CN101331547A - Objective lens, optical head and optical disc device - Google Patents

Abstract

An objective lens, an optical head, and an optical disc device (drive) capable of attaining good recording or reproduction characteristics by compensating various aberrations including variation in wavelength for various kinds of optical discs such as a high density optical disc, a DVD, a CD, and the like, under good wavelength dispersion compensation performance are provided. The objective lens includes a first lens and a second lens substantially adhered to have the optical axes mutually matched, and functions as a convex lens, as a whole. Each lens has a central portion including the optical axis, and a peripheral portion around the central portion. The central portion of the first lens functions as a convex lens and the central portion of the second lens functions as a concave lens. Assuming the refractive index of the first lens in d line (wavelength 587.56nm) is nd1, an Abbe number represented using the refractive index of the d line, F line (wavelength 486.13nm) and C line (wavelength 656.27nm) is [upsilon]d1, the refractive index of the second lens in d line is nd2, and an Abbe number represented using the refractive index of the d line, F line and C line is [upsilon]d2, following relation is satisfied; nd1>nd2 and [upsilon]d1> [upsilon]d2.

Description

Object lens, optical head and optical disc apparatus

Technical field

The present invention relates to possess wavelength different a plurality of light sources mutually, the optical head that information recording carriers such as multiple CD is carried out recording of information or regeneration with optical mode; Employed object lens and possess the optical disc apparatus of optical head in the optical head.

Background technology

In recent years, be accompanied by the practicability of semiconductor laser of emission bluish violet color laser, disk track is identical with CD (Compact Disc) or DVD (Digital Versatile Disc), conduct more the Blu-ray of high density/jumbo optical information recording medium (the following CD that also is called) (below be called BD) be practical.BD can utilize bluish violet color laser light source about wavelength 400nm and numerical aperture (NumericalAperture, NA) high to 0.85 object lens, carry out recording of information or regeneration, protective substrate thickness is about the CD of 0.1mm." protective substrate thickness " is meant: the surface of CD that is present in the laser light incident side is to thickness between the information recording layer, hyaline layer (protective substrate).

In addition, researching and developing a kind of same about having utilized wavelength for 400nm the bluish violet color laser light source and numerical aperture be 0.65 object lens, protective substrate thickness is about the high density compact disc (utilize the bluish violet color laser light source to write down these or the CD of regenerating is referred to as high density compact disc) of 0.6mm.

Therefore, proposed a kind ofly to utilize object lens to make the respectively different laser of wavelength, the information recording layer of the CD that optically focused has nothing in common with each other to protective substrate thickness carries out optical head recording of information and regeneration, that have interchangeability.

Patent documentation 1 discloses a kind of object lens that are used for as the optical head of record that carries out high density compact disc and DVD or regeneration, for example used reference lens 101a shown in Figure 28, that form by synthetic resin material or glass material and connect airtight in this reference lens 101a connect airtight the compound lens that lens 101b is constituted by what the ultraviolet hardening resin material formed, as the optical head of object lens 101.

In Figure 28, show the face 111 of the light source side of reference lens 101a, as the face of the CD side of reference lens 101a and connecting airtight face 112 and connecting airtight the face 113 of the CD side of lens 101b as the face of the light source side of connecting airtight lens 101b.

According to this conventional example, can be to the laser of red laser and these two kinds of wavelength of bluish violet color laser, the aberration that compensation produces because of the difference of wavelength.

In addition; in patent documentation 2, disclose a kind of laser that has utilized about wavelength 405nm, reached three kinds of wavelength about wavelength 785nm about wavelength 655nm, in the different CD of protective substrate thickness, had optical pickup objective diffraction limit performance, that possess high optical characteristics respectively.

In this conventional example, as shown in figure 29, utilization is by reference lens 201a, with connect airtight or the approximate object lens 201 that connect airtight lens 201b formation face 212, that material is different with reference lens 201a that connect airtight, engage or be adhered to the CD side of reference lens 201a, can carry out: utilize the highdensity CD of bluish violet color laser, record or the regeneration of DVD, CD.

More than, disclosed object lens utilize the poor of reference lens and refractive index of connecting airtight lens and chromatic dispersion in two conventional examples, only the refracting power of scioptics and to 2 different or 3 wavelength mutually, aberration for compensation.Therefore, compare, almost do not have the loss of light quantity, can obtain the high efficient that sees through at all wavelength with the object lens that utilized diffraction.

Patent documentation 1: the spy opens the 2000-90477 communique

Patent documentation 2: the international openly text that discloses No. 2004/053557

In the prior art, do not consider the wavelength dispersion compensation performance, and, be difficult to fully acquisition because of the calibration result of the spherical aberration that difference produced of the protective substrate thickness of CD.

For example, in patent documentation 1, record at the corrugated aberration of bluish violet color laser with at the corrugated aberration of red laser.But, do not mention the moving of best image point position of this corrugated aberration, therefore, not talkatively considered the wavelength dispersion compensation performance.And; do not have narration and the thickness of the protective substrate of the CD that writes down or regenerate, the relevant particular content of numerical aperture of object lens, the calibration result that whether can fully obtain the spherical aberration that the difference because of the protective substrate thickness of CD produces is also clear.These might especially become problem in the recordable type optical head.

In addition, because patent documentation 1 does not mention record or the regeneration of the CD that utilizes the infrared laser about wavelength 785nm, so record or regeneration for high density compact disc, DVD and CD do not have the exchange performance.

