JP4216167B2 - Optical disk device - Google Patents

Description

  The present invention relates to control for converging a light beam on an information surface of an optical disc.

  Conventionally, optical disks such as DVD-ROM, DVD-RAM, DVD-RW, DVD-R, DVD + RW, and DVD + R are known as high-density and large-capacity recording media. In recent years, the development of optical discs such as Blu-ray Discs (BDs) with higher density and larger capacity than these optical discs has also been developed.

  The optical disc apparatus reads and / or writes data by converging the light beam on the information surface of the optical disc. For an optical disc in which a plurality of information surfaces are stacked, the optical disc apparatus can move the focal point of the light beam from one information surface to the other information surface. Such movement of the focus is called interlayer jump or focus jump.

For example, the optical disc apparatus described in Patent Document 1 realizes a focus jump as follows. That is, this optical disc apparatus applies a pulse signal to the optical head in a state where focus control is not performed (held). The focus movement is started by the application of the pulse signal. The optical disk device controls the pulse signal to increase the focal point moving speed and then decrease it. Then, the optical disc apparatus detects the light beam reflected on the optical disc and determines that the focal point has reached the target information surface or that the focal point has slightly passed through the information surface. This determination ends the focus jump.
JP-A-9-326123 (paragraphs 0108 to 0118, FIGS. 18 and 12)

  There is a possibility that an accurate focus jump cannot be realized with a conventional optical disc apparatus for an optical disc in which the focal position of the light beam must be controlled with high accuracy. For example, in a DVD that is rotating at a high speed to read / write data at high speed or a BD that has a higher density than the DVD, the range in which the variation of the focal position is allowed is narrow. For this reason, the conventional optical disc apparatus cannot accurately control the focal position, and the focus jump may not be performed accurately.

  Since an accurate focus jump cannot be realized, the objective lens (focusing lens) of the optical disc apparatus and the optical disc may collide. For example, when a focusing lens having a numerical aperture (NA) of 0.8 or more is used to record data on a high-density optical disc such as a BD, the distance between the optical disc and the focusing lens is about 100 μm. Then, when a focus jump is made to an information surface at a deeper position, there is a possibility that the focusing lens and the optical disc collide with the operation accuracy of the conventional optical disc device, and both the focusing lens and the optical disc are damaged.

  An object of the present invention is to realize an accurate focus jump while appropriately avoiding a collision between an optical disc and a focusing lens.

  An optical disc apparatus according to the present invention includes a light source, a converging unit for converging light from the light source, a position of the converging unit based on a control signal in a direction perpendicular to the information surface of the optical disc, and focusing the light. A moving unit that moves, a light receiving unit that receives reflected light from the information surface in a plurality of regions, generates a plurality of signals according to the amount of light received in each region, and generates a focus error signal based on the plurality of signals And a control unit that generates the control signal based on the focus error signal. The control signal is a signal for moving the focus of the light to a range where focus control can be performed on the information surface. The control unit generates a control signal for decelerating the focal point of the light with a first acceleration and then decelerating with a second acceleration with respect to the information surface. The absolute value of the second acceleration is smaller than the absolute value of the first acceleration.

  The control unit is a control signal for changing the position of the converging unit in a direction away from the optical disc, and the focus of the light is moved when the focus of the light first enters a range in which the focus control is possible. A control signal for stopping the control may be generated.

  The control unit generates a control signal that changes the position of the converging unit in a direction approaching the optical disc until the focus of the light first passes through the range in which the focus control is possible, and then moves away from the optical disc. A control signal for changing the position of the converging unit in the direction may be generated.

  The control unit generates a control signal for decelerating the focus of the light with the first acceleration and then decelerating with the second acceleration until the focus of the light first passes through the range in which the focus control is possible. When the focal point of the light passes through the range where the focus control is possible, a control signal for stopping the movement of the focal point of the light may be generated.

  The control unit generates a control signal that decelerates at the first acceleration and stops the movement of the focal point of the light, and then generates a control signal that moves again in the same direction and decelerates at the second acceleration. Also good.

  The optical disc has a plurality of information surfaces. The control unit may generate a control signal for moving the focus of the light from an information surface on which focus control is performed to a range in which focus control is possible with respect to another information surface.

  The moving unit changes the position of the focusing unit based on the applied pulse train, and the control unit generates the control signal including a first pulse that increases acceleration and a second pulse that decreases acceleration. May be.

  The moving unit changes the position, acceleration, and speed of the focusing unit based on the number and magnitude of the applied first pulse and the second pulse, and the applied time length, and the control unit includes: The control signal may be generated by adjusting at least one of the number and magnitude of the first pulse and the second pulse and the applied time length.

  The control unit may stop focus control on the information surface while generating the control signal.

  The control unit may start the focus control after moving the focus of the light to a range where the focus control is possible with respect to the information surface.

  The focus moving method according to the present invention is a method that is executed in an optical disc apparatus and moves the focus of light to a range where focus control is possible. An optical disc apparatus includes a light source, a converging unit for converging light from the light source, and a movement for moving the focal point of the light by changing the position of the converging unit in a direction perpendicular to the information surface of the optical disc based on a control signal. A light receiving unit that receives reflected light from the information surface in a plurality of regions and generates a plurality of signals according to the amount of light received in each region, and a signal generation that generates a focus error signal based on the plurality of signals Part. The method generates a control signal for decelerating the focal point of the light with a first acceleration with respect to the information surface based on the focus error signal, and applies the first control step to the moving unit. A second step of generating a control signal for decelerating the focal point of the light at a second acceleration and applying the control signal to the moving unit, the absolute value of the second acceleration being smaller than the absolute value of the first acceleration A second step.

  The processor according to the present invention is mounted on an optical disc apparatus. This optical disc apparatus moves the focal point of the light by changing the position of the converging unit in a direction perpendicular to the information surface of the optical disc based on a control signal based on a light source, a converging unit for converging the light from the light source, and a control signal. A moving unit, a light receiving unit that receives reflected light from the information surface in a plurality of regions, generates a plurality of signals according to the amount of light received in each region, and a signal that generates a focus error signal based on the plurality of signals And a generation unit. The processor generates a control signal for decelerating the focal point of the light with a first acceleration with respect to the information surface based on the focus error signal, and applies the first movement control unit to the moving unit; and the focal point of the light Is a second movement control unit that generates a control signal for decelerating at a second acceleration and applies the control signal to the moving unit, wherein a second absolute value of the second acceleration is set smaller than an absolute value of the first acceleration. A movement control unit.

  The computer program according to the present invention is executed in the optical disc apparatus. An optical disc apparatus includes a light source, a converging unit for converging light from the light source, and a movement for moving the focal point of the light by changing the position of the converging unit in a direction perpendicular to the information surface of the optical disc based on a control signal. A light receiving unit that receives reflected light from the information surface in a plurality of regions and generates a plurality of signals according to the amount of light received in each region, and a signal generation that generates a focus error signal based on the plurality of signals And a control unit that generates the control signal based on the focus error signal. The computer program generates a control signal for decelerating the focal point of the light at a first acceleration with respect to the information surface based on the focus error signal, and applies the control signal to the moving unit. A second step of generating a control signal for decelerating the focal point of the light with a second acceleration and applying the control signal to the moving unit, wherein an absolute value of the second acceleration is calculated from an absolute value of the first acceleration; And the second step of setting a smaller value is executed.

