CN100454402C

CN100454402C - Optical disk unit

Info

Publication number: CN100454402C
Application number: CNB2006100898439A
Authority: CN
Inventors: 石桥广通; 渡边克也; 藤亩健司; 山田真一; 久世雄一
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2001-02-22
Filing date: 2002-02-20
Publication date: 2009-01-21
Anticipated expiration: 2022-02-20
Also published as: CN1913013A

Abstract

An optical disc unit 2001, comprising: a reflective surface detection device 1010 for detecting a reflective surface; focus adjustment means (1202, 1003, 1009, 1008, 1003, 1012, 1005 and 1204) for performing focus adjustment to the reflection surface so that a distance between a focus of a light beam applied to the optical disc 2100 and the reflection surface is within a predetermined error limit; a shifting means 1007 for shifting the position of the focus in a direction perpendicular to the optical disc; and a control means 1006 for controlling the focus adjustment means and the shift means.

Description

Optical disc unit

Technical field

The present invention relates to a kind of optical disc unit, be used for high density in the information that writes down digital video information for example on the CD and be reproduced in the information that writes down on the CD, and more specifically, relate to a kind of optical disc unit, it can carry out accurate focus adjustment (focus control) to the information sides of a CD.

Background technology

Recently, CD has been caused as the removable media with high power capacity and has noticed and expected that having an optical disc unit more to be widely used as in the future is a video recorder.One of reason is that CD is the removable media of a high power capacity, and it allows executive logging/reproduction and needn't contact this media.In other words, focus on a laser beam and shine the information recording layer of a CD with its focus, and therefore executive logging and reproduction.Therefore, even be attached with dust or foul on the surface of dish, the read head bump that takes place can not appear for example sending out in magnetic recording.

Yet, such characteristic of CD is based on a main prerequisite: the focus adjustment, promptly stably carry out the control that the focus of a convergent beam and the distance between the information recording layer is remained on an extent of the error that allows, in case this focus is out of control, the actuator for objective lenses of a shaven head (actuator) moves out of control and may cause clashing into optical disc surface.Be right after after a CD drive activated especially, when carry out focusing on, promptly in laser beam foucing being displaced to the capture range that this focus adjusts and during the closed then focus adjustment loop, such out of focus frequently occurs.Like this, routinely, several different focus methods have been worked out.

For example, in a kind of method that Japanese patent application (publication number is 9-115147) is described, pre-determine with respect to the optical disc information recording layer, the initial laser beam focus is closely or far and according to this original state to determine this focusing processing.Near with respect to information recording layer when definite this focus, actuator for objective lenses is driven so that focus more is close to information recording layer and when focus entered the capture range of focusing, this operation was converted into the operation with closed ring that focus is adjusted.Alternatively, when definite this focus is far away with respect to information recording layer, this actuator is driven so that focus is farther in information recording layer, and this operation is transformed into operation with closed ring similarly then.

Yet this conventional method has problem: during less than the swing of CD, the collision rate between object lens and the optical disc surface increases in the operating distance (distance between object lens and the optical disc surface) of object lens.Particularly, no problem when attempting to realize focusing on.Yet if failed, out of control even the actuator for objective lenses operation does not have, under the situation of swing greater than operating distance of CD, CD also might collide object lens.

For current available CD player and DVD player, the NA of object lens (numerical aperture) maximum is about 0.45 to 0.6.Like this, can guarantee that operating distance is 0.5mm or bigger.Therefore, common contingent swing is 0.2mm, and such swing can sufficiently be absorbed.Yet if the limit of NA is enhanced with further increase recording capacity in the future, the operating distance of this setting of object lens becomes especially little.For example, if NA is 0.85, even the thickness of protective seam be reduced to 0.1mm (thickness of the protective seam in CD be 1.2mm and in DVD the thickness of protective seam be 0.6mm), operating distance is about 0.15mm.

The present invention proposes in view of the above-mentioned problems in the prior art.The object of the present invention is to provide a kind of optical disc unit that focus is adjusted of carrying out, it can reduce the frequency that object lens and optical disc surface bump significantly, even when making the enough operating distance that can not guarantee object lens owing to the raising of CD capacity.

As the optical disc unit of a routine, an optical disc unit is arranged, wherein for example a light beam of the light source of semiconductor laser generation is focused and is applied on the CD that rotates with predetermined number of revolutions and the signal that is recorded on the CD is reproduced certainly.This CD comprises many mark roads of spiralization.These mark roads form by having recessed and groove convex portion.One recording film of phase shift material or similar material is attached on the recording surface.For recorded information on this CD, the intensity of light beam is changed, carries out the focus adjustment according to this information so that the focus of light beam drops on the recording surface and carries out tracking Control so that focus drops on the mark road.Like this, the reflectance of recording film is changed.For the information of reproducing on the CD, reflection is received by a photodetector from the light of switch-board, similarly, carries out the focus adjustment so that the focus of light beam drops on the information sides and carries out tracking Control so that focus drops on the mark road.The output of photodetector is processed to reproduce this information.

Detect the focus error signal of the misalignment between the focus of the information sides of indication one CD and a light beam by an astigmatic method or similar approach.When focus drops on the information sides, this focus error signal vanishing.Usually, the detection limit of astigmatic method is about 10 μ m.Like this, for operation one focus Adjustment System, object lens are moved in advance so that the position of focus is moved in this detection limit.When the focus error signal friendship is more zero, carry out the focus adjustment.Yet when focus was passed through (pass) optical disc surface, focus error signal was also handed over more zero.Hand over execution focus adjustment when getting over (zero-cross) if occur zero on optical disc surface, this focus adjustment is performed so that focus is positioned on the optical disc surface.For anti-situation here, the reflectance of employing information sides is higher than the reflectance of optical disc surface.More specifically, when horizontal exceeding one predeterminated level that detects the total internal reflection amount, appear at zero of recording surface and hand over detected more.

Recently, advised a kind of CD-RW, it has two information sides on the one side of CD.Below, such CD is called as double-layer CD.In this double-layer CD, when from the information on next (further) information sides of object lens when reproduced, reproduce this information with the light beam of being crossed the information sides that is close to object lens by transmission.Like this, this double-layer CD is designed so that to be close to the information sides reflectance of object lens lower.

Therefore, the light quantity from each information sides that is received by photodetector diminishes.CD with an information sides is called as single-layer optical disc.

As mentioned above, in double-layer CD, at the horizontal step-down of the total internal reflection amount of each information sides.Like this, according to the total internal reflection amount, be difficult to resolved light panel surface and information sides.This means if when carry out focusing on, be difficult to guarantee to focus on information sides with the method that is similar to conventional method.

The present invention proposes in view of the above problems.The object of the present invention is to provide a kind of optical disc unit, it can guarantee to focus on information sides, even leave the total internal reflection amount of closing panel surface and leave message surface the total internal reflection amount between difference when very little (for example, using under the situation of double-layer CD).

Summary of the invention

The invention provides a kind of optical disc unit, be used to have one or more information recording layer and be formed on the CD of the protective seam on this information recording layer with one or more, this optical disc unit comprises: reflective surface detection means is used to detect a reflecting surface; Focus adjusting device is used to carry out the focus adjustment of this reflecting surface so that be applied to the focus of light beam of this CD and the distance between this reflecting surface in predetermined extent of the error; Shift unit is used for the position of edge perpendicular to the direction moving focal point of CD; And control device; be used to control this focus adjusting device and this shift unit; wherein this control device is controlled this shift unit so that the focus of light beam is shifted to protective seam is detected by this reflective surface detection means until the surface of this protective seam; this control device is controlled this focus adjusting device with when detecting this protective seam surperficial; carry out the focus adjustment on the surface of this protective seam; this control device is controlled this shift unit to remove the surface that the focus of the focus adjustment on the surface of this protective seam and orientation information recording layer displacement light beam is detected information recording layer until this reflective surface detection means; and this control device is when controlling this focus adjusting device and being detected with the surface when information recording layer; carry out the focus adjustment on the surface of this information recording layer, thereby realize above-mentioned purpose.

Can be provided with to the feedback gain of the focus adjustment on the surface of protective seam and to the feedback gain of the focus adjustment on the surface of information recording layer so that the product of the reflectance on the surface of the feedback gain of the focus adjustment on the surface of protective seam and protective seam is equaled the product of reflectance on the surface of feedback gain that the focus on the surface of information recording layer is adjusted and this information recording layer.

Can on the surface of protective seam, be pre-formed the information of the reflectance of indication information recording layer; when execution is adjusted the focus on the surface of protective seam; this control device can read this information from the surface of protective seam, and can be according to the feedback gain of this information setting to the focus adjustment on the surface of information recording layer.

The reflectance on the surface of protective seam can be 3% to 5%.

The invention provides a kind of optical disc unit, be used to have the CD of one or more information sides, wherein this information sides has many formation mark road thereon, this optical disc unit comprises: tracking error detecting device, be used to detect the light beam that is applied on the CD with the misalignment between one of its many corresponding mark roads, and the tracking error signal of this misalignment of output indication; The amplification detection device is used to detect the amplification of this tracking error signal; Focus adjusting device, be used to carry out the focus adjustment so that the focus of this light beam and the distance between the information sides in a predictive error limit; Shift unit is used for moving towards this CD the position of the focus of this light beam; And control device, be used to control this focus adjusting device and shift unit, wherein this control device is controlled this shift unit so that along the be shifted focus of this light beam and near this CD of the direction of crossing the mark road that forms on the information sides of this CD, the operation of focus adjusting device is stopped; And the magnification that this control device allows focus adjusting device only to detect tracking error signal at this amplification detection device becomes a predetermined value or begins this operation when higher, thereby realizes above-mentioned purpose.

Each many mark road that is formed on the information sides can be wavy.

One optical disc unit can comprise that also zero hands over pick-up unit more, being used to detect the focus of indication light beam and the focus error signal of the misalignment between the information sides hands over more zero, and this control device can become a predetermined value or higher and should zero hand over more pick-up unit to detect this focus error signal and hand over when zero at the magnification that this amplification detection device detects tracking error signal, begins the operation of focus adjusting device.

One optical disc unit also can comprise a bandpass filter, and this tracking error signal can be provided for the amplification detection device through this bandpass filter.

The rotation of this this CD of control device may command so that when this amplification detection device detects the amplification of tracking error signal the revolution of this CD less than the revolution of this CD when the information that writes down on the information sides that reproduces this CD.

The intensity of this control device may command light beam so that when this amplification detection device detects the amplification of tracking error signal the intensity of light beam less than the intensity of light beam when the information that writes down on the information sides that reproduces this CD.

This control device can stop the rotation of CD and carry out the rotation of focus adjustment and control CD so that after the distance between focus that detects light beam and the information sides was in this predictive error limit, CD began to rotate.

Body of the present invention provides a kind of optical disc unit, be used to have the CD of one or more information sides, this optical disc unit comprises: the focus error pick-up unit, be used to export a focus error signal, and indicate the focus of a light beam that is applied to CD and the misalignment between the predetermined surface; Shift unit is used for the position of edge perpendicular to the focus of the direction mobile beam of this CD; Focus adjusting device is used to carry out the focus adjustment of this predetermined surface so that make the focus of light beam and the distance between this predetermined surface in a predictive error limit by control this shift unit according to this focus error signal; Zero hands over pick-up unit more, is used to detect this focus error signal and hands over more zero; And control device, be used to control this focus adjusting device and shift unit, wherein this control device is controlled this shift unit so that more zero along handing over pick-up unit more to detect the friendship of focus error signal for the first time towards the focus of the first direction displacement light beam on a surface of this CD until zero.This control device is controlled this shift unit so that when the friendship that detects focus error signal for the first time is more zero, the focus of light beam is further moved past a preset distance along first direction, this preset distance is greater than the surface of CD and the distance between the information sides, this control device is controlled this shift unit so that moved past this preset distance along first direction and hand over when more zero when detecting focus error signal for the second time up to the focus of this light beam, focus along the second direction orientation information surface displacement light beam relative with first direction, and this control device control focus adjusting device is to hand over when more zero when detecting focus error signal for the second time, execution is to the focus adjustment of information sides, thus the realization above-mentioned purpose.

