed for each divided area to determine that a divided area in which the ratio is greater than a predetermined value is unsuitable for formation of a visible image. 
     Here, operation of the optical disc recording device  100  to form a visible image will be described with reference to a flow chart of  FIG. 7 . 
     In S 1001 , the traverse control section  107  controls the stepping motor  120  to move the pickup section  117 , thereby moving the irradiation position of the laser beam  111  to the innermost circumference of the optical disc  200 . Then, the optical disc recording device  100  allows the further movement of the pickup section  117  through the control of the stepping motor  120 , thereby moving the irradiation position of the laser beam  111  from the innermost circumference to the visible image drawing area  203  outside the lead-in area  201 . Next, in S 1002 , the rotating section  102  rotates the optical disc  200 . In S 1100 , the optical disc recording device  100  performs a later-described disk determining process. Thereafter, in S 1003 , the traverse control section  107  controls the stepping motor  120  to move the pickup section  117  so that the irradiation position of the laser beam  111  moves to the lead-in area  201 . Next, in S 1004 , focus control is set to be in an on state based on the reflectivity of the lead-in area  201 . In S 1005 , the tracking control is set to be in an on state. Then, in S 1006 , the optical disc recording device  100  reads the innermost circumference information recorded in the lead-in area  201 , and determines, based on the innermost circumference information, whether or not the optical disc  200  is a disk supporting visible image drawing. Moreover, when the innermost circumference information indicates, for example, an optimal laser current value of the visible image drawing area  203 , the value is read. Then, in S 1007 , the tracking control is set to be in an off state. In S 1008 , the traverse control section  107  controls the stepping motor  120  to move the pickup section  117  so that the irradiation position of the laser beam  111  moves to the visible image drawing area  203 . Then, in S 1200 , the optical disc recording device  100  performs a later-described drawing area determining process. In S 1300 , the optical disc recording device  100  performs a later-described drawing process. During the drawing process, the focus control is in the on state, and the tracking control is in the off state. Moreover, an image is drawn by rotating the stepping motor  120  to move the pickup section  117  in the radial direction of the optical disc  200 . When the drawing process is completed, the process of  FIG. 7  ends. 
     Note that after completing the drawing process in S 1300 , the drawing area determining process in S 1200  may be performed again to determine whether or not the image has been recorded. 
       FIG. 8  is a flow chart illustrating the disk determining process in S 1100  of  FIG. 7 . 
     First, in S 1101 , the laser  108  is set to be in an on state. Then, the process proceeds to S 1102 . 
     In  1102 , the focus control section  105  allows the focus actuator  114  to travel up and down to search a position of the focus actuator  114  in which the laser beam  111  is focused on the optical disc  200 . When a position in which the wave form of the focus error signal forms an S shape in the vicinity of a focusing point is detected, the process proceeds to S 1104 . When the position in which the wave form of the focus error signal forms the S shape in the vicinity of the focusing point cannot be detected, the process proceeds to S 1103 . 
     In S 1103 , the optical disc recording device  100  performs a NO DISC determination, and the disk determining process ends. 
     By contrast, in S 1104 , the operation section  103  measures the amplitude of the focus error signal. Then, the process proceeds to S 1105 . 
     In S 1105 , the operation section  103  compares the amplitude measured in S 1104  with a predetermined value. When the amplitude is larger than the predetermined value, the operation section  103  determines that the irradiation position of the laser beam  111  is not in the color changeable layer, and so drawing an image is impossible, and the process proceeds to S 1106 . By contrast, if the amplitude is equal to or less than the predetermined value, the operation section  103  determines that drawing an image is possible, and the process proceeds to S 1107 . 
     In S 1106 , the optical disc recording device  100  ends the disk determining process. 
     In S 1107 , the operation section  103  determines the gain of the focus control based on the amplitude of the focus error signal. Then, the process proceeds to S 1108 . 
     In S 1108 , the focus control is set to be in the on state. Then, the process proceeds to S 1109 . 
