JP2007323809A - Optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time needed for forming an image on an optical disk 200. <P>SOLUTION: Condensing points S1m, S2m and S3m of laser beams are arranged in a radial direction of the optical disk 200 by using a laser array radiating the three laser beams. In the optical disk 200, main scanning of one column is performed by radiation of the laser beam when the disk is rotated and sub scanning is performed by moving the radiation point from an inner peripheral side to an outer peripheral side by one column for every formation of dots of one column. Tracking is operated so that tracks of the condensing points S1m, S2m and S3m in the first main scanning (1) and the second main scanning (2) for the one column are not overlapped. When a discolored region is formed by radiating the laser beam according to dot data in such scanning operation, an image having a high contrast ratio can be formed in a short time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc applied to an optical disc apparatus that shortens the time required for image formation on the optical disc.

Data recording on optical discs such as CD-R (Compact Disc-Recordable) and CD-RW (Compact Disc-Rewritable) is performed by irradiating the recording layer with laser light having a spot diameter of about 1 μm to change the color change area (pit). It is impossible to identify the contents of the data record with the naked eye. Therefore, a technique for forming an image such as a character, a symbol, or a picture on the optical disk using the same optical system as that for data recording is proposed so that the optical disk on which the data is recorded can be visually identified. (For example, refer to Patent Document 1). According to this technique, an image is formed by irradiating a laser beam with an intensity corresponding to a dot to change the color of a recording layer for recording data.
Japanese Patent Laid-Open No. 11-134648

However, there is a drawback that it takes a long time to form a high-quality image using an optical system for recording data.
To explain this point, when the resolution of the image is, for example, 250 dpi (dot per inch), the size of one dot is about 0.1 mm square, but this dot is once applied with a laser beam having a spot diameter of about 1 μm. Even when scanning, the ratio of the discolored portion to the area of one dot is only 1%.
Here, if the spot diameter of the laser beam is enlarged, the proportion of the portion that changes color by one scan can be improved, but the light intensity per unit area decreases, so that the laser beam is inevitably increased. It must be output or the rotational speed must be reduced.
Generally, semiconductor lasers are used as lasers (oscillators) that output laser light from the viewpoint of miniaturization and low current consumption. However, such semiconductor lasers must have a low junction temperature, so they have high output. It is difficult. On the other hand, if the rotation speed is decreased, the time required for image formation becomes longer. For this reason, when a semiconductor laser is used as a condition that the rotation speed is not lowered, the spot diameter can be expanded only to about 10 μm at most. Eventually, when the spot diameter is scanned once with a laser beam of 10 μm, the ratio of the discolored portion is improved to 10%, but it is still far from obtaining a sufficient contrast ratio.
Therefore, in order to increase the proportion of the discolored portion, it is necessary to repeatedly scan in the form of filling the same dot, and as a result, much time is required.
The present invention has been made in view of such circumstances, and an object thereof is to provide an optical disc device applicable to an optical disc device capable of shortening the time required for image formation.

  The above object has a recording surface and a label surface, and an image is formed by irradiating a combined light of a laser beam having a first wavelength and a laser beam having a second wavelength different from the first wavelength from the label surface. In the optical disk to be formed, the recording surface includes a recording layer that changes color when irradiated with the laser beam of the first or second wavelength, and a reflective layer that is positioned below the recording layer. The surface is achieved by an optical disc including a photosensitive layer positioned on the reflective layer and having photosensitivity to the light of the first and second wavelengths. Since the photosensitive layer of this optical disc has photosensitivity with respect to the first wavelength and the second wavelength, when the laser beams of the first and second wavelengths are combined and irradiated, the color changes in a short time. The time required for image formation is shortened.

  As described above, according to the present invention, it is possible to reduce the time required to form an image on an optical disc.

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
First, the configuration of the optical disc apparatus according to the first embodiment of the present invention will be described. FIG. 1 is a block diagram showing the configuration of the optical disc apparatus 10A. This optical disc apparatus 10A is provided with an image forming function for forming an image in addition to a data recording function for recording data on a CD (-R) as the optical disc 200.
In FIG. 1, the control unit 130A controls each unit of the optical disc apparatus 10A. The spindle motor 140 rotates the optical disc 200. The rotation detector 142 generates, for example, 8 pulses at equal intervals every time the spindle motor 140 rotates once, and outputs this as a detection signal FG. Therefore, the control unit 130A can know that the optical disc 200 has rotated once by counting the rising edge of the detection signal FG eight times, and can know the rotation speed of the optical disc 200 based on the frequency of the detection signal FG. Furthermore, the control unit 130A can know that the optical disc 200 has been rotated by a minute angle by multiplying the frequency of the detection signal FG and detecting that one cycle of the multiplied signal has elapsed. For example, when the multiplication rate of the detection signal FG is “450”, one cycle of the multiplication signal corresponds to a period during which the optical disc 200 rotates by 0.1 degree (= 360/8/450).
This optical disc apparatus 10A records data or forms an image by a CAV (Constant Angular Velocity) method with a constant angular velocity. Therefore, the servo circuit 144 feedback-controls the spindle motor 140 so that the rotation speed indicated by the signal FG matches the target value instructed from the control unit 130A.

Next, the pickup 100A is a block that has three lasers (oscillators) that irradiate the optical disc 200 with laser light, and that receives one return, and the pickup control circuit 150A has the intensity of the return light (the intensity of the return light). ) And the hold signal LLa, and various controls such as focusing and tracking in the pickup 100A. Details of the pickup 100A and the pickup control circuit 150A will be described later.
The stepping motor 146 is arranged so that the rotation axis thereof is in the radial direction of the optical disc 200, and rotates in accordance with an instruction from the control unit 130A. Since the pickup 100 </ b> A is screwed into the rotation shaft of the stepping motor 146, the pickup 100 </ b> A moves in the radial direction of the optical disc 200 by the rotation of the stepping motor 146.
When reproducing data, the decoder 182A demodulates the light quantity signal La by EFM (Eight to Fourteen Modulation), and the interface (I / F) 184 is for connection with a host computer.
The write signal generator 186A has three sets so that the return light indicated by the light amount signal La and the hold signal LLa is set by the control unit 130A and becomes a target value of light intensity necessary for data recording or image formation. The current of the drive signals L1, L2, L3 to a certain laser is operated as described later. The write signal generator 186A has a buffer for temporarily storing recording data or image data.
In the CAV method, the linear velocity increases as the distance from the optical disk 200 increases. For this reason, the control unit 130A sets the target value of the light intensity to be higher as the pickup 100A is located outside the optical disc 200.

