CN1118798C - Optical head, recording and/or reproducing method and apparatus and method for detecting the thickness - Google Patents
Optical head, recording and/or reproducing method and apparatus and method for detecting the thickness Download PDFInfo
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- CN1118798C CN1118798C CN 99102974 CN99102974A CN1118798C CN 1118798 C CN1118798 C CN 1118798C CN 99102974 CN99102974 CN 99102974 CN 99102974 A CN99102974 A CN 99102974A CN 1118798 C CN1118798 C CN 1118798C
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Abstract
An optical head used for recording/reproducing information signals for an optical disc having a light transmitting layer on a recording layer includes an actuator for the collimator lens. A collimator lens arranged between a light source and an objective lens is moved by the actuator for the collimator lens in a direction of cancelling the spherical aberration ascribable to thickness errors in the light transmitting layer. By this structure, the amount of generation of spherical aberration is reduced even if the numerical aperture NA of the objective lens loaded on the optical head is increased to render it possible to increase the recording capacity of the optical disc.
Description
The present invention relates to a kind of shaven head that is used for writing down and/or duplicate such as carriers such as CDs, and a kind of record and/or reproducing unit that this shaven head is housed.The invention still further relates to a kind of record and/or clone method, and relate to a kind of method of the light-transmitting layer thickness that is used for detecting the carrier that on recording medium, has a light-transmitting layer such as carriers such as CDs.
Such as read-only optical disc, phase transition optical disk, magneto-optic disk or optical recording card or the like carrier are what to be used for storing such as video or audio-frequency information or computer data or the like data specially.In recent years since, the high record density of this carrier and the demand of big recording capacity have been become more and more urgent.
In order to improve the recording density of carrier, it is to increase the numerical aperture NA that is loaded in object lens on the shaven head that a kind of effective method is arranged, and shortens light wavelength, so just can dwindle the size of the laser spots that is formed by object lens.
For the compact disks such as optical digital disk (CD) of early stage appearance, the numerical aperture NA of object lens is 0.45, and used light wavelength is 780nm.On the other hand, for recording density and all higher than the compact disk a kind of optical digital disk DVD of recording capacity, the numerical aperture NA of object lens is 0.6, and used light wavelength is 650nm.
Simultaneously, record on such as carriers such as CDs on the recording layer of information signal a light-transmitting layer is arranged.Recording layer with a carrying information signal when writing down or duplicating shines this recording layer by light-transmitting layer.If there is error in the thickness of light-transmitting layer, its thickness will depart from predetermined value, and this error can produce spherical aberration.For example can represent three rank spherical aberrations with following formula (1):
W
40={ Δ t (n
2-1)/(8n
3) NA
4... (1) Δ t wherein is the thickness error of light-transmitting layer, and n is the refractive index of light-transmitting layer, and NA is the numerical aperture of object lens.
As seen, the spherical aberration that is caused by the thickness error of light-transmitting layer increases with the biquadratic of numerical aperture NA with being directly proportional from formula (1).Therefore, increase numerical aperture for the conclusive effect that has that suppresses spherical aberration.
From formula (1), it can also be seen that,, can also dwindle the thickness deviation of light-transmitting layer, thereby reduce its thickness error in order to suppress the spherical aberration of address signal effectively.For example in DVD, the thickness deviation of light-transmitting layer is ± 0.03mm.If want because the spherical aberration that the thickness error of light-transmitting layer causes is suppressed at the numerical value that is equivalent to the DVD grade, be under 0.6 the situation at numerical aperture NA, just enough as long as the thickness error Δ t of light-transmitting layer is within the scope of formula (2):
-0.00388/NA
4≤Δt≤+0.00388/NA
4 ...(2)
From above-mentioned formula (2), as can be seen, under the situation that enlarges numerical aperture NA, just can find required tolerance value, so that spherical aberration is suppressed at the grade that is equivalent to DVD basically.From formula (2) as seen, if numerical aperture NA=0,7 or NA=0.85, as long as Δ t be respectively-0.016mm≤Δ t≤+ 0.016mm or-0.0074mm≤Δ t≤+ 0.0074mm is just enough.
Yet the thickness deviation that will dwindle light-transmitting layer is very difficult.Although do not need to change significantly technology for mass production system, the precision that improve light-transmitting layer thickness remains difficulty very, and this is because this type of error depends primarily on the manufacture method of carrier.If can realize the precision of light-transmitting layer thickness error, just need thoroughly to change technology, will increase manufacturing cost significantly like this.Therefore, be worthless by dwindling the method that the light-transmitting layer thickness error suppresses spherical aberration.
The purpose of this invention is to provide a kind of shaven head and a kind of record and/or clone method, and a kind of device, even when increasing numerical aperture, still can suppress spherical aberration.
Another object of the present invention provides a kind of record and/or clone method, even still can suppress spherical aberration when increasing numerical aperture.
A further object of the present invention provides a kind of thickness detecting method, so that detect the thickness of a light-transmitting layer above the recording layer that is located at a carrier.
From one side, the invention provides a kind of shaven head that is used for carrier, on carrier, be used for having a light-transmitting layer above the recording layer of recording information signal, this shaven head comprises that is used for a luminous light source, object lens, being used for will be from the optical convergence of light source to recording layer by light-transmitting layer, be arranged on a optical element between light source and the object lens with predetermined refraction, and a mobile device that comes the mobile optical element according to the thickness of light-transmitting layer.
Optical element in the above-mentioned shaven head is a collimation lens preferably, if light-transmitting layer is in the value of regulation, collimation lens drops on the object lens with just allowing light substantial registration that light source sends.
In above-mentioned shaven head, if the numerical aperture NA of object lens is not less than 0.65, the film thickness of the light-transmitting layer of carrier just should be not less than 0.47mm.
Preferably include in the mobile device one with the substantially parallel axis of reference of optical axis from the light of light source directive optical element, an optical element bracing or strutting arrangement that is used for supporting optical component and can moves along axis of reference, a motor, and gearing, be used for converting the rotation of motor to be parallel to optical axis translation motion, and this translation motion is passed to the optical element bracing or strutting arrangement.Gearing converts the rotation of motor to be parallel to optical axis translation motion, is used for mobile optical member supports device, and then optical element is moved, thereby eliminates spherical aberration according to the thickness of light-transmitting layer.
Utilize this shaven head to move a optical element that is located between light source and the object lens, so that eliminate spherical aberration according to the thickness of light-transmitting layer by mobile device with predetermined refraction.Therefore, although in light-transmitting layer, there is thickness error, also can suppress because the spherical aberration that thickness error causes.
On the other hand, the invention provides a kind of record and/or reproducing unit, be used on an a kind of recording layer of carrier, writing down and/or the Copy Info signal, on this recording medium, also has a light-transmitting layer, this device comprises the thickness detection apparatus that is used for detecting light-transmitting layer thickness, and a shaven head that is used for carrier, on carrier, be used for having a light-transmitting layer above the recording layer of recording information signal.This shaven head comprises that is used for a luminous light source, object lens, being used for will be from the optical convergence of light source to recording layer by light-transmitting layer, be arranged on a optical element between light source and the object lens with predetermined refraction, and the mobile device that comes the mobile optical element according to the thickness of the detected light-transmitting layer of thickness detection apparatus.
Optical element in the above-mentioned shaven head is a collimation lens preferably, if light-transmitting layer is in the value of regulation, collimation lens drops on the object lens with just allowing light substantial registration that light source sends.
In above-mentioned shaven head, if the numerical aperture NA of object lens is not less than 0.65, the film thickness of the light-transmitting layer of carrier just should be not less than 0.47mm.
In above-mentioned record and/or reproducing unit, mobile device comprise one with the substantially parallel axis of reference of optical axis that sends and drop on the light on the optical element from light source, an optical element bracing or strutting arrangement that is used for supporting optical component and can moves along axis of reference, a motor, and gearing, be used for converting the rotation of motor to be parallel to optical axis translation motion, and this translation motion is passed to the optical element bracing or strutting arrangement.Gearing converts the rotation of motor to be parallel to optical axis translation motion, is used for mobile optical member supports device, and then optical element is moved, thereby eliminates spherical aberration according to the thickness of light-transmitting layer.
Utilize this record and/or reproducing unit, can move a optical element that is located between light source and the object lens by mobile device, so that eliminate spherical aberration according to the thickness of light-transmitting layer with predetermined refraction.Therefore, although in light-transmitting layer, there is thickness error, also can suppress because the spherical aberration that thickness error causes.
On the other hand, the invention provides a kind of record and/or clone method, be used on a kind of recording layer of carrier, writing down and/or the Copy Info signal, on this recording medium, also has a light-transmitting layer, this method comprises shaven head with illuminating source of employing, object lens, being used for will be from the optical convergence of light source to recording layer by light-transmitting layer, and be arranged on a optical element between light source and the object lens with predetermined refraction, and detect the thickness of light-transmitting layer, come the mobile optical element according to the result who detects, thereby eliminate spherical aberration.
Optical element in the above-mentioned shaven head is a collimation lens preferably, if light-transmitting layer is in the value of regulation, collimation lens drops on the object lens with just allowing light substantial registration that light source sends.
In above-mentioned shaven head, if the numerical aperture NA of object lens is not less than 0.65, the film thickness of the light-transmitting layer of carrier just should be not less than 0.47mm.
Utilize this record and/or reproducing unit, can move the optical element that is located between light source and the object lens by mobile device, so that eliminate spherical aberration according to the thickness of light-transmitting layer with predetermined refraction.Therefore, although in light-transmitting layer, there is thickness error, also can suppress because the spherical aberration that thickness error causes.
