JP2005174383A - Method for removing stray light offset and optical disc apparatus - Google Patents

Abstract

A stray light offset removing method and an optical disc apparatus that appropriately remove stray light offset even when the movable range of an optical pickup is narrow as in a thin drive.
When the voltage of the focus drive signal is gradually increased and output, the optical pickup moves in a direction approaching the optical disk, and in the moving process, an S-shaped signal 33 due to reflection on the surface of the optical disk, the reflection surface of the optical disk An S-shaped signal 34 due to reflection at is detected.
The voltage Va is stored as Va as the voltage of the focus drive signal when the S-shaped signal 34 is detected. Next, based on the stored voltage value Va, Vb which is the voltage value of the focus drive signal corresponding to the position of the optical pickup that is not affected by the reflection of the surface of the optical disc 1 is calculated, and the optical pickup is located at that position. To remove stray light offset.
[Selection] Figure 3

Description

  The present invention relates to a stray light offset removal method and an optical disc apparatus when information on an optical disc is recorded and reproduced by an optical pickup.

  As optical disc devices, audio CDs, CD-ROMs, CD-R / RWs, DVDs, and the like have already been put into practical use, and application to various fields and development for high performance are being actively conducted. . Particularly recently, with the rapid market expansion of personal computers, the penetration rate of built-in optical disk devices in personal computers has increased.

  Here, the configuration of the optical disc apparatus will be described with reference to FIG.

  FIG. 1 is a block diagram of a pickup control unit of an optical disc apparatus according to an embodiment of the present invention. In FIG. 1, 1 is an optical disk, 2 is a pickup module, 3 is a spindle motor, 4 is an optical pickup, 5 is a carriage, 6 is a feed unit, 7 is a feed motor, 8 is an analog signal processing unit, 9 is a servo processing unit, Reference numeral 10 denotes a motor driving unit, 11 denotes a digital signal processing unit, 12 denotes a laser driving unit, and 13 denotes a controller.

  The operation of the pickup control unit in the conventional technology configured as described above will be described. In FIG. 1, a pickup module 2 moves a spindle motor 3 for rotating an optical disc 1, an optical pickup 4 for reading an information signal of the optical disc 1, and a carriage 5 on which the optical pickup 4 is mounted in the radial direction of the optical disc. And a feed section 6 for the purpose. The analog signal processing unit 8 generates a focus error signal and a tracking error signal based on a signal output from an optical sensor (not shown) in the optical pickup 4 in the carriage 5 provided in the pickup module 2. To the servo processing unit 9.

  The focus error signal indicates a shift in the focal direction between a light beam spot emitted from an objective lens (not shown) provided in the optical pickup 4 and the recording surface of the optical disc 1. The tracking error signal indicates a deviation in the optical disc radial direction between the light beam spot and the information track of the optical disc 1. Further, the analog signal processing unit 8 extracts a low frequency component of the tracking error signal to generate a lens position signal indicating a relative positional relationship between the objective lens and the carriage 5 and outputs the lens position signal to the motor driving unit 10.

  The servo processing unit 9 includes an ON / OFF circuit, an arithmetic circuit, a filter circuit, an amplifier circuit, and the like. The servo processing unit 9 performs focus / tracking control of the objective lens so that the light beam spot follows the information track of the optical disc 1, and further a tracking error signal. Feed control is performed so that the objective lens maintains a substantially neutral position using the low-frequency component. The feed unit 6 includes a feed motor 7, a gear (not shown), a screw shaft (not shown), and the like. The carriage 5 is moved by rotating the feed motor 7. Are output periodically. The controller 13 controls the entire servo unit configured as described above.

  FIG. 5 is a diagram illustrating a focus error signal and a focus drive signal that accompany the movement of the optical pickup.

FIG. 5A shows a focus error signal generated when the optical pickup is moved with respect to the optical disc, and FIG. 5B shows a focus drive signal at that time.