  According to the present invention, the focus of light is decelerated at the first acceleration, and then decelerated at the second acceleration, thereby realizing a focus jump to the target information surface. Since the absolute value of the second acceleration is smaller than the absolute value of the first acceleration, the focal point of light does not travel too much on the information surface, and the focal point can be reliably moved within a focus controllable range. In addition, since the position of the converging part such as a lens that determines the position of the focal point of the light does not greatly shift, it is possible to appropriately avoid the collision between the optical disc and the converging part.

  In the following, first, an optical disk loaded in the optical disk apparatus according to the present invention will be described, and then each embodiment of the optical disk apparatus will be described.

  FIG. 1A shows the appearance of the optical disc 102. The optical disk 102 is a disc-shaped recording medium such as a CD, a DVD-ROM, a DVD-RAM, a DVD-RW, a DVD-R, a + RW, a + R, or a BD that records data using a blue-violet laser. The optical disk 102 is configured by laminating a substrate 180, one or more information surfaces 184, and a protective film 188. The substrate 180 supports the information surface 184 and the protective film 188. The information surface 184 is formed of a phase change material or the like that transmits and reflects received light, and records data. The information surface 184 is provided with a plurality of tracks (not shown) formed in a spiral shape, for example, and each track is defined as a region of a groove portion or a valley portion of the information surface. Data is written in these groove or valley regions. The protective film 188 is formed of a material that transmits a light beam, and is provided to protect the information surface 184 from scratches and the like.

  FIG. 1B shows a cross section of the optical disk 102. The cross-sectional direction is a direction perpendicular to the optical disk 102 and its information surface. The thickness of this optical disk is about 1.2 mm. The breakdown is 1.1 mm for the substrate 180 and 0.1 mm (= 100 μm) including the information surface 184 and the protective film 188. The information surface 184 has three layers of L0, L1, and L2, and is arranged at intervals of 25 μm. The information surface L0 is disposed at a position of 100 μm from the surface of the protective film 188. The information surface L1 is disposed at a position of 75 μm from the surface of the protective film 188. The information surface L2 is disposed at a position of 50 μm from the surface of the protective film 188.

  An optical disc apparatus to be described later irradiates the optical disc 102 with a light beam 30 such as a laser to write data or read the written data. For reference, FIG. 1B shows a light beam 30 incident from the surface of the protective film 188 and focused on the information surface L1.

  In an optical disc, the number of information planes may differ depending on the relationship with the required storage capacity. FIG. 1C shows an example of an optical disk 102 having two layers of information surfaces L0 and L1. Even if the information surface has two layers, the thickness of the substrate 180 of the optical disk 102 and the combined thickness of the information surface 184 and the protective film 188 are the same as in the previous example. FIG. 1C also shows the light beam 30 incident from the surface of the protective film 188 and focused on the information surface L1 for reference. The optical disk 102 may have four or more information surfaces.

  In the following description, it is assumed that the optical disc 102 is loaded with the optical disc 102 having the three information surfaces L0 to L2 shown in FIG. It is assumed that the optical disc apparatus specifies the number of information planes in advance and knows where the focal point of the light beam currently exists before performing the processing according to the present invention described below.

  In the following description, it is assumed that the “focus” of the light beam includes not only a single point where the light beam is converged but also a portion of the light beam in a predetermined converged state. The “predetermined convergence state” refers to, for example, a convergence state of a light beam capable of general operations such as tracking control, data writing, and data reading obtained by the optical disc apparatus performing focus control. . This convergence state depends on, for example, the type of the optical disk 102, the width of the track provided on the information surface 184, and the like. When the focal point of the light beam is located on the information surface, the case where the converged light beam is formed on the information surface as a circular or elliptical beam spot is also included.

(Embodiment 1)
FIG. 2 shows a functional block configuration of the optical disc apparatus 100 according to the present embodiment. The optical disc apparatus 100 includes an information surface movement control unit 104, a focusing unit 110, a vertical movement unit 112, a focus detection unit 114, and a focus control unit 116.

  The information surface movement control unit 104 (hereinafter referred to as “control unit 104”) controls the operation of the optical disc apparatus 100 that accesses the optical disc 102. More specifically, the control unit 104 performs control for moving the focal point of the light beam from one information surface to the other information surface. Such movement of the focus is called interlayer jump or focus jump. In this specification, “focus jump” not only moves the focal point of the light beam from one information surface to the other information surface, but also moves the focal point of the light beam from a position other than the information surface to the information surface. Including. As for the latter, the present invention can be applied to an optical disc having a single information surface, and can also be applied to an optical disc having two or more layers. In the case of an optical disc having two or more layers, the focus is temporarily moved from a position other than the information surface to a certain information surface, and then the focus is moved to another information surface.

  The control unit 104 includes a first moving unit 106 and a second moving unit 108. For example, the first moving unit 106 performs control to move the focal point of the light beam in a certain section. This “section” is defined between the position of the focal point and the desired information surface along a direction perpendicular to the information surface. For example, the first moving unit 106 outputs an acceleration signal that gives an acceleration according to the moving direction as a control signal, and applies the acceleration signal to the vertical moving unit 112. As a result, the vertical moving unit 112 changes the position of the converging unit 110 and moves the focal point of the light beam. The second moving unit 108 generates a control signal after moving by the first moving unit 106 and similarly moves the focal point of the light beam in another section defined along the same direction as the above-described section. .

  The first moving unit 106 and the second moving unit 108 also control the moving speed when moving the focal point of the light beam. For example, after the first moving unit 106 performs control to move the focal point of the light beam at a predetermined average speed to the vicinity of another information surface, the second moving unit 108 is an optical head or objective lens that emits the light beam. Control is performed to approach the information surface at a low average speed capable of appropriately reducing the collision between the (focusing lens) and the optical disk. For example, the second moving unit 108 repeatedly performs acceleration / deceleration to realize such a low average speed. Details of processing, speed, etc. when moving the focal point of the light beam will be described later.

  In general, speed is defined by speed and direction. In this specification, the direction from the protective film 188 side of the optical disk 102 toward the information surface 184 is a positive direction, and conversely, the direction from the information surface 184 toward the protective film 188 side is a negative direction. When viewed from the optical disc apparatus 100, the positive direction is a direction approaching the optical disc 102, and the negative direction is a direction away from the optical disc 102.

  The converging unit 110 is condensing means for converging the light beam on the information surface of the optical disc 102. The focusing unit 110 is, for example, a focusing lens. The converging unit 110 may be an optical lens having an NA of 0.6 or more, or an optical lens having an NA of 0.8 or more. The vertical moving unit 112 moves the converging unit 110 in a direction substantially perpendicular to the information surface. The vertical moving unit 112 is, for example, a focus actuator 124 described later.

