JP4428437B2 - Optical disk device - Google Patents

Description

  The present invention relates to an optical disc apparatus that irradiates an optical disc with laser light.

  Conventionally, recordable optical disks such as CD-R (Compact Disc-Recordable) and CD-RW (Compact Disc-Rewritable) have been sold. When recording various data such as music data on these optical disks, an optical disk recording / reproducing apparatus such as a CD-R drive apparatus or a CD-RW drive apparatus is used. In these optical disc recording / reproducing apparatuses, information recording is performed by irradiating a recording surface formed on one surface of an optical disc with a laser beam corresponding to information to be recorded from an optical pickup. Further, when reading information recorded on an optical disk, laser light is emitted from an optical pickup and information is read from the return light.

  Thus, when irradiating the recording surface of the optical disc with the laser beam, the optical disc recording apparatus performs focus control so that the recording surface is irradiated with the laser beam having a desired spot diameter. In this focus control, the return light of the laser beam irradiated to the recording surface of the optical disc is received, and the focus control is performed using an astigmatism method or the like.

  As described above, the focus control in the conventional optical disk recording apparatus is feedback control performed by acquiring the return light of the laser light irradiated to the optical disk and performing the acquisition based on the acquired return light. Therefore, when a laser beam is irradiated on a region where the reflecting surface of the optical disk is not formed, a sufficient amount of return light cannot be obtained, and focus control cannot be performed.

  For example, a heat sensitive surface is provided on the surface opposite to a recording surface on which music data or the like is recorded on an optical disc, and the heat sensitive surface is discolored by irradiating the heat sensitive surface with laser light, so that characters such as music titles of music data In the case of forming an image, a laser beam must be applied to a heat-sensitive surface that cannot obtain reflected light as much as the recording surface, and accurate focus control cannot be performed.

  The present invention has been made in consideration of the above circumstances, and an optical disc capable of performing more accurate focus control when irradiating a laser beam to an area where the reflected light on the optical disc is not sufficiently obtained. An object is to provide an apparatus.

  In order to solve the above problems, an optical disk apparatus according to the present invention is an optical disk apparatus that irradiates a laser beam onto the optical disk while rotating the optical disk, and an irradiating unit that irradiates the optical disk with a laser beam. A focus actuator for defining a spot diameter of laser light irradiated to the optical disc by the irradiating means in accordance with a driving amount, and a means for determining a driving amount of the focus actuator, wherein the laser is applied to the optical disc. After irradiating light and obtaining a driving amount at which the spot diameter becomes a predetermined value, the irradiation means applies the laser light to the region where the visible image is formed or the region where the visible image is formed in the optical disc. , The drive amount of the focus actuator is set based on the acquired drive amount. Is characterized by comprising determination means for constant for.

  According to this configuration, even when recording or reading is performed by irradiating a laser beam with a low reflectance on the optical disk, it is determined by the determining means, not the focus control based on the return light from the surface. Focus control can be performed according to the focus control content. Here, the focus control content determined by the determining means is determined based on the return light obtained when the predetermined area on the optical disk is irradiated with the laser beam, and the predetermined area is determined based on the reflectance on the optical disk. By setting to a large area, sufficient return light is acquired, and the focus control content determined based on this result is the preferred focus control content according to the set optical disc. Therefore, more accurate focus control can be performed when irradiating a laser beam to a region having a low reflectance.

  According to the present invention, it is possible to perform more accurate focus control even when irradiating a laser beam to a region where the reflected light on the optical disk is not sufficiently obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<A. Configuration of Embodiment>
The present invention is an optical disc recording / reproducing apparatus that records information by irradiating a recording surface of an optical disc with a laser beam. In addition to recording information on such a recording surface, a thermosensitive surface is provided on the surface opposite to the recording surface. Has a function of forming a visible image corresponding to the image data by irradiating the heat-sensitive surface of the optical disk with the laser beam. In the following, the configuration of an optical disc capable of forming a visible image as described above will be described first, and then the configuration of an optical disc recording / reproducing apparatus capable of recording information and forming a visible image on the optical disc. Will be described.

<A-1. Configuration of optical disc>
First, FIG. 1 is a side sectional view showing a configuration of a disk-shaped optical disc capable of recording information on one side and forming a visible image on the other side. As shown in FIG. 1, this optical disc D includes a protective layer 201, a recording layer (recording surface) 202, a reflective layer 203, a protective layer 204, a heat-sensitive layer (heat-sensitive surface) 205, and a protective layer 206. It has a structure in which these are stacked in the above order. The figure schematically shows the structure of the optical disc D, and the dimensional ratios of the layers are not as shown in this figure.

  The recording layer 202 has a spiral groove (guide groove) 202a formed on the surface thereof. When recording information on the optical disc D, the recording layer 202 is irradiated with laser light along the groove 202a. Become. Therefore, when recording information, the surface of the optical disc D on the protective layer 201 side (the upper side in the figure) (hereinafter referred to as the recording surface) is set to face the optical pickup of the optical disc recording / reproducing apparatus. Information recording is performed by moving the laser beam to be irradiated along the groove 202a. On the other hand, when a visible image is formed on the surface of the optical disk D, the optical disk D is such that the surface on the protective layer 206 side (hereinafter referred to as a heat sensitive surface) faces the optical pickup of the optical disk recording / reproducing apparatus according to the present invention. Set. Then, by irradiating the heat-sensitive layer 205 with laser light, a desired position of the heat-sensitive layer 205 is thermally changed to form a visible image. As described above, the optical disc D has substantially the same configuration as the CD-R used conventionally except that the thermal layer 205 is provided, and the detailed configuration of the recording layer 202 and the like is not described. To do. In the present specification, the “heat-sensitive surface” is a surface that changes color when irradiated with laser light, and is a surface formed by the heat-sensitive layer 205 having such properties.

<A-2. Configuration of Optical Disc Recording / Reproducing Device>
Next, FIG. 2 is a block diagram showing a configuration of an optical disc recording / reproducing apparatus according to an embodiment of the present invention. As shown in the figure, the optical disc recording / reproducing apparatus 100 is connected to a host personal computer (PC) 110, and has an optical pickup 10, a spindle motor 11, an RF (Radio Frequency) amplifier 12, and a servo circuit 13. A decoder 15, a control unit 16, an encoder 17, a strategy circuit 18, a laser driver 19, a laser power control circuit 20, a frequency generator 21, a stepping motor 30, a motor driver 31, and a motor controller. 32, a PLL (Phase Locked Loop) circuit 33, a FIFO (First In First Out) memory 34, a drive pulse generator 35, and a buffer memory 36.

  The spindle motor 11 is a motor that rotationally drives an optical disk D that is a target for recording data, and the number of rotations is controlled by a servo circuit 13. In the optical disk recording / reproducing apparatus 100 according to the present embodiment, recording or the like is performed by a CAV (Constant Angular Velocity) method, so that the spindle motor 11 has a constant angular velocity set by an instruction from the control unit 16 or the like. It is designed to rotate.