  When the optical pickup 4 is brought close to the optical disc 1, when the condensing point of the laser light 30 coincides with the surface 31 of the optical disc 1, an S-shaped signal 33 is obtained by surface reflection. Further, when the condensing point of the laser beam 30 coincides with the reflection surface 32 of the optical disc 1, an S-shaped signal 34 is obtained by reflection on the reflection surface.

  In an optical disc apparatus, it is known that stray light is generated due to scattering by optical components constituting an optical pickup, and a signal in which a stray light component is added as an offset is output. Therefore, an offset due to stray light (hereinafter referred to as “stray light”). It is necessary to remove "offset"). This stray light offset is removed by outputting a focus drive signal at a preset voltage so that the condensing point of the laser light does not reach the surface of the optical disc in order to avoid the influence of the S-shaped signal due to the surface reflection, and the optical pickup The position is sufficiently kept away from the optical disc.

Techniques relating to the removal of stray light offset are described in Patent Document 1 and Patent Document 2, for example.
Japanese Patent Laid-Open No. 10-105997 JP 2000-339737 A

  In recent years, a drive having a thickness of 9.5 mm has been developed as a drive in an optical disc apparatus, and the drive is becoming thinner. As the drive becomes thinner, the movable range of the optical pickup becomes narrower, and it is impossible to secure a space enough to move the position of the optical pickup sufficiently away from the optical disk. Therefore, there is a problem that erroneous adjustment of the stray light offset is likely to occur due to the influence of the S-shaped signal due to the surface reflection. When such an erroneous adjustment of the stray light offset occurs, it is difficult to accurately obtain a control signal such as a focus error signal, and control is not performed correctly.

  The present invention has been made to solve the above problems, and even when the movable range of the optical pickup is narrow like a thin drive, the stray light offset can be appropriately removed, and the control is accurately performed. It is an object of the present invention to provide a stray light offset removal method and an optical disc apparatus that can be performed in the same manner.

  In order to solve the above-mentioned problems, the present invention is a method for removing stray light offset generated by stray light generated in an optical pickup, which outputs a focus drive signal to move the optical pickup relative to the optical disk, and reflects the optical disk. The voltage of the focus drive signal when the S-shaped signal is generated in the focus error signal by the surface is stored as a reference voltage, and the voltage of the focus drive signal in the region not affected by the reflected light from the optical disk is calculated based on the reference voltage. The stray light offset removing method is characterized in that the stray light offset is removed at the position where the optical pickup is calculated and moved.

The focus drive signal voltage when the S-shaped signal is generated in the focus error signal by the reflecting surface of the optical disc is stored as a reference voltage, and the focus drive signal for the region not affected by the reflected light from the optical disc based on the reference voltage The stray light offset can be removed without being affected by the reflected light even when the focal position of the laser light is within the optical disk. Therefore, stray light offset can be removed without sufficiently moving the optical pickup away from the optical disk, and stray light offset can be properly removed even when the movable range of the optical pickup is narrow, such as a thin drive.

  According to the present invention, it is possible to remove the stray light offset without moving the optical pickup sufficiently away from the optical disk, and appropriately remove the stray light offset even when the movable range of the optical pickup is narrow as in a thin drive. be able to.

  The invention according to claim 1 of the present invention is a method for removing stray light offset generated by stray light generated in an optical pickup, and outputs a focus drive signal to move the optical pickup relative to the optical disk, and the reflection surface of the optical disk. Stores the voltage of the focus drive signal when the S-shaped signal is generated in the focus error signal as a reference voltage, and calculates the voltage of the focus drive signal in the region not affected by the reflected light from the optical disk based on the reference voltage Then, the stray light offset removing method is characterized in that the stray light offset is removed at the position where the optical pickup is moved.

  The focus drive signal voltage when the S-shaped signal is generated in the focus error signal by the reflecting surface of the optical disc is stored as a reference voltage, and the focus drive signal for the region not affected by the reflected light from the optical disc based on the reference voltage The stray light offset can be removed without being affected by the reflected light even when the focal position of the laser light is within the optical disk. Therefore, stray light offset can be removed without sufficiently moving the optical pickup away from the optical disk, and stray light offset can be properly removed even when the movable range of the optical pickup is narrow, such as a thin drive.