Aspect another, the invention provides a kind of detection method that is used for detecting the light-transmitting layer thickness on the recording layer that is located at carrier, on this recording layer, be fit to recording information signal, this method comprises from a light source luminescent, the optical convergence that light source is sent with object lens is to carrier, receive the reflected light that converges to carrier and reflect by object lens with a photoelectric detector that is used for the detection of focus error signal, and the signal section in the focus error signal that produces according to the reflected light of the surface reflection of the reflected light of photoelectric detector reflection and light-transmitting layer detects the thickness of light-transmitting layer from carrier.
In thickness detecting method of the present invention, the thickness of light-transmitting layer detects according to focus error signal, does not need special-purpose pick-up unit just can detect light-transmitting layer thickness.
According to the present invention,, still can suppress because the spherical aberration that the thickness error of light-transmitting layer causes even increased the numerical aperture NA of object lens.So just can improve the recording density and the recording capacity of carrier, not need to improve the manufacturing cost of carrier, the tolerance with the light-transmitting layer thickness error remains on a bigger value simultaneously.
Fig. 1 has represented to be used for embodying a shaven head of the present invention;
Fig. 2 represents to be used for embodying a record of the present invention and/or reproducing unit;
Fig. 3 represents astigmatic aberration;
Fig. 4 is illustrated in the optical pickup apparatus of a photoelectric detector that uses in the astigmatic aberration method;
Fig. 5 is illustrated in the optical pickup apparatus of the another kind of photoelectric detector that uses in the astigmatic aberration method;
Fig. 6 is illustrated in the optical pickup apparatus of another photoelectric detector that uses in the astigmatic aberration method;
Fig. 7 expresses a kind of S-deltoid in the present focus error signal;
Fig. 8 is illustrated in a focus error signal of exporting when optical axis on the direction of pointing to CD moves object lens;
Fig. 9 represents to be used for embodying another embodiment of shaven head of the present invention;
Figure 10 is a planimetric map, is used for being illustrated in the embodiment of a twin shaft driver that uses in the shaven head of Fig. 8;
Figure 11 is a side view, is used for being illustrated in the embodiment of a twin shaft driver that uses in the shaven head of Fig. 8;
Figure 12 is a skeleton view, is used for representing the schematic structure of lens driver;
Figure 13 is the planimetric map of the lens driver shown in Figure 12;
Figure 14 has schematically shown the optical system of first embodiment;
Figure 15 represents the thickness error of light-transmitting layer, wavefront aberration, and the relation between the displacement of a collimation lens among first embodiment;
Figure 16 has schematically shown the optical system of second embodiment;
Figure 17 represents the thickness error of light-transmitting layer, wavefront aberration, and the relation between the displacement of a collimation lens among first embodiment.
Below to explain most preferred embodiment of the present invention with reference to accompanying drawing.
Fig. 1 has represented to be used for embodying a shaven head 1 of the present invention.Shaven head 1 is to be used for a kind of shaven head of a kind of phase change disc 2 of recording/copying.Although be to be example to be used for the shaven head 1 of recording/copying phase change disc 2 herein, the present invention can also be widely applicable for and be used for having above the recording layer of recording information signal the employed shaven head of the sort of carrier of a light-transmitting layer.The carrier that is used for writing down and/or duplicate can be a read-only optical disc, magneto-optic disk or a kind of optical recording card.
1 come recording/copying CD 2 with shaven head, have one and come the recording layer of recording information signal by phase transformation on the substrate 3 of CD, the thickness d of substrate approximately is 1.2mm or 0.6mm, also has a light-transmitting layer 4 on recording layer, and its thickness t approximately is 0.1mm.The effect of light-transmitting layer 4 is protective seams that are used for protecting recording layer.Can be by light recording/copying information signal on CD 2 from the side irradiation of side of light-transmitting layer 4 rather than substrate 3, the film thickness of light-transmitting layer is much thinner than substrate 3.
If allow the optical thickness smaller lateral fall on the recording layer, just can suppress aberration, thereby obtain than common CD or higher recording density and the recording capacity of DVD.Yet the present invention also can be used to utilize from the light of substrate one side incident and writes down and/or the sort of carrier of Copy Info signal.
Referring to Fig. 1, shaven head 1 comprises a light source 10, diffractional lattice 11, polarization beam splitter 12, collimation lens 13 is used for the driver of collimation lens 14, quarter-wave plate 15, object lens 16, the twin shaft driver 17 of object lens, multiple-lens block 18, and a photoelectric detector 19.
In the recording/copying process, light source 10 is towards CD 2 emission light beams, and the suitable emission wavelength lambda of semiconductor laser that constitutes light source is the linear polarization laser of 650nm.For Copy Info signal from CD 2, laser beam of light source 10 emissions with constant output.For recording information signal on CD 2, light source 10 need be according to the signal intensity of modulating outgoing laser beam of record.
The present invention is to the not restriction of wavelength X of light source 10 emitted laser.For example, if semiconductor laser emitted laser wavelength ratio 650nm is short,, just be fit to use short wavelength's laser instrument in order to obtain high record density and high recording capacity.
At first incide on the diffractional lattice 11 and be subjected to diffraction from light source 10 emitted laser.The effect of diffractional lattice 11 is that separation by laser is become at least three parts, is used for so-called bikini rule servocontrol.
The zero order light of diffracted dot matrix 11 diffraction and one-level light (being referred to as incident laser) drop on by two spherical lens 13a by polarization beam splitter 12, on the common collimation lens 13 that constitutes of 13b.
If the thickness t of the light-transmitting layer 4 of CD 2 is in predetermined value, collimation lens 13 just can will incide the laser alignment on the collimation lens 13.In other words, collimation lens 13 is a kind of optical device with predetermined refraction, if the thickness t of the light-transmitting layer 4 of CD 2 is in predetermined value, collimation lens 13 just can make the laser alignment of incident.
Simultaneously, collimation lens 13 is loaded on the driver of collimation lens 14, so that vertically move along the optical axis of incident laser.If the thickness of the light-transmitting layer 4 of CD 2 has broken away from predetermined value, move collimation lens 13 with regard to driver with collimation lens 14, proofread and correct because the spherical aberration that the thickness error of light-transmitting layer 4 causes.That is to say that if the thickness of the light-transmitting layer 4 of CD 2 has broken away from predetermined value, collimation lens 13 will convert incident laser to scattered light or converging light, thereby proofread and correct because the spherical aberration that the thickness error of light-transmitting layer 4 causes.
The incident laser that sends from collimation lens 13 drops on the object lens by quarter-wave plate 15.When light passed through quarter-wave plate 15, the laser of incident dropped on the object lens 16 after being converted into circularly polarized light beam.
Although object lens 16 can be single lens, also can be by shown in Figure 1 by two lens 16a that connect together, 16b constitutes.If object lens 16 are by two lens 16a, 16b constitutes, even enlarge numerical aperture NA, still is easy to mounted lens, and does not need the curved surface of each lens surface is adopted very strict tolerance.That is to say that if can be with two lens 16a, 16b constitutes lens 16, just can compare capacity and enlarge numerical aperture NA, obtain higher recording density and higher recording capacity.
Also can constitute object lens 16 with the lens more than three.If constitute object lens 16, just can relax the curvature of each lens surface with the lens more than three.Yet,, just be difficult to be combined into high-precision lens if the quantity of lens is too much.Thereby need constitute object lens with two lens.
The incident laser that is dropped on after being assembled by object lens 16 on the recording layer of CD 2 is subjected to the reflection of recording layer and becomes Returning beam.This Returning beam is fallen on the quarter-wave plate 15 by object lens 16.Returning beam is at first followed original path by object lens 16, and is converted into linear polarized beam by quarter-wave plate 15, has rotated 90 ° with respect to the polarization of incident light direction.Back light after being aimed at by collimation lens 13 is incided on the polarization beam splitter 12 and is subjected to its reflection.
Back light by polarization beam splitter 12 reflections incides on the photoelectric detector 19 by multiple-lens block 18, is detected by photoelectric detector.Multiple-lens block 18 has a cylinder light entrance face and a concave light output face.Multiple-lens block 18 is operated according to the spherical aberration of back light, carries out focus servo control by so-called spherical aberration method.
Be used for detecting spherical aberration and can comprise six photoelectric detectors through the photoelectric detector 19 that multiple-lens block 18 is in harmonious proportion back light afterwards.The electric signal of photoelectric detector 19 output is directly proportional with the light intensity of back light on dropping on each photoelectric detector, and this electric signal is carried out predetermined calculating, therefrom produce and export such as focus servo signal or tracking servo signal or the like servosignal.
Specifically, detect spherical aberration with photoelectric detector 19 and be in harmonious proportion back light afterwards according to so-called spherical aberration method generation and output focus servo signal through multiple-lens block 18.Shaven head 1 drives the twin shaft driver of the object lens 17 that are loaded with object lens 16 according to these focus servo signals, thereby carries out focus servo control.
Photoelectric detector 19 also will detect the 0 grade of light being subjected to diffractional lattice 11 diffraction and the Returning beam of ± 1 grade of light, produces tracking servo signal according to so-called three beams method, and the tracking servo signal of output gained.Shaven head 1 drives the twin shaft driver of the object lens 17 that are loaded with object lens 16 according to these tracking servo signals, thereby carries out tracking servo control.
When Copy Info signal from CD 2, photoelectric detector 19 also will be handled and incide and return the corresponding electric signal of light intensity on each photoelectric detector according to predetermined algorithm, so that produce and the output replay signal from CD 2.