The present invention also provides a kind of optical disc unit, be used to have the CD of one or more information sides, this optical disc unit comprises: the focus error pick-up unit, be used to export a focus error signal, and indicate the focus of a light beam that is applied to CD and the misalignment between the predetermined surface; Shift unit is used for the position of edge perpendicular to the focus of the direction mobile beam of this CD; Focus adjusting device is used to carry out the focus adjustment of this predetermined surface so that make the focus of light beam and the distance between this predetermined surface in a predictive error limit by control this shift unit according to this focus error signal; Zero hands over pick-up unit more, is used to detect this focus error signal and hands over more zero; And control device, be used to control this focus adjusting device and shift unit, wherein this control device is controlled this shift unit so that hand over more zero along handing over more pick-up unit to detect focus error signal for the first time towards the focus of this surface displacement light beam of this CD until zero.This control device control focus adjusting device is to hand over when zero when detecting focus error signal for the first time, and execution is to this surperficial focus adjustment of CD.When execution was adjusted this surperficial focus of CD, this control device was stored displacement information in memory storage, indicate the displacement of this shift unit according to the rotation angle of this CD.This control device is controlled this shift unit so that stop the operation of focus adjusting device, according to the displacement information of storing in the memory storage, towards the be shifted focus of this light beam of this information sides, hand over more pick-up unit to detect focus error signal for the second time until zero and hand over more zero.And this control device control focus adjusting device is carried out the focus adjustment to information sides to hand over when zero when detecting focus error signal for the second time, thereby realization above-mentioned purpose.

This focus adjusting device may command phase compensation is so that the predetermined period after having begun to operate for focus adjusting device, during than the information of playback light disc recording, and a frequency band broad of phase place leading (phase lead) wherein.

One gain can be set this focus adjusting device so that the predetermined period after having begun to operate for focus adjusting device, and during than the information of playback light disc recording, this gain is less.

The invention provides a kind of optical disc unit, be used to have the CD of a plurality of information sides, this optical disc unit comprises: Electro-Optical Sensor Set, be used for detecting when a light beam is applied to a predetermined surface of these a plurality of information sides, and the light of this CD is left in reflection; The focus error pick-up unit is used for exporting a focus error signal according to the output of this Electro-Optical Sensor Set, indicates the focus of this light beam and the misalignment between this predetermined information surface; The total internal reflection amount detecting device is used for the output according to this Electro-Optical Sensor Set, and detection of reflected is left the amount of the total internal reflection of this CD; With the normalization device, be used for by focus error signal is generated a normalization focus error signal divided by a value, this value is to deduct a signal value that leaves the volume reflection of the information sides except that this predetermined information surface of this CD corresponding to reflection by the output from this total internal reflection amount detecting device to obtain, thereby realizes above-mentioned purpose.

One optical disc unit also can comprise: shift unit is used for the position of edge perpendicular to the focus of the direction mobile beam of this CD; Focus adjusting device is used to carry out the focus adjustment so that make the focus of light beam and the distance between this predetermined information surface in a predictive error limit by control this shift unit according to this normalized focus error signal; With the focus gain measuring device, be used to measure the gain of the system that this focus adjusts, and this signal value can change according to the output of this focus gain measuring device.

One optical disc unit also can comprise: shift unit, be used for the position of edge perpendicular to the focus of the direction mobile beam of this CD, and this signal value can change so that when driving shift unit, the magnification of normalization focus error signal is a constant value, so that the focus of light beam is by the predetermined information surface of (pass through) this CD.

This signal value can change according to these a plurality of information sides respectively.

One optical disc unit also can comprise the diffused light pick-up unit, be used for the light that detection of reflected is left the information sides except that the predetermined information surface of this CD of the focus that falls to having light beam on it, and this signal value can change according to the output of this diffused light pick-up unit.

One optical disc unit also can comprise: shift unit is used for the position of edge perpendicular to the focus of the direction mobile beam of this CD; And control device, be used for controlling this shift unit so that control the focus of this shift unit towards the displacement of the information sides except this predetermined surface of this CD light beam according to the normalization focus error signal.

This Electro-Optical Sensor Set also can comprise: the beam splitting device, be used for reflection become to approach from the photo-fission of switch-board optical axis an interior zone light and away from the light of a perimeter of optical axis; This focus error pick-up unit can comprise the internal focal point error detecting apparatus, be used for light according to this interior zone, detect the focus of light beam and CD the predetermined information surface between misalignment, with the external focal point error detecting apparatus, be used for light according to this perimeter, detect the focus of light beam and CD the predetermined information surface between misalignment; And this control device can be according to one of at least controlling this shift unit in the output of the output of this internal focal point error detecting apparatus and this external focal point error detecting apparatus, so that control the focus of this shift unit towards the displacement of the information sides except this predetermined surface of this CD light beam.

Description of drawings

Fig. 1 is the block scheme according to the exemplary configurations of an optical disc unit of embodiments of the invention 1;

Fig. 2 A is illustrated in the change of position that one on the sequence 1 to 4 assembled the focus of laser beam;

Fig. 2 B is illustrated in the change of the focus error signal FE on the sequence 1 to 4;

Fig. 3 illustrates the example of a CD, formation dish information on the surface of a protective seam of this CD;

Fig. 4 is the block scheme according to the exemplary configurations of an optical disc unit of embodiments of the invention 2;

Fig. 5 illustrates an example of the change in the FE signal;

Fig. 6 diagrammatically is illustrated in the mark road that forms on the CD;

Fig. 7 illustrates the waveform of one TE signal when light beam crosses these mark roads;

Fig. 8 illustrates the waveform of these signals when object lens progressively approach the information sides of CD;

Fig. 9 illustrates the waveform of these signals when carrying out focusing;

Figure 10 is the block scheme of exemplary configurations of the optical disc unit of embodiment 3;

Figure 11 is illustrated in many mark roads that form on the information sides of CD;

Figure 12 illustrates when carrying out focus adjustment, the waveform of these signals when light beam crosses these mark roads;

Figure 13 is illustrated in the waveform of the signal that uses in this optical disc unit;

Figure 14 is the block scheme according to the exemplary configurations of the optical disc unit of embodiments of the invention 4;

Figure 15 is illustrated in the waveform of the signal that uses in this optical disc unit;

Figure 16 is the block scheme according to the exemplary configurations of the optical disc unit of embodiments of the invention 5;

Figure 17 is illustrated in the waveform of the signal that uses in this optical disc unit;

Figure 18 is the block scheme according to the exemplary configurations of the optical disc unit of embodiments of the invention 6;

Figure 19 is the block scheme of the exemplary configurations of a phase compensating circuit;

Figure 20 illustrates the phase propetry of these circuit that comprise in this phase compensating circuit;

Figure 21 illustrates the waveform when carrying out focusing;

Figure 22 illustrates an operating distance;

Figure 23 is the block scheme according to the exemplary configurations of the optical disc unit of embodiments of the invention 7;

Figure 24 illustrates a pair of lamina CD 2187 and a light beam 2106;

Figure 25 illustrates the waveform of these signals that use in this optical disc unit;

Figure 26 is the block scheme according to the exemplary configurations of the optical disc unit of embodiments of the invention 8;

Figure 27 diagrammatically illustrates the structure of a photodetector;

Figure 28 is the block scheme according to the exemplary configurations of the optical disc unit of embodiments of the invention 9;

Figure 29 illustrates the waveform of these signals that use in this optical disc unit;

Figure 30 is the block scheme according to the exemplary configurations of the optical disc unit of embodiments of the invention 10;

Figure 31 when at this control FE on first information surface signal being zero, the outside of this light beam and internal focal point;

Figure 32 illustrates the waveform of an outside FE signal and an inner FE signal; And

Figure 33 illustrates the waveform of these signals that use in this optical disc unit.

Embodiment

Hereinafter with reference to accompanying drawing embodiments of the invention are described.

(embodiment 1)

Fig. 1 shows the exemplary configurations according to the optical disc unit 1001 of embodiments of the invention 1.

This optical disc unit 1001 recorded information and reproduce on the optical disc unit 1100 information of record on a CD 1100.This CD 1100 has an information recording layer 1120 and a protective seam 1110 that is formed on this information recording layer 1120.

This optical disc unit 1001 comprises a shaven head 1002, is used for assembling laser beam irradiation at information recording layer 1120 with one.

This shaven head 1002 comprises a lasing light emitter 1201, optical pickup apparatus 1202, actuator for objective lenses 1204 and object lens 1203.

This lasing light emitter 1201 outputs one laser beam.Be focused by object lens 1203 from the laser beam of these lasing light emitter 1201 outputs.As a result, CD 1100 is by this convergent laser bundle irradiation.The convergent laser bundle that leaves from CD 1100 reflection passes object lens 1203 and is received by optical pickup apparatus 1202.Object lens 1203 are driven by actuator for objective lenses 1204.

Optical pickup apparatus 1202 is for example formed by the light-receiving section that is divided into a plurality of parts.One group of signal (DOUT) from optical pickup apparatus 1202 outputs is provided for focus error calculation element 1003 and information read device 1011.This focus error calculation element 1003 generates a focus error signal (FE) from this sets of signals DOUT.This focus error signal according to this can gathered light the focus of bundle and the distance between the reflecting surface (surface of protective seam 1110 or information recording layer 1120 is described in detail in the back) and change.This focus error signal FE feeds back to the actuator for objective lenses 1204 of shaven head 1002 through a gain amplifier 1009, a switch 1008, adder 1004, low-frequency compensation device 1012 and an actuator drive 1005.

Like this, form a focus adjustment loop by optical pickup apparatus 1202, focus error calculation element 1003, gain amplifier 1009, switch 1008, adder 1004, low-frequency compensation device 1012, actuator drive 1005 and actuator for objective lenses 1204, be used to carry out focus servo.Switch 1008 is unlocked and cuts out this focus adjustment loop.Adder 1004 is used to the output signal of focus shift device 1007 (describing in detail in the back) is added to this focus adjustment loop.

Optical pickup apparatus 1202, focus error calculation element 1303, gain amplifier 1009, switch 1008, adder 1004, low-frequency compensation device 1012, actuator drive 1005 and actuator for objective lenses 1204 are used as focus adjusting device, be used to carry out to the focus adjustment of this reflecting surface so that by driving actuator for objective lenses 1204 according to focus error signal FE, focus that can the gathered light bundle and the distance between the reflecting surface are in a predictive error limit.

Focus shift device 1007 is with respect to optical disc surface, and vertically forced displacement is understood the focus of gathered light bundle.The output signal of focus shift device 1007 is added to the focus adjustment loop by totalizer 1004.

One sequencer, 1006 control focus shift device 1007 and focus adjusting devices.This sequencer 1006 is controlled focus adjusting device by change-over switch between Kai Heguan 1008.When switch 1008 when opening, the focus adjustment loop is closed, and therefore focus adjusting device work.When switch 1008 when closing, the focus adjustment loop is for opening, and so the work of focus adjusting device stop.

Sequencer 1006 for example can be formed by the microprocessor of the program that has formation sequence 1 to 4 (describing in detail in the back).

Below, with reference to the function of Fig. 2 A and 2B explanation sequencer 1006.Following sequence 1-4 is carried out on sequencer 1006 sequences ground.Fig. 2 A is illustrated in the variation of position of the focus of the meeting gathered light bundle on the sequence 1-4.Fig. 2 B is illustrated in the variation of the focus error signal FE on the sequence 1-4.