  According to a second aspect of the present invention, in the stray light offset removing method according to the first aspect, the region that is not affected by the light reflected by the optical disk is located between the reflective surface and the surface of the optical disk. To do.

  This is because when the focal position of the laser light is between the disk surface and the reflecting surface, stray light offset can be performed without being affected by the reflected light.

  According to a third aspect of the present invention, in the stray light offset removal method according to the first aspect, the region that is not affected by the reflected light from the optical disk is defined in the optical disk thickness direction with respect to the reflective surface of the optical disk. The distance between the reflecting surface and the surface is within a range of 23% to 76%.

  Considering the focal length and numerical aperture of the optical member such as a lens in the pickup and the surface deflection of the optical disk, the distance between the reflection surface and the surface of the optical disk is 23% to This is because it is appropriate to make the area within the range of 76% not affected by the light reflected by the optical disk.

  According to a fourth aspect of the present invention, an actuator driving means for outputting a focus driving signal for moving the optical pickup with respect to the optical disc, and an S-shaped signal generated in the focus error signal by the reflecting surface of the optical disc are detected. S-shaped level detection means, a storage unit that stores the voltage of the focus drive signal when the S-shaped signal is generated as a reference voltage, and focus drive in an area that is not affected by reflected light from the optical disk based on the reference voltage An arithmetic unit for calculating the voltage of the signal, an offset detecting unit for measuring the offset voltage of the control signal when the focus drive signal is the calculated voltage, and an offset adjusting unit for adjusting the offset to remove the stray light offset It is an optical disc apparatus characterized by having.

  With this configuration, the focus drive signal voltage when the S-shaped signal is generated in the focus error signal by the reflecting surface of the optical disk is stored as a reference voltage, and the influence of the reflected light from the optical disk is determined based on the reference voltage. The voltage of the focus drive signal in the unaffected area can be calculated, and the stray light offset can be removed without being affected by the reflected light even when the focal position of the laser light is within the optical disc. Therefore, an optical disc apparatus capable of removing stray light offset without sufficiently moving the optical pickup away from the optical disc and capable of properly removing stray light offset even when the movable range of the optical pickup is narrow like a thin drive. Can be realized.

  According to a fifth aspect of the present invention, in the optical disk apparatus according to the fourth aspect, the region that is not affected by the light reflected by the optical disk is located between the reflective surface and the surface of the optical disk.

  This is because when the focal position of the laser light is between the disk surface and the reflecting surface, stray light offset can be performed without being affected by the reflected light.

  According to a sixth aspect of the present invention, in the optical disk apparatus according to the fourth aspect, the region that is not affected by the light reflected by the optical disk is defined in the thickness direction of the optical disk with respect to the reflective surface of the optical disk. The distance between the surface and the surface is in the range of 23% to 76%.

  Considering the focal length and numerical aperture of the optical member such as a lens in the pickup and the surface deflection of the optical disk, the distance between the reflection surface and the surface of the optical disk is 23% to This is because it is appropriate to make the area within the range of 76% not affected by the light reflected by the optical disk.

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

  FIG. 1 is a block diagram of an optical disc apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a recordable optical disk, 2 is a pickup module, and the pickup module 2 is irradiated with light on a spindle motor 3 that rotates the optical disk 1 variably or at a constant rotation, and the optical disk 1. Thus, the optical pickup 4 for recording predetermined information on the optical disc 1 or reading information based on the reflected light of the light irradiated on the optical disc 1, the carriage 5 on which the optical pickup 4 is mounted, and the carriage 5 with the radius of the optical disc 1. A feed unit 6 that is driven to reciprocate in a direction and a feed motor 7 that is a drive source of the feed unit 6 are fixed, and a small / thin optical disc apparatus is realized by such a configuration.