On of the present invention bare headed 1, object lens 16 are loaded on the twin shaft driver of object lens 17, are used for realizing tracking servo and focus servo control.Or will only be used for focus servo control by the servocontrol that driver moves object lens, carry out tracking servo control by moving whole shaven head simultaneously.
When focusing light on the optical recording layer of CD 2, because the aberration that the thickness error of the light-transmitting layer 4 of CD 2 causes is mainly owing to defocusing or spherical aberration produces by shaven head 1.
Can proofread and correct with focus servo control and to defocus.That is to say, along the optical axis of object lens 16 object lens 16 that move up in front and back, defocus thereby proofread and correct, and focus on the recording layer with the twin shaft driver of object lens 17.On common shaven head, also can carry out this correction to defocusing.
On the other hand, moving up object lens in front and back along optical axis can not the correction of spherical aberration.If can change the refractive index of the object lens 16 or the optical medium of change object lens 16 according to the thickness t of light-transmitting layer 4, just can proofread and correct this spherical aberration.Yet these schemes all are unpractical.
According to of the present invention bare headed 1, the collimation lens 13 that can move up in the front and back along optical axis with the driver of collimation lens 14 is used for proofreading and correct the spherical aberration that the thickness of light-transmitting layer 4 causes.That is to say that adopt of the present invention bare headedly 1, the driver of collimation lens 14 can be used to mobile collimation lens 13, so that eliminate the spherical aberration that the thickness t of the light-transmitting layer 4 of CD 2 causes.
Below to explain spherical aberration that the thickness error owing to light-transmitting layer 4 produces and the method that is used for proofreading and correct this aberration.
If light-transmitting layer 4 has certain thickness error, will produce three spherical aberration W40 that can use formula (1) expression:
W
40={ Δ t (n
2-1)/(8n
3) NA
4... (1) as mentioned above, Δ t wherein is the thickness error of light-transmitting layer, and n is that the refractive index NA of light-transmitting layer is the numerical aperture of object lens.
Formula (1) is to use the numerical aperture NA of object lens to obtain according to the Taylor expansion of aberration amount always, and converts thereof into wavefront aberration.That is to say, if represent numerical aperture NA and, just can obtain following formula (3) with its expansion with sine function:
Sin (θ)=x-x
3/ 6+x
6/ 120-x
7/ 5040+ ρ (x)
8... (3) from second of formula (3) right side as can be seen, wavefront aberration is three spherical aberrations by above-mentioned formula (1) representative.
Yet as can be seen, actual aberration number of times can be higher from formula (3).From the 3rd wavefront aberration of seeing on formula (3) right side is five degree spherical aberration W50 by following formula (4) representative:
W
50＝{Δt(n
3-1)(n
2+3)/48n
5}NA
6 ...(4)
Because the summation that three spherical aberration W50 that the thickness error ti of light-transmitting layer 4 produces and five spherical aberration W60 sums are exactly formula (1) and (4) can be expressed as formula (5):
W≈W
40{[1+{(n
2+3)/6n
2}NA
2} ...(5)
By just can obtaining total aberration to formula (5) differential, and represent with formula (6) with numerical aperture NA:
δS＝{Δt(n
2-1)/2n
3}NA
3[1+(n
3+3)/4n
2}NA
2] ...(6)
Three spherical aberration W40 by above-mentioned formula (1) expression can represent with the aberration sum that produces on each optical flat.That is to say,, just can proofread and correct by arrange the optical element that can produce the spherical aberration of opposite in sign on a bit between light source 10 and the light-transmitting layer 4 certain if having only spherical aberration W40 three times.Yet, from above-mentioned formula (5) as seen, the refractive index n of light-transmitting layer 4 is more little, and the numerical aperture NA of object lens 16 is big more, five spherical aberration W60 role in the spherical aberration that the thickness error Δ t of light-transmitting layer 4 produces is just big more, therefore, it is not enough only proofreading and correct three spherical aberration W40.
It should be noted that three spherical aberration W40 are to 3
The refractive index n of the light-transmitting layer 4 of (=1.732) is maximum, and sharply descends during less than above-mentioned value at the refractive index n of light-transmitting layer 4.The refractive index n of light-transmitting layer 4 is in about 1.5 usually.Therefore, if the effect of five spherical aberration W60 diminishes along with the refractive index n of light-transmitting layer 4 and increases, the effect of this First Five-Year Plan time spherical aberration W60 is just descended by the integral body of total aberration amount and has covered, and can not produce serious problem.
On the other hand, if the numerical aperture NA of object lens 16 increases in the manner described above, the effect of five spherical aberration W60 will increase.This increase of five spherical aberration W60 can not covered.If increased numerical aperture NA, five spherical aberration W60 shared ratio in whole spherical aberration will become maximum, and simultaneously, five times spherical aberration W60 accounts for 40% greatly in overall spherical aberration.Therefore, in the bigger system of numerical aperture NA, need give enough attention to the effect of five spherical aberration W60.
Specifically, suppose numerical aperture NA=0.6, and the refractive index n of light-transmitting layer 4=1.5, total the aberration that thickness error Δ t causes is exactly 30 μ m.If at the formula of considering five spherical aberration W60 (6) total in find out the aberration that thickness error Δ t causes, be exactly its 1.452 μ m.On the other hand, if hypothesis numerical aperture NA=0.85, and the refractive index n of light-transmitting layer 4=1.5, thickness error Δ t is exactly 30 μ m.Total aberration that the thickness error Δ t that finds out from formula (6) causes approximately is 4.850 μ m.That is to say, if the thickness deviation of light-transmitting layer 4 be ± 0.03mm, numerical aperture NA is 0.6, total aberration that the thickness error Δ t of light-transmitting layer 4 causes just can not surpass 1.452 μ m.Yet, if being 0.85, five spherical aberration W60, numerical aperture NA will increase, make the capable height of total aberration can reach 4.850 μ m.
In order to proofread and correct above-mentioned spherical aberration, the spherical aberration value with formula (6) expression is identical and aberration opposite in sign is just enough if can produce one.The simplest method is exactly to insert a parallel flat board between light source 10 and the collimation lens 13 that is used to proofread and correct.In this case, if can satisfy formula (7) and (8):
{(n1
2+3)/n1
2}NA1
2＝{(n0
2+3)/n0
2}NA0
2 ...(7)
{ (n1
3-3)/n1
3NA1
4={ (n0
2-1)/n0
3NA0
4... (8) just can proofread and correct five spherical aberration W60.In these formula, NA0, n1 and NA1 are the refractive index of collimation lens 13 in incident light one side, the refractive index of light-transmitting layer 4, and the numerical aperture of object lens 16.
In order to satisfy formula (7) and (8), consider the actual allowable value of refractive index, the NA1 of object lens 16 and collimation lens 13 need keep equal value at the NA0 of incident light one side.Specifically, need to satisfy the relation of NA1/NA0≤2 at least.But, in fact can not when increasing the NA1 of object lens 16, increase the NA0 value of collimation lens 13 incident lights one side.Therefore, adopt the method for between light source 10 and collimation lens 13, inserting parallel flat can not proofread and correct this spherical aberration fully.
In addition, not the optical element of parallel flat if adopt, iff optical element is arranged on the optical axis, just be difficult to fully proofread and correct whole spherical aberration.As seen, the numerical value of three spherical aberration W40 and five spherical aberration W60 logarithm value aperture NA is different from formula (1) and (4).Therefore need carry out correction with a kind of method of complete equipilibrium, consider the thickness deviation of light-transmitting layer 4, this aberration should be within the margin tolerance fully.
Therefore, if adopt of the present invention bare headed 1 correction that just can realize complete equipilibrium, three-dimensional collimation lens 13 is moved along optical axis with the driver of collimation lens 14.When collimation lens 13 moves up in front and back, just can change the numerical aperture NA of object lens 16, thereby make spherical aberration obtain proofreading and correct in incident light one side.
Simultaneously, in of the present invention bare headed 1, the diameter of the emergent pupil of collimation lens 13 should be more much bigger than the diameter of the entrance pupil of object lens 16.In this case,, also remain unchanged basically, so just can finish stable recording/copying at the numerical aperture NA of object lens 16 smooth outgoing one sides even change the numerical aperture NA of object lens 16.
In this shaven head, collimation lens 13 mainly is to set according to the coupling efficiency that improves the incident laser that sends from light source at the numerical aperture NA of incident light one side.Specifically, numerical aperture NA should be set in about below 0.3.On the other hand, in order to dwindle the diameter that is focused at the light on the recording layer, the numerical aperture NA of object lens 16 should select bigger value.Use recording density and the recording capacity higher than DVD if desired, this numerical aperture NA just should be set in and be not less than 0.65.
That is to say that according to of the present invention bare headed 1, collimation lens 13 should be set in such value at the numerical aperture NA of incident light one side, it is significantly less than the numerical aperture NA of object lens 16 in emergent light one side.According to this setting means, mainly be three spherical aberration W40 owing to collimation lens 13 moves the spherical aberration that produces along optical axis.Therefore, can not eliminate fully by mobile collimation lens 13 because whole spherical aberrations that the thickness error Δ t of light-transmitting layer 4 causes.
Therefore, in the process of mobile collimation lens 13, need to set the moving target position of collimation lens 13, allow the mean square value of aberration become minimum.Specifically, the optical path difference of main beam and environment light beam is calculated by light tracking method, and the LMS least mean square of the wavefront aberration that the acquisition optical path difference just precomputes on the position of collimation lens.When CD 2 is carried out recording/copying, need to detect the thickness t of light-transmitting layer 4, and collimation lens 13 is moved on the position that precomputes according to error delta t by the driver of collimation lens 14.