  The focus detection unit 114 generates a signal corresponding to the focused state of the light beam on the information surface. The focus control unit 116 drives the vertical movement unit 112 in accordance with the signal from the focus detection unit 114 to move the focus of the light beam in a direction perpendicular to the optical disc, so that the focusing state of the light beam on the information surface is substantially constant. Control to be This control is called focus control. For example, the focus control unit 116 releases the focus control before the focus jump is performed, and sets the focus control to the operating state after the focus jump. The control unit 104 controls the focus jump by driving the vertical movement unit 112.

  FIG. 3 shows an example of the hardware configuration of the optical disc apparatus 100. The optical disc apparatus 100 mainly includes an optical head 10, an optical disc controller (ODC) 20, a drive unit 30, and a disc motor 120.

  The optical head 10 is an optical system that irradiates the information surface 184 of the loaded optical disk 102 with laser light. The optical head 10 adjusts the optical system based on the drive signal from the drive unit 30, receives the laser beam reflected by the optical disc 102 in a predetermined light receiving area, and outputs a signal corresponding to the amount of light received in each light receiving area. .

  The ODC 20 controls main operations of the optical disc apparatus 100. For example, the ODC 20 generates a control signal based on the signal output from the optical head 10, moves the focal point of the light beam to the information surface of the optical disc, and performs focus control, tracking control, and the like. The ODC 20 reads out data from the optical disc 102, performs error correction and the like, and outputs it as a reproduction signal.

  The drive unit 30 generates a drive signal based on the control signal from the ODC 20 and applies it to the optical head 10.

  The disk motor 120 rotates the optical disk 102 at a predetermined number of rotations.

  Hereinafter, these components will be described more specifically.

  The optical head 10 includes a light source 122, a coupling lens 123, a focus actuator 124, a focusing lens 126, a tracking actuator 128, a deflection beam splitter 130, a condensing lens 132, a photodetector 134, and a preamplifier 136. , 138, 140, 142 and adder circuits 144, 146.

  The light source 122 outputs a light beam. The light source 122 is, for example, a semiconductor laser. The light source 122 may output a light beam having a wavelength of 680 nm or less, or may output a light beam having a wavelength of 410 nm or less. The coupling lens 123 makes the light beam from the light source 122 parallel light. The deflecting beam splitter 130 reflects the parallel light from the coupling lens 123.

  The focus actuator 124 changes the position of the focusing lens 126 in a direction substantially perpendicular to the information surface of the optical disc 102. The focusing lens 126 focuses the reflected light from the deflecting beam splitter 130 and positions the focal point on the information surface of the optical disc 102. At this time, a light beam spot is formed on the information surface. Further, the focusing lens 126 allows the reflected light from the optical disk 102 to pass. Further, the deflecting beam splitter 130 allows the reflected light from the optical disk 102 that has passed through the focusing lens 126 to pass. The tracking actuator 128 changes the position of the focusing lens 126 in a direction substantially parallel to the information surface of the optical disc 102.

  The condenser lens 132 allows the reflected light from the optical disk 102 that has passed through the focusing lens 126 and the deflecting beam splitter 130 to pass therethrough. The photodetector 134 receives the light that has passed through the condenser lens 132 and converts the optical signal into an electric signal (current signal). The photodetector 134 has, for example, a four-part light receiving region.

  The preamplifiers 136 to 142 convert the current signal from the photodetector 134 into a voltage signal. The adder circuits 144 and 146 synthesize the voltage signals from the preamplifiers 136 to 142 for each diagonal position of the photodetector 134.

  The ODC 20 includes binarization units 152 and 154, a phase comparator 156, differential amplifiers 158 and 160, a digital signal processor (DSP) 162, gain switching circuits 164 and 166, and analog / digital (AD ) Converters 168 and 170.

  The binarization units 152 and 154 receive signals from the addition circuits 144 and 146 of the optical head 10 and binarize them. The phase comparator 156 performs phase comparison of signals from the binarization units 152 and 154.

  The differential amplifier 158 inputs signals from the adder circuits 144 and 146 and outputs a focus shift signal (FE signal). The FE signal is a signal for controlling the light beam to be in a predetermined focused state on the information surface of the optical disc 102. The detection method of the FE signal is not particularly limited, and an astigmatism method may be used, a knife edge method may be used, or an SSD (spot sized detection) method may be used. It may be a thing. The circuit configuration may be appropriately changed according to the detection method.

  The differential amplifier 160 receives the signal from the phase comparator 156 and outputs a tracking error signal (TE signal). The TE signal is a signal for controlling the light beam to scan correctly on the track of the optical disk 102. The TE signal detection method is not particularly limited, and a phase difference method may be used, a push-pull method may be used, or a three-beam method may be used. The circuit configuration may be appropriately changed according to the detection method.

  The DSP 162 applies a control signal for tracking control to the drive circuit 150 in accordance with the TE signal or the like. The DSP 162 applies a control signal for focus control to the drive circuit 148 in accordance with the FE signal or the like. The operation of the DSP 162 related to the main features of the present invention will be described in detail later.

  The gain switching circuit 164 adjusts the FE signal to a predetermined amplitude (gain). The AD converter 168 converts the signal from the gain switching circuit 164 into a digital signal and outputs it to the DSP 162.

  The gain switching circuit 166 adjusts the TE signal to a predetermined amplitude (gain). The AD converter 170 converts the signal from the gain switching circuit 166 into a digital signal and outputs it to the DSP 162.

  The drive unit 30 includes drive circuits 148 and 150. The drive circuit 148 receives a control signal from the DSP 162, and drives the focus actuator 124 by applying a drive signal corresponding to the control signal. The drive circuit 150 receives a control signal from the DSP 162 and applies a drive signal corresponding to the control signal to the tracking actuator 128 to drive it.

  The above-described photodetector 134, preamplifiers 136 to 142, addition circuits 144 and 146, differential amplifier 158, gain switching circuit 164, AD converter 168, DSP 162, drive circuit 148, and focus actuator 124. Is a component for performing focus control, and realizes a focus control function.

  Further, the photodetector 134, the preamplifiers 136 to 142, the adder circuits 144 and 146, the binarization units 152 and 154, the phase comparator 156, the differential amplifier 160, the gain switching circuit 166, and the AD conversion. The device 170, the DSP 162, the drive circuit 150, and the tracking actuator 128 are components for performing tracking control, and implement a tracking control function.

  The correspondence relationship between the functional block configuration of the optical disc apparatus 100 shown in FIG. 2 and the hardware configuration of the optical disc apparatus 100 shown in FIG. 3 is as follows.

  The DSP 162 is a so-called computer, and the functions of the focus control unit 116 and the information surface movement control unit 104 shown in FIG. 2 can be realized by executing a computer program. The focusing lens 126 corresponds to the focusing unit 110 in FIG. The photodetector 134, the preamplifiers 136 to 142, the adder circuits 144 and 146, and the differential amplifier 158 correspond to the focus detection unit 114 in FIG. The drive circuit 148 and the focus actuator 124 correspond to the vertical moving unit 112 in FIG. Note that a part or all of the information surface movement control units 104 and 200 and the focus control unit 116 can be configured by hardware.

  Next, the control when the optical disc apparatus 100 according to the present embodiment causes the focus of the light beam to jump from one information surface to another information surface will be described. The optical disc apparatus 100 can perform different control depending on the direction in which the focal point of the light beam is moved. Hereinafter, a preferred control example regarding the focal speed of the light beam will be described with reference to FIGS. 4 (a) and 4 (b).

