CN1497555A - Optical disk device and spectral device - Google Patents
Optical disk device and spectral device Download PDFInfo
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- CN1497555A CN1497555A CNA2003101014662A CN200310101466A CN1497555A CN 1497555 A CN1497555 A CN 1497555A CN A2003101014662 A CNA2003101014662 A CN A2003101014662A CN 200310101466 A CN200310101466 A CN 200310101466A CN 1497555 A CN1497555 A CN 1497555A
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Abstract
The present invention provides an optical disk device and an optical splitter in each of which even if an objective lens and a polarization hologram substrate deviate in a disk radial direction, off-track does not occur under tracking control, and two radiation light sources can simultaneously be handled in the case of employing a configuration with two radiation light sources. Light emitted from a radiation light source is reflected by a signal plane of an optical disk, and passes through an objective lens to enter an optical splitter. The optical splitter is divided into four quadrants Ak (wherein k=1, 2, . . . ) by two straight lines that intersect with an optical axis. The photodetector is divided into at least four regions Bk. First-order diffracted lights ak are derived from light that has entered the quadrants Ak by the optical splitter and are projected on the regions Bk of the photodetector, respectively. Sections of the first-order diffracted lights a2 and a3 taken along the x-axis lie approximately on a boundary between the regions B2 and B3. The first-order diffracted lights a1 and a4 are distributed on the photodetector apart from each other.
Description
Technical field
The present invention relates to be used for be recorded in the optical disc apparatus and the light-dividing device of the signal on the CD in tracer signal on the CD or reproduction.
Background technology
For example, Japanese documentation JP2000-133929A has introduced a kind of prior art.The technology of describing based on this piece patent and having done partly to revise below with reference to Fig. 9 and 10B.Fig. 9 has shown the cross-sectional structure according to the optical disc apparatus of prior art example, comprises the side view of radiation light source 1 and near its structure, and described side view is added to the below of the figure of show cross section plane structure.In Fig. 9, be installed in light such as semiconductor laser etc. and detect laser beam that the radiation light source 1 on the substrate 9 sends and be installed in light and detect catoptron 10 reflections on the substrate 9, and converted to directional light by collimation lens 4.This directional light converts circularly polarized light by polarization holography substrate 2 and from linearly polarized photon (S ripple or P ripple) to by quarter-wave plate 3, is concentrated by object lens 5 then to focus on the signal face 6a of compact disc substrate 6.The light that is reflected by signal face 6a passes through object lens 5, and be converted into linearly polarized photon (P ripple or S ripple) by quarter-wave plate 3, enter the holographic facet 2a of polarization holography substrate 2 inside then, diffracted and be branched off into first-order diffraction light 8 and negative first-order diffraction light 8 ', this first-order diffraction light 8 and negative first-order diffraction light 8 ' are mutually symmetrical with respect to the optical axis 7 that is used as axis of symmetry.First-order diffraction light 8 and negative first-order diffraction light 8 ' pass collimation lens 4, thereby different diffraction lights becomes converging light, incide on the detection faces 9a on the light detection substrate 9.Quarter-wave plate 3 is set on the same substrate with holographic facet 2a, and with object lens 5 motions.Detection faces 9a roughly is arranged on the position, focal plane (just radiating the virtual luminous point position of light source 1) of collimation lens 4.
Figure 10 A and 10B show the light detection faces of prior art example optical disk device and the structure of holographic facet respectively.In Figure 10 A and 10B, be to see light detection faces and holographic facet from CD one side.Point 20 is represented the intersection point of holographic facet 2a and optical axis 7.Holographic facet 2a is divided into four quadrants by two at point 20 straight lines that are perpendicular to one another (X-axis and Y-axis).And each quadrant is divided into bar- shaped zone 21B, 21F, 22B, 22F, 23B, 23F, 24B and 24F along X-axis.
On the other hand, 90 is intersection points of optical axis 7 and detection faces 9a.Article two, be perpendicular to one another and the straight line that is parallel to X-axis and Y-axis respectively is represented as x axle and y axle at point 90.Comb teeth shape focus detection device F1a, F2a, F1b, F2b, F1c, F2c, F1d, F2d, F1e and F2e are set at the positive side of y axle along the y axle.Trapezoidal tracking detecting element 7T1,7T2,7T3 and 7T4 are set at y axle minus side.These detecting elements are being configured to the rotational symmetry with respect to y in shape.Vertical with paper and run through in the plane of x axle and propagate along the direction parallel with the x axle, and the mirror 10 that is reflected reflects along the optical axis direction direction of paper and crossing point 90 (just perpendicular to) from the light that sends of luminous point 1a of radiation light source 1.
Be focused on hot spot 81BS and the 81FS by zone 21B of the comb teeth shape in the first quartile of holographic facet 2a and diffracted first-order diffraction light 81B and the 81F of 21F, above-mentioned hot spot 81BS and 81FS are formed on respectively on the border of striding between detecting element F2a and the F1b, negative first-order diffraction light 81B ' and 81F ' are focused on hot spot 81BS ' and the 81FS ', and this hot spot 81BS ' and 81BF ' are formed on separately on the detecting element 7T1 respectively; Be focused on hot spot 82BS and the 82FS by zone 22B of the comb teeth shape in second quadrant and diffracted first-order diffraction light 82B and the 82F of 22F, this hot spot 82BS and 82FS are formed on respectively on the border of striding between detecting element F1b and the F2b, negative first-order diffraction light 82B ' and 82F ' are focused on hot spot 82BS ' and the 82FS ', and this hot spot 82BS ' and 82FS ' are formed on separately on the detecting element 7T2 respectively; Be focused on hot spot 83BS and the 83FS by zone 23B of the comb teeth shape in the third quadrant and diffracted first-order diffraction light 83B and the 83F of 23F, this hot spot 83BS and 83FS are formed on respectively on the border of striding between detecting element F1d and the F2d, negative first-order diffraction light 83B ' and 83F ' are focused on hot spot 83BS ' and the 83FS ', and this hot spot 83BS ' and 83FS ' are formed on separately on the detecting element 7T3 respectively; Be focused on hot spot 84BS and the 84FS by zone 24B of the comb teeth shape in the four-quadrant and diffracted first-order diffraction light 84B and the 84F of 24F, this hot spot 84BS and 84FS are formed on respectively on the border of striding between detecting element F2d and the F1e, negative first-order diffraction light 84B ' and 84F ' are focused on hot spot 84BS ' and the 84BF ', and this hot spot 84BS ' and 84BF ' are formed on separately on the detecting element 7T4 respectively.Because first-order diffraction light 81B, 82B, 83B and 84B are focused on the dorsal part of detection faces 9a (just away from holographic facet 2a a side), are formed on the light that the hot spot distributional class on the detection faces 9a is similar on the holographic facet 2a and distribute.Because negative first-order diffraction light 81B ', 82B ', 83B ' and 84B ' are focused on the front side of detection faces 9a (just near holographic facet 2a a side), the hot spot distributional class that is formed on the detection faces 9a is similar to the light distribution that distributes and obtains by with respect to the light on the point 20 counter-rotating holographic facet 2a.Because first-order diffraction light 81F, 82F, 83F and 84F are focused on the front side of detection faces 9a, the hot spot distributional class that is formed on the detection faces 9a is similar to the light distribution that distributes and obtain by with respect to the light on the point 20 counter-rotating holographic facet 2a.In addition, because negative first-order diffraction light 81F ', 82F ', 83F ' and 84F ' are focused on the rear side of detection faces 9a, are formed on the light that the hot spot distributional class on the detection faces 9a is similar on the holographic facet 2a and distribute.
Some detecting elements are conducted, thereby can obtain following six signals.