In this bare headed 1, the displacement of collimation lens 13 should be more much smaller than the focal length of collimation lens 13, and therefore, the wavefront aberration Wrms that is produced by moving of collimation lens 13 will be more much smaller than the focusing of collimation lens 13.In this case, the value of the spherical aberration that the amount of movement of collimation lens 13 produces during with mobile collimation lens 13 is directly proportional, and has so just simplified the structure and the type of drive thereof of the driver of collimation lens 14.In other words, if the displacement of collimation lens 13 is far smaller than the focusing of collimation lens 13, be very favorable to the structure of servo control mechanism.
In above-mentioned shaven head 1, because the spherical aberration that the thickness error Δ t of light-transmitting layer 4 causes is proofreaied and correct by mobile collimation lens 13.Yet, because the spherical aberration that the thickness error Δ t of light-transmitting layer 4 causes also can be proofreaied and correct with other any suitable optical devices except that collimation lens 13.
According to the present invention, as long as will be used for proofreading and correct because the optical element of the spherical aberration that the thickness error Δ t of light-transmitting layer 4 causes is arranged between light source 10 and the object lens 16 just enough.For example, lens that are located between light source 10 and the collimation lens 13 can move up in front and back along optical axis.Or saving collimation lens 13, the light that allows light source 10 send is fallen on the object lens 16 with the state of diverging light.In this case, as long as lens are located on the light path that incides the diverging light on the object lens 16, and it is just enough to move up in front and back along optical axis.
Yet, come the correction of spherical aberration with the collimation lens 13 in above-mentioned bare headed 1 if desired, and the thickness of light-transmitting layer 4 is in predetermined value, the incident laser on the object lens 16 is exactly the light of collimation, therefore, object lens 16 just can resemble and work the parallel system lens of being convenient to operate.Therefore, under actual conditions, can resemble bare headed 1 with the optical device of collimation lens 13 as the correction of spherical aberration.
Although the correction of the spherical aberration that above-mentioned explanation is the thickness error Δ t at light-transmitting layer 4 to be caused is explained, can also allow the optical element that is used for aberration correction move, be used for the variation of testing environment, variation of temperature for example, CD 2 is in the radial direction inclination, the variation of the refractive index n of light-transmitting layer 4, or the dislocation of the optical element of formation shaven head 1 or the like, and be used for proofreading and correct the aberration that causes by these factors.
Wish also that simultaneously this bare headed 1 can expand the numerical aperture NA of object lens 16 to the requirement of satisfying DVD, so that further improve recording density.As indicated above, numerical aperture NA should be set in and be not less than 0.65.
Yet, if increased the numerical aperture NA of object lens 16, the problem that comatic aberration increases also can appear except above-mentioned spherical aberration.Comatic aberration is that the radial skew owing to CD 2 produces, and along with the cube direct ratio of the numerical aperture NA of object lens 16 increases.Therefore, along with the increase of numerical aperture NA, the problem that suppresses comatic aberration just becomes more important.
In order to suppress comatic aberration, the thickness t that reduces light-transmitting layer 4 is a kind of effective method.For example in DVD, the pitch angle of radial skew is ± 0.4 °, in order to keep necessary tolerance value, the thickness t of light-transmitting layer 4 should satisfy following formula (9):
t≤0.1296/NA
3 ...(9)
For instance, if the t≤0.47mm of formula (9) is satisfied in NA 〉=0.65.Therefore, if the numerical aperture NA of the object lens 16 in the shaven head 1 is not less than 0.65, just the thickness t of light-transmitting layer 4 should be set in below the 0.47mm.Therefore, in order to obtain high record density, be not less than 0.65, just the tolerance of the thickness t of light-transmitting layer 4 can be maintained the value that satisfies common DVD if the numerical aperture NA of object lens 16 is set in.
From above-mentioned formula (9), as can be seen,, allow NA 〉=0.7 if increase the numerical aperture NA of object lens 16 again, just should t≤0.37mm.If further increase the numerical aperture NA of object lens 16, allow NA 〉=0.85, just should t≤0.21mm.
In general, it is inconvenient obtaining narrow radial skew tolerance.If desired, its expense will increase significantly.Yet if can reduce the thickness t of light-transmitting layer 4 along with the numerical aperture NA of object lens 16 fully, so that reach the purpose that increases recording density by the numerical aperture NA that increases object lens 16, the radial skew tolerance just can remain on the desired value of common DVD.Therefore,, just can obtain higher recording density if reduce the thickness t of light-transmitting layer 4 along with the increase of the numerical aperture NA of object lens 16, can be owing to the too small expense that makes of radial skew tolerance rises significantly.
An embodiment as record of the present invention and/or reproducing unit has represented a kind of recorder/reproducer apparatus 30 in Fig. 2, it has a shaven head 1 that is used for recording/copying CD 2 as indicated above.
Illustrate that with reference to being used for the recorder/reproducer apparatus of recording/copying phase transition optical disk 2 the present invention can also be used to have the various types of records and/or the reproducing unit of shaven head although be hereinafter.The carrier that is used for writing down and/or duplicate can be a kind of read-only optical disc, magneto-optic disk, or a kind of optical recording card.
Recorder/reproducer apparatus 30 comprises that is used for rotating a spindle motor 31 that drives CD 2, be used for the shaven head 1 of recording/copying information signal, be used for moving the feeding motor 32 of shaven head 1, be used for carrying out a modulation-demodulation circuit 33 of modulating/demodulating work, a servo-controlled servo control circuit 34 that is used for shaven head 1, and a system controller 35 that is used for controlling total system.
When the recording/copying information signal, the shaven head 1 with laser radiation on CD 2, detect the light that returns along with the rotation of CD 2.When recording information signal, be sent to shaven head 1 by external circuit 36 transmission and with the signal that modulation circuit 33 is modulated according to predetermined way, use the laser beam irradiation of modulating according to light intensity then on CD 2.When the Copy Info signal, shaven head 1 on the CD 2 that rotates, and produces replay signal according to back light with the laser beam irradiation of a constant output, and replay signal is offered modulation-demodulation circuit 33.
Modulation-demodulation circuit 33 is connected to system controller 35 and external circuit 36.During recording information signal, modulation-demodulation circuit 33 is receiving the signal that need be recorded on the CD 2 from external circuit 36 under the control of system controller 35, and the signal that receives is modulated on CD 2.Be sent to shaven head 1 through the signal after modulation-demodulation circuit 33 modulation.When Copy Info signal from CD 2, modulation-demodulation circuit 33 receives the signal that is produced by CD 2 under the control of system controller 35, replay signal is modulated.The signal of modulated demodulator circuit 33 demodulation outputs to external circuit 36 from modulation-demodulation circuit 33.
Feeding motor 32 be used to along CD 2 radially shaven head 1 is transported to preposition, it is by driving from the control signal of servo control circuit 34.That is to say, feeding motor 32 is connected to servo control circuit 34 and is subjected to its control.
In addition, in embodying recorder/reproducer apparatus 30 of the present invention, servo control circuit 34 can also be operated as pick-up unit, detects the thickness t of the light-transmitting layer 4 of CD 2 according to focus servo signal.The method that detects the thickness of light-transmitting layer 4 with servo control circuit 34 below will be described.
In the middle of the focus servo signal that the photoelectric detector 19 of photoelectric detector 1 sends, comprise and focus on propel signal and focus error signal.Represent the light quantity of whole back lights of CD 2 reflection with the focusing propel signal, and be used for object lens 16 are moved near the focal position.After near object lens 1 being moved to focal position according to the focusing propel signal, object lens 16 are remained on the position that just focuses on focus error signal.
Recorder/reproducer apparatus 30 obtains focus error signal according to the spherical aberration method.In the spherical aberration method, the optical element of the parallel flat formula that glass plate is made is arranged in the optical convergence path of back light, be used for deliberately producing a very big spherical aberration, detect the shape of light beam in the front and back of circle of least confusion, therefrom obtain focus error signal.
Be that example is explained the spherical aberration method with a parallel flat 20 as shown in Figure 3 below.Although the shaven head shown in Fig. 11 has adopted multiple-lens block 18 as the optical element that produces spherical aberration, used parallel flat 20 herein for simplification as the optical element that produces spherical aberration.
If parallel flat 20 as the optical element that produces spherical aberration, just can be obtained spherical image residual quantity δ y from following formula (10):
δ y={ (n2-1) sin2 θ * t}/(n2-sin2 θ) 3/2 ... (10) θ wherein, n and t represent the angle of back light opening respectively, are arranged in the refractive index and the thickness thereof of the parallel flat 20 on the limited light path.
In order to detect focus error signal, detect light beam with spherical aberration with a photoelectric detector with the spherical aberration method.Fig. 4 to 6 has represented the light receiver 21 of a photoelectric detector of suitable use spherical aberration method detection of focus error signal.This light receiver 21 has the shape of rectangle, and is divided into four sections with two vertical dividers.When just being in focus state on the recording layer of laser at CD, if being set in the light beam spot 22 that allows on the light receiver 21, photoelectric detector becomes circle of least confusion, the light beam spot 22 on the light receiver 21 will become oval-shaped point under the non-focusing state.If use A, B, C and D represent each section of light receiver 21, by a current-voltage switching amplifier the performed amplification of light quantity that light receiver 21 receives are calculated, and the focus error signal FE that is obtained is exactly voltage signal FE=(A+C)-(B+D).