  First, the focus jump when the focal point of the light beam is present behind the information surface of the movement destination as viewed from the optical disc apparatus 100 side will be described. At this time, the focusing lens 126 moves in a direction away from the optical disk 102 to move the focal point of the light. FIG. 4A shows the moving speed of the focal point of the light beam when a focus jump is made in a direction away from the optical disk 102. Profile Pa <b> 1 indicates the focus speed controlled by the optical disc apparatus 100. For reference, a focus speed profile Pa2 by the control of a conventional optical disc apparatus is also shown.

  The optical disc apparatus 100 controls the speed of the focus by dividing the movement of the focus into sections X and Y. The moving speed of the focal point of the light beam is controlled as follows. First, in the section X, the focal point of the light beam is accelerated in a direction away from the optical disk 102, becomes constant, and then decelerates. Then, in the section Y, the speed is further reduced to 0 by reaching the target information surface by further decelerating. The absolute value of the acceleration represented by the slope of the graph in FIG. 4A is smaller during the deceleration in the section Y than during the deceleration in the section X. Further, the average focal speed in the section Y is slower than the average speed in the section X. The average speed is obtained by dividing the moving distance by the moving time. The movement distance corresponds to the area of the graph shown in FIG.

  On the other hand, a focus jump when the focal point of the light beam is present in front of the information surface of the movement destination as viewed from the optical disc apparatus 100 side will be described. At this time, the focusing lens 126 moves in a direction approaching the optical disc 102 to move the focal point of the light. FIG. 4B shows the moving speed of the focus of the light beam when the focus jump is performed in the direction approaching the optical disk 102. A profile Pb1 indicates the speed of the focus by the control of the optical disc apparatus 100. For reference, a focus speed profile Pb2 controlled by a conventional optical disc apparatus is also shown.

  The moving speed of the focal point of the light beam is controlled as follows. First, in the section X, the focal point of the light beam accelerates toward the optical disc 102, becomes constant, and then decelerates. Then, once in section Y, the speed becomes constant, and then decelerates again. The speed after the start of deceleration changes to positive, 0, negative, and 0.

  The relationship between the speed and position of the focal point of the light beam will be described. In the section where the speed changes from positive to zero (sections X and Y), the focal point of the light beam gradually decelerates as it approaches the optical disc 102. Pass through the desired information plane and stop at that point. In the section where the speed changes from 0 to negative (part of section Y), the focal point of the light beam starts to move in the opposite direction (that is, the direction away from the optical disc). Thereafter, the focal point of the light beam is gradually decelerated and stops when it reaches the target information surface. Also at this time, the optical disc apparatus 100 controls the focus speed by dividing the movement of the focus into the sections X and Y, and the average speed of the focus in the section Y is made slower than the average speed in the section X. The absolute value of the acceleration when decelerating is smaller during the deceleration in the section Y than during the deceleration in the section X. Further, the absolute value of the acceleration from the minimum value of the focal speed in the section Y to 0 is preferably smaller than the absolute value of the acceleration in the section X.

  4A and 4B, since the section Y includes a section in which the focus speed is negative, the focus moves in a direction away from the optical disc 102.

  Hereinafter, with reference to FIGS. 5 to 10, each of (1) a focus jump in a direction away from the optical disk 102 and (2) a focus jump in a direction approaching the optical disk 102 will be described in more detail. .

(1) Focus jump in a direction away from the optical disk 102 In the following, focus jump from the periphery of the information surface L0 to L2 (FIG. 1B) will be considered for easy understanding.

  FIG. 5 shows the relationship between the control signal at the time of focus jump from the information surface L0 to the information surface L2 and the focal position of the light beam. When the focal point formed by the focusing lens 126 approaches the information surface L0 from the point A, the amount of reflected light from the information surface L0 increases, and accordingly, the amplitude of the FE signal increases from approximately 0 to the negative polarity side (broken line). The amplitude of the FE signal peaks at point B and then decreases. When the focal point reaches the information surface L0 (point C), the amplitude of the FE signal becomes zero. At this time, focus control for the information surface L0 may be performed once, and then the following processing may be executed. The solid line FE signal up to point C shows a waveform when focus control is performed on the information surface L0.

  When the focal point leaves the information plane L0 and proceeds in the direction of the information plane L1, the amplitude of the FE signal increases to the positive polarity side. The amplitude of the FE signal reaches a peak at point D and then decreases to zero at point E. As the information plane L1 is further approached, the amount of reflected light from the information plane L1 increases, so the amplitude of the FE signal increases from approximately 0 to the negative polarity side. The amplitude of the FE signal decreases after peaking at point F. When the focal point reaches the information surface L1 (point G), the amplitude of the FE signal becomes zero.

  When the focal point leaves the information surface L1 and proceeds in the direction of the information surface L2, the amplitude of the FE signal increases toward the positive polarity. The amplitude of the FE signal reaches a peak at the H point and then decreases to zero at the I point. As the information plane L2 is further approached, the amount of reflected light from the information plane L2 increases, so that the amplitude of the FE signal increases from approximately 0 to the negative polarity side. The amplitude of the FE signal increases after reaching a minimum at point J. When the focal point reaches the information plane L2 (point K), the amplitude of the FE signal becomes zero. When the focal point leaves the information plane L2, the amplitude of the FE signal increases to the positive polarity side, peaks at the point L, and then decreases. As shown in FIG. 5, the waveform of the FE signal draws an S shape when the focal point moves around the information planes L0 to L2. Such a signal is also referred to as an S-shaped signal based on its waveform.

  Next, control signals for performing the above-described focus jump operation will be described. When the focus jump from the information surface L0 to the information surface L2, the DSP 162 generates an acceleration signal and a deceleration signal that are control signals. The drive circuit 148 drives the focus actuator 124 based on the control signal, and moves the focal point in the range of the section X. The acceleration signal is a signal that gives acceleration in the acceleration direction, and the deceleration signal is a signal that gives acceleration in the deceleration direction.

  In this specification, the direction away from the optical disk 102 is set to a negative direction. Therefore, it is assumed that when the DSP 162 generates a negative signal, the focal point moves in a direction away from the optical disc 102, and when a positive signal is generated, the focal point moves in a direction approaching the optical disc 102. In the following description, when the DSP 162 generates a signal, the signal is applied to the drive circuit 148, and the drive circuit 148 applies a drive signal to the focus actuator 124 based on the signal. As a result, the position of the focusing lens 126 is changed by the focus actuator 124, and the focal point of the light beam is moved.

  First, when the DSP 162 performs focus control so as to follow the information surface L0, for example, the focus control is held. Next, the DSP 162 generates a negative acceleration signal for a predetermined time while holding the focus control. By this acceleration signal, the focal point starts to move from the information surface L0 toward the information surface L2. The generation of the acceleration signal ends between the information planes L0 and L1. Even if the acceleration signal is not generated, the focusing lens 126 continues to move due to inertia, so that the focal point also continues to move in the direction of the information surface L2 at a substantially constant speed.

