JP2008176852A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive which can stably lead in focus to an innermost recording layer of an optical disk with no contacting of an objective lens to the optical disk which is wobbling. <P>SOLUTION: The objective lens 116 is brought close to the optical disk 101 rotated by a spindle motor 102 with a constant speed V1 of percentage smaller than the working distance, and the objective lens 116 is further brought close a certain distance from the time when a focal point of a laser beam reached a disk surface and stopped. The optical disk 101 performs one revolution from the time when the focal point has reached the disk surface, and further the objective lens 116 is moved in the direction which keeps away from the optical disk 101 at a speed V3 from the time when carrying out predetermined angle rotation corresponding an FG number which indicates a motor rotating-phase. When it is determined that the focal point has reached a recording layer, focal loop control is started. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus, and more particularly to a technique for accurately controlling the focal point of an objective lens on a recording layer of an optical disc.

  As an optical recording medium, an optical disc having a plurality of recording layers in a single disc is known. For recording on an optical disc, a laser beam is focused on the recording layer by an objective lens, and the recording layer material is changed. This is done by optically changing with heat. The recorded information is reproduced by focusing a laser beam weaker than that at the time of recording on the recording layer, converting the reflected light into an electric signal by a photodiode, and reading the signal. Due to the tilt of the optical disk support member of the optical disk apparatus and the distortion that occurs when the optical disk is molded, the distance between the surface of the optical disk and the objective lens is not constant, and so-called surface vibration occurs. On the other hand, for selective recording or reading on a plurality of recording layers, the focus is first drawn into an optical disc that is wobbling, and the focal point of the objective lens is focused on the recording layer without contacting the objective lens. Need to move quickly. However, when the surface shake of the optical disk is large, there is a possibility that inconveniences such as failure of focus pull-in or an objective lens contacting the optical disk may occur. In order to solve such a problem, Patent Document 1 discloses a method of stopping the transfer operation of the objective lens when the distance between the objective lens and the optical disk surface is the shortest or when the distance is changing. Proposed.

JP 2005-505875 A

  However, in the conventional method, there is a possibility that the focus is drawn into the wrong layer for the optical disc having a plurality of recording layers.

  The present invention has been made in consideration of this point, and it is possible to perform stable focus pull-in to the innermost recording layer of the optical disc without bringing the objective lens into contact with the optical disc having surface wobbling. A first object is to provide an optical disk device, and a second object is to provide an optical disk device capable of calculating an optimum amplifier gain of a focus error signal for each recording layer. A third object is to provide an apparatus.

  In order to achieve the first object, the invention according to claim 1 is directed to irradiating a recording layer of an optical disc rotated by a spindle motor with a laser beam through an objective lens, and based on reflected light from the recording layer. In an optical disc apparatus having a function of recording or reproducing information with respect to an optical disc, the objective lens is moved in a direction closer to the optical disc at a rate smaller than the working distance of the objective lens at every cycle time of the minimum number of revolutions of the optical disc. A focus actuator driving means for causing the objective lens to be driven by the focus actuator driving means, and detecting a focal point of the laser beam from a sum signal of reflected light from the surface of the optical disc, and the surface detecting means When detecting that the in-focus point has reached the surface of the optical disc by FG number storage means for storing the FG number indicating the rotational phase of the spindle motor, and the position of the objective lens at the time when the surface detection means detects that the focal point has reached the surface of the optical disk. Further, the objective lens approaching means for bringing the objective lens closer to the optical disk by a certain distance, and the rotational phase of the spindle motor to a rotational phase delayed by a predetermined amount from the rotational phase corresponding to the FG number stored in the FG number storage means And a focus pull-in means for moving the objective lens in a direction away from the optical disk and moving the focal point from the surface of the optical disk to the innermost recording layer.