(sequence 1)

Sequencer 1006 is controlled focus shift devices 1007 so that the focus of meeting gathered light bundle moves towards protective seam 1110.For example carry out such control by the sequencer 1006 of the M that gives an order to focus shift device 1007.In response to order M, a DC electric current is provided for actuator for objective lenses 1204.Therefore, object lens 1203 move with predetermined speed on perpendicular to the direction of CD 1100.

In sequence 1, switch 1008 is turned off.Like this, the focus adjustment loop is opened and focus adjusting device is stopped.

When reflective surface detection means 1010 detected a reflecting surface (being the surface of protective seam 1110), sequence 1 finished.

For example surpass a predetermined threshold (Vth) by detecting focus error signal FE, this reflecting surface can detected (Fig. 2 B).Can carry out such detection by the particular characteristics that utilizes focus error signal, the particular characteristics of this focus error signal be when can gathered light the focus of bundle and the distance between the reflecting surface (but promptly in sensing range time) more in short-term, can obtain to have focus error signal with the approximately proportional amplitude of focus error, and when but this distance is outside sensing range, can not obtain to have the signal (so-called S shape characteristic) of such amplitude.

(sequence 2)

Sequencer 1006 control focus adjusting devices are so that carry out focus adjustment to the surface of protective seam 1110.This carries out by switch 1008 is switched to unblank from shutoff.When reflective surface detection means 1010 detects focus error signal FE above predetermined threshold (Vth), export an output pulse signal P.In response to the edge of output pulse signal P, sequencer 1006 generates a loop unblanking signal (LON), is used for Closing Switch 1008.Like this, switch 1008 is by unblank, and begins the focus adjustment to the surface of protective seam 1110.

When the focus adjustment on the surface of protective seam 1110 was stablized, sequence 2 finished.For example, begin past one predetermined period of time from the focus adjustment after, do not adjust stabilized problem about focus.This predetermined period of time is preferably according to about 10 times (with bigger) of focus adjustment with determined response time period.For example, if corresponding to the response time of the focus adjustment band of 10KHz be 0.1ms, this predetermined period of time is 1ms (=0.1ms * 10) or bigger preferably.

(sequence 3)

The focus adjustment that sequencer 1006 is removed the surface of protective seam 1110.This is performed by switch 1008 is switched to turn-off from unblank.

Then, sequencer 1006 control shift units 1007 are so that focus orientation information recording layer 1120 displacements of meeting gathered light bundle.Such control is performed to focus shift device 1007 by for example sequencer 1006 M that gives an order.In response to this order M, a DC electric current is provided for actuator for objective lenses 1204.Like this, object lens 1203 move with predetermined speed on perpendicular to the direction of CD 1100.

When reflective surface detection means 1010 detected a reflecting surface (being the surface of information recording layer 1120), sequence 3 finished.

This reflecting surface is by detected with the method identical with respect to sequence 1 described method.

(sequence 4)

Sequencer 1006 control focus adjusting devices are so that carry out focus adjustment to the surface of information recording layer 1120.This is performed by switch 1008 is switched to unblank from shutoff.

When the focus of information recording layer 1120 being adjusted when stabilized, sequence 4 finishes.

As mentioned above, adopt, carry out focusing by the control of sequencer 1006 with two steps according to optical disc unit 1001 of the present invention.The first step of this focusing is the focusing to the surface of protective seam 1110.Second step of this focusing is the focusing to the surface of information recording layer 1120.Employing has such focusing of two steps, can significantly reduce the danger of object lens 1203 collision CDs 1100.To describe its reason in detail below.

In sequence 1 and 2, to the surface of protective seam 1110 but not the first step that focuses on is carried out on the surface of information recording layer 1120.This focusing be performed with conventional method in the position away from a position of the thickness of protective seam 1110.In other words, this operating distance is extended the thickness of protective seam 1110.

For example; if the initialization distance is (promptly when focus is on information recording layer 1120; distance between the surface of protective seam 1110 and the object lens 1203) be 150 μ m, the operating distance of essence is 250 μ m, and it adds the thickness 100 μ m of protective seam 1110 for the initialization distance.Therefore, even the amplitude of the swing that rotation produced of CD 1100 is 200 μ m, also can avoid in most of the cases because the surface of the object lens 1203 crash protection layers 1110 that the focusing fault causes.

In addition, in sequence 2, carry out tracking Control to the swing of CD 1100.Like this, in sequence 3 and 4, the swing of CD 1100 is disturbed and can be left in the basket.This is because information recording layer 1120 stands identical swing with protective seam 1110.

In sequence 4, the relative velocity between information recording layer 1120 (will carry out it and focus on) and the object lens 1203 is zero substantially.Like this, can be regarded as be static (on swaying direction) to CD 1100 basically.In sequence 3, the focus adjustment loop is blocked (block), but the duty of the actuator before blocking-up focus adjustment loop is kept by former state.As a result, in sequence 3 and 4, almost can guarantee to carry out focusing to information recording layer 1120.

As mentioned above; according to embodiments of the invention 1, even use the shaven head of object lens, by carrying out focus adjustment to the surface of protective seam 1110 with high NA; and carry out focus adjustment then, can as much as possible avoid the surface of object lens collision CD information recording layer 1120.

Usually, the reflectance R1120 of the reflectance R1110 of protective seam 1110 and information recording layer 1120 is different.Sequencer 1006 uses a gain amplifier 1009 gain suitably to be set to revise poor between reflectance R1110 and the reflectance R1120.

Feedback gain G1110 when execution in sequence 2 is adjusted the focus on the surface of protective seam 1110 and the feedback gain G1120 when execution in the sequence 4 is adjusted the focus on the surface of information recording layer 1120 preferably are set up and satisfy formula (1).

R1110×G1110＝R1120×G1120 (1)

The product that G1110 and G1120 preferably are set to make R1110 and G1110 equals the product of R1120 and G1120.

Feedback gain G1110 and G1120 are set have realized that to satisfy formula (1) loop gain of The whole control system keeps constant.As a result, can carry out the arbitrary stable focus adjustment in the surface of the surface of protective seam 1110 and information recording layer 1120.

The reflectance R1110 on the surface of protective seam 1110 is determined uniquely by the refractive index of protective seam 1110.On the other hand, the reflectance 1120 on the surface of information recording layer 1120 changes significantly according to the material of information recording layer 1120.For example, if the material of protective seam 1110 is normally used polycarbonate resin (polycarbonate resin), the reflectance on the surface of protective seam 1110 is in 3% to 5% scope.Under the situation that can write down and can wipe medium (for example phase-change film), the reflectance R1120 on the surface of information recording layer 1120 is 5% to 20%.Be to rewrite that (for example color type material) is 70% to 90% under the situation of medium.(for example aluminium mirror coating) is 70% to 90% under the situation of readable media only.The reflectance on the surface of information recording layer 1120 has obvious variation according to its material.Like this, unless when focusing on the reflectance R1120 on the surface of Given information recording layer 1120, otherwise can't guarantee to realize satisfying the relation of formula (1).

Reflectance R1120 in order to ensure the surface of acquired information recording layer 1120; for example; the information of indication reflectance R1120 can be formed on the surface of protective seam 1110 of CD 1100 in advance so that (during promptly focusing on the surface of protective seam 1110) during the sequence 2; by using information read device 1011, the information of indication R1120 is read from the surface of protective seam 1110.In sequence 4, sequencer 1006 uses gain amplifier 1009, sets a ride gain according to emission than R1120.

Fig. 3 shows the example of a CD, is formed with optical disc information 1112 on the surface of the protective seam 1110 of this CD.The information of the reflectance R1120 on the surface of this indication information recording layer 1120 is included in the part of dish information 1112 at least.This dish information 1112 can be that the lip-deep bar code that is printed directly on protective seam 1110 maybe can be a label that has bar code or similar printed article to be attached.Information read device 1011 can have any structure, is used for detection as long as it will compare with a predetermined threshold and convert this bar code to a binary value according to this comparative result from each additional signal of the sets of signals DOUT of optical pickup apparatus 1202 output.

(embodiment 2)

Fig. 4 shows the exemplary configurations according to the optical disc unit 2002 of embodiments of the invention 2.

In the present embodiment, a photodetector 2113 and a TE signal generating circuit 2102 (describing in the back) are used as tracking error detecting device.This tracking error detecting device detects and is applied to the misalignment that has an information sides between light beam and the corresponding mark road of CD 2100 of (being formed with many mark roads on this information sides), and exports the tracking error signal of indicating this misalignment.

Photodetector 2113, FE signal generating circuit 2115, phase compensating circuit 2116, power amplifier 2118 and actuator 2104 are used as focus adjusting device.This focus adjusting device carry out focus adjustment so that the distance between the information sides of the focus of this light beam and CD 2100 in a predictive error limit.

One microcomputer 2122 is used as the control device of control focus adjusting device and actuator 2104 (shift unit).

CD 2100 is connected to a motor 2127 and rotates with predetermined revolution.Motor 2127 is by a motor control circuit 2126 controls.The revolution of motor 2127 is set by microcomputer 2122.

CD 2100 has an information sides, forms by many mark roads (not shown among Fig. 4, as to see also Fig. 6 and 22) on it.These many mark roads form spirality, have protruding and concave portion.This CD 2100 can be single-layered disk and can be multilayer disc, comprise dual layer discs.

One laser instrument 2109, coupled lens 2108, polarization beam splitter 2110, quarter wave plate 2107, total internal reflection mirror 2105, photodetector 2113 and actuator 2104 are attached to this shaven head 2114.

Laser instrument 2109 is connected to laser control circuit 2101.Laser controller 2101 drive laser 2109 are so that have the light emitting power of being set by microcomputer 2112.The light beam 2106 that is generated by the laser instrument 2109 that is attached to shaven head 2114 is collimated into directional light by coupled lens 2108, and by polarization beam splitter 2110 and quarter wave plate 2107.Then, this light is reflected and leaves total internal reflection mirror 2105 and be focused and be applied on the information sides of CD 2100 by object lens 2103.

Reflection from the light of the information sides of switch-board 2100 by object lens 2103 and be reflected and leave total internal reflection mirror 2105.Then, this light by quarter wave plate 2107, polarization beam splitter 2110, detect lens 2111 and cylindrical lens 2112 and be incident upon in the photodetector 2113 that includes four light receiving parts.Object lens 2103 are connected to a moveable part of actuator 2104.The actuator 2104 that plays focus direction shift unit and the effect of tracking direction shift unit comprises a focusing coil, a tracking coil, a permanent magnet that is used to focus on and a permanent magnet that is used to follow the tracks of.When using power amplifier 2118 that a voltage is applied to the focusing coil of actuator 2104, an electric current flows through this coil.This coil receives a magnetic force from permanent magnet and is used for focusing on.

Like this, move perpendicular to the direction (being direction up and down in the drawings) of the information sides of CD 2100 on object lens 2103 edges.Object lens 2103 according to the focus error signal Be Controlled of the misalignment between the information sides of indication focus of light beam and CD so that the focus of light beam 2106 always drop on the information sides of CD 2100.

When by power amplifier 2125 voltage being applied to tracking coil, an electric current flows through this coil.This coil receives a magnetic force from permanent magnet and is used for following the tracks of.Like this, object lens 2103 radially (crossing the direction in mark road on the CD 2100, the direction about being in the drawings) and move along CD 2100.