  Thereafter, the DSP 162 generates a deceleration signal. The generation of the deceleration signal ends between the information planes L1 and L2. When the generation of the deceleration signal is completed, the focus speed is not zero, and the focus continues to move in the direction of the information L2. That is, the DSP 162 adjusts the magnitude and generation time of the deceleration signal so that the speed obtained by the acceleration signal is not zero.

  The vicinity (point M) of the information surface L2 where the DSP 162 finishes generating the deceleration signal is located in a region (between the point J and the point L) in which the focus control on the information surface L2 is possible. The point M is a position in the vicinity of the point J, for example. The generation start position of the deceleration signal is not particularly limited, and may be, for example, a substantially intermediate position between the information surface L0 and the information surface L2. Needless to say, there is no collision between the focusing lens 126 and the optical disk 102 at the point M.

  Next, the DSP 162 controls the section Y (from M point to K point). That is, the DSP 162 generates a control signal for causing the focal point to approach the information surface L <b> 2 at an average speed slower than the average speed of the section X to the drive circuit 148. As shown in FIG. 6, this control signal includes a pulse signal (pulse train) having both polarities for acceleration and deceleration. That is, the acceleration increases when an acceleration pulse is applied, and the acceleration decreases when a deceleration pulse is applied. FIG. 6 shows waveforms and timings of control signals for acceleration and deceleration applied in the sections X and Y. In this pulse train, positive and negative pulses alternately change with respect to the reference. The timing at which the DSP 162 finishes generating the pulse train may be when the focal point reaches the information plane L2, may reach a point N near the information plane L2, or may slightly pass through the information plane L2. It may be the point when the point O is reached. In other words, the section Y may be from point M to point K, from point M to point N, or from point M to point O. After the section Y, the DSP 162 starts focus control following the information surface L2. The DSP 162 controls the focus jump by generating an acceleration signal and a deceleration signal as described above.

  Next, a procedure when the optical disc apparatus 100 performs a focus jump in a direction away from the optical disc 102 will be described with reference to FIGS. FIG. 7 shows a procedure of focus jump control according to the present embodiment. In this focus jump control, first, the first moving unit 106 controls the movement of the focal point in the section X in step S100. Next, in step S102, the second moving unit 108 controls the movement of the focal point in the section Y. This control will be described in more detail.

  FIG. 8 shows a detailed processing procedure of focus jump control according to the present embodiment. The following processing is mainly performed by the DSP 162 that implements the functions of the first moving unit 106 and the second moving unit 108.

  The DSP 162 stops tracking control in step S110 and holds a drive signal for focus control in step S112. Next, in step S <b> 114, the DSP 162 generates an acceleration pulse train and applies it to the focus actuator 124 via the drive circuit 148. Subsequently, in step S116, the DSP 162 switches the gain setting value of the gain switching circuit 164 to a value corresponding to the jump destination information surface L2, and in step S118, a level at which focus control can be performed according to the jump destination information surface L2. Set. As a result, the S-shaped signal of the focus jump destination information surface L2 and the level at which focus control is possible can be detected correctly. The gain setting value and the focus controllable level are defined in advance for each information surface, and are held in a nonvolatile memory (not shown) or the like.

  Next, the DSP 162 generates a deceleration pulse train in step S 120 and applies it to the focus actuator 124 via the drive circuit 148. In step S122, it is determined whether or not the section X has ended, that is, whether or not the focal point has reached the point M. Whether or not the focal point has reached point M can be determined by monitoring an FE signal whose waveform is obtained in advance. Specifically, the DSP 162 recognizes that the position of the first zero cross point when the FE signal changes from negative to positive is the C point, and then the FE signal changes again from negative to positive. The position of the second zero-crossing point is recognized as the G point. As a result, the DSP 162 can determine that the position corresponding to the subsequent minimum value is the J point. Note that the DSP 162 may make a determination based on other signals such as an all-optical (AS) signal or an envelope of an RF signal.

  When the DSP 162 determines that the focal point has reached the point M, the application of the deceleration pulse train is ended in step S124, and the application of the acceleration / deceleration bipolar pulse train is started in step S126.

  Thereafter, in step S128, the DSP 162 determines whether or not the FE signal has reached the focus controllable level of the information plane L2 that is the focus jump destination. When it is determined that it has not reached, the process of step S126 is continued, and when it is determined that it has reached, the process proceeds to step S130.

  In step S130, the DSP 162 ends the application of the pulse train, releases the hold of the drive signal for focus control, and sets the focus control to the operating state. Thereby, stable focus control becomes possible. In step S132, when the DSP 162 confirms that the focus control has been started normally based on a signal such as a TE signal or an RF signal, the tracking control is set to the operating state in step S134. Thereafter, a predetermined track / sector address is searched and data is reproduced.

  The focus jump that the focusing lens 126 moves away from the optical disk 102 is not limited to the focus jump from the information surface L0 to the information surface L2, but for example, the focus jump from the information surface L0 to the information surface L1 and from the information surface L1 to the information surface L2. Similarly, a focus jump is possible.

(2) Focus jump in the direction approaching the optical disc 102 In the following, in order to facilitate understanding, a focus jump from the periphery of the information surface L2 to L0 (FIG. 1B) will be considered.

  FIG. 9 shows the relationship between the control signal at the time of focus jump from the information surface L2 to the information surface L0 and the focal position of the light beam. When the focal point formed by the focusing lens 126 approaches the information surface L2 from the point A on the protective film 188 side, the amount of reflected light from the information surface L2 increases, and accordingly, the amplitude of the FE signal increases from approximately 0 to the negative polarity side. To do. The amplitude of the FE signal peaks at point B and then decreases. When the focal point reaches the information surface L2 (point C), the amplitude of the FE signal becomes zero. At this time, focus control for the information surface L2 may be performed once, and then the following processing may be executed. The solid line FE signal up to point C shows a waveform when focus control is performed on the information surface L2.

  When the focal point leaves the information surface L2 and proceeds in the direction of the information surface L1, the amplitude of the FE signal increases to the positive polarity side. The amplitude of the FE signal reaches a peak at point D and then decreases to zero at point E. As the information plane L1 is further approached, the amount of reflected light from the information plane L1 increases, so the amplitude of the FE signal increases from approximately 0 to the negative polarity side. The amplitude of the FE signal decreases after peaking at point F. When the focal point reaches the information surface L1 (point G), the amplitude of the FE signal becomes zero.

  When the focal point leaves the information surface L1 and proceeds in the direction of the information surface L0, the amplitude of the FE signal increases to the positive polarity side. The amplitude of the FE signal reaches a peak at the H point and then decreases to zero at the I point. As the information plane L0 is further approached, the amount of reflected light from the information plane L0 increases, so the amplitude of the FE signal increases from approximately 0 to the negative polarity side. The FE signal increases after becoming minimum at point J. When the focal point reaches the information surface L0 (point K), the amplitude of the FE signal becomes zero.

  Next, the focal point moves past the information plane L0. Along with this movement, the amplitude of the FE signal increases toward the positive polarity and peaks at the point P, and then gradually decreases to 0 (point M). After that, when the focal point moves in the opposite direction (the direction away from the optical disc 102), the amplitude of the FE signal increases from approximately 0 to the plus polarity side again. After reaching the peak at the point N, it decreases and reaches a level where focus control is possible (point O), and the focus jump ends and shifts to the focus control operation.