  In order to achieve the second object, the invention according to claim 2 is directed to irradiating a recording layer of an optical disk rotated by a spindle motor with a laser beam through an objective lens, and based on the reflected light from the recording layer. In an optical disc apparatus having a function of recording or reproducing information with respect to an optical disc, the objective lens is moved in a direction closer to the optical disc at a rate smaller than the working distance of the objective lens at every cycle time of the minimum number of revolutions of the optical disc. A focus actuator driving means for causing the objective lens to be driven by the focus actuator driving means, and detecting a focal point of the laser beam from a sum signal of reflected light from the surface of the optical disc, and the surface detecting means When detecting that the in-focus point has reached the surface of the optical disc by FG number storage means for storing the FG number indicating the rotational phase of the spindle motor, and the position of the objective lens at the time when the surface detection means detects that the focal point has reached the surface of the optical disk. Further, the objective lens approaching means for bringing the objective lens closer to the optical disk by a certain distance, and the rotational phase of the spindle motor to a rotational phase delayed by a predetermined amount from the rotational phase corresponding to the FG number stored in the FG number storage means The objective lens is moved at a high speed in a direction away from the optical disc, and each detected recording layer is detected based on a focus error signal obtained from reflected light from the recording layer detected during the movement. And an amplifier gain calculating means for calculating an optimum amplifier gain.

  In order to achieve the third object, the invention described in claim 3 is directed to irradiating a recording layer of an optical disk rotated by a spindle motor with a laser beam through an objective lens, and based on reflected light from the recording layer. In an optical disc apparatus having a function of recording or reproducing information with respect to an optical disc, the objective lens is moved in a direction closer to the optical disc at a rate smaller than the working distance of the objective lens at every cycle time of the minimum number of revolutions of the optical disc. A focus actuator driving means for causing the objective lens to be driven by the focus actuator driving means, and detecting a focal point of the laser beam from a sum signal of reflected light from the surface of the optical disc, and the surface detecting means When detecting that the in-focus point has reached the surface of the optical disc by FG number storage means for storing the FG number indicating the rotational phase of the spindle motor, and the position of the objective lens at the time when the surface detection means detects that the focal point has reached the surface of the optical disk. Further, the objective lens approaching means for bringing the objective lens closer to the optical disk by a certain distance, and the rotational phase of the spindle motor to a rotational phase delayed by a predetermined amount from the rotational phase corresponding to the FG number stored in the FG number storage means At this point, the objective lens is moved at a high speed in a direction away from the optical disc, and the amplitude of the focus error signal obtained from the reflected light from the recording layer detected during the movement and the focus error signal S is drawn. Disc identifying means for identifying the type of the optical disc based on the number of character waveforms. And wherein the Rukoto.

  According to the first aspect of the present invention, the objective lens is controlled so as to approach the optical disk at a rate smaller than the working distance of the objective lens for each rotation of the optical disk, and the focal point of the laser beam is from the surface of the optical disk. An FG number indicating the rotational phase of the spindle motor at the time when it is detected from the sum signal of the reflected light and when it is detected that the focal point has reached the optical disk surface is stored. Thereafter, the objective lens is brought closer to the optical disc by a certain distance. The objective lens is controlled to move away from the optical disk from the point when the spindle motor rotates to a rotational phase delayed by a predetermined amount from the rotational phase corresponding to the stored FG number, and is farthest from the surface of the optical disk. Focus is drawn into the recording layer. As a result, even with an optical disc that is wobbling, the focus can be drawn into the recording layer that is farthest from the optical disc surface without the objective lens coming into contact with the optical disc.

  According to the second aspect of the present invention, the objective lens is controlled so as to approach the optical disk at a rate smaller than the working distance of the objective lens for each rotation of the optical disk, and the focal point of the laser beam is from the surface of the optical disk. An FG number indicating the rotational phase of the spindle motor at the time when it is detected from the sum signal of the reflected light and when it is detected that the focal point has reached the optical disk surface is stored. Thereafter, the objective lens is brought closer to the optical disc by a certain distance. Then, the objective lens is controlled to move at a high speed in the direction away from the optical disk from the time when the spindle motor rotates to the rotation phase delayed by a predetermined amount from the rotation phase corresponding to the stored FG number. Based on the focus error signal detected during the movement, the optimum amplifier gain is calculated for each recording layer. As a result, even if the optical disc is wobbling, the optimum amplifier gain of the focus error signal can be calculated for each recording layer without the objective lens coming into contact with the optical disc.

