DE19536190A1 - Optical disk drive with radially transported optical head - Google Patents

Abstract

The device has an optical head directing a light beam onto the recording medium surface to read or write information. The disc drive has an objective lens actuator and a lens acceleration sensor. A seek control section directs the optical beam to a target track at a predetermined control speed and a constant lens actuator speed. The seek control section decelerates the lens actuator on the basis of the measured acceleration if the light beam reaches a track position which is a predetermined number of tracks before the target track.

Description

Background of the Invention

The present invention relates to an opti cal plate device for moving a light beam spot tes, which is emitted by an optical head a target track of a disk media surface through a Search control, and especially on an optical disc device and its search control method in which a deceleration control when the optical head approaching a target track is optimized.

So far, according to an optical disc device an optical head mounted on a trolley, which by a Voice coil motor in the radial direction of a disk medium is moved. The optical head converges a laser beam through an objective lens and forms a microbeam spot on the media surface. The objective lens is replaced by a Lens actuator driven and moved the beam point in radial direction of the plate. An area where the Beam point can be moved by a lens actuator, is so narrow to, for example, 32 tracks on one side be. One movement of the beam point, the 32 tracks exceeds, is carried out by the carriage.

If a search command from a higher value device is received, the optical disk device inserts one Search control for moving the beam point of the optical Head to a track address that is used as a command parameter was received. The search control is mainly under divides into a rough control, mainly to the car move, a fine control to mainly the lenses actuate to move, and a deceleration control to set the speed to zero on a target track. As for those controls and the switching operation,  if the number of remaining tracks (difference) for the Target track, for example, exceeds 32 tracks, the rough one control executed, and if the number of remaining Tracks is equal to or less than 32 tracks, the fine will control executed. In a state where the Track control of the lens actuator is released, lead the rough control and the fine control the speed speed control based on a predetermined goal speed table. During the speed control is the number of tracks that the head passes has, from a zero crossing detection signal of the Spurver known error signal and the number of lead traces up to the target track are monitored. If the Number of tracks left a specified value reached, the deceleration control is executed. To the The end of the deceleration control reaches Beam point of the optical head ideally the target track, and the speed is zero.

When the deceleration control is finished, on Control mode of the lens actuator on position control the target track is switched and a servo feed is released leads to move the beam point onto the target track. If a slowdown and an acceleration of the lenses actuator have already been known, will be used in the Ver slowdown control before a deceleration start position get the target lane, and an ideal deceleration control tion can be carried out.

With such a search control of the conventional opti plate device will accelerate the Lens actuator is determined at the stage of construction a predetermined acceleration for all devices set together and becomes the deceleration control executed. In the actual device the lens has actuator of the optical head, however, due to one  Acceleration power that is inherent in the lens actuator, a coil current, an eccentricity of the medium, one Difference of an assembly state, a fluctuation of dimensions (apparently within an allowable accuracy) or the like, an acceleration inherent in the device is, although such an acceleration within one Range of acceleration power is in the stage the construction is required. That is why at the firm certain acceleration the acceleration power that the device is not taken into account. There are such problems that in the presence of a large swan kung the deceleration control is insufficient or, in In contrast, the deceleration control is excessive is executed and entering the target lane tert, and search performance deteriorates due to a repeat related to a search error.

Summary of the invention

According to the invention there are optical disks direction and a search control process provided at considering the optimal deceleration control an acceleration performance that can be performed is inherent to the device.

According to an optical disk device of the invention is an optical head (optical scanner) on a trolley mounted in the radial direction of a disk medium is moved. According to the optical head is on a media surface of the disc medium through an objective lens Light beam spot formed, making information optically be read and written. The objective lens is through driven a lens actuator (tracking actuator) and moves the light beam point in the radial direction of the Plate.

Regarding such an optical disk device  the invention by the presence of an acceleration marked measuring section, to obtain an acceleration α, which is specific to the lens operator, on the basis of a Movement speed when the lens actuator accelerates is controlled by inclination.

A search control section moves the light beam spot of the optical head by a predetermined speed speed control and a constant speed control of the lens actuator to a target track. If the light beam point reaches a position that is a predetermined one Number of tracks in front of the target track, the Lens actuator slow controlled, based on the Acceleration by an accelerometer section was measured, and the light beam point becomes the end time point of deceleration control led to the target lane.

The accelerometer section of the invention receives one Acceleration α that is inherent in the lens actuator by a track jump to move the light spot from that optical head is running on the adjacent track. At the track jump after the on-track control of the Lens actuator was suppressed, the acceleration control is only carried out for a predetermined time Tx the control mode to the constant speed control tion switched, and a waiting time Ty until the light beam point after the end of acceleration the track position 0.5 is reached, is measured. Furthermore, after waiting for the same Time as the waiting time Ty from the track position 0.5 the Slowdown for the same predetermined time as that Acceleration time Tx executed, and the control mode is switched to the on-track control.

The acceleration α that is inherent in the lens actuator is by the following equation based on the Measurement waiting time Ty is calculated, assuming that a Track spacing is equal to (C) and an acceleration time  is equal to Tx.

The acceleration measuring section measures an acceleration many times and gets its own acceleration from the Average of the measurement results. For example, the Accelerometer measurement many times in a predetermined one Run on the inner side of the disk medium. The acceleration measurement is made many times in one specific track on the outer side. The special acceleration α is obtained from the average of the Obtain a large number of measurement results. The acceleration measuring section carries out the acceleration measurement of the lens bed tigers at a reset position of a track eccentricity in radial direction of the disk medium. More specifically, the optical head uses a lens position sensor to detect a position of an objective lens by the lens actuator is driven. In a state at which the light beam point of the optical head by a On-track control of the lens actuator of the track eccentric acted in the radial direction of the disk medium the accelerometer section monitors a lens position signal from the lens position sensor and measures one Acceleration of the lens actuator at one position which is an increase / decrease direction of the lens position signals changes. Such an operation is equivalent to when the lens position signal from the lens position sensor is differentiated and the acceleration measurement of the Lens actuator at a position where a differentiation signal is set to 0. Furthermore leads the acceleration measurement section the acceleration measurement of the Lens actuator when a plate medium in the front direction is used. The accelerometer section  leads the acceleration measurement of the lens actuator a wait state from a command from a higher order Device off. Furthermore, the acceleration leads measuring section the acceleration measurement of the lens actuator if a search error occurs and updates one Acceleration required for a deceleration control one next search retry operation is used.