If laser beam is focused on the recording layer of CD, the light beam spot of introducing in the district 21 22 is exactly oval-shaped, as shown in Figure 4.Light quantity in each section of light receiver 21 is (A+C)=(B+D), therefore, and FE=0.
If near laser focus point, the light beam spot 22 on the light receiver 21 is exactly oval-shaped to the recording layer of CD, as shown in Figure 5 more.Light quantity in each section of follow-up 21 of light is (A+C)＜(B+D), therefore, and FE＜0.
If the recording layer of CD is away from laser focus point, the light beam spot 22 on the light receiver 21 is exactly oval-shaped, as shown in Figure 6.Light quantity in each section of follow-up 21 of light is (A+C)＞(B+D), therefore, and FE＞0.
As shown in Figure 7, if focusing deviation is plotted on the transverse axis, the output of focus error signal is plotted on the longitudinal axis, thus obtained focus error signal just can be represented with a sigmoid curve.The point that zero point, representative just focused at sigmoid curve center.Simultaneously, the scope Wa from a peak value Pa of sigmoid curve to the peak value Pb of opposite side is commonly called the focusing Propulsion Range.
In order to realize focus servo control in 1, need drive the twin shaft driver of object lens 17 when focusing on propel signal detecting, so that object lens 16 are moved up in front and back along optical axis at shaven head.According to focus on propel signal make the focus of object lens be positioned at recording layer near.When the focus of object lens 16 be positioned in recording layer near, and object lens 16 are in when focusing within the Propulsion Range, just utilize the twin shaft driver of object lens 17 to move gradually on fore-and-aft direction along optical axis by object lens 16, keep the position that just focuses on from start to finish, allow focus error signal be in zero point all the time.So just can be set in focus state all the time with respect to recording layer.
The principle of focus servo control more than has been described.In habitual recorder/reproducer apparatus, the focus error signal FE that the back light that reflects from recording layer obtains is used to realize focus servo control.Yet the laser of incident not only is subjected to the reflection of recording layer, also can be subjected to being on the CD 2 light-transmitting layer 4 lip-deep surface reflections more or less.Owing to the back light of the surface reflection of light-transmitting layer 4 forms sigmoid curve shown in Figure 7.In the following description, the sigmoid curve that occurs focus error signal owing to the back light of the surface reflection of light-transmitting layer 4 is called as first sigmoid curve, and because the focus error signal that the back light of the recording layer surface reflection of CD 1 causes is called as second sigmoid curve.
According to the first and second above-mentioned sigmoid curves of recorder/reproducer apparatus 30 responses of the present invention, detect the thickness t of light-transmitting layer 4 according to focus error signal.That is to say, in recorder/reproducer apparatus 30 of the present invention, with the twin shaft driver of object lens 17 object lens 16 were moved forward and backward along optical axis before recording/copying operation beginning, the surface up to the focal position of object lens from light-transmitting layer 4 moves on on the recording layer.Detect the thickness t of light-transmitting layer 4 according to the focus error signal of the translational speed of object lens 16 and corresponding first and second sigmoid curves.
Below to be described with reference to Fig. 8.In Fig. 8, represented when object lens 16 near the direction of CD 2 when optical axis moves the focus error signal of output, the transverse axis among the figure and the longitudinal axis are represented the focus error signal of time and output respectively.
In Fig. 8, W1 is the needed time of focusing Propulsion Range that object lens 16 stride across first sigmoid curve.That is to say, W1 represents focus error signal along with moving of object lens 16 changes to the needed time of minimum value from maximal value, and P1 has represented light-transmitting layer 4 lip-deep focus points of CD 2, just the point that just focuses on respect to the surface of light-transmitting layer 4.
In Fig. 8, W2 is the needed time of focusing Propulsion Range that object lens 16 stride across second sigmoid curve.That is to say, W2 represents focus error signal along with the mobile maximal value from second sigmoid curve of object lens 16 changes to the needed time of minimum value, and P2 has represented light-transmitting layer 4 lip-deep focus points of CD 2, just the point that just focuses on respect to recording layer.
In addition, light-transmitting layer 4 lip-deep one P1s one the time that P2 experienced up to the recording layer that focus on CD 2 on of the representative of the W3 among Fig. 8 from focusing on CD 2.
In this case, be A if focus on the length of Propulsion Range, just can obtain the thickness t of light-transmitting layer 4 with following formula (11):
t＝W
3×{(A/W
1)
2+(A/W
3)
2}
1/2 ...(11)
Simultaneously, in shaven head commonly used at present, the length A that focuses on Propulsion Range is set at about 20 μ m.
In according to recorder/reproducer apparatus 30 of the present invention, servo control circuit 34 obtains the thickness t of light-transmitting layer 4 according to formula (11).Therefore, the servo control circuit 34 of recorder/reproducer apparatus 30 can be used as a kind of thickness detection apparatus, is used for detecting the thickness of light-transmitting layer 4.
Although can the thickness t of light-transmitting layer 4 only be detected once, best mode obtains a mean value by repeated detection.That is to say, in the process that detects light-transmitting layer 4 thickness t, move forward and backward the twin shaft driver of object lens 17 repeatedly, obtain the thickness t of light-transmitting layer 4 repeatedly, therefrom find a mean value according to for example 100 to 200Hz preset frequency.So just can more accurately detect the thickness t of light-transmitting layer 4.
The servo control circuit 34 that detects the thickness t of light-transmitting layer 4 in the manner described above sends a control signal to CD 2, utilize the driver of collimation lens 14 to come mobile collimation lens 13, the spherical aberration that the thickness error of light-transmitting layer 4 may be caused according to this control signal reduces to minimum.After the spherical aberration that the thickness error to light-transmitting layer 4 causes was proofreaied and correct, recorder/reproducer apparatus 30 was as common recorder/reproducer apparatus executive logging/replicate run.
In recorder/reproducer apparatus 30 of the present invention, the thickness t of light-transmitting layer 4 was measured before the recording/copying operation, so that can proofread and correct the spherical aberration that thickness error causes.Therefore,, still can suppress the generation of spherical aberration even there is thickness error in the thickness t of light-transmitting layer 4, thus executive logging/replicate run in the best condition.
Adopt shaven head of the present invention, just be enough to eliminate the spherical aberration that depends on light-transmitting layer thickness as long as move the optical element with predetermined refraction, therefore, this shaven head is not limited in structure shown in Figure 1.Below to describe the various change forms of shaven head of the present invention with reference to Fig. 9 to 11 in detail.
Shaven head 100 shown in Figure 9 is a kind of shaven heads that are used for recording/copying phase transition optical disk 101.Be fit to have a substrate 102, be located at an on-chip recording layer, can come recording information signal by phase change, and be located at a light-transmitting layer 103 above the recording layer with the CD 101 of this bare headed 100 recording/copyings.With the light that incides light-transmitting layer 103 1 sides CD 101 is write down or duplicates.
Shaven head 100 comprises first optical system 104 and one second optical system 105 of light-transmitting layer 103 thickness that are used for detecting CD 101.For recording/copying information signal on CD 101, second optical system 105 need be proofreaied and correct the spherical aberration that the thickness error of the light-transmitting layer 103 of CD 101 causes according to the thickness of the light-transmitting layer 103 of first optical system, 104 detected CDs 101.
First optical system 104 comprises a light source 106, polarization beam splitter 107,108, one object lens 109 of collimation lens, and a photoelectric detector 110.
Light source 106 is luminous towards CD 101.It is 635 semiconductor lasers to the 650nm short wavelength laser that light source 106 can adopt an emission wavelength.The laser that light source 106 sends is subjected to the reflection of polarization beam splitter 107 and falls on the collimation lens 108 afterwards.
With two spherical lens 108a that are bonded to together, the collimation lens 108 that 108b constitutes will incide the laser alignment on the collimation lens 108.The laser that collimated lens 108 are aimed at drops on the object lens 109.
The laser that incides on the object lens 109 is fallen on the recording layer of CD 101 by light-transmitting layer 103 after object lens 109 convergences.Object lens 109 are loaded on the twin shaft driver 111, can move on the direction of optical axis and perpendicular direction.
Be subjected to through the laser on the recording layer that drops on CD 101 after the convergence of object lens 109 having become Returning beam after the reflection of recording layer.This back light goes down along the original light path that strides across polarization beam splitter 107, incides at last on the photoelectric detector 110.
The thickness that first optical system 104 detects the light-transmitting layer 103 of CD 101 according to the light-transmitting layer 103 and the lip-deep focus error signal of recording layer of CD 101.
Second optical system 105 comprises 112, one cylindrical lenses 113 of a light source, polarization beam splitter 114, collimation lens 115, diffractional lattice 116, light path promotes catoptron 117,118, one groups of two object lens 119 of quarter-wave plate, and a photoelectric detector 120.
By emission wavelength is that the light source 112 that constitutes of the semiconductor laser of 400 to 650nm short wavelength lasers is towards CD 101 emission laser.The laser that sends from light source 112 drops on the cylindrical lens 113.
The laser that incides on the collimation lens 115 from cylindrical lens 113 is the shape of beam, and drops on the collimation lens 115 by polarization beam splitter 114.
If the thickness of the light-transmitting layer 103 of CD 101 is in predetermined value, laser will incide on the collimation lens 11 that is made of two spherical lenses that are bonded to together and be aligned.Collimation lens 115 is loaded on the driver of collimation lens 121, and can move forward and backward along the optical axis of incident laser.