  According to the third aspect of the present invention, the objective lens is controlled so as to approach the optical disk at a rate smaller than the working distance of the objective lens every rotation of the optical disk, and the focal point of the laser beam is from the surface of the optical disk. An FG number indicating the rotational phase of the spindle motor at the time when it is detected from the sum signal of the reflected light and when it is detected that the focal point has reached the optical disk surface is stored. Thereafter, the objective lens is brought closer to the optical disc by a certain distance. Then, the objective lens is controlled to move at a high speed in the direction away from the optical disk from the time when the spindle motor rotates to the rotation phase delayed by a predetermined amount from the rotation phase corresponding to the stored FG number. The type of the optical disc is identified based on the amplitude of the focus error signal detected during the movement and the number of S-shaped waveforms drawn by the focus error signal. As a result, even if the optical disc is wobbling, the type of the optical disc can be identified without the objective lens coming into contact with the optical disc.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of a main part of the optical disc apparatus according to the first embodiment of the present invention. The optical disk 101 is held in a detachable manner on a turntable 104 fixed to the shaft 103 of the spindle motor 102. The rotation speed of the spindle motor 102 is controlled so that a predetermined linear velocity is obtained at the spot position of the laser beam.

  The pickup 105 includes a laser diode 106, a light receiving unit 107 including a plurality of photodiodes, a half mirror 118, a movable unit 117 on which an objective lens 116 and a magnet (not shown) are mounted, a tracking control coil 108, and a focus control coil. 109. The movable portion 117 on which the objective lens 116 and the magnet are mounted is configured to be displaced in the tracking direction and the focus direction by the tracking control coil 108 and the focus control coil 109, respectively.

  The entire pickup 105 is configured to be movable in the radial direction of the optical disc 101. Specifically, a microcomputer (hereinafter referred to as “microcomputer”) 113 controls a thread motor 110 attached to a lead screw 111 fitted to a female screw portion attached to a pickup via a drive circuit 112, The pickup 105 is driven in the radial direction.

  Laser light emitted from the laser diode 106 is irradiated onto the optical disc 101 through the objective lens 116, and is modulated and reflected by a recording signal or guide groove of the optical disc 101. This reflected light is incident on the light receiving unit 107 via the half mirror 118. The analog signal processing circuit 114 detects and outputs the tracking error signal TE, the focus error signal FE, and the sum signal PE from the signal photoelectrically converted by the light receiving unit 107. Further, these signals are converted from analog to digital by the AD converters AD1, AD2, and AD3 and input to the microcomputer 113.

FIG. 2 is a diagram for explaining the calculation of the tracking error signal TE, the focus error signal FE, and the sum signal PE. The light receiving unit 107 shown in FIG. 2 is composed of four divided photodiodes. The reflected light from the optical disk 101 is incident on a photodiode divided into four parts with astigmatism. The reflected light incident on each of the four divided photodiodes is photoelectrically converted, and photoelectrically converted signals A, B, C, and D are output to the analog signal processing circuit 114. The analog signal processing circuit 114 calculates the tracking error signal TE, the focus error signal FE, and the sum signal PE by applying the input signals A, B, C, and D to the following equations (1) to (3). To do.
TE = (A + D)-(B + C) (1)
FE = (A + C) − (B + D) (2)
PE = (A + B + C + D) (3)

  Returning to FIG. 1, the tracking error signal TE output from the analog signal processing circuit 114 is analog-digital converted by the analog-digital converter AD <b> 1 and is taken into the microcomputer 113. Similarly, the focus error signal FE is analog-to-digital converted by the analog-to-digital converter AD2, and is taken into the microcomputer 113. Further, the sum signal PE is taken into the microcomputer 113 via the analog-digital converter AD3. The sum signal PE is supplied to a reproduction processing circuit (not shown) and returned to the recorded original signal and output.