  Since the above point M is at the deepest position from the surface of the optical disk 102, the focusing lens 126 is closest to the optical disk 102 when the focal point reaches the above point M. However, in the optical disc apparatus 100 of this embodiment, the focusing lens 126 and the optical disc 102 do not collide. This is because the distance between the focusing lens 126 and the optical disk 102 is about 100 μm, whereas the position of the point M is only a few μm away from the information surface L0. Further, after passing the peak point P, the focal point moving speed gradually decreases and becomes zero at the point M, so that the position of the point M does not fluctuate greatly due to overshoot or the like.

  Next, control signals for performing the above-described focus jump operation will be described. When performing a focus jump from the information surface L2 to the information surface L0, the DSP 162 applies an acceleration signal and a deceleration signal to the drive circuit 148 and moves the focal point in the range of the section X. When the focus moves in the section X, it is the same as the control signal at the time of focus jump from the information surface L0 to the information surface L2, except that the polarities of the acceleration signal and the deceleration signal are reversed. Therefore, hereinafter, a control signal when the focal point moves in the range of the section Y will be described.

  When the point K is reached, the DSP 162 finishes applying the deceleration signal, and the optical disc apparatus 100 enters a wait state in which no control signal is generated. However, since the focusing lens 126 continues to move with inertia even when the deceleration signal is no longer applied, the focal point continues to move at a substantially constant speed beyond the information surface L0. As a result, the amplitude of the FE signal also increases to the positive polarity side and peaks at the point P.

When passing the peak point P, the DSP 162 generates a deceleration pulse train for decelerating the moving speed of the focal point. As a result, the focusing lens 126 receives acceleration in the opposite direction (the direction away from the optical disk 102), and the focal point is decelerated.
The motor decelerates and stops until the position where the FE signal crosses zero (M point). The DSP 162 continues to generate the deceleration pulse train thereafter. As a result, the focal point is again pulled back toward the information plane L0, and the amplitude of the FE signal again increases toward the positive polarity side. The amplitude of the FE signal peaks at point N and then decreases. The DSP 162 further generates deceleration pulses until an FE signal capable of focus control is obtained. Thereafter, the DSP 162 starts focus control following the information surface L0.

  When the amplitude of the FE signal passes the peak (P point) and further crosses zero (M point), it is generally impossible to perform focus control on the information surface L0. However, it is clear that when the focal point of the light beam is moved in the opposite direction, a peak appears again in the FE signal and then zero-crosses. It is also clear that the predetermined range including the zero cross is a range in which focus control is possible. Therefore, even from the point M where focus control cannot be performed, the optical disc apparatus 100 can move the focus in the reverse direction and monitor the FE signal, thereby enabling focus control on the information surface L0. In order to operate more reliably, the optical disc apparatus 100 holds the peak value of the FE signal, and when the focus is moved in the reverse direction, the peak value can be compared with the value of the FE signal to control the focus. It is determined whether or not the range has been returned.

  Next, a procedure when the optical disc apparatus 100 performs a focus jump in a direction approaching the optical disc 102 will be described. Although this procedure is also represented by FIG. 7, since it has already been described, it is omitted here.

  FIG. 10 shows a detailed processing procedure of focus jump control according to the present embodiment. In FIG. 10, processes in the same section X as those in FIG. 8 are denoted by the same reference numerals and description thereof is omitted. Hereinafter, processing in the section Y after step S226 performed mainly by the DSP 162 will be described.

  After completing the application of the deceleration pulse, the DSP 162 enters a wait state in which a control signal is not generated for a certain period in step S226, and detects the FE signal. This wait state continues until an S-shaped peak (point P in FIG. 9) appears in the FE signal. If it is determined that an S-shaped peak has appeared in the FE signal, in step S230, the DSP 162 records the peak value, and in step S232, calculates the focus control level of the information plane L0 that is the focus jump destination. Thereafter, in step S234, a reverse rotation pulse for returning the focal point to the information surface L0 side is given to the drive circuit 148 until a focus controllable level is detected. The DSP 162 determines that the level of the FE signal after being equal to the held peak value is a focus controllable level. Thereafter, the DSP 162 executes Steps S130, S132, and S134. Since the contents of steps S130, S132, and S134 have already been described with reference to FIG. 8, the description thereof will be omitted.

  Note that the focus jump in which the focusing lens 126 approaches the optical disk 102 is not limited to the focus jump from the information surface L2 to the information surface L0. For example, the focus jump from the information surface L2 to the information surface L1 and the information surface L1 to the information surface L0. Similarly, a focus jump is possible.

  In any of the focus jump processes (1) and (2) described above, the position where the deceleration signal is applied or the timing thereof is not particularly limited. For example, the application of the deceleration signal may be started when the focal point reaches a position approximately in the middle between the information surface L0 and the information surface L2.

  Further, in the present embodiment, the focus jump process is varied depending on the direction away from the optical disc 102 and the direction approaching the optical disc 102, but this is a preferred example, and other examples may be adopted. . For example, the optical disc apparatus 100 may always perform the focus jump process according to the above (1), or may always perform the focus jump process according to the above (2).

(Embodiment 2)
FIG. 11 shows a functional block configuration of the optical disc apparatus 201 according to the present embodiment. The optical disc apparatus 201 includes an information surface movement control unit 200, a focusing unit 110, a vertical movement unit 112, a focus detection unit 114, and a focus control unit 116. The same components as those of the optical disc apparatus 100 shown in FIG. The optical disc apparatus 201 can be used as an alternative to the optical disc apparatus according to the first embodiment. Below, description of a common component is abbreviate | omitted. The optical disc apparatus 201 can perform the operations of the optical disc apparatus 100 according to the first embodiment, for example, the focus jump processes (1) and (2) in the first embodiment. At this time, it is assumed that the processing is performed instead or additionally in the points described below.

  The information surface movement control unit 200 includes a first moving unit 106 and a second moving unit 202. Among these, the 2nd moving part 202 performs moving speed control according to the signal of the focus detection part 114. FIG. For example, the second moving unit 202 detects the separation distance between the information surface and the focal point of the light beam based on the signal level of the focus detection unit 114. FIG. 12 shows a first example of a control signal applied by the second moving unit 202 in the section Y. The second moving unit 202 controls the number of pulses of the pulse train applied at the time of the focus jump according to the FE signal from the focus detection unit 114. As the number of pulses increases, the focusing unit 110 is controlled more precisely. Thereby, the second moving unit 202 can change the pulse interval according to the distance from the focal point to the information surface of the focus jump destination. For example, the second moving unit 202 can reduce the pulse interval as the focal point approaches the information surface of the focus jump destination. Thereby, appropriate focus jump control according to the distance between the focal point and the information surface can be performed in the vicinity of the information surface of the jump destination.