<Pickup and its surroundings>
Next, details of the pickup 100A and the pickup control circuit 150A will be described. FIG. 2 is a block diagram showing these configurations. As shown in this figure, the pickup 100A detects a laser array 102 that emits three laser beams, a diffraction grating 104, an optical system 110A that focuses the laser beams on the optical disc 200, and reflected (returned) light. The light receiving element 108 is provided.
Among these, the laser array 102 is a device in which the first, second, and third lasers are integrated in the same semiconductor chip, and has a light intensity corresponding to the current values of the drive signals L1, L2, and L3, respectively. Each of the laser beams is emitted, and their emission points are arranged at equal intervals on a straight line.
When three laser beams are emitted from the laser array 102, each of the three laser beams is separated into a main beam and two sub beams by the diffraction grating 104, respectively, and then a polarized beam constituting the optical system 110A. As shown in FIG. 3 with respect to the optical disc 200, the three beams are reflected by the splitter 111 in the direction perpendicular to the collimator lens 112, the quarter wavelength plate 113, and the objective lens 114. The light spots S1m, S2m, and S3m are focused.
Here, the condensing points S1m, S2m, and S3m have a relationship of being arranged at equal intervals on a line orthogonal to the forming direction of the pregroove 202a. Among these, the condensing point S2m is obtained by focusing the main beam of the laser beam from the second laser at the center of the array. Similarly, the condensing points S1m and S3m are respectively laser beams from the first and third lasers. The main beam is focused. As shown in FIG. 4, the pregroove 202a has a clockwise spiral shape with the inner peripheral side as the starting point and the outer peripheral side as the end point on the recording surface of the optical disc 200, and as shown in FIG. It is a groove-like region formed by finely meandering. Note that the interval between these condensing points is closely related to the resolution of the image to be formed and the diameter (spot diameter) of the condensing points. In the present embodiment, it is assumed that the resolution of the formed image is 250 dpi, the diameter of the condensing point at the time of image formation is 10 μm, and the laser array has a distance of about 17 μm between the condensing points S1m, S2m, S3m. 102 and the optical system 110A are designed.

  On the other hand, each of the condensing points S2a and S2b is obtained by focusing the sub-beam of the laser beam from the second laser. When the center of the condensing point S2m coincides with the center of the pregroove 202a, the condensing point is obtained. The point S2a is on the inner surface of the pre-groove 202a, and the condensing point S2b is on the outer surface. Each of the condensing points S1a and S1b is obtained by focusing the sub beam of the laser beam from the first laser. Similarly, each of the condensing points S3a and S3b is respectively a laser beam by the third laser. However, since these are not used for various controls to be described later, description thereof will be omitted.

  Returning to FIG. 2, the objective lens 114 is held by the focus actuator 121 and the tracking actuator 122. Among these, the focus actuator 121 operates the objective lens 114 in the direction of the optical axis 125 so as to approach the optical disc 200 as the voltage of the focus drive signal Fc increases. The tracking actuator 122 operates the objective lens 114 in the radial direction of the optical disc 200 in accordance with the tracking signal Tr (or Ts).

On the other hand, the laser beam reflected by the optical disc 200 passes through the objective lens 114, the quarter-wave plate 113, and the collimator lens 112 again in order, passes through the polarization beam splitter 111, passes through the cylindrical lens 115, and enters the light receiving element 108. Incident.
As shown in FIG. 5, the light receiving element 108 has six detection areas a to f. Of these, the areas a to d receive the return by the main beam of the second laser, and the area e is the sub-area. A return by one of the beams is received, and area f receives a return by the other of the sub-beams, and outputs a light reception intensity (a signal indicating) for each area. For this reason, the light reception signal Rv is a generic name of these light reception intensities.
The arithmetic circuit 152 calculates (b + d) + (a + c) for the received light intensity in the areas a to d, outputs a signal La indicating the result, calculates (b + d) − (a + c), A signal Fe indicating the result is output. The arithmetic circuit 152 calculates (ef) for the areas e and f, and outputs a signal Te indicating the difference between the two.

Here, among the three laser beams, the return beam (intensity) of the main beam by the second laser is indicated by the sum of the light amounts of the areas a to d, and thus the signal La is used as the light amount signal.
Further, in the light receiving element 108, the image formed by the main beam becomes a vertical ellipse (1) (shown by a round numeral; the same applies hereinafter) when the objective lens 114 is close to the optical disk 200 by the cylindrical lens 115. Becomes a horizontal ellipse (2) when the lens is far from the optical disc 200, and when the objective lens 114 is at an appropriate position with respect to the optical disc 200 (when the focus point of the laser beam is substantially located in the reflective layer of the optical disc). It becomes a perfect circle (3). For this reason, when the objective lens 114 is too close to the optical disc 200, the polarity of the signal Fe becomes negative, whereas when the objective lens 114 is too far from the optical disc 200, the polarity of the signal Fe becomes positive. The absolute value corresponds to the amount of error from the appropriate state. For this reason, the signal Fe becomes a focus error signal indicating how much the focus point of the laser beam is deviated from the appropriate value in which direction. Therefore, it is only necessary to operate the focus actuator 121 so that this error amount becomes zero at the time of data recording (reproduction), and at the time of image formation, this error amount corresponds to the case where the diameter of the condensing point S2m is 10 μm. The focus actuator 121 may be operated so that the value α is constant.
On the other hand, as described above, when the center of the condensing point S2m is located at the center of the pre-groove 202a, the condensing point S2a by one sub-beam is on the inner surface of the groove and the condensing point by the other sub-beam. Since S2b is applied to the outer surface, the signal Te indicating the difference between the received light intensities of the areas e and f is shifted to the inner side / outer side of the condensing point S2m by the main beam with respect to the pregroove 202a. And a tracking error signal indicating the amount of error. Therefore, when the optical disc 200 is rotated, the tracking actuator 122 may be operated so that this error amount is zero in order to cause the condensing point S2m to follow the pregroove 202a.