  The optical pickup 10 is a unit that irradiates the optical disk D rotated by the spindle motor 11 with a laser beam, and its configuration is shown in FIG. As shown in the figure, the optical pickup 10 includes a laser diode 53 that emits a laser beam B, a diffraction grating 58, an optical system 55 that focuses the laser beam B on the surface of the optical disk D, and a light receiving device that receives reflected light. An element 56 is provided.

  In the optical pickup 10, the laser diode 53 emits a laser beam B having an intensity corresponding to the drive current when supplied with a drive current from the laser driver 19 (see FIG. 2). The optical pickup 10 separates the laser beam B emitted from the laser diode 53 into a main beam, a preceding beam, and a succeeding beam by the diffraction grating 8, and these three laser beams are polarized beam splitter 59, collimator lens 60, 1 / The light is condensed on the surface of the optical disc D through the four-wavelength plate 61 and the objective lens 62. Then, the three laser beams reflected on the surface of the optical disk D are transmitted again through the objective lens 62, the quarter wavelength plate 61, and the collimator lens 60, reflected by the deflection beam splitter 59, and passed through the cylindrical lens 63. The light is incident on the light receiving element 56. The light receiving element 56 outputs a received signal to the RF amplifier 12 (see FIG. 2), and the received light signal is supplied to the control unit 16 and the servo circuit 13 via the RF amplifier 12.

  The objective lens 62 is held by a focus actuator 64 and a tracking actuator 65 and can move in the optical axis direction of the laser beam B and the radial direction of the optical disc D. Each of the focus actuator 64 and the tracking actuator 65 moves the objective lens 62 in the optical axis direction and the radial direction according to the focus error signal and the tracking error signal supplied from the servo circuit 13 (see FIG. 2). The servo circuit 13 irradiates the recording surface of the optical disc D with laser light, for example, when recording data on a normal general CD-R, or when reading data described in a CD-ROM. When the laser beam is irradiated, a focus error signal and a tracking error signal are generated based on a light reception signal supplied via the light receiving element 56 and the RF amplifier 12, and the objective lens 62 is moved as described above to focus. Control and tracking control, that is, feedback control is performed. On the other hand, when irradiating a laser beam to a surface having a low reflectance such as a heat-sensitive surface of the optical disk D, the servo circuit 13 does not perform feedback control based on the return light, and is determined by the control unit 16 described later. The focus control according to the focus control content is configured to be performed by open loop control.

  The optical pickup 10 has a front monitor diode (not shown). When the laser diode 53 emits laser light, a current is generated in the front monitor diode that receives the emitted light, and the current is 2 is supplied from the optical pickup 10 to the laser power control circuit 20 shown in FIG.

  The RF amplifier 12 amplifies the EFM (Eight to Fourteen Modulation) modulated RF signal supplied from the optical pickup 10, and outputs the amplified RF signal to the servo circuit 13 and the decoder 15. The decoder 15 performs EFM demodulation on the EFM-modulated RF signal supplied from the RF amplifier 12 during reproduction to generate reproduction data.

  The servo circuit 13 is supplied with a control signal from the control unit 16, an FG pulse signal having a frequency corresponding to the rotation speed of the spindle motor 11 supplied from the frequency generator 21, and an RF signal from the RF amplifier 12. The servo circuit 13 performs rotation control of the spindle motor 11 and focus control and tracking control of the optical pickup 10 based on these supplied signals. Note that, as described above, the RF signal is not used for focus control when the laser beam is irradiated to the region having a low reflectance. Also, when forming a visible image on the heat-sensitive surface of the optical disc D, unlike when recording on the recording surface, it is not necessary to trace the irradiation position along a previously formed groove (guide groove) or the like. . Therefore, in this embodiment, the target value of tracking control is a fixed value (a constant offset voltage is set for the tracking actuator).

  Here, as a driving method of the spindle motor 11 when information is recorded on the recording surface (see FIG. 1) of the optical disc D or when a visible image is formed on the thermal surface (see FIG. 1) of the optical disc D, the optical disc D is used. Either a method of driving the optical disk D at a constant angular velocity (CAV: Constant Angular Velocity) or a method of rotating the optical disk D so as to have a constant recording linear velocity (CLV: Constant Linear Velocity) may be used. The optical disk recording / reproducing apparatus 100 according to the present embodiment employs the CAV method, and the servo circuit 13 rotates the spindle motor 11 at a constant angular velocity instructed by the control unit 16.

  The buffer memory 36 is information supplied from the host PC 110 to be recorded on the recording surface of the optical disc D (hereinafter referred to as recording data) and information corresponding to a visible image to be formed on the thermal surface of the optical disc D (hereinafter referred to as image data). ). The recording data stored in the buffer memory 36 is output to the encoder 17, and the image data is output to the control unit 16.

  The encoder 17 performs EFM modulation on the recording data supplied from the buffer memory 36 and outputs it to the strategy circuit 18. The strategy circuit 18 performs time axis correction processing or the like on the EFM signal supplied from the encoder 17 and outputs the result to the laser driver 19.

  The laser driver 19 drives a laser diode 53 (see FIG. 3) of the optical pickup 10 according to a signal modulated according to the recording data supplied from the strategy circuit 18 and the control of the laser power control circuit 20.

  The laser power control circuit 20 controls the laser power emitted from the laser diode 53 (see FIG. 3) of the optical pickup 10. Specifically, the laser power control circuit 20 controls the laser driver 19 so that a laser beam having a value that matches the target value of the optimum laser power indicated by the control unit 16 is emitted from the optical pickup 10. The laser power control by the laser power control circuit 20 performed here is controlled so that laser light having a target intensity is emitted from the optical pickup 10 using the current value supplied from the front monitor diode of the optical pickup 10. Feedback control.

  In the FIFO memory 34, the image data supplied from the host PC 110 and stored in the buffer memory 36 is supplied via the control unit 16 and sequentially stored. Here, the image data stored in the FIFO memory 34, that is, the image data supplied from the host PC 110 to the optical disc recording / reproducing apparatus 100 includes the following information. This image data is data for forming a visible image on the surface of the disk-shaped optical disk D. As shown in FIG. 4, each of n pieces of data on a large number of concentric circles centering on the center O of the optical disk D is shown. Information indicating the degree of gradation (shading) is described for each coordinate (indicated by a black dot in the figure). The image data includes coordinate points P11, P12... P1n in which information indicating the gradation of these coordinates belongs to the innermost circle, coordinates P21, P22... P2n belonging to one of the outer circles, Further, the data indicating the gradation of each coordinate point up to the coordinate Pmn of the outermost circle in the order of the coordinates belonging to one outer circle is described, and the FIFO memory 34 has such polar coordinates. Information indicating the degree of gradation of each coordinate is supplied in the order as described above. FIG. 4 is a diagram schematically showing the positional relationship between the coordinates, and the actual coordinates are arranged more densely than those shown. When the host PC 110 creates image data to be formed on the photosensitive surface of the optical disc D in a commonly used bitmap format or the like, the bitmap data is converted into the polar coordinate format data as described above. Then, the converted image data may be transmitted from the host PC 110 to the optical disc recording / reproducing apparatus 100.