  The microcomputer 113 is connected to a ROM that stores programs and fixed data, and a RAM that stores variable values and the like. The microcomputer 113 outputs a tracking control drive signal calculated based on the tracking error signal TE to the digital / analog converter DA1. The tracking control drive signal digital-to-analog converted by the digital-analog converter DA1 drives the tracking control coil 108 via the drive circuit DRV1. Similarly, a focus control drive signal calculated based on the focus error signal FE is output to the digital-analog converter DA2, and the focus control drive signal digital-analog converted by the digital-analog converter DA2 is subjected to focus control via the drive circuit DRV2. The coil 109 for driving is driven.

  Next, a focus pull-in operation performed in the optical disc apparatus will be described by taking as an example a case where surface deflection of the optical disc 101 is large.

  First, the microcomputer 113 outputs a focus control drive signal in a direction in which the objective lens 116 is moved away from the optical disk 101, and the objective lens is positioned so that the focal point is completely away from the disk surface in any surface vibration disk. 116 is moved.

Next, the microcomputer 113 outputs a focus control drive signal for driving the objective lens 116 at a speed V <b> 1 in a direction in which the objective lens 116 approaches the optical disk 101. Specifically, the objective lens 116 is brought closer to the optical disc 101 by increasing the drive value FD0 of the output data from the digital-analog converter DA2 by a constant amount at a constant period. At this time, assuming that one rotation cycle of the optical disk 101 is T and a distance sufficiently smaller than the working distance (working distance) is L1, the relationship among the speed V1, the rotation cycle T, and the distance L1 is V1 = L1 / T. The drive value FD0 is updated at a proper rate. That is, the objective lens 116 approaches the optical disk 101 by a distance L1 every time the optical disk 101 makes one rotation. When the update value corresponding to the current distance L1 is FD0_STEP1, the update of the drive value FD0 can be expressed by the following equation.
FD0 = FD0 + FD0_STEP1 (4)
Here, FD0 on the right side is the previous value.

  At this time, an upper limit drive value FD0_MAX that is an upper limit value of the drive value FD0 is set in advance. The upper limit drive value FD0_MAX is determined in consideration of the mechanical error of the distance from the objective lens 116 to the turntable 104, the degree of surface deflection or warpage of the optical disc 101, the variation in focus actuator sensitivity, and the like. It is set to a large value sufficient to reach the disk recording surface. Before the drive value FD0 is updated, the magnitude relationship between the drive value FD0 and the upper limit drive value FD0_MAX is confirmed, and the movement of the objective lens 116 is terminated when FD0 = FD0_MAX.

  While the objective lens 116 moves in the direction approaching the optical disc 101, the microcomputer 113 continues to monitor whether the reflected light from the surface of the optical disc 101 is obtained, that is, whether the sum signal PE does not exceed the threshold value TH_pe. . FIG. 3 shows the positional relationship between the surface of the optical disc 101 and the surface of the objective lens 116 having a large surface shake, the position of the optical disc recording layer that changes as the optical disc 101 rotates, and the focal point that changes when the objective lens is driven and controlled. It is a figure for demonstrating the relationship with this position.

  FIG. 3 shows that the objective lens 116 is driven and controlled so as to approach the optical disc 101 at a speed V1 from a position where the focal point is completely away from the surface of the optical disc 101, and the focal point is about to reach the disc surface at time t0. However, it shows. At this time, since the reflected light from the disc has not yet been obtained, the objective lens 116 is continuously driven and controlled so as to approach the optical disc 101 at the speed V1 as it is. However, since the optical disk 101 is wobbling, the distance between the surface of the optical disk 101 and the objective lens 116 increases in reverse, and the focal point does not reach the disk surface. Thereafter, the distance between the disc surface and the objective lens 116 starts to approach due to surface deflection of the optical disc 101, and the focal point reaches the disc surface at time t1. FIG. 3 shows that the transition of the sum signal PE takes a peak value at time t1 and exceeds a predetermined threshold TH_pe for the first time.