The signal that the signal that the signal that the signal that the signal that F1=detecting element F1a obtains+detecting element F1b obtains+detecting element F1c obtains+detecting element F1d obtains+detecting element F1e obtains
The signal that the signal that the signal that the signal that the signal that F2=detecting element F2a obtains+detecting element F2b obtains+detecting element F2c obtains+detecting element F2d obtains+detecting element F2e obtains
The signal that T1=detecting element 7T1 obtains
The signal that T2=detecting element 7T2 obtains
The signal that T3=detecting element 7T3 obtains
The signal that T4=detecting element 7T4 obtains
In Figure 10 A and 10B, the y axle is represented CD 6 radially, detect according to following formula the focus error signal FE that is illustrated in the focused light error on the CD signal face, expression tracking illumination disk track error magnetic track error signal TE and from the reproduced reproducing signal RF of CD signal face.
FE＝F1-F2 (1)
TE＝T1+T2-T3-T4 (2)
RF＝F1+F2+T1+T2+T3+T4 (3)
This general optical disc device has following problems.Usually can be with the equation expression of suitable coefficient a of following use and b according to the TE signal of formula 2, Δ representative this moment is with respect to the magnetic track bias of CD magnetic track, and δ represents object lens 5 and the deviation of polarization holography substrate 2 on radially (Y direction just) of coiling.
TE＝aΔ+bδ (4)
Just in the prior art example, when the TE detection signal that uses according to formula 2, because the object lens 5 of motion and polarization holography substrate 2 produce deviation (under tracking Control, producing this deviation inevitably) in disc radial direction together, therefore shift phenomenon takes place.Why signal TE is that the reason of function of δ is as follows: because object lens 5 and holographic substrate 2 deviation diametrically, cause the intensity distributions of the back light 80 on holographic facet 2a asymmetric from the uneven intensity distributions of the light that sends of radiation light source 1 with respect to X-axis, the uneven intensity distributions that above-mentioned radiation light source 1 sends light is meant in the position intensity near optical axis big, far away more apart from optical axis distance, intensity is more little.(optical depth D for example is λ/6 for having dark guide groove, the wavelength of λ representative radiation light source wherein) and the CD such as DVD-RAM of wide spacing (for example flute pitch Λ approximately is 1.21～1.48 μ m), because the diffraction effect that groove produced makes the intensity distributions of back light 80 on holographic facet 2a roughly even on Y direction, therefore coefficient b approximately is 0 (just b=0) haply, and this can not cause any problem.Yet for CD such as DVD-R, DVD-RW with shallow guide groove (optical depth D for example is λ/10～λ/20) and thin space (for example flute pitch Λ approximately is 0.74m), because the asymmetry of back light 80 variation, coefficient b is not equal to 0 (b ≠ 0 just).
Usually carrying out tracking Control is 0 (TE=0 just) so that make signal TE.Therefore when b ≠ 0, be according to the magnetic track bias of formula 4 generations:
Δ＝-bδ/a (5)
As example, for the dish of the flute pitch Λ of depth of groove D with λ/12 and 0.74 μ m, b/a is approximately 2.4/10000, and when δ=200 μ m, magnetic track bias Δ is 0.048 μ m.This amount is very big, is that the dish of 0.74 μ m can not be ignored for track pitch.This will produce, and magnetic track is omitted, the reproducing signal variation, influences problems such as adjacent track signal when record.
Summary of the invention
In order to solve above-mentioned problems of the prior art, the purpose of this invention is to provide a kind of optical disc apparatus, even wherein when object lens and holographic substrate depart from diametrically, also can under tracking Control, not produce magnetic track and depart from.Another object of the present invention provides a kind of optical disc apparatus and light-dividing device, and the two can be handled two simultaneously and is arranged on light adjacent to each other and detect on-chip radiation light source.
To achieve these goals, first optical disc apparatus of the present invention comprises radiation light source, object lens, an optical splitter and a photodetector, and wherein, the light that sends from described radiation light source passes described object lens and is focused on the signal face of CD; The light that is reflected by this signal face passes described object lens and enters described optical splitter; Described optical splitter is divided into four quadrant Ak (k=1,2,3,4) by two with the straight line of optical axis intersection (a y axle parallel with disc radial direction, an x axle vertical with disc radial direction); Described photodetector is divided at least 4 area B k; First-order diffraction light ak, and is projected on the Bk zone of described photodetector under the effect of described optical splitter and derive from respectively by the light that enters all quadrants Ak; The section that first-order diffraction light a2 and a3 are done along the x axle is roughly on the border between area B 2 and the B3; First-order diffraction light a1 and a4 are distributed on the described photodetector with being separated from each other.
Preferably produce the tracking error signal TE of CD according to formula TE=C1-C4-(C2-C3)/m, Ck representative detected signal (k=1,2,3,4) in area B k wherein, m represent 1 or bigger value.
Preferably, negative first-order diffraction light ak ' (k=1,2,3,4) by the light that enters all quadrants Ak under the effect of described optical splitter and derive from respectively; Negative first-order diffraction light a2 ' is focused on the described detection faces, does not reverse with respect to the y direction of principal axis; Negative first-order diffraction light a3 ' reverses with respect to the y direction of principal axis and is focused on the detection faces.
Second optical disc apparatus according to the present invention comprises the first radiation light source, the second radiation light source, object lens, an optical splitter and a photodetector, and wherein, the described first radiation light source and the second radiation light source are set on the described photodetector; Pass described object lens and be focused on the signal face of first CD from described first light that sends of radiation light source; The light that is reflected by this signal face passes object lens and enters described optical splitter; Described optical splitter is divided into four quadrant Ak (k=1,2,3,4) by two with the straight line of optical axis intersection (a y axle parallel with disc radial direction, an x axle vertical with disc radial direction); Described photodetector is divided at least 4 area B k; First-order diffraction light ak, and is projected on the Bk zone of described photodetector under the effect of described optical splitter and derive from respectively by the light that enters all quadrants Ak; Send and have and pass described object lens from first light that radiates the light different wave length that light source sends and be focused on the signal face of second CD from the described second radiation light source; Light by the reflection of the signal face of this second CD passes described object lens and enters described optical splitter; Under the effect of described optical splitter and derive from respectively, and described first-order diffraction light bk is projected respectively on the Bk zone of described photodetector first-order diffraction light bk by the light that enters all quadrants Ak.
The section that first-order diffraction light a2 and a3 or b2 and b3 are done along the x axle is preferred roughly on the border between area B 2 and the B3, and first-order diffraction light a1 and a4 or b1 and b4 are distributed on the described photodetector with being separated from each other.
Preferably produce the tracking error signal TE of first or second CD according to formula TE=C1-C4-(C2-C3)/m, Ck representative detected signal (k=1,2,3,4) in area B k wherein, m represent 1 or bigger value.
Preferred negative first-order diffraction light ak ' or bk ' (k=1,2,3,4) by the light that enters all quadrants Ak under the effect of described optical splitter and derive from respectively, negative first-order diffraction light a2 ' or b2 ' are focused on the detection faces and do not reverse with respect to the y direction of principal axis, and negative first-order diffraction light a3 ' or b3 ' reverse with respect to the y direction of principal axis and be focused on the described detection faces.
In addition, each all comprises the first radiation light source, the second radiation light source, object lens, an optical splitter and a photodetector according to a kind of optical disc apparatus of the present invention and optical splitter, wherein, described optical splitter has following structure, and just it has one and has the periodically birefringent medium of convex-concave xsect; Send and wavelength is that the light of λ 1 enters described optical splitter from the described first radiation light source, and periodically converted to the light that phase differential approximately is 2n π (n represents the integer outside 0); Above-mentioned light passes described object lens and is focused on the signal face of first CD; The light that is reflected by this signal face passes described object lens, enter described optical splitter then, and periodically converted to the light that phase differential approximately is 2n π+α (α represents the real number outside 0), and enter described photodetector and detected by the diffraction light that above-mentioned light derives from; Send and wavelength is that the light of λ 2 enters described optical splitter from the second radiation light source, and periodically converted to the light that phase differential approximately is 2n π λ 1/ λ 2; Above-mentioned light passes described object lens and is focused on the signal face of second CD; Light by the signal face of described second CD reflection passes described object lens, enters described optical splitter then, and periodically to be converted to phase differential approximately be (the light of λ 1/ λ 2 of 2n π+α); The diffraction light that is derived from by above-mentioned light enters described photodetector and detected.