On the other hand, the embodiment 1～5 of patent documentation 2 disclosed conventional examples has narrated and has utilized the reference lens that formed by glass material and by resin material connecting airtight of forming recording of information object lens that lens constitute, corresponding with high density compact disc, DVD, CD or the exchange performance of regeneration.

But if according to the embodiment 1 of patent documentation 2, then the centre wavelength with respect to bluish violet color laser is the change of the wavelength ± 1nm under the 405nm, and the change of the best image point position of RMS corrugated aberration is more than the 1 μ m, and is very big.This can't fully realize the wavelength dispersion compensation performance.

In addition, in the embodiment 6 and 7 of patent documentation 2, though disclose the design example of the well behaved object lens of wavelength dispersion compensation, for these object lens, reference lens and to connect airtight lens all be glass material does not mention its concrete method for making.The situation of reality is: on the basis of two glass lenss of high precision shaping, it is difficult making object lens by joint or bonding.

And the embodiment 7 of patent documentation 2 discloses when the record of CD and DVD or regeneration, and laser is incided in the object lens as diverging light.But, very little because the object distance of CD is 19.5mm, so it is very difficult constituting actual optical head.In fact do not mention the concrete formation of optical head.

And for being accompanied by the spherical aberration that high density compact disc produces with the discrete of the centre wavelength of laser, wavelength is discrete ± and the spherical aberration (chromosphere surface aberration) that produced during 5nm surpasses 100m λ.But, in the embodiment 1 of patent documentation 2,, do not relate to the compensation method of chromosphere surface aberration not at the opinion of this major issue.

In addition, because in the optical head put down in writing of patent documentation 2, three-wavelength object distance difference separately, so, the luminous point of each wavelength on the optical head and be subjected to the configuration formation etc. of luminous point to become complicated.But do not mention any content for such problem.For example, according to the embodiment 7 of patent documentation 2, the object distance of CD and DVD is respectively 20nm and 38nm, and is very little.The formation of this optical head is not disclosed as yet, and its realization property is not understood.

In addition, from the viewpoint of the bump of evading object lens and CD, preferred object lens are with respect to operating distance (the Working Distance of CD; WD) be the bigger the better.But according to the embodiment 4 of patent documentation 2, the operating distance maximum of object lens about 0.38mm, is insufficient as the employed object lens of the optical head of recordable type CD only.

Summary of the invention

The objective of the invention is to, a kind of good wavelength dispersion compensation performance that has is provided, and compensation comprises the various aberrations of the change of wavelength to the CD of a plurality of kinds such as high density compact disc, DVD, CD, can obtain object lens, optical head and the optical disc apparatus (driver) of good record or reproducing characteristic.

Object lens of the present invention are assembled in optical head.Described object lens comprise first lens and second lens that connected airtight in fact according to the mode of mutual optical axis unanimity, and it is whole as convex lens performance function, described first lens and described second lens have respectively: the core that comprises optical axis, with the peripheral part on every side that is positioned at described core, the core of described first lens is brought into play function as convex lens, the core of described second lens is brought into play function as concavees lens, be made as nd1 in the refractive index that the d line (wavelength 587.56nm) of described first lens is located, to utilize the d line, the represented Abbe number of refractive index of F line (wavelength 486.13nm) and C line (wavelength 656.56nm) is made as υ d1, the refractive index of the d line of described second lens is made as nd2, to utilize the d line, when the represented Abbe number of the refractive index of F line and C line is made as υ d2, satisfy nd1＞nd2 and υ d1＞υ d2.

Also can be, described refractive index n d1 satisfies 1.60＜nd1＜1.85, and described refractive index n d2 satisfies 1.45＜nd2＜1.60, and described Abbe number υ d1 satisfies 40＜υ d1＜60, and described Abbe number υ d2 satisfies 20＜υ d2＜40.

Also can be that described first lens and described second lens engage or bond together.

Also can possess the anchor clamps that described first lens and described second lens are connected airtight in fact, keep.

Also can be, described first lens be formed by glass material, and described second lens are formed by resin material.

Also can be that the glass transformation temperature of described resin material is below 300 degree.

Also can be that described second lens are formed by ultraviolet hardening resin.

Also can be that described resin material is a polycarbonate.

Also can be that described first lens and described second lens are formed by glass material.

Also can be that described first lens are formed by the mutual different glass material of glass transformation temperature with described second lens.

Also can be that the difference of the glass transformation temperature of the glass material of the glass transformation temperature of the glass material of described first lens and described second lens is more than 200 degree.

Also can be, described object lens have three lens faces with described optical axis intersection, do not face first lens face of a lens face side, that be described first lens mutually with described second lens that is:; Second lens face of described first lens that formation is connected airtight in fact and the boundary of described second lens; And the 3rd lens face of not facing a lens face side, that be described second lens mutually with described first lens, in the effective coverage of at least one lens face of described first lens face, described second lens face and described the 3rd lens face, comprise the central effective coverage and the peripheral effective coverage on every side that is positioned at described middle section of optical axis, form by different aspherical shape.

Also can be that for described first lens face, described second lens face and described the 3rd lens face, described middle section is separately formed by different aspherical shape with described neighboring area.

Also can be, in the section that will join with the arbitrfary point on the face in effective diameter of described second lens face, with the plane vertical with optical axis is that the reference plane angulation is when being made as θ, at the central effective coverage of described second lens face and the intersection of peripheral effective coverage, the value of described θ changes.

Also can be that at the central effective coverage of described second lens face and the intersection of peripheral effective coverage, at least one side of the absolute value of described θ and symbol changes.