  When a visible image is formed on the heat-sensitive surface of the optical disc D based on the image data supplied as described above, the FIFO memory 34 is supplied with a clock signal for image recording from the PLL circuit 33. It has become. Each time the clock pulse of the image recording clock signal is supplied, the FIFO memory 34 outputs information indicating the gradation degree of one coordinate accumulated first to the drive pulse generator 35. Yes.

  The drive pulse generation unit 35 generates a drive pulse for controlling the irradiation timing of the laser light emitted from the optical pickup 10 when a visible image is formed on the heat-sensitive surface of the optical disc D. Here, the drive pulse generation unit 35 generates a drive pulse having a pulse width corresponding to information indicating the degree of gradation for each coordinate supplied from the FIFO memory 34. For example, when the gradation of a certain coordinate is relatively large (when the density is large), a drive pulse with a large light level pulse width is generated as shown in the upper part of FIG. As shown in the lower part of FIG. 5, a drive pulse with a reduced write level pulse width is generated. Here, the light level is a power level at which the heat-sensitive surface (heat-sensitive layer 205) is clearly discolored when the laser power of that level is irradiated onto the heat-sensitive surface of the optical disc D. When the optical pickup 10 is supplied to the optical pickup 10, light level laser light is emitted from the optical pickup 10 for a time corresponding to the pulse width. Therefore, when the gradation is large, the light level laser beam is irradiated for a longer time, and a larger area in the unit area of the heat-sensitive surface of the optical disc D is discolored. You will see that it is a dark area. In this embodiment, the gradation shown in the image data is expressed by varying the length of the area to be changed per unit area (unit length) in this way. The servo level is a power level at which the heat-sensitive surface hardly changes when the heat-sensitive surface of the optical disc D is irradiated with that level of laser power. What is necessary is just to irradiate the laser beam of the said servo level, without irradiating.

  The drive pulse generator 35 generates a drive pulse in accordance with the information indicating the gradation for each coordinate as described above, and performs laser power control by the laser power control circuit 20, focus control by the servo circuit 13, and When it is necessary to perform the tracking control, a light level pulse or a servo level pulse for a very short period is inserted regardless of the information indicating the gradation level. For example, as shown in the upper part of FIG. 6, in order to express a visible image according to the gradation of a certain coordinate in the image data, it is necessary to irradiate laser light having a light level for a period of time T1. When the time T1 is longer than a predetermined servo cycle ST for controlling the laser power, the servo off-pulse (SSP1) for a very short time t after the servo cycle ST elapses from the time when the write level pulse is generated. ) Is inserted. On the other hand, as shown in the lower part of FIG. 6, when it is necessary to irradiate a laser beam with a servo level for a period longer than the servo cycle ST in order to represent a visible image according to the gradation of a certain coordinate in the image data, A servo on pulse (SSP2) is inserted after the servo cycle ST has elapsed after the level pulse is generated.

  As described above, the laser power control by the laser power control circuit 20 is based on the current (intensity of the irradiated laser light) supplied from the front monitor diode that receives the laser light irradiated from the laser diode 53 (see FIG. 3) of the optical pickup 10. (The current having a value corresponding to the current value). More specifically, as shown in FIG. 7, the laser power control circuit 20 samples and holds a value corresponding to the intensity of the irradiation laser beam received by the front monitor diode 53a as described above (S201, S202). . Then, when irradiation is performed with the light level as a target value, that is, when a light level drive pulse (see FIGS. 5 and 6) is generated, the light is supplied from the control unit 16 based on the sample and hold result. Laser power control is performed so that the laser light of the light level target value is irradiated (S203). Further, when irradiation is performed with the servo level as a target value, that is, when a servo level drive pulse (see FIGS. 5 and 6) is generated, it is supplied from the control unit 16 based on the sample and hold result. Laser power control is performed so that laser light of the target servo level value is irradiated (S204). Therefore, when the write level or servo level pulse is not continuously output for a time longer than the predetermined servo cycle ST (sample cycle), the servo off-pulse SSP1, the servo on-pulse as described above, regardless of the content of the image data. SSP2 is forcibly inserted so that the laser power can be controlled for each level as described above.

  As described above, the time for inserting the servo off-pulse SSP1 and the servo off-pulse SSP2 is preferably set to the minimum time within a range that does not hinder the execution of the laser power control, and the insertion time is extremely shortened. Thus, the servo as described above can be performed with little influence on the formed visible image.

  Returning to FIG. 2, the PLL circuit 33 multiplies the FG pulse signal having a frequency corresponding to the rotation speed of the spindle motor 11 supplied from the frequency generator 21, and outputs a clock signal used for visible image formation described later. To do. The frequency generator 21 outputs an FG pulse signal having a frequency corresponding to the number of spindle revolutions using a counter electromotive current obtained by the motor driver of the spindle motor 11. For example, as shown in the upper part of FIG. 8, when the frequency generator 21 generates eight FG pulses while the spindle motor 11 makes one revolution, that is, the optical disk D makes one revolution, the lower part of FIG. As shown in FIG. 4, the PLL circuit 33 outputs a clock signal (for example, a frequency of 5 times the FG pulse signal and 40 high-level pulses during one rotation of the optical disk D) obtained by multiplying the FG pulse, that is, the spindle motor 11. To output a clock signal having a frequency corresponding to the rotational speed of the optical disk D rotated. A clock signal obtained by multiplying the FG pulse signal in this way is output from the PLL circuit 33 to the FIFO memory 34, and the gradation of one coordinate is added to the clock signal every cycle, that is, every time the disk D rotates by a certain angle. The data shown is output from the FIFO memory 34 to the drive pulse generator 35. As described above, the PLL circuit 33 may be used to generate a clock signal obtained by multiplying the FG pulse. However, when the spindle motor 11 is a motor with sufficiently stable rotational drive capability. In this case, a crystal oscillator may be provided in place of the PLL circuit 33 to generate a clock signal obtained by multiplying the FG pulse as described above, that is, a clock signal having a frequency corresponding to the rotational speed of the optical disc D.

  The stepping motor 30 is a motor for moving the optical pickup 10 in the radial direction of the optical disc D set on the optical disc D. The motor driver 31 rotates the stepping motor 30 by an amount corresponding to the pulse signal supplied from the motor controller 32. The motor controller 32 generates a pulse signal according to the movement amount and the movement direction according to the movement start instruction including the movement direction and movement amount in the radial direction of the optical pickup 10 instructed from the control unit 16, and the motor driver 31. Output to. The stepping motor 30 moves the optical pickup 10 in the radial direction of the optical disc D, and the spindle motor 11 rotates the optical disc D with respect to the optical disc D, whereby the laser light irradiation position of the optical pickup 10 is set to various positions on the optical disc D. Can be moved.