The sampling and hold (S / H) circuit 165 samples the light amount signal La at the rising edge of the sampling pulse Sp supplied from the control unit 130A in the case of image formation, and holds it until the next rising edge of the sampling pulse Sp. The hold signal LLa is supplied to the write signal generator 186A.
The sampling and holding circuit 161 supplies the focus error signal Fe to the loop filter 171 as it is in the case of data recording, but in the case of image formation, the sampling and holding circuit 161 samples at the rising edge of the sampling pulse Sp and Hold until the next rise, and supply the hold signal to the loop filter 171. When data recording is instructed by the signal R / I supplied from the control unit 130A, the loop filter 171 generates the focus drive signal Fc so that the error amount indicated by the focus error signal Fe becomes zero. On the other hand, when image formation is instructed by the signal R / I, the focus drive signal Fc is generated so that the error amount indicated by the focus error signal Fe is constant at the value α, and the signal is focused. It is supplied to the actuator 121.
The loop filter 172 generates the tracking drive signal Tr so that the error amount indicated by the tracking error signal Te becomes zero, and supplies the generated signal to the tracking actuator 122 via the switch SW. When data recording is instructed by the signal R / I, the switch SW is closed between a and c as indicated by a solid line in FIG. 2, while image formation is instructed by the signal R / I. In this case, the double throw switch is closed between bc as shown by the broken line.

By the way, as shown in FIG. 6, the image on the optical disc 200 is composed of m rows and n columns of dots (black dots in the figure) in which the row direction is the circumferential direction of the optical disc 200 and the column direction is the radial direction of the optical disc 200. Is done. The dots of m rows and n columns are main-scanned in the row direction by the laser beam irradiation when the optical disc 200 is rotated, while the laser beam irradiation point is set every time one row of dots is formed. Sub-scanning is performed in the column direction by moving from the inner circumference side to the outer circumference side by one row. A target image is formed by irradiating laser light in accordance with dot data indicating the density of dots during such scanning and sequentially forming a color-changing region.
Here, since the sub-scan in the image formation is only the feed of the pickup 100A, the tracking control in the data recording is invalidated.
Further, when an image is formed in the present embodiment, main scanning of dots located in the same row (circumference) is executed twice. However, if the discoloration region due to laser light irradiation overlaps in the two main scans, an improvement in contrast ratio cannot be expected. Therefore, for the main scan of dots located in the same row, the tracking position (condensing point It is necessary to change the trajectory).
Therefore, the offset voltage generator 175 detects whether the main scanning of the dots located in the same row is the first time or the second time based on the signal Tg supplied from the control unit 130A, and responds to this detection. Thus, the tracking drive signal Ts having a different DC voltage is output. For example, the tracking drive signal Ts at the time of the second main scan may be a signal that causes the main scan to be closer to the outer periphery by half of one dot than the first main scan. In the following, for convenience of explanation, the tracking drive signal Ts at the time of image formation will be described as a DC voltage. However, if a DC voltage is used as the tracking drive signal, noise is generated or the sensitivity of the tracking actuator varies. Since the influence cannot be ignored, an AC signal that vibrates in the same row and has a different phase when passing through the reference line in each main scan so that no overlap occurs in the discoloration region is generated as the tracking drive signal Ts. It may be used as

  Here, the reference line in FIG. 6 is an imaginary line to be used as a reference for the matrix of m rows and n columns, and eight detection signals FG from the rotation detector 142 are output per rotation when the optical disc 200 is rotated. When attention is paid to one pulse among the pulses, this is a straight line connecting points irradiated with laser light at the timing when the pulse of interest rises. Further, when the optical disc 200 is rotated, the fact that the optical disc 200 is rotated by an angle corresponding to one column of the matrix is detected by multiplying the frequency of the detection signal FG and rising of the multiplied signal.

<Operation>
Next, the operation of the optical disc apparatus 10A according to the present embodiment will be described.

<Data recording>
When recording data on the optical disc 200, the control unit 130A first instructs the servo circuit 144 the target value of the rotational speed, and secondly, rotates the stepping motor 146 to cause the pickup 100A to be pre-recorded on the optical disc 200. Move to the starting point of the groove 202a, and thirdly, the signal SW is closed between a and c by the signal R / I, and the error amount indicated by the focus error signal Fe is set to zero for the loop filter 171. The generation of the focus drive signal Fc is instructed. Fourth, the target value of the light intensity of the first and third lasers is set to zero for the write signal generator 186A, while the light intensity of the second laser is set. Set the target value necessary for data recording.
Here, the target value necessary for data recording is a value corresponding to data obtained by EFM-modulating data supplied from the host computer via the interface 184 and subjecting the EFM signal to time axis correction processing or the like. Thus, it is a binary value of a write level sufficient to form a discolored pit in the recording layer and a servo level not to discolor the recording layer. Therefore, of the three lasers, only the second laser at the center of the array is lit at the write level or servo level according to the data to be recorded, and the other first and third lasers are turned off.

On the other hand, the light receiving element 108 detects only the return light of the laser from the second laser. Of the return light, the focus error signal Fe is generated by the arithmetic circuit 152 by the return light of the main beam, and the focus drive signal Fc is generated by the loop filter 171 in a direction that cancels the error amount. Since it is operated in the direction of the optical axis 125 in accordance with the focus drive signal Fc, the spot diameter of the main beam is controlled to be constant even when the optical disc 200 is rotated in a wavy state (focus control).
Also, a tracking error signal Tr is generated by the return light of the sub beam, and a tracking drive signal Tr is generated by the loop filter 172 in a direction to cancel the error amount, whereby the objective lens 114 is optical disc in accordance with the tracking drive signal Tr. Since the optical disc 200 is rotated, the condensing point S2m by the main beam accurately follows the pregroove 202a (tracking control).
In the state in which the focus control and the tracking control are performed, the write signal generator 186A causes the current of the drive signal L2 to the second laser so that the return light indicated by the light amount signal La becomes the target value of the write level or the servo level. To operate. Thereby, the emission intensity of the laser beam from the second laser is controlled so as to become the target value of the write level or the servo level (power control).
As a result of executing the focus control, the tracking control, and the power control in this way, as shown in FIG. 3, pits 202P are formed in the pregroove 202a at lengths and intervals corresponding to the data. . In the reproduction of this data, first, the length and interval of the pits 202P are detected by the return light (light quantity signal La) of the laser light irradiated on the pregroove 202a, and secondly, the detection signal is decoded. This is executed by EFM demodulating by 182A and supplying to the host computer via the interface (I / F) 184.