Also can be, to be provided with optical jump at described first lens face, described second lens face and the described middle section that at least one lens face had of described the 3rd lens face and the intersection of described neighboring area.

Also can be that the peripheral effective coverage of described first lens face possesses the diffraction structure of the light of the provision wavelengths made from the diffraction efficiency diffraction more than 80%.

Optical head of the present invention possesses: a plurality of light sources of the light of emission different wave length; And the described object lens of light convergent that make an emission from described a plurality of light sources.

Also can be, the object lens that possess in the described optical head utilize described core and described peripheral part, make the light convergence from first light source in described a plurality of light sources, in fact only utilize described core, make light convergence from the secondary light source in described a plurality of light sources.

Also can be, described first light source be compared with described secondary light source, the light of emission shorter wavelength.

Also can be, described optical head also possesses transformation component, and described transformation component is transformed to approximate directional light, diverging light or convergence light according to light wavelength with described light, and it is incided in the described object lens.

Also can be that described transformation component will be transformed to approximate directional light from the light that described first light emitted goes out.

Also can be that described transformation component will be transformed to convergence light, diverging light or approximate directional light from the light that described secondary light source is launched.

Also can be, described optical head also possesses the 3rd light source, and described the 3rd light source is compared with described secondary light source with described first light source, launches more long wavelength's light, and described transformation component will be transformed to diverging light from the light that described the 3rd light emitted goes out.

Also can be that described optical head also possesses basis from the light wavelength that light emitted goes out, and limits the limited aperture portion of the beam diameter of described light.

Also can be, described optical head also possesses the 3rd light source, described the 3rd light source is compared with described secondary light source with described first light source, launches more long wavelength's light, the light of the described first light emitted wavelength X 1, the light of described secondary light source emission wavelength lambda 2, the light of described the 3rd light emitted wavelength X 3, described wavelength X 1, described wavelength X 2 and described wavelength X 3 satisfy 350nm＜λ 1＜450nm, 600nm＜λ 2＜700nm, 700nm＜λ 3＜850nm.

Also can be, described optical head also possesses transformation component, is used for the light of described wavelength X 1 is transformed to approximate directional light, and the light of described wavelength X 2 is transformed to convergence light, and the light of described wavelength X 3 is transformed to diverging light and it is incided in the described object lens.

Also can be, described optical head also possesses the chromatic aberation correcting element that is used for the correcting colour aberration, and the chromatic aberation of the described object lens that described chromatic aberation correcting element produces the light wavelength change that is accompanied by described wavelength X 1 is proofreaied and correct.

Also can be, in light time by described object lens optically focused wavelength X 3, the arbitrfary point in the effective coverage of described object lens with by optically focused the interval W of optical recording media of light, more than 0.30mm.

Also can be, when the light that makes described wavelength X 1 is concentrated on optical recording media, thickness at the focus place of described light because of the light transmission layer of optical recording media produces spherical aberration, and the spherical aberration that described transformation component produces the focus place of the light of described wavelength X 1 changes.

Also can be that described transformation component possesses: collimation lens, it makes the light of described wavelength X 1 incide described object lens as approximate directional light at least; And drive division, its based on the corresponding drive signal of institute's wavelength of light emitted, described collimation lens is moved along optical axis direction.

Also can be, when the position that the light that can make described wavelength X 1 is incided the described collimation lens in the described object lens as approximate directional light is made as the reference position, described drive division, according to the drive signal corresponding with the light of described wavelength X 2, described collimation lens is moved from the direction of described reference position to described object lens, thereby the light of described wavelength X 2 is incided in the described object lens, according to the drive signal corresponding with the light of described wavelength X 3, described collimation lens is moved from described reference position to the direction opposite with described object lens, thereby the light of described wavelength X 3 is incided in the described object lens.

Also can be, described transformation component utilizes the index distribution changeable material to constitute at least, and the index distribution of described index distribution changeable material because of electric field, magnetic field or the heat that applies from the outside accordingly with the institute wavelength of light emitted, and changes.

Also can be, described transformation component be the lens that utilize the different multiple non-Combination liquid of refractive index to constitute, the interface of described multiple non-Combination liquid, and corresponding to institute's wavelength of light emitted, its curvature changes.

Also can be that described secondary light source and described the 3rd light source are configured in roughly the same position

Also can be that described secondary light source and described the 3rd light source are by integrated.

Also can be, also to possess relay lens with negative focal length between described first light path and the described transformation component and have only on the light path that the light of described wavelength X 1 passes through.

Also can be, in described chromatic aberation correcting element, be provided with the phase place jump, described phase place jump constitutes, the difference of the optical path length that is produced during the described phase place jump of the light transmission of described wavelength X 1 is about 10 times of described wavelength X 1, thus, the light wavelength that can proofread and correct because of described wavelength X 1 changes the spherical aberration that produces in the focal position of described light.

Also can be, also possesses for the part of the light of described wavelength X 1 optical element as phase place jump performance function, the difference of the optical path length that is produced during the described phase place jump of the light transmission that described phase place jump constitutes described wavelength X 1 is about 10 times of described wavelength X 1, thus, the light wavelength that can proofread and correct because of described wavelength X 1 changes the spherical aberration that produces in the focal position of described light.

Also can be, be accompanied by the light wavelength change of described wavelength X 1 and in the spherical aberration that produces, described transformation component is mainly proofreaied and correct spherical aberration three times, the main number of corrections of described phase place jump be the spherical aberration more than five times.