Photodetector 2113 is formed by four light receiving parts.Reflection is sent to focus error signal generation circuit 2115 (hereinafter referred to as FE signal generating circuit 2115) and tracking error signal generation circuit 2102 (hereinafter referred to as TE signal generating circuit 2102) from switch-board and the light that is incident on the photodetector 2113.The focus error signal (hereinafter referred to as the FE signal) of the misalignment between the focus of these FE signal generating circuit 2115 generation indication light beams 2106 and the information sides of CD 2100.

Optical system shown in Fig. 4 has the detection scheme that realization is commonly referred to the FE signal of astigmatic method.The FE signal is sent to power amplifier 2118 through a phase compensating circuit 2116 and a switch 2117.

One electric current flow to the focusing coil of actuator 2104 by power amplifier 2118.Phase compensating circuit 2116 is wave filters, and it shifts to an earlier date a phase place and is used to stablize this focus Adjustment System.Like this, object lens 2103 are driven in response to the FE signal and the focus of light beam 2106 always drops on the information sides.

According to current potential, switch between being connected of the connection of an at one end sub-a of switch 2117 and a terminal c and terminal b and terminal c at control terminal d.In the present embodiment, when the current potential at control terminal d when being high, terminal c and terminal a are connected.When at the current potential of control terminal d when low, terminal c and terminal b are connected.The FE signal also is sent to 1 and hands over testing circuit 2119 more.Hand over more testing circuit 2119 to detect the FE signal to hand over when more zero when zero, it exports a pulse signal.Below, this pulse is called as zero-crossing signal.

Optical system shown in Fig. 4 has a tracking error signal detection scheme of realizing being commonly referred to push-pull method.Below, this tracking error signal is called as the TE signal.TE signal generating circuit 2102 is by this push-pull method, detects misalignment between the mark road of light beam 2106 on the information sides that focuses on and be applied to the CD 2100 that is formed with many mark roads on it and CD 2100.This TE signal is sent to a comparer 2128 through a bandpass filter 2120 (hereinafter referred to as BPF2120) and an amplification detection circuit 2121.

The output of comparer 2128 is sent to microcomputer 2122.Circuit 2123 takes place and generates a signal (being ramp waveform) that changes with constant rate in one slope.The time cycle that generates this ramp waveform is set by microcomputer 2122.The output that circuit 2123 takes place on the slope is sent to power amplifier 2118 through switch 2117.Switch 2117 is switched by microcomputer 2122.One sine wave generating circuit 2124 generates sinusoidal wave.Generate this sinusoidal wave time cycle by microcomputer 2122 settings.The output of sinusoidal wave generation circuit 2124 is sent to power amplifier 2125.

Now, a focusing operation is described.Microcomputer 2122 is set predetermined revolution and is given motor control circuit 2126, and sets predetermined luminous power then and give laser control circuit 2101.Microcomputer 2122 hangs down with splicing ear c and terminal b the current potential of the control terminal of switch 2117.At this moment, do not carry out the focus adjustment.Circuit 2123 takes place and activated with output slope ripple in the slope.Electric current according to this slope ripple flows through focusing coil by power amplifier 2118.

Object lens 2103 are shifted to CD 2100 (in the drawings in the upward direction).Simultaneously, microcomputer 2122 activates sine wave generating circuit 2124 and flows through tracking coil with sinusoidal current by power amplifier 2125.Object lens 2103 are swung with a sinusoidal waveform along the direction of crossing the mark road.

As mentioned above, object lens 2103 are swung near CD 2100 and on the direction of crossing the mark road.When the focus of light beam 2106 near the information sides of CD 2100 and when beginning to cross these mark roads, be sinusoidal waveform from the TE signal of TE signal generating circuit 2102.This TE signal is sent to amplification detection circuit 2121 through BPF2120.Along with light beam moves along the direction perpendicular to these mark roads, amplification detection device, the i.e. amplification of amplification detection circuit 2121 measurement TE signals.BPF2120 removes noise.The passband of BPF2120 is the frequency of TE signal.The frequency of TE signal depends on the spacing in these mark roads and the revolution of dispersion and CD.In common optical disc unit and CD, its scope is from tens of hertz to thousands of hertz.

The magnification of TE signal is detected by amplification detection circuit 2121.When the magnification that detects the TE signal becomes predetermined value or when higher, the focus that the output of comparer 2128 becomes height and light beam is detected and approaches information sides.Then, the focus of light beam is passed through information sides.The FE signal of FE signal generating circuit 2115 outputs is handed over more zero.At this moment, this zero-crossing signal is handed over from zero to get over pick-up unit, promptly zero hands over testing circuit 2119 outputs more.

When the output of comparer 2128 is high level and when when zero hands over more testing circuit 2119 output zero-crossing signals, microcomputer 2122 judges that focuses are on the information sides of CD 2100.In the case, microcomputer 2122 makes the current potential of control terminal d high and connect the terminal c of switch 2117 and terminal a with beginning focus adjustment operation.

The rotation of microcomputer 2122 control CDs 2100 is so that the revolution of CD 2100 during the information that writes down on the information sides of the revolution of the CD 2100 when amplification detection circuit 2121 detects the amplification of TE signal less than reproduction CD 2100.Such control example is that the revolution of motor 2127 is realized by the wheelwork of control rotating disc in this way.After the beginning focus was adjusted, microcomputer 2127 improved the revolution of motor 2127 to the normal revolution that is used for information reproduction.When detecting the amplification of TE signal as mentioned above, by reducing the revolution of CD 2100, can slow down and on focus direction, arrive the speed of information sides, because the swing of CD 2100, this speed may be increased.Therefore, the time cycle that information sides is in depth of focus can be extended, and therefore light beam 2106 can be increased across the mark road number of crossing.As a result, can accurately detect the amplification of TE signal.

The intensity of microcomputer 2122 control bundle is so that the intensity of the light beam of the intensity of the light beam when amplification detection circuit 2121 detects the amplification of TE signal during less than the information that writes down on the information sides that reproduces CD 2100.Such control is to realize by the luminous power of control laser instrument 2109.After the beginning focus was adjusted, the normal power of information reproduction brought up to the luminous power of laser instrument 2109 by microcomputer 2122.When detecting the amplification of TE signal as mentioned above, by reducing the power of light beam, the information of record can be prevented from destroying on the CD 2100,

Fig. 5 shows an example of the change of FE signal.In Fig. 5, a transverse axis represents to adopt the distance between the information sides of the focus of the light beam 2106 that object lens 2103 focus on and CD 210.One Z-axis is represented the level of this FE signal.This FE signal has the waveform that is similar to S shape.Below, this waveform is referred to as S shape waveform.The zero level of FE signal is represented focus and this information sides coupling (promptly being focused) of light beam.When this distance was about 10 μ m, the level of this FE signal was a maximal value.When this distance was elongated, this FE signal was close to zero.Like this, before focus is adjusted, require to carry out initial operation that focus adjusts so that the focus of light beam 2106 and the distance between the information sides in the range L of Fig. 5.

Fig. 6 diagrammatically illustrates the mark road that forms on the CD 2100.Light beam 2106 is applied by the bottom from figure.These mark roads are the part of projection with respect to the bottom among the figure.In Fig. 6, the information sides of CD 2100 is by reference number 2101 expressions, and the surface of CD 2100 is by reference number 2102 expressions.

The tracking error detection scheme that is commonly referred to push-pull method is described below.This push-pull method is also referred to as the far field method.In the method, poor and detected in the light-receiving section output of TE signal by photodetector, wherein these light-receiving sections are divided into two and with respect to symmetry location, the center in these mark roads, this photodetector receives by the mark road reflection of CD 2100 and the light beam of diffraction.

Fig. 7 shows the waveform of TE signal when light beam 2106 crosses these mark roads.When light beam 2106 crossed these mark roads, the TE signal was a sinusoidal waveform.The TE signal is zero at the center in each mark road.

Fig. 8 shows the waveform of signal when object lens 2103 progressively approach the information sides of CD 2100.In Fig. 8, the output of circuit 2123 takes place in waveform (a) expression slope, waveform (b) expression focus, waveform (c) expression FE signal, waveform (d) expression zero-crossing signal, waveform (e) expression TE signal, the output of waveform (f) expression amplification detection circuit 2121, and the output of waveform (g) expression comparer 2128.

When microcomputer 2122 when time t0 begins circuit 2123 takes place on the slope operation, a corresponding current flows through this focusing coil.Like this, object lens 2103 are progressively near the information sides of CD 2100.When in the surface of time t1 focal position and CD coupling, the output zero-crossing signal.Yet at optical disc surface, the level of TE signal is zero.Like this, the output of comparer 2128 remains on low level.And when focal position during further near CD 2100, information sides enters depth of focus.Like this, the TE signal is a sinusoidal waveform.Therefore, the output of amplification detection circuit 2121 output that exceeds E1 and comparer 2128 becomes height.

At time t3, when focus and information sides coupling, the output zero-crossing signal.When further rising object lens 2103, information sides is deviate from depth of focus.Like this, the TE signal reaches zero level.At time t4, the output of comparer 2128 becomes low.Yet,, can guarantee to detect information sides because comparer 2128 is output as lowly.Particularly, if this optical disc unit has current potential height that such structure makes that microcomputer 2122 makes control terminal d with at time t3 splicing ear c and terminal a, even for example the reflectance of information sides is low in double-layer CD, can guarantee to carry out focusing to information sides.

Fig. 9 shows the waveform of carrying out these signals when focusing on.In Fig. 9, the output of circuit 2123 takes place in waveform (a) expression slope, waveform (b) expression focus, waveform (c) expression FE signal, waveform (d) expression zero-crossing signal, waveform (e) expression TE signal, the output of the output of waveform (f) expression amplification detection circuit 2121 and waveform (g) expression comparer 2128.

Waveform (h) expression microcomputer 2122 is exported to the control signal of the control terminal d of switch 2117.At t10, circuit 2123 takes place and starts working in the slope.At time t12, the output of comparer 2128 uprises.

At time t13, focus and information sides coupling and output zero-crossing signal.Microcomputer 2122 makes the current potential height of the control terminal d of switch 2117.

Therefore, the terminal c of switch 2117 and terminal a are connected and the focus adjustment is operated.The focus adjustment of object lens 2103 is performed so that focus drops on the information sides.

The FE signal is also handed over more zero on the surface of CD 2100.Yet, be zero at the level of the TE signal on the surface of CD 2100.Therefore, microcomputer 2122 unlikely oving foci adjustment.Like this, can carry out vernier focusing to information sides.

When CD 2100 was the dish that prerecord has information on it (for example ROM), this information sides can be detected according to a RF signal.Such detection can realize by an additional total internal reflection testing circuit and a RF testing circuit on the structure of optical disc unit shown in Figure 4 2002.

(embodiment 3)

Figure 10 shows the exemplary configurations of the optical disc unit 2003 of embodiment 3.In Figure 10, represent with identical reference number with similar unit in the foregoing description, and omission is to its description.

Figure 11 shows many mark roads that form on the information sides of a CD 2150.Every the mark road is undulatory.In exemplary configurations shown in Figure 11, each bar mark road is directly upwards slightly swung with predetermined period W at it.These slight swings can be detected as misalignment between light beam 2106 and these mark roads by the TE signal.CD 2150 can be a single-layered disk, or multilayer disc, comprises dual layer discs.

Figure 12 shows when the adjustment of execution focus, the waveform of these signals when light beam 2106 crosses these mark roads, and wherein (a) diagrammatically represents these mark roads, waveform (b) expression TE signal, the output of waveform (c) expression BPF2151.Below, the output of BPF2151 is called as swinging signal.When light beam 2016 during at center, a mark road, swinging signal be enlarged into maximum, when light beam 2016 was between the mark road, the amplification of swinging signal was less.Because the slight swing that the footpath in these mark roads that comprise in the TE signal makes progress, this BPF2151 transmits component (pass component).Therefore, the passband of BPF2151 depends on the revolution of W and CD 2150.