<Image formation>
Next, an operation when an image is formed on the optical disc 200 will be described.
First, the control unit 130A instructs the servo circuit 144 to set the target value of the rotation speed, and secondly, the stepping motor 146 is rotated to move the pickup 100A to a point corresponding to the first line of the optical disc 200. Thirdly, the switch SW is closed between b and c by the signal R / I, and the focus drive signal that causes the error amount indicated by the focus error signal Fe to be constant at the value α with respect to the loop filter 171. Fc generation is instructed, and fourth, a target value necessary for image formation is set for the light signal target values of the first, second, and third lasers to the write signal generator 186A.
Here, the target value necessary for image formation is a binary value, that is, a light level sufficient to form a color change area of dots and a servo level at which the color change area is not formed. Accordingly, the three lasers are turned on at the write level or the servo level according to the dot data defining the density of the scanning dot.
On the other hand, the dot data is supplied from the host computer according to the scanning of the optical disk, and is accumulated in the internal buffer of the write signal generator 186A. In addition, the control unit 130A notifies the offset voltage generator 175 that the main scanning of the first row is the first time by the signal Tg, and the offset voltage generator 175 thereby notifies the first main scanning. The tracking signal Tg corresponding to is supplied to the tracking actuator 122 via the switch SW closed between bc. Thereby, the condensing points S1m, S2m, and S3m with respect to the optical disc 200 are located in the first row of the dot matrix and corresponding to the first main scanning.

Here, when the control unit 130A detects that the reference line of the optical disc 200 has passed by the rising edge of the pulse of interest in the detection signal FG, the current value of the drive signals L1, L2, and L3 to the write signal generator 186A. In accordance with the dot data in one row and one column. The write signal generator 186A sets the current of the drive signals L1, L2, and L3 to a value corresponding to the write level if the dot data in one row and one column indicates “black”, while indicating “white”. If it is, the value corresponding to the servo level. As a result, the first writing is performed on the dots of 1 row and 1 column. At this time, the write signal generator 186A operates the currents of the drive signals L1, L2, and L3 so that the return light intensity indicated by the hold signal LLa becomes the target value of the write level or the servo level. The point will be described later.
Subsequently, when the control unit 130A detects that the optical disk 200 has been rotated by an angle corresponding to one column of the dot matrix by the rising edge of the multiplied signal of the detection signal FG, the control unit 130A determines 1 for the write signal generator 186A. An instruction is given to output drive signals L1, L2, and L3 corresponding to the dot data in the two rows. As a result, the first writing is performed for the dots in the first row and the second column. Similarly, from the first row and the third column to the first row and the nth column, writing corresponding to the corresponding dot data is performed every time the writing is rotated by an angle corresponding to one column. As a result, the first main scan is completed for the dot located in the first row.

Next, when detecting that the reference line has passed again, the control unit 130A notifies the offset voltage generator 175 that the main scanning of the first row is the second time, and the offset voltage generator 175 A tracking signal Tg corresponding to the second main scanning is supplied to the tracking actuator 122. Thereby, the condensing points S1m, S2m, and S3m with respect to the optical disc 200 are located at the point corresponding to the second main scanning in the first row of the dot matrix. At the same time, the control unit 130A instructs the write signal generator 186A to output the drive signals L1, L2, and L3 corresponding to the dot data in the first row and the first column again. As a result, the second writing is performed even for the dots in the first row and the first column.
Similarly, from the 1st row and the 2nd column to the 1st row and the nth column, writing corresponding to the corresponding dot data is performed every time the writing is rotated by an angle corresponding to one column. As a result, the second main scanning is completed for the dots located in the first row, and the dot formation in the first row is completed.

Subsequently, the control unit 130A rotates the stepping motor 146 to move the pickup 100A to the outer peripheral side by a distance (0.1 mm) corresponding to one row, and to the offset voltage generator 175 in the second row. The signal Tg notifies that the main scanning is first time. As a result, the condensing points S1m, S2m, and S3m with respect to the optical disc 200 are located in the second row of the dot matrix and corresponding to the first main scan. When the control unit 130A detects the passage of the reference line, the control unit 130A instructs the write signal generator 186A to output the drive signals L1, L2, and L3 corresponding to the dot data of 2 rows and 1 column, Similarly, a drive signal corresponding to dot data from 2 rows and 2 columns to 2 rows and n columns is instructed each time the drive signal is rotated by an angle corresponding to one column. As a result, the first main scan is completed for the dot located in the second row.
When the control unit 130A detects that the reference line has passed again, the control unit 130A notifies the offset voltage generator 175 that the main scanning of the second row is the second time. The condensing points S1m, S2m, and S3m with respect to are located in the second row of the dot matrix and corresponding to the second main scan. At the same time, the control unit 130A instructs the write signal generator 186A to output a drive signal corresponding to the dot data of 2 rows and 1 column again, and so on. A drive signal corresponding to the dot data of the row is instructed each time the drive signal is rotated by an angle corresponding to one row. As a result, the second main scanning is completed for the dots located in the second row, and the dot formation in the second row is completed.
Thereafter, the same operation is repeated from the third row to the final m-th row, and the image formation by the dot matrix of m rows and n columns is completed.

