CN101140771A - Optical pick-up - Google Patents

Abstract

The present invention discloses an optical pick-up apparatus. In accordance with an embodiment of the present invention, a first diffraction element based on the property that a light beam in incidence at an optical disk is reflected and separated by a locus structure of the optical disk is adopted to remove the auxiliary light beams of AC ponderance, and a second diffraction element is used for preventing a light beam reflected from adjacent layers from being diffracted to an auxiliary unit used for receiving the auxiliary light beams. In this instance, the optical grating directions of the first diffraction element and the second diffraction element are regulated to remove the dead tract influence produced in tracing error signals and caused by the second diffraction element.

Description

Optical pick-up

Technical field

The present invention relates generally to optical pick-up, more specifically, relates to the optical pick-up that a kind of noise that can prevent to result from other layer flows to servosignal.

Background technology

CD (CD) is a kind of optical storage medium that can store nearly the data of 74 minutes audio frequency (music) or 650 megabyte, since it comes into the market, can keep the digital multi-purpose CD (DVD) of two hours other videos of single-definition (SD) level to obtain wide range of commercialization.In addition, in the near future, the Blu-ray Disc (BD) or high definition (HD) DVD that can store HD rank film will come into the market.

Optical storage medium such as CD, DVD and BD are the collar plate shape media, in these media, utilize optical property storage data, and data are recorded on the CD, perhaps will be recorded in data reproduction on the dish by optical pick-up.Optical storage medium comprises the disk that is used to reproduce that has write down data on it in advance, with the disk that is used to write down that can write or rewrite, but such as record/can rewrite (R/RW) CD, DVD-R/+R/-RW/+RW random access storage device (RAM) but but record/record-can rewrite (R/-RE) BD.

Optical pickup apparatus with the laser beam vernier focusing under the situation on the track of the CD of high speed rotating, data are recorded in that dish is gone up or reading of data from the CD.

For the corresponding servosignal of the site error that obtains and focus on the beam spot on the CD, such as focus error signal and tracking error signal, and for the site error of proofreading and correct beam spot according to this servosignal, also, in order to implement servo operation, optical pickup apparatus is embodied as arranges optics therein, such as object lens and beam splitter, mechanical part is such as actuator and pedestal, and electronic unit, such as laser diode and photodetector.

Which kind of type no matter be used for the dish of recoding/reproduction is, generally adopts Astigmatism methord to survey focus error signal.About the detection of the error signal that tracks, adopt 3 fluxs of light method or differential phase detection (DPD) method at the CD that is used for reproducing, and general what adopt is differential push-pull (DPP) method at the CD that is used for writing down.

Fig. 1 illustrates the principle of surveying tracking error signal based on the DPP method.

The DPP method is a kind of like this method, and its 1 light beam method of recommending to routine makes improvements, and can eliminate because object lens in radially the skew of moving or occurring owing to disc tilt, and can detect stable tracking error signal.

In the DPP method, by being known as the grating diffration element, will be divided into three beams from the laser beam that light source sends, also, 0 order diffraction light beam and+/-1 order diffraction light beam.Grating is controlled, so that when also promptly 0 order diffraction light beam is arranged in the groove of CD track with main beam, make side beam also be+/-1 order diffraction light beam is positioned at the bank (land) adjacent with which is provided with this groove of main beam and goes up (also promptly, side beam being arranged to separate with main beam the distance of one 1/2 track pitch).In addition, based on radially the left signal of each light beam and the differential signal of right signal detect tracking error signal.

From the main beam of CD reflection by 4 minutes (a, b, c, d) the key light electric explorer receives, and is detected as push-pull signal---promote mainly and draw (MPP) ((A+D)-(B+C)) signal.(E1, E2) (F1, F2) secondary photodetector received, and is detected as pair and recommends (SPP) ((E1-E2)+(F1-F2)) signal by 2 minutes from each side beam of CD reflection.When with side beam to be separated by the distance of 1/2 track pitch when arranging with main beam, MPP and SPP just become opposite each other, as shown in Figure 2.

Because skew all appears at same direction to MPP and SPP, therefore, according to object lens radially inclination or move, if utilize DPP=MPP-k * SPP (wherein k is a proportionality constant) to operate, so just can obtain does not have (offset-free) push-pull signal of skew.In addition, can obtain the more push-pull signal of large amplitude by from MPP, deducting the opposite SPP of phase place.

Usually, the ratio of light quantity that is used to produce the main beam of MPP signal in the DPP method and is used to produce the side beam of spp signal was made as about 1: 5: 1 to 1: 20: 1, is made as about 1/5 to 1/20 of main beam light quantity with light quantity with side beam.At the equation that is used for obtaining the DPP signal, resize ratio constant k (for example, when this light quantity ratio is 1: 10: 1, k being adjusted into 5), thus eliminate skew.

As mentioned above, in order to use the DPP method, in rotating grating, must the adjust side beam angle of---promptly+/-1 order diffraction light beam---.In this case, disadvantage is may the be adjusted influence of degree of the characteristic of signal.

Also promptly, in the time of on main beam being positioned at groove (perhaps bank), side beam must be positioned on the bank (perhaps groove).Yet, can differ from one another for the type track pitch of various CDs.For example, for DVD+RW or DVD-RW, track pitch (Tp), distance between its expression track is 0.74 μ m, and for DVD-RAM, the track pitch is 0.615 μ m, and it is difficult therefore the CD with different tracks pitch being imposed identical angle.

In addition, along with the development of BD or HD-DVD, increased for the needs of the optical disc recording/reproducing equipment that can reproduce or write down all types of CD, DVD and BD (perhaps HD-DVD).Yet owing to the numerical aperture that is the required object lens of recoding/reproduction CD, DVD and BD is very different each other, therefore, it almost is impossible only using single object lens to reproduce three kinds of all CDs.

Consider this needs, recently worked out such optical pickup apparatus, two kinds of object lens wherein are housed on actuator, also promptly be used for the object lens and the object lens that are used for BD or HD-DVD of CD/DVD.These two kinds of object lens can be arranged along the direction (tangentially) of CD track or the inside/outside circumferencial direction (radially) of CD.When object lens are radially arranged, be not easy to the innermost circumference of access CD, thereby, worked out wherein two kinds of optical pickup apparatus that object lens are arranged along trajectory direction now.

Fig. 3 illustrates an example, and one of them object lens deviates from the central shaft of CD, and two object lens on will being installed in single actuator make it arrange from axle when trajectory direction is arranged.

As shown in Figure 3, when with two object lens when trajectory direction is arranged, at least one in two object lens deviates from and is used to connect the inner periphery of CD and that axle of excircle (by the axle of cd centre).In the optical system of using this position that object lens is located at the central shaft that deviates from CD, owing to the relative position (angle of side beam) that the DPP of track is detected required main beam and side beam changes along with optical pickup apparatus moves to excircle from the inner periphery of CD, so the adjustment of the angle of side beam is just nonsensical.

Meanwhile, in standard, adopt sandwich construction, in this sandwich construction, formed two or more recording layers for increasing memory capacity at DVD and BD.In addition, even for the high density compact disc that will develop in the future, also wish generally to adopt sandwich construction.

In order to increase the density of CD, the numerical aperture (NA) that shorten the wavelength of laser beam and increase object lens gradually.For the situation of CD, use wavelength to be the laser diode of 780nm and the object lens of NA=0.45.For the situation of DVD, use wavelength to be the laser diode of 650nm and the object lens of NA=0.6.For the situation of BD, use wavelength to be the laser diode of 405nm and the object lens of NA=0.85.

In multiplayer optical disk, the spacing between the recording layer is defined as being approximated to direct ratio with the depth of focus of beam spot.Since depth of focus is directly proportional with the wavelength of laser beam and with square being inversely proportional to of the NA of object lens, so the spacing between the recording layer must reduce along with the increase of recording density.

When the short multiplayer optical disk of the spacing between layer and the layer is implemented record or reproduced operation,, also, flow to photodetector easily, as shown in Figure 4 promptly from the noise light of another layer from the layer beam reflected adjacent with the current record layer.

Also flow to from the noise light of another layer and to be used to receive the key light electric explorer of main beam and be used to receive the secondary photodetector of side beam, thereby influence the signal of servosignal and reproduction.Especially, utilize the less servosignal that side beam obtained of light quantity to be subjected to greatly to influence.

Shown in Fig. 5 A and 5B, there is a problem to be, owing to, cause the spp signal excessive distortion, and, also be that tracking error signal produces deterioration based on the DPP signal that spp signal calculates from the cause of the noise light of another layer.Also be, when reproducing or record when having the CD of two or more recording layers, because from another layer beam reflected, cause in reproducing signal and servosignal, noise occurring, shown in Figure 4 and 5, and thereby reproduction or record performance can sometimes can not be finished record because of the noise deterioration.

Summary of the invention

Thereby, the present invention considers the problems referred to above that occur in the prior art, an object of the present invention is to provide a kind of optical pick-up, it has reduced the interlayer interference (interlayer interference) in the multiplayer optical disk interlayer, thereby obtains stable servosignal and improved the performance of reproducing or writing down.

Another object of the present invention provides the device of variation of the position of the side beam that the variation of the focal length (magnification) of a kind of variation of the pitch that effectively tackles correction because of the moving of interlayer, spherical aberration, diffraction element or lens causes.

According to an aspect of the present invention,, the invention provides a kind of optical pick-up, comprise being used to launch light source with light beams of predetermined wavelengths for realizing top purpose; Be used for to focus on from the light beam that this light source sends the object lens on the optical storage medium; Be used to make the light beam that sends from light source or from this optical storage medium beam reflected by or the beam splitter of reflection; First diffraction element, be used for from produce through this optical storage medium beam reflected not with track at this optical storage medium on second light beam of the corresponding component in position that focuses on the light beam on this optical storage medium; Second diffraction element; Sensor leads is used for producing astigmatism from the optical storage medium beam reflected; And Electro-Optical Sensor Set, it comprises being used to receive not and changes ground by the main sniffer of first light beam of first and second diffraction elements and two first secondary sniffers that are used to receive second light beam; Wherein second diffraction element will be from except when the part diffraction other layer beam reflected beyond the anterior layer of the optical storage medium of preceding executive logging thereon or reproduction, thereby the light beam that prevents this diffraction incides on the Electro-Optical Sensor Set.

In an embodiment of the present invention, first diffraction element comprises incident beam that is used for a diffraction part and the first area that produces second light beam, and this first area does not comprise such zone, promptly, wherein from this optical storage medium beam reflected, in by this optical storage medium diffraction and separation, by the light beam of this optical storage medium diffraction and not by the light beam of this optical storage medium diffraction in zone that they overlap each other during by first diffraction element.