The control unit 16 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls each unit of the optical disc recording / reproducing apparatus 100 according to a program stored in the ROM. And centrally controlling the recording process on the recording surface of the optical disk D and the image forming process on the thermal surface of the optical disk D including the characteristic focus control according to the present invention.
What has been described above is the configuration of the optical disc recording / reproducing apparatus 100 according to the present embodiment.

<B. Operation of Embodiment>
Next, the operation of the optical disc recording / reproducing apparatus 100 configured as described above will be described. As described above, the optical disc recording / reproducing apparatus 100 can record information such as music data supplied from the host PC 110 on the recording surface of the optical disc D, and can also record information on the thermal surface of the optical disc D. A visible image corresponding to the image data supplied from the PC 110 can be formed. The operation of the optical disc recording / reproducing apparatus 100 capable of performing processing such as information recording and visible image formation will be described below with reference to FIGS.

  First, when the optical disc D is set in the optical disc recording / reproducing apparatus 100, the control unit 16 controls the optical pickup 10 and the like, and ATIP (Absolute Time In Pregroove) is provided on the surface of the set optical disc D facing the optical pickup 10. It is detected whether information is recorded (step Sa1). As is well known, the ATIP information is information recorded in advance in a pre-groove on the recording surface of the CD-R. When the ATIP information is recorded in this way, the recording surface of the optical disc D faces the optical pickup 10. You can see that it is set. On the other hand, when ATIP information is not recorded, it can be seen that the optical disc D is set so that the heat-sensitive surface of the optical disc D faces the optical pickup 10. That is, the control unit 16 detects which side of the optical disk D is set toward the optical pickup 10 by detecting the presence or absence of ATIP information as described above. In addition to the method of detecting which surface is set toward the optical pickup 10 depending on the presence / absence of ATIP information as described above, other methods may be used, and the user faces the thermal surface to the optical pickup 10. You may make it input that it was set.

  Here, when the ATIP information is detected from the set optical disc D, it is determined that the optical disc D is set so that the recording surface faces the optical pickup 10, and the control unit 16 determines the recording surface with respect to the recording surface. Control for recording the recording data supplied from the host PC 110 is performed (step Sa2). The control for recording the recording data performed here is the same as that of the conventional optical disc recording / reproducing apparatus (CD-R drive apparatus), and the focus control is also performed by feedback control based on normal general return light. However, the explanation is omitted.

  On the other hand, when the ATIP information is not detected from the set optical disc D, it is determined that the optical disc D is set so that the thermal surface faces the optical pickup 10, and the control unit 16 determines the disc of the set optical disc D. It is determined whether or not an ID can be acquired (step Sa3). In this embodiment, the disc ID of the optical disc D is a disc ID recorded on the thermal surface of the optical disc D (see FIG. 1) having a recording surface and a thermal surface. For example, as shown in FIG. A visible image corresponding to the encoded information is described along the circumference of the outermost peripheral portion of the optical disc D on the heat sensitive surface side. In the present embodiment, as shown in the figure, the disk ID is formed on the heat-sensitive surface of the optical disk D by forming a reflective area 301a and a non-reflective area 301b having a length corresponding to the code along the circumference of the outermost peripheral portion. It is described. The control unit 16 obtains the disk ID from the reflected light by tracing the irradiation position of the laser light of the optical pickup 10 along the outermost circumference of the optical disk D.

  Therefore, when the reflective area 301a and the non-reflective area 301b corresponding to the disk ID as described above are not formed on the outermost peripheral portion of the thermal surface, the optical disk D is a general optical disk (CD) having no thermal surface. -R etc.). When the disk ID cannot be acquired in this way, the control unit 16 determines that the optical disk D is incapable of forming a visible image (step Sa4), and performs processing for notifying the user of that fact.

  On the other hand, if the disk ID can be obtained from the optical disk D, the host PC 110 waits until an image formation instruction including image data is received (step Sa5). Performs initialization control for forming a visible image on the heat-sensitive surface of the optical disc D (step Sa6). More specifically, the control unit 16 controls the servo circuit 13 so that the spindle motor 11 is rotated at a predetermined angular velocity.

  When the initialization control is completed, the control unit 16 performs a process for determining the focus control content to be performed at the time of laser beam irradiation for image formation (step Sa7). In the focus control content determination process, the control unit 16 performs a test irradiation for determining the focus control content so that the laser beam is applied to the innermost area Da of the optical disc D shown in FIG. An instruction for moving the pickup 10 is sent to the motor controller 32 to drive the stepping motor 30. Unlike the recording surface, the heat-sensitive surface of the optical disc D has a low reflectivity. However, in the optical disc D, the innermost peripheral area Da and the outermost peripheral area Db are areas with high reflectivity. In order to perform the test laser light irradiation, the laser light irradiation position of the optical pickup 10 is first moved to the area Da as described above.

  When the position of the optical pickup 10 is moved as described above, the control unit 16 instructs the optical pickup 10 to perform test irradiation with the laser beam while the optical disk D rotates once in this state, and in this way. When the laser beam is irradiated while the optical disk D is rotated once, the servo circuit 13 is instructed to perform focus control based on the return light, that is, normal general focus control.

  And the control part 16 acquires the focus control content performed by the servo circuit 13 based on the return light received while the optical disk D is rotated once, and the focus control content actually performed, That is, the focus control content obtained by changing the control amount of the focus actuator by a predetermined amount is synchronized with the clock signal supplied by the PLL circuit 33 and stored in the RAM or the like.

  More specifically, as shown in FIG. 13, at the time of the test irradiation, the astigmatism method is performed based on the signal output from the light receiving element 56 of the optical pickup 10 in the same manner as the normal general focus control. It is done using. That is, the servo circuit 13 uses the focus actuator 64 (see FIG. 3) so that circular return light (A in the figure) is received at the center of the four areas 56a, 56b, 56c, and 56d of the light receiving element 56 shown in FIG. To drive. That is, when the received light amounts of the areas 56a, 56b, 56c, and 56d are a, b, c, and d, the focus actuator 64 is driven so that the focus error obtained by (a + c) − (b + d) becomes zero. The amount (drive voltage applied to the actuator) is determined. At this time, as in normal general focus control, the focus actuator is configured to receive the spot A shown in FIGS. 13 and 14 (that is, to irradiate the optical disc D with the beam having the smallest spot diameter). 64 drive amounts are determined.

  A clock generated by the PLL circuit 33 while the optical disc D is rotated once is a focus control content obtained by changing the focus control content performed while the optical disc D is rotated once by a predetermined amount. In synchronization with each clock pulse of the signal, it is stored in the inner periphery side focus control content storage area of the RAM. That is, as schematically shown by the one-dot chain line in FIG. 15, the focus control content (actuator drive voltage) obtained by changing the focus control content actually performed when each clock pulse of the clock signal is generated by a predetermined amount is It is stored in association with the clock pulse. In the figure, for simplicity of explanation, the number of clock pulses is 16. However, the number is not limited to this number, and all generated clock pulses and focus control contents are stored in association with each other. In addition, the focus control content may be stored in association with every other number of clock pulses (every FG pulse) such as every second or every third.