If the thickness t of the light-transmitting layer 103 of CD 101 has broken away from predetermined value, just aim at collimation lens 115, so that proofread and correct because the spherical aberration that the thickness error of light-transmitting layer 103 causes with collimation lens 115.That is to say,, just incident laser is transformed into diverging light or converging light, so that proofread and correct because the spherical aberration that the thickness error of light-transmitting layer 103 causes with collimation lens 115 if the thickness t of the light-transmitting layer 103 of CD 101 has broken away from predetermined value.The laser that sends from collimation lens 115 drops on the diffractional lattice 116.
Become a three beams of laser after inciding the diffraction that laser on the diffractional lattice 116 is subjected to diffractional lattice 116.Diffractional lattice 116 is used to laser is resolved at least three light beams, so that carry out tracking servo control with so-called bikini method.The laser that penetrates from diffractional lattice 116 is turned to by light path lifting catoptron 117 on its working direction, drops on the quarter-wave plate 118.
The laser that incides on the quarter-wave plate 118 is become the circular polarisation state from linear polarization state.Drop on one group of two object lens 119 from the laser of quarter-wave plate 118 outputs.
Inciding one group of laser on two object lens 119 falls on the recording layer of CD 101 by light-transmitting layer 103 after being assembled.By two object lens 119a, two object lens 119 of this group that 119b constitutes are loaded on the twin shaft driver 111, and can move on the direction of optical axis and perpendicular direction.Become Returning beam after being fallen the reflection that incident laser on the recording layer of CD 101 is subjected to recording layer after being assembled by one group of two object lens 119, driven in the wrong direction by one group of two object lens 119 along the light path that advances then, and converge on the collimation lens 115.The converging light that produces is subjected to inciding on the photoelectric detector 120 after the reflection of polarization beam splitter 114, detects with photoelectric detector.
Referring to Fig. 9, second optical system 105 comprises a convergent lens 122, be used for assembling and be polarized beam splitter 114 laser light reflected, regulate photoelectric detector 123 with an output that is used for receiving the laser of assembling by convergent lens 122, so that regulate the output of the laser that sends from light source 112 automatically according to the light quantity that receives.
On the shaven head 100 of present embodiment, the object lens 109 of first optical system 104 and one group of two lens of second optical system 105 are loaded on the twin shaft driver 111, thereby it is moved on the direction of twin shaft, be used for realizing tracking Control and focus control CD 101.
Figure 10 and 11 has schematically shown the structure of a twin shaft driver 111.This twin shaft driver 111 comprises a drum 130 that is used for loading object lens 109 and one group of two object lens 119, and is used for an electromagnetic drive mechanism 131 of on two vertical direction mobile drum 130.
Referring to Figure 10 and 11, drum 130 is a cylinder with top board basically, and is supported on its center with a back shaft 132.Drum 130 supported rotate and slide around the axis of back shaft 132.Object lens 109 and one group of two object lens 119 are installed on the symmetric points of back shaft 132 both sides on the drum 130, allow optical axis each other be parallel to each other.
Referring to Figure 10 and 11, be used for the electromagnetic drive mechanism 131 of mobile drum 130 and comprise magnetic circuit, a pair of focusing yoke 134 with a focus magnet 133, follow the tracks of magnet 136, a pair of tracking yoke 137 for 135, one, 138, one focusing coils 139, and a tracking coil 140.
As shown in figure 11, fixedly mounting a metalwork 141, be used for setting the neutral position of drum 130 in tracking coil 141 inboards of electromagnetic drive mechanism 131.Because metalwork 141 is attracted towards the border of two magnetic poles of the tracking magnet 136 that is divided into two planar poles, drum 130 is set at tracking direction just on the neutral position of second direction, is set at focus direction simultaneously just on the neutral position of first direction.A neutral position supporting mechanism that utilizes elastic caoutchouc or the like to constitute remains on drum 130 on the neutral position of the supporting base 142 that back shaft 132 is housed.
Remain on drum 130 on the neutral position and be subjected to the driving of electromagnetic drive mechanism 131, its axis along back shaft 132 is slided, and rotate around the axis of back shaft 132.
That is to say that electromagnetic drive mechanism 131 makes drum 130 move along the axis of back shaft 132 according to the focus error signal that sends focusing coil 139 by flexible substrate 143 to.The focus control of along the slip of the axis of back shaft 132 one group of two object lens 119 being carried out with respect to CD 101 by drum 130.
On the other hand, electromagnetic drive mechanism 131 makes drum 130 rotate around the axis of back shaft 132 according to the tracking error signal that sends tracking coil 140 by flexible substrate 143 to.The tracking Control of around the rotation of the axis of back shaft 132 one group of two object lens 119 being carried out with respect to CD 101 by drum 130.
In above-mentioned shaven head 100, focus servo control and tracking servo control method so-called spherical aberration method and bikini method have been adopted respectively.Detect from CD by the cylindrical lens laser light reflected with the spherical aberration method by four sections photoelectric detectors, and calculate the detection output that obtains from each section and and/or poor, will therefrom derive focus error signal as the component that defocuses of laser with respect to recording layer.
The bikini method uses diffractional lattice will be separated into a main laser bundle (zero order beam) and two beamlets (± one-level light beam) from the single beam laser of light source, forward and backwardly sends two beamlets what be radiated at the supercentral main laser bundle of recording track.Detect folded light beam with photoelectric detector at the forward and backward beamlet that sends of main laser bundle with two light receivers, so that find out from the difference between the detection output of light receiver acquisition, therefrom derive tracking error signal, with it as the offset component of main beam with respect to recording track.
In order to duplicate with this bare headed 100 pairs of CDs 101, the thickness that first optical system 104 detects the light-transmitting layer 103 of CD 101 according to the recording layer and the light-transmitting layer 103 lip-deep focus error signals of CD 101.That is to say, the twin shaft driver 111 of first optical system 104 allows object lens 109 move forward and backward along optical axis under the driving of twin shaft driver 111, and first and second sigmoid curves that provided according to the translational speed and the focus error signal of object lens 109 detect the thickness of light-transmitting layer 103 by formula (11).
Thickness with first optical system, 104 detected light-transmitting layers 103 is to determine according to table that control circuit calculated and was scheduled to and the function do not represented among the figure.After the thickness of having determined light-transmitting layer 103, decide its mode of operation by this control circuit, be used for proofreading and correct because the spherical aberration that the thickness error of CD 101 causes, and will indicate the control signal of this operation to send to second optical system 105.Second optical system 105 is controlled the driver of collimation lens 121 according to these control signals, thereby collimation lens 115 is progressively moved, and reduces because the spherical aberration that the thickness error of light-transmitting layer 103 causes as far as possible.
After the spherical aberration that the thickness error to light-transmitting layer 103 causes was proofreaied and correct, 105 pairs of CDs of second optical system 101 were carried out as far as possible/replicate run.The driver of collimation lens 115 moves to its optimum position with collimation lens 115 according to the method, the spherical aberration that the thickness error of light-transmitting layer 103 causes is proofreaied and correct, thereby produce best signal.
During copy 101, the effect of first optical system 104 is optical systems that are used for detecting the operating distance in second optical system 105 in second optical system 105, just detects the interval between CD 101 and one group of two object lens 119.
In second optical system 105, carry out the focusing forward operation by move one group of two object lens 119 along optical axis, because the NA of one group of two object lens 119 is very big, it is very narrow focusing on Propulsion Range, and the operating distance between CD 101 and one group of two object lens 119 can not be greater than 0.5mm.Therefore, if there is surface deviation in CD 101, or the highly deviated of CD 101 reference value, CD 101 just may be run into one group of two object lens 119 during focusing on forward operation.
Therefore, second optical system 105 carry out focus on forward operations during, first optical system 104 can be used as a servicing unit, is used for preventing that CD 101 from running into one group of two object lens 119.
That is to say, second optical system 105 carry out focus on forward operations during, the laser radiation of sending from light source 106 and receives and the detection of focus error signal with photoelectric detector 110 on CD 101.According to this focus error signal just can detect be loaded in usually and drum that object lens 109 together use on the approximate location of one group of two object lens 119.According to the positional information by 104 detected one groups of two object lens 119 of first optical system, shaven head 100 drives twin shaft drivers 111, prevents that CD 101 from running into one group of two object lens 119.
Simultaneously, if one group of two object lens 119 have departed from the focusing Propulsion Range of first optical system 104 significantly, first optical system 104 may just can not produce focus error signal.Only detect from the entire emission of CD 101, and in the focusing Propulsion Range of first optical system 104, advance one group of two object lens 119 according to detected grade with first optical system 104.
Therefore, in this bare headed 100, first optical system 104 is used as one and is responsible for focusing on the auxiliary optics that advances, so that with second optical system, 105 copys 101, no matter CD 101 has does not have the surface or the deviation of height, can both realize that correct focusing advances, and can not allow one group of two object lens 119 run into CD 101.
First optical system 104 is used to focus on the subsidiary function or the operating distance detection method of propelling and also can uses the method except the spherical aberration method to realize, for example the differential concentric circle method.
Axis of reference 161 and secondary axis of reference 162 are mounted and are fixed on the stationary part of shaven head.Collimation lens support 163 supported and do sliding motion along optical axis with respect to these axis of reference 161,162.Be loaded on the collimation lens support 163 by moving the collimation lens of eliminating spherical aberration.By moving back and forth collimation lens support 163 along axis of reference 161,162, lens actuating device 160 makes the collimation lens that is loaded on the collimation lens support 163 move with respect to the reciprocal translation of optical axis direction.