When detecting that the sum signal PE exceeds the threshold value TH_pe at time t1, the microcomputer 113 obtains the upper limit drive value FD0_MAX from the value FD0 (t1) of the drive value FD0 at time t1 and the digital-analog converter DA2 corresponding to the distance L2. To the sum of the drive value D2, which is the output data.
FD0_MAX = FD0 (t1) + D2 (5)
In other words, the objective lens 116 is finally brought closer to the optical disc 101 by a distance L2, and the focal point is at a position that is substantially (L1 + L2) deeper than the lowest point on the disc surface. Here, the distances L1 and L2 need to be selected such that the distance (L1 + L2) surely exceeds the distance from the disk surface to the recording layer, and there is no risk that the approaching objective lens 116 will contact the optical disk 101. .

  When detecting that the sum signal PE exceeds the threshold value TH_pe at time t1, the microcomputer 113 simultaneously outputs an FG number (frequency) indicating the rotational phase of the spindle motor 102 output from the spindle motor 102 at time t1. (Number assigned to the pulse output from the generator in one rotation cycle) is stored as the FG stored value FG_MEM.

  After time t1, the objective lens 116 moves to a position corresponding to the upper limit drive value FD0_MAX updated at time t1 at a speed V2 that is equal to or slightly different from the speed V1. (In FIG. 3, L1 = L2 and V1 = V2 are set for simplification of the drawing).

  At time t2, FD0 = FD0_MAX, and the movement of the objective lens 116 ends. The microcomputer 113 waits for the spindle to rotate to the FG number obtained by adding a predetermined number n to the FG stored value FG_MEM stored at time t1. Here, the predetermined number n is set to a small integer of about 0 to 3, for example, and the rotational phase of the optical disc 101 at time t1 itself or a rotational phase slightly delayed from the rotational phase of the optical disc 101 at time t1. This is to wait for the time t3.

  At time t3, the position of the disk surface is always near the lowest point (position where the distance between the objective lens 116 and the optical disk 101 is the shortest), and the focal position is approximately (L1 + L2) from the surface of the optical disk 101. It is a position that is in the back, that is, a position that is deeper than the recording layer of the disc. The objective lens 116 is moved from this position in a direction away from the optical disc 101 at a speed V3, and a focus pull-in operation is performed from the back side of the disc recording layer.

  When the objective lens 116 starts to move away from the optical disc 101, it is determined whether or not the signal level of the focus error signal FE matches a preset pull-in condition. When the signal level of the focus error signal FE matches the pull-in condition, the movement of the objective lens 116 at the speed V3 is finished, the focus servo loop is closed, and control by the focus error signal FE is started.

  Next, the focus pull-in operation process described above will be described with reference to the flowchart shown in FIG. After the objective lens 116 is moved so that the focal point is completely away from the disk surface, the focus pull-in control is started. First, in step 401, initial values of the upper limit drive value FD0_MAX and the drive value FD0 regarding the movement of the objective lens 116 are set.

  Next, proceeding to step 402, the objective lens 116 is moved at a speed V1 to a position corresponding to the drive value FD0, and at step 403, it is determined whether or not the total signal PE exceeds a predetermined threshold value TH_pe. Since this answer is initially negative (NO), the routine proceeds to step 406, where it is determined whether the drive value FD0 is smaller than the upper limit drive value FD0_MAX. As long as this answer is affirmative (YES), the process proceeds to step 407, the drive value FD 0 is updated according to the equation (4), and the process returns to step 402.

  When the drive value FD0 is repeatedly updated in step 407 and the answer to step 403 is affirmative (YES), that is, when the sum signal PE exceeds the predetermined threshold value TH_pe, the process proceeds to step 404 to move the objective lens. First, it is determined whether or not the sum signal PE has exceeded a predetermined threshold value TH_pe. Since this answer is initially affirmative (YES), the process proceeds to step 405, and the upper limit drive value FD0_MAX is changed by the equation (5). Further, the FG number of the spindle motor at this time is stored as a stored value FG_MEM, and the process proceeds to Step 406.