Also can be that optical drive of the present invention possesses: described optical head, be used to rotate motor that drives optical recording media and the control part of controlling described optical head and described motor.

Also can be that object lens of the present invention are assembled in optical head.Described object lens comprise first lens and second lens that connected airtight in fact according to the mode of mutual optical axis unanimity, and whole as convex lens performance function.Described first lens and described second lens have respectively: the core that comprises optical axis; And the peripheral part on every side that is positioned at described core.The core of described first lens is brought into play function as convex lens, the core of described second lens is brought into play function as concavees lens, with at least one lens face described optical axis intersection, described object lens, have: the peripheral effective coverage that comprises the central effective coverage of described optical axis and do not comprise described optical axis, described central effective coverage forms the aspherical shape of being shown by different aspheric surface institute coefficient tables respectively with described peripheral effective coverage.

Also can be, by described first lens and described second lens regulation: not a side of facing mutually with described second lens, be first lens face of the lens face of described first lens; Second lens face of described first lens that formation is connected airtight in fact and the boundary of described second lens; And a side of not facing mutually with described first lens, be the 3rd lens face of the lens face of described second lens, in the effective coverage of at least one lens face of described first lens face, described second lens face and described the 3rd lens face, the middle section that comprises optical axis is formed by different aspherical shape with the neighboring area on every side that is positioned at described middle section.

Also can be that for described first lens face, described second lens face and described the 3rd lens face, described middle section separately and described neighboring area are formed by different aspherical shape.

Also can be, in the section that will join with the arbitrfary point on the face in the effective diameter of described second lens face, with the plane perpendicular to optical axis be the reference plane angulation, when being made as θ, at the central effective coverage of described second lens face and the intersection of peripheral effective coverage, the value of described θ changes.

Also can be that at the central effective coverage of described second lens face and the intersection of peripheral effective coverage, at least one side of the absolute value of described θ and symbol changes.

Also can be, to be provided with optical jump at described first lens face, described second lens face and the described middle section that at least one lens face had of described the 3rd lens face and the intersection of described neighboring area.

Also can be that the peripheral effective coverage of described first lens face possesses the diffraction structure of the light of the provision wavelengths made from the diffraction efficiency diffraction more than 80%.

According to the present invention, can obtain to have diffraction-limited performance and the outstanding object lens of wavelength dispersion compensation performance with respect to high density compact discs such as BD, DVD, CD.If, then can simplify the formation of optical head owing to adopt this object lens, so, can make the optical head miniaturization.As a result, the optical disc apparatus that has carried this optical head also is miniaturized or slimming, can be with the low cost manufacturing.And such optical disc apparatus has outstanding record regenerating performance because of the above-mentioned performance of object lens.

Description of drawings

Fig. 1 is the figure of expression based on the formation of the object lens 1 of embodiment 1.

Fig. 2 (a)～(c) is respectively that expression utilizes the object lens 1 of embodiment 1, the constitutional diagram of the light when making laser focusing to separately information recording layer of BD60, DVD70, CD80.

Fig. 3 is the corrugated aberration diagram of laser focusing when BD60 that makes wavelength 405nm.

Fig. 4 is the corrugated aberration diagram of laser focusing when DVD70 that makes wavelength 655nm.

Fig. 5 is the corrugated aberration diagram of laser focusing when CD80 that makes wavelength 785nm.

Fig. 6 is RMS (Root Mean Square) corrugated aberration diagram of representing incident angle of light at transverse axis.

Fig. 7 is the pie graph of expression based on the object lens 21 of embodiment 2.

Fig. 8 (a)～(c) is respectively that expression utilizes the object lens 21 of embodiment 2, the constitutional diagram of the light when making laser focusing to separately the information recording layer of BD60, DVD70, CD80.

Fig. 9 is the corrugated aberration diagram of laser focusing when BD60 that makes wavelength 405nm.

Figure 10 is the corrugated aberration diagram of laser focusing when DVD70 that makes wavelength 655nm.

Figure 11 is the corrugated aberration diagram of laser focusing when CD80 that makes wavelength 785nm.

Figure 12 is a RMS corrugated aberration diagram of representing incident angle of light at transverse axis.

Figure 13 is the figure of the state of expression CD light path when being BD60, in the optical head 7.

Figure 14 is the figure of the state of expression CD light path when being DVD70, in the optical head 7.

Figure 15 is the figure of the state of expression CD light path when being CD80, in the optical head 7.

Figure 16 is the figure of the state of expression CD light path when being BD60, in the optical head 100.

Figure 17 is the figure of the state of expression CD light path when being DVD70, in the optical head 100.

Figure 18 is the figure of the state of expression CD light path when being CD80, in the optical head 100.

Figure 19 (a) reaches the figure of the summary formation that (b) is expression collimation lens 46 and the driving mechanism that drives collimation lens 46 along optical axis direction.

Figure 20 is the figure of the state of the light when representing along optical axis direction driving collimation lens 46.

Figure 21 is the focal length of the collimation lens 46 of expression when receiving bluish violet color laser from BD60, the graph of a relation of the focal length of the collimation lens 46 when receiving red laser from DVD70/CD80/infrared laser.

Figure 22 (a) and (b) be the figure of position that expression is subjected to the luminous point of the luminous body member 50 of light.

Figure 23 (a)～(c) is the figure that the object lens side that is illustrated in collimation lens 46 is provided with the example of index distribution changeable material 54.

Figure 24 is the figure of the example of expression diffraction type chromatic aberation correcting element 47.