Gearing 165 comprises a tooth bar 166 that is installed on the collimation lens support 163, be installed in first gear 167 on the turning axle of dc motor 164, be used for transmitting the rotary power of dc motor 164, one second gear 168, be used for converting rotatablely moving of dc motor 164 to translation motion along optical axis, and one the 3rd gear 169, the driving force that is used for being converted to by second gear 168 along the translation motion of optical axis is delivered on the tooth bar 166.
Come mobile collimation lens with this lens actuating device 160 if desired, just rotate dc motor 164 first gear 167 is rotated.The rotation of first gear 167 is passed to second gear 168, converts the translation motion along optical axis to.Converted to along the driving force of the translation motion of optical axis by second gear 168 and to pass to tooth bar 166 by the 3rd gear 169.
Utilize above-mentioned lens actuating device 160 that collimation lens is moved exactly.So just can eliminate the spherical aberration that the variation in thickness by light-transmitting layer causes fully with this lens actuating device 160.
In above-mentioned lens actuating device 160, dc motor 164 can adopt the stepper motor of a pulsed driven, and the distance that the rotation of each pulse is moved collimation lens is 13.8 μ m.If use this motor in the optical system in following example, for the variation in thickness of light-transmitting layer, the rotation of each pulse of dc motor to the correcting value of spherical aberration more than or equal to 0.2 μ m.The spherical aberration that produces with regard to the variation in thickness that is enough to proofread and correct owing to light-transmitting layer like this.
In addition, above-mentioned lens actuating device 160 is relatively simple for structure, and can reduced in size and cost.
Some most preferred embodiments of the optical system that has embodied shaven head of the present invention below will be described.
In the following description, the specific embodiment that comprises the optical system of lens is used for explaining how to come the correction of spherical aberration by mobile collimation lens.It should be noted that the thickness of the light-transmitting layer that the displacement of collimation lens or the numerical aperture NA of light outgoing one side that precision only depends on object lens and the distance layer that is located at CD are top, with the structure-irrelevant of object lens.Therefore, the concrete numerical value of the numerical aperture NA on light outgoing one side of object lens is given, but has omitted other lens data.
In addition, explained respectively in the following description and use bonding spherical lens as the example (example 1) of collimation lens with use the example (example 2) of surperficial phase type holographic lens as collimation lens.Yet, also can be with a kind of non-spherical lens or Fresnel lens as collimation lens.Also can use a kind of so-called volume phase formula holographic lens in addition.Example 1
Figure 14 represents a kind of optical system of present embodiment.Illustrated optical system represents to be used for the essential part in the optical system of shaven head of recording/copying CD 50, is provided with a recording layer on the substrate 50a surface of CD, also is provided with an x ray fluoroscopy x layer 50b on recording layer.Between light source and object lens 51, arranging 53, one collimation lenses 54 of 52, one polarization beam splitters of a diffractional lattice, and an aperture baffle plate 55.Collimation lens 54 is the spherical lenses with a bonding of first colourless lens 54a and second lens 54b formation.Lens 54a, 54b are spherical lenses.The numerical aperture NA of incident light one side is set at 0.14.
The lens data of in table 1, having represented this optical system.Lens data shown in the table 1 comprises an object lens face OBJ, the light entrance face s1 of diffractional lattice 52 and photoirradiated surface s2, the light entrance face s3 of polarization beam splitter 53 and light-emitting face s4, the light entrance face s5 of the first lens 54a of collimation lens 54, constitute the first and second lens 54a of collimation lens 54, the adhesive surface s6 of 54b, and the light-emitting face S7 of the second lens 54b of collimation lens 54.In table 1, s8 is an imaginary surface, and STO is an aperture baffle plate 55 that interrelates with object lens 51.
Table 1
| Surface number | Subsequent corrosion | From axially separating | Refractive index η d | Abbe number |
| OBJ | ∞ | 0.00000 | ||
| s1 | ∞ | 2.800000 | 1.51680 | 64.17 |
| s2 | ∞ | 10.130000 | ||
| s3 | ∞ | 2.200000 | 1.51680 | 64.17 |
| s4 | ∞ | 1.734906 | ||
| s5 | 22.03200 | 1.630000 | 1.78472 | 25.76 |
| s6 | 8.21300 | 2.100000 | 1.58267 | 46.47 |
| s7 | -11.74000 | 3.265094 | ||
| s8 | ∞ | 0.000000 | ||
| STO | ∞ | 0.000000 |
The thickness of supposing the x ray fluoroscopy x layer 50b of CD 50 is 0.1mm, and the numerical aperture NA of object lens 51 is 0.85, and the light wavelength λ that adopts is 635nm.Scale-up factor between the image of object and optical system is 0.1891.
Figure 15 is illustrated in the thickness error of the x ray fluoroscopy x layer 50b in the above-mentioned optical system and the relation between the wavefront aberration.Simultaneously, the standard deviation WFB on the emergent pupil face
RmsIn Figure 15, represent, and represent the light wavelength that adopted with λ with wavefront aberration.In addition, there is not mobile situation for collimation lens 54, just under the situation that spherical aberration does not obtain proofreading and correct, with dashed lines A1 and solid line A2 represent the thickness error of x ray fluoroscopy x layer 50b and the relation between the wavefront aberration in Figure 15, under the situation of mobile collimation lens 54, just under the situation of spherical aberration being proofreaied and correct according to the thickness error of x ray fluoroscopy x layer 50b, represent with a dotted line A3.
Referring to Figure 15, if x ray fluoroscopy x layer 50b do not have thickness error, the wavefront aberration in this optical system approximately is 0.003 λ.As can be seen from Fig. 15, if not mobile collimation lens 54, wavefront aberration will sharply increase.Yet if come mobile collimation lens 54 according to the thickness error of x ray fluoroscopy x layer 50b, the wavefront aberration that is produced by the thickness error of x ray fluoroscopy x layer 50b just can obtain obvious suppression.
Specifically, wavefront aberration is inhibited by mobile collimation lens 54, shown in following formula (12):
ΔL≈21Δt ...(12)
Even the thickness of x ray fluoroscopy x layer 50b changes, for example the thickness error of x ray fluoroscopy x layer 50b is in ± magnitude of 10 μ m, still wavefront aberration can be suppressed at and be not more than 0.01 λ.
In above-mentioned formula (12), Δ L is the amount of movement of collimation lens 54, and its positive dirction is the moving direction of collimation lens away from CD 50, and Δ t is the thickness error of x ray fluoroscopy x layer 50b.Example 2
Figure 16 represents a kind of optical system of present embodiment.Illustrated optical system represents to be used for the essential part in the optical system of shaven head of recording/copying CD 60, is provided with a recording layer on the substrate 60a surface of CD, also is provided with an x ray fluoroscopy x layer 60b on recording layer.Between light source and object lens 61, arranging a collimation lens 54 that constitutes by holographic lens, and an aperture baffle plate 63.
The lens data of in table 2, having represented this optical system.Lens data shown in the table 2 comprises an object lens face OBJ, the light entrance face s1 of collimation lens 62 and photoirradiated surface s2, and an imaginary surperficial s3.In addition, STO is an aperture baffle plate 63 that interrelates with object lens 61.
Table 2
| Surface number | The subsequent corrosion or the coefficient of phase function | From axially separating | Refractive index η d | Abbe number |
| OBJ | 14.000000 | |||
| s1 | C1：-3.5714E-02 C2：4.5549E-05 C3：-1.1354E-07 C4：0.0 | 1.000000 | 1.515014 | 64.17 |
| s2 | ∞ | 0.860000 | ||
| s3 | ∞ | 0.000000 | ||
| STO | ∞ | 0.000000 | ||
| Phase function: m=C1R 2+C2R 4+C3R 6+C4R 8 | ||||
The thickness of supposing the x ray fluoroscopy x layer 60b of CD 50 is 0.1mm, and the numerical aperture NA of object lens 61 is 0.85, and the light wavelength λ that adopts is 635nm.Scale-up factor between the image of object and optical system is 0.1891.
Simultaneously, collimation lens 62 is a kind of so-called surperficial phase type holographic lenses, is fit to according to the phase differential of incident light incident light to be carried out diffraction, equals 0.16 at the numerical aperture NA of incident light one side of lens.
The lens surface of collimation lens 62 carries out machine work, and incident light is produced phase differential.That is to say that the lens surface of collimation lens 62 carries out machine work, to the light generation phase differential of emission, thus the light of generation diffraction.In the optical system of present embodiment, the first order diffraction light that obtains by the diffraction on the collimation lens 62 drops on the object lens 61.
The characteristic of collimation lens 62 can be represented with following phase function formula (13):
M=C1R
2+ C2R
4+ C3R
6+ C4R
8... (13) m wherein represents the optical path difference under the reference diffraction wavelength.If when making collimation lens, suppose that two pointolites are the positions that are in the infinite distance, in above-mentioned formula (13), just can represent with the phase deviation in each surface of the collimation lens 62 of surperficial phase type holographic lens formation with on-chip polar coordinates polynomial expression.The collimation lens 62 that adopts in the present embodiment is a kind of holographic lenses, and phase function wherein is a kind of axisymmetric holographic lens.In above-mentioned formula (13), the distance that the R representative is counted from optical axis.In table 2, C1, C2, C3 and C4 represent the coefficient of phase function, and the reference diffraction wavelength of collimation lens 62 is set at 635nm.
In above-mentioned optical system, the thickness error of x ray fluoroscopy x layer 60b and the relation of wavefront aberration are as shown in figure 17, and be similar with Figure 16, the standard deviation WFE on the emergent pupil face of wavefront aberration
RmsBe to represent by the light wavelength of representing with λ.In Figure 17, move under the situation of collimation lens 62 at thickness error according to x ray fluoroscopy x layer 60b, solid line A4 represents the thickness error of x ray fluoroscopy x layer 60b and the relation between the wavefront aberration, with dashed lines A5 represents situation that wavefront aberration is proofreaied and correct.