  Here, since the clock pulse of the clock signal is a pulse obtained by multiplying the FG pulse supplied from the frequency generator 21, it is generated every time the optical disc D is rotated by a predetermined amount. For example, when the number of clock pulses generated during one rotation of the optical disk D is 360, it is generated every time the optical disk D is rotated by 1 °. That is, the focus control content as described above is stored in association with each fixed rotation amount (for example, 1 °) of the optical disc D.

  As described above, the focus control content changed by a predetermined amount is stored in the inner periphery side focus control content storage area, not the focus control content itself performed during the test laser light irradiation as described above. Next, the predetermined amount will be described with reference to FIG. As shown in the figure, the focus control performed when the laser beam is irradiated for the above-described test is the same as the general focus control, and the spot diameter of the laser beam irradiated onto the surface of the optical disc D is minimized. It is such control. On the other hand, in the optical disc recording / reproducing apparatus 100 according to the present embodiment, when a visible image is formed on the heat sensitive surface of the optical disc D, the heat sensitive surface is irradiated with a laser beam having a larger diameter than when recording information on the recording surface. Focus control is performed, and more specifically, focus control is performed so as to obtain the Z spot diameter shown in FIG. Accordingly, as described above, the focus actuator drive voltage, which is the focus control content actually performed as described above, corrected by the predetermined offset voltage Vd is stored as the focus control content.

  When focus control is performed according to the stored focus control content in this way, laser light is irradiated onto the heat-sensitive surface with a larger spot diameter than that during normal recording or reading during visible image formation. As described above, when a visible image is formed on the heat-sensitive surface of the optical disc D, the following effects can be obtained by irradiating the laser beam with a larger spot diameter than when recording information on the recording surface. That is, in this embodiment, when forming a visible image, laser light is irradiated while rotating the optical disc D, as in the case of recording information on the recording surface. Therefore, by increasing the beam spot diameter of the laser beam, a visible image can be formed on the entire area of the heat-sensitive surface of the optical disc D in a shorter time. The reason for this will be described with reference to FIG. As schematically shown in the figure, when comparing the case where the beam spot diameter BS of the laser beam to be irradiated is large and small, the area of the region to be image-formed when the optical disk D is rotated once is the beam. When the spot diameter BS is large, it becomes larger. For this reason, when the beam spot diameter BS is small, the optical disk D has to be rotated more in order to make the entire area the target of image formation (in the example shown in the figure, when the beam spot diameter BS is large, it is 4 rotations, and when it is small, 6 rotations). ), It takes a lot of time for image formation. For the reasons described above, the optical disc recording / reproducing apparatus 100 is configured to irradiate a laser beam having a spot diameter larger than that at the time of information recording when forming a visible image.

  As described above, when the test laser beam irradiation is performed on the innermost area Da on the optical disc D and the focus control contents are stored in the inner periphery side focus control contents storage area of the RAM in association with the clock pulse, the control unit 16 sends an instruction to the motor controller 32 to move the optical pickup 10 so that the laser beam is irradiated onto the outermost peripheral area Db of the optical disc D shown in FIG.

  Thereafter, the control unit 16 instructs the optical pickup 10 to perform the test irradiation with the laser beam while the optical disc D is rotated once, as in the case of the test irradiation with respect to the area Da of the optical disc D. The servo circuit 13 is instructed to perform focus control based on the return light, that is, normal general focus control, when irradiating the laser beam during one rotation. Thus, when irradiating the laser beam to the outer peripheral side region Db, the controller 16 starts the laser from the same position Dbs as the position Das where the irradiation of the inner peripheral side region Da is started. Instruct to start light irradiation. That is, as shown in FIG. 12, the position Das where irradiation of the laser beam to the inner peripheral area Da is started and the position of the area Db located on the same straight line in the radial direction from the center O of the optical disc D An instruction is given to start laser beam irradiation from Dbs. In this specification, such a position on the same straight line is referred to as a reference position, and whether or not the laser light irradiation position has passed through the reference position is detected by counting FG pulses. That is, assuming that the number of FG pulses corresponding to one rotation of the optical disk D is, for example, 8, the reference position is the time when 8 FG pulses are counted from the time when the laser beam is irradiated to the inner area Da. The next time when 16 pulses are counted becomes the reference position passage timing, and similarly, the timing at which 8n (n is a natural number) FG pulses are counted becomes the reference position passage timing. Irradiation of the laser beam to the region Db may be started.

  Then, the control unit 16 performs the focus control content actually performed when irradiating the region Db on the outer peripheral side of the optical disc D with the laser beam by the same procedure as when the inner peripheral focus control content is stored. The focus control content obtained by changing the control amount of the focus actuator by a predetermined amount is synchronized with the clock signal supplied by the PLL circuit 33, and the content (shown by a solid line in FIG. 15) is stored in the outer peripheral side focus control content storage area of the RAM. To remember.

  When the focus control content determination process as described above is completed, a process for actually forming a visible image on the heat-sensitive surface of the optical disc D is performed. As shown in FIG. 11, the control unit 16 first transfers the image data supplied from the host PC 110 via the buffer memory 36 to the FIFO memory 34 (step Sa8). Then, the control unit 16 determines from the FG pulse signal supplied from the frequency generator 21 whether the predetermined reference position of the optical disc D rotated by the spindle motor 11 has passed the laser light irradiation position of the optical pickup 10. Is determined (step Sa9). As described above, whether or not the laser beam irradiation position has passed through the reference position (see FIG. 12) is determined by counting the FG pulses from the time when the irradiation of the laser beam is started on the above-described inner peripheral area Da. Is detected.

  After receiving an image formation instruction from the host PC 110 and completing the focus control content determination process, when detecting that the reference position of the optical disc D has passed the laser light irradiation position, the control unit 16 sets a variable indicating the number of rotations. After incrementing R by 1 (step Sa10), it is determined whether R is an odd number (step Sa11).

  Here, when it is first detected that the reference position has been passed after the focus control content determination processing is completed, R = 0 (initial value) + 1 = 1. In this case, R is an odd number in step Sa10. It will be determined that there is. When it is determined that R is an odd number, the control unit 16 performs control for forming a visible image by irradiating the heat-sensitive surface of the optical disc D from the optical pickup 10 with a laser beam (step Sa12). More specifically, the control unit 16 receives the above reference position detection pulse and outputs each unit so as to sequentially output the image data from the FIFO memory 34 in synchronization with the clock signal output from the PLL circuit 33. Control. By this control, as shown in FIG. 17, the FIFO memory 34 outputs information indicating the gradation of one coordinate to the drive pulse generator 35 every time a clock pulse is supplied from the PLL circuit 33, and the drive pulse The generation unit 35 generates a drive pulse having a pulse width according to the gradation shown in the information and outputs the drive pulse to the laser driver 19. As a result, the optical pickup 10 irradiates the heat-sensitive surface of the optical disk D with the laser light at the light level for a time corresponding to the gradation of each coordinate, and the irradiation area changes color, thereby causing a visible image as shown in FIG. Can be formed.