In this embodiment, the first area can be formed rectangular shape, it has such zone as the border, in this zone, from this optical storage medium beam reflected those by the light beam of this optical storage medium diffraction by first diffraction element, perhaps can comprise be arranged in be used for being connected by this optical storage medium beam reflected by the light beam of this optical storage medium diffraction and not by the light beam of this optical storage medium diffraction when by first diffraction element above crossing four somes the zone above 2 the straight line be arranged in the straight line that is used to be connected below these four points at 2 below the zone.

The first area can comprise such grating, it forms and makes this a part of incident beam diffracted by the vertical direction of the direction of this optical storage medium diffraction with light beam, perhaps can comprise such grating, it forms and makes that this incident beam of a part is diffracted by the direction of this optical storage medium diffraction at light beam.

In one embodiment of the invention, second diffraction element comprises the 3rd zone of the incident beam that is used for a diffraction part, and the 3rd zone is corresponding to regionally such, promptly, in this zone, the light beam that focuses on from described other layer beam reflected on this Electro-Optical Sensor Set passes through second diffraction element.

In this embodiment, the first area can comprise such grating, its form to make a part this incident beam with the light beam direction parallel or vertical by the direction of this optical storage medium diffraction on diffracted.First area and the 3rd zone can have the grating orientation that forms the right angle.

Second diffraction element can wherein be passed through at those light beams that focus on the first secondary sniffer from described other layer beam reflected corresponding to such zone in the 3rd zone.

In one embodiment of the invention, each first secondary sniffer can be located in that those have not passed through outside the effective radius of the light beam of first diffraction element and second diffraction element with changing from described other layer beam reflected.In this case, second diffraction element is wherein passed through at those light beams that focus on the first secondary sniffer from described other layer beam reflected corresponding to such zone in the 3rd zone.

In this embodiment, the first area can comprise such grating, its form to make a part this incident beam with light beam by the parallel or vertical direction of the direction of this optical storage medium diffraction and diffracted, and wherein first area and the 3rd zone can have the grating orientation that forms the right angle.

Each first secondary sniffer can have the width wideer than the width of main sniffer.Each first secondary sniffer can be located at the position that deviates from this main sniffer according to the focus direction and the focal length of this sensor leads, perhaps can be divided, to obtain push-pull signal by the border surface that forms with the angle that straight line limited that is used to connect the first secondary sniffer and this main sniffer.

This optical pick-up can also comprise the beam diffraction that is used for sending from this light source become 0 grade of light beam and+/-1 grade of light beam and the light beam of this diffraction focused on grating on this optical storage medium, and wherein this Electro-Optical Sensor Set also comprise be used to receive from this optical storage medium reflection+two second secondary sniffers of/-1 grade of light beam.The first secondary sniffer and the distance of this main sniffer between them can be 5 times or bigger multiple of distance between the second secondary sniffer and this main sniffer.

In this embodiment, first diffraction element and second diffraction element can be integrated into individual devices.

In this embodiment, first diffraction element can be inserted between this beam splitter and this object lens, between this beam splitter and this sensor leads or between this sensor leads and this Electro-Optical Sensor Set.In addition, when first diffraction element was inserted between this beam splitter and this object lens, this optical pick-up can also comprise that being used between first diffraction element and this object lens makes the quarter wave plate of the polarization rotation of light beam.

In this embodiment, second diffraction element can be inserted between this beam splitter and this object lens, between this beam splitter and this sensor leads or between this sensor leads and this Electro-Optical Sensor Set.When first or second diffraction element is inserted between this beam splitter and this object lens, first or second diffraction element only diffraction from this optical storage medium beam reflected, and the light beam that sends from this light source of diffraction not.To this operation, first or second diffraction element can adopt liquid crystal manufacturing.

In one embodiment of the invention, tracking error signal can be surveyed by Mpp-k (Spp1+Spp2), and the variation of the skew of the variation of the skew of k this Mpp that can cause based on the radial displacement because of these object lens and Spp1 and Spp2 is calculated.

Description of drawings

From the detailed description of carrying out below in conjunction with accompanying drawing, above-mentioned and other purpose, feature and other the advantage that the present invention may be better understood.In the accompanying drawings:

Fig. 1 illustrates the principle that detects tracking error signal based on the DPP method;

Fig. 2 illustrates the push-pull signal that produces based on 3 light beam DPP methods;

Fig. 3 illustrates an example, and wherein the object lens when trajectory direction is arranged of two object lens on will being installed in single actuator deviate from the central shaft of CD and it is arranged from axle;

Fig. 4 illustrates the state that flows to photodetector from the noise light of another layer reflection;

Fig. 5 A and 5B illustrate an example, and wherein tracking error signal is because of the interlayer interference distortion in the CD with two or more recording layers;

The skew that Fig. 6 illustrates DPP signal wherein the intersection of record/non-posting field increase and with objective lens arrangement for from axle and the phenomenon of the interval prolongation of the generation of this skew when adopting 3 light beam DPP methods;

Fig. 7 A is to be used for summarily representing 3 light beam DPP methods and 1 light beam DPP method figure relatively to 7C;

Fig. 8 is illustrated in the embodiment of the optical pick-up of wherein using 1 light beam DPP method;

Fig. 9 is illustrated in another embodiment of the optical pick-up of wherein using 1 light beam DPP method;

Figure 10 illustrates the shape that separation takes place the light beam that wherein incides on the CD that is used to write down;

Figure 11 exemplarily is illustrated in the baseball pattern that forms when the light beam that incides on the CD that is used to write down takes place to separate;

Figure 12 is schematically illustrated from removed the principle of the side beam of AC component by acquisition the light beam of CD reflection and separation;

Figure 13 A illustrates several embodiment of the diffraction grating of the side beam that has been used to obtain to remove the AC component to 13C;

Figure 14 is illustrated in diffraction grating by Figure 12 and has removed the AC component from the push-pull signal of side beam, only stayed the result of DC component;

Figure 15 A and 15B illustrate when to CD with two-layer or multilayer when anterior layer writes down or reproduces, incide example on the photodetector integrated circuit (PDIC) from another layer beam reflected;

Figure 16 A and 16B illustrate and are used to remove the diffraction grating of interlayer interference and the beam distribution on the PD according to the embodiment of the invention;

Figure 17 A and 17B are illustrated in the layout that is used for the unit of main beam in the light receiving element according to the embodiment of Figure 16 and is used for the unit of side beam;

Figure 18 A is the light beam that is used for being presented at through the diffraction grating diffraction of Figure 16 A to 18C, as the figure of the mutually different example of shape of the side beam of the side beam of anterior layer and another layer;

Figure 19 A and 19B illustrate the diffraction grating and the upward distribution of light beam of PD that are used to remove interlayer interference according to another embodiment of the present invention;

Figure 20 A and 20B are illustrated in the example of the layout of the unit that is used for the unit of main beam in the light receiving element according to the embodiment of Figure 19 and is used for side beam;

Figure 21 A and 21B illustrate other example according to the layout of the unit that is used for side beam of the embodiment of Figure 19;

Figure 22 A shows the distribution of light beam on the shape of DOE when adopting 3 light beam DPP methods and position and the PD to 22C;

Figure 23 A is illustrated in the multiple shape of the DOE that is used to remove interlayer interference when adopting typical 3 light beam DPP methods to 23C;

The distribution that the shape of DOE and position and PD went up light beam when Figure 24 A was illustrated in the 1 light beam DPP method of employing to 24C;

Figure 25 is illustrated in the 1 light beam DPP method, when under the radially non-wiping state of object lens, when side beam is located at the center of pair unit, according to the variation of the skew of the tracking error signal of the radial displacement of object lens;

Figure 26 is illustrated in the 1 light beam DPP method, when under the radially non-wiping state of object lens, when side beam not being located at the center of pair unit, according to the variation of the skew of the tracking error signal of the radial displacement of object lens;

Figure 27 A and 27B illustrate the embodiment that makes at the position change of PDIC side beam by the DOE that removes interlayer interference in conjunction with the grating and being used to that is used for 1 light beam DPP method;

Figure 28 A and 28B illustrate among each embodiment the moving direction of side beam in the pair unit, in these embodiments, by in conjunction with the grating that is used for 1 light beam DPP method and the DOE that is used to remove interlayer interference make position change at the PDIC side beam;

Figure 29 A to 29C illustrate different shape be used to remove the DOE of interlayer interference and be used for the example that the diffraction grating of 1 light beam DPP method is realized in a plane;

Figure 30 A illustrates the example of the enforcement of the diffraction direction and the grating orientation of diffraction grating and the type HOE that glitters to 30C; And

Figure 31 illustrates the main structure of use according to the data recording/reproducing device of optical pick-up of the present invention.

Embodiment

Specifically describe embodiments of the invention hereinafter with reference to accompanying drawing.

In using the DPP method of 3 light beams, in that being separated by, side beam and main beam it is focused on the CD in the 1/2 track pitch.In this typical situation, the relative position of main beam and side beam can not change because of the inner periphery and the excircle of CD on the central shaft that object lens is located at CD.

Yet, deviate from the central shaft of CD and work this for object lens wherein from situation that axle is arranged, as shown in Figure 3, the relative position of main beam and side beam changes according to the inside/outside circumference of CD on the CD track.In this case, exist a problem to be, as shown in Figure 6, at the intersection of the record/non-posting field of CD, the skew of DPP signal has increased, and occur skew during elongated.

Difference between record and the non-posting field is represented with the difference of their reflectivity.In 3 light beam DPP methods, when object lens are mobile on record/non-posting field, be created on level (level) poor of each region generating DPP signal.

When using 3 light beams,, produce the skew of DPP signal at the intersection of record/non-posting field because of light beam enters the poor of used time of record/non-posting field.In order to address this problem, applicant of the present invention proposes a kind of method, it also is so-called 1 light beam DPP method, this method only makes, and single beam incides on the CD, light beam is separated and reflection through the track configuration of CD, so that by predetermined diffraction grating and produce main beam and side beam, and utilize this side beam to eliminate skew from the push-pull signal of main beam.This method is described below.

Fig. 7 A illustrates the comparable situation of 3 light beam DPP methods and 1 light beam DPP method to 7C.In 3 light beam DPP methods, the light beam that sends from laser diode (LD) is divided into three beams by grating, and this three-beam incides on the CD and reflects thereon, and the three-beam of reflection focuses on the master unit and pair unit of photodetector (PD).In contrast, in 1 light beam DPP method, only single beam incides on the CD and from this CD reflection, separate simultaneously through the track configuration of this CD, and beam reflected forms main beam and two side beams of having removed the AC component by predetermined diffraction grating, and main beam and side beam focus on the master unit and pair unit of PD.