     In S 1109 , the reflected light amount acquiring section  106  acquires a reflected light amount in the on state of the focus control. Then, the process proceeds to S 1110 . 
     In S 1110 , the operation section  103  adds a predetermined value to the reflected light amount acquired in S 1109  or multiplies the reflected light amount acquired in S 1109  by the predetermined value to compute a value greater than the reflected light amount (e.g., a value 1.2 times as large as the acquired reflected light amount) as an unrecorded state determining threshold value. Then, the process proceeds to S 1111 . 
     In S 1111 , the operation section  103  subtracts a predetermined value from the reflected light amount acquired in S 1109 , or divides the reflected light amount acquired in S 1109  by the predetermined value to compute a value less than the reflected light amount (e.g., a value 0.8 times as large as the acquired reflected light amount) as the defect-free state determining threshold value. Then, the process proceeds to S 1112 . 
     In S 1112 , the focus control is set to be in the off state, and the disk determining process ends. 
     In the present embodiment, the unrecorded state determining threshold value is computed based on the reflected light amount outside the lead-in area  201 . However, when the reflectivity in the unrecorded area of the lead-in area  201  is the same as the reflectivity of the visible image drawing area  203 , the unrecorded state determining threshold value may be computed based on the reflected light amount of the lead-in area  201 . This can ensure acquisition of the reflected light amount and computation of the unrecorded state determining threshold value because the lead-in area  201  necessarily has the unrecorded area. Alternatively, the entirety of the disk determining process in S 1100  may be performed with the lead-in area  201  being irradiated with the laser beam  111 . In this way, it becomes unnecessary to perform the process of moving the pickup section  117  in S 1003 . Thus, the processing time can be reduced. 
       FIG. 9  is a flow chart illustrating the drawing area determining process in S 1200  of  FIG. 7 . The visible image drawing area  203  is divided, for example, into the divided areas described with reference to  FIG. 4 . It is provided that circumferential direction area numbers which are incremented by 1 starting from 1 are assigned to the divided areas, and radial direction area numbers which are incremented by 1 starting from 1 at the inner circumference are assigned to the divided areas. 
     First, in S 1201 , the traverse control section  107  controls the stepping motor  120  to move the pickup section  117  so that the irradiation position of the laser beam  111  moves to an innermost circumference of the visible image drawing area  203 . Then, the process proceeds to S 1202 . Here, it is provided that the visible image drawing area  203  is divided into m annular areas in the radial direction. The innermost circumference of the visible image drawing area  203  is an innermost portion of an annular area to which a radial direction area number  1  is assigned (area composed of areas A 1 -A 6  of  FIG. 4 ). Moreover, j=1. 
     In S 1202 , the operation section  103  determines the division number n in the circumferential direction of the annular area to which the radial direction area number j is assigned. Then, the process proceeds to S 1203 . The determination is made based on an externally given instruction for division. In the example of  FIG. 4 , three annular areas A 1 -A 6 , B 1 -B 6 , and C 1 -C 6  are each divided into six areas, and thus the division number n is six. When the process in S 1202  is performed after the process in S 1201 , the process in S 1202  is to determine the division number for the annular area at the innermost circumference of the visible image drawing area  203 . However, when the process in S 1202  is performed after a process in S 1212  which will be described later, the process in S 1202  is to determine the division number for annular areas except for the annular area at the innermost circumference. 
     Note that in the example of  FIG. 4 , the division number for each annular area is six so that the areas A 1 -A 6 , B 1 -B 6 , and C 1 -C 6  are obtained, but division numbers for the annular areas may differ from each other. 
     In S 1203 , the reflected light amount acquiring section  106  acquires the reflected light amounts from a plurality of irradiation positions included in the annular area to which the radial direction area number j is assigned. Here, the reflected light amounts are measured with the optical disc  200  being rotated. Thus, even when the annular area is divided into a plurality of divided areas, the reflected light amounts at the irradiation positions included in the plurality of divided areas can be successively measured during one rotation of the optical disc  200 , and thus the efficiency of measurement is high. Here, it is provided that k=1. 