  FIG. 13 shows a second example of the control signal applied by the second moving unit 202 in the section Y. As illustrated in FIG. 13, the second moving unit 202 may control the pulse height of the pulse train in accordance with the signal from the focus detection unit 114. The pulse height is the magnitude of the pulse signal value. For example, the acceleration of the focusing unit 110 increases as the pulse height increases, and the acceleration decreases as the pulse height decreases. Thereby, the second moving unit 202 can change the height of the pulse in accordance with the distance from the focal point of the light beam to the information surface of the focus jump destination. For example, the second moving unit 202 can reduce the pulse height as the focal point approaches the jump destination information surface. Thereby, appropriate focus jump control according to the distance between the focal point and the information surface can be performed in the vicinity of the information surface of the jump destination.

  FIG. 14 shows a third example of the control signal applied by the second moving unit 202 in the section Y. As illustrated in FIG. 14, the second moving unit 202 may control the pulse width of the pulse train signal according to the signal from the focus detection unit 114. The pulse width is the time length during which a pulse is applied. For example, the moving speed of the focusing unit 110 increases as the pulse width increases, and the increase in speed decreases as the pulse width decreases. As a result, the second moving unit 202 can change the pulse width according to the distance from the focal point of the light beam to the jump destination information surface. For example, the second moving unit 202 can reduce the pulse width as the focal point approaches the jump destination information surface. Thereby, appropriate focus jump control according to the distance between the focal point and the information surface can be performed in the vicinity of the information surface of the jump destination.

  Next, another example of the control signal that can be used in both the optical disc apparatus 100 according to the first embodiment and the optical disc apparatus 201 according to the second embodiment will be described. FIG. 15 shows an example of control signals applied in the sections X and Y. The first moving unit 106 may control the movement of the focal point of the light beam to stop once after the end of the section X. Thereby, the collision between the focusing unit 110 (the focusing lens 126) and the optical disc 102 is further reduced. At this time, the second moving units 108 and 202 generate the deceleration pulse in the section Y to the extent that the acceleration pulse is not canceled out. As a result, the once stopped focus can be moved again toward the jump destination information surface. After starting the movement again, the vehicle slowly decelerates until it enters the focus controllable range, and stops when it enters the focus controllable range. The magnitude of the acceleration before the second stop is preferably smaller than the magnitude of the acceleration before the first stop.

  FIG. 16 shows an example of a control signal applied in the section Y. The second moving units 108 and 202 can generate a control signal that intermittently repeats deceleration in the section Y. As a result, the focal point of the light beam approaches the information surface and the moving speed of the focal point can be appropriately reduced, and the risk of collision between the converging unit 110 (the converging lens 126) and the optical disc 102 is further reduced.

  FIG. 17 shows an example of the control signal applied in the section X. As shown in FIG. 17, the first moving unit 106 may perform control for decelerating immediately after acceleration in the section X. In addition, as shown in FIG. 18, after the control by the first moving unit 106, there may be an interval before the control by the second moving units 108 and 202 is started. Further, as shown in FIG. 19, the second moving units 108 and 202 may provide an interval between each pulse in the section Y. Alternatively, the second moving units 108 and 202 may be controlled to perform deceleration after acceleration and to accelerate after deceleration. Further, the second moving units 108 and 202 may output the acceleration pulse and the deceleration pulse once each instead of outputting the pulse train.

  The first moving unit 106 may end the application of the acceleration signal in the section X according to a detection signal such as an FE signal. Moreover, the 1st moving part 106 may perform acceleration of the area X several times, and may perform deceleration several times. For example, in the section X, a plurality of acceleration pulses may be output or a plurality of deceleration pulses may be output. In this case, acceleration and deceleration may be repeated alternately, or acceleration may be continued intermittently and then deceleration may be continued intermittently.

  The second moving units 108 and 202 may monitor the moving speed of the focal point of the light beam. For example, in step S128 of FIG. 8, the second moving units 108 and 202 determine whether or not the moving speed of the focus is within a predetermined speed range. If the moving speed of the focal point is not within the predetermined speed range, the process returns to step S126. If the moving speed of the focal point is within the predetermined range, the process proceeds to step S130. Further, the control of this embodiment may be arbitrarily combined.

  The DSP 162 implements a focus jump operation by executing a computer program stored in a computer-readable recording medium (not shown) such as a ROM or RAM. Such a computer program includes, for example, instructions for executing the processes defined in the flowcharts shown in FIGS. The computer program can be recorded on a recording medium such as an optical recording medium typified by an optical disk, an SD memory card, a semiconductor recording medium typified by an EEPROM, or a magnetic recording medium typified by a flexible disk. The optical disc apparatus 100 can acquire a computer program not only via a recording medium but also via an electric communication line such as the Internet.

  The DSP 162 can be distributed alone. The DSP 162 can be mounted on, for example, a device having components other than the DSP 162 shown in FIG. 3 to cause the device to function as an optical disk device.

  According to the optical disk apparatus of the present invention, since the focal position of the light beam can be controlled with high accuracy, an accurate focus jump can be realized for any information surface of an optical disk having a plurality of information surfaces. In addition, according to the optical disk device or the like according to the present invention, collision between the focusing means such as a lens and the optical disk can be appropriately reduced, and thus it is possible to avoid both the lens and the optical disk from being damaged.

(A) is an external view of the optical disc 102, (b) is a cross-sectional view of the three-layer optical disc 102, and (c) is a cross-sectional view of the optical disc 102 having the two-layer information surfaces L0 and L1. 1 is a block diagram of an optical disc apparatus 100 according to Embodiment 1. FIG. 2 is a diagram illustrating an example of a hardware configuration of an optical disc device 100. FIG. (A) is a figure which shows the movement speed of the focus of the light beam when performing a focus jump in a direction away from the optical disk 102, and (b) is the movement of the focus of the light beam when performing a focus jump in a direction approaching the optical disk 102. It is a figure which shows speed. The relationship between the control signal at the time of the focus jump from the information surface L0 to the information surface L2 and the focal position of the light beam is shown. It is a figure which shows the waveform and timing of the control signal for the acceleration and deceleration which are applied in the area X and Y. It is a flowchart which shows the procedure of the focus jump control by 1st Embodiment. It is a flowchart which shows the detailed process sequence of the focus jump control by 1st Embodiment. It is a figure which shows the relationship between the control signal at the time of the focus jump from the information surface L2 to the information surface L0, and the focus position of a light beam. It is a flowchart which shows the detailed process sequence of the focus jump control by 1st Embodiment. 2 is a block diagram of an optical disc device 201. FIG. 6 is a diagram illustrating a first example of a control signal applied by a second moving unit 202 in a section Y. FIG. 12 is a diagram illustrating a second example of a control signal applied by the second moving unit 202 in a section Y. FIG. 12 is a diagram illustrating a third example of a control signal applied by the second moving unit 202 in a section Y. FIG. It is a figure which shows the example of the control signal applied in the area X and Y. 6 is a diagram illustrating an example of a control signal applied in a section Y. FIG. 6 is a diagram illustrating an example of a control signal applied in a section X. FIG. It is a figure which shows the example of the control signal in which the time interval exists between the area X and the area Y. It is a figure which shows the example of the control signal for decelerating after acceleration and accelerating after decelerating.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,201 Optical disk apparatus 102 Optical disk 104,200 Information surface movement control part 106 1st movement part 108,202 2nd movement part 110 Focusing part 112 Vertical movement part 114 Focus detection part 116 Focus control part