Figure 25 (a)～(d) is that expression is write down BD60 or the corrugated aberration diagram when regenerating.

Figure 26 is the figure of example of the shape of expression phase place jump.

Figure 27 is the figure of expression based on the summary formation of the optical disc apparatus 30 of embodiment 5.

Figure 28 is the pie graph of expression based on the object lens 101 of first conventional example.

Figure 29 is the pie graph of expression based on the object lens 201 of second conventional example.

Among the figure: the 1-object lens, the 1a-reference lens, 1b-connects airtight lens, the 2-light source, the 3-beam splitter, 4-collimation lens, 5-aperture control element, 6-photo detector, the 7-optical head, first public domain of 11i-, first reserved area of 11o-, second public domain of 12i-, second reserved area of 12o-, the 3rd public domain of 13i-, the 3rd reserved area of 13o-, 20-optical head, the 30-optical disc apparatus, 35-disc drives portion, 36-control part, 60-BD, 70-DVD, 80-CD.

Embodiment

With reference to the accompanying drawings, to based on object lens of the present invention, be assembled with the optical head of these object lens and utilized each embodiment of the optical disc apparatus of this optical head to describe.

In the following embodiment that will illustrate, the so-called optical head corresponding with three-wavelength described.Optical head is equipped on optical disc apparatus (CD drive), according to CD irradiation three-wavelength laser one of the kind of CD, records information on the CD or from the CD sense information.

The kind of CD is made as BD, DVD and CD.For the purpose of simplifying the description, information recording layer all is one below.

The protective substrate thickness of BD is about 0.1mm.To BD recorded information and/or the Wavelength of Laser utilized from the BD regenerating information, for example as long as be the scope that benchmark is included in 350nm～450nm with 405nm.The numerical aperture NA of the object lens 1 corresponding with BD is 0.85.

In addition, the protective substrate thickness of DVD is about 0.6mm.The Wavelength of Laser corresponding with DVD, for example needing only with 655nm is benchmark, is included in from the scope of 600nm～700nm to get final product.The numerical aperture NA of the object lens 1 corresponding with DVD is 0.60.

On the other hand, the protective substrate thickness of CD is about 1.2mm.The Wavelength of Laser corresponding with CD, for example needing only with 785nm is benchmark, is included in from the scope of 700nm～850nm to get final product.The numerical aperture NA of the object lens 1 corresponding with CD is 0.47.

Below, determine BD, DVD and the pairing Wavelength of Laser of CD based on reference wavelength (405nm, 655nm and 785nm) separately.

In optical head of the present invention, any one of the laser of three-wavelength shone to CD from public object lens.Therefore, the laser focusing that can make each wavelength object lens have been adopted in this optical head to each information recording layer of CD, DVD and BD.

In based on object lens of the present invention, be not provided for making the diffraction grating that shines in the bluish violet color laser diffraction of BD.Bluish violet color laser is only arrived the information recording layer of BD by optically focused by the refraction effect of object lens.Because diffraction grating not being set, so, the efficient that sees through of laser can be kept near 100%.As a result, can suppress the recording of information or the needed laser power of regenerating.Especially because power that need be higher when recording of information than when regeneration, so, power consumption can more effectively be suppressed.

In addition, in being provided with the object lens of diffraction grating, can't all wavelength be improved evenly through efficient.Its reason is, during to each information recording layer of CD, DVD and BD, can't obtain the diffraction efficiency near 100% at the laser focusing that makes each wavelength at all wavelength.Though the diffraction efficiency of BD can be set near 100%, the result is that the diffraction efficiency of for example DVD becomes below 50%.And, because for the low wavelength of diffraction efficiency, light quantity can reduce during laser radiation, and, be subjected to the light time also can further reduce light quantity by the laser of CD reflection, so, in order to ensure the reflection light quantity of necessity, the power setting of laser must be got high.Therefore preferred employing does not utilize the object lens of diffraction grating.

And object lens of the present invention can reduce the change of optical maser wavelength and the change of the chromatic aberation that causes especially can be brought into play high effect to bluish violet color laser.Therefore, though for example will regenerate action when switching to operation of recording the wavelength of bluish violet color laser change has taken place, be not vulnerable to its influence according to object lens of the present invention yet.Thus, can always realize correct recording/reproducing action.Especially Ji Lu failure causes fatefulue data degradation probably, therefore, can realize that correct operation of recording is extremely important.Given this, preferably adopt object lens of the present invention.

(embodiment 1)

With reference to Fig. 1～Fig. 6, the object lens of present embodiment are elaborated.

Fig. 1 represents the formation of the object lens 1 of present embodiment.Object lens 1 are used in to the information recording layer light-concentrating laser of CD and carry out in the optical head of recording of information or regeneration.Object lens 1 are at the information recording layer optically focused of each CD and the laser of this CD corresponding wavelength.

Object lens 1 have: as the reference lens 1a of first lens with connect airtight lens 1b as second lens.

As shown in Figure 1, reference lens 1a and connect airtight the reserved area that lens 1b is divided into the public domain that comprises optical axis and the outside, public domain respectively." public domain " is any public zone of passing through that is designed to the laser of above-mentioned three-wavelength.On the other hand, " reserved area " is only to be designed to the zone that the laser of the wavelength 405nm corresponding with BD passes through.The laser of the wavelength 655nm corresponding, and only pass through the public domain with the laser of the corresponding wavelength 785nm of CD with DVD.

In addition, in view of comprising optical axis, also the public domain is called " middle section ", the reserved area that will be positioned at its central area is called " neighboring area ".