Here, consider the case where the letter “A” is formed as an image on the optical disc 200 as shown in FIG. As described above, when the image resolution is 250 dpi, the size of one dot is 0.1 mm square.
Further, if the condensing points S1m, S2m, and S3m have a diameter (spot diameter) of 10 μm and a center distance of about 17 μm, the area of the portion that changes in color in the first main scanning (1) is 1 dot. The share will be 30%. Furthermore, in the present embodiment, the main scanning is performed twice, and the second main scanning (2) does not overlap the discoloration region caused by the first laser light irradiation, so the second main scanning (2 ), The ratio of the area that changes color in 1 dot is 30%. Eventually, in this embodiment, according to this embodiment, the rate of color change in one dot reaches 60% in total, and an image having a high dot density ratio can be formed as shown in the enlarged view of FIG. In addition, since the number of times of main scanning for one dot is “2”, the time required for image formation is also reduced to about １ ／ compared with the case of performing main scanning six times for one row using one laser. Can be shortened.

  In the description of the embodiment, the case where characters such as characters and symbols are formed as binary images has been described. However, the shading of the dots is defined by 3-bit dot data, and the first and second main characters are defined. In scanning, by individually controlling the drive signals L1, L2, and L3, it is also possible to express seven levels of gradation from “0” to “6” as shown in FIG. For example, when forming a dot of gradation “3”, in the first main scan (1), the drive signals L1 and L3 are set to the servo level, the drive signal L2 is set to the write level, and the second main scan (2 ), The drive signal L2 may be the servo level, and the drive signals L1 and L3 may be the write level. As for gradation display, a color-change region may be formed by irradiating laser light at a light level only during a period corresponding to the density in a period of scanning dots with laser light.

<First Embodiment: Various Controls During Image Formation>
Next, details such as power control and focus control for the optical disc 200 will be described.
When the recording layer is irradiated with light level laser light for image formation, the light amount signal La indicating the return light has a maximum peak in the portion K1 immediately after the light level irradiation, as shown in FIG. As shown in the portion K2, it gradually decreases. For this reason, it is considered that the hatched portion in the figure is the energy used to change the color of the recording layer. Here, the energy for discoloration does not always become a stable value, but fluctuates according to various situations, so that the shape of the shaded portion changes each time. Accordingly, when the return light corresponding to the light level is used at the time of image formation, there is a possibility that power control and focus control become unstable.
Furthermore, when “black” dots must be continuously formed in a certain row, irradiation at the light level is continued, so that power control and the like are considered to become even more unstable.
Therefore, in this embodiment, servo-level laser light is forcibly irradiated periodically regardless of dot data, and power control and focus control are performed based on the return light.

Specifically, as shown in FIG. 9, the control unit 130A periodically outputs the sampling pulse Sp. When the sampling pulse Sp is output, the control unit 130A relates the dot data to the write signal generator 186A. The drive signal L2 is forcibly set to a value corresponding to the servo level, while the drive signals L1 and L3 are instructed to have zero current values.
For this reason, as shown in FIG. 9, even when the color change period is for forming the color change region, when the sampling pulse Sp is output, the drive signal L2 is output at the servo level, while the drive signal L1 is output. , L3 is output at zero (off level). Therefore, since the first and third lasers are turned off during the output period of the sampling pulse Sp, the light amount signal La corresponds to the servo level and purely shows only the return light component from the second laser. The light amount signal La is held by the sampling & hold circuit 165 and fed back to the write signal generator 186A as the hold signal LLa.
Thereby, the write signal generator 186A can know the return light when the second laser irradiates the laser with the servo level intensity by the hold signal LLa.

When the intensity of the laser beam from the second laser is set to the servo level, the write signal generator 186A drives the drive signal L2 in the direction in which the return light (its intensity) indicated by the hold signal LLa becomes the servo level target value. Manipulate the current. Here, the case where the intensity of the laser beam from the second laser is set to the servo level means that the sampling pulse Sp in the colorless period (for example, the scanning period of white dots) and the color change period (for example, the scanning period of black dots). Is a period during which is output.
On the other hand, the write signal generator 186A uses the function having the return light indicated by the hold signal LLa as an argument to return light at the write level when the intensity of the laser beam from the second laser is set to the write level. And the current of the drive signal L2 is manipulated in a direction in which the estimated value becomes the target value of the light level. Here, the case where the intensity of the laser beam from the second laser is set to the light level is a period in which the sampling pulse Sp is not output in the discoloration period.
By operating the current to the drive signal L2, the intensity of the second laser is set to the servo level / light level target value in the discoloration period, and to the servo level target value in the colorless period. Therefore, each is appropriately controlled.

By the way, although the return light is not detected about the 1st and 3rd laser, since it is integrated in the same semiconductor chip with the 2nd laser, it is thought that it has the almost same characteristic as the 2nd laser. Therefore, the intensity of the first and third lasers can be indirectly controlled from the return light from the second laser without directly detecting the return light.
Specifically, the write signal generator 186A indicates the hold signal LLa when the intensity of the laser beam from the first (third) laser is set to the servo level in the period during which the sampling pulse Sp is not output in the colorless period. Laser light from the first (third) laser during the period when the sampling pulse Sp is not output during the discoloration period while operating the current of the drive signal L1 (L3) in the direction in which the return light that is generated becomes the servo level target value. Is set to the light level, the current of the drive signal L1 (L3) is operated in a direction that is an estimated value from the hold signal LLa and the estimated value of the return light at the light level becomes the target value of the light level. Note that the write signal generator 186A unconditionally sets the current value of the drive signal L1 (L3) to zero during the period in which the sampling pulse Sp is output, as described above.
By the current operation to the drive signals L1 and L3, the intensities of the first and third lasers are appropriately controlled so that the return values of the second laser become the servo / write level target values. become.

Further, the focus error signal Fe is sampled by the sampling & hold circuit 161 at the rising timing of the sampling pulse Sp, held, and supplied to the loop filter 171. Here, when image formation is instructed by the signal R / I, the loop filter 171 generates the focus drive signal Fc in a direction in which the error indicated by the held focus error signal Fe becomes constant at α, This is supplied to the focus actuator 121. Therefore, according to the present embodiment, the diameters of the condensing points S1m, S2m, and S3m can be stably maintained at approximately 10 μm regardless of the length of the discoloration period.
As described above, according to the first embodiment, the irradiation with the servo level intensity is periodically performed regardless of the dot data. Therefore, the power control and the focus control are performed at the time of image formation as in the data recording. Effectiveness can be ensured.
Note that it is desirable that the output period of the sampling pulse Sp be as short as possible on the condition that the time required for executing the power control and the focus control is secured, and the influence on the formed image is reduced.