  As schematically shown in the figure, the optical disk D is rotated by the spindle motor 11, so that the laser beam irradiation position of the optical pickup 10 is one cycle of the clock signal (the rising edge of the next pulse from the rising edge of the pulse). During the period until the timing), it moves along the circumference by the area indicated by C in the figure. By changing the time during which the laser beam is irradiated at the light level while the laser beam irradiation position passes through the region C according to the gradation level as described above, the gradation level varies depending on the region C as shown in the figure. Different areas can be discolored accordingly. In this way, a visible image corresponding to image data is formed on the heat-sensitive surface of the optical disc D by controlling the irradiation time of the light level laser light when passing through each region C according to the gradation of each coordinate. It can be done.

  In addition, when laser light irradiation for image formation as described above is performed, focus control according to the focus control content stored in the RAM is performed by the focus control content determination process described above, and the return from the thermal surface is performed. There is no feedback control based on light. That is, the control unit 16 determines the focus control amount based on the focus control content determined as described above and the laser light irradiation position in the radial direction of the optical pickup 10, and controls the focus actuator 64 via the servo circuit 13. .

上記式において、ｄｆはデフォーカス配分比であり、例えば０．８といった固定値である。また、fin（ｒ）は所定の関数であり、fout（ｒ）も所定の関数であり、これらの関数としてどのような関数を用いるかによって、上述した内周側フォーカス制御内容と外周側フォーカス制御内容のいずれをより多くフォーカス制御内容に反映させるかが決まる。例えば、単純に半径方向の位置ｒに応じた比例的に両者の反映具合を決める場合には、fin（ｒ）＝（Ｒ−ｒ）／Ｒ、fout（ｒ）＝ｒ／Ｒとなる。ここで、ＲはディスクＤの半径を示す。また、in（θ）は上記のように決定された内周側フォーカス制御内容であり、回転量θに対応するクロックパルスに対応付けられて記憶されているフォーカス制御内容である。同様にout（θ）は外周側フォーカス制御内容であり、回転量θに対応するクロックパルスに対応付けられて記憶されているフォーカス制御内容である。したがって、基準位置からの回転量θが図１５に示す基準位置から７個目のクロックパルスに相当するものである場合には、in（θ）はＶinとなり、out（θ）はＶoutとなる。 More specifically, the control unit 16 detects the number of clock pulses from the reference position, that is, the rotation amount information indicating the rotation amount from the reference position, which is detected one by one during the image forming period. From the θ, the position information r indicating the irradiation position in the radial direction, and the focus control content stored in the RAM, the focus control amount V that is the focus control content at that time is determined by the following equation.

In the above formula, df is a defocus distribution ratio, and is a fixed value such as 0.8. Further, fin (r) is a predetermined function, and fout (r) is also a predetermined function, and the above-described inner peripheral focus control content and outer peripheral focus control are determined depending on what function is used as these functions. Which content is to be reflected in the focus control content is determined. For example, when the reflection state of both is simply determined in proportion to the position r in the radial direction, fin (r) = (R−r) / R and fout (r) = r / R. Here, R indicates the radius of the disk D. Further, in (θ) is the inner periphery side focus control content determined as described above, and is the focus control content stored in association with the clock pulse corresponding to the rotation amount θ. Similarly, out (θ) is the outer periphery side focus control content, and is the focus control content stored in association with the clock pulse corresponding to the rotation amount θ. Therefore, when the rotation amount θ from the reference position corresponds to the seventh clock pulse from the reference position shown in FIG. 15, in (θ) is Vin and out (θ) is Vout.

  As described above, the control unit 16 controls the focus actuator 64 via the servo circuit 13 so that the focus control is performed according to the focus control amount V derived each time the clock pulse is supplied (that is, every time θ changes). To control. As a result, as described above, the laser beam having a large spot diameter is irradiated onto the heat-sensitive surface of the optical disc D (see FIG. 16), and a quicker image forming process is possible.

  As described above, when the control for executing the formation of the visible image by the laser light irradiation controlled according to the image data is executed, the processing of the control unit 16 returns to Step Sa8, and the image data supplied from the buffer memory 36 Is transferred to the FIFO memory 34. Then, it is detected whether or not the laser light irradiation position of the optical pickup 10 has passed through the reference position of the optical disc D (step Sa9). When it is detected that the reference position has passed, 1 is incremented to R (step S9). Sa10). As a result, when R becomes an even number, the control unit 16 controls each unit of the apparatus so as to stop the visible image formation by the laser light irradiation control as described above (step Sa13). More specifically, the FIFO memory 34 is controlled not to output information indicating the gradation of each coordinate to the drive pulse generator 35 in synchronization with the clock signal supplied from the PLL circuit 33. In other words, the control unit 16 irradiates the heat-sensitive surface of the optical disk D with light level laser light to form a visible image, and then changes the color of the heat-sensitive surface during the next rotation of the optical disk D. The laser light is controlled not to be irradiated.

  When the laser beam irradiation for forming the visible image is stopped in this way, the control unit 16 instructs the motor controller 32 to move the optical pickup 10 to the outer peripheral side in the radial direction by a predetermined amount (step Sa14). In response to the instruction, the motor controller 32 drives the stepping motor 30 via the motor driver 31, whereby the optical pickup 10 is moved to the outer peripheral side by a predetermined amount.

  Here, the predetermined amount by which the optical pickup 10 is moved in the radial direction of the optical disc D may be appropriately determined according to the beam spot diameter BS (see FIG. 16) irradiated from the optical pickup 10 as described above. That is, when a visible image is formed on the heat-sensitive surface of the disk-shaped optical disc D, the laser light irradiation position of the optical pickup 10 can be moved on the surface of the optical disc D with almost no gap, thereby realizing higher-quality image formation. It is necessary to do. Therefore, if the unit movement amount of the optical pickup 10 in the radial direction as described above is substantially the same as the beam spot diameter BS of the irradiation laser light with respect to the optical disc D, the laser light can be emitted on the surface of the optical disc D with almost no gap. Irradiation is possible, and higher-quality image formation is possible. In some cases, the area larger than the irradiated beam spot diameter may be colored due to various factors such as the nature of the heat-sensitive surface. In such a case, considering the width of the colored area, adjacent colored areas do not overlap. The unit movement amount may be determined as follows. In this embodiment, since the beam spot diameter BS is larger than that during recording on the recording surface (for example, about 20 μm), the control unit 16 reduces the diameter of the optical pickup 10 by substantially the same length as the beam spot diameter BS. The motor controller 32 is controlled to move in the direction, and the stepping motor 30 is driven. The stepping motor 30 in recent years can control the movement amount in units of 10 μm by using the μ step technology, and the optical pickup 10 can be controlled in units of 20 μm using the stepping motor 30 as described above. Moving in the radial direction is sufficiently feasible.