  Since the answer to step 406 is affirmative (YES), the process again proceeds to step 403 via steps 407 and 402. Even if the answer to step 403 is affirmative (YES) this time, the answer to step 404 is negative (NO), so the process proceeds to step 406.

  If the answer to step 406 is negative (NO), the process proceeds to step 408 to determine whether or not the detected FG number of the spindle motor 102 is equal to the sum of the stored value FG_MEM stored in step 405 and the predetermined value n. When the spindle rotates and the answer to step 408 is affirmative (YES), the routine proceeds to step 409.

In step 409, the objective lens 116 is driven away from the optical disc 101 in accordance with the drive value FD0. Initially, since FD0 = FD0_MAX, the objective lens 116 does not actually move. Next, the routine proceeds to step 410, where it is determined whether the detected signal level of the focus error signal FE matches the pull-in condition. Initially, the answer to step 410 is negative (NO), so the process proceeds to step 411 to update the drive value FD0 according to the following equation (7).
FD0 = FD0-FD0_STEP2 (7)

  When the drive value FD0 is updated in step 411, the process returns to step 409, and the objective lens 116 is moved away from the optical disc 101 in accordance with the updated drive value FD0. If the answer to step 410 is affirmative (YES) and the detected signal level of the focus error signal FE matches the pull-in condition, the process proceeds to step 412 and focus loop control of the objective lens 116 is started.

  In FIG. 3, the recording layer of the disk is drawn as only one layer for simplification of the drawing. However, even when there are a plurality of recording layers, the focal point can reach the deeper side than the innermost recording layer. If the distance (L1 + L2) is determined, focus pull-in from the innermost recording layer can be stably performed.

(Second Embodiment)
Next, as a second embodiment, the amplifier gain adjustment control of the focus error signal FE performed for each of a plurality of recording layers of the optical disc will be described.
The configuration of this apparatus is the same as that of the first embodiment shown in FIG. FIG. 5 is a flowchart showing a flow of amplifier gain adjustment control of the focus error signal FE. Step 501 is a process in which the setting of the lower limit drive value FD0_MIN is added to the process of step 401 in the flowchart of the first embodiment shown in FIG. The lower limit drive value FD0_MIN is set to a value corresponding to the moving distance until the in-focus point moves away from the disc surface in consideration of disc surface deflection.

  Steps 502 to 509 perform the same processing as steps 402 to 409 in the flowchart of the first embodiment shown in FIG. The processing up to step 509 is the movement control of the objective lens 116 until time t3 shown in FIG. 3, and at the time t3, the in-focus position is always behind the plurality of recording layers of the optical disc 101.

  In step 509, the objective lens 116 is driven away from the optical disc 101 in accordance with the drive value FD0. Initially, since FD0 = FD0_MAX, the objective lens 116 does not actually move. Next, the routine proceeds to step 510. A focus error signal FE detected when the focal point passes through the recording layer of the optical disk 101 from the back side toward the surface draws a so-called S-shaped waveform. In step 510, it is determined whether or not the first S-shaped waveform of the focus error signal FE has been detected. Initially, this answer is negative (NO), so the routine proceeds to step 512, where it is determined whether or not the second S-shaped waveform of the focus error signal FE has been detected. Initially, this answer is also negative (NO), so the routine proceeds to step 514, where it is determined whether the drive value FD0 is greater than the lower limit drive value FD0_MIN set in step 501. Initially, the answer is affirmative (YES), so the process proceeds to step 515, and the drive value FD0 is updated by the same process as step 411 shown in FIG.

  At this time, the moving speed V3 of the objective lens 116 determined by the update value FD0_STEP2 of the drive value FD0 is different from the time when the objective lens 116 is brought close to the optical disk 101, and therefore there is no risk of contact with the optical disk 101. Can be set to a relatively large value, and can be a high speed exceeding the surface vibration speed of the disk recording layer.