Figure 13 shows the waveform of the signal that uses in the optical disc unit 2003.The output of circuit 2123 takes place in waveform (a) expression slope, waveform (b) expression one focus, waveform (c) expression FE signal, waveform (d) expression zero-crossing signal, waveform (e) expression swinging signal, the output of waveform (f) expression amplification detection circuit 2121, the signal of the control terminal d of the output of waveform (g) expression comparer 2460 and waveform (h) expression switch 2117.Microcomputer 2122 activates the slope at time t20 circuit 2123 takes place, and a corresponding current is provided for focusing coil.

As mentioned above, object lens 2103 are progressively near the information sides of CD 2150.At time t21, when the coupling of the surface of focus and CD 2150, the output zero-crossing signal.Because the level of swinging signal is zero.It is low that the output of comparer 2460 keeps.When focus during further near CD, at time t22, information sides enters depth of focus.Like this, swinging signal becomes sine wave-shaped signal.The output of amplification detection circuit 2121 surpasses E2, and therefore, the output of comparer 2460 uprises.At time t23, when focus and information sides coupling, the output zero-crossing signal.High also splicing ear c of the current potential of the control terminal d that microcomputer 2122 makes at switch 2117 and terminal a are to carry out the focus adjustment.

On the surface of CD 2150, the output zero-crossing signal.Yet the output of comparer 2460 is lower.Like this, the level of the current potential of microcomputer 2122 retentive control terminals is low.In switch 2117, terminal b and terminal c are connected and do not carry out the focus adjustment.On the other hand, on the information sides of CD 2150, also detect zero-crossing signal.In the case, comparer 2460 is output as height.Therefore, microcomputer 2122 makes the current potential height at control terminal d.In switch 2117, terminal a and terminal c are connected and carry out the focus adjustment.

Have such structure,, also can guarantee to detect this information sides and guarantee to carry out to focus on even lower as the reflectance of this information sides in double-layer CD.

(embodiment 4)

Figure 14 shows the exemplary configurations according to the optical disc unit 2004 of embodiments of the invention 4.Unit same with the above-mentioned embodiment is represented with identical reference number, and omission is to its description.

When the current potential of terminal a uprised, circuit 2157 took place and generates the signal that changes with constant speed in a slope.The polarity of this speed is positive when the current potential of terminal b is high, and when this current potential is low the polarity of this speed for negative.CD 2100 is with predetermined revolution rotation.One motor control circuit, 2156 control motors 2127 are with predetermined revolution rotation.One laser control circuit, 2155 control laser instruments 2109 are luminous with predetermined power.

Focusing operation will be described.One microcomputer 2158 makes the current potential of control terminal d of switch 2117 low, and splicing ear c and terminal b.Then, microcomputer 2158 makes the slope that the terminal a of circuit 2157 and the current potential height of terminal b take place.As a result, the signal that circuit 2157 generates the positive polarity that changes with constant speed takes place in the slope.The electric current that the output of circuit 2157 takes place corresponding to the slope flows through focusing coil by power amplifier 2128.As a result, object lens 2103 are shifted to CD 2100 (being direction upwards in the drawings).When the coupling of the surface of the focus of light beam 2106 and CD 2100, hand over testing circuit 2119 outputs first zero-crossing signal more from zero.

Going over behind the predetermined period of time M0 from detecting first zero-crossing signal, the current potential that microcomputer 2158 slope takes place the terminal b of circuit 2157 is low from hypermutation.As a result, going over behind the predetermined period of time M0 from detecting first zero-crossing signal, the signal that circuit 2157 generates the negative polarity that changes with constant speed takes place in the slope.Like this, object lens 2103 along the direction (be downward direction in the drawings) from switch-board 2100 move and therefore the focus of light beam along direction displacement (being downward direction in the drawings) towards the information sides of CD 2100.

This predetermined period of time M0 is set up longer than the time of the focus arrival information sides of light beam.Particularly; this predetermined period of time M0 is such cycle time: object lens 2103 are moved further a predetermined distance with the identical direction of direction that moves with object lens 2103 when detecting first zero-crossing signal during it, and this predetermined distance is greater than the thickness of the protective seam of CD 2100.The thickness of the protective seam of CD 2100 is the surface of CD 2100 and the distance between the information sides.

The focus of light beam begins to shift to information sides after it is by information sides, when the focus of light beam was passed through information sides once more, zero handed over testing circuit 2119 outputs second zero-crossing signal more.When microcomputer 2158 detects second zero-crossing signal and is output (focus error signal is handed over more zero for the second time), it make that the current potential of control terminal d is high and connect the terminal c of switch 2117 and terminal a with the adjustment of beginning focus.

Figure 15 shows the waveform of the signal that uses in optical disc unit 2004.In Figure 15, the output of circuit 2157 takes place in waveform (a) expression slope, waveform (b) expression focus, the signal of the terminal b of circuit 2157 takes place in waveform (c) expression slope, waveform (d) expression FE signal, waveform (e) expression zero-crossing signal, and the signal of the terminal d of waveform (f) expression switch 2117.Microcomputer 2158 begins the work that circuit 2157 takes place on the slope at time t30, and corresponding electric current flows through focusing coil.

Therefore, object lens 2103 are step by step near the information sides of CD 2100.At time t31, when the coupling of the surface of focus and CD 2100, the output zero-crossing signal.

When time in the past cycle M0 after detecting first zero-crossing signal, microcomputer 2158 is made as height with the current potential that the terminal b of circuit 2157 takes place on the slope.

At time t32, focus and information sides coupling.Like this, output zero-crossing signal.The output that circuit takes place on the slope reduces with constant speed from time t33.Like this, focus is progressively near information sides.At time t34, focus and information sides coupling, and output zero-crossing signal.High also splicing ear c of the current potential of the control terminal d that microcomputer 2158 makes at switch 2117 and terminal a are with beginning focus adjustment operation.

Have such structure, even as in double-layer CD the reflectance of information sides lower, also can guarantee to detect information sides and guarantee carry out to focus on and do not require the TE signal.

In this programme, focus once was shifted in to the top of information sides.Like this, it is not subjected to the influence at the zero-crossing signal on the surface of CD 2100.

With respect to the surface of CD 2100, the distance that focus approaches CD 2100 is restricted.Like this, object lens 2103 can not collide the surface of CD 2100.Predetermined period of time M0 depends on the sensitivity of focus actuator and the variation of output signals rate that circuit 2157 takes place on the slope.

In the present embodiment, M0 has scheduled volume the time cycle.Yet it can change according to the time span from time t31 to t32.The surface and the distance between the information sides of CD 2100 are scheduled.Like this, it is proportional to move the sensitivity of time of this distance and actuator.

Therefore, even the sensitivity of actuator changes, it also can accurately be shifted focus to information sides to the top.

(embodiment 5)

Figure 16 shows the exemplary configurations according to the optical disc unit 2005 of embodiments of the invention 5.Unit same with the above-mentioned embodiment adopts identical reference number, and omits the description to it.

Focusing operation will be described.2160 settings zero of one microcomputer are that the revolution of motor is given motor control circuit 2126.Laser control circuit 2155 control laser instruments 2109 are with predetermined electric power emission light.Microcomputer 2160 becomes the current potential of the control terminal d of switch 2117 low with splicing ear c and terminal b.Then, the two-terminal a of circuit 2157 takes place with the slope and the current potential of terminal b becomes height in microcomputer 2160.As a result, the signal that circuit 2157 generates a positive polarity that changes with constant speed takes place in the slope.The electric current that the output of circuit 2157 takes place corresponding to the slope flows through focusing coil by power amplifier 2118.As a result, object lens 2103 are shifted to CD 2100 (being direction upwards in the drawings).

Microcomputer 2160 is being gone over behind the predetermined period of time M1 from detecting first zero-crossing signal, and the current potential that microcomputer 2158 slope takes place the terminal b of circuit 2157 is low from hypermutation.As a result, going over behind the predetermined period of time M0 from detecting first zero-crossing signal, the signal that circuit 2157 generates the negative polarity that changes with constant speed takes place in the slope.Like this, object lens 2103 are progressively recessed CD 2100.

This predetermined period of time M1 is set up sufficiently longer than the time of the focus arrival information sides of light beam.Particularly, this predetermined period of time M1 is such cycle time: distance of the thickness of the removable protective seam greater than CD 2100 of object lens 2103 during it.The current potential that the terminal b of circuit 2157 takes place when the slope becomes and detects first zero-crossing signal after low, microcomputer 2160 make that the current potential of control terminal d of switch 2117 is high and connect the terminal c of switch 2117 and terminal a with the adjustment of beginning focus.Microcomputer 2160 activates sine wave generating circuit 2124.If comparer 2128 is output as height, microprocessor 2160 stops the work of sine wave generating circuit 2124 and predetermined revolution is provided with to motor control circuit 2126.If it is low that comparer 2128 is output as, slope generation circuit 2157 is reset and the terminal c and the terminal b of switch 2117 are connected to carry out focusing again.

Figure 17 is illustrated in the waveform of the signal that uses in the optical disc unit 2005.The output of circuit 2157 takes place in waveform (a) expression slope, waveform (b) expression focus, the signal of the terminal b of circuit 2157 takes place in waveform (c) expression slope, waveform (d) expression FE signal, waveform (e) expression zero-crossing signal, waveform (f) expression TE signal, the signal of the control terminal d of waveform (g) expression switch 2117, the output of waveform (h) expression comparer 2128, and waveform (i) expression is sent to the signal corresponding to predetermined number of revolutions of motor 2127 by motor control circuit 2126.

After microcomputer 2160 begins the work of slope generation circuit 2157 at time t40.Corresponding current flows through focusing coil.Like this, object lens 2103 are progressively near the information sides of CD 2100 and pass through information sides.Behind time t40 past one preset time cycle M1, microcomputer 2160 is made as the current potential that the terminal b of circuit 2157 takes place on the slope low at time t41.Then, the output of slope generation circuit 2157 reduces with constant speed since time t41.Therefore, focus is progressively near information sides and in time t42 and information sides coupling.The output zero-crossing signal.

Microcomputer 2160 makes high also splicing ear c of current potential and the terminal a of the control terminal d of switch 2117 operate with the adjustment of beginning focus.Microcomputer 2160 activates sine wave generating circuit 2124 at time t43.If the focus of light beam drops on the information sides, light beam crosses these mark roads and the TE signal is a sinusoidal waveform.If the amplification detection device, promptly to detect the amplification of TE signal be a predetermined value and bigger to amplification detection circuit 2121, and the output of comparer 2128 uprises.Microcomputer 2160 is determined being focused to end normally and predetermined revolution is set to motor control circuit 2126 information sides at time t44.

According to present embodiment, before rotation motor 2127, determine to focus on whether normally finished.Like this, normally do not carried out and therefore under the situation on the surface of object lens 2103 collision CDs 2100, motor 2127 is not rotated when focusing on.Therefore, CD 2100 can be not destroyed in the scope of a broad.And, even lower, also can guarantee to detect information sides and guarantee to carry out to focus on as the reflectance of information sides in double-layer CD.

The control of the rotation of the motor 2127 of Miao Shuing in the present embodiment can be used in any the above embodiments.

(embodiment 6)

Figure 18 shows the exemplary configurations according to the optical disc unit 2006 of embodiments of the invention 6.Unit same with the above-mentioned embodiment adopts identical reference number to represent, and omits the description to it.

In the present embodiment, a single rotation storer 2166 is used as the memory storage of the displacement on the focus direction that is stored in actuator 2104, and this displacement is corresponding to the angle of rotation of CD 2100.