Utilize said structure, the magnetic track that takes place under tracking Control departs from and can be eliminated.And,, use identical photodetector can detect, and the magnetic track that takes place under tracking Control departs from and can be eliminated corresponding to control signal and reproducing signal from the emission bright dipping of different radiating lights source for structure with two adjacent radiation light sources.Especially under the situation with respect to a radiation light source, be used in appointment under any birefringence situation of compact disc substrate, diffraction efficiency can not be 0 all the time, thereby can detect CD signal reliably.
Description of drawings
Fig. 1 is the cut-open view that shows according to the CD device structure of the embodiment of the invention 1;
Fig. 2 A and 2B show respectively according to the detection faces of the optical disc apparatus of the embodiment of the invention 1 and the structure of holographic facet;
When Fig. 3 A～3C shows when focus is focused on according to the CD signal face of the embodiment of the invention 1 on, be positioned at before the photodetector of the xsect of doing along optical axis and the position of focus afterwards; Fig. 3 A has shown first-order diffraction light 81B, 84B, 81F and 84F and negative first-order diffraction light 81B ', 84B ', 81F ' and 84F '; Fig. 3 B has shown first-order diffraction light 82 and negative first-order diffraction light 82 '; Fig. 3 C has shown first-order diffraction light 83 and first-order diffraction light 83 ';
Fig. 4 A and 4B are light check pattern and the distribution mode of light on this pattern and the views of holographic photography pattern that shows respectively according to the embodiment of the invention 2;
Fig. 5 is the cut-open view that shows according to the CD device structure of the embodiment of the invention 3;
Fig. 6 is the cut-open view that shows according to the structure of the polarization holography graph 2 of the embodiment of the invention 3 and quarter-wave plate 3;
Fig. 7 A is the cut-open view of demonstration according to the structure of another routine polarization holography graph of the embodiment of the invention 3, and Fig. 7 B is the cut-open view of demonstration according to the structure of the another routine polarization holography graph of the embodiment of the invention 3.
Fig. 8 A and 8B are respectively the views that shows according to the light check pattern and the distribution mode of light on this pattern of the embodiment of the invention 3;
Fig. 9 is the cut-open view of a demonstration according to the CD device structure of prior art example;
Figure 10 A and 10B show respectively according to the detection faces of the optical disc apparatus of prior art example and the structure of holographic facet.
Embodiment
The invention is characterized in, the light that sends from irradiation radiation light source is focused on the signal face of optical disc apparatus by object lens, the light that is reflected by signal face is divided into four by one, wherein two strands of light are separated, the joint of two strands of light between a plurality of photodetectors in addition, detect the differential signal of every pair of light, calculate these differential signals, so that detect tracking error (TE) signal.Thus, the present invention can provide a kind of optical disc apparatus, even wherein object lens and the upwards skew in the footpath of coiling of polarization holography substrate the magnetic track deviation can not occur yet under tracking Control.In addition, the present invention can provide a kind of optical disc apparatus and optical splitter, handles two simultaneously and is arranged on light adjacent to each other and detects on-chip radiation light source.
Hereinafter introduce embodiments of the invention 1 in conjunction with Fig. 1～3C.Components identical uses the same reference numerals to represent in embodiment 1 and prior art example.Fig. 1 has shown the cross-sectional structure according to the optical disc apparatus of embodiment 1, and comprise emission radiation light source 1 with and a near side view, this side view is set at the view below that shows above-mentioned cross-sectional structure.In Fig. 1, detect laser beam that the radiation light source 1 on the substrate 9 sends and be installed in light and detect catoptron 10 reflections on the substrate 9 from be installed in light such as semiconductor laser etc., and converted to directional light by collimation lens 4.This directional light passes through a polarization holography substrate 2 as optical splitter, and converts circularly polarized light from linearly polarized photon (S ripple or P ripple) to by quarter-wave plate 3, is assembled by object lens 5 so that focus on the signal face 6a of compact disc substrate 6 then.The light that is reflected by signal face 6a passes through object lens 5, convert linearly polarized photon (P ripple or S ripple) to by quarter-wave plate 3, enter the holographic facet 2a in the holographic substrate 2 then, diffracted and be branched off into first-order diffraction light 8 and the negative first-order diffraction light 8 ' that is mutually symmetrical with respect to the optical axis 7 that is used as axis of symmetry.First-order diffraction light 8 and negative first-order diffraction light 8 ' are by collimation lens 4, thereby each diffraction light becomes converging light, incide then on the detection faces 9a on the light detection substrate 9.Quarter-wave plate 3 is set on the identical substrate with holographic facet 2a, and with object lens 5 motions.Detection faces 9a roughly is positioned at the position (just radiating the virtual luminous point position of light source 1) of the focal plane of collimation lens 4.In holographic photography Fig. 2, the diffracting effect of back light for example is 0 grade of light 0%, positive and negative one-level light 41%.
Fig. 2 A and 2B show respectively according to the light detection faces of the optical disc apparatus of the embodiment of the invention 1 and the structure of holographic facet.In Fig. 2 A and 2B, be to observe light detection faces and holographic facet from the CD side.Point 20 is represented the intersection point of holographic facet 2a and optical axis 7.Holographic facet 2a is divided into four quadrants by two at point 20 straight lines that are perpendicular to one another (X-axis and Y-axis line).And first quartile and four-quadrant are divided into bar- shaped zone 21B, 21F, 24B and 24F along X-axis, second and third quadrant be expressed as respectively the zone 22 and 23.
On the other hand, 90 is intersection points of detection faces 90a and optical axis 7.Article two, be perpendicular to one another and the straight line that is parallel to X-axis and Y-axis respectively is represented as x axle and y axle at point 90.Comb teeth shape focus detection device F1a, F2a, F1b, F2b, F1c and F2c are set on the positive side of y axle along the y axle.Rectangle is followed the tracks of detecting element 7T1,7T2,7T3 and 7T4 and is set on the minus side of y axle, and these detecting elements are set in shape with respect to the y rotational symmetry.Perpendicular to paper and penetrate in the plane of x axle and propagate along the direction that is parallel to the x axle, the mirror 10 that is reflected then is in the optical axis direction direction of the paper by point 90 (just perpendicular to) reflection from the light that sends of luminous point 1a of radiation light source 1.
By the comb teeth shape in the first quartile of holographic facet 2a zone 21B and 21F and diffracted first-order diffraction light 81B and 81F is focused on respectively on hot spot 81BS and the 81FS, described hot spot 81BS and 81FS are formed on respectively on the border of striding between detecting element F2a and the F1b, and negative first-order diffraction light 81B ' and 81F ' are focused on respectively on the hot spot 81BS ' and 81FS ' that is formed on separately on the detecting element 7T1.Diffracted first-order diffraction light 82 and negative first-order diffraction light 82 ' is focused on respectively on hot spot 82S and the 82S ' by second quadrant area 22, hot spot 82S is formed on the border of striding between detecting element F1b and the F2b, and hot spot 82S ' is formed on separately on the detecting element 7T2; Diffracted first-order diffraction light 83 and negative first-order diffraction light 83 ' is focused on respectively on hot spot 83S and the 83S ' by third quadrant zone 23, hot spot 83S is formed on the border of striding between detecting element F1b and the F2b, and hot spot 83S ' is formed on separately on the detecting element 7T3; By the comb teeth shape in four-quadrant zone 24B and 24F and diffracted first-order diffraction light 84B and 84F is focused on respectively on hot spot 84BS and the 84FS, described hot spot 84BS and 84FS are formed on respectively on the border of striding between detecting element F2b and the F1c, and negative first-order diffraction light 84B ' and 84F ' are focused on respectively on the hot spot 84BS ' and 84FS ' that is formed on separately on the detecting element 7T4.