<Application example of the first embodiment>
In the first embodiment, the condensing points S1m, S2m, and S3m are arranged in the radial direction of the optical disc 200. However, since the distance between them is about 17 μm, a slight gap is generated even if the diameter is increased to 10 μm. As a result, the contrast ratio decreases accordingly.
Therefore, the lens array 102 may be rotatable as indicated by an arrow in FIG. 2 around the emission point of the second laser in parallel with the incident surface of the polarization beam splitter 111.
For example, as shown in FIG. 10A, when the laser array 102 is rotated so that the discoloration areas do not overlap by the main scanning by the condensing points S1m, S2m, and S3m, there is no gap between the adjacent discoloration areas. Thus, an image with a higher contrast ratio can be formed.
Further, for example, as shown in FIG. 10B, when the laser array 102 is rotated so that the main scans at the condensing points S1m, S2m, and S3m coincide with each other, the area that changes in color by one main scan is reduced. However, since the intensity of the laser beam applied to the same region is substantially tripled, it is possible to increase the rotation speed by a factor of three. The time required can be reduced to 1/3.
In the first embodiment, the number of lasers integrated by the laser array 102 is “3”, but it may be two or more. In addition, although the laser that acquires the servo level is the second laser at the center in the laser array 102, for example, when the number of lasers integrated by the laser array 102 is “4”, the second or third laser near the center is used. It is also good.

Second Embodiment
Next, the configuration of the optical disc apparatus according to the second embodiment of the present invention will be described. FIG. 11 is a block diagram showing the configuration of the optical disc 10B according to the second embodiment, and FIG. 12 is a block diagram showing the configuration of the pickup and its control circuit.
The optical disk device 10B shown in these drawings has a data recording function for recording data on a DVD / CD (-R) as the optical disk 200 and an image forming function for forming an image. For this reason, each of the pickup 100B, the control unit 130B, the pickup control circuit 150B, the decoder 182B, and the write signal generator 186B in the optical disc apparatus 10B is a DVD system corresponding to the corresponding part of the optical disc apparatus 10A according to the first embodiment. A function is added.
In particular, with respect to the pickup 100B, as shown in FIG. 12, a DVD laser 102D that emits a laser beam having a wavelength of about 650 nm in accordance with the drive signal LD and a laser beam having a wavelength of about 780 nm are driven by the drive signal L−. And a CD laser 102 </ b> C that emits light in accordance with C.
In the optical system 110B, the laser beam from the laser 102C passes through the diffraction grating 104C, and then is reflected by the polarization beam splitter 111C in a right angle direction. The laser beam from the laser 102D passes through the diffraction grating 104D, and then is polarized. The light is reflected by the beam splitter 111D in a right angle direction and synthesized with the laser light from the laser 102C. That is, in the second embodiment, two lasers are combined to increase the light intensity, and accordingly, the rotational speed is increased to shorten the time required for image formation.

  The objective lens 114 </ b> B is an image formation-dedicated lens that condenses the laser light having a wavelength of about 650 nm and the laser light having a wavelength of about 780 nm at substantially the same point on the optical disc 200. Although not shown, at the time of DVD / CD data recording / reproduction, it is switched to an objective lens (bifocal lens) dedicated to recording / reproduction. This is because the DVD recording surface is generally located at a point deeper by 0.6 mm from the disk surface, whereas the CD recording surface is located at a point deeper by 1.2 mm from the disk surface. This is because the laser beam having a wavelength of 650 nm and the laser beam having a wavelength of 780 nm according to the latter need to be condensed at different points, and the image forming objective lens 114B that focuses at the same point is properly used. It is necessary to use it.

In FIG. 11, the control unit 130B alternately outputs a sampling pulse Sp-D for DVD and a sampling pulse Sp-C for CD. In response to this, the sampling and holding circuit 166 in FIG. 12 samples the light amount signal La at the rising edge of the sampling pulse Sp-D, holds it until the next rising edge of the sampling pulse Sp-D, and holds the hold signal La. -D is supplied to the write signal generator 186B.
Similarly, the sampling and holding circuit 167 samples the light amount signal La at the rising edge of the sampling pulse Sp-C, holds it until the next rising edge of the sampling pulse Sp-C, and writes the hold signal La-C. The signal generator 186B is supplied.
Further, in the second embodiment, the offset voltage generator 175 detects whether the main scanning of the dots located in the same row is the first to sixth times based on the signal Tg supplied from the control unit 130A. Depending on the detection, a tracking drive signal Ts having a different DC voltage is output, and the locus of the condensing point for scanning the same row is made different for each main scan.
On the other hand, in the case of DVD recording, the write signal generator 186B in FIG. 11 drives the drive signal LD to the DVD laser 102D so that the return light indicated by the light quantity signal La becomes the target value for data recording. In the case of CD recording, the current of the drive signal LC to the CD laser 102C is manipulated so that the return light indicated by the light amount signal La becomes the target value for data recording, and the image In the case of formation, the currents of the drive signals LD and LC are controlled so that the return light indicated by the light amount signal La, the hold signals La-D and La-C becomes the target value for image formation. Is.

<Optical disk>
As described above, in the second embodiment, the laser beam with a wavelength of 650 nm for DVD and the laser beam with a wavelength of 780 nm for CD are combined and condensed at substantially the same point during image formation. On the other hand, the DVD recording layer absorbs light near the wavelength of 650 nm and changes color, and the CD recording layer absorbs light near the wavelength of 780 nm and changes color. For this reason, even if the DVD or CD recording layer is irradiated with the combined light of the laser beam for DVD and the laser beam for CD, only the light of either wavelength is absorbed. It is conceivable that the degree of discoloration is less than the intensity. On the other hand, when forming an image on the recording surface, the image formation area is limited to the unrecorded area of the recording layer, so if the data capacity to be recorded is large, the user forms an image in an arbitrary area. There is also the disadvantage that it cannot be done.