Referring to Figure 17, if the x ray fluoroscopy x layer 60b of CD 60 do not have thickness error, the wavefront aberration in this optical system approximately is 0.003 λ.As can be seen from Fig. 17, if come mobile collimation lens 62, just can suppress the wavefront aberration that the thickness error owing to x ray fluoroscopy x layer 60b produces significantly according to the thickness error of x ray fluoroscopy x layer 60b.Specifically, if come mobile collimation lens 62 according to formula (14), wavefront aberration just can be suppressed:
Δ L ≈ 14 Δ t ... (14) irrelevant with the variation in thickness of x ray fluoroscopy x layer 60b.
In above formula (14), Δ L is the amount of movement of collimation lens 62, and its positive dirction is the moving direction of collimation lens, and Δ t is the thickness error of x ray fluoroscopy x layer 60b.
Simultaneously,, between lens, deviation might be produced, or tilt phenomenon might be on lens surface, occurred if move collimation lens according to the mode of example 1 or 2.This deviation or inclination can cause comatic aberration or spherical aberration.If comatic aberration or spherical aberration sharply increases, system will break down.Because the numerical aperture NA of incident light one side is very little on collimation lens, example 1 or 2 optical system are not easy to cause a deviation between lens or the inclination of lens surface.Specifically, the deviation of about 30 μ m or about 0.1 ° lens surface tilt can not throw into question to optical system in actual use, because comatic aberration or the spherical aberration of this moment are very little.
Claims (15)
1. a kind of shaven head that is used for carrier is used for having a light-transmitting layer above the recording layer of recording information signal on carrier, this shaven head comprises:
One is used for luminous light source;
Object lens, being used for will be from the optical convergence of above-mentioned light source to above-mentioned recording layer by above-mentioned light-transmitting layer;
Be arranged on a optical element between above-mentioned light source and the object lens with predetermined refraction; And
Move a mobile device of above-mentioned optical element according to the thickness of above-mentioned light-transmitting layer, this mobile device comprises:
One with the substantially parallel axis of reference of optical axis from the light of light source directive optical element;
The optical element bracing or strutting arrangement that is used for supporting above-mentioned optical element and can moves along above-mentioned axis of reference;
A motor; And
A gearing is used for converting the rotation of motor to be parallel to above-mentioned optical axis translation motion, and this translation motion is passed to above-mentioned optical element bracing or strutting arrangement;
Above-mentioned gearing converts the rotation of motor to be parallel to above-mentioned optical axis translation motion, is used for moving above-mentioned optical element bracing or strutting arrangement, and then above-mentioned optical element is moved, thereby eliminate spherical aberration according to the thickness of above-mentioned light-transmitting layer.
2. according to the shaven head of claim 1, it is characterized in that the optical element in the above-mentioned shaven head is a collimation lens.
3. according to the shaven head of claim 1, it is characterized in that the film thickness of above-mentioned light-transmitting layer is not more than 0.47mm, and the numerical aperture NA of above-mentioned object lens is not less than 0.65.
4. according to the shaven head of claim 1, it is characterized in that above-mentioned shaven head further comprises a twin shaft driver, be used on the direction of optical axis and perpendicular direction, moving above-mentioned object lens.
5. according to the shaven head of claim 4, it is characterized in that above-mentioned twin shaft driver is a drum, it can rotate around parallel with the optical axis of an object lens axle, and can slide along above-mentioned axle, and above-mentioned twin shaft driver can be used for supporting object lens.
6. according to the shaven head of claim 1, it is characterized in that above-mentioned twin shaft driver makes above-mentioned optical element move in the direction towards the spherical aberration that variation in thickness produced of eliminating light-transmitting layer on the direction of optical axis.
7. according to the shaven head of claim 1, it is characterized in that exporting Wavelength of Laser and be not more than 650nm.
8. one kind is write down and/or reproducing unit, is used for writing down and/or the Copy Info signal on a kind of recording layer of carrier, also has a light-transmitting layer on this recording medium, and this device comprises:
Be used for detecting the thickness detection apparatus of above-mentioned light-transmitting layer thickness; And
A shaven head that is used for carrier is used for having a light-transmitting layer above the recording layer of recording information signal on carrier, this shaven head comprises:
One is used for luminous light source;
Object lens, being used for will be from the optical convergence of above-mentioned light source to above-mentioned recording layer by above-mentioned light-transmitting layer;
Be arranged on a optical element between above-mentioned light source and the object lens with predetermined refraction; And
Move the mobile device of above-mentioned optical element according to the thickness of the detected above-mentioned light-transmitting layer of above-mentioned thickness detection apparatus, this mobile device comprises:
One with the substantially parallel axis of reference of optical axis that sends and fall the light on the optical element from light source;
The optical element bracing or strutting arrangement that is used for supporting above-mentioned optical element and can moves along above-mentioned axis of reference;
A motor; And
A gearing is used for converting the rotation of motor to be parallel to above-mentioned optical axis translation motion, and this translation motion is passed to above-mentioned optical element bracing or strutting arrangement;
Above-mentioned gearing converts the rotation of motor to be parallel to above-mentioned optical axis translation motion, is used for moving above-mentioned optical element bracing or strutting arrangement, and then above-mentioned optical element is moved, thereby eliminate spherical aberration according to the thickness of above-mentioned light-transmitting layer.
9. according to the record and/or the reproducing unit of claim 8, it is characterized in that above-mentioned optical element is a collimation lens.
10. according to the record and/or the reproducing unit of claim 8, it is characterized in that the film thickness of above-mentioned light-transmitting layer is not more than 0.47mm, and the numerical aperture NA of above-mentioned object lens is not less than 0.65.
11. according to the record and/or the reproducing unit of claim 8, it is characterized in that above-mentioned shaven head further comprises a twin shaft driver, be used on the direction of optical axis and perpendicular direction, moving above-mentioned object lens.
12. record and/or reproducing unit according to claim 11, it is characterized in that above-mentioned twin shaft driver is a drum, it can rotate around parallel with the optical axis of an object lens axle, and can slide along above-mentioned axle, and above-mentioned twin shaft driver can be used for supporting object lens.
13., it is characterized in that above-mentioned twin shaft driver makes above-mentioned optical element move in the direction towards the spherical aberration that variation in thickness produced of eliminating the x ray fluoroscopy x layer on the direction of optical axis according to the record and/or the reproducing unit of claim 8.
14., it is characterized in that exporting Wavelength of Laser and be not more than 650nm according to the record and/or the reproducing unit of claim 9.
15. a detection method that is used for detecting the light-transmitting layer thickness on the recording layer that is located at carrier is fit to recording information signal on above-mentioned recording layer, this method comprises:
From a light source luminescent;
The optical convergence that above-mentioned light source is sent with object lens is to above-mentioned carrier;
Receive the back light that converges on the above-mentioned carrier and reflect from above-mentioned carrier by above-mentioned object lens with a photoelectric detector that is used for the detection of focus error signal, and
Signal section in the above-mentioned focus error signal that produces according to the back light of the surface reflection of the back light of above-mentioned photoelectric detector reflection and above-mentioned light-transmitting layer detects the thickness of above-mentioned light-transmitting layer.
Applications Claiming Priority (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP348098 | 1998-01-09 | ||
| JP3480/1998 | 1998-01-09 | ||
| JP3480/98 | 1998-01-09 | ||
| US09/014,546 US5892050A (en) | 1998-01-28 | 1998-01-28 | Process for the preparation of pyridine dicarboxylate derivatives |
| JP159654/1998 | 1998-06-08 | ||
| JP159654/98 | 1998-06-08 | ||
| JP10159654A JPH11259893A (en) | 1998-01-09 | 1998-06-08 | Optical head, recording and/or reproducing device, recording and/or reproducing method, and thickness detecting method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1229231A CN1229231A (en) | 1999-09-22 |
| CN1118798C true CN1118798C (en) | 2003-08-20 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 99102974 Expired - Lifetime CN1118798C (en) | 1998-01-09 | 1999-01-09 | Optical head, recording and/or reproducing method and apparatus and method for detecting the thickness |
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|---|---|
| CN (1) | CN1118798C (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100657247B1 (en) | 1999-11-30 | 2006-12-19 | 삼성전자주식회사 | Objective lens for high density optical condensing and optical pickup apparatus employing it and optical disk |
| WO2003073152A1 (en) * | 2002-02-26 | 2003-09-04 | Matsushita Electric Industrial Co., Ltd. | Optical element and optical head device using it, and optical information device using this optical head device, and computer, optical disk player, car navigation system, optical disk recorder and optical disk server using this optical information device |
| US7254107B2 (en) | 2003-04-07 | 2007-08-07 | Matsushita Electric Industrial Co., Ltd. | Optical head and optical recording and reproducing apparatus |
| CN100401394C (en) * | 2004-12-06 | 2008-07-09 | 上海乐金广电电子有限公司 | Optical picking system |
| KR100675863B1 (en) * | 2005-01-24 | 2007-02-02 | 삼성전자주식회사 | Optical pick-up device |
| US7679846B2 (en) * | 2006-03-29 | 2010-03-16 | Mitsubishi Denki Kabushiki Kaisha | Lens driving device, optical pick up device and adjusting method |
-
1999
- 1999-01-09 CN CN 99102974 patent/CN1118798C/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| CN1229231A (en) | 1999-09-22 |
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