The fundamental purpose of using side beam in the DPP method is to eliminate the skew that produces in main beam that the radial displacement because of object lens causes, and thereby can obtain quadratic effect, such as the increase of the DPP signal level that causes because of the AC component that in the push-pull signal of side beam, produces.

In this method that the present patent application people is proposed, track configuration (playing the bank/groove of the track of diffraction grating function) reflection through CD is passed through diffraction grating with the light beam that separates, and the formation main beam, the light beam that has the pattern institute diffraction of reservation shape in diffraction grating forms side beam.

Because the main beam that forms by diffraction grating has comprised the AC component---its reflection focuses on the position of light beam on track on the CD, therefore and DC component---the amount of the radial displacement of its reflection object lens has comprised AC component and two kinds of components of DC component in the push-pull signal of main beam.

The pattern of diffraction grating has such shape, its allow these by in the reflection of the track configuration of CD and the light beam that separates only corresponding to the light beam of DC component (skew) rather than diffracted corresponding to the light beam of AC component.Therefore, in by the push-pull signal of the side beam that this pattern reflected and produced, only comprised the DC component.

Therefore, can utilize the push-pull signal of side beam and effectively eliminate corresponding to the radial displacement of object lens skew---it is contained in and does not change in the push-pull signal of ground by the main beam of diffraction grating.

In addition, as mentioned above, in 3 light beam DPP methods of routine, there is three-beam to incide on the CD, in the tracking error signal that the difference that enters record and time of non-posting field because of three-beam causes, mistake can occurs.Yet, in 1 light beam DPP method, owing to only have a branch of light to incide on the CD, therefore, even also can obtain stable tracking error signal at the intersection of record/non-posting field.

Fig. 8 illustrates the structure of it being used the optical pick-up of 1 light beam DPP method.

Optical pick-up among Fig. 8 comprises light source 110, collimation lens 120, beam splitter 130, diffraction grating 140, quarter wave plate (QWP) 160, object lens 170, sensor leads 180, and Electro-Optical Sensor Set (perhaps photodetector: PD) 190.That side of the focus of CD formation object lens 170 mounted thereto.

Light source 110 emission of lasering beam, collimation lens 120 will become collimated light from the light beam of light source.In the present invention, light source 110 and collimation lens 120a can be combined into single luminescence unit.In addition, when will in optical system, using the scattered light that sends from light source without change, rather than collimated light, can save collimation lens 120 so.Beam splitter 130 as beam splitting mean sees through incident light according to the polarization of incident light direction, makes it towards diffraction grating 140, and will reflect towards sensor leads 170 from the light beam of CD reflection.

The linearly polarized photon that is used to make the quarter wave plate 160 of the polarization rotation of light beam to send from light source 110, P polarized light for example, convert circularly polarized light to, and will come from CD reflection, become another kind of linearly polarized photon as the Beam Transformation of another kind of circularly polarized light, S polarized light for example.

Focus on light beam on the CD through object lens 170, through having the CD reflection and the diffraction of bank/groove structure, convert 0 grade of light beam and+1 grade of light beam then to, they are once more towards object lens 170 incidents.The circularly polarized light that comes from CD reflection converts collimated light to through object lens 170, and this collimated light becomes linearly polarized photon in by quarter wave plate 160.For from CD reflection and incide on the sensor leads 180 light beam that its light path simultaneously changes by beam splitter 130, sensor leads 180 produces astigmatisms, and the light beam that has astigmatism is transmitted on the Electro-Optical Sensor Set 190.

In diffraction grating 140, form grating pattern so that at light beam in the circular pattern of the produced simultaneously diffracted beam of CD reflection and separation, the zone that the circular pattern of the circular pattern of ± 1 grade of light beam and 0 grade of light beam overlaps each other, the PD unit that is not used for pair unit in the Electro-Optical Sensor Set 190 receives.

Also promptly, forming main beam and side beam through the light beam that CD separates and reflex time forms by diffraction grating 140.Main beam is by diffraction grating 140 with changing, also is that light receiving element receives by the master unit of Electro-Optical Sensor Set 190, and is detected as main beam and recommends (MPP) signal.Two side beams that produce when in by diffraction grating 140, having the pattern diffraction of reservation shape, pair unit through Electro-Optical Sensor Set 190 receives, and then its detection is recommended (SPP) signal (SPP1) and second spp signal (SPP2) as first side beam.

In order to detect MPP signal and spp signal, respectively corresponding to radially being divided into two parts at least with tangential direction, and each pair unit that makes Electro-Optical Sensor Set 190 is being divided into two parts at least corresponding to radially direction with the master unit of Electro-Optical Sensor Set 190.

Fig. 9 illustrates the another kind structure of it being used the optical pick-up of 1 light beam DPP method.Optical pick-up 200 among Fig. 9 comprises light source 210, collimation lens 220, beam splitter 230, diffraction grating 240, object lens 270, sensor leads 280 and Electro-Optical Sensor Set 290.Be installed on it that side of the focus that forms object lens 270 of CD.

Optical pick-up 200 among Fig. 9 have with above-mentioned Fig. 8 in the similar structure of optical pick-up 100, difference between them is that Fig. 9 does not provide the quarter wave plate 150 of the optical pick-up 100 among Fig. 8, and diffraction grating 240 is located between beam splitter 230 and the sensor leads 280.Except this difference, the structure of the optical pick-up 200 among Fig. 9 and operation all with Fig. 8 in optical pick-up 100 identical.

The shape of separation takes place in the schematically illustrated light beam that wherein incides on the CD that is used to write down of Figure 10.

When from the focus of object lens, incide light beam on the CD that is used to write down be divided in CD reflection through object lens+1 grade of light beam, 0 grade of light beam and-1 grade of light beam, form predetermined angle (θ) simultaneously, as shown in figure 10.This is that therefore the bank and the groove of the CD that is used to write down have protruding/concave portion because the track configuration (bank/groove) of the CD that is used to write down has projected path pitch (TP), and therefore produces and the similar effect of diffraction grating.

0 grade of light beam (b2) ,+1 grade of light beam (b1) and-1 grade of light beam (b3), they form circular pattern through CD reflection and separation, and propagate towards object lens.The entrance pupil diameter (EPD) of the size of the circular pattern of light beam and object lens measure-alike.When the focal length of object lens is f and numerical aperture when being NA, EPD is 2 * f * NA.

In addition, as shown in figure 10 ,+1 grade of light beam (b1) and-1 grade of light beam (b3) move to the left side or the right.When the track pitch of CD is the wavelength of Tp and laser beam when being λ, amount of movement is f * λ/Tp.

The circular pattern P2 that is arranged in 0 grade of light beam of central authorities forms the pattern of Figure 11, because it with since the track configuration of CD and to the left side or the right move+1 grade and the circular pattern P1 of-1 grade of light beam and overlapping of circular pattern P3, (this is illustrated in light beam through the CD diffraction by the state before the object lens).This circular pattern is called baseball pattern, because it is similar to the shape of baseball.

In this case, the size of circular pattern P1, P2 and P3 and overlapping degree differ from one another according to the type of CD.For BD or DVD-RW, because amount of movement is big, so overlapping degree is low relatively, forms the pattern among Figure 10 thus.The AC component of push-pull signal (, being MPP and spp signal) for 3 light beam DPP methods by 0 grade of light beam in the baseball pattern in Figure 11 and+that part of (shadow region) that/-1 grade of light beam overlaps each other produce.

Figure 12 is schematically illustrated from removed the principle of the side beam of AC component by acquisition the light beam of CD reflection and separation.

The light beam that incides CD is diffracted into three light beams through the track configuration of CD.The central light beam of these three diffracted beams is defined as 0 grade of light beam, and the light beam that will be formed at 0 grade of light beam left side and the right is defined as+/-1 grade of light beam.These three light beams that come out from the beam separation that incides CD (0 grade light beam and+/-1 grade of light beam) overlap each other at some zone (P7), thereby form baseball pattern.

The pattern of the diffraction grating of the embodiment of conduct shown in Figure 12 is designed to only 0 grade of light beam of diffraction (P5), and not in the diffraction baseball pattern 0 grade of light beam and+/-1 grade of zone that light beam overlaps each other, thereby the photodetector that allows to be used for side beam receives diffracted beam, and thereby prevent to be used for photodetector reception+/-1 grade of light beam (P4, P6 and P7) of side beam, comprise wherein 0 grade of light beam and+that/-1 grade of light beam overlaps each other is that part of.

Yet, change ground by the formed main beam of diffraction grating, irrespectively reflected baseball pattern with the pattern of diffraction grating, and thereby focused on the master unit of light receiving element.Thereby, in the push-pull signal (MPP) of main beam, comprised AC component and DC component the two.

Except that 0 grade of light beam in baseball pattern and+the diffraction pattern diffraction of 0 grade of light beam (P5) through representing of the part of/-1 grade of light beam overlapping each other with dash area, and receive by the photodetector that is used for side beam (pair unit).Thereby, in the push-pull signal (SPP) of side beam, only comprise the skew (DC component) rather than the AC component of main beam.

Therefore, the push-pull signal that has removed the side beam of AC component is deducted from the push-pull signal (MPP) of main beam, and thereby can need not by using three light beams to be focused on the trajectory error signal that 3 beam method on the CD obtain to eliminate skew.

Figure 13 A illustrates several embodiment of the diffraction grating of the side beam that has been used to obtain to remove the AC component to 13C.This diffraction grating can form the pattern with different shape.

As mentioned above, the main beam that forms to the diffraction grating among the 13C by Figure 13 A has not reflected whole baseball pattern with changing, and thereby has comprised the AC component and be offset the two in the MPP signal.Yet, only using the zone corresponding first pattern A1, A3 and A5 diffraction by some zone quilt and diffraction grating in the light beam of CD reflection and separation, thereby the formation side beam.

When the hypothesis X-axis is an inside/outside circumferencial direction (radially) and when supposing that Y-axis is trajectory direction (perhaps tangential), the diffraction grating among Figure 13 A comprises the first pattern A1 that the hourglass shape (" I " shape) with standing upright forms and at the regional formed second pattern A2 except that the first pattern A.

The first pattern A1 is formed at the zone except that the circular pattern of ± 1 grade of light beam b1 and b3 (P1 among Figure 11 and P3), also promptly, except that wherein the circular pattern zone of 0 grade of light beam b2 (P2 among Figure 11) and ± zone (P7 among Figure 12) and the regional P4 among Figure 12 and the zone the P6 (P5 among Figure 12) that the circular pattern (P1 and P3) of 1 grade of light beam b1 and b3 overlaps each other.

In addition, the first pattern A1 on/lower end (rectangle part except that the central, circular recess) can not invade ± extend to the both sides of diffraction grating in the circular pattern zone P4 of 1 grade of light beam b1 and b3 and the scope of P6.