When the light beam spot reaches a position located a predetermined number of tracks in front of a target track determined by an acceleration performance of the lens actuator, a search control section measures a track passing time (T) and obtains a moving speed (V), and then receives Use of the speed of movement (V) and the measurement acceleration a a deceleration time TB to the target track. Finally, the search control section receives a waiting time TW until the start of the deceleration from a time of the end of the measurement of the lane passing time by the measuring time (T) and deceleration time TB and operates the lens actuator 25 for a period of the deceleration time TB from the elapse of the waiting time TW in a deceleration controlled manner. Assuming that a passage time of one lane is (T) and a deceleration time is TB, the waiting time TW is calculated by

TW = (3T - TB) / 2.

The invention also provides a search control method the optical disk device. The search control ver driving is carried out by the following procedure.

I. Accelerometer step

The acceleration α that the lens actuator is peculiar, based on the speed of movement get when the lens actuator to move the light radial point on the surface of the disc media Direction of the plate is accelerated by the lens  lens of the optical head mounted on the carriage which is moved in the radial direction of the disk medium, is driven.

II. Search step

The light beam point of the optical head is by a predetermined speed control and Constant speed control of the lens actuator too the target track is moving, and when the light beam spot is a Position reached that a predetermined number of tracks is placed in front of the target track, the lens actuator based on the measurement acceleration α deceleration control and the light beam point becomes the desire at the end control led to the target lane.

The other process steps are essentially the same as the construction of the device.

According to the optical disk device and the search control method of the invention, as mentioned above, the acceleration power of the lens actuator beforehand is measured, and the resulting acceleration is calculated for the Deceleration control at the time of retraction of Spurver Follow servo used. Even if the acceleration performance has a change that the device is inherent, can therefore provide the ideal deceleration control be executed so that the speed is set to 0 becomes when the light beam spot reaches the target track position enough. The retraction on the target track can safely out leads. Since no search error occurs, a search is made performance significantly improved.

The above and other tasks, features and advantages The present invention will be apparent from the following the description with reference to the drawings better forth.

Brief description of the drawings

Fig. 1 is a block diagram of an embodiment of the invention;

Fig. 2 is an exploded assembly diagram of a carriage and an optical head;

Fig. 3 is an exploded assembly diagram of the carriage and a movable section of the optical head;

Fig. 4 is an explanatory diagram of a fixed section of the optical head and an optical system;

Fig. 5 is a block diagram showing functions of the invention;

FIGS. 6A to 6E are timing charts for an acceleration measurement according to the invention;

FIGS. 7A to 7E are timing charts for a Ver langsamungssteuerung according to the invention;

Fig. 8 is a timing chart showing coarse control, fine control, and deceleration control in a search control of the invention;

Fig. 9 is a timing chart showing a deceleration state in a changeover section from fine control to deceleration control of the invention;

Fig. 10 is a flowchart for an acceleration measurement process of the invention;

Fig. 11 is a flow chart for search control of the invention;

Figs. 12A to 12C are timing charts for a Medienexzentrizität and acceleration measurements;

Fig. 13 is a flowchart for a measurement timing setting process; and

Fig. 14 is a flowchart for an acceleration measurement of the invention, which is carried out when a search error occurs.

Detailed description of the preferred embodiment

In Fig. 1, an optical disc 10 is a medium on which / from which information can be optically written and read. The optical disc 10 is enclosed by a cassette (not shown). When the cassette of the optical disc 10 is inserted into a device, it is loaded onto an axis of rotation of a spindle motor 12 by a loading mechanism as shown in the diagram. The spindle motor 12 rotates the optical disk 10 at a constant speed. A carriage 14 is arranged to be movable in the radial direction of the optical disk 10 . A movable section 18 of an optical head is mounted on the carriage 14 . The carriage 14 is driven by a Wagenan drive coil 16 in the radial direction of the optical plate 10 . More specifically, a voice coil motor is used. An objective lens 22 is provided for the movable section 18 of the optical head, which is mounted on the carriage 14 . The objective lens 22 converges a laser beam, which is irradiated through a fixed section 20 of the optical head, onto a media surface of the optical disk 10 , whereby a beam spot is formed. The objective lens 22 is driven by a lens actuator 25 having a tracking actuator drive coil 24 , and moves the beam spot in the radial direction of the optical disk 10 . The lens actuator 25 is also referred to as a tracking actuator. A range of motion of the beam spot through the objective lens 22 is set at a lens center 23 to a range on one side of, for example, 32 tracks. The objective lens 22 is moved in the direction of an optical axis by a focus actuator drive coil 26 and performs focus control to form a specified beam spot on the media surface of the optical disk 10 . A lens position sensor 28 is also provided for the movable section 18 of the optical head. The Linsenposi tion sensor 28 detects the position of the objective lens 22nd Namely, when the objective lens 22 is disposed at the lens center position 23 , a lens position signal E4 obtained from a control amplifier 46 is set to 0V. For example, when the objective lens 22 moves toward the inner side, a signal voltage with plus polarity and according to a moving amount is derived. When the objective lens 22 moves to the outer side, a signal voltage with opposite minus polarity is obtained and obtained according to an amount of movement. The position of the carriage 14 is detected by a carriage position sensor 32 . A carriage position signal E2 of the carriage position sensor 32 , which is output from a control amplifier 35 , is set to 0 when the carriage 14 is arranged at the innermost position. The carriage position signal E2 is set to a signal voltage which is proportionally increased in accordance with the movement of the carriage 14 toward the outer side.