Then, respectively to reference lens 1a and connect airtight lens 1b and describe.

Among the reference lens 1a there be as first of the face of light source side with as second of the face of CD side regulation.

First face of reference lens 1a is divided into public domain 11i and reserved area 11o.Public domain 11i and reserved area 11o form with different aspherical shape as described later.Second face of reference lens 1a is divided into public domain 12i and reserved area 12o.This public domain 12i also forms with different aspherical shape with reserved area 12o.

1a is same with reference lens, connects airtight lens 1b and also stipulates the face of light source side and the face of CD side.

Connect airtight the face of light source side of lens 1b and second of reference lens 1a, in fact by engaging or bonding connecting airtight together.Therefore, they can be regarded as a face.Also this face is called below and connects airtight face.In connecting airtight face, the shape of connecting airtight lens 1b is roughly consistent with the shape of reference lens 1a.Therefore, the public domain of face and the reserved area that connects airtight the light source side of lens 1b also forms with different aspherical shape.

The face that connects airtight the CD side of lens 1b is divided into public domain 13i and reserved area 13o.

Below, with the face 11i of the light source side of reference lens 1a and " first face " that 11o is called object lens 1, will connect airtight " second face " that face is called object lens 1, the face that will connect airtight the CD side of lens 1b is called " the 3rd face ".

Then, the concrete formation to the object lens 1 of present embodiment describes.

Same with the object lens of general optical head, object lens 1 integral body is brought into play function as convex lens.Wherein, reference lens 1a brings into play function as convex lens, and connects airtight the effect that lens 1b has concavees lens.

In the present embodiment, the material of reference lens 1a is K-VC79 (refractive index n d=1.610, Abbe number υ d=57.8).And the material of connecting airtight lens 1b is polycarbonate (refractive index n d=1.584, Abbe number υ d=30.1).Wherein, refractive index n d represents the refractive index in the d line (wavelength 587.56nm).And Abbe number υ d is the value of each refractive index of utilizing d line, F line (wavelength 486.13nm) and C line (wavelength 656.27nm) (being nd, nf, nc in order) expression, particularly, and υ d=(nd-1)/(nf-nc).

The such smaller material of Abbe number υ d of polycarbonate usually can not be as the material of object lens 1.Its reason is, if Abbe number υ d is little, then chromatic dispersion increases, refractive index wavelength and significantly changing.

This change of refractive can be given king-sized influence to the focal position (best image point position) of laser when short wavelengths' such as bluish violet color laser Wavelength of Laser change.The change of the wavelength of LASER Light Source produces because of a variety of causes such as the switching (that is the change of luminous power), temperature change of record and regeneration.

Connect airtight lens 1b as concavees lens by utilizing the little polycarbonate of Abbe number to form, can offset the influence of the change that is accompanied by the best image point position that wavelength variation produces in the reference lens 1a as convex lens by connecting airtight lens 1b.And, shape easily to what connect airtight as the polycarbonate of resin material and to connect airtight lens 1b with reference lens 1a.The application's inventors think, as present embodiment connect airtight one of material of lens, the preferred use is shaped and the minimum polycarbonate of Abbe number among resin material easily.

Here, the aspherical shape of the aspherical shape of first 11i, 11o of object lens 1, the aspherical shape of second 12i, 12o and the 3rd 13i, 13o is by the aspherical shape decision with following (formula 1) expression.

$Z=(1/R){\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="A20068004503600471.png,A20068004503600532.png"\; state="\{\{state\}\}">h</figure-callout>}}^2/[1+[1-(1+k)\&CenterDot;{(1/R)}^2{h}^2{]}^{1/2}]+\mathrm{\&Sigma;}{A}_i{h}^{2i}$ (formula 1)

Wherein, h is the distance of leaving on the optical axis summit, the optical axis vertical direction, and R is a radius-of-curvature, and k is the constant of the cone, and Ai is the asphericity coefficient of i=0～10.Z is optical axis direction, leave the distance (span of hanging down) by the section on the summit of R, k, Ai decision, the aspheric surface interface shape that the curve that is determined by this Z value is given each face.

In addition, in (formula 1) as the A of 0 item ₀h ⁰, be A ₀The amount of movement of having represented the optical axis direction of vertical span.In giving (formula 1) of aspherical shape, generally do not utilize item 0 time, but same with other asphericity coefficient, it is handled as one of asphericity coefficient.

As shown in Figure 1, form each face of object lens 1, in the reserved area that does not comprise optical axis around public domain that comprises optical axis and the public domain, differ widely.

Form first 11i of public domain, each aspherical shape of second (connecting airtight face) 12i, the 3rd 13i, the laser of three-wavelength is by whole optimizations relatively.Promptly, in the scope in the aperture of stipulating by the public domain, according to the laser focusing of each wavelength mode in the position of the information recording layer of the CD of correspondence, decision radius of curvature R, constant of the cone k and asphericity coefficient A, thus decision is based on each aspherical shape of above-mentioned formula 1.

On the other hand, each aspherical shape the shortest only relative bluish violet color laser that forms first 11o of reserved area, second (connecting airtight face) 12o, the 3rd 13o is optimized, by radius of curvature R, circular cone coefficient k and asphericity coefficient Ai decision each aspherical shape based on above-mentioned formula 1.

Object lens 1 mainly are that reference lens 1a plays a role as convex lens as the function of convex lens.Change big (promptly, Abbe number is little) by combination reference lens 1a and refractive index relative wavelength connect airtight lens 1b, can utilize reference lens 1a and refractive index poor of connecting airtight lens 1b under each wavelength, make laser focusing arrive the position of the information recording layer of the CD corresponding with each wavelength.