Claims (12)

An optical disc apparatus that performs focus control on a plurality of information surfaces provided on an optical disc,
A light source;
A focusing section for focusing the light from the light source;
Based on the control signal, the position of the converging unit is changed in a direction perpendicular to the information surface of the optical disc, and the moving unit moves the focal point of the light,
A light receiving unit that receives reflected light from the information surface in a plurality of regions, and generates a plurality of signals according to the amount of light received in each region;
A signal generator that generates a focus error signal based on the plurality of signals;
A control unit that generates the control signal based on the focus error signal, wherein the control signal is a signal for moving the focal point of the light to a range in which focus control can be performed on the information surface. And
Have
The control unit generates a first control signal for decelerating the focal point of the light with a first acceleration with respect to the information surface, and a second control signal for decelerating with a second acceleration in a second interval thereafter,
The absolute value of the second acceleration is smaller than the absolute value of the first acceleration,
When the focus is moved to the information surface in the direction away from the optical disk, the second error signal is generated by the acceleration pulse and the deceleration pulse train when the focus error signal for the target information surface takes the first extreme value. Generate control signals,
When moving the focal point to an information surface in a direction approaching the optical disc, a deceleration pulse train is generated after the focus error signal for the target information surface takes a second extreme value.
Optical disk device. The moving unit changes the position, acceleration, and speed of the focusing unit based on the number, magnitude, and applied time length of the first and second pulses applied,
Wherein the control unit, the number of the first pulse and the second pulse, the size, by adjusting at least one of the time length to be applied to generate the control signal, the optical disk apparatus according to claim 1. The optical disc has a plurality of the information surfaces,
The optical disc apparatus according to claim 1, wherein the control unit generates a control signal for moving the focus of the light from an information surface on which focus control is performed to a range in which focus control is possible with respect to another information surface. .   The control unit is a control signal for changing the position of the converging unit in a direction away from the optical disc, and the focus of the light is moved when the focus of the light first enters a range in which the focus control is possible. The optical disc apparatus according to claim 1, wherein a control signal for stopping is generated.   The control unit generates a control signal for changing the position of the focusing unit in a direction approaching the optical disc until the focal point of the light first passes through the range where the focus control is possible, and then moves away from the optical disc. The optical disk apparatus according to claim 1, wherein a control signal for changing a position of the converging unit in a direction is generated. The controller is
Until the focal point of the light first passes through the range in which the focus control is possible, a control signal for decelerating the focal point of the light with the first acceleration and then decelerating with the second acceleration is generated.
The optical disc apparatus according to claim 4 , wherein a control signal for stopping movement of the focus of the light is generated when the focus of the light passes through a range where the focus control is possible. The control unit generates a control signal for decelerating with the first acceleration and stopping the movement of the focal point of the light when moving the focal point to the information surface in a direction away from the optical disc , and then again in the same direction It is moved, and generates a control signal for decelerating in the second acceleration, an optical disk apparatus according to claim 1 or 2. Wherein the control unit, while generating the control signal stops the focus control on the information plane, the optical disk apparatus according to claim 1 or 2. The optical disc apparatus according to claim 7 , wherein the control unit starts focus control after moving the focus of the light to a range in which focus control is possible with respect to the information surface. In an optical disc apparatus that performs focus control on a plurality of information surfaces provided on an optical disc, a focus movement method for moving the focus of light to a range where focus control is possible,
The optical disc apparatus is
A light source;
A focusing section for focusing the light from the light source;
Based on the control signal, the position of the converging unit is changed in a direction perpendicular to the information surface of the optical disc, and the moving unit moves the focal point of the light,
A light receiving unit that receives reflected light from the information surface in a plurality of regions, and generates a plurality of signals according to the amount of light received in each region;
A signal generation unit that generates a focus error signal based on the plurality of signals, and
A first step of generating a control signal for decelerating the focal point of the light at a first acceleration with respect to the information surface based on the focus error signal, and applying the control signal to the moving unit;
A second step of generating a second control signal for decelerating the focal point of the light with a second acceleration after the first step, and applying the second control signal to the moving unit;
The absolute value of the second acceleration is smaller than the absolute value of the first acceleration,
When the focus is moved to the information surface in the direction away from the optical disk, the second error signal is generated by the acceleration pulse and the deceleration pulse train when the focus error signal for the target information surface takes the first extreme value. Generate control signals,
A second step of generating a deceleration pulse train after the focus error signal for the target information surface takes a second extreme when moving the focus to the information surface in a direction approaching the optical disc ; A method of moving the focus. A light source;
A focusing section for focusing the light from the light source;
Based on the control signal, the position of the converging unit is changed in a direction perpendicular to the information surface of the optical disc, and the moving unit moves the focal point of the light,
A light receiving unit that receives reflected light from the information surface in a plurality of regions, and generates a plurality of signals according to the amount of light received in each region;
A processor mounted on an optical disc apparatus comprising: a signal generation unit that generates a focus error signal based on the plurality of signals;
The processor is
A first step of generating a control signal for decelerating the focal point of the light at a first acceleration with respect to the information surface based on the focus error signal from the signal generation unit, and applying the control signal to the moving unit;
A second step of generating a second control signal for decelerating the focal point of the light at a second acceleration and applying the second control signal to the moving unit;
The absolute value of the second acceleration is smaller than the absolute value of the first acceleration,
When the focus is moved to the information surface in the direction away from the optical disk, the second error signal is generated by the acceleration pulse and the deceleration pulse train when the focus error signal for the target information surface takes the first extreme value. Generate control signals,
A second step of generating a deceleration pulse train after the focus error signal for the target information surface takes a second extreme when moving the focus to the information surface in a direction approaching the optical disc ;
Processor to run . A computer program executed in an optical disc apparatus that performs focus control on a plurality of information surfaces provided on an optical disc, the optical disc apparatus comprising: a light source;
A focusing section for focusing the light from the light source;
Based on the control signal, the position of the converging unit is changed in a direction perpendicular to the information surface of the optical disc, and the moving unit moves the focal point of the light,
A light receiving unit that receives reflected light from the information surface in a plurality of regions, and generates a plurality of signals according to the amount of light received in each region;
Have a control unit for generating the control signal based on the focus error signal and the signal generator for generating a focus error signal based on the plurality of signals, the computer program, to the control unit,
A first step of generating a control signal for decelerating the focal point of the light at a first acceleration with respect to the information surface based on the focus error signal, and applying the control signal to the moving unit;
A second step of generating a second control signal for decelerating the focal point of the light with a second acceleration after the first step, and applying the second control signal to the moving unit;
The absolute value of the second acceleration is smaller than the absolute value of the first acceleration,
When the focus is moved to the information surface in the direction away from the optical disk, the second error signal is generated by the acceleration pulse and the deceleration pulse train when the focus error signal for the target information surface takes the first extreme value. Generate control signals,
A second step of generating a deceleration pulse train after the focus error signal for the target information surface takes a second extreme when moving the focal point to the information surface in a direction approaching the optical disc ; A computer program that executes

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