  When the drive value FD0 is updated in step 515, the process returns to step 509, and the objective lens 116 is driven away from the optical disc 101 in accordance with the updated drive value FD0. If the answer to step 510 is affirmative (YES) and the first S-shaped waveform of the focus error signal FE is detected, the process proceeds to step 511, where the maximum and minimum values of the focus error signal FE obtained so far are determined. The amplitude of the focus error signal FE is calculated. The amplitude calculated here corresponds to the nearest recording layer through which the focal point has passed, and in this case, corresponds to the innermost recording layer. Thereafter, the process proceeds to step 512.

  Next, when the answer to step 512 is affirmative (YES), the process proceeds to step 513, and the amplitude of the focus error signal FE is determined from the maximum value and the minimum value of the focus error signal FE detected after the first S-shaped waveform detection. calculate. The amplitude calculated here corresponds to the recording layer nearest to which the focal point has passed, and in this case, corresponds to the second recording layer from the back.

  As long as the answer to step 514 is affirmative (YES), a series of processing from step 515 to step 514 is executed. Thereafter, when the answer to step 514 is negative (NO) and the drive value FD0 is equal to the lower limit drive value FD0_MIN set in step 501, the process proceeds to step 516, and the focus error signal FE calculated in steps 511 and 513 is determined. The optimum amplifier gain corresponding to each recording layer through which the focal point passes is calculated from the amplitude.

  In this way, the S-shaped waveform of the focus error signal FE is detected one by one in order from the innermost recording layer every time the focal point passes through the recording layer. Therefore, by obtaining the amplitude of the focus error signal FE in each recording layer, the focus error signal FE can be adjusted to an optimum gain for each recording layer.

(Third embodiment)
Next, disc type identification of an optical disc will be described as a third embodiment.
The configuration of this apparatus is the same as that of the first embodiment shown in FIG. FIG. 6 is a flowchart showing the flow of disc type identification processing. Steps 601 to 609 perform the same processing as steps 501 to 509 in the flowchart of the second embodiment shown in FIG. The processing up to step 609 is the movement control of the objective lens 116 up to time t3 shown in FIG. 3, and at the time t3, the in-focus position is always behind the plurality of recording layers of the optical disc 101.

  In step 610, the maximum and minimum values of the focus error signal FE measured so far are detected, and in step 611, the number of measured S-shaped waveforms is detected. Next, the routine proceeds to step 612, where it is determined whether the drive value FD0 is greater than the lower limit drive value FD0_MIN set at step 601. Initially, this answer is affirmative (YES), so the routine proceeds to step 613, where the drive value FD0 is updated by the same processing as step 411 shown in FIG.

  As long as the answer to step 612 continues to be affirmative (YES), a series of processing from step 613 to step 612 is executed. Thereafter, when the answer to step 612 is negative (NO) and the drive value FD0 becomes equal to the lower limit drive value FD0_MIN set in step 601, the process proceeds to step 614 and the maximum value of the focus error signal FE detected in step 610 is reached. Then, the amplitude of the focus error signal FE for each recording layer is calculated from the minimum value, and the type of the optical disk is identified from the calculated amplitude of the focus error signal FE and the number of S-shaped waveforms detected in step 611.

  In this way, the S-shaped waveform of the focus error signal FE is detected one by one in order from the innermost recording layer every time the focal point passes through the recording layer. Therefore, accurate disc identification can be performed by obtaining the amplitude of the focus error signal FE in each recording layer and correctly detecting the number of recording layers.

It is a block diagram which shows the structure of the optical disk recording / reproducing apparatus concerning one Embodiment of this invention. It is a figure for demonstrating calculation of the tracking error signal TE, the focus error signal FE, and the sum total signal PE. It is a figure for demonstrating the movement control of an objective lens. It is a flowchart for demonstrating a focus drawing-in operation | movement process. 6 is a flowchart for explaining processing of amplifier gain adjustment control of a focus error signal FE. It is a flowchart for demonstrating the disc type identification process.