The specification of following (table 1)～(table 3) expression object lens 1.

Table 1

The face numbering	Radius-of-curvature	Face at interval	Title material
					0	∞		Air
1	(R)	2	VC79
				2	(R)	0.150	Polycarbonate
3	(R)	0.01	Air
				4	∞	Operating distance	Air
5	∞	Protective substrate thickness	Polycarbonate
				6	∞	(information recording surface)	-

Table 2

Table 3

Face code in (table 1) is assigned with according to the following meaning.Face code 0 expression light source; face code first 11i of 1 expression and 11o; face code second 12i of 2 expressions and 12o (connecting airtight face); face code 3 expressions the 3rd 13i and 13o; the reference field of face code 4 expression operating distances; the protective substrate surface of face code 5 expression CDs, the information recording layer of face code 6 expression CDs.And, at face interval and material name, represented face interval and material name between corresponding face code and the next face code.For operating distance, represented lens face near the part of CD and with the distance of CD.In addition, in (table 2), " E+02 "～" E-07 " represents-7 powers of 10 2 powers～10 respectively.

Then, Fig. 2 (a)～(c) represents to utilize the object lens 1 of present embodiment respectively, the state of the light when making laser focusing to separately information recording layer of BD60, DVD70, CD80.

Fig. 2 (a) expression is 0.85 to make the laser focusing of wavelength 405nm with NA, the state of the light of optically focused during to BD60.Equally, Fig. 2 (b) expression is 0.60 to make the laser focusing of wavelength 655nm with NA, the state of the light of optically focused during to DVD70.Fig. 2 (c) expression is 0.47 to make the laser focusing of wavelength 785nm with NA, the state of the light of optically focused during to CD80.State when each has all represented to carry out recording of information or regeneration.

Make laser focusing when BD60, laser has seen through the reserved area and the public domain both sides of object lens 1, and when being concentrated on DVD70 or CD80, laser has only seen through the public domain.

Fig. 3 is the corrugated aberration diagram of laser focusing when BD60 that makes wavelength 405nm, has represented that incident angle of light is 0.0deg (a) and 0.5deg (b).Equally, Fig. 4 is the corrugated aberration diagram of laser focusing when DVD70 that makes wavelength 655nm, and Fig. 5 is the corrugated aberration diagram of laser focusing when CD80 that makes wavelength 785nm.

PX axle shown in Fig. 3～5, PY axle are perpendicular to the axle of optical axis, and the PX axle is perpendicular to the PY axle.The longitudinal axis is represented the corrugated aberration, and smallest dimension is-1 λ, maximum expression+λ (λ: wavelength).

Shown in Fig. 3～5, even if make the incident angle of light of laser be changed to 0.5deg, can confirm also that the corrugated aberration is taked respectively from 0.0deg ± 1 λ is with interior value.

Fig. 6 is RMS (Root Mean Square) corrugated aberration diagram of representing incident angle of light at transverse axis.RMS corrugated aberration has been represented the normal scatter (scattered error) on desirable corrugated and actual corrugated.Among Fig. 6, represented to make the light of wavelength 405nm be concentrated on BD60 situation, make the light of wavelength 655nm be concentrated on the situation of DVD70 and make the light of wavelength 785nm be concentrated on the RMS corrugated aberration of the situation of CD80.

According to Fig. 6, the value of RMS corrugated aberration all is the incident angle of light of 0.0deg～0.5deg under the situation relatively arbitrarily, can confirm that all have all adopted the following following value of diffraction limit of 0.07 λ (λ/14).This has represented the superperformance of object lens 1.

In the present embodiment, when CD80, laser is incided in the object lens 1 as diverging light, make optical system bring into play function as limited system at the laser focusing that makes wavelength 785nm.By laser is incided in the object lens 1 as diverging light, the emergent light convergent position of object lens 1 will be away from object lens 1.As a result, can increase the operating distance that makes laser focusing object lens 1 relative CD80 when CD80.This operating distance generally is preferably more than the 0.30mm, but is preferably more than the 0.40mm especially for the CD of recordable type.The operating distance of the object lens of present embodiment is more than the 0.44mm, and is enough big.

On the other hand, when DVD70, laser is incided in the object lens 1 as convergence light, optical system is brought into play function as limited system at the laser focusing that makes wavelength 655nm.Like this, incide in the object lens 1, can reduce at corrugated aberration BD60, DVD70, CD80, in the public domain by making convergence light.In addition, when making laser focusing, convergence light is incided in the object lens 1, also can guarantee enough big operating distance in DVD70.

Owing to the wavelength of LASER Light Source can be because the switching of record and regeneration, temperature change etc. change, so, short wavelength's Wavelength of Laser change, the refractive index change of the material of object lens is big more, and the result has the tendency of best image point position change.

Object lens 1 according to present embodiment, even taken place ± wavelength variation of 1nm, also only be about ± 0.5 μ m with respect to the change of the best (minimum) corrugated aberration of the RMS corrugated aberration of wavelength 406nm, 404nm with respect to the position of the best (minimum) corrugated aberration of 405nm.Therefore, we can say that object lens 1 have good wavelength dispersion compensation performance.