Motor control circuit 2156 control motors 2127 rotate with predetermined revolution.Laser instrument control module 2155 control laser instruments 2109 are luminous with predetermined electric power.One angle of rotation testing circuit 2165 detects and exports the angle of rotation of motor 2127.Below, this signal is called as the angle of rotation signal.Be stored in to this single rotation storer 2166 and angle of rotation signal Synchronization the input voltage of the power amplifier 2118 during one-period of single rotation of CD 2100.Be exported to the value of this storage and this angle of rotation signal Synchronization a totalizer 2167.

Such storage and output function are by microcomputer 2168 controls.‘

In the structure of present embodiment, can measure the open-loop gain of a focus Adjustment System.

Microcomputer 2168 sends to totalizer 2167 with a sine wave, and the terminal c and the terminal a of switch 2117 are closed and carry out the focus adjustment.One object lens, 2103 Be Controlled are so that follow this sine wave that adds to the focus Adjustment System.Microcomputer 2168 catch under this state the FE signal and according to the sinusoidal wave of this addition and amplify and the phase place of this FE signal between relation calculate the open-loop gain of this focus Adjustment System.According to the yield value of this calculating, the gain of amplifier 2400 is changed so that this open loop has a predetermined gain.This predetermined gain is the gain of hypothesis when specifying the leading characteristic of phase place of a phase compensating circuit 2170 (describing in the back).

This phase compensating circuit 2170 is to be used to make phase place to be used for the wave filter of stable focus Adjustment System in advance.

In this structure, phase propetry can be converted with leading in broadband and arrowband.Phase propetry is arranged on carries out focusing in the broadband in advance.Then, after the open-loop gain of regulating the focus Adjustment System, the phase propetry of this band is set in the arrowband leading.Particularly, the one-period between the open-loop gain that focuses on beginning and adjusting focus Adjustment System, this phase place Te Be is arranged in the broadband leading.Because the variation of the variation of the reflectance of CD 2100 and the sensitivity of focus actuator, open-loop gain departs from predetermined gain.Like this, when carry out focusing on, phase propetry is arranged on carries out the focus adjustment in the broadband in advance, and after a gain-adjusted, return phase place leading state in a normal band.

Therefore, focus on and become stable, and can be higher than the open-loop gain of the open-loop gain of focusing in the gain-adjusted setting.

With reference to Figure 19 and 20 phase compensating circuit 2170 is described.

Figure 19 shows the exemplary configurations of phase compensating circuit 2170.First input end 2300 is connected to first phase compensating circuit 2301 and third phase bit compensation circuit 2303.First phase compensating circuit 2301 is connected with second phase compensating circuit 2302.The output of second phase compensating circuit 2302 is connected to a terminal a of a switch 2304.Third phase bit compensation circuit 2303 and being connected in parallel of being connected with third phase bit compensation circuit 2303.Its output is connected to a terminal b of switch 2304.One terminal c of switch 2304 is connected to lead-out terminal 2306.The signal of lead-out terminal 2306 is transfused to single rotation storer 2166 and totalizer 2167.One terminal d of switch 2304 is connected to second input terminal 2305.Second input terminal 2305 is connected to microcomputer 2168.

Figure 20 shows the phase propetry of the circuit that comprises in the phase compensating circuit 2170.In Figure 20, transverse axis indication frequency and Z-axis is represented phase place.The frequency of transverse axis indication is by logarithmically calibrated scale.

(a) in Figure 20, represented the phase propetry of first phase compensating circuit 2301.In first phase compensating circuit 2301, leading in the band of phase place between frequency f 0 and f3.

(b) in Figure 20, represented the phase propetry of second phase compensating circuit 2302.In second phase compensating circuit 2302, leading in the band of phase place between frequency f 2 and f5.

(c) in Figure 20, first phase compensating circuit 2301 of polyphone connection and the phase propetry of second phase compensating circuit 2302 have been represented.In first phase compensating circuit 2301, leading in the band of phase place between frequency f 0 and f5.

(d) in Figure 20, represented the phase propetry of third phase bit compensation circuit 2303.In third phase bit compensation circuit 2303, leading in the band of phase place between frequency f 1 and f4.

Like this, by switching the level of second input terminal, phase propetry can be converted in broadband and leading in the arrowband.

Frequency when open-loop gain becomes 0dB is predefined between f2 and the f3.Like this, first phase compensating circuit 2301 of polyphone connection and second phase compensating circuit 2302 are designed so that phase place becomes maximum in advance between frequency f 2 and f3.First phase compensating circuit 2301 that polyphone connects and the phase compensating circuit of second phase compensating circuit 2302 have be used for this phase place leading than the wideer band of third phase bit compensation circuit 2303.Like this,, can guarantee the phase place tolerance, and therefore this control system is stable even open-loop gain changes.Yet, widen and be used for the increase that the leading band of phase place causes the gain of phase compensating circuit 2170.Like this, because noise or similar, an excessive electric current flows through the coil of actuator.In order to prevent this overcurrent, when first phase compensating circuit 2301 that uses polyphone to connect and second phase compensating circuit 2302, preferably open-loop gain is reduced a bit.

Figure 21 shows the waveform of carrying out when focusing on.In Figure 21, the output of circuit 2123 takes place in waveform (a) expression slope, waveform (b) expression focus, the input waveform of waveform (c) expression comparer 2128, the output waveform of the single rotation storer 2166 of waveform (d) expression, waveform (e) expression FE signal, the signal of the control terminal d of waveform (f) expression zero-crossing signal and waveform (g) expression switch 2117.Microcomputer 2168 make the high and splicing ear a of the current potential of second input terminal 2305 of switch 2304 with terminal c so that be transmitted to lead-out terminal 2306 from first phase compensating circuit 2301 that is connected and the output signal of second phase compensating circuit 2302.Like this, the phase propetry of phase compensating circuit 2170 becomes and has the phase propetry that is used for the leading broadband of phase place.

Microcomputer 2168 makes the current potential of control terminal d of switch 2117 low and connect the terminal c and the terminal b of switch 2117 at time t50.Circuit 2123 takes place and generates the signal that changes with constant speed in the slope.The electric current that the output of circuit 2123 takes place corresponding to the slope flows through focusing coil by power amplifier 2118.Therefore, object lens 2103 are shifted to CD 2100 (being direction upwards in the drawings).When the plane of focus and CD is complementary, export first zero-crossing signal.When detecting first zero-crossing signal, microcomputer 2168 makes the current potential of control terminal d of switch 2117 high and connect the terminal a of switch 2117 and terminal c to carry out the focus adjustment at time t51.

Carry out the focus adjustment so that the focus of light beam is positioned on the surface of CD 2100.

Because CD 2100 swings, object lens 2103 move up and down to follow this swing.Therefore, incoming level and these swings of the power amplification circuit 2118 before activating single rotation storer 2166 are proportional.

Make the cycle of a single rotation of CD 2100 from time cycle of time t51 to t52.The single rotation storer 2166 of microcomputer 2168 orders is stored at time t51.Single rotation storer 2166 storages are from the level of the terminal b of the switch 2117 of t51 to t52.Then, at time t52, the value that single rotation storer 2166 will be stored is exported to totalizer.And then, microcomputer 2168 makes the current potential of control terminal d of switch 2117 low at time t52, thereby connects the terminal c and the terminal b of switch 2117.Microcomputer 2168 makes the slope that the terminal a of circuit 2123 and the current potential height of terminal b take place at time t51, and sends the consistent order that circuit 2123 takes place on the slope of moving.Therefore, the output of totalizer 2167 is the output by the slope is taken place circuit 2123 and the resulting signal of output addition of single rotation storer 2166.Object lens 2103 in response to the output of totalizer 2167 step by step near CD 2100.

When time t53 focus and information sides are complementary, the output zero-crossing signal.Microcomputer 2166 stops the output of single rotation storer 2166, makes the current potential height of the control terminal d of switch 2117, and connects the terminal a and the terminal c of switch 2117.Like this, carry out the focus adjustment so that focus drops on information sides.

Microcomputer 2168 is carried out gain-adjusted, and the gain of amplifier 2400 is changed so that the open-loop gain of focus adjustment becomes predetermined value.

Microcomputer 2166 makes the current potential of second input terminal 2305 of switch 2304 low, and connects the terminal b of switch 2304 and terminal c so that the output signal of third phase bit compensation circuit is output.Like this, the phase propetry of phase compensating circuit is converted with leading in the arrowband.

According to present embodiment, even CD has the swing greater than operating distance, object lens 2103 and CD 2100 can not collide.

Figure 22 shows this operating distance.This operating distance is when focus drops on the information sides, the minor increment K between the upper surface of the surface of CD 2100 and object lens 2103.

According to present embodiment, it is zero substantially that the relative distance of the information sides of object lens 2103 and CD 2100 is reduced to.Like this, focusing is stabilized.

Variation as the sensitivity of the reflectance of the information sides of the CD 2100 of the changed factor in the open-loop gain and focus actuator is below described.Under the situation of double-layer CD, normalization the amplification of the FE signal made a gesture of measuring of reflection the light of another information sides changes and therefore open-loop gain change because reflection is left.According to present embodiment, this open-loop gain is conditioned.Like this, even the reflectance of information sides is lower in double-layer CD, also can guarantee to detect this information sides and guarantee to carry out to focus on.

(embodiment 7)

Figure 23 shows the exemplary configurations according to the optical disc unit 2007 of embodiments of the invention 7.Unit same with the above-mentioned embodiment adopts identical reference number to represent, and omits the explanation to it.

In the present embodiment, a photoelectric sensor 2113 is used as after light beam is focused and is applied to the predetermined information surface of CD 2187, and detection of reflected is left the photoelectric detection system of the light of the CD 2187 with a plurality of information sides.

FE signal generating circuit 2115 is used as the output according to photoelectric detector 2113, the focus error pick-up unit of the misalignment between the focus of detection light beam and the predetermined information surface of CD 2187.

One total internal reflection amount signal generating circuit 2183 is used as the output that is used for according to photodetector 2113, detects the total internal reflection amount detecting device from the total internal reflection amount of CD 2187.

One divider 2185 is used as and is used for the output of the focus error pick-up unit normalization device divided by a value, and wherein this value is the value that is obtained by a signal value that deducts from the output of this total internal reflection amount detecting device corresponding to the volume reflection that leaves from the information sides reflection except this predetermined information surface of this CD.

CD 2187 is to have two information sides, i.e. the pair of lamina CD of the first information surface and second information sides on one side.Motor control circuit 2156 control motors 2127 rotate with predetermined revolution.Laser control circuit 2155 control laser instruments 2109 are with predetermined electric power emission light.Reflection from the light of switch-board 2187 be incident on the photodetector 2113 and be sent to focus error signal generation circuit 2115 and complete in emission measure signal generating circuit 2183.In should be full emission measure signal generating circuit 2183 detect and output reflection from the total internal reflection of switch-board 2187 and be incident on the photodetector 2113.Below, the output of complete interior emission measure signal generating circuit 2183 is called as total internal reflection amount signal.

This total internal reflection amount signal is sent to the terminal b of divider 2185 through a subtracter 2184.One FE signal is transfused to the terminal a to divider 2185.The signal that divider 2185 will input to terminal a is divided by the signal that inputs to terminal b and export from terminal c then.Divider 2185 keeps the constant level of FE signals and the amplification level of FE signal is not subjected to the influence of variation of reflectance of the information sides of CD 2187.Below, the output of divider 2185 is called as normalized FE signal.The output of divider 2185 is sent to power amplifier 2118 through phase compensating circuit 2116 and switch 2117.