Fig. 3 A～3C shows and is positioned at when the focus on the CD signal face 6a is focused before the photodetector plane 9a of the xsect of doing according to the optical axis of the embodiment of the invention 1 and the position of focus afterwards; Fig. 3 A has shown first-order diffraction light 81B, 84B, 81F and 84F and negative first-order diffraction light 81B ', 84B ', 81F ' and 84F '; Fig. 3 B has shown first-order diffraction light 82 and negative first-order diffraction light 82 '; Fig. 3 C has shown first-order diffraction light 83 and first-order diffraction light 83 '.Be focused on detection faces 9a corresponding to 0 order diffraction element of every bundle diffraction light and go up on the point 90, but in practice,, therefore do not produce optical radiation because 0 order diffraction diffraction of light efficient is 0 basically.
As shown in Figure 3A, pass the diffraction light 80 of holographic facet 2a with respect to diffraction, respectively first and the diffracted first-order diffraction light 81B of four-quadrant and 84B be focused on apart from detection faces 9a dorsal part distance on the some 8B of L1, negative first-order diffraction light 81B ' and 84B ' are focused on apart from detection faces 9a front side distance and go up (path of light is represented with solid line) for the some 8B ' of L1.In addition, pass the diffraction light 80 of holographic facet 2a with respect to diffraction, respectively first and the diffracted first-order diffraction light 81F of four-quadrant and 84F be focused on apart from detection faces 9a front side distance on the some 8F of L2, negative first-order diffraction light 81F ' and 84F ' are focused on apart from detection faces 9a dorsal part distance and go up (path of light is represented with solid line) for the some 8F ' of L2.Distance L 2 and L1 are about equally.
Shown in Fig. 3 B, pass the diffraction light 80 of holographic facet 2a with respect to diffraction, diffraction passes the focus of first-order diffraction light 82 of second quadrant in the xsect that is parallel to paper and differs from one another perpendicular to paper.In the xsect perpendicular to paper, first-order diffraction light 82 is focused on apart from detection faces 9a dorsal part and goes up (this bundle diffraction light is represented as 82X) apart from the some 82x for L1.In being parallel to the xsect of paper, first-order diffraction light is focused on apart from detection faces 9a dorsal part and goes up (this bundle diffraction light is represented as 82Y) apart from the some 82y for L3.On the other hand, diffraction passes the focus of negative first-order diffraction light 82 ' of second quadrant in the xsect that is parallel to paper and differs from one another perpendicular to paper.In the xsect perpendicular to paper, first-order diffraction light 82 ' is focused on apart from detection faces 9a front side and goes up (this bundle diffraction light is represented as 82X ') apart from the some 82x ' for L1.In being parallel to the xsect of paper, first-order diffraction light 82 ' is focused on apart from detection faces 9a front side and goes up (this bundle diffraction light is represented as 82Y ') apart from the some 82y ' for L3.
Shown in Fig. 3 C, pass the diffraction light 80 of holographic facet 2a with respect to diffraction, diffraction passes the focus of first-order diffraction light 83 of third quadrant in the xsect that is parallel to paper and differs from one another perpendicular to paper.In the xsect perpendicular to paper, first-order diffraction light 83 is focused on apart from detection faces 9a front side and goes up (this bundle diffraction light is represented as 83X) apart from the some 83x for L1.In being parallel to the xsect of paper, first-order diffraction light 83 is focused on apart from detection faces 9a dorsal part and goes up (this bundle diffraction light is represented as 83Y) apart from the some 83y for L3.On the other hand, diffraction passes the focus of negative first-order diffraction light 83 ' of third quadrant in the xsect that is parallel to paper and differs from one another perpendicular to paper.In the xsect perpendicular to paper, first-order diffraction light 83 ' is focused on apart from detection faces 9a dorsal part and goes up (this bundle diffraction light is represented as 83X ') apart from the some 83x ' for L1.In being parallel to the xsect of paper, first-order diffraction light 83 ' is focused on apart from detection faces 9a front side and goes up (this bundle diffraction light is represented as 83Y ') apart from the some 83y ' for L3.
With reference to figure 2,3A, 3B and 3C,, be formed on the light that the hot spot on the detection faces 9a is similar in form on holographic facet 2a and distribute because first-order diffraction light 81B and 84B are focused on detection faces 9a dorsal part (just from a holographic facet 2a side far away).Because negative first-order diffraction light 81B ' and 84B ' are focused on detection faces 9a front side (side of close holographic facet 2a just), the hot spot that is formed on the detection faces 9a is similar in form by the distribution of the light on the holographic facet 2a is distributed with respect to the light that point 20 counter-rotatings obtain.Because first-order diffraction light 81F and 84F are focused on detection faces 9a front side, the hot spot that is formed on the detection faces 9a is similar to the light distribution that obtains with respect to point 20 counter-rotatings by the light on the holographic facet 2a is distributed in form.Because negative first-order diffraction light 81F ' and 84F ' are focused on the dorsal part of detection faces 9a, are formed on the light that the hot spot on the detection faces 9a is similar in form on holographic facet 2a and distribute.And, because first-order diffraction light 82 is focused in the xsect that is being parallel to paper with perpendicular to the dorsal part of the detection faces 9a in the xsect of paper, is formed on hot spot on the detection faces 9a and is similar to the light that obtains by distributing in form and distributes along the light on the Y direction expansion holographic facet 2a.Because negative first-order diffraction light 82 ' is focused in the xsect that is being parallel to paper with perpendicular to the front side of the detection faces 9a in the xsect of paper, is formed on hot spot on the detection faces 9a and is similar in form by the light on the holographic facet 2a being distributed with respect to point 20 counter-rotatings and the light distribution that obtains along the expansion of Y direction.In addition, because first-order diffraction light 83 is focused in the xsect that is being parallel to paper with perpendicular to the front side of the detection faces 9a in the xsect of paper, is formed on hot spot on the detection faces 9a and is similar in form by the light on the holographic facet 2a being distributed around Y-axis counter-rotating and the light distribution that obtains along the expansion of Y direction.Because negative first-order diffraction light 83 ' is focused in perpendicular to the dorsal part of the detection faces 9a in the xsect of paper be parallel to the front side of the detection faces 9a in the xsect of paper, is formed on hot spot on the detection faces 9a and is similar to light distribution in form by the light on the holographic facet 2a being distributed relative X-axis counter-rotating and obtaining along the expansion of Y direction.Whole hot spot 81BS ' and 81FS ' and whole hot spot 84BS ' and 84FS ' are formed on respectively in photodetector 7T1 and the 7T4.Yet hot spot 82S ' and 83S ' are connected to each other at the y direction of principal axis, connection between the two roughly with photodetector 7T2 and 7T3 between separator bar overlap, this is a specific character.In addition, another kind of characteristic is, the light on the Y-axis line counter-rotating holographic facet 2a distributes and forms the shape of hot spot 82S relatively, and the light on the Y-axis line counter-rotating holographic facet 2a distributes and forms the shape of hot spot 83S relatively.
Some photodetectors are conducted, and therefore, can obtain following 6 signals.
The signal that is obtained in the signal+detecting element F1c that is obtained in the signal+detecting element F1b that is obtained in the F1=detecting element F1a
The signal that is obtained in the signal+detecting element F2c that is obtained in the signal+detecting element F2b that is obtained in the F2=detecting element F2a
The signal that is obtained in the T1=detecting element 7T1
The signal that is obtained in the T2=detecting element 7T2
The signal that is obtained in the T3=detecting element 7T3
The signal that is obtained in the T4=detecting element 7T4
In Fig. 2 A and 2B, the y axle is represented CD 6 radially, according to following various detection represent focused light at the focus error signal FE of the error on the CD signal face, be illustrated in the tracking error signal TE of the error on the tracking illumination disk track and the reproducing signal RF that reproduces from the CD signal face:
FE＝F1-F2 (6)
TE＝(T1-T4)-(T2-T3)/m (7)
RF＝F1+F2+T1+T2+T3+T4 (8)
Usually, when on CD, occurring defocusing, depend on the relative position relation between the focus of light detection faces 9a and each hot spot in the mode that forms hot spot on the light detection faces.The FE signal relies on the shape of hot spot on the X-direction especially.Shown in Fig. 3 A～3C, this shape depends on that light detection faces 9a and each hot spot are perpendicular to the relative position relation between the focus in the xsect of paper.