  In the present embodiment, each of the above members is mounted on the pickup module 2, but at least one of the members may be mounted and the other members may be mounted and fixed on a portion inside another optical disk device. Reference numeral 8 denotes an analog signal processing unit, 9 denotes a servo processing unit, 10 denotes a motor driving unit, 11 denotes a digital signal processing unit, 12 denotes a laser driving unit, and 13 denotes a controller.

  The operation of the optical disk apparatus configured as described above according to the embodiment of the present invention will be described. In FIG. 1, a pickup module 2 is used to move a spindle motor 3 for rotating an optical disk 1, an optical pickup 4 for reading an information signal of the optical disk 1, and a carriage 5 on which the optical pickup 4 is mounted in the radial direction of the optical disk. The feed unit 6 is configured.

  The feed unit 6 includes a feed motor 7, a gear (not shown), a screw shaft (not shown), and the like, and the carriage 5 moves between the inner periphery and the outer periphery of the optical disk 1 by rotating the feed motor 7. It is configured.

  The analog signal processing unit 8 generates a focus error signal and a tracking error signal based on a signal output from an optical sensor (not shown) in the optical pickup 4 in the carriage 5 configured in the pickup module 2. Output to the servo processing unit 9.

  The servo processing unit 9 is an A / D converter that converts the analog signal sent from the analog signal processing unit 8 into a digital signal, a memory that temporarily stores the digital signal converted by the A / D converter, and a memory An arithmetic circuit for calculating a recorded digital signal or a digital signal sent from an A / D converter by a predetermined method, a D / A converter for converting the digital signal calculated by the arithmetic circuit into an analog signal, etc. Thus, the filter signal processing and various calculation processes are performed by digital calculation so that the light beam spot follows the information track of the optical disc 1. For this reason, various parameter settings and sequence control can be flexibly performed by command from the controller 13.

  The servo processing unit 9 performs control for moving the objective lens mounted on the optical pickup 4 in the focus direction / tracking direction via the motor driving unit 10, transfer control for the feed unit 6, and rotation control for the spindle motor 3. Do. The rotation of the spindle motor 3 is controlled so that the linear velocity (CLV) is constant during recording of a CD or DVD, but the disk has a constant angular velocity (CAV) in order to obtain a data transfer rate that is as high as possible during reproduction. Thus, the rotation control of the spindle motor 3 is performed. Regarding the CAV mode, there are a plurality of rotational speed modes having different rotational speeds.

  During the reproduction operation, the optical pickup 1 is irradiated with light from the optical pickup 4, the reflected light from the optical disk 1 is received by a light receiving element (not shown), and the reproduction output from the optical pickup 4 according to the received light. A signal is input to the digital signal processing unit 11 via the analog signal processing unit 8.

  The digital signal processing unit 11 includes a data slicer, a data PLL circuit, a jitter measurement circuit, an error correction unit, a modulation / demodulation unit, a buffer memory, a laser control unit, and the like, and is effective for the host (HOST in the figure) side. It is transferred as data.

  During the recording operation, the data sent from the host is modulated by the digital signal processing unit 11, and the laser control unit sends a predetermined light source such as a laser (not shown) in the optical pickup 4 via the laser driving unit 12. A current is supplied, the light source is caused to emit light in a pulse shape, for example, and recording is performed on an information track of the optical disc 1. The controller 13 controls the entire optical disk apparatus configured as described above.

  Based on FIG. 2 and FIG. 3, an optical disc apparatus according to an embodiment of the present invention and a stray light offset removal method in the optical disc apparatus will be described.

  FIG. 2 is a flowchart of the stray light offset removal method. FIG. 3 is a diagram illustrating a focus error signal and a focus drive signal in stray light offset removal.

First, a focus drive signal is output, the optical pickup 4 is moved in a direction approaching the optical disc 1, and the S-shaped level of the focus error signal is measured for each step of the focus drive signal (S1). That is, as shown in FIG. 3B, when the voltage of the focus drive signal is gradually increased and output, the optical pickup 4 moves in the direction approaching the optical disc 1, and in the moving process, the state shown in FIG. As shown, an S-shaped signal 33 and an S-shaped signal 34 are detected.