Diffraction grating among Figure 13 B is formed first pattern A3 of the vertical long rectangular shape that is included in middle body formation and the second pattern A4 that forms on the left side and the right of the first pattern A3.For this situation, the position of the first pattern A3 and width are important factors.The first pattern A3 has and does not comprise ± 1 grade of light beam b1 and the circular pattern P1 of b3 and the rectangular shape of P3.Also promptly, preferably, determine position and the width of the first pattern A3 on the x direction so that the both sides of the first pattern A3 all with the circular pattern P2 that is positioned at 0 grade of light beam ± the circular pattern P1 of 1 grade of light beam and the edge contact of P3.

Diffraction grating among Figure 13 C is included in second pattern A6 of the long rectangular shape of level that middle body forms and the first pattern A5 that forms up and down at the second pattern A6.For this situation, preferably, by in four points of the boundary-intersected of the circular pattern P1 of the border of the circular pattern P2 of 0 grade of light beam b2 and ± 1 grade of light beam b1 and b3 and P3, connect top and following straight line respectively at 2 at 2, determine position and the width of the first pattern A5 on the y direction.

Figure 14 illustrates by Figure 13 A and has removed the AC component from the push-pull signal of side beam, only stayed the result of DC component to the diffraction grating of 13C.Can find out that from Figure 14 the push-pull signal of main beam (MPP) is not subjected to the influence of diffraction grating, and has removed the AC component from the push-pull signal (SPP) of side beam.

From the push-pull signal (SPP) of side beam, remove the AC component and mean the phase change of having eliminated in the AC component that the variation because of the track pitch causes (phase variation), therefore, the problem that occurs can achieve a solution arranging from axle because of object lens---state that its expression object lens depart from from central shaft---.

In this case, the amount of movement of the DC level (skew) of spp signal and object lens also is that radial displacement (its expression object lens moving from the center of actuator to the inside/outside circumference of CD) is closely related.

Usually, be directly proportional, therefore can think that the skew of push-pull signal has linear behavio(u)r, be that it is directly proportional with the radial displacement of object lens because the skew (DC level) of MPP signal and spp signal is increased in to a certain extent with the increase of the radial displacement of object lens.

Therefore, when the variation of the DC level (slope) of hypothesis MPP signal is a with respect to the radial displacement of object lens, when the variation of the DC level of spp signal is b with respect to the radial displacement of object lens, can passes through proportionality constant k=1/2b among the equation DPP=MPP-k * (SPP1+SPP2) and eliminate skew because of the MPP signal of the mobile generation of object lens.

In CD with two-layer or multilayer, form semitransparent layer reproducing data from another recording layer, and for various CD transmissivity differences.Shown in Figure 15 A and 15B, when supposing that the recording layer near the CD plane of incidence is L1, and when being L0 away from the recording layer of this plane of incidence, Figure 15 A is illustrated in layer L1 identifying recording layer and reproduces the situation of data from layer L1, and Figure 15 B is illustrated in layer L0 identifying recording layer and reproduce the situation of data from layer L0.

Figure 15 A and 15B are illustrated under the situation of the position that does not change CD and photodetector integrated circuit (PDIC), the situation that the interlayer of implementing according to the variation of its position of object lens that constitutes optical system moves.In Figure 15 A, from being different from the current front that the light when the layer L0 of anterior layer L1 reflection that reproduces or write down focuses on PDIC of carrying out thereon.In Figure 15 B, focus on the back of PDIC from the light of layer L1 reflection.

The influence of noise on double-layer CD that Fig. 5 A and 5B illustrate that factor value limited aperture (limiting) method causes.Fig. 5 A illustrates the situation of single-layer optical disc, and Fig. 5 B illustrates the situation of double-layer CD, and it shows the not influence of MPP signal, but has comprised a large amount of noises in spp signal, and thereby causes the DPP distorted signals.

Also promptly, because of from the interference between the side beam of the light beam of other layer output and reproducing signal, noise appears in spp signal.Therefore, flow to side beam zone (perhaps until the main beam zone), also promptly be used for receiving the pair unit of side beam, just can prevent the deterioration of the DPP signal that causes because of interlayer interference if can stop from the light beam of other layer output.

Analysis to this process is described below.The light beam (also being sub1 (E1/E2) and the sub2 (F1/F2) among Fig. 1) that focuses on the pair unit when hypothesis is ψ _{Sub ,+1}And ψ _{Sub ,-1}, by the amount of following equation definition light beam and light beam:

ψ _sub，+1＝ψ _0，+1+ψ _1，0+ψ _1，+1+ψ _1，-1

I _sub，+1＝|ψ _0，+1| ²+|ψ _1，0| ²+|ψ _1，+1| ²+|ψ _1，-1| ²

+2V ₀[|ψ _1，0||ψ _1，+1|cos(φ _1，0-φ _1，+1)+|ψ _1，0||ψ _1，-1|cos(φ _1，0-φ _1，-1)

+|ψ ₁₊₁||ψ _1，-1|cos(φ _1，+1-φ _1，-1)]+2V ₀₁[|ψ _0，+1||ψ _1，0|cos(φ _0，+1-φ _1，0)

+|ψ _0，+1||ψ _1，1|cos(φ _0，+1-φ _1，+1)+|ψ _0，+1||ψ _1，-1|cos(φ _0，+1-φ _1，-1)]

In this case, first subscript is represented layer, and a back subscript represents the level of diffraction inferior.ψ _{0 ,+1}Representative is from layer L0 reflection and through the light beam of diffraction grating with+1 order diffraction, φ represents phase place, and V represents visibility.Only summarize principal element below.

I _sub，+1≈|ψ _0，+1| ²+|ψ _1，0| ²+2V ₀₁|ψ _0，+1||ψ _1，0|cos(φ _0，+1-φ _1，0)

Also promptly, if with ψ _1,0Disappear, so just removed double-deck noise.In other words, because the 0 grade of light beam that advances from other laminar flow is maximum noise, therefore by suitably reducing or removing the generation that 0 grade of light beam just can be eliminated this noise.

In order to eliminate 0 grade of light beam advancing from other laminar flow, can consider two kinds of methods.A kind of method is, adopt diffraction element (diffraction optical element: DOE), such as diffraction grating, perhaps holographic element (holographic optical elements (HOE): HOE), make the part optical diffraction that incides on the CD, thereby reduce or eliminate light quantity to different positions.Another kind method is, to using identical method from CD reflection and by this part light that PDIC receives.

The problem of first method is that it influences the amount of the light beam that incides CD widely, thus widely deterioration record or the signal that reproduces.Therefore, first method is inappropriate.Preferred second method also promptly adopts the method for DOE from CD reflection and the light path that received by PDIC at light beam.

In the present invention, integrally indicate the element of using diffraction with the conception of DOE, such as diffraction grating and HOE.

Figure 16 A and 16B illustrate and are used to remove the diffraction grating of interlayer interference and the beam distribution on the PD according to one embodiment of the invention.Diffraction grating according to Figure 16 A of one embodiment of the invention can be applied to the diffraction grating 140 or 240 of the optical pick-up of Fig. 8 or 9.

In the pattern of diffraction grating, showing the grating orientation of wherein phase place management area A12 and A13 as an example and using the angle between the grating orientation of regional A11 is the situations of 90 degree.In Figure 16 A and 16B, A11 has the grating that forms with horizontal direction, and A12 and A13 have the grating that forms with vertical direction.Therefore, be arranged in by the light beam of A11 diffraction and do not change the above and below of ground, do not change the left side and the right, ground by the light beam of diffraction grating and be positioned at by the light beam of A12 and A13 diffraction by the light beam of diffraction grating.

The diffraction grating of the diffraction grating of Figure 16 A and Figure 13 B is similar, except pattern A13 forms in pattern A11.As mentioned above, with reference to Figure 12 and 13, A11 (A3 of Figure 13 B) and A12 (A4 of Figure 13 B) are formed in the 1 light beam DPP method the required combination pattern of side beam that produces the skew (corresponding to the radial displacement of object lens) that is used to offset main beam, and they are designed such that do not comprise the AC component in side beam.

Operation hereto, A11 forms rectangular shape with pattern, so that in side beam, do not comprise in the baseball pattern ± and circular pattern P1 and the P3 of 1 grade of light beam b1 and b3, this baseball pattern is to be formed by the three-beam that produces during from CD reflection at light beam (0 grade light beam and+/-1 grade of light beam).Side beam through pattern A11 diffraction focuses on the PD (pair unit of light receiving element) that is used to receive side beam.

Certainly, change ground focuses on the PD (master unit of light receiving unit) that is used to receive main beam by the main beam of the diffraction grating of Figure 16 A, and is used for RF signal, focus signal and push-pull signal.Main beam and side beam have the light quantity that changes according to the outer shape of pattern A11, the recessed and protruding shape etc. that is used to form pattern A11.

From being different from current another layer (adjacent layer) beam reflected that writes down or reproduce thereon, do not change the diffraction grating of ground, and focus on the PD that is used for main beam by Figure 16 A when anterior layer.Focused beam is through the pattern A11 of Figure 16 A diffraction, and focuses on the PD that is used for side beam.From the further side beam of influence of adjacent layer beam reflected with less relatively light quantity, and thereby greatly influence use the tracking error signal of side beam.

Implement the present invention preventing flowing to the PD that is used for side beam, thereby prevent that tracking error signal from causing deterioration because of interlayer interference from the adjacent layer beam reflected.First kind of situation of tracking error signal deterioration is a kind of like this situation, that is, and and from adjacent layer reflection and change the light beam of ground by the diffraction grating of Figure 16 A and incide the PD that is used for side beam; And second kind of situation is a kind of like this situation,, incides the PD that is used for side beam from adjacent layer reflection and through the light beam of the A11 of Figure 16 A diffraction that is.

As the method that solves the problem in first kind of situation, the present invention adjusts recessed/convex form (having determined the angle of diffraction) of A11 and is used for the position of the PD of side beam so that through the A11 diffraction when the side beam of anterior layer be disposed in from adjacent layer, change outside the effective radius of ground by the light beam of the diffraction grating of Figure 16 A.

To this method, shown in Figure 17 A and 17B, the PD that will be used for side beam arranges to such an extent that be used to detect the PD of side beam more away from the PD that is used for main beam than the method for conventional DPP.Also promptly, will be used for the PD unit of main beam and the distance that is used between the PD unit of side beam is provided with greatly.For example, will be used for the PD of side beam and be used for distance D between the PD of main beam being made as conventional DPP method and being used for the PD unit of side beam and being used between the PD of main beam according to of the present invention apart from 5 times of d or more.In addition, shown in Figure 17 B, light receiving element can be arranged to comprise all PD that are used for conventional DPP detection and 1 light beam DPP of the present invention detection.