A laser photo sensing section 30 for receiving a return light of the beam spot formed on the optical disk 10 by the objective lens 22 is provided for the fixed section 20 of the optical head. A light reception signal from the laser photo sensing section 30 is supplied to a control amplifier 54 . A focus error signal E5 and a tracking error signal E6 are output from the control amplifier 54 . A laser light source for emitting a light beam to the movable section 18 of the optical head is provided for the fixed section 20 of the optical head. The details of the fixed section 20 of the optical head are clearly explained below. A DSP (digital signal processor) 40 is provided to perform servo control of the carriage 14 , the lens actuator drive coil 24, and the focus actuator drive coil 26 . The DSP 40 has an A / D converter and a D / A converter in it, and for example, an MB86311 from Fujitsu Ltd. be used. Each circuit function of a carriage servo section 50 , a focus servo section 58 , a tracking servo section 64 and a search control section 72 is realized by a processor circuit section 42 of the DSP 40 . An MPU (microprocessor unit) 120 is also provided, which reports a search command to the DSP 40 based on a command from an external disk control unit. The MPU 120 also instructs to start an acceleration measurement of the invention.

The carriage servo section 50 performs position locking control and double servo control using the carriage 14 . For those controls, the carriage position signal E2 is output based on the detection signal of the carriage position sensor 32 from the control amplifier 35 and supplied to the carriage servo section 50 through an A / D converter 38 . By differentiating the carriage position signal E2 from the control amplifier 35 by a differentiating circuit 34 , a carriage speed signal E3 is formed and fed to the carriage servo section 50 via an A / D converter 36 .

The search control by the search control section 72 is mainly divided into a rough control to mainly move the carriage 14 , a fine control to mainly move the lens actuator 25 , and a deceleration control to zero the speed on a target track.

The coarse and fine controls are feedback controls so that a TES zero-cross signal E7 output from a comparator 68 is counted by a counter 71 for a predetermined time, the speed is compared with a target speed by a search control section 72 , and Current instruction data E10 is output to a D / A converter 52 to set a deviation between those speeds to zero. In the rough control, the carriage 14 is speed controlled and the lens actuator 25 is controlled to always set the position signal E4 from the lens position sensor 28 to zero. Such an operation is called lens locking. More specifically, a lens lock ON signal E16 is output from the search control section 72 to the tracking servo section 64 . The fine control is carried out when the number of tracks up to the target cylinder is equal to or less than 32 tracks on each of the inner side and the outer side. At this time, the carriage servo section 50 performs position servo control. Consequently, the carriage servo section 50 performs the position control for the movement of the lens actuator 25 so that the carriage 14 can be tracked to always set the position signal E4 from the lens position sensor 28 to zero. Such an operation is called a double servo.

The tracking servo section 64 performs on-track control and search current output by driving the lens actuator drive coil 24 .

The tracking error signal E6 based on the light reception output of the laser photo sensing section 30 is supplied from the control amplifier 54 through an A / D converter 62 to the tracking servo section 64 . The tracking error signal E6 is supplied to the comparator 68 , from which the TES zero crossing signal E7, which indicates a zero crossing timing of the tracking error signal, is output. The zero crossing signal E7 is given to the counter 71 . A zero crossing signal E7 is obtained every time the head passes a track. Therefore, the number of lanes in search control can be recognized by the search control section 72 .

A generation period of the zero crossing signal E7,
that is output from the comparator 68 is measured by a timer 70 , so that the pass control time from a track can be recognized by the search control section 72 . When the 1-lane passing time is obtained from the timer 70 , the search control section 72 can recognize a moving speed of the beam spot at that time, namely a moving speed of the beam spot through the objective lens 22 which is driven by the lens actuator driving coil 24 . Further, a search command to instruct a destination track address (destination address) is reported to the search control section 72 by a higher-order device. The search control section 72 that received the search command obtains the number of remaining tracks up to the target track address for the current track address recognized based on the zero crossing signal E7. If the number of remaining tracks is equal to or less than 32, fine control based mainly on the lens actuator is carried out. If it is larger than 32, the rough control based mainly on the carriage is executed.

Simultaneously with the instruction of a track jump power output, the search control section 72 stops outputting a track servo ON signal E8 and turns off-track control by the tracking servo section 64 . For a period during which the track servo ON signal E8 is received by the search control section 72 , the tracking servo section 64 outputs an instruction data signal E12 to a D / A converter 66 to receive the tracking error signal E6 from the A / D converter 62 always set to 0, and performs the on-track control by driving the lens actuator 25 through the lens actuator drive coil 24 . Since the tracking servo ON signal E8 is stopped while searching, the on-track control is suppressed. At the same time, a search operation is performed based on the instruction of the track jump current output that is generated. In a similar manner as in the case mainly based on the carriage, the search control mainly based on the lens actuator is also constituted by a rough control including the acceleration control, constant speed control and deceleration control, and by a fine control. In the invention, the search control section 72 functions as an acceleration measuring section for measuring an acceleration of the lens actuator 25 by the lens actuator drive coil 24 provided for the movable section 18 of the optical head.

Fig. 2 shows a specific example of the carriage 14 , the movable section 18 of the optical head and the fixed section 20 of the optical head of the invention. The fixed section 20 of the optical head is attached to a frame of the device (not shown). The carriage 14 , which is movable along guide rails 75-1 and 75-2 , is provided in front of the fixed section 20 of the optical head. Box-shaped carriage drive coils 16-1 and 16-2 , which are open on the front and rear sides, are provided on both sides of the carriage 14 . The carriage drive coils 16-1 and 16-2 are arranged around a pair of magnet units 74-1 and 74-2 which are fixed to the frame of the device. A voice coil motor (VCM) is formed by the carriage drive coils 16-1 and 16-2 and magnet units 74-1 and 74-2 . The movable section 18 of the optical head having the objective lens 22 is mounted on the carriage 14 . The movable section 18 of the optical head 18 has a beam input / emission opening 77 and lets in and emits a laser beam from the fixed section 20 of the optical head. The movable section 18 of the optical head, which is mounted on the carriage 14 , moves the beam spot in the radial direction of the media surface on the lower side of the optical disk 10 , which shows the objective lens 22 through a cut away part.