In the prior art example, when defocusing on CD, hot spot 82FS and 83BS and hot spot 83FS and 82BS adopt same way as to be formed.Therefore, even without forming hot spot 82FS and 83BS, the identical characteristic of characteristic that signal FE is obtained when having with formation hot spot 82FS and 83BS.In example 1, the width on the x direction of principal axis such as hot spot 81BS is identical in hot spot 81BS, 81FS, 82S, 83S, 84BS and the 84FS width on the x direction of principal axis and the prior art example.When defocusing on CD, hot spot 81BS, 81FS, 84BS and 84FS adopt the mode identical with the prior art example to form.Therefore, owing to light detection faces 9a with identical (just with respect to hot spot 82BS and 83FS perpendicular to the relation of the position between the focus in the xsect of paper, hot spot 82S and 83S expand on the y direction of principal axis, but depend on their width on the x direction of principal axis owing to relate to the mode of FE detection, the characteristic of FE signal does not change), so the generation type of hot spot 82BS in the generation type of hot spot 82S and 83S and the prior art example and 83FS is identical.Thereby the characteristic of the interior FE signal of the characteristic of FE signal and prior art example is identical in the example 1.
With respect to the magnetic track deviation, signal (T1-T4) and signal (T2-T3) are substantially the same each other, but they also have different characteristics.For example signal (T1-T4) can be represented by employed coefficient a and b in the following formula employing prior art example, wherein Δ representative departs from quantity with respect to the magnetic track of CD magnetic track, and the δ representative is gone up object lens 5 and and the deviation of the polarization holography substrate 2 that moves together of object lens 5 in radially (Y direction just) of dish.
T1-T4＝aΔ+bδ (9)
On the other hand, signal (T2-T3) can be used following formulate:
T2-T3＝aΔ+b’δ (10)
Signal (T1-T4) is that the reason of function of δ is as follows: identical with the prior art example, because object lens 5 and holographic substrate 2 deviation diametrically, the uneven intensity distributions of sending light from radiation light source 1 causes the intensity distributions of the back light 80 on holographic facet 2a asymmetric with respect to X-axis, above-mentioned uneven intensity distributions is meant in the position intensity near optical axis big, far away more apart from optical axis distance, intensity is more little.On the other hand, except back light 80 the on-chip intensity distributions of holography is asymmetric with respect to X-axis, be offset diametrically corresponding to object lens 5 and polarization holography substrate 2, hot spot on the detection faces 9a moves on the y axle, thereby signal (T2-T3) relies on the reason of δ and the reason different (b ≠ b ' herein) of signal (T1-T4) dependence δ.Just because hot spot 81BS ' and 81FS ' and 84BS ' and 84FS ' are formed in photodetector 7T1 and the 7T4 the mobile variation (with prior art example identical) that do not cause light quantity of hot spot on the y axle respectively.Yet hot spot 82S ' links to each other on the y direction of principal axis with 83S ', connection between the two approximate with photodetector 7T2 and 7T3 between separator bar overlap.Therefore, when these hot spots are mobile together on the y axle, the change of light quantity appears on described separator bar both sides.
(optical depth D for example is λ/6 having dark guide groove, the wavelength of λ representative radiation light source wherein) and under the situation such as the CD of DVD-RAM of wide spacing (for example flute pitch Λ approximately is 1.21～1.48 μ m), because diffraction effect that groove produced makes the intensity distributions of back light 80 on holographic facet 2a roughly even on Y direction, coefficient b approximately is 0 (just b=0) haply.In the case, as Coefficient m=∞, TE=(T1-T4) just, under tracking Control (TE=0), the magnetic track deviation quantity is 0.
Under CD situation such as DVD-R, DVD-RW with shallow guide groove (optical depth D for example is λ/10～λ/20) and thin space (for example flute pitch Λ approximately is 0.74 μ m), because the asymmetry of back light 80 variation, coefficient b is not equal to 0 (b ≠ 0 just), satisfy formula m=b/b ' if the Coefficient m in the formula 7 is set, then from formula 7,9 and 10, obtain following formula:
TE＝(1-1/m)aΔ (11)
Therefore object lens 5 and almost ideally eliminated with the influence of the deviation δ of the polarization holography substrate 2 of object lens 5 motions.Even there is deviation δ, under tracking Control (TE=0), do not produce track skew (just being 0).
The value of coefficient ratio b/b ' depends on the groove shapes of optical system and CD basically.Under CD situation such as DVD-R and DVD-RW, coefficient b than b ' larger about 2～4.In the above-described embodiments, hot spot 82S ' and 83S ' are described as be in the point that is connected with each other on the y axle.Yet, even moving on the x direction of principal axis, these hot spots are separated from each other, eliminating also not variation in the deviation δ influence.When the position of luminous point 1a was mobile on the y direction of principal axis, the tie point between hot spot 82S ' and the 83S ' departed from the separator bar 7Ta between photodetector 7T2 and the 7T3.Therefore, this bias is added on the signal (T2-T3), but by preliminary research, the influence of this composition can be eliminated.In addition, even move on the y direction of principal axis position of luminous point 1a, because hot spot 82S ' and 83S ' extend along the y direction of principal axis, the ratio of bias and spot diameter can be maintained very little, thereby the increase surplus of this deviation is provided.This is external has above introduced the position, focal plane that detection faces 9a is positioned at collimation lens 4, but its also can be positioned at this focal plane near.Among this external embodiment 1, radiation light source and photodetector are set on the same substrate, but also can be separated to be provided with.
Introduce embodiments of the invention 2 below in conjunction with Fig. 4 A and 4B.Except the pattern of holographic facet 2a, check pattern on the 9a of photodetector plane and the light on it distributed, embodiment 2 was identical with embodiment 1.Omitted introduction herein with embodiment 1 same section.In introducing hereinafter, use identical Reference numeral to represent 1 components identical with embodiment.Fig. 4 A and 4B show light check pattern and light distribution mode on this pattern and the holographic photography pattern in the embodiment 2 respectively, wherein are to see light detection faces (Fig. 4 A) and holographic facet (Fig. 4 B) from CD one side.
With the intersection point that point 20 is represented holographic facet 2a and optical axis 7, holographic facet 2a is divided into four quadrants by two at point 20 straight lines that are perpendicular to one another (X-axis and Y-axis).First, second, third and four-quadrant be represented as regional 21B, zone 22, zone 23 and regional 24F respectively.
The intersection point of representing light detection faces 9a and optical axis 7 with point 90.Be perpendicular to one another and two straight lines being parallel to X-axis and Y-axis are represented as x axle and y axle at point 90.Comb teeth shape focal length detecting element F1a, F2a, F1b, F2b, F1c and F2c are set at the positive side of y axle along the y axle.Rectangle is followed the tracks of the minus side that detecting element 7T1,7T2,7T3 and 7T4 are set at the y axle.Detecting element is set to shape with respect to the y rotational symmetry.Perpendicular to paper and run through in the plane of x axle and propagate along the direction that is parallel to the x axle, the mirror 10 that is reflected then is along the optical axis direction direction of the paper by point 90 (just perpendicular to) reflection from the light that sends of luminous point 1a of radiation light source 1.