As the method that solves the problem in second kind of situation, implement the present invention in the A11 scope, to form the A13 that its grating orientation is different from the grating orientation of A11, make through the A11 reflection, be used for the PD of side beam from the side beam out-focus of adjacent layer, this PD be designed to receive through the A11 diffraction, when the side beam of anterior layer.

The outer shape of layout A13 is so that the zone of pattern A13 is corresponding to such zone, promptly, in this zone, from adjacent layer output and through the light beam of pattern A11 diffraction, can influence the light beam in the zone of the PD that wherein is provided for side beam, by the diffraction grating of Figure 16 A.

From the adjacent layer beam reflected diffraction grating by Figure 16 A, and focus on the PD that is used for main beam with the shape of B0 with changing.

In addition,, and focus on the zone that is located at the main beam above and below through the A11 of Figure 16 A diffraction from the adjacent layer beam reflected with the shape of B1.In this case, because grating orientation and the A11's of the A13 in the A11 is different, so can not flow to the PD (area B 2 of Figure 16 B) that is used for side beam from the light beam of adjacent layer.

In addition, a part is through the A12 of Figure 16 A diffraction from the adjacent layer beam reflected, and focus on the shape of B4 on the zone on the left side that is positioned at main beam and the right, and its other parts are through the A13 of Figure 16 A diffraction, and focus on the shape of B5 on the zone on the left side that is positioned at main beam and the right.Between the area B 4 of Figure 16 B and B5, form white space, because focus on the area B 1 through pattern A11 from the adjacent layer beam reflected.

Utilize the MPP signal---it is push-pull signal and SPP1 and the SPP2 signal that obtains from the PD that is used for main beam---its be the push-pull signal that obtains from the PD that is used for side beam, can obtain to track error signal according to DPP=MPP-k * (SPP1+SPP2).

As mentioned above, when the skew of supposing MPP signal and spp signal has linear behavio(u)r, this represents that they are directly proportional with the radial displacement of object lens, and, with respect to the radial displacement of object lens, the slope of the DC level of MPP signal is a, and with respect to the amount of the radial displacement of object lens, when the slope of the DC level of spp signal was b, can access proportionality constant k was k=1/2b.

Meanwhile, in Figure 16 B, in the light beam of A11 diffraction, from the side beam when anterior layer reflection have with from the different shape (level is microscler) of the shape (vertical long) of adjacent layer beam reflected B1.

Usually, be used for producing astigmatism to obtain the sensor leads 170 or 270 of focus error signal, utilize cylindrical lens with two axles for example the focus of x axle and y axle be provided with differently to incident light, therefore make the centre of focus of x axle and y axle become focal position.

The lens that are used to produce astigmatism play the effect that 90 degree keep the relative position of this incident beam are simultaneously rotated in incident and the shape (light quantity distribution) that focuses on the light beam between the focus of two axles.In addition, these lens can not rotate incident and focus on the shape of the extraneous light beam between the focus of these two axles.

Also be, from by sensor leads 170 or 270 time, having the light quantity distribution of having rotated 90 degree thereon when anterior layer (light beam is positioned on the focus to be used for record or reproduction) beam reflected, have the light quantity distribution that remain unchanged from adjacent layer (light beam is outside focus) beam reflected thereon, even light beam is by sensor leads 170 or 270.

Therefore, by A11 and have in the light beam (part on its left side and the right is removed by A12) of shape (vertical long) of Figure 18 A, microscler from by the lens that are used to produce astigmatism, be transformed into level when the anterior layer beam reflected, shown in Figure 18 B, even and from this light beam of adjacent layer beam reflected by also still keeping its vertical long after the lens that are used to produce astigmatism, shown in Figure 18 C.

Similarly, in light beam (only staying the left side and right-hand component because its middle body of A11 is removed) by A12, from the adjacent layer beam reflected, even after having passed through to be used to produce the lens of astigmatism, still when keeping its original-shape, focus on the position that deviates from the PD that is used for main beam and be used for the PD of side beam, as the situation of the B4 of Figure 16 B.

In this embodiment of the present invention, will A11 and the grating orientation of A12 form vertical.The grating orientation of A12 and recessed/convex form only are designed to prevent focus on PD that is used for main beam and the PD that is used for side beam at the light beam through the A12 diffraction from the adjacent layer beam reflected.Therefore, the angle of the diffraction of A12 is arranged to increase,, thereby prevents to focus on PD that is used for main beam and the PD that is used for side beam through the light beam of A12 diffraction even the grating orientation of A11 and A12 is mutually the same.

This fact also is applicable to grating orientation and the recessed/convex form of A13 in the same way.In addition, will A12 and grating orientation and the recessed/convex form (recessed/the protruding pitch and the degree of depth, protruding and recessed slope etc.) of A13 be designed to mutually the same.

Replace, regional A12 must not utilize grating to realize, it can be only thickness by adjustment region A12 only come correcting area A12 with respect to the phase place of regional A11.

In addition, the position of side beam focusing, the angle of diffraction etc. can obtain adjusting by the recessed/protruding pitch and the degree of depth that comprehensively is used to form pattern A11.

In addition, can realize like this,, remove pattern A13 and be formed at this point difference in the pattern A11 so that the shaped design of pattern A11 and A12 is become similar to the shape of the pattern A1 of the diffraction grating of Figure 13 A and A2 according to the diffraction grating of the embodiment of the invention.

Diffraction grating according to Figure 16 A of the present invention can be applied in the optical pick- up 100 and 200 diffraction grating 140 and 240 in Fig. 8 and 9.Situation for the optical pick-up among Fig. 8 100, when the diffraction grating among Figure 16 A being inserted between beam splitter 130 and the quarter wave plate 150, angle from optical efficiency, the preferred polarization-type diffraction grating that uses, the light beam that comes from CD reflection with diffraction only, and diffraction does not incide light beam on the CD.If light loss can be stood, also can use unpolarized type diffraction grating.In the optical pick-up 200 of Fig. 9, on the light path that diffraction grating 240 is not located between light source 210 and the CD, therefore there is no need to use the polarization-type diffraction grating.

In the optical pick- up 100 and 200 of it having been used Fig. 8 of the present invention and 9, preferably will all drive according in diffraction grating 140 of the present invention and 240 each with object lens 160 or 260, also promptly, they are installed in together with object lens 160 or 260 are used to support object lens 160 or 260 and the actuator that carries out focus servo operation and/or tracking servo operation.In addition, can be installed in respectively on the pedestal of optical pick-up 100 or 200 according to diffraction grating 140 of the present invention or 240, and not be installed on the actuator.

Figure 19 A and 19B illustrate the diffraction grating and the upward distribution of light beam of PD that are used to remove interlayer interference according to another embodiment of the present invention.In Figure 19 A and 19B, the x direction is represented inside/outside circumference (radially) direction, and the y direction is represented trajectory direction.

The diffraction grating of Figure 19 A has and the similar pattern of the pattern of Figure 13 B, and it is characterized in that, compares with the diffraction grating of Figure 13 B, and it further comprises the regional A23 that is used to proofread and correct based on the phase place of the main signal of main beam.Zone A23 plays the effect of the phase place of proofreading and correct main signal, and play according to based on the sub signal blocking-up of side beam from being different from the current record layer or reproducing the effect of light of the adjacent recording layer reflection of layer.

In Figure 19 A, zone A21 comprises the grating that forms with vertical direction, and regional A22 and A23 comprise the grating that forms with horizontal direction, and therefore the light beam through regional A21 diffraction is arranged at not changing the left side and the right by the light beam of diffraction grating, ground, shown in Figure 19 B.

Except that the grating orientation of corresponding region difference opposite each other, the embodiment of the embodiment of Figure 16 A and 16B and Figure 19 A and 19B is similar.Yet, in these two embodiment, be used to receive through the shape and the position of the pair unit of the side beam of diffraction grating diffraction and have nothing in common with each other.Similar with the embodiment of Figure 16 A and 16B, regional A22 needn't realize with grating, as long as but can adjustment region A22 with respect to the phase place of regional A21.

Figure 19 B is illustrated in the multilayer recording medium by the pattern of the diffracted beam of the diffraction grating of Figure 19 A and based on the example of the deployment scenarios of unit in the Electro-Optical Sensor Set of this pattern.To this situation, B11, B22 and B33 represent from recording layer or reproduce after the layer reflection light beam by diffraction grating.B11 and B33 representative are through the side beam of the diffraction grating diffraction of Figure 19 A, and the B22 representative does not change the main beam of ground by the diffraction grating of Figure 19 A.In addition, the little rectangle among light beam B11, B22 and the B33 is formed by regional A23.

In Figure 19 B, reference number 192 representatives are used to receive the master unit of main beam, and 194 representatives are used to receive the pair unit of side beam.In Figure 19 B, the diagonal line shadow region is represented from adjacent recording layer beam reflected.Pair unit and mark this fact round the zone of pair unit with white and represent not incide on these zones from adjacent recording layer beam reflected, this is owing to regional A23.

For this problem of variation of the position that solves side beam, the pair unit that is used to receive side beam is set to have the width wideer than existing unit.The reason that moves of side beam can comprise that the interlayer between each recoding/reproduction layer moves, compensation of spherical aberration, the variation of the focal length of lens or the like.In addition, in order to prevent to incide on the pair unit, arrange that master unit and pair unit make that the distance (D) between them is bigger from adjacent layer reflection and the light beam that flows to the master unit position adjacent.

Figure 20 A and 20B illustrate the example according to the light receiving element of the embodiment of Figure 19.Light receiving element of the present invention comprises the pair unit 194 that is used to receive the master unit 192 of main beam and is used to receive side beam.To this situation, the orientation of light receiving element and position change according to the grating orientation and the magnification of optical system.Pair unit 194 is characterised in that, they are located at from the position that the light of adjacent layer reflection can not incide.

Figure 20 B is illustrated in the embodiment of the Electro-Optical Sensor Set of for example together using in the 3 light beam DPP methods according to the 1 light beam DPP method of the embodiment of Figure 19 and conventional method.The Electro-Optical Sensor Set of Figure 20 B comprises the unit 196 that is used to receive the side beam that 3 light beam DPP methods by routine produce, and is used to receive the master unit 192 of main beam and two and is used to receive pair unit through the side beam of the diffraction grating diffraction of Figure 19 A.Pair unit 194 is located at and is not subjected to from the position that the adjacent layer beam reflected influences.

Figure 21 A and 21B illustrate other example according to the Electro-Optical Sensor Set of the embodiment of Figure 19, and it shows by considering that astigmatism changes the position of pair unit 194 and the Electro-Optical Sensor Set that shape is obtained.In the optical system that adopts astigmatic method, according to the direction and the focal length of cylindrical lens, main beam and side beam focus on the light receiving element of inclination.