FIG. 3 is an exploded assembly diagram of the carriage 14 and the movable section 18 of the optical head in FIG. 2. A shaft 80 is formed in a central section of the carriage 14 cut at right angles. The lens actuator 25 is attached to the shaft 80 through a shaft hole. The lens actuator 25 rotates around the shaft 80 and slides in the axial direction at the same time. The objective lens 22 is provided for the lens actuator 25 . The lens actuator drive coils 24 are attached to both sides of a rotating portion of the lens actuator 25 . In a state where the lens actuator 25 is disposed on the shaft 80 , a pair of magnets 76-1 and 76-2 are disposed on the outside of the lens actuator drive coils 24 . Therefore, when a current is supplied to the lens actuator drive coils 24, the lens actuator 25 rotates clockwise or counterclockwise by a magnetic repulsion function between the magnets 76-1 and 76-2 on both sides. The focus actuator drive coil 26 is provided on the lower side of the lens actuator drive coils 24 provided for the lens actuator 25 . In a state where the lens actuator 25 is disposed on the shaft 80 , permanent magnets 78-1 and 78-2 are disposed on both sides of the focus actuator drive coil 26 . Therefore, when a current is supplied to the focus actuator drive coil 26 , the lens actuator 25 can be vertically driven according to the current direction by magnetic attraction and repulsion between the magnets 78-1 and 78-2 on both sides. By attaching a cover 82 after the lens actuator 25 is mounted on the shaft 80 of the carriage 14 , the movable section 18 of the optical head, which is integrated with the carriage 14 , is assembled.

Fig. 4 shows an optical system which is built in the fixed section 20 of the optical head in Fig. 2. In this optical system there are two optical systems of a walking path and a return path. First, the optical system of the walking path is explained. A laser beam emitted and dispersed by a laser diode 200 is converted into a parallel beam by a collimator lens 202 . The parallel beam transmitted through the collimator lens 202 passes through a beam splitter 204 and enters the objective lens 22 . The laser beam that enters the objective lens 22 is converged, and a beam spot with a diameter of about 0.8 microns is formed on the disc medium 10 . As is well known, the plate medium 10 is formed by applying an MO layer 10-2 to a substrate 10-1 , and a magnetization reversal dimple 15 is formed by a groove 10-3 in the circumferential direction. The return path optical system will now be described. The laser beam reflected from the disk medium 10 moves along the same path of the objective lens 22 and the beam splitter 204 as that of the walking path in the opposite direction and is reflected by the beam splitter 204 and enters a beam splitter 206 . The beam splitter 206 divides the incident laser beam into transmitted light for a detection lens 208 and reflection light for a Wollaston unit 210 . The reflected light that entered the Wollaston unit 210 is further divided according to a deflection component and enters a two-part photo detector 212 . The two-part photo detector 212 has photo sensing sections 212-1 and 212-2 . Light receiving signals M1 and M2 of the photo sensing sections 212-1 and 212-2 are input to operational amplifiers 222 and 224 , of which an MO signal and an ID signal are output. That is, MO = ID = M2 - M1. The transmitted light from the beam splitter 206 for the detection lens 208 is split by a Foucault unit 214 and enters a 2-split photo detector 216 and a 4-split photo detector 218 . The split photodetector 216 has photo- sensing sections 216-1 and 216-2 and outputs light reception signals T1 and T2. The light receiving signals T1 and T2 of the photo sensing sections 216-1 and 216-2 are input to an operational amplifier 226 , from which a TES signal (TES = T1-T2) is output. In the Foucault unit 214 , the transmitted light is further divided by a cross prism 220 and enters the 4-divided photodetector 218 . Of the 4-divided photodetector 218 photo-sensing sections 218-1, 218- 2, 218-3 and 218-4, and generates light reception signals P1 to P4. The light receiving signals P1 to P4 of the photo sensing sections 218-1 to 218-4 are additionally input to an operational amplifier 228 , from which an FES signal is output. That is

FES = (P1 + P3) - (P2 + P4).

FIG. 5 shows a functional block of the DSP 40 in FIG. 1, and it is constructed from the tracking servo section 64 , the search control section 72, and a carriage servo section 75 . A target speed operation section 84 , a speed operation section 86 , an adder 88 , a current value converting section 90 and a remaining track operation section 101 are provided for the search control section 72 . The speed operation section 86 receives from the counter 71 the number of tracks that the optical head has passed within a predetermined time, or receives a 1-track passing time from the timer 70 and outputs a signal of the current speed. The target speed operation section 84 obtains the number of remaining tracks up to the target track from the number of tracks counted by the counter 71 , and reads a target speed signal corresponding to the number of remaining tracks from a table 85 previously has been formed and outputs this. The adder 88 forms a deviation signal between the current speed signal output from the speed operation section 86 and the target speed signal output from the target speed operation section 84 .

An output of the current value conversion section 90 is input to a selector 91 . On the basis of a coarse / fine switching signal E15 from the remaining-track operating section 101 , the output of the conversion section 90 of the carriage servo section 75 is supplied in the case of the coarse control. When the control is switched to fine control, the remaining track operation section 101 switches to the output from the tracking servo section 64 . For example, if the number of remaining tracks exceeds 32 tracks, the rough switching is made effective. If it is equal to or less than 32 tracks, fine switching is made effective. Further, in the case of rough control, the lens lock ON signal E16 is supplied to a lens lock control section 97 of the tracking servo section 64 . The lens lock ON signal E16 is reset when the control is switched to fine control.

The carriage servo section 75 has a double servo section 177 and a selector 79 . In the rough control, the selector 79 selects an output from the search control section 72 and allows a current to flow to the carriage drive coil 16 . When the control is switched to fine control, the remaining servo number operation section 101 generates a double servo ON signal E17 so that the double servo section 177 is made operative, and the selector 79 selects an output of the double servo section 177 . The double servo section 177 supplies the current of the car driving coil 16 too, so that the lens position of the Spurver is set folgungsbetätigers 25 by the lens position sensor 28 to zero. An on-track control section 98 , a selector 96, and the lens lock control section 97 are provided for the tracking servo section 64 . The on-track control section 98 is controlled on / off by the tracking control section 72 by the tracking servo ON signal E8. In the rough control, the selector 96 selects an output of the lens lock control section 97 . In fine control, the selector 96 selects the output of the search control section 72 . Further, the selector 96 selects an output of the on-track control section 98 after the search operation is completed.