Like this, even the reflectance of the information sides of CD 2187 is changed, open-loop gain does not change.Yet in double-layer CD, the light that the information sides except the focal information sides that falls on it is left in reflection is incident on the photodetector 2113.Like this, even adopt total internal reflection comparison FE signal to carry out normalization, the FE signal is lowered level.The light quantity that the out of Memory surface is left in 2184 pairs of reflections of subtracter compensates.Switch 2186 is connected to subtracter 2184.First reflected voltage 2181 and second reflected voltage 2182 are connected to switch 2186.By the order from microcomputer 2180, switch 2186 is exported arbitrary signal in them.

Drop under the lip-deep situation of the first information in focus, first reflected voltage 2181 leaves the light quantity of second information sides corresponding to reflection.Under focus dropped on situation on second information sides, second reflected voltage 2182 left the light quantity on first information surface corresponding to reflection.Therefore, a signal of the volume reflection of the subtracter 2185 output expression first information surfaces or second information sides, the light quantity that the out of Memory surface is left in reflection is removed from it.

The level of first reflected voltage 2181 and second reflected voltage 2182 depends on the characteristic of shaven head 2114, the reflectance and the similar factor of CD 2187.When the focus of light beam by when this information sides moves to second information sides, microcomputer 2180 makes the current potential of control terminal d of switch 2117 low and connect the terminal c and the terminal b of switch 2117.

Microcomputer 2180 sends the driving voltage of the focus focusing coil to second information sides from first information surface that is used for mobile beam through a D/A converter.After the displacement focus, the control terminal d of switch 2117 is changed again for high.Terminal c and terminal a are connected to carry out the focus adjustment.As mentioned above, switch 2186 is to be switched on the first information surface or on second information sides according to the focus of light beam.Like this, can change corresponding to the signal value of reflection from the light quantity of the information sides except the information sides of the focus that falls to having light beam on it of switch-board 2187, it is transfused to this normalization device according to this information sides, i.e. subtracter 2185 (promptly being transfused to the signal value to the terminal b of subtracter).

Figure 24 shows double-layer CD 2187 and light beam 2106.In example shown in Figure 24, this focus is on first information surface.Under the situation of reproducing the information that writes down on the first information surface, carry out the focus adjustment so that focus on first information surface.Under the situation of reproducing the information that writes down on second information sides, the focus adjustment is stopped, and object lens 2103 are made near CD 2187, and behind focus shift to the second information sides, carry out the focus adjustment again.

Be positioned under the lip-deep situation of the first information in focus, light beam L1 is reflected and leaves first information surface and be incident on the photodetector 2113.The FE signal is generated by light beam L1.

Yet the part that transmission is left the light beam L2 of second information sides by first information surface and reflection goes into to be located on the photodetector 2113.The light of reflection does not influence the FE signal but has increased total internal reflection amount signal.Like this, after with this total internal reflection amount signal this FE signal being carried out normalization, the level of FE signal has been reduced the amount of light beam L2.The light quantity that the out of Memory surface is left in reflection under situation second information sides on makes different with focus in focus under the lip-deep situation of the first information.

Then, explanation is moved to focus from the first information surface operation of second information sides.

Figure 25 shows the waveform of the signal that uses in optical disc unit 2007.Waveform (a) is illustrated in the FE signal after the normalization, the output waveform of the D/A converter of waveform (b) expression microcomputer 2180, waveform (c) expression is from the waveform of the terminal d of switch 2186, and the signal of the control terminal d of switch 2117 is exported in waveform (d) expression.Microcomputer 2180 is exported an acceleration pulse since time t60 through D/A converter, is used for focus is moved to second information sides.Like this, object lens 2103 are shifted to second information sides and focus is also shifted to second information sides.Microcomputer 2180 becomes an E3 and stops acceleration pulse at the level that time t61 detects normalized FE signal.When the friendship of this normalization of time t62 FE signal is more zero, the terminal c of switch 2186 is switched to terminal b and is connected with it from terminal a.When the level at this normalized FE signal of time t63 is E3, export this deceleration pulse.During the level of normalization FE signal was E3 or higher cycle, promptly until time t64, this deceleration pulse was output.

When handing at time t561 normalization FE signal when zero, the terminal c of microcomputer 2180 connection switches 2117 and terminal a and carry out the focus adjustment again.According to adopting total internal reflection amount signal by normalized FE signal, the time Be Controlled of output acceleration pulse and deceleration pulse reflects the light quantity of leaving the out of Memory surface and is removed from this total internal reflection amount signal.Therefore, can accurately detect this timing and focus can displacement stably between information sides.

(embodiment 8)

Figure 26 shows the exemplary configurations according to the optical disc unit 2008 of embodiments of the invention 8.Unit same with the above-mentioned embodiment is represented with identical reference number, and omission is to its description.

One photodetector 2188 has five light receiving parts.With respect to embodiment 2, the photodetector 2113 that provides four light receiving parts has been described.In the present embodiment, light receiving part around these four light receiving parts further is provided, and this advances a light receiving part and is used as and is used for the diffusion of light optical detection device that detection of reflected is left the information sides except this predetermined information surface of this CD.

In the present embodiment, photodetector 2188 is by four light receiving parts that formed the photodetector 2113 described in the embodiment 2 and this diffused light pick-up unit, promptly is provided to be grouped into around this light receiver of the outer survey of these four light receiving parts.When being positioned at the light summation as these light receiving parts of the light receiving part inside of diffused light pick-up unit with total internal reflection amount signal.This is the light quantity that is received in the part corresponding to the photodetector 2113 described in the embodiment 2.

As described in reference Figure 24, under the lip-deep situation of the first information, the light that second surface is left in reflection is incident on the overall optical electric explorer 2188 in focus.The light that first information surface is left in most of reflection is incident on these interior lights receiving units.Therefore, reflection leave second information sides and the light that is incident on the interior lights receiving unit proportional with the light quantity that is incident on the exterior light receiving unit.

Deduct by light quantity from this total internal reflection amount signal by subtracter 2184 and multiply by the resulting value of a pre-determined factor this exterior light receiving unit.Like this, obtain not have to reflect the total internal reflection amount signal of the influence of the light that leaves the out of Memory surface.

Figure 27 diagrammatically shows the structure of photodetector 2188.Four light receiving parts in this inside are corresponding to photodetector 2113.This outside light receiver is divided into the part of increase.Focus is similar to embodiment 7 from the class of operation that first surface is displaced to second surface, and therefore omits description it.

(embodiment 9)

Figure 28 shows the exemplary configurations according to the optical disc unit 2009 of embodiments of the invention 9.Unit same with the above-mentioned embodiment is represented with identical reference number, and omission is to its description.

CD 2187 is the pair of lamina CDs that have two information sides on one side.These motor control circuit 2156 control motors 2127 rotate with predetermined revolution.Laser control circuit 2155 control laser instruments 2109 are with predetermined electric power emission light.

Describe detection of reflected and leave the operation of the light on out of Memory surface.The level of the control terminal e of one microcomputer, 2195 changes, one switch 2196 is to connect a terminal a and a terminal b.And the level of the control terminal e of microcomputer 2195 changes one switch 2410 is to connect a terminal d and a terminal c.The terminal c of switch 2410 is set to zero level.Microcomputer 2195 activates the slope circuit 2123 takes place.The output that circuit 2123 takes place on the slope is sent to power amplifier 2118 through switch 2196.Like this, object lens 2103 are near CD 2187.At first export a S shape waveform on the surface of CD 2187.Then, at first information surface output one S shape waveform.Then, export a S shape waveform at second information sides.

The magnification H1 that microcomputer 2195 is measured at the S on first information surface shape waveform and at the magnification H2 of the S of second information sides shape waveform.Microcomputer 2195 be pre-stored in focus be positioned under the situation on this information sides at the magnification Hs of a S shape waveform of single-layer optical disc and the level of a total internal reflection amount signal Cs.On first information surface, this microcomputer 2195 will be established the light that leaves the out of Memory surface to the terminal a of switch 2410 as reflection from the Q1 that formula (2) obtains.At second information sides, the terminal b that the Q2 that obtains from formula (3) is set to switch 2410 leaves the light on out of Memory surface as reflection.

Q1＝Cs·(1-(H1/HS)) (2)

Q2＝Cs·(1-(H2/HS)) (3)

After obtaining Q1 and Q2, carry out focusing on again.Particularly, the level of the control terminal e that changes at switch 2196 of microcomputer 2195 is with splicing ear d and terminal b.And microcomputer 2195 changes the level of control terminal e of switch 2410 with splicing ear d and terminal a again.Microcomputer 2195 activates the slope circuit 2123 takes place.The output that circuit 2123 takes place on the slope is sent to power amplifier 2118 through switch 2196.Like this, object lens 2103 are near CD 2187.When microcomputer 2195 detected first information surface, it changed the level of the control terminal e of switch 2196 and operates with the adjustment of beginning focus with splicing ear d and terminal a.Be shifted in in focus under the situation of second information sides, microcomputer 2195 changes the level of control terminal e of switches 2196 with splicing ear d and terminal c, and exports switch 2196 is given in an acceleration pulse through D/A converter terminal c.And the level of the control terminal e of microcomputer 2195 change switches 2410 is with splicing ear d and terminal b.The level of the control terminal e of microcomputer 2196 change switches 2196 is so that splicing ear d and terminal a operate with the adjustment of beginning focus again.In other words, under the situation that the focus of light beam is shifted, switch 2410 is converted according to these information sides.When focus was on first information surface, terminal a and terminal b were connected, and when focus was on second information sides, terminal b and terminal d were connected.

Figure 29 shows the waveform of the signal that use is worked as in optical disc unit 2009.In Figure 29, the output of circuit 2123 takes place in waveform (a) expression slope, waveform (b) expression focus, and waveform (c) expression is the normalization FE signal of the output of subtracter 2185.At time t70, microcomputer 2195 activates the slope circuit 2123 takes place.Like this, focus is near CD 2187, and at time t71, the level of the normalization FE signal that this is surperficial surpasses E4.And the focus of light beam is near CD 2187, and at time t72, and the level of normalization FE signal becomes and is lower than-E4.

Microcomputer 2195 detects the surface of the focus of light beam by CD 2187.When object lens 2103 are further raise,, surpass E4 at the level of the normalization FE on first information surface signal at time t73.Normalization FE signal was measured and stored to microcomputer 2195 during this cycle maximal value a1 becomes E4 again until normalization FE signal.At time t74, the level of normalization FE signal becomes and is lower than-E4.Microcomputer 2195 becomes at the level of normalization FE signal again-during cycle of E4, measures and the level of the minimum value b1 of storage normalization FE signal, and b1 is a negative value.By deduct the resulting value of b1 from a1 is magnification H1 at the S on first information surface shape waveform.When object lens 2103 were further raise, the focus of light beam was further near CD 2187.At time t75, the level of normalization FE signal surpasses E4.The maximal value a2 of normalization FE signal is measured and stored to microcomputer 2195 during the level of normalization FE signal becomes the cycle of E4 again.At time t76, the level of normalization FE signal becomes and is lower than-E4.Microcomputer 2195 becomes at the level of normalization FE signal again-during cycle of E4, measures and the level of the minimum value b2 of storage normalization FE signal.By deduct the resulting value of b2 from a2 is magnification H2 at the S of second information sides shape waveform.

Microcomputer 2195 uses above-mentioned two formula to calculate Q1 and Q2.In embodiment 9, when focus is passed through this information sides, adopt the amplification of normalization FE signal to come detection of reflected to leave the light quantity on out of Memory surface.Yet when the magnification of normalization FE signal reduced, the open-loop gain of this focus Adjustment System reduced pro rata.Focus gain measuring device (not shown) can be used measuring the open-loop gain of this focus Adjustment System, and according to the gain of this measurement be used for the ratio of the gain of single-layer optical disc, the terminal a of switch 2410 and the value of terminal b can be set up.

(embodiment 10)

Figure 30 shows the exemplary configurations according to the optical disc unit 2010 of embodiments of the invention 10.Unit same with the above-mentioned embodiment is represented with identical reference number, and omission is to its description.