Therefore, shown in Figure 21 A and 21B, pair unit 194 can be located at diagonal line ground and depart from Party member of the CPC 192 the position, and be used to obtain the boundary surface of the pair unit 194 of push-pull signal can be with shape with inclination.This boundary surface can be according to being divided by the angle of the straight line definition that connects master unit 192 and pair unit 194.Even concerning this situation, with Figure 20 category-B seemingly, Electro-Optical Sensor Set can also comprise the pair unit 196 3 light beam DPP methods, that be used to produce side beam based on routine.

Meanwhile, in the diffraction grating of Figure 16 A and 19A, area of the pattern A13 (A23) (it prevents to incide on the pair unit that is used to the required side beam of generation tracking error signal from the adjacent layer beam reflected) is embodied as discrete component on the plane identical with A12 (A21 and A22) with area of the pattern A11, and area of the pattern A11 and A12 are based on the area of the pattern that 1 light beam DPP method is used to produce side beam.

Yet, the invention is not restricted to these embodiment, and can realize allowing to construct individually the defraction grating device that comprises area of the pattern A13 (A23) and to comprise the defraction grating device of area of the pattern A11 and A12 (A21 and A22) situation among the embodiment that will describe as the back like this.

To Figure 21 A and 21B the embodiment that is used to solve because of the noise (also being the problem of interlayer interference) that causes from the adjacent layer beam reflected has been described with reference to Figure 16 A and 16B.The light beam that top embodiment realization utilizes diffraction element will flow to Electro-Optical Sensor Set is partly eliminated.Yet, diffraction element not only will be from the some or all of elimination of adjacent layer beam reflected, flow to the current part generation diffraction in the light beam of anterior layer that carries out recoding/reproduction thereon but also make, thereby removed the segment beam spot that focuses on the Electro-Optical Sensor Set, perhaps reduced the intensity of beam spot widely.

This part beam spot of having removed or its intensity reduced by this way is called the dead band.When object lens radially were shifted, proportionality constant k changed according to the section (section) of the radial displacement that causes owing to this dead band, and the performance degradation of RF signal and reproduction/record.The embodiment that is used to address this problem is described below.

At first will describe by the typical DPP method that will utilize 3 light beams and the diffraction optical element (DOE) that is used to produce diffraction effect in conjunction with the method that reduces interlayer interference.

Figure 22 A shows the distribution situation of light beam on the shape of DOE when adopting 3 light beam DPP methods and position and the PD to 22C.

Adopt the optical pick-up 300 of 3 light beam DPP methods, shown in Figure 22 B, comprise light source 310, collimation lens 320, grating 325, beam splitter 330, DOE 350, object lens 370, sensor leads 380 and Electro-Optical Sensor Set 390.In adopting the optical system of 3 light beam DPP methods, the grating 325 that will be used for producing the side beam of DPP is located at the light path between light source 310 and the object lens 370.Usually, the grating 325 that will be used for 3 light beams is inserted between collimation lens 320 and the beam splitter 330.

In the optical system of the 3 light beam DPP methods of employing, shown in Figure 22 B, when the DOE 350 of the pattern that will have Figure 22 A is inserted on the light path of the folded light beam that extends to PD 390 from CD, also be, when light beam focuses on the light path of PD 390 by object lens 370, beam splitter 330 and sensor leads 380, the part of the 0 grade of light beam that flows to from adjacent layer is separated because of the pattern of DOE, and is directed into other position on the PD 390, shown in Figure 22 C.

In Figure 22 A, the DOE pattern of DOE 350 has the grating that forms with vertical (vertically) direction, and thereby the light beam that passes through DOE 350 of part is by DOE pattern diffraction (+/-1 order diffraction light beam), and the light beam of this diffraction is set at and does not change the left side and the right by 0 grade of light beam of DOE pattern, ground, shown in Figure 22 C.To this situation, 0 grade of light beam and+light beam of/-1 order diffraction indicates whether to occur diffraction based on the DOE pattern.

Because from focusing on the PD 390 when the anterior layer beam reflected of writing down thereon or reproducing, so the size correspondence of this light beam the unit size of PD 390, and the intensity of light beam strong (these light beams mark with dark color in Figure 22 C).

From main beam and two side beams (separating) (B through grating 325 when the anterior layer reflection _{CL, 0}, B _{CL ,+1}, and B _{CL ,-1}) focus on the master unit that is used for MPP of PD 390 and be used for the pair unit of SPP.The light beam of part and focuses on master unit and pair unit (B by DOE pattern diffraction _{CL, 0} ^+/1, B _{CL ,+1} ^+/-1, B _{CL ,-1} ^+/-1) the left side and the right, and thereby in master unit and pair unit, form above-mentioned dead band (B _{CL, 0} ⁰, B _{CL ,+1} ⁰, B _{CL ,-1} ⁰).

Owing to focus on front or the back of PD 390 from non-adjacent layer beam reflected, so focus on big and its weak strength (these light beams mark with light color in Figure 22 C) of light beam on the PD 390 when anterior layer.

Form big round B from the adjacent layer beam reflected by DOE 350 and in the central authorities of Figure 22 C _OL, and the left side and the right rectangle B _OL ^{+ 1}And B _OL ^-1, passed through the great circle B of the light beam of DOE pattern in central authorities _OLThe interior vertically long rectangle B that forms _OL ⁰, and form in the position on the left side of this great circle and the right and to have and vertical long rectangle B _OL ⁰The rectangle B that shape is identical _OL ^{+ 1}And B _OL ^-1

The rectangle B that forms by the DOE area of the pattern of Figure 22 A _OL ⁰Corresponding to the shape of the unit of PD 390, and thereby can not disturb from when the anterior layer reflection and focus on light beam on the PD 390.Also promptly, can reduce the noise that in MPP signal and spp signal, causes because of noise light from the adjacent layer reflection.

Consider this fact, also be, the master unit of PD and the shape of pair unit and position (with respect to the light beam that forms by adjacent layer) and/or result from master unit and pair unit in the size in dead band and intensity (with respect to by the light beam that forms when anterior layer), design the shape of DOE pattern and DOE area of the pattern.

As shown in figure 23, DOE 350 can realize having very little difference at its aspect of performance that abates the noise with different shape.Particularly, importantly, DOE is not so that can flow to the pair unit that is used for producing spp signal from the adjacent layer beam reflected in design.Not direction and the shape that the zone of DOE pattern just must realization can be adjusted this regional thickness or grating suitably, to prevent between described zone and DOE area of the pattern, producing phase differential.

In addition, the pattern direction of DOE (grating orientation) preferably keeps 90 degree with respect to the grating 325 that is used for 3 beam separation, although not necessarily must be with the DOE patterned arrangement for to meet at right angles with respect to grating 325.In the embodiment of Figure 22 A and 22B, because grating 325 has the grating that forms with horizontal direction, side beam B _{OL ,+1}And B _{OL ,-1}At main beam B _{OL, 0}The above and below form, shown in Figure 22 C.In addition, the pitch of the grating of DOE pattern is preferably designed to and makes and to be separated and the light beam that focuses on the PD is configured to overlap each other away from each other and not by the DOE pattern.

Shown in Figure 22 B, DOE can be arranged on position (A) to (C).When DOE being placed the light path that light beam passed through that incides on the CD and on the light path that light beam passed through of CD reflection the time,, DOE must be manufactured polarization dependent form element, such as liquid crystal as the situation of (A) in the position.In addition, when DOE being placed position (A), preferably DOE is installed on the actuator, moving DOE, because can reduce the zone of DOE along object lens.

When DOE being placed position (B), must must be bigger than (A) with the DOE zone design, so that when the object lens radial displacement, can not flow among the PD from the noise of adjacent layer.Also DOE can be placed position (C), if consider factor such as fabrication tolerance, then position (C) is favourable not as position (B), although the area of DOE identical with respect to the diameter of incident beam and position (B).

Usually, use DOE pattern in diffraction efficiency from 0 to 60% scope wherein be used for 0 grade of light beam.For this situation, the diffraction efficiency that is used for 0 grade of light beam corresponding to 60% means that 60% of the light beam that incides on the DOE pattern changes ground by wherein, and all the other light beams of 40% are by DOE pattern diffraction.

In Figure 22 A, along with the diffraction efficiency of DOE pattern near 0% o'clock, focus on the area B of Figure 22 C as 0 grade of light beam _OL ⁰Light quantity reduced, and thereby inciding on the master unit and pair unit of PD from the adjacent layer beam reflected still less arranged, this means the noise that in MPP signal and spp signal, produces still less.

Yet the noise of MPP signal and spp signal is not only removed or reduced to the DOE pattern, and removed the light beam (B of the part that is used for reproducing signal _{CL, 0} ⁰, B _{CL ,+1} ⁰, B _{CL ,-1} ⁰).Along with the minimizing of the 0 order diffraction light beam that flows to the dead band, also, along with the diffraction efficiency of DOE pattern near 0%, also can deterioration such as the reproducing signal of RF signal or servosignal.

In addition, this dead band disadvantage is that when object lens radially were shifted, it changed the value k of each section that is used for radial displacement based on the radial displacement amount.This variation of value k causes the skew in the DPP signal, thus deterioration the performance of tracking servo.

Shown in Figure 22 C, inciding DOE pattern (each all has the vertical long rectangle of Figure 22 A) and from the light beam of DOE pattern diffraction, from when the anterior layer reflection and be formed at each light beam (B on PD surface _{CL, 0} ⁰, B _{CL ,+1} ⁰, B _{CL ,-1} ⁰, B _{CL, 0} ^+/-1, B _{CL ,+1} ^+/-1, B _{CL ,-1} ^+/-1) have and each the light beam (B that reflects and be formed at the PD surface from adjacent layer _OL ⁰, B _OL ^{+ 1}, B _OL ^-1) the different shape (the long rectangle of level) of shape (vertically long rectangle).This is owing to having adopted sensor leads above-mentioned cylindrical lens, that be used to produce astigmatism.

Therefore, when behind the DOE area of the pattern diffraction of the vertical long rectangular shape that had Figure 22 A when the anterior layer beam reflected, when being used to produce the sensor leads of astigmatism, this light beam is converted into the light beam with the long rectangular shape of level, such as the B of Figure 22 C _{CL, 0} ⁰, B _{CL ,+1} ⁰, B _{CL ,-1} ⁰, B _{CL, 0} ^+/-1, B _{CL ,+1} ^+/-1, and B _{CL ,-1} ^+/-1, and focus on the surface of PD then.