Explanation of symbols

101 Optical disk 102 Spindle motor (FG number storage means)
104 Turntable 105 Pickup 106 Laser diode 107 Light receiving portion (surface detection means, focus pull-in means)
108, 109 coils (focus actuator drive means, objective lens approach means, focus pull-in means)
113 microcomputer (surface detection means, FG number storage means)
114 Analog signal processing circuit (surface detection means)
116 Objective lens 117 Movable part 118 Half mirror

Claims (3)

In an optical disc apparatus having a function of irradiating a recording layer of an optical disc rotated by a spindle motor through an objective lens through an objective lens and recording or reproducing information on the optical disc based on reflected light from the recording layer.
A focus actuator driving means for moving the objective lens in a direction approaching the optical disc at a ratio of a distance smaller than the working distance of the objective lens every cycle time of the minimum number of rotations of the optical disc;
The objective lens is driven by the focus actuator driving means, and a surface detecting means for detecting a focal point of the laser light from a sum signal of reflected light from the surface of the optical disc;
FG number storage means for storing an FG number indicating the rotational phase of the spindle motor at the time when the surface detection means detects that the focal point has reached the surface of the optical disc;
Objective lens approach means for bringing the objective lens closer to the optical disk by a certain distance from the position of the objective lens at the time when the surface detection means detects that the focal point has reached the surface of the optical disk;
The objective lens is moved in a direction away from the optical disc from the time when the rotational phase of the spindle motor becomes a rotational phase delayed by a predetermined amount from the rotational phase corresponding to the FG number stored in the FG number storage means, An optical disc apparatus comprising: a focus pull-in unit that moves the focal point to the recording layer that is furthest from the surface of the optical disc. In an optical disc apparatus having a function of irradiating a recording layer of an optical disc rotated by a spindle motor through an objective lens through an objective lens and recording or reproducing information on the optical disc based on reflected light from the recording layer.
A focus actuator driving means for moving the objective lens in a direction approaching the optical disc at a ratio of a distance smaller than the working distance of the objective lens every cycle time of the minimum number of rotations of the optical disc;
The objective lens is driven by the focus actuator driving means, and a surface detecting means for detecting a focal point of the laser light from a sum signal of reflected light from the surface of the optical disc;
FG number storage means for storing an FG number indicating the rotational phase of the spindle motor at the time when the surface detection means detects that the focal point has reached the surface of the optical disc;
Objective lens approaching means for bringing the objective lens closer to the optical disc by a certain distance from the position of the objective lens at the time when it is detected by the surface detection means that the focal point has reached the surface of the optical disc;
The objective lens is moved at a high speed in a direction away from the optical disk from the time when the rotational phase of the spindle motor becomes a rotational phase delayed by a predetermined amount from the rotational phase corresponding to the FG number stored in the FG number storage means. And an amplifier gain calculating means for calculating an optimum amplifier gain for each detected recording layer based on a focus error signal obtained from reflected light from the recording layer detected during the movement. An optical disk device. In an optical disc apparatus having a function of irradiating a recording layer of an optical disc rotated by a spindle motor through an objective lens through an objective lens and recording or reproducing information on the optical disc based on reflected light from the recording layer.
A focus actuator driving means for moving the objective lens in a direction approaching the optical disc at a ratio of a distance smaller than the working distance of the objective lens every cycle time of the minimum number of rotations of the optical disc;
The objective lens is driven by the focus actuator driving means, and a surface detecting means for detecting a focal point of the laser light from a sum signal of reflected light from the surface of the optical disc;
FG number storage means for storing an FG number indicating the rotational phase of the spindle motor at the time when the surface detection means detects that the focal point has reached the surface of the optical disc;
Objective lens approaching means for bringing the objective lens closer to the optical disc by a certain distance from the position of the objective lens at the time when it is detected by the surface detection means that the focal point has reached the surface of the optical disc;
The objective lens is moved at a high speed in a direction away from the optical disk from the time when the rotational phase of the spindle motor becomes a rotational phase delayed by a predetermined amount from the rotational phase corresponding to the FG number stored in the FG number storage means. Disc identifying means for identifying the type of the optical disc based on the amplitude of the focus error signal obtained from the reflected light from the recording layer detected during the movement and the number of S-shaped waveforms drawn by the focus error signal; An optical disc apparatus comprising:

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