  As shown in FIG. 5A, in the process in which the optical pickup 4 moves from the position (a) to the position (e), the S-shaped signal 33 is reflected by the reflection on the surface 31 of the optical disk 1 at the position (b). And an S-shaped signal 34 is generated by reflection at the reflecting surface 32 of the optical disc 1 at the position (d). Therefore, in the state where the focal position of the laser beam is between the surface 31 and the reflecting surface 32 of the optical disc 1 shown in (c), stray light offset can be performed without being affected by the reflected light.

  Further, considering that the laser beam has a focal depth determined by the focal length and numerical aperture of an optical member such as a lens in the pickup and the surface shake of the optical disc, the focal position of the laser beam is close to the surface 31 of the optical disc 1 or reflected. It is preferable to remove the vicinity of the surface 32. Specifically, when the laser beam is focused within a range of 23% to 76% of the distance between the reflecting surface 32 of the optical disc 1 and the surface 31 with respect to the reflecting surface 32 of the optical disc 1, If the stray light offset is removed within this range without being affected by the reflected light, erroneous adjustment of the stray light offset due to the influence of the reflected light from the optical disk 1 will not occur.

  Such a position of the optical pickup 4 can be obtained by the following procedure.

The voltage Va is stored as the voltage Va of the focus drive signal when the S-shaped signal 34 is detected (S2). Next, based on the stored voltage value Va, Vb, which is the voltage value of the focus drive signal corresponding to the position of the optical pickup 4 that is not affected by reflection by the surface 31 of the optical disc 1, is calculated (S3). This Vb is
Vb = Va− {distance from reflecting surface to surface × L ÷ DC sensitivity}
Is required. Here, the distance from the reflecting surface to the surface varies depending on the type of the optical disk, and is approximately 1.2 mm for CD and approximately 0.6 mm for DVD. The DC sensitivity is the amount of movement of the optical pickup 4 when 1 V is applied to the focus drive signal, and its unit is mm / V. L is a constant and determines the distance to which the focal position of the laser beam should move from the reflecting surface 32 of the optical disc 1. That is, when L is 0.23 to 0.76, the laser beam is focused within a range of 23% to 76% of the distance between the reflecting surface 32 and the surface 31 of the optical disc 1.

  Therefore, by dividing (distance from the reflecting surface 32 to the surface 1 × L) by the DC sensitivity, the voltage decreases with reference to the voltage of the focus drive signal when the S-shaped signal 34 is detected on the reflecting surface 32 of the optical disc 1. The voltage of the focus drive signal to be generated can be derived. A voltage obtained by subtracting the voltage of the focus drive signal to be reduced from the voltage Va of the focus drive signal when the S-shaped signal 34 by the reflecting surface 32 of the optical disc 1 is obtained becomes the voltage value Vb of the focus drive signal to be obtained.

  Next, the optical pickup 4 is moved to a position where the voltage value of the focus drive signal becomes Vb (S4). This means that in FIG. 3B, the voltage value of the focus drive signal is lowered to Vb. At this position, the offset voltage of the control signal such as the focus error signal and the tracking error signal is measured to remove the stray light offset (S5).

  FIG. 4 is a block diagram of an optical disc apparatus having a function of executing stray light offset removal processing.

  The movement of the optical pickup 4 in the direction of the optical disk 1 is performed by outputting a focus drive signal from the actuator drive means 21, and a focus error signal, A control signal such as a tracking error signal is generated. The S-shaped level is detected by the S-shaped level detecting means 23 with respect to the focus error signal, and information related to the S-shaped level is sent to the CPU 24.

  The CPU 24 stores the voltage of the focus drive signal when the S-shaped signal is generated as a reference voltage, and the voltage of the focus drive signal in an area not affected by the reflected light from the optical disk 1 based on the reference voltage. A calculation unit that outputs a focus drive signal to the actuator drive unit 21 via the servo control unit 27 and, as described above, the optical pickup 4 at a position not affected by the reflected light from the optical disc 1. To move.