On the contrary, keeping the vertically B of long rectangular shape such as Figure 22 C from the adjacent layer beam reflected _OL ⁰, B _OL ^{+ 1}, B _OL ^-1The time focus on the surface of PD, even this light beam behind the DOE of vertical long rectangular shape area of the pattern diffraction through having Figure 22 A by being used to produce the sensor leads of astigmatism.

Next, a kind ofly, 1 light beam DPP method and DOE reduce the method for interlayer interference with describing by being combined.

The shape of DOE and the situation of the beam distribution on position and the PD when Figure 24 A is illustrated in the 1 light beam DPP method of employing to 24C.

In Figure 24 B, adopt the optical pick-up 400 or 500 of 1 light beam DPP method to comprise light source 410 or 510, collimation lens 420 or 520, beam splitter 430 or 530, grating 440 or 540, DOE 450 or 550, object lens 470 or 570, sensor leads 480 or 580 and Electro-Optical Sensor Set 490 or 590.According to the position of grating 440 or 540, can in optical pick-up 400 or 500, comprise quarter wave plate 460.

Grating 440 or 540 is different from the grating 325 of Figure 22 B fully.The grating 325 of Figure 22 B has the raster shape that is used to produce 3 light beams, and the grating 440 or 540 of Figure 24 B has such raster shape, it is in by the light beam of the bank of the track of CD/groove structure reflection and separation, only diffraction corresponding to the light beam of DC component (skew) not diffraction corresponding to the light beam of AC component, as Fig. 7 C or Figure 13 A to as shown in the 13C.

The side beam B of Figure 24 C _{CL ,+1}, and B _{CL ,-1}Have in use and have the grating 440 of shape of Fig. 7 C or Figure 13 A or the shape that obtained at 540 o'clock.When the pattern of Figure 13 A as grating 440 or 540 the time, have the grating that forms with horizontal direction as the regional A1 of first pattern, and thereby through regional A1 diffraction+side beam of/-1 grade of light beam _{BCL ,+1}And B _{CL ,-1}Be arranged in main beam B _{CL, 0}The above and below of (it is the 0 grade of light beam that does not pass through grating 440 or 540 with changing) is shown in Figure 24 C.

Shown in Figure 22 B, DOE 450 or 540 can be placed position (A) to the position (C), and the same in the characteristic of each locational DOE with situation in the aforesaid employing 3 light beam DPP methods.In addition, can with grating 440 or 540 and DOE 450 or 550 be integrated into single structure.When the DOE that will be used for 1 light beam DPP method or grating place the light path that light beam passed through that incides CD and on the light path that light beam passed through of CD reflection the time, angle from optical efficiency, for diffraction only from the light beam of CD reflection, and diffraction does not incide light beam on the CD, preferably DOE or grating is manufactured the polarization-type element.Thereby, DOE or grating must be manufactured polarization dependent form element, such as liquid crystal.

Similar with top situation, the grating orientation that the grating orientation of the DOE pattern in will DOE 450 or 550 is arranged in respect to the grating 440 in the 1 light beam DPP method or 540 forms the right angle.Also promptly, only need the DOE pattern is formed, make on the master unit and pair unit of light beam out-focus at PDIC of DOE 450 or 550 diffraction.For example, even the DOE pattern in DOE450 or 550 has identical grating orientation with the grating 440 or 540 that is used for 1 light beam DPP method, still the angle with the diffraction of DOE pattern is provided with increase, thereby prevents to be focused on the master unit and pair unit of PDIC by the light beam of DOE pattern diffraction.

Yet, more preferably, arrange the DOE pattern and be used for the grating 440 of 1 light beam DPP method or 540 grating orientation, between them, to form the right angle.At Figure 24 A in the embodiment of 24C, because grating 440 or 540 has the grating that forms with horizontal direction (radially), so side beam B _{CL ,+1}And B _{CL ,-1}At main beam B _{CL, 0}The top form, shown in Figure 24 C.In addition, the raster pitch of decision design DOE pattern and grating so that the light beam that focuses on the PD can overlap each other away from each other and not.

Similar with top description, consider the shape and the position of the master unit of PD and pair unit and/or result from master unit and pair unit in the size and the intensity in dead band, design DOE pattern and shape thereof.

Also promptly, its profile of zone of DOE pattern is designed to corresponding to the zone of wherein passing through DOE 450 or 550 at the light beam of master unit that can influence PD from the adjacent layer beam reflected and pair unit among the DOE 450 or 550.Particularly, importantly design the zone of DOE so that the pair unit minimum degree of PD be subjected to from the influence of adjacent layer beam reflected.Therefore, DOE 450 or 550 can realize with different shape, as Figure 23 A to shown in the 23C.

When the zone design of DOE pattern being become, also can occur because of dead band B with the 3 light beam DPP methods of Figure 22 A consistent _{CL, 0} ⁰, B _{CL ,+1} ⁰And B _{CL ,-1} ⁰The tracking servo that causes and the deterioration of reproduction/tracer signal.

The variation of the value k that causes because of the dead band is described below.When object lens radially are not shifted, when side beam accurately focuses on the center of pair unit, as can be seen from Figure 25, when object lens radially when the center of optical pick-up is displaced to the interior or excircle of CD, in the zone that comprises the dead band with do not comprise that the value k (rate of curve) of acquisition in the zone in this dead band is different.MPP skew and SPP skew change, but they can not cause subject matter, and skew changes along identical direction because the MPP skew is with SPP.

Yet, as shown in figure 26, this situation often occurs, side beam is owing to interlayer moves, the variation of the magnification of the pitch error of diffraction element, optical system etc. is configured to depart from slightly the center of pair unit, even also is like this when object lens radially are not shifted.Exist even without other error, when reproducing or recording layer L0 and during as the mobile reproduction of passing through interlayer or recording layer L1, the position of side beam still changes inevitably.

To this situation, as shown in figure 26, MPP skew and SPP skew with opposite direction (their opposite in sign) even change---these skews be produce partly and side-play amount little, therefore there is such problem, that is, the skew of the MPP signal that produces when object lens radially are shifted can not utilize the skew of spp signal and obtain offsetting.

Meanwhile, different with the distribution of light beam among Figure 16 B or the 19B, the distribution of light beam shows among Figure 24 C because master unit and pair unit are adjacent one another are, therefore by grating 440 or 540 and DOE 450 or 550, from the light beam (B of adjacent layer _OLIn B _OL ⁰) also focus on the pair unit, thereby influence the tracking error signal that from pair unit, produces.

Shown in Figure 16,17 and 19 to 21 embodiment, when master unit and pair unit are provided with away from each other, benefit is that pair unit is subjected to the influence from the light beam of adjacent layer hardly, and some problems are arranged also, promptly, the size of optical pick-up increases because of the increase of Electro-Optical Sensor Set equidimension, and the optical efficiency deterioration of grating, because must be big from the angle of the diffraction of the side beam of the optical grating diffraction that is used for 1 light beam DPP.

For the situation of Figure 24 C and since from adjacent layer, change the part of ground by the light beam of grating 440 or 540, in its area of the pattern, be diffracted into area B by DOE 450 or 550 _OL ^{+ 1}And B _OL ^-1, therefore focus on area B _OL ⁰On the intensity of light beam less than area B _OLOn the intensity of light beam.

Consider the reduction of the optical efficiency of the condition of increase of size of slight minimizing, optical pick-up of the light quantity of side beam and grating, can preferably be provided with master unit and pair unit to such an extent that close on each other that the embodiment that the back will be described is at this situation.

For the situation of 1 light beam DPP method, can change the position of pair unit, also, the position that side beam focuses on.Figure 27 A is relevant to the embodiment of 24C with Figure 24 A, and is illustrated in the grating orientation that the grating 440 or 540 that is used for 1 light beam DPP is used to produce the pattern of side beam and forms with horizontal direction, shown in Figure 27 A.Thereby, side beam B _{CL ,+1}And B _{CL ,-1}Be located in main beam B _{CL, 0}The above and below.

Owing to be used to remove the DOE 450 of interlayer interference among Figure 27 A or 550 DOE area of the pattern has the grating that forms at vertical direction, therefore, form on the left side and the right of PDIC from adjacent layer reflection and through the light beam of DOE pattern diffraction, although this point is not shown among Figure 27 A.

On the contrary, in Figure 27 B, the grating orientation that is used to produce the pattern of side beam at the grating 440 or 540 that is used for 1 light beam DPP, and the grating orientation of DOE area of the pattern in DOE 450 or 550, be designed to respectively and the difference that has with respect to the situation of Figure 27 A corresponding to 90 degree, therefore the position of the pair unit of PDIC must be revolved and turn 90 degrees.

Each pair unit must be divided into two parts at least corresponding to radially direction.Here, determine and radially corresponding direction, and do not consider to be used to produce the grating orientation of the pattern of side beam at the grating that is used for 1 light beam DPP.In Figure 27 A and 27B, horizontal direction represents radially, and turn 90 degrees from revolving because of sensor leads when the shape of anterior layer beam reflected, makes that the grating orientation of pair unit of PDIC is a vertical direction.Therefore, shown in Figure 27 A and 27B, must also be top and lower part with each pair unit based on the vertical direction separated into two parts.

For the situation of Figure 27 B, horizontal direction is lined up in the dead band.In addition, when object lens during at radial displacement, main beam and side beam radially move.As mentioned above, radially be vertical direction among the PDIC of Figure 27 B.Thereby, the variation of the value k that the radial displacement because of object lens causes can not appear.

In addition, as mentioned above, even with the object lens centering time, still such situation can often appear, that is, side beam is arranged to deviate from a little the center of pair unit because of the variation of the magnification of the error of the pitch of the moving of interlayer, diffraction element, optical system etc.For the situation of the embodiment of Figure 27 B, side beam moves in the direction consistent with the straight line that is used to divide pair unit, shown in Figure 28 B.Therefore, signal is not subjected to the influence of moving of the side beam that causes because of some factors.

Figure 29 A to 29C illustrate different shape, be used to remove the DOE of interlayer interference and be used for the example that the diffraction grating of 1 light beam DPP method is realized in a plane.When the transmissivity of 0 grade of light beam up to 50% to 60% the time, can use common grating but not HOE.In addition,, each grating pattern can be formed in the plane to shown in the 29C as Figure 29 A., the shape and the various diffraction grating of DOE pattern can be combined to shown in the 29C as Figure 29 A.

Shown in Figure 30 A and 30B, the light beam that incides on the diffraction grating is divided into: 0 grade of light beam, and it does not pass through diffraction grating with changing; And diffracted optical grating diffraction+/-1 grade of light beam.0 grade of light beam and+angle of diffraction of/-1 grade of light beam and light quantity can adjust by comprehensively recessed/protruding pitch, cup depth, protruding/recessed dutycycle, protruding and recessed slope etc.