  When the control for moving the optical pickup 10 by a predetermined amount in the radial direction is performed as described above, the control unit 16 is configured to irradiate the laser beam at the light level so as to change the light level value of the target laser beam. The changed light level value to be targeted is instructed to the laser power control circuit 20 (step Sa15). In the present embodiment, a CAV method in which laser light is irradiated while rotating the optical disk D while maintaining a constant angular velocity is adopted as a method for forming a visible image, and the optical pickup 10 is moved to the outer peripheral side. As a result, the linear velocity increases. Therefore, when the optical pickup 10 is moved in the radial direction (outer peripheral side) in this way, the target value of the light level is changed to be larger than that at that time as described above, whereby the linear velocity is changed. Even if the temperature changes, the heat sensitive surface of the optical disk D can be irradiated with a laser power having such an intensity that the color can be sufficiently changed.

  As described above, when the movement control in the radial direction of the optical pickup 10 and the control for changing the target value of the light level are executed, the control unit 16 performs unprocessed image data, that is, the drive pulse generation unit 35 for forming a visible image. It is determined whether or not there is image data not supplied to the image. If there is no image data, the process is terminated.

  On the other hand, if there is unprocessed image data that has not been supplied to the FIFO memory 34, the process returns to step Sa7 to continue processing for visible image formation. That is, the image data is transferred from the control unit 16 to the FIFO memory 34 (step Sa8), and it is determined whether or not the irradiation position of the laser beam has passed the reference position of the optical disc D (step Sa9). When the reference position is passed, the variable R indicating the number of rotations is incremented by 1 (step Sa10), and it is determined whether or not the incremented R is an odd number (step Sa11). Here, when R is an odd number, the control unit 16 controls each part of the apparatus so that the laser beam irradiation for forming a visible image as described above is performed. When R is an even number, the visible image is displayed. Is stopped (irradiated with servo-level laser light), and control such as the above-described movement control of the optical pickup 10 in the radial direction and change of the target value of the light level is performed. That is, when the control unit 16 performs laser light irradiation (including the light level) for image formation on the optical disc D during a certain round, laser light irradiation for image formation is performed during the next round. Is controlled so that the optical pickup 10 is controlled to move in the radial direction during the rotation. Thus, by performing control for moving the optical pickup 10 during the lap when image formation is not performed, control for changing the light level target value, and the like, the irradiation position, the power value of the laser light to be irradiated, and the like are associated with the control. No image is formed while the angle fluctuates, and laser beam irradiation for image formation can be executed after the irradiation position and the intensity of the laser beam are stabilized. Therefore, it is possible to suppress degradation of the quality of the visible image formed due to the radial movement control of the optical pickup 10 as described above.

  What has been described above is the main operation of the optical disc recording / reproducing apparatus 100 according to the present embodiment. According to the optical disc recording / reproducing apparatus 100, information is recorded on the recording surface without newly installing printing means or the like. As much as possible, each part of the apparatus such as the optical pickup 10 used for performing the recording is irradiated with a laser beam to form the visible image corresponding to the image data. can do.

  In this embodiment, the laser light irradiation timing is set based on the clock signal generated using the FG pulse generated according to the rotation of the spindle motor 11, that is, the clock signal generated according to the rotation amount of the optical disc D. Since the control is performed, it is possible to grasp the laser beam irradiation position in the optical disc recording / reproducing apparatus 100 without acquiring position information or the like from the optical disc D side. Therefore, according to the optical disc recording / reproducing apparatus 100, there is no restriction that the optical disc D subjected to special processing such as forming a pre-groove (guide groove) on the heat sensitive surface must be used, and the groove, position information, etc. A visible image corresponding to the image data can be formed even on a heat-sensitive surface on which is not formed in advance.

  By the way, when irradiating the heat-sensitive surface of the optical disc D with laser light, it is difficult to perform feedback control based on return light as focus control because the reflectance of the heat-sensitive surface is small. However, when focus control is performed by applying a pre-fixed offset voltage or the like to the focus actuator 64, the optical pickup 10 and the heat-sensitive surface of the optical disc D are caused by unevenness of the optical disc D or shake due to rotation. The distance between the two fluctuates, and accurate focus control cannot be performed. On the other hand, as in the present embodiment, open-loop focus control is performed according to the focus control content obtained based on the return light when the laser beam is irradiated on the region (region Da and region Db) having a high reflectance in advance. By performing the above, accurate focus control can be performed even when a laser beam is irradiated to a region having a low reflectance such as a heat sensitive surface.

  Further, on the outer peripheral side and the inner peripheral side, the distance between the optical pickup 10 and the optical disc D often varies on the outer peripheral side due to blurring, and the distance between the inner peripheral side and the outer peripheral side is often the same. The degree of fluctuation will also be different. Therefore, when focus control is performed based on the focus control content obtained when the laser beam is irradiated only on the inner peripheral area Da or only on the outer peripheral area Db, the variation in the distance between the inner periphery and the outer periphery is determined. If there is a large difference between the two, the accuracy of focus control may be reduced. On the other hand, in the present embodiment, the focus control content derived from the focus control content performed when each of the inner peripheral region Da and the outer peripheral region Db is irradiated with laser light is used. Since the final focus control content is determined while changing the reflection amount of both according to the irradiation position of the laser beam, more accurate focus control can be performed.

<C. Modification>
In addition, this invention is not limited to embodiment mentioned above, Various deformation | transformation which is illustrated below is possible.

(Modification 1)
In the above-described embodiment, the test laser light is irradiated to both the inner peripheral area Da and the outer peripheral area Db, and based on the focus control content performed at these times, The focus control contents when irradiating the laser beam are determined, but the return light when the laser beam is irradiated to only one of the inner area Da or the outer area Db is used. The focus control content may be determined based on the implemented focus control content. On the heat-sensitive surface of the optical disc D used in the above-described embodiment, a region having a high reflectivity is formed in both the inner peripheral region Da and the outer peripheral region Db. For example, only one of the regions is reflected. When a region with a high rate is not formed, the test laser light irradiation may be performed only on the region.

  Further, in the above-described embodiment, the inner peripheral area Da and the outer peripheral area Db having high reflectivity are targets. However, the target area to be irradiated with the test laser light has high reflectivity, and accurate focus control is performed. Any area may be used as long as the return light necessary for the operation can be obtained, and the area is not limited to the innermost or outermost area.

(Modification 2)
In the above-described embodiment, the focus described in the above-described embodiment is used as the focus control performed when laser light is irradiated to form a visible image on the heat-sensitive surface opposite to the recording surface of the optical disc D. Although the control is performed, for example, when reading a visible image formed on the surface (label surface) opposite to the recording surface, the focus control when irradiating the label surface with laser light is the same as in the above embodiment. Control can be employed. As with the heat-sensitive surface described above, a label surface on which a visible image such as a character such as a song title or a pattern is drawn often has a smaller reflectance than the recording surface. Therefore, more accurate focus control can be performed by employing the same focus control as in the above embodiment when irradiating laser light for reading on such a label surface.