Diffracted first-order diffraction light 81B and negative first-order diffraction light 81B ' is focused on respectively on hot spot 81BS and the 81BS ' by the first quartile 21B of holographic facet 2a, described hot spot 81BS is formed on the border of striding between detecting element F2a and the F1b, and hot spot 81BS ' is formed on separately on the detecting element 7T1; Diffracted first-order diffraction light 82 and negative first-order diffraction light 82 ' is focused on respectively on hot spot 82S and the 82S ' by second quadrant area 22, hot spot 82S is formed on the border between detecting element F1b and the F2b, and hot spot 82S ' is formed on separately on the detecting element 7T2; Diffracted first-order diffraction light 83 and negative first-order diffraction light 83 ' is focused on respectively on hot spot 83S and the 83S ' by third quadrant zone 23, hot spot 83S is formed on the border of striding between detecting element F1b and the F2b, and hot spot 83S ' is formed on separately on the detecting element 7T3; Diffracted first-order diffraction light 84F and negative first-order diffraction light 84F ' is focused on respectively on hot spot 84FS and the 84FS ' by four-quadrant 24F, described hot spot 84FS is formed on the border of striding between detecting element F2b and the F1c, and hot spot 84FS ' is formed on detecting element 7T4 separately.
When the focus on the signal face 6a of CD is focused, before the photodetector in the xsect of doing along optical axis with afterwards focal position and embodiment 1 in identical, and identical with shown in Fig. 3 A～3C, except first-order diffraction light 81F and 84B and negative first-order diffraction light 81F ' and 84B '.Therefore Fig. 3 A is corresponding to the situation of the first-order diffraction light 81B in the present embodiment and 84F and negative first-order diffraction light 81B ' and 84F ', Fig. 3 B is corresponding to the situation of first-order diffraction light 82 in the present embodiment and negative first-order diffraction light 82 ', and Fig. 3 C is corresponding to the situation of first-order diffraction light 83 in the present embodiment and negative first-order diffraction light 83 '.
When defocusing on CD, the hot spot 81FS among the embodiment 1 is identical with the generation type of hot spot 84FS and 81BS with the generation type of 84BS.Therefore even without forming hot spot 81FS and 84BS, the identical characteristic of characteristic that the FE signal is obtained when still having with formation hot spot 81FS and 84BS.Embodiment 2 has wherein omitted hot spot 81FS and 84BS corresponding to embodiment 1.Clearly, utilize the principle identical,, can obtain the effect identical with embodiment 1 with respect to object lens 5 and polarization holography substrate 2 skew diametrically with embodiment 1.
Introduce embodiments of the invention 3 below in conjunction with Fig. 5～7B.Except the luminous point quantity of radiation light source from one be increased to two, as the pattern of the structure of the polarization holography substrate 2 of optical splitter, polarization holography face 2a, pattern on the detector plane 9a and light thereon distribute improve, embodiment 3 is identical with embodiment 1.No longer embodiment 3 and embodiment 1 components identical are introduced herein, use identical Reference numeral to represent among the embodiment 3 and embodiment 1 components identical.
Fig. 5 has shown the xsect according to the compact disk structure of embodiment 3, and comprise emission radiation light source 1 with and near the side view at position, it is set at the below of the view that shows above-mentioned xsect.In Fig. 1, be installed in light and detect catoptron 10 reflections on the substrate 9 from be installed in first laser beam (wavelength X 1) that luminous point 1a that light detects the radiation light source 1 on the substrate 9 sends such as semiconductor laser etc., and converted to directional light by collimation lens 4.This directional light converts circularly polarized light by a polarization holography substrate 2 and from linearly polarized photon (S ripple or P ripple) to by quarter-wave plate 3, is assembled by object lens 5 so that focus on the signal face 6a of first compact disc substrate 6 then.The light that is reflected by signal face 6a passes through object lens 5, convert linearly polarized photon (P ripple or S ripple) to by quarter-wave plate 3, enter the holographic facet 2a in the holographic substrate 2 then, diffracted and be branched off into first-order diffraction light 8 and negative first-order diffraction light 8 ', diffraction light 8 and 8 ' is mutually symmetrical with respect to the optical axis 7 that is used as axis of symmetry.First-order diffraction light 8 and negative first-order diffraction light 8 ' are located each diffraction light at this and are become converging light by collimation lens 4, incide then on the detection faces 9a on the light detection substrate 9.Quarter-wave plate 3 is set on the identical substrate with holographic facet 2a, and with object lens 5 motions.Detection faces 9a roughly is positioned at the position (the virtual luminous point position of luminous point 1a just) of the focal plane of collimation lens 4.The diffracting effect of the back light that is provided by holographic facet 2a for example is to be approximately 0% under 0 grade of light situation and positive and negative one-level light 41%.
Radiation light source 1 can the emission wavelength light different with first laser beam wavelength.The catoptron 10 that second laser beam of sending from the second luminous point 1a ' that radiates light source 1 (wavelength X 2, λ 2＞λ 1) is installed on the light detection substrate 9 reflects, and is converted to directional light by collimation lens 4.This directional light converts elliptically polarized light by a polarization holography substrate 2 and from linearly polarized photon (S ripple or P ripple) to by quarter-wave plate 3, is assembled by object lens 5 so that focus on the signal face 6a ' of second compact disc substrate 6 ' then.Light by signal face 6a ' reflection passes through object lens 5, by quarter-wave plate 3, enter the holographic facet 2a in the holographic substrate 2, diffracted and be branched off into first-order diffraction light 11 and negative first-order diffraction light 11 ', this diffraction light 11 and 11 ' is mutually symmetrical with respect to the optical axis 7 ' that is used as axis of symmetry.First-order diffraction light 11 and negative first-order diffraction light 11 ' are by collimation lens 4, thereby each diffraction light becomes converging light, incide the detection faces 9a on the light detection substrate 9 then.Compact disc substrate 6 is a kind ofly to have the dish of low-birefringence such as DVD etc., and compact disc substrate 6 ' is a kind of dish that has high birefringence such as CD etc.
Fig. 6 has shown according to the polarization holography substrate 2 of embodiment 3 and the cross-sectional structure of quarter-wave plate.Polarization holography substrate 2 has following structure, and just it has one and is set at the transparent substrate 2A of (refractive index of transparent substrate 2A is represented as " na ") that has homogeneous refractive index and the birefringent medium 2B between the 2C.Is the grating of d at transparent substrate 2A in the face of forming the degree of depth on the surface of medium 2B.Being layered on substrate 2C as the quarter-wave plate 3 of quarter-wave plate that for wavelength is the light of λ 1 goes up on the surface away from medium 2B.On the direction with respect to X-axis and Y-axis angle at 45, quarter-wave plate 3 has its fast axle.Along optical propagation direction the Z axle is set, X-axis and Y-axis is set along the plane that is parallel to holographic facet 2a.The refractive index of medium 2B on x axle and y direction of principal axis used " nx " and " ny " expression respectively.In practice, these refractive indexes are respectively the functions of wavelength, but owing to the difference between them in visual～infra-red range is very little, can use same value to replace actual value.Fig. 6 has shown the grating trend along Y direction, but also can be along other direction.In addition, the output light 12a that sends from each luminous point (from the light of radiation light source 1 to 2 propagation of polarization holography graph) is polarized in the Y direction.
Following formulate grating depth d and different refractivity:
(na-nb)＝Nλ1 (12)
(na-nx)＝Nλ1+λ1/2 (13)
In above-mentioned formula, N represents the integer outside 0, and n represents an integer.
In the polarization holography graph of prior art example and embodiment 1, N=0, but present embodiment is characterised in that N ≠ 0
At first, when optical wavelength is λ 1, because output light 12a is polarized in the Y direction, when light is propagated by polarization holography substrate 2, by producing phase differential N λ 1 (just phase differential is 2 π) between the light according to the recess of the grating of formula 12 and protruding place.This phase differential is equal to 0 basically.Therefore pass through the light 12b of medium 2B not by optical grating diffraction.The polarization direction of light 12b remains unchanged in the Y direction.Light 12b passes quarter-wave plate 3, becomes circularly polarized light 12c.When compact disc substrate 6 does not cause birefringence, be the circularly polarized light identical with light 12c from the back light 13a of CD signal face 6a.After passing quarter-wave plate 3, the light 13b that back light 13a becomes at the directions X linear polarization.Therefore, according to formula 13, when light 13b propagates by polarization holography substrate 2, produce phase differential N λ 1+ λ 1/2 (just phase differential is π) between the recess by grating and the light at protruding place.The light 13c a large portion of having passed substrate 2A is by optical grating diffraction (about 0% under 0 grade of light situation, under the positive and negative one-level light situation about 41%).