     Specifically, the reflected light amounts are acquired with the optical disc  200  being rotated, where during one rotation of the optical disc  200 , the tracking actuator  115  moves the irradiation position of the laser beam  111  by d 1  inward and outward and by d 2  inward and outward from a radial position in a state where a voltage is not applied to the tracking actuator  115  (hereinafter referred to as a “reference radial position”). At each rotation of the optical disc  200 , the traverse control section  107  moves the pickup section  117  to move the reference radial position by the sum of d 1  and d 2  which are widths by which the pickup section  117  can move inward and outward. That is, the optical disc recording device  100  repeats, a plurality of times, one-rotation reflected light amount acquisition operation in which the reflected light amounts are acquired from the plurality of irradiation positions by the reflected light amount acquiring section  106  during one rotation of the optical disc  200  while moving the reference radial position by the sum of d 1  and d 2  every time the one-rotation reflected light amount acquisition operation is completed. The acquired result is recorded in, for example, a recording means, and the process proceeds to S 1204 . 
     In S 1204 , the operation section  103  compares the unrecorded state determining threshold value computed in the disk determining process in S 1100  with the reflected light amount acquired in S 1203  from each irradiation position included in the divided area to which a circumferential direction area number k is assigned. When an irradiation position in which the reflected light amount is greater than the unrecorded state determining threshold value exists, the divided area to which the circumferential direction area number k is assigned is determined to be a recorded area, and the process proceeds to S 1207 . By contrast, when an irradiation position in which the reflected light amount is greater than the unrecorded state determining threshold value does not exists, the divided area to which the circumferential direction area number k is assigned is determined to be an unrecorded area, and the process proceeds to S 1205 . 
     Note that in S 1204 , the operation section  103  may compute the ratio of the number of irradiation positions in which the reflected light amounts are greater than the unrecorded state determining threshold value to the number of irradiation positions in which the reflected light amounts are equal to or less than the unrecorded state determining threshold value. In this case, when the value of the ratio is greater than a predetermined value, it may be determined that the area is a recorded area. When the value of the ratio is less than the predetermined value, it may be determined that the area is an unrecorded area. 
     In S 1205 , the operation section  103  compares the defect-free state determining threshold value computed in the disk determining process in S 1100  with the reflected light amount measured in S 1203  for each irradiation position included in the divided area to which the circumferential direction area number k is assigned. When an irradiation position in which the reflected light amount is less than the defect-free state determining threshold value exists, the divided area to which the circumferential direction area number k is assigned is determined to have a defect, and the process proceeds to S 1207 . By contrast, when an irradiation position in which the reflected light amount is less than the defect-free state determining threshold value does not exist, the divided area to which the circumferential direction area number k is assigned is determined to have no defect, and the process proceeds to S 1206 . 
     Note that in S 1205 , the operation section  103  may compute the ratio of the number of irradiation positions in which reflected light amounts are less than the defect-free state determining threshold value to the number of irradiation positions in which the reflected light amounts are equal to or greater than the defect-free state determining threshold value. In this case, when the value of the ratio is greater than a predetermined value, it may be determined that the area has a defect. When the value of the ratio is less than the predetermined value, it may be determined that the area has no defect. 
     In S 1206 , the operation section  103  determines that the divided area to which the circumferential direction area number k is assigned is an area which is suitable for formation of a visible image and is available for drawing an image. Then, the process proceeds to S 1208 . 
     In S 1207 , the operation section  103  determines that the divided area to which the circumferential direction area number k is assigned is an area which is unsuitable for formation of a visible image and is unavailable for drawing an image. Then, the process proceeds to S 1208 . 
     In S 1208 , the operation section  103  adds 1 to k. Then, the process proceeds to S 1209 . 
     In S 1209 , the operation section  103  compares k with the division number n. When k is equal to or less than the division number n, it is determined that the determination for the divided area of one rotation is not ended, and the process proceeds to S 1204 . When k=division number n+1, it is determined that the determination for the divided area of one rotation is ended, and the process proceeds to S 1210 . 