In addition to the functions of the search control and on-track control in the tracking servo section 64 , the search control section 72 and the car servo section 75 , as mentioned above, an acceleration measuring section 100 is newly provided in the invention. The acceleration measurement section 100 operates when a measurement start signal is received from the MPU 120 in FIG. 1. The Beschleunigungsmeßsektion 100, the target speed operation section 84 an input track seek and receive on the basis of the tracking error signal E6, obtained from the laser photo sensing section 30, a movement velocity by the driving of the lens actuator by the lens actuator drive coil 24 at the time, whereby from the movement speed an acceleration α is obtained which is inherent in the lens actuator.

A measurement of the acceleration α of the lens actuator by the acceleration measurement section 100 will now be described with reference to FIGS. 6A to 6E. It is now assumed that the acceleration measurement was started at time t1 in FIGS. 6A to 6E. Before time t1, as shown in Fig. 6D, the tracking servo ON signal E8 is in the ON state, and on-track control for tracking the current track by the beam spot is carried out. When the acceleration measurement is started at time t1, the tracking servo ON signal E8 in Fig. 6D is turned off and the on-track control is suppressed. At the same time, as shown by a lens actuator drive coil current in FIG. 6B, a predetermined acceleration current is supplied for a predetermined acceleration time Tx. As shown in FIG. 6E, the acceleration time Tx is a time required for a moving speed (V) of the lens actuator to reach a specified target speed V0. When the speed of the lens actuator reaches the target speed (V) at time t2, the control mode is switched to the constant speed mode. In a state of constant speed control from time t2, the optical head waits until it is moved to a track position 0.5 according to the tracking error signal E6 in Fig. 6A. When the head moves to the track position 0.5, the tracking error signal in Fig. 6A is set to 0 at time t3. A time period from the acceleration end time t2 to the arrival time t3 at the track position 0.5 is measured as the waiting time Ty. The acceleration α of the lens actuator is obtained from the acceleration time Tx and the waiting time Ty as follows. First, it is now assumed that the acceleration time is Tx, the time it takes for the head to be moved to the half-track position after the end of acceleration is Ty, a speed at that time is (V) , and a track pitch is equal to (C). In this case, since an area of a hatched portion obtained by integrating a speed change in a time interval from t1 to t3 in FIG. 6E indicates a moving distance over half the track, the following equation is satisfied.

From the equation (1) the speed (V) on End of acceleration at time t2 by the following Get equation.

Since the acceleration α is a gradient one Speed change in a time interval of t1 denoted by t2, it is represented by the following equation calculated.

In equation (3), the acceleration α can be calculated by inserting the measured values of the acceleration time Tx and waiting time Ty in FIGS. 6A to 6E and the well-known track spacing (C).

On the other hand, in Figs. 6A to 6E, after the head is moved to the track position 0.5 at the time t2, the head waits the same time as the waiting time Ty for t2 to t3 because the acceleration α by the 1-track search is measured. A current of the same magnitude as that of acceleration and a polarity opposite to that is supplied to the lens actuator driving coil for the same deceleration time Tx as the acceleration time Tx at time t4, thereby executing the deceleration control. When the 1-track search is completed at time t5, the tracking servo ON signal E8 in FIG. 6D is turned on again, thereby returning the control mode to the on-track control. The acceleration of the lens actuator that has been measured as explained above is stored and held in the acceleration measuring section 100 , and the deceleration is carried out.

Timing charts of FIGS. 7A to 7E relate to the deceleration control using the Meßbeschleuni supply α of the lens actuator, the measuring section by the acceleration was measured 100th As shown in FIG. 9, the deceleration control corresponds to the portion obtained by enlarging the portion of a deceleration control 150 that is executed after fine control 140 following coarse control 130 . Fig. 8 shows the changeover section from the fine control 140 to the deceleration control provided that the speed is constant for the sake of simplicity of explanation. However, there is also a case, as shown in FIG. 9, in which the control is changed over while decelerating due to an inertial force.

First, like a tracking error signal E6 in Fig. 7A, the passing time (T) from one track at time t1 is measured when the number of remaining tracks for the target track is equal to the value corresponding to the position 2.5 cylinders ahead the target track is. As shown at time t1-t2 in FIG. 7E, since an area obtained by integrating the constant speed (V) by the 1-lane passing time (T), with the 1-lane distance (C) coincides, the moving speed (V) at that time obtained by the following equation.

V = C / T [m / s] (4)

A braking time TB that is required to Speed by arriving at the target track position, at which the number of remaining tracks at time t4 is 0, set to 0, can be obtained by

β = V / α [s] (5)

based on the acceleration α previously measured in the timing chart of FIG. 6.

If the braking time TB for the ideal slowdown obtained, as mentioned above, will start from the measurement end point of the 1-lane passing time from the time t2 to the Start time t3 of deceleration at time t3 a waiting time TW received.

Since the area of the hatched portion of the lens actuator speed in Fig. 7E coincides with the moving distance 1.5C at time t2-t4, the following relationship is satisfied.

By summarizing equation (6) with respect to Waiting time TW, the following equation is obtained.

As is evident from equation (7), if the measurement time (T) of the 1-lane passage of the time t1-t2 and the braking time TB are obtained from the equations (4) and (5), the waiting time can be obtained by inserting them TW can be obtained. Equation (7) is obtained just after the time t2 at which the measuring time T of the 1-lane passing time is obtained. When the time from the timer start reaches the calculated waiting time TW from the time t2, the deceleration control is started at the time t3. At a time when the deceleration control is performed for the calculated braking time TB, by returning the tracking servo ON signal E9 in FIG. 7 (D) to the ON state, the servo retraction to the ideal target track is realized.

A flowchart of FIG. 10 relates to an acceleration measurement process of the lens actuator by the acceleration measurement section 100 in FIG. 5. The embodiment is characterized in that the acceleration measurement is performed many times in a state that the movable section 18 of the optical head is one searched for a predetermined inner track of the optical disk 10 , for example, an innermost track, the acceleration measurement is then performed many times in a state in which the movable section 18 of the optical head searched for a predetermined outer track of the disk medium, for example, an outermost track, and finally an average of all acceleration measurements is obtained as a final result.