Then, when light wavelength is λ 2, because output light 12a is polarized in the Y direction, when light is propagated by polarization holography substrate 2, by producing phase differential λ 2-N λ 1 (just phase differential is 2 π (1-N λ 1/ λ 2)) between the light according to the recess of the grating of formula 12 and protruding place.Usually passed the light 12b of medium 2B by optical grating diffraction.Yet 0 independent order diffraction light relates to record and reproducing signal, and other senior diffraction light (one-level or more senior) is the diffused light that will be eliminated.Therefore in introducing hereinafter, ignore the more senior light in the outgoing route.The polarization direction of light 12b remains on the Y direction.Light 12b becomes elliptically polarized light 12c by quarter-wave plate 3 (corresponding to being used for 1/4 * λ, 1/ λ, 2 wave plates that wavelength is the light of λ 2).When compact disc substrate 6 ' causes birefringence, may be circularly polarized light, elliptically polarized light or linear shape polarized light from the back light 13a of CD signal face 6a '.Therefore light 13b be any direction between directions X and the Y direction by the direction of passing quarter-wave plate 3 and being polarized.Thereby according to formula 13, when light by after the holographic substrate 2, between the light at recess by grating and protruding place, exist phase differential λ 2-N λ 1-λ 1/2 and λ 2-N λ 1 (just phase differential be 2 π 1-(n+1/2) λ 1/ λ 2} and 2 π (1-N λ 1/ λ 2)).Usually the light 13c that has passed substrate 2 is by optical grating diffraction, and therefore, under the birefringence condition of any given compact disc substrate 6 ', diffraction efficiency can not be 0.For example, as λ 1=660nm, λ 2=792nm, N=1 is during n=0, positive and negative first-order diffraction diffraction of light efficient approximately is 10% (phase differential is π/3) on outgoing route, and have 7 π/6 and π/3 two kind of phase differential on the return path, in the previous case, positive and negative first-order diffraction diffraction of light efficient approximately is 38%, and under latter event, diffraction efficiency approximately is 10%.That is to say that according to the birefringence condition, diffraction efficiency changes between 10～38%.As λ 1=660nm, λ 2=792nm, N=1, during n=1, positive and negative first-order diffraction diffraction of light efficient approximately is 10% (phase differential is π/3) on outgoing route, and existence-pi/2 and π/3 two kind of phase differential on the return path, in the previous case, positive and negative first-order diffraction diffraction of light efficient approximately is 20%, and under latter event, diffraction efficiency approximately is 10%.That is to say that according to the birefringence condition, diffraction efficiency changes between 10～20%.In both cases, have under any birefringence condition at compact disc substrate 6 ', diffraction efficiency also never is lower than 10%.Therefore even under CD had high birefringence situation such as CD etc., CD signal also can be detected reliably by photodetector.Therefore, be the light of λ 2 with respect to wavelength, although in the light propagation efficiency on the outgoing route and the light detection efficiency on return path variation a little, can guarantee that stable signal detection performance is not subjected to that compact disc substrate is birefringent to be influenced.
In above introducing, medium 2B shown in Figure 6 is made by birefringent material.Yet substrate 2A can be made by birefringent material, or substrate 2A and medium 2B can be made by birefringent material.
Fig. 7 A and 7B are the cut-open views that shows according to the polarization holography substrate 2 of another example.In the polarization holography substrate 2 shown in Fig. 7 A, by forming pattern and carrying out local etching subsequently and at LiNbO
3Crystal medium 200A goes up and forms proton exchange zone 200B.As shown in Figure 6, proton exchange zone 200B is formed on the Y direction, but also can be formed in any direction.
In the polarization holography substrate 2 shown in Fig. 7 B, proton exchange zone 210B is formed on LiNbO by forming pattern
3On the crystal medium 210A, and a Ta
2O
3Film also is formed on the described proton exchange zone 210B by forming pattern.As shown in Figure 6, proton exchange zone 210B is formed on the Y direction, but also can be formed in any direction.
In Fig. 7 A and 7B, dotted line is represented the wave front propagated, and in the case, wavelength is that the light of λ 1 (0.66 μ m) is propagated by polarization holography substrate 2, thereby causes phase differential λ 1, but this is one and is substantially equal to 0 phase differential.With respect to others, the effect that is obtained in the effect of the polarization holography substrate 2 shown in each accompanying drawing and polarization holography substrate shown in Figure 6 is identical.Therefore, be the light of λ 1 and λ 2 with respect to wavelength, can obtain the diffraction efficiency that is fit to reliably.
Fig. 8 A and 8B have shown from CD one side and have seen holographic facet one side and a kind of photodetector pattern and the photodistributed mode according to the embodiment 3 that obtain thereon.Identical in holographic photography pattern and the xsect of doing along optical axis among before the photodetector and focal position afterwards and the embodiment 1, so omission is to their introduction.The light check pattern except its shape is extended along the y direction, other also with embodiment 1 in identical, therefore also omit introduction to it.Fig. 8 A shown by the mode with respect to the hot spot that back light forms of first laser beam of sending from the first luminous point 1a, and Fig. 8 B has shown by the mode with respect to the hot spot that back light forms of second laser beam of sending from the first luminous point 1a ' simultaneously.
In Fig. 8 A, when when the y direction of principal axis is measured, the junction between hot spot 82S ' and the 83S ' was 11 (also there is same case in the junction between hot spot 82S and the 83S) apart from the distance of point 90.When the y direction of principal axis is measured, between hot spot 81FS ' and the 81BS ' between junction and 84FS ' and the 84BS ' junction are l1+l1 ' (between hot spot 81FS and 81BS between junction and 84FS and the 84BS junction also have same case) apart from the distance of point 90.On the other hand, in Fig. 8 B, when when the y direction of principal axis is measured, the junction between hot spot 82S ' and the 83S ' is l2 (also there is same case in the junction between hot spot 82S and the 83S) apart from the distance of point 90 '.When the y direction of principal axis is measured, between hot spot 81FS ' and the 81BS ' between junction and 84FS ' and the 84BS ' junction be l2+l2 ' (between hot spot 81FS and the 81BS between junction and 84FS and the 84BS junction also have same case) apart from the distance of point 90 '.Luminous point 1a and 1a ', promptly putting 90 and 90 ' is ε along Y-axis distance each other.Suppose to exist following relation.
l2＝l1+ε (14)
In the case, if with respect to first laser beam, between hot spot 82S ' and the 83S ' junction almost with photodetector 7T2 and 7T3 between separator bar 7Ta overlap, then have identical situation with respect to second laser beam.
On the other hand, roughly proportional with angle of diffraction apart from the distance of virtual luminous point (just putting 90 or 90 '), angle of diffraction is roughly proportional with wavelength.Therefore, there is following formula
l2/l1＝l2’/l1’＝λ2/λ1 (15)
Because the light check pattern of present embodiment has the shape of extending along the y axle, hot spot 81FS ' and 81BS ' and hot spot 84FS ' and 84BS ' are formed on respectively in photodetector 7T1 and the 7T4, even when they are formed by the light with different wave length.In addition, hot spot 82S and 83S, hot spot 81FS and 81BS, hot spot 84FS and 84BS have narrow width also basically along the setting of y axis on the x direction of principal axis.Even when they are formed by the light with different wave length, they also only move along the y axis, and are very little to the influence of FE signal.
Therefore, when keeping the good signal characteristics, utilize the principle identical,, can obtain the effect identical with embodiment 1 with respect to object lens 5 and polarization holography substrate 2 deviation diametrically with embodiment 1 with respect to two laser beam.