     In S 1210 , the operation section  103  adds 1 to j, and it is provided that k=1. Then, the process proceeds to S 1211 . 
     In S 1211 , when j is the radial direction division number m+1, the operation section  103  determines that the determination for all the annular areas is ended, and ends the image drawing area determination. By contrast, when j is equal to or less than the radial direction division number m, the process proceeds to S 1202 . 
     In S 1212 , the optical disc recording device  100  moves the irradiation position of the laser beam  111  to a jth annular area from the inner side of the optical disc  200 . Then, the process proceeds to S 1202 . Here, when an outermost portion of a (j-1)th annular area from the inner side is in contact with the jth annular area, a continuous visible image and a continuous defect which extend over a plurality of annular areas can be recognized. 
     Note that the processes of S 1204 -S 1209  may not be continuously performed n times (where n is the division number in the circumferential direction), but the determinations in S 1204  for n divided areas may be made simultaneously, the determinations in S 1205  for n divided areas may be made simultaneously, and the processes in S 1208  and S 1209  may be omitted. 
     Moreover, the threshold value comparison may not performed in S 1204  and S 1205  after recording the measurement result in the recording means in S 1203 , but each threshold value may be compared with the measurement result immediately after the acquisition of the measurement result, and the comparison result may be recorded in the recording means. In this case, only a comparison result which is smaller in capacity than the measurement result may be recorded in the recording means, which can reduce the area used for the recording means. 
       FIG. 10  is a flow chart illustrating the drawing process in S 1300  of  FIG. 7 . 
     First, in S 1301 , a drawing instructed image which the optical disc recording device  100  will draw is loaded from a host personal computer. Then, the process proceeds to S 1302 . 
     In S 1302 , the operation section  103  reads whether or not each divided area is determined to be an area available for drawing the image in the drawing area determining process of S 1200 . Then, the process proceeds to S 1303 . 
     In S 1303 , the operation section  103  determines, based on the determination result read in S 1302  for each divided area, whether or not the entirety of the drawing instructed image loaded in S 1301  can be drawn. If it is possible to draw the entirety of the drawing instructed image, the process proceeds to S 1304 . If it is not possible to draw part or the entirety of the drawing instructed image, the process proceeds to S 1312 . For example, all the area, that is, all the divided areas are available for drawing the image, the process proceeds to S 1304 . Even when some divided areas are not available for drawing the image, the process proceeds to S 1304  if the divided areas are areas in which the drawing instructed image loaded in S 1301  is not to be drawn. 
     In S 1304 , the traverse control section  107  moves the pickup section  117  through the rotation of the stepping motor  120 , thereby moving the irradiation position of the laser beam  111  to the innermost circumference of the divided area which is located at the innermost circumference and in which the image is to be drawn. Then, the process proceeds to S 1305 . Here, it is provided that p=1. 
     In S 1305 , the optical disc recording device  100  forms a visible image in a divided area of a pth annular area from the inner side among a plurality of annular areas obtained by dividing the visible image drawing area  203  by m in the radial direction, where the divided area is determined to be an area available for drawing a picture in the drawing area determining process in S 1200  and has the drawing instructed image, whereas the optical disc recording device  100  does not form the visible image in other divided areas. Next, the process proceeds to S 1306 . 
     In S 1306 , 1 is added to p. Then, the process proceeds to S 1307 . 
     In S 1307 , the operation section  103  compares p with the radial direction division number m. When p is equal to or less than m, the operation section  103  determines that the formation of the visible image in all the annular areas is not ended, and the process proceeds to S 1308 . When p is m+1, the operation section  103  determines that the formation of the visible image in all of the annular areas is ended, and the process proceeds to S 1309 . 
     In S 1308 , the traverse control section  107  moves the irradiation position of the laser beam  111  to the pth annular area from the inner side. Then, the process proceeds to S 1305 . Here, if an outermost portion of a (p-1)th annular area from the inner side is in contact with the pth annular area, a continuous image extending over the plurality of annular areas can be formed. 