In FIG. 10, the movable section 18 of the optical head first searches for a predetermined inner track of the optical disk 10 at step S1. When the completion of the search is judged at step S2, the tracking servo is turned on and the tracking control is executed at step S3. At step S4, the acceleration measurement is started, tracking servo is turned off, and an acceleration current (I) is turned on. At step S5, a check is made to see whether or not the specified acceleration time Tx has passed. When the acceleration time Tx elapses, step S6 follows, and the acceleration current (I) is turned off, and the waiting process is carried out. At step S7, a check is made to see whether or not the head has been moved to the track position 0.5 during the constant speed control. If YES, step S8 follows, and a value of a timer (T) at that time is set to the waiting time Ty. At step S9, a check is made to see whether or not the same time as the waiting time Ty has passed. If YES, a deceleration current -I is turned on and the deceleration is started at step S10. At step S11, a check is made to see whether or not the time Tx has elapsed during the deceleration. If YES, step S12 follows, and the deceleration current -I is turned off, and at the same time, by turning on the tracking servo, the control mode is switched to the on-track control, and the 1-track search for the acceleration measurement is ended. At step S13, a check is made to see whether or not the number of measurements has reached a specified number. If NO, a count value of a counter (N) is incremented by "1" in step S14. The acceleration measurement from step S4 is repeated again.

When measuring acceleration in the inner track  switched the direction of the 1-track search for each measurement, and the acceleration α is measured until by the Switch the 1-track search between the two neighboring ones inner tracks the number of measurements the specified Number reached. If the specified one at step S13 Number of measurement times obtained with respect to the inner track step S15 follows. A check is made to to see if the measurement regarding the outer track ends has been or not. If NO, the head visits Step S16 a predetermined outer track. If at step S2 the completion of the search is judged, the multiple current measurement in steps S13 to S14 for similar Repeated as in the inner track. If at step S13 judges that the number of measurements regarding the outer track has reached the specified number the processing routine from step S15 to step S17 about. The acceleration α is derived from equation (3) for each measurement using the plurality of measurement times Tx and Ty calculated by the measurement related to the inner track and the outer track were saved. If at step S17, the accelerations α with respect to all Measurements can finally be calculated at Step S18 calculates an average acceleration and stored as acceleration α, which for the deceleration a control is used.

FIG. 11 is a flowchart for the search control that includes the deceleration control by the search control section 72 using the measurement acceleration α measured by the acceleration measurement section 100 in FIG. 5. First, in step S1, a difference is set that has been reported by a higher-value device. If the difference exceeds 32 tracks, the tracking servo is turned off at step S2. The acceleration control is carried out at step S3. At step S4, the rough control is carried out. If the number of remaining tracks due to the rough control decreases to 32 tracks, the fine control is carried out in step S4. During the fine control, a check is made to see if the number of remaining tracks has reached 2.5 tracks or not. If YES, the timer (T) for measurement is started in step S6. At step S7, a check is made to see whether or not the number of remaining tracks has reached 1.5 tracks. If YES, the timer (T) is stopped at step S8 and the 1-lane passing time (T) is determined. At step S9, the measured value of the 1-lane passing time (T) is inserted into the equation (4), and the moving speed (V) is obtained. By inserting the movement speed (V) in the equation (5), the braking time TB is calculated. Furthermore, by inserting the braking time TB and the 1-lane passing time (T) into the equation (7), the waiting time TW is obtained. At step S10, a check is made to see whether or not the time of the timer (T) started when the number of remaining tracks reaches 1.5 tracks coincides with the waiting time TW. If YES, the deceleration current -I is turned on and the deceleration is started at step S11. At step S12, a check is made to see whether or not the value of the timer (T) started by the start of the deceleration coincides with the braking time TB. If YES, step S13 follows, and the deceleration current -I is turned off, and at the same time, tracking servo is turned on and on-track control is performed, whereby servo feeding is performed on the target track. Search control is complete.

An optimal timing of the acceleration measurement with a track eccentricity of the optical disk 10 will now be described. As shown in Fig. 1, in the optical disk 10 which is attached to the spindle motor 12 and rotated, a track position in the disk rotation due to a curvature of the optical disk 10 , a deviation from the motor rotation axis or the like is made eccentric . With such a track eccentricity, the tracking servo section 64 controls the lens actuator 25 by on-track control so that movement of the beam spot through the objective lens 22 , which tracks the track eccentricity, is obtained. Such movement of the objective lens 22 , which tracks the eccentricity in the on-track control, is detected by the lens position sensor 28 . A change in the lens position signal from a rotation is obtained, for example, shown in Fig. 12A. In the acceleration measurement section 100 in Fig. 5, since the acceleration is obtained from the measurement result by the 1-track search of the lens actuator 25 , it is desirable to start the acceleration measurement at an eccentric position where the movement of the lens actuator 25 due to the track eccentricity while the on-track control is small. When looking at a lens position signal in FIG. 12A, a direction of movement of the lens actuator is switched from moving inward at point 114 to moving outward. At this position, the speed of movement in the radial direction is 0. Similarly, at point 116, the direction of movement of the lens actuator has been switched from the outer direction to the inner direction. Similarly, the speed of movement in the radial direction is 0. Therefore, when controlling the lens actuator that was tracking the track eccentricity, it is desirable to start the acceleration measurement at points 114 and 116 when there is no movement in the radial direction of the lens actuator. Regarding such timings of points 114 and 116, it is sufficient to detect a zero-cross timing of a lens speed signal obtained by differentiating the lens position signal as shown in Fig. 12B and to output a measurement start signal shown in Fig. 12C. The process for the 1-track search to measure the acceleration of the lens actuator shown in the timing chart of Fig. 6 takes only a short time of about a few hundred microseconds. The acceleration measurement can be repeated at any time when the lens speed signal is 0.

A flowchart of FIG. 13 relates to a speed measurement timing setting process of FIGS . 12A to 12C. First, at step S1, the lens position signal from the lens position sensor 28 is differentiated, and a speed VL is calculated. At step S2, a check is made to see whether or not the lens movement speed VL has reached 0. If YES, a measurement process is started in step S3. When the completion of the measurement is judged at step S4, the processing routine returns to step S1 and the next measurement timing is set.