Therefore, in the second embodiment, a separate photosensitive layer is provided on the side of the label surface opposite to the recording surface, and an image is formed by irradiating this photosensitive layer with laser light. FIG. 13 is a schematic cross-sectional view showing the configuration of the optical disc 200.
The optical disc 200 shown in this figure is a CD (-R, -RW) system, and when viewed from the recording surface, a protective layer 201, a recording layer 202, a reflective layer 203, a protective layer 204, and a photosensitive layer 205 are shown. The protective layer 206 is laminated in this order. Among these layers, the recording layer 202 is formed with a pre-groove 202a and a land 202b. Note that, when the pregroove 202a is viewed from the recording surface, as shown in FIG. 4, the shape spiraled clockwise from the inner circumference side toward the outer circumference side is as described above.
On the other hand, the photosensitive layer 205 includes a dye that changes color by absorbing light having a wavelength of 650 nm as shown by a characteristic M1 in FIG. 14 and a dye that changes color by absorbing light having a wavelength of 780 nm as shown by a characteristic M2. It is a mixed layer. For this reason, the photosensitive layer 205 is efficiently discolored with respect to the combined light of the laser beam having a wavelength of 650 nm and the laser beam having a wavelength of 780 nm. As the photosensitive layer 205, as shown by the characteristic M3, a dye that changes color by absorbing light with a wavelength of 650 nm to 780 nm in a wide band may be used.

When an image is formed on the optical disc 200, as shown in FIG. 13, the surface (label surface) on the protective layer 206 side is set so as to face the objective lens 114B. Then, as in the first embodiment, the dots constituting the image are defined as shown in FIG. 6, and these dots are mainly aligned in the row direction by irradiation with laser light when the optical disc 200 is rotated. On the other hand, every time a dot for one row is formed, the scanning point in the column direction is sub-scanned by moving the laser beam irradiation point by one row from the inner circumference side to the outer circumference side. Furthermore, a target image is formed by irradiating laser composite light in accordance with dot data during such scanning to form a color-change region sequentially.
However, unlike the first embodiment in which there are three condensing points, in the second embodiment there is only one condensing point, so images of the same quality are provided for dots located in the same row. If it is going to form, it is necessary to change the locus of the condensing point and perform main scanning six times so that the discolored regions do not overlap. However, since the intensity of the condensing point is double, the rotation speed of the optical disc 200 can be doubled as compared with the first embodiment. For this reason, the time required for image formation is 2/3 times that of the first embodiment and is slightly reduced. However, the time required for image formation can be reduced to ½ compared with the case of using one laser.

On the other hand, when data is recorded on the optical disc 200, the optical disc 200 is set so that the recording surface faces downward, and rotated, contrary to FIG. 13, and the condensing point of the laser beam by the laser beam 102C is the pregroove. The target data is recorded by controlling the tracking so as to follow along 202a and controlling the drive signal L-C according to the data. This also applies to the case where data is recorded on a CD-type optical disk such as a CD-R or CD-RW that does not have the photosensitive layer 205.
When the optical disk 200 is a DVD system such as a DVD-R, tracking control is performed so that the condensing point of the laser light by the laser light 102D follows along the pregroove, and driving is performed according to data to be recorded. The target data is recorded by controlling the signal L-D.
In FIG. 13, a CD-type optical disc has been described as an example, but it is needless to say that a similar photosensitive layer 205 may be provided on the label surface of a DVD-type optical disc.

<Second Embodiment: Various Controls During Image Formation>
In the second embodiment, an image is formed by irradiating the photosensitive layer 205 provided on the label surface with light-level composite light. The return light when the light-level laser composite light is irradiated varies in various situations. Since the points that vary according to the same are the same as in the first embodiment, various controls using return light at the light level may become unstable.
Therefore, in the second embodiment, as shown in FIG. 13, the control unit 130B includes the sampling pulse Sp-D for detecting the return light of the DVD laser La-D and the CD laser La-C. When the sampling pulse Sp-C for detecting the return light is output mutually exclusively and periodically, and when the former sampling pulse Sp-D is output, the current value of the drive signal LD regardless of the dot data Is forced to a value corresponding to the servo level, and the write signal generator 186A is instructed to make the current value of the drive signal L-C zero, while the latter sampling pulse Sp-C is output. Regardless of the dot data, the current value of the drive signal LC is forced to a value corresponding to the servo level and the current value of the drive signal LD is zero. It instructs the write signal generator 186A to cause.
For this reason, as shown in FIG. 15, even during the color change period, when the sampling pulse Sp-D is output, the drive signal LD is output at the servo level, while the drive signal LC is Is output at the off level. Even during the color change period, when the sampling pulse Sp-C is output, the drive signal L-C is output at the servo level, while the drive signal LD is output at the off level.
Accordingly, the hold signal La-D purely shows only the component of the return light from the DVD laser 102D corresponding to the servo level, while the hold signal La-C returns from the CD laser 102C corresponding to the servo level. Only the light component is shown purely and fed back to the write signal generator 186B.
Thus, the write signal generator 186B knows only the return light when the DVD laser 102D irradiates the laser with the servo level intensity by the hold signal La-D, and the CD laser 102C has the servo level. Only the return light when the laser is irradiated with the intensity can be known by the hold signal La-C.

The write signal generator 186B determines the intensity of the laser beam from the DVD laser 102-D in the period in which the sampling pulse Sp-D is output and the period in which the sampling pulse Sp-C is not output in the colorless period. When the servo level is set, the current of the drive signal L-D is manipulated in a direction in which the return light indicated by the hold signal La-D becomes the target value of the servo level for DVD. On the other hand, the write signal generator 186B holds the hold signal when the intensity of the laser beam from the laser 102-D is set to the light level in the period in which neither of the sampling pulses Sp-D and Sp-C is output during the color change period. Using the function having the return light indicated by La-D as an argument, the return light at the light level by the laser 102D is estimated, and the drive signal L- is directed so that this estimated value becomes the target value of the DVD light level. Manipulate the current of D.
As a result, the intensity of the laser beam from the DVD laser 102D becomes zero during the output period of the sampling pulse Sp-C, but during the discoloration period, the target value of the servo level / write level can be set to a colorless period. Thus, the servo level target value is appropriately controlled.