     In S 1309 , the optical disc recording device  100  records a pattern in the area  202  of  FIG. 3  for each divided area in which the visible image is formed, where the pattern indicates that the visible image has been drawn in the divided area. Then, the process proceeds to S 1310 . Checking the pattern makes it possible to determine whether or not the image has been drawn without performing the disk determining process in S 1100  of  FIG. 7 . That is, the optical disc recording device  100  is configured so that a visible image is not formed in the divided area for which the pattern indicates that the image has been drawn, thereby reducing time for the disk determining process. 
     In S 1310 , the optical disc recording device  100  notifies the end of the drawing process to the host personal computer to end the drawing process. 
     In S 1311 , the optical disc recording device  100  notifies to the host personal computer that the drawing instructed image overlaps an area which has a recorded image or a defect. Then, the process proceeds to S 1312 . 
     In S 1312 , the optical disc recording device  100  waits for a change request for the drawing instructed image for an independently set period. When the optical disc recording device  100  receives the change request from the host personal computer, the process proceeds to S 1313 . When the optical disc recording device  100  does not receive the change request after the independently set period has elapsed, the drawing process ends. 
     In S 1313 , the optical disc recording device  100  compares an image after the change with the drawing instructed image originally loaded in S 1301 . When there is a change, the process proceeds to S 1301 , but when there is no change, the process proceeds to S 1314 . 
     In S 1314 , the optical disc recording device  100  determines whether or not the drawing instructed image overlapping the area having a recorded image or a defect is forcibly formed. When the optical disc recording device  100  receives, from the host personal computer, an instruction that the image is to be forcibly formed, the process proceeds to S 1304 , but otherwise, the process proceeds to S 1315 . In S 1315 , the optical disc recording device  100  notifies, to the host personal computer, that drawing the image is not performed to end the drawing process. 
     According to the present embodiment, a visible image is not formed in a divided area including an irradiation position in which a reflected light amount greater than the unrecorded state determining threshold value is acquired. This prevents destruction of a visible image which has already been formed. Moreover, a visible image is not formed in a divided area including an irradiation position in which the reflected light amount less than the defect-free state determining threshold value is acquired, so that the visible image which is to be formed does not overlap a defect such as a scratch. This can ensure formation of a highly visible image. 
     Note that in the present embodiment, the host personal computer sends the drawing instructed image to the optical disc recording device  100 , and the optical disc recording device  100  determines, based on the determination result in the drawing area determining process in S 1200 , whether or not the entirety of the drawing instructed image can be drawn. However, the optical disc recording device  100  may send the determination result in the drawing area determining process in S 1200  to the host personal computer, and the host personal computer may generate a visible image which does not overlap an area in which the image cannot be drawn as the drawing instructed image, and send the drawing instructed image to the optical disc recording device  100 . 
     Moreover, in the present embodiment, the visible image drawing area  203  is divided into a plurality of divided areas, and it is determined whether or not each of divided areas is suitable for formation of a visible image. However, it may be determined whether or not the entirety of the visible image drawing area  203  is suitable for the formation of the visible image without dividing the visible image drawing area  203 . 
     Although the visible image drawing area  203  in the present embodiment is divided both in the radial direction and in the circumferential direction, the visible image drawing area  203  may be divided in any one of the directions. 
     Although the above determination for each divided area is made based on the reflected light amounts of the plurality of irradiation positions in the present embodiment, the determination may be made based on the reflected light amount of one irradiation position. 
     Although the optical disc recording device  100  in the present embodiment is connected to the host personal computer, the optical disc recording device  100  may be connected to a controlling microcomputer instead of the host personal computer, and the controlling microcomputer may serve as the host personal computer. 
     The optical disc recording device and the method for drawing an image on an optical disc according to the present invention have the advantage that destruction of already formed visible image and formation of less visible image can be prevented, and are useful as a technique in which a color changeable layer which is formed on a label side of an optical disc and changes in color due to heat or light is irradiated with a laser beam to form a visible image on the label side.