A time at the optical disk device of the present invention to perform the acceleration measurement of the lens actuator by the acceleration measurement section 100 in FIG. 5 will now be described. First, as shown in Fig. 1, in the optical disc device of the invention, the optical disc 10 enclosed by the cassette is inserted and used in the device. At a time when loading is completed so that the optical disk 10 , which is closed by the cassette, is inserted into the optical disk device and attached to the spindle motor 12 , the measurement start signal E14 from the search control section 72 of the acceleration measurement section 100 the tracking servosec tion 64 is supplied, whereby the measurement process according to the flow diagram of FIG. 8 is carried out.

In an ordinary use state, after the optical disc cartridge is loaded when the DSP 40 in FIG. 1 is in a waiting state of an instruction, the measurement start signal E14 is supplied from the search control section 72 to the acceleration measurement section 100 , whereby the measurement process is carried out. In the measurement process in such a command waiting state, if a command is received from a higher quality device during the measurement process, the measurement process is interrupted and the received command is preferably processed. Furthermore, the usage time of the device is counted, and the acceleration measurement can also be performed every time a count value reaches a predetermined usage time. In the acceleration measurement in such a case, it is also desirable to start the measurement process when the device is in the waiting state from a command from the higher-order device, in a state in which the usage time of the device reaches a predetermined time.

Further, in the optical disk device of the invention, as shown in a flowchart of Fig. 14, when a search error occurs due to the execution of the search command from the higher-value device, the measurement process of accelerating the lens actuator is carried out and a retry search can be performed using a newly measured acceleration can also be carried out. In Fig. 14, when the search command is first received at step S1, a search process is carried out at step S2. If the search error occurs in step S3 regarding such a search process, step S4 follows, and the measurement process of accelerating the lens actuator according to the flowchart of FIG. 8 is carried out. When the measurement process is finished, a retry search process is carried out using the acceleration α obtained by the measurement. If the search error occurred due to the deceleration control by the incorrect acceleration α, the search error is eliminated by the deceleration control in the search control using the newly measured correct acceleration. The processing routine can be ended normally from step S6.

As described above, according to the present Invention by measuring the acceleration line beforehand equipment of the lens operator and using the received acceleration for the deceleration control to the Tracking servo retraction time, even if the Accelerating performance of the lens actuator changes tion that is specific to the device, the ideal Deceleration control so that the Speed on arrival at the target track position is 0. The servo retraction to the target track can be done safely be carried out. Since no search error occurs, the stable search operation are guaranteed, so the search line can be improved. Although the above execution shape with regard to the acceleration measurement process and the Search control shown and described using the DSP MPU or hardware can also be used circuit for exclusive use.

In the deceleration control of Fig. 7A to 7E of the measuring process has started, when the number of ver remaining tracks reaches 2.5 tracks. However, it is sufficient if the position of the remaining number of tracks at which the measurement is started is correctly determined in accordance with the number of remaining tracks necessary for the braking time TB which is determined by the acceleration performance of the lens actuator. For example, if the acceleration performance is good and the braking time TB is equal to or less than 0.5 tracks, it is sufficient to obtain the measurement time (T) and the waiting time TW by setting the number of remaining tracks to 1.5 tracks . Further, when the acceleration performance is lower than that in the timing chart of Fig. 7, the number of remaining tracks to start the measurement is set to a larger value.

Although in the above embodiment the average value has been obtained by the acceleration measurement many times regarding the inner track and the outer track has been carried out, it is also possible, the acceleration incline at a suitable track many times Measure position and get the average. Furthermore, the invention is not by the in the execution limited numerical values shown in the form.

Claims (28)