  FIG. 19 shows the configuration of an optical disc recording / reproducing apparatus that can read a visible image drawn in a region having a low reflectance such as a label surface. As shown in the figure, the optical disc recording / reproducing apparatus 100 ′ includes a visible image discriminating unit 500 in addition to the configuration of the optical disc recording / reproducing apparatus 100 in the above embodiment. Under this configuration, when a visible image formed on the label surface opposite to the recording surface of the optical disk D, for example, character information or a two-dimensional barcode is read, the control unit 16 does not use the normal optical disk D except for focus control. As in reading the EFM data recorded on the recording surface, each part of the apparatus such as the optical pickup 10, the servo circuit 13, and the laser power control circuit 20 is controlled to irradiate the label surface with laser light. Before performing laser light irradiation for reading as described above, test irradiation is performed on a region with a high reflectivity (for example, the innermost region) as in the above-described embodiment, and the focus control performed at that time The focus control content to be performed when irradiating the label surface with the laser light is obtained, and the focus control is performed according to the obtained focus control content.

  In the optical disc recording / reproducing apparatus 100 ′, the return light of the laser light irradiated on the label surface as described above is supplied to the visible image discrimination unit 500 via the RF amplifier 12. The visible image discrimination unit 500 discriminates whether or not the level of the signal supplied from the RF amplifier 12 is equal to or higher than a predetermined level value, and outputs the discrimination result to the control unit 16. The control unit 16 thus determines the discrimination results supplied from the visible image discrimination unit 500 one by one, and the position (radial position and reference position) where the laser beam was irradiated when each discrimination result was obtained. Based on the rotation angle), information such as characters drawn on the label surface is read by determining the brightness of the area for each coordinate on the label surface. Even if the amount of light reflected from the label surface is relatively small, the area is a light area (for example, a white area) depending on whether the level value of the reflected light is larger than a predetermined value as described above. In addition, it is possible to determine whether the area is low in brightness (for example, a black area), whereby simple characters, designs, barcodes, and the like can be read.

(Modification 3)
In the above-described embodiment, focus control is performed based on the return light received by the light receiving element 56 having the four areas 56a, 56b, 56c, and 56d at the time of test irradiation. In the tracking control employed, a light receiving element having two light receiving areas in addition to the above four light receiving areas is used. In an optical disc recording / reproducing apparatus having such a light receiving element, focus control content may be determined by performing focus control based on return light received by the light receiving element having these six light receiving areas.

(Modification 4)
In the above-described embodiment, the CD-R is assumed as the optical disc D, and the case where the present invention is applied to the optical disc recording / reproducing apparatus that records and reproduces the CD-R has been described. For example, the present invention may be applied to an optical disk recording apparatus, a reproducing apparatus, a recording / reproducing apparatus, or the like that can perform data recording on a CD-RW disk, a DVD-RW disk, a DVD-RAM disk, or the like.

(Modification 5)
In the above-described embodiment, the control unit 16 executes the process including the focus control content determination process (step Sa7 in FIG. 9) by executing a program stored in the ROM. A circuit may be configured, and the above processing may be executed by the hardware circuit. Further, when the above processing is performed by software, various recording media such as a CD-ROM and a floppy (registered trademark) disk on which a program for realizing the above processing on a computer is recorded may be provided to the user. Alternatively, it may be provided to the user via a communication line such as the Internet.

1 is a side cross-sectional view showing a schematic configuration of an optical disc capable of forming a visible image by an optical disc recording / reproducing apparatus according to an embodiment of the present invention. It is a block diagram which shows the structure of the optical disk recording / reproducing apparatus which concerns on one Embodiment of this invention. It is a figure which shows the structure of the optical pick-up which is a component of the said optical disk recording / reproducing apparatus. It is a figure for demonstrating the content of the image data used in order to form a visible image with respect to the heat-sensitive surface of the said optical disk by the said optical disk recording / reproducing apparatus. It is a figure for demonstrating the irradiation control content of the laser beam for expressing the contrast of an image, when the said optical disk recording / reproducing apparatus forms a visible image with respect to the heat-sensitive surface of the said optical disk. It is a figure for demonstrating the control method of the laser beam at the time of the said optical disk recording / reproducing apparatus forming a visible image with respect to the thermal surface of the said optical disk. It is a figure for demonstrating the laser power control content by the laser power control circuit which is a component of the said optical disk recording / reproducing apparatus. It is a figure which shows the clock signal produced | generated based on the FG pulse produced | generated according to the rotation amount of a spindle motor by the frequency generator 21 which is a component of the said optical disk recording / reproducing apparatus, and the said FG pulse. 4 is a flowchart for explaining the operation of the optical disc recording / reproducing apparatus. 4 is a flowchart for explaining the operation of the optical disc recording / reproducing apparatus. It is a figure which shows disk ID recorded on the thermal surface of the said optical disk. It is a figure which shows the area | region structure of the thermal surface of the said optical disk. It is a figure which shows the shape of the return light of the laser beam received by the light receiving element of the said optical pick-up of the said optical disk recording / reproducing apparatus. It is a figure for demonstrating the focus control content in the said optical disk recording / reproducing apparatus. It is a figure for demonstrating the derivation method of the focus control content calculated | required by the test irradiation by the said optical disk recording / reproducing apparatus. It is a figure for demonstrating the size of the beam spot diameter of the laser beam which the said optical pick-up of the said optical disk recording / reproducing apparatus irradiates to the said thermosensitive surface of the said optical disk. 4 is a timing chart for explaining the operation of the optical disc recording / reproducing apparatus when a visible image is formed by irradiating a laser beam onto a heat sensitive surface of the optical disc. It is a figure which shows the heat sensitive surface of the said optical disk irradiated with the laser beam by the said optical disk recording / reproducing apparatus. It is a block diagram which shows the structure of the modification of the said optical disk recording / reproducing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical pick-up, 11 ... Spindle motor, 12 ... RF amplifier, 13 ... Servo circuit, 16 ... Control part, 17 ... Encoder, 18 ... Strategy circuit, 19 ... Laser driver, 20 ... Laser power control circuit, 21 ... frequency generator, 30 ... stepping motor, 31 ... motor driver, 32 ... motor controller, 33 ... PLL circuit, 34 ... FIFO memory, 35 ... drive pulse generator, 36... Buffer memory 53. Laser diode 53 a Front monitor diode 56 Light receiving element 64 Focus actuator 65 Tracking actuator 100 Optical disk recording / reproducing device 201 Protective layer , 202... Recording layer, 203... Reflective layer, 204... Protective layer, 205 ... heat-sensitive layer, 206 ...... protective layer, 500 ...... visible image discriminator, D ...... optical disc

Claims (1)

An optical disc apparatus that irradiates a laser beam to the optical disc while rotating the optical disc,
Irradiating means for irradiating the optical disc with laser light;
A focus actuator that regulates a spot diameter of laser light irradiated to the optical disc by the irradiation means according to a driving amount;
A means for determining a drive amount of the focus actuator, after irradiating the optical disc with the laser beam and obtaining a drive amount at which the spot diameter becomes a predetermined value;
When the irradiation means irradiates the laser light to a region where a visible image is formed or a region where a visible image is formed in the optical disc, the driving amount of the focus actuator is based on the acquired driving amount. An optical disc apparatus comprising: determining means for determining

Images