  At this position, the offset voltage of the control signal such as the focus error signal and the tracking error signal is measured by the offset detecting means 25, and the offset is adjusted by the offset adding means 26 to remove the stray light offset.

  In the optical disc apparatus described above, the focus drive signal voltage Va when the S-shaped signal 34 is generated in the focus error signal by the reflecting surface 32 of the optical disc 1 is stored as a reference voltage, and the reflection by the optical disc 1 is performed based on this reference voltage. By calculating the voltage Vb of the focus drive signal in a region not affected by light, the stray light offset can be removed without being affected by the reflected light even when the focal position of the laser light is within the optical disc 1. . Therefore, stray light offset can be removed without sufficiently moving the optical pickup 4 from the optical disc 1, and stray light offset can be properly removed even when the movable range of the optical pickup is narrow, such as a thin drive. .

  INDUSTRIAL APPLICABILITY The present invention can be used as an optical disk device, and can realize an optical disk device capable of accurately removing stray light offset and accurately performing focus control even with a thin drive.

1 is a block diagram of a pickup control unit of an optical disc apparatus according to an embodiment of the present invention. Flow chart of stray light offset removal method Diagram showing focus error signal and focus drive signal in stray light offset removal Block diagram of an optical disc apparatus having a function of executing stray light offset removal processing The figure which shows the focus error signal and the focus drive signal accompanying the movement of the optical pickup

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Pickup module 3 Spindle motor 4 Optical pick-up 5 Carriage 6 Feed part 7 Feed motor 8 Analog signal processing part 9 Servo processing part 10 Motor drive part 11 Digital signal process part 12 Laser drive part 13 Controller 21 Actuator drive means 22 Control signal Generation means 23 S-shaped level detection means 24 CPU
25 Offset detecting means 26 Offset adding means 27 Servo control means 30 Laser light 31 Surface 32 Reflecting surface 33 S-shaped signal 34 S-shaped signal

Claims (6)

A method for removing stray light offset generated by stray light generated in an optical pickup, which outputs a focus drive signal to move the optical pickup relative to the optical disc, and an S-shaped signal is generated as a focus error signal by the reflecting surface of the optical disc. When the focus drive signal voltage is stored as a reference voltage, the focus drive signal voltage in a region not affected by the reflected light from the optical disk is calculated based on the reference voltage, and the optical pickup is moved to the position. A method for removing stray light offset, comprising: removing stray light offset. 2. The method of removing stray light offset according to claim 1, wherein the region that is not affected by the light reflected by the optical disk is between the reflection surface and the surface of the optical disk. The region that is not affected by the light reflected by the optical disk is within a range of 23% to 76% of the distance between the reflection surface and the surface of the optical disk in the thickness direction of the optical disk with respect to the reflection surface of the optical disk. The method for removing a stray light offset according to claim 1. Actuator drive means for outputting a focus drive signal for moving the optical pickup relative to the optical disk, S-shaped level detection means for detecting an S-shaped signal generated in the focus error signal by the reflecting surface of the optical disk, and the S-shaped signal A storage unit that stores the voltage of the focus drive signal when the light is generated as a reference voltage, a calculation unit that calculates the voltage of the focus drive signal in an area that is not affected by the reflected light from the optical disk based on the reference voltage, and the focus An optical disc apparatus comprising: an offset detection unit that measures an offset voltage of a control signal when a drive signal is the calculated voltage; and an offset adjustment unit that performs offset adjustment to remove a stray light offset. 5. The optical disk apparatus according to claim 4, wherein the area not affected by the light reflected by the optical disk is between the reflection surface and the surface of the optical disk. The region that is not affected by the light reflected by the optical disk is within a range of 23% to 76% of the distance between the reflection surface and the surface of the optical disk in the thickness direction of the optical disk with respect to the reflection surface of the optical disk. The optical disc device according to claim 4.

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