1. An optical disk device with:
an optical head for forming a light beam spot on a media surface of a disk medium through an objective lens, whereby information is optically read or written;
a carriage on which said optical head is mounted and which is moved in the radial direction of the disk;
a lens actuator for driving said objective lens of said optical head on said carriage, thereby moving said light beam spot in the radial plate direction;
an acceleration measuring section for obtaining acceleration inherent in said lens actuator based on a moving speed when said lens actuator is accelerated; and
a search control section for moving the light beam spot of said optical head toward a target track by a predetermined speed control and constant speed control of said lens actuator, for decelerating control of said lens actuator based on said measurement acceleration when said light beam spot reaches a position which is a predetermined number of tracks is arranged in front of the named target track. 2. A device according to claim 1, wherein the called acceleration measurement section from a track jump leads to moving the light beam point of the above optical head on an adjacent track, causing the Acceleration is obtained using the lenses mentioned actuator is own.   3. A device according to claim 1, wherein the mentioned track jump in the said accelerometer tion after the on-track control of said lenses was suppressed, the acceleration only for a predetermined time (Tx) is executed, a control mode switched to constant speed control a waiting time (Ty) is measured until the light beam point from the end of the mentioned acceleration Track position 0.5 reached, and further after waiting for it ben time as the specified waiting time (Ty) from track position 0.5 the slowdown for the same time as that Acceleration time (Tx) is executed and the control mode is switched to on-track control. 4. An apparatus according to claim 3, wherein in the case where a track pitch is (C) and the acceleration time is Tx, said acceleration measuring section calculates an acceleration α which is inherent in said lens on the basis of the measurement waiting time Ty. 5. An apparatus according to claim 1, wherein the called acceleration measurement section the acceleration measurement many times and the named own Acceleration from an average of results of named measurement. 6. An apparatus according to claim 1, wherein the called acceleration measurement section the acceleration measurement many times on a predetermined track on a executes the inner side of the mentioned disk medium and the  Acceleration measurement also many times on a predetermined th track on an outer side, causing the own acceleration from an average of results the measurement mentioned is obtained from the many times. 7. A device according to claim 1, wherein the called acceleration measurement section the acceleration measurement of the named lens actuator at a reset position of a track eccentricity in the radial direction of the mentioned disk medium executes. An apparatus according to claim 7, further comprising a lens position sensor for detecting a position of said objective lens which is more actuated by said lens,
and in a state where the light beam point of said optical head is allowed to track the track excentricity in the radial direction of said disk medium by on-track control of said lens actuator, said accelerometer section monitors a lens position signal from said lens position sensor and performs the acceleration measurement of said lens actuator at a position where an increase / decrease direction of said lens position signal changes. 9. A device according to claim 8, wherein the called accelerometer section the lens position signal differentiates that from said lens position sensor in a state of on-track control of the above Lens actuator is output, in which the light beam of the mentioned optical head the track eccentricity in Follow the radial direction of the disk medium mentioned allowed, and the acceleration measurement of the lens mentioned  operator at a position where there is a difference tion signal is 0. 10. An apparatus according to claim 1, wherein the called acceleration measurement section the acceleration measurement of the lens actuator mentioned, if that mentioned plate medium is inserted into the device. 11. An apparatus according to claim 1, wherein the called acceleration measurement section the acceleration measurement of said lens actuator in one command waiting state from a higher-quality device. 12. An apparatus according to claim 1, wherein the called acceleration measurement section the acceleration measurement of the lens actuator mentioned, if a Search error occurs, and the acceleration mentioned above lized that for the deceleration control of a next Search retry operation is used. 13. An apparatus according to claim 1, wherein the called search control section when the light beam spot reaches a position that is a predetermined number of Tracks are arranged in front of a target track, which is marked by a Acceleration performance of the lens actuator mentioned is determined, a lane passing time (T) measures a movement speed (V) receives a slowdown time TB to get to the target track by moving said speed (V) and the stated measurement acceleration a are used, finally by the measurement time and the said slowdown time TB a waiting time TW a point in time when said track measurement has ended, until the start of the slowdown, and the so called th lens actuator for the said slowdown time TB  from the end of the waiting period TW slow down controls. 14. A device according to claim 13, wherein under the assumption that a lane passing time is equal to (T) and the Slowdown time is equal to TB, the search tax mentioned tion section the waiting time TW calculated by TW = (3T - TB) / 2. 15. A search control method of a disk device, with:
an acceleration measurement step of obtaining an acceleration inherent in a lens actuator based on a moving speed when the lens actuator is accelerated to drive an objective lens of an optical head mounted on a carriage moving in the radial direction of a disk medium, whereby a light beam spot is moved on a surface of the disk medium in the radial disk direction; and
a search step for moving the light beam spot of said optical head to a target track by a predetermined speed control and a constant speed control of said lens actuator and, when said light beam spot reaches a position located a predetermined number of tracks ahead of the target track, for decelerating control of said lens actuator on the basis of said measurement acceleration, and for tracking said light beam spot onto the target track at an end time of said deceleration control. 16. A method according to claim 15, wherein the mentioned acceleration measurement step a track jump to Moving the light beam point of said optical  Head to an adjacent track and one Acceleration is obtained, the lens lens mentioned tiger is own. 17. A method according to claim 16, wherein the Track jump in said acceleration measurement step, after on-track control of said lens actuator gers was suppressed, the acceleration only for one predetermined time (Tx) is executed and a control mode switched to constant speed control a waiting time (Ty) is measured until the light beam point from the end of the mentioned acceleration Track position 0.5 reached, also after waiting for the same Time as the specified waiting time (Ty) from track position 0.5 the slowdown for the same predetermined time as that called acceleration time (Tx) is executed and the Control mode is switched to the on-track control. A method according to claim 17, wherein in said acceleration measuring step, in the case where a track pitch is (C) and the acceleration time is Tx, an acceleration α inherent in said lens actuator is calculated by on the basis of the measurement waiting time Ty. 19. A method according to claim 15, wherein the called acceleration measurement step, the acceleration measurement is carried out many times and the named own Acceleration from an average of results of mentioned measurement is obtained.   20. A method according to claim 15, wherein the called acceleration measurement step, the acceleration measurement many times on a predetermined track on a inner side of said disk medium is executed, the acceleration measurement is also done many times on one certain track is running on an outer side, and the named own acceleration from an average the results of the above measurement from many times is obtained. 21. A method according to claim 15, wherein the called acceleration measurement step, the acceleration measurement of the named lens actuator at a reset position of a track eccentricity in the radial direction of the mentioned disk medium is executed. 22. A method according to claim 21, wherein the said acceleration measurement step, in a state at which the light beam point of said optical head Track eccentricity in the radial direction of the mentioned plat tenmediums by an on-track control of the above Lens operator may track a lens position signal the objective lens mentioned, which by a lens posi tion sensor is detected, monitored and the Accelerometer measurement of the lens actuator mentioned a position is executed where an increase / decrease direction of said lens position signal changed becomes. 23. A method according to claim 22, wherein the said acceleration measurement step, in a state at which the light beam from said optical head Track eccentricity in the radial direction of the mentioned plat tenmediums by the on-track control of the above  Lens operator may track the lens position signal, which is detected by said lens position sensor is differentiated and the acceleration measurement of the mentioned lens actuator performed at one position becomes where a differentiation signal is set to 0. 24. A method according to claim 15, wherein the Accelerometer measurement of the lens actuator mentioned said acceleration measuring step is carried out, when said disk medium is inserted into the device sets is. 25. A method according to claim 15, wherein the Accelerometer measurement of the lens actuator mentioned said acceleration measurement step in one command Waiting state carried out by a higher quality device becomes. 26. A method according to claim 15, wherein the Accelerometer measurement of the lens actuator mentioned said acceleration measuring step is carried out, if a search error occurs, and the mentioned acceleration supply for the deceleration control of a next one Search retry operation is updated becomes. 27. A method according to claim 15, wherein the called search control step when the light beam spot reaches a position that is a predetermined number of Tracks are arranged in front of a target track, which is marked by a Acceleration performance of the lens actuator mentioned is determined, a lane passing time (T) is measured, a Movement speed (V) is obtained, then get a slowdown time TB to the target track  is by the said movement speed (V) and the measurement acceleration α are used, close Lich by the measurement time (T) and the Ver slowdown time TB a waiting time TW from a time of End of the track measurement mentioned until a start of the Slowdown is obtained, and said lens actuation ger for the mentioned slowdown time TB from the expiration of the called waiting time TW is controlled by deceleration. 28. A method according to claim 27, wherein the mentioned search control step in the case when a 1- Lane passing time is equal to (T) and the deceleration time is equal to TB, the specified waiting time TW is calculated by TW = (3T - TB) / 2.