In the present embodiment, one holographic element 2250 is used as the beam splitting device, be used for after light beam is focused and is applied to the predetermined information surface of CD 2187, reflection is become near the light of an interior zone of optical axis with away from the light of a perimeter of optical axis from the photo-fission of switch-board 2187.

One inner FE signal generating circuit 2258 is used as the internal focal point error detecting apparatus, is used for the light according to interior zone, the misalignment between the focus of detection light beam and the predetermined information surface of CD 2187.One outside FE signal generating circuit 2254 is used as the external focal point error detecting apparatus, is used for the light according to the perimeter, the misalignment between the focus of detection light beam and the predetermined information surface of CD 2187.

CD 2187 is the dual layer discs that have two information sides on one side.CD 2187 rotates with predetermined revolution.Laser instrument 2109 is with predetermined power emission light.

Become directional light and transmission by a beam splitter 2256 from the light of laser instrument 2109 emission by collimation lens 2430.

The light beam 2106 of transmission is collected on the CD 2187 by the object lens 2103 as beam condensing unit.The light beam of assembling is reflected/diffraction by the mark road on the CD 2187.

The light beam of this reflection/diffraction is transmission object lens 2103 and be reflected and leave beam splitter 2256 again.

Beam reflected 2106 is separated into diffraction light and 0 grade (0 by this holographic element 2250 as the beam splitting device ^ThOrder) light.This 0 grade of light is assembled by detecting lens 2111 by holographic element 2250, is given 45 ° astigmatism by cylindrical lens 2112 with respect to the mark road, and enters photodetector 2253.

Photodetector 2253 receives this light and exports a signal.This signal is transfused to a control FE signal generating circuit 2257.This control FE signal generating circuit 2257 generates a control FE signal.

Control FE signal is sent to power amplifier 2118 through phase compensating circuit 2116 and switch 2117.Like this, the electric current according to this control FE signal flows through focusing coil.

Assembled by detecting lens 2111 by holographic element 2250 diffracted+1 grade light and-1 grade of light, be given 45 ° astigmatism by cylindrical lens 2112 with respect to the mark road, and enter photodetector 2253.

Photodetector 2253 receives these light, and the light beam of this CD is left in reflection, is divided into the light beam light of the interior zone that is close to optical axis and away from the light beam light of the perimeter of this optical axis, and output signal.These signals are sent to inside and outside FE

signal generating circuit

2258 and 2254 respectively.

In this double-layer CD, each first and second Information Level has the protective seam of different-thickness.Like this, generate spherical aberration.This shaven head be designed so that when the thickness of protective seam is between the thickness of the protective seam of first and second information sides this spherical aberration be zero.Like this, in first information surface, the thinner thickness of this protective seam, and in second information sides, the thickness of this protective seam is thicker.Therefore, the spherical aberration at first and second information sides has opposite polarity.

Because this spherical aberration, be positioned under the lip-deep situation of the first information (promptly under the level of control FE signal on the first information surface is being 0 situation) in focus, the level of inner FE signal becomes positive and the level of outside FE signal becomes negative.

Under focus is positioned at situation on second information sides (promptly under the level of control FE signal on the first information surface is being 0 situation), the level of inner FE signal becomes negative and the level of outside FE signal becomes positive.

When with the focus of light beam during from first information surface displacement to the second information sides, the terminal c and the terminal b of switch 2117 are connected.

Microcomputer 2255 is used for the focus of light beam is sent to through D/A converter from the driving voltage of the focusing coil of first information surface displacement to the second information sides the terminal b of switch 2117.The focus of light beam begins to shift to second information sides.When outside FE signal friendship was more zero, microcomputer 2255 stopped an acceleration pulse and exports a deceleration pulse.

When with the focus of light beam during from first information surface displacement to the second information sides, this outside FE signal at first hand near the second information sides place zero, and then should the friendship of control FE signal more zero.Then, hand over when more zero when outside FE signal, microcomputer 2255 stops deceleration pulse again.

Then, when the friendship of control FE signal was more zero, the terminal c and the terminal a of switch 2117 were connected.Carry out the focus adjustment again.

Then, with reference to Figure 31, the relation between spherical aberration and the focus is described.Figure 31 has illustrated that light beam is when external focal point and internal focal point when control FE signal on first information surface is zero.

As mentioned above, in first information surface, the thickness of protective seam is less than optimum value.Spherical aberration as illustrated instructions.External beam focuses near on the position of object lens 2103.Light beam inside focuses on the position away from object lens 2103.

Be that the thickness of protective seam is greater than this optimum value under zero the situation on second information sides in control signal.Like this, external beam focuses on the position away from object lens 2103.Light beam inside focuses near on the position of object lens 2103.

Like this, when object lens 2103 during near these information sides, outside FE signal and inner FE signal are waveform shown in Figure 32.Solid line is represented inner FE signal and dotted line is represented outside FE signal.Control FE signal is the mean value of outside FE signal and inner FE signal.

As mentioned above, when with focus during from first information surface displacement to the second information sides, this outside FE signal at first hand near the second information sides place zero, and then should the friendship of control FE signal more zero.

Then, describe the operation of focus from first information surface displacement to the second information sides.

Figure 33 has described the waveform of the signal that uses in optical disc unit 2010.Waveform (a) expression FE signal, waveform (b) is illustrated in the waveform of the terminal d of controller 2117, and the output of the D/A converter of waveform (c) expression microcomputer 2255.In waveform (a), dotted line is represented outside FE signal, and heavy line is represented inner FE signal, and fine line represents to control the FE signal.

Microcomputer 2255 is exported the acceleration pulse that is used for focus shift to the second information sides from time t70.Like this, focus is shifted to second information sides.Microcomputer 2255 detects the level of outside FE signal at time t71.Then, microcomputer 2255 output deceleration pulses.

Microcomputer 2255 stops deceleration pulse at time t72, and hands over when more zero at time t73 splicing ear c and terminal a to carry out the focus adjustment again when control FE signal.

According to the optical disc unit of present embodiment, because externally the FE signal is handed over when zero, deceleration pulse can be stopped, and than the situation that stops deceleration pulse according to the level of controlling the FE signal, mode that can accurate timing stops deceleration pulse.As a result, can be stably the focus of light beam be displaced to another information sides from an information sides.

When this optical system is not set to make thickness when protective seam this spherical aberration is zero between the thickness of the protective seam of first and second information sides time.Can determine regularly by using inner FE signal.

Under such situation, according to the information of the spherical aberration of the relevant thickness that depends on the protective seam between the thickness of the protective seam of first and second information sides, can suitably select in outside FE signal and the inner FE signal one of at least.According to this signal, actuator 2104 can be driven and the focus of light beam can be displaced to another information sides from an information sides.

Industrial applicability

In an optical disc unit according to the present invention, after execution is adjusted the focus on the surface of the protective seam of CD.Execution is to the focus adjustment of the information recording surface of CD.Like this, operating distance has been extended the thickness of protective seam in fact.As a result, can significantly reduce the possibility of object lens collisions optical disc surface, even when use has big NA bare headed.

In another optical disc unit according to the present invention, only when the magnification that detects a tracking error signal be a predetermined value or when higher, allow to begin this focus adjustment.Like this, need not be with reference to the level of total internal reflection amount, distinguishablely go out optical disc surface and information sides.As a result, even the difference less (for example, under the situation of double-layer CD) in the middle of the level of the total internal reflection amount of the level of the total internal reflection amount of optical disc surface and information sides can guarantee to carry out the focusing to information sides.

In another optical disc unit according to the present invention, in response to detecting for the second time the more zero focus error signal of friendship.Begin focus adjustment to information sides.Like this, need not be with reference to the level of total internal reflection amount, distinguishablely go out optical disc surface and information sides.As a result, even the difference less (for example, under the situation of double-layer CD) in the middle of the level of the total internal reflection amount of the level of the total internal reflection amount of optical disc surface and information sides can guarantee to carry out the focusing to information sides.

In another optical disc unit according to the present invention, after the swing of recognizing optical disc surface, begin focus adjustment to information sides.Like this, the focus control of information sides is carried out the optical disc surface of learning its swing.As a result, can reduce significantly because the swing of CD makes the possibility of object lens collision CD.

In another optical disc unit according to the present invention, provide the device (normalization device) that is used for accurately calculating from the total internal reflection ratio on this customizing messages surface.Like this, can remove the influence that the light of the information sides except that this customizing messages surface is left in reflection.

Claims

1, a kind of optical disc unit is used to have the CD of one or more information sides, and this optical disc unit comprises:

The focus error pick-up unit is used to export focus error signal, and this focus error signal is indicated the focus of the light beam that is applied to CD and the misalignment between the predetermined surface;

Shift unit is used for the position of edge perpendicular to the focus of the direction mobile beam of this CD;

Focus adjusting device is used to carry out the focus adjustment of this predetermined surface, so that by controlling this shift unit according to this focus error signal, makes the focus of light beam and the distance between this predetermined surface in the predictive error limit;

Zero hands over pick-up unit more, is used to detect this focus error signal and hands over more zero; And

Control device is used to control this focus adjusting device and this shift unit, wherein

This control device is controlled this shift unit, so that along zero to hand over pick-up unit more to detect the friendship of this focus error signal for the first time more zero until this towards the focus of the first direction displacement light beam on the surface of this CD,

This control device is controlled this shift unit, so that hand over when more zero when detecting this focus error signal for the first time, the focus of light beam is further moved preset distance along first direction, and this preset distance is greater than the surface of CD and the distance between the information sides,

This control device is controlled this shift unit, so that after the focus of this light beam has been moved past this preset distance along first direction, and along the focus of second direction orientation information surface displacement this light beam relative with first direction, and

This control device is controlled this focus adjusting device, and zero to hand over more pick-up unit to detect this focus error signal to hand over when zero at this, execution is to the focus adjustment of information sides.

2, according to the optical disc unit of claim 1, wherein this control device is controlled the rotation of this CD, make the rotation that stops CD when focus is adjusted carrying out, and after the distance between focus that detects light beam and the information sides was in this predictive error limit, CD began to rotate.

3, a kind of optical disc unit is used to have the CD of one or more information sides, and this optical disc unit comprises:

Focus adjusting device is used to carry out the focus adjustment of this predetermined surface, so that by controlling this shift unit according to this focus error signal, makes the focus of light beam and the distance between this predetermined surface in a predictive error limit;

This control device is controlled this shift unit so that along towards the focus of the surface displacement light beam of this CD until this zero hand over more pick-up unit detect for the first time this focus error signal hand over more zero,

This control device is controlled this focus adjusting device, and handing over when zero when detecting this focus error signal for the first time, execution is to this surperficial focus adjustment of CD,

When execution was adjusted this surperficial focus of CD, this control device was stored displacement information in memory storage, and this displacement information is indicated the displacement of this shift unit according to the rotation angle of this CD,

This control device is controlled this shift unit, so that stop the operation of focus adjusting device, according to the displacement information of storing in this memory storage, towards the be shifted focus of this light beam of this information sides, until this zero hand over more pick-up unit detect for the second time this focus error signal hand over more zero, and

This control device is controlled this focus adjusting device, and to hand over when zero when detecting this focus error signal for the second time, execution is to the focus adjustment of information sides.

4, according to the optical disc unit of claim 3, wherein this focus adjusting device control phase compensation, so that the predetermined period after having begun to operate for this focus adjusting device, during than the information of playback light disc recording, the leading frequency band broad of phase place wherein.

5, according to the optical disc unit of claim 3, wherein this focus adjusting device is provided with a gain, so that the predetermined period after having begun to operate for this focus adjusting device, during than the information of playback light disc recording, this gain is less.