As mentioned above, according to the present invention, even object lens and polarization holography substrate upwards are offset in the footpath of CD, the magnetic track that takes place under tracking Control departs from and can be eliminated.In addition, for the structure with two adjacent radiation light sources, use identical photodetector to detect control signal and reproducing signal, the magnetic track that takes place under tracking Control departs from and can be eliminated.Especially, under the situation with respect to a radiation light source, be used in appointment under any birefringence situation of compact disc substrate, diffraction efficiency can always not be 0, thereby can detect CD signal reliably.
Only otherwise break away from spirit of the present invention and substantive distinguishing features, the present invention can have other any form.The disclosed specific embodiment of present specification is descriptive and nonrestrictive.Protection scope of the present invention determines that by appending claims all modifications based on the spirit of appended claims all belong to protection scope of the present invention.
Claims (9)
1. an optical disc apparatus comprises a radiation light source, object lens, an optical splitter and a photodetector, wherein,
The light that sends from described radiation light source passes described object lens and is focused on the signal face of CD;
The light that is reflected by described signal face passes described object lens and enters described optical splitter;
Described optical splitter is divided into four quadrant Ak (wherein k=1,2,3,4) by two with the straight line of optical axis intersection (y axle and an x axle vertical with disc radial direction) parallel with disc radial direction;
Described photodetector is divided at least 4 area B k;
First-order diffraction light ak is derived from respectively under the effect of described optical splitter by the light that enters described all quadrants Ak, and projects on the Bk zone of described photodetector;
The section that first-order diffraction light a2 and a3 are done along the x axle is roughly on the border between area B 2 and the B3; And
First-order diffraction light a1 and a4 are distributed on the described photodetector with being separated from each other.
2. optical disc apparatus according to claim 1 is characterized in that: according to formula TE=C1-C4-(C2-C3)/m, produce the tracking error signal TE of described CD, wherein Ck representative is in area B k (k=1 wherein, 2,3,4) detected signal in, m represent 1 or bigger value.
3. optical disc apparatus according to claim 1, it is characterized in that: negative first-order diffraction light ak ' (k=1 wherein, 2,3,4) by the light that enters described all quadrants Ak under the effect of described optical splitter and derive from respectively, negative first-order diffraction light a2 ' is focused on the described detection faces and does not reverse with respect to the y direction of principal axis, and negative first-order diffraction light a3 ' reverses with respect to the y direction of principal axis and is focused on the described detection faces.
4. an optical disc apparatus comprises the first radiation light source, the second radiation light source, object lens, an optical splitter and a photodetector, wherein,
The described first radiation light source and the second radiation light source are set on the described photodetector;
Pass described object lens and be focused on the signal face of first CD from described first light that sends of radiation light source;
The light that is reflected by this signal face passes described object lens and enters described optical splitter;
Described optical splitter is divided into four quadrant Ak (wherein k=1,2,3,4) by two with the straight line of optical axis intersection (y axle and an x axle vertical with disc radial direction) parallel with disc radial direction;
Described photodetector is divided at least 4 area B k;
First-order diffraction light ak, and is projected on the Bk zone of described photodetector under the effect of described optical splitter and derive from respectively by the light that enters described all quadrants Ak;
Send and have and pass described object lens from described first light that radiates the light different wave length that light source sends and be focused on the signal face of second CD from the described second radiation light source;
Light by the reflection of the signal face of described second CD passes described object lens and enters described optical splitter, under the effect of described optical splitter and derive from respectively, and described first-order diffraction light bk is projected respectively on the Bk zone of described photodetector first-order diffraction light bk by the light that enters described all quadrants Ak.
5. optical disc apparatus according to claim 4, it is characterized in that: roughly on the border between area B 2 and the B3, first-order diffraction light a1 and a4 or b1 and b4 are distributed on the described photodetector section that first-order diffraction light a2 and a3 or b2 and b3 are done along the x axle with being separated from each other.
6. optical disc apparatus according to claim 4 is characterized in that: according to formula TE=C1-C4-(C2-C3)/m, produce the tracking error signal TE of first or second CD, wherein Ck representative is in described area B k (k=1 wherein, 2,3,4) detected signal in, m represent 1 or bigger value.
7. optical disc apparatus according to claim 4, it is characterized in that: negative first-order diffraction light ak ' or bk ' (k=1 wherein, 2,3,4) by the light that enters described all quadrants Ak under the effect of described optical splitter and derive from respectively, negative first-order diffraction light a2 ' or b2 ' are focused on the detection faces and do not reverse with respect to the y direction of principal axis, and negative first-order diffraction light a3 ' or b3 ' reverse with respect to the y direction of principal axis and be focused on the detection faces.
8. an optical disc apparatus comprises the first radiation light source, the second radiation light source, object lens, an optical splitter and a photodetector, wherein,
The structure of described optical splitter has one and has the periodically birefringent medium of convex-concave xsect;
Send and wavelength is that the light of λ 1 enters described optical splitter from the described first radiation light source, and periodically converted to the light that phase differential approximately is 2n π, wherein n represents the integer outside 0;
Above-mentioned light passes described object lens and is focused on the signal face of described first CD;
The light that is reflected by described signal face passes described object lens, enter described optical splitter then, and periodically converted to the light that phase differential approximately is 2n π+α, and enter described photodetector and detected by the diffraction light that above-mentioned light derives from, wherein α represents the real number outside 0;
Send and wavelength is that the light of λ 2 enters described optical splitter from the described second radiation light source, and periodically converted to the light that phase differential approximately is 2n π λ 1/ λ 2;
Above-mentioned light passes described object lens and is focused on the signal face of one second CD;
Light by the signal face of described second CD reflection passes described object lens, enters described optical splitter then, and periodically to be converted to phase differential approximately be (the light of λ 1/ λ 2 of 2n π+α);
The diffraction light that is derived from by above-mentioned light enters described photodetector and detected.
9. a light-dividing device comprises the first radiation light source, the second radiation light source, object lens, an optical splitter and a photodetector, wherein,
The structure of described optical splitter has one and has the periodically birefringent medium of convex-concave xsect;
Send and wavelength is that the light of λ 1 enters described optical splitter from the described first radiation light source, and periodically converted to the light that phase differential approximately is 2n π, wherein n represents the integer outside 0;
Above-mentioned light passes described object lens and is focused on the signal face of described first CD;
The light that is reflected by described signal face passes described object lens, enter described optical splitter then, and periodically converted to the light that phase differential approximately is 2n π+α, and enter described photodetector and detected by the diffraction light that above-mentioned light derives from, wherein α represents the real number outside 0;
Send and wavelength is that the light of λ 2 enters described optical splitter from the described second radiation light source, and periodically converted to the light that phase differential approximately is 2n π λ 1/ λ 2;
Above-mentioned light passes described object lens and is focused on the signal face of one second CD;
Light by the signal face of described second CD reflection passes described object lens, enters described optical splitter then, and periodically to be converted to phase differential approximately be (the light of λ 1/ λ 2 of 2n π+α);
The diffraction light that is derived from by above-mentioned light enters described photodetector and detected.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2003101014662A CN1497555A (en) | 2002-10-18 | 2003-10-20 | Optical disk device and spectral device |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP304913/2002 | 2002-10-18 | ||
| CNA2003101014662A CN1497555A (en) | 2002-10-18 | 2003-10-20 | Optical disk device and spectral device |
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| Publication Number | Publication Date |
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| CN1497555A true CN1497555A (en) | 2004-05-19 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2003101014662A Pending CN1497555A (en) | 2002-10-18 | 2003-10-20 | Optical disk device and spectral device |
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| CN (1) | CN1497555A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106087674A (en) * | 2016-06-23 | 2016-11-09 | 陆玥 | A kind of square, high ferro station floor tile builds automation integrated machine with building device |
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- 2003-10-20 CN CNA2003101014662A patent/CN1497555A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106087674A (en) * | 2016-06-23 | 2016-11-09 | 陆玥 | A kind of square, high ferro station floor tile builds automation integrated machine with building device |
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