For the transmissivity of 0 grade of light beam making DOE is approximately 0, must be with most optical diffraction by the DOE pattern.This structure can realize by the type HOE that glitters, shown in Figure 30 C.When DOE is when the DOE surface being divided into a plurality of steps subtly realizing, this DOE is approximately the type HOE that glitters, and along with more fine forming the step of dividing, the transmissivity of 0 grade of light beam is approximately 0.

When DOE being arranged to object lens when mobile, it must only react to the polarized state of light that comes from CD reflection, thereby liquid crystal is used for this operation.Arrange liquid crystal like this,, thereby produce phase differential with the method identical with the method for typical diffraction grating or HOE so that refractive index is only different on the specific polarization component.

Figure 31 illustrates the main structure that has adopted according to the data recording/reproducing device of optical pick-up of the present invention.Data recording/reproducing device according to the present invention comprises the optical pick-up that is used to allow light beam to incide on the recording medium and receives the signal that reflects from recording medium, be used to receive from the signal of optical pick-up and modulate the signal processing unit of this signal that receives, be used to produce the control module of servosignal such as focus error signal and tracking error signal from the signal of signal processing unit, with utilize servosignal to carry out control operation to follow the servo unit of this track to allow laser beam.

Optical pick-up 100,200,400 of the present invention or 500 can be applied in the optical pick-up part that can write down and/or reproduce all CD, DVD and BD.

For example, when the optical system that will be used for CD and DVD and be used for the optical system of BD when single pick-up is realized, two object lens must be installed on the single actuator, and the objective lens arrangement of optical system that will be used for BD usually is for from axle, as shown in Figure 3.

Therefore, optical pick-up 100,200,400 of the present invention or 500 can be applied to be used for the optical system of BD, makes because the problem of the 3 light beam DPP aspects that may occur from the axle layout of object lens can be solved.

In addition, optical pick-up 100,200,400 of the present invention or 500 can be removed the noise that occurs that causes because of interlayer interference in reproduction/tracer signal, therefore it is applicable to the recoding/reproduction of the optical storage medium with a plurality of recording layers, DVD-RAM for example, DVD-RW, DVD+RW, DVD-R, DVD+R, BD-R, BD-RE etc.

As mentioned above, the advantage of optical pick-up of the present invention is, it can remove the skew of arranging the push-pull signal cause from axle because of object lens, can remove the interlayer noise that occurs in the multiplayer optical disk effectively, and can eliminate the influence in the dead band that when removing the interlayer noise, produces, therefore can remove the skew of the push-pull signal that the radial displacement because of object lens causes and the influence of moving of side beam effectively, thereby obtain stable tracking error signal and improved and reproduced and the performance of record.

Although for the example purpose discloses the preferred embodiments of the present invention, but person of skill in the art will appreciate that, under the prerequisite that does not deviate from the disclosed scope and spirit of the present invention of appended claims, can make various variations, increase and replacement to the present invention.

Claims (30)

1. optical pick-up comprises:

Light source is used for emission and has light beams of predetermined wavelengths;

Object lens, the light beam that is used for sending from this light source focuses on optical storage medium;

Beam splitter, be used to make the light beam that sends from light source or from this optical storage medium beam reflected by or be reflected;

First diffraction element is used for from producing second light beam through this optical storage medium beam reflected, and this second light beam does not have and the corresponding component in the position of light beam on the track of this optical storage medium that focuses on this optical storage medium;

Second diffraction element;

Sensor leads is used for producing astigmatism from the optical storage medium beam reflected; With

Electro-Optical Sensor Set comprises being used to receive not changing the main sniffer of ground by first light beam of first and second diffraction elements, and two first secondary sniffers that are used to receive second light beam,

Wherein this second diffraction element will be from the segment beam diffraction when the anterior layer reflection that writes down thereon or reproduce other layer reflection of optical storage medium rather than current, thereby the light beam that prevents this diffraction incides on the Electro-Optical Sensor Set.

2. optical pick-up as claimed in claim 1, wherein this first diffraction element comprises incident beam that is used for a diffraction part and the first area that produces second light beam, and this first area does not comprise such zone, in this zone, in by this optical storage medium diffraction and separation from this optical storage medium beam reflected, by the light beam of this optical storage medium diffraction with by first diffraction element time, do not overlapped each other by the light beam of this optical storage medium diffraction.

3. optical pick-up as claimed in claim 2, wherein this first area forms rectangular shape, it has such zone as the border, in this zone, is being passed through first diffraction element by the light beam of this optical storage medium diffraction from this optical storage medium beam reflected.

4. optical pick-up as claimed in claim 2, wherein this first area comprises the zone that is arranged in the top straight line top that is used for connecting four points as described below at 2 and is positioned at the zone that is used to be connected below the following straight line at 2: from this optical storage medium beam reflected, by the light beam of this optical storage medium diffraction with not by the light beam of this optical storage medium diffraction, by first diffraction element time, intersect at described four some places.

5. optical pick-up as claimed in claim 2, wherein this first diffraction element comprises second area, in this zone, in the zone except that the first area, form grating pattern, and this second area will be by this grating pattern a part of diffraction of light beam, and prevent that the light beam of this diffraction from focusing on this Electro-Optical Sensor Set.

6. optical pick-up as claimed in claim 5, wherein this first area and second area have the grating orientation that forms the right angle.

7. optical pick-up as claimed in claim 2, wherein this first area comprises such grating, its form to make a part incident beam with the light beam direction vertical by the direction of this optical storage medium diffraction on diffracted.

8. optical pick-up as claimed in claim 2, wherein this first area comprises such grating, it form to make that the incident beam of a part is diffracted on by the direction of this optical storage medium diffraction at light beam.

9. optical pick-up as claimed in claim 2, wherein this second diffraction element comprises the 3rd zone of the incident beam that is used for a diffraction part, and the 3rd zone is passed through this second diffraction element corresponding to such zone at the light beam that will focus on this Electro-Optical Sensor Set in this zone from described other layer beam reflected.

10. optical pick-up as claimed in claim 9, wherein this first area comprises such grating, its form to make a part incident beam with the light beam direction parallel or vertical by the direction of this optical storage medium diffraction on diffracted.

11. optical pick-up as claimed in claim 10, wherein this first area and the 3rd zone have the grating orientation that forms the right angle.

12. optical pick-up as claimed in claim 9, wherein the 3rd zone is passed through second diffraction element corresponding to such zone at the light beam that will focus on the first secondary sniffer in this zone from described other layer beam reflected.

13. optical pick-up as claimed in claim 2, wherein each first secondary sniffer is set at and is not changing outside the effective radius of ground by the light beam of first diffraction element and second diffraction element from described other layer beam reflected.

14. optical pick-up as claimed in claim 13, wherein this second diffraction element comprises the 3rd zone of the incident beam that is used for a diffraction part, and second diffraction element passed through at the light beam that will focus on the first secondary sniffer corresponding to such zone in the 3rd zone from described other layer beam reflected in this zone.

15. optical pick-up as claimed in claim 14, wherein this first area comprises such grating, its form to make a part incident beam with direction that wherein light beam is parallel or vertical by the direction of this optical storage medium diffraction on diffracted, and wherein this first area and the 3rd zone have the grating orientation that forms the right angle.

16. optical pick-up as claimed in claim 13, wherein each first secondary sniffer has the width wideer than the width of main sniffer.

17. optical pick-up as claimed in claim 13, wherein each first secondary sniffer is arranged on the position that deviates from this main sniffer according to the focus direction and the focal length of this sensor leads.

18. optical pick-up as claimed in claim 17, wherein each first secondary sniffer is divided by the border surface that the angle that limits with the straight line that is used to connect the first secondary sniffer and this main sniffer forms, to obtain push-pull signal.

19. optical pick-up as claimed in claim 13, further comprise this beam diffraction that is used for sending from this light source become 0 grade of light beam and+/-1 grade of light beam and the light beam of this diffraction focused on grating on this optical storage medium, and

Wherein this Electro-Optical Sensor Set further comprise be used to receive from this optical storage medium reflection+two second secondary sniffers of/-1 grade of light beam.

20. optical pick-up as claimed in claim 19, wherein the distance that has between them of this first secondary sniffer and this main sniffer is 5 times or bigger multiple of distance between the second secondary sniffer and this main sniffer.

21. as arbitrary described optical pick-up in the claim 2,9 and 13, wherein this first diffraction element and second diffraction element are integrated into individual devices.

22. as arbitrary described optical pick-up in the claim 2,9 and 13, wherein this first diffraction element be inserted between this beam splitter and this object lens, between this beam splitter and this sensor leads or between this sensor leads and this Electro-Optical Sensor Set.

23. optical pick-up as claimed in claim 22 further comprises, when this first diffraction element was inserted between this beam splitter and this object lens, being used between first diffraction element and this object lens made the quarter wave plate of the polarization rotation of light beam.

24. optical pick-up as claimed in claim 23, wherein this first diffraction element only diffraction from this optical storage medium beam reflected, and the light beam that sends from this light source of diffraction not.

25. as arbitrary described optical pick-up in the claim 2,9 and 13, wherein this second diffraction element be inserted between this beam splitter and this object lens, between this beam splitter and this sensor leads or between this sensor leads and this Electro-Optical Sensor Set.

26. optical pick-up as claimed in claim 25, wherein when this second diffraction element is inserted between this beam splitter and this object lens, this second diffraction element only diffraction from this optical storage medium beam reflected, and the light beam that sends from this light source of diffraction not.

27. optical pick-up as claimed in claim 1, wherein this first diffraction element and the second diffraction element both adopt the liquid crystal manufacturing.

28. as arbitrary described optical pick-up in the claim 2,9 and 13, wherein:

This main sniffer respectively by with radially and on the tangential corresponding direction be divided into two parts at least, and each first secondary sniffer quilt is being divided into two parts at least with radially corresponding direction, and

When supposing that the push-pull signal by this main detection is Mpp, and when being Spp1 and Spp2 by two push-pull signals of the first secondary detection, tracking error signal is surveyed by Mpp-k (Spp1+Spp2), and wherein the variation of the skew of the variation of the skew of this Mpp of causing based on the radial displacement because of these object lens of k and Spp1 and Spp2 is calculated.

29. optical pick-up as claimed in claim 1, wherein this optical storage medium is a CD (CD)-can write down (R), CD-can rewrite (RW), digital multi-purpose CD (DVD)-random-access memory (ram), DVD-RW, and DVD+RW, DVD-R, DVD+R, Blu-ray Disc (BD)-can write down (R) and BD-can write at least a in (RE).

30. optical pick-up as claimed in claim 1, wherein this light source sends the light with blue light wavelength, and these object lens deviate from the central shaft of this optical storage medium.

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