Similarly, the write signal generator 186B performs laser light from the CD laser 102-C in the period in which the sampling pulse Sp-C is output and the period in which the sampling pulse Sp-D is not output in the colorless period. Is set to the servo level, the current of the drive signal L-C is manipulated so that the return light indicated by the hold signal La-C becomes the target value of the servo level for CD. On the other hand, the write signal generator 186B holds the hold signal when the intensity of the laser beam from the laser 102-C is set to the light level in the period in which neither of the sampling pulses Sp-D and Sp-C are output during the color change period. Using the function having the return light indicated by La-C as an argument, the return light at the light level by the laser 102C is estimated, and the drive signal LC is applied in the direction in which the estimated value becomes the CD light level target value. Manipulate the current.
As a result, the intensity of the laser beam from the CD laser 102C is zero during the output period of the sampling pulse Sp-D, but the target value of the servo level / light level is set to the target value of the servo level / light level during the color change period. Thus, the servo level target value is appropriately controlled.
As described above, since the intensity of the laser beams by the lasers 102C and 102D is individually controlled, the intensity of these combined lights is also appropriately controlled.

Further, the focus error signal Fe is sampled by the sampling & hold circuit 161 at the rising timing of the sampling pulse Sp-C, and is held and supplied to the loop filter 171. Therefore, as in the first embodiment, The diameter of the condensing point of the synthesized light can be stably maintained at approximately 10 μm regardless of the length of the discoloration period.
Note that the sampling instruction in the sampling and holding circuit 161 may be Sp-D instead of the sampling pulse Sp-C, or a logical sum signal of both.

  As described above, according to the second embodiment, the irradiation with the servo level intensity is periodically performed regardless of the dot data. Therefore, the power control and the focus control are effectively performed at the time of image formation as in the data recording. It becomes possible to ensure the sex.

<Application Example of Second Embodiment>
In the second embodiment, the color of the photosensitive layer 205 is changed by the combined light of the DVD laser light and the CD laser light during image formation. However, three or more laser lights may be combined. For example, as the third laser, a violet semiconductor laser used for recording a next-generation disk may be used. In the case of using such a violet semiconductor laser, the photosensitive layer 205 may be mixed with the violet absorbing dye, or a broadband dye having an absorption up to the violet may be used.
Further, an image may be formed on the label surface of the optical disc 200 having the structure shown in FIG. 13 by using the optical disc apparatus 10A according to the first embodiment. Since the optical disc apparatus 10A is assumed to be a CD-type optical disc, the light absorptivity at a wavelength of 650 nm in the photosensitive layer 205 at this time is unnecessary.

<Image Formation Using Tracking Control in First and Second Embodiments>
In the first and second embodiments described above, since the dots of the optical disk are sub-scanned by the feed of the pickup 100A (100B), the tracking control for following the pregroove 202a (see FIG. 13) is performed by b− in the switch SW. It was invalidated by closing between c. However, even when laser light is irradiated from the label surface, such tracking control may be possible.
In such a case, the position of the condensing point of the laser beam may be controlled by using tracking control together, and the intensity of the laser beam may be controlled according to the dot data corresponding to the control position.
However, in the first embodiment, attention should be paid only to the condensing points S2a and S2b (see FIG. 3) of the sub beam by the second laser. For this purpose, for example, a sampling and holding circuit is provided in front of the loop filter 172, and the tracking error signal Fe is sampled and held by the sampling signal Sp, and the loop filter 172 cancels the error indicated by the holding signal. A configuration in which the tracking drive signal Tr is generated in the direction may be adopted so that the hold signal does not include return light components from the first and third lasers.
Note that, when the laser beam is irradiated from the label surface, the concavo-convex relationship between the pre-groove 202a and the land 202b is reversed, and the tracking control in this case is control for following the land 202b. Further, when the spiral direction of the pregroove 202a is viewed from the label surface, it is opposite to that in FIG. 4 (that is, counterclockwise with the inner peripheral side as the start point and the outer peripheral side as the end point). It is also necessary to reverse the direction. However, if the optical disk 200 is made to follow from the outer periphery side toward the inner periphery side, the rotation direction of the optical disk 200 can be the same.

1 is a block diagram showing a configuration of an optical disc apparatus according to a first embodiment of the present invention. It is a block diagram which shows the structure of the pick-up in the same optical disk apparatus, and its control circuit. It is a figure for demonstrating the positional relationship of the condensing point in the optical disk device. It is a top view for demonstrating the pre-groove of the same optical disk. It is a top view which shows the detection surface of the light receiving element in the pickup. It is a top view for demonstrating the dot of the same optical disk. It is a figure which shows an example of the image formed with the optical disk apparatus. It is a figure which shows an example of a gradation display with the same optical disk apparatus. 4 is a timing chart for explaining the operation of the optical disc apparatus. (A) And (b) is a top view which shows the arrangement | sequence of the condensing point applicable respectively in the same optical disk device. It is a block diagram which shows the structure of the optical disk apparatus based on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the pick-up in the same optical disk apparatus, and its control circuit. It is a schematic sectional drawing which shows the structure of the optical disk applied to the same optical disk apparatus. It is a figure which shows the photosensitive characteristic of the photosensitive layer in the disk. 4 is a timing chart for explaining the operation of the optical disc apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10A, 10B ... Optical disk apparatus, 100A, 100B ... Pickup, 102 ... Laser array, 102D, 102C ... Laser (1st laser, 2nd laser), 108 ... Light receiving element (detection means), 130 ... Control part (control means) , 150A, 150B ... pickup control circuit, 171, 172 ... loop filter, 200 ... optical disc, 202 ... recording layer, 202a ... pre-groove, 205 ... photosensitive layer

Claims (1)

An optical disc having a recording surface and a label surface, on which an image is formed by irradiating a combined light of a laser beam having a first wavelength and a laser beam having a second wavelength different from the first wavelength from the label surface Because
On the recording surface,
A recording layer that changes color by irradiation with the laser light of the first or second wavelength;
A reflective layer positioned below the recording layer,
On the label surface,
An optical disc comprising: a photosensitive layer that is positioned above the reflective layer and has photosensitivity to light of the first and second wavelengths.

Images