Reason with good like this wavelength dispersion compensation performance was as before illustrated, its reason is, object lens 1 integral body is brought into play function as convex lens, make chromatic dispersion than reference lens 1a big, be Abbe number little connect airtight the effect that lens 1b has concavees lens, and it is engaged with reference lens 1a as convex lens or bonding.Be accompanied by wavelength variation, the change of the best image point position that produces among the reference lens 1a as convex lens, the lens 1b that connects airtight with concavees lens effect offsets a part.

Wherein, because the object lens 1 of the record of BD or regeneration usefulness are the object lens of the high-NA of NA=0.85, so it is big that the curvature of the face of general light source side becomes, and has the tendency that becomes unmanageable shape.But in the object lens 1 of present embodiment, the maximal value at the angle that is become with reference plane with section that arbitrfary point on first 11i, the 11o face joins is 66.4deg, can easily make the aspheric mould that is used to form object lens.

And in the object lens 1 of present embodiment, reference lens 1a is the outstanding glass material K-VC79 of optical property, can utilize mould to be shaped at an easy rate.On the other hand, connecting airtight lens 1b is polycarbonate as resin material.

Here, the glass transformation temperature of relative datum lens 1a (K-VC79) is 507 degree, and the glass transformation temperature that connects airtight lens 1b (polycarbonate) is 138 degree, therefore, can connect airtight on the reference lens 1a that is formed into formed thereby connecting airtight lens 1b.

In sum, the object lens 1 of present embodiment when carrying out the record regenerating of each CD corresponding with these wavelength, have showed the good optical performance utilizing wavelength 405nm, 660nm, these 3 kinds of light sources of 785nm respectively.Utilized the above-mentioned optical head or the optical disc apparatus of these object lens, can carry out good record or regeneration BD, DVD, these three kinds of CDs of CD.

(embodiment 2)

Then, with reference to Fig. 7～Figure 12, the object lens of present embodiment are described.The object lens of present embodiment also are used to make the information recording layer of laser focusing to BD, DVD and these three kinds of CDs of CD, carry out in the optical head of recording of information or regeneration.

Fig. 7 represents the formation of the object lens 21 of present embodiment.Object lens 21 have reference lens 21a and connect airtight lens 21b.The difference of the object lens of the object lens of present embodiment and embodiment 1 is the shape of reserved area.Be specifically described below.

Reference lens 21a and connect airtight lens 21b is divided into respectively: comprise the public domain that optical axis, three-wavelength laser see through and the reserved area in the outside, public domain.Promptly first in the face of the light source side of reference lens 21a is divided into public domain 31i and reserved area 31o.As the face of the CD side of reference lens 21a and as second (also claiming to connect airtight face) of the face of the light source side of connecting airtight lens 21b, be divided into public domain 32i and reserved area 32o.The face that connects airtight the CD side of lens 21b is the 3rd, is divided into public domain 33i and reserved area 33o.

Because reference lens 21a and connect airtight lens 21b with second 32i and 32o connects airtight or approximate connect airtight, joint or bonding, so, reference lens 21a with connect airtight that lens 21b engages or bonding face, with connect airtight lens 21b and engage or bonding face with reference lens 21a, have identical or roughly the same aspherical shape.

Then, the concrete structure to object lens 21 describes.

The reference lens 21a and the material of connecting airtight lens 21b are respectively with the reference lens 1a of embodiment 1 and to connect airtight lens 1b identical.

The aspherical shape of the aspherical shape of the aspherical shape of first 31i, 31o, second 32i, 32o and the 3rd 33i, 33o is by the aspherical shape decision of above-mentioned (formula 1) expression.

The specification of following (table 4)～(table 6) expression object lens 21.

Table 4

The face numbering	Radius-of-curvature	Face at interval	Title material
					0	∞		Air
1	(R)	2	VC79
				2	(R)	0.150	Polycarbonate
3	(R)	0.017	Air
				4	∞	Operating distance	Air
5	∞	Protective substrate thickness	Polycarbonate
				6	∞	(information recording surface)	-

Table 5

Table 6

Face code in (table 4) is assigned with according to the following meaning.Face code 0 expression light source; face code first 31i of 1 expression and 31o; face code second 32i of 2 expressions and 32o (connecting airtight face); face code 3 expressions the 3rd 33i and 33o; the reference field of face code 4 expression operating distances; the protective substrate surface of face code 5 expression CDs, the information recording layer of face code 6 expression CDs.And, at face interval and material name, represented face interval and material name between this face code and the next face code.In addition, in (table 5), " E+02 "～" E-07 " represents-7 powers of 10 2 powers～10 respectively.And 0 item A0 and embodiment 1 are handled equally.

The difference of table 4 and table 1 is, face is numbered the face numerical value at interval of 3 represented the 3rd 33i and 33o.Face based on the object lens of embodiment 2 is spaced apart 0.017mm, than the face of the object lens of embodiment 1 long 7 μ m of 0.01mm at interval.

On the other hand, the difference of table 6 and table 3 is the numerical value of operating distance.Operating distance based on the object lens of embodiment 2 is 0.662mm, than the short 7 μ m of operating distance 0.669mm of the object lens of embodiment 1.

These are that what to be produced by the shape difference of reserved area is poor.If his-and-hers watches 2 and table 5 compare, then can be understood as the numerical value difference of the asphericity coefficient that reserved area is given.Based on the difference of the numerical value of this asphericity coefficient, the difference as a result of (formula 1) causes the shape difference of reserved area.Because the object lens of embodiment 2 are compared with the object lens of embodiment 1, face has been grown 7 μ m at interval, so, show the situation that the operating distance of having located object lens shortens.

Fig. 8 (a)～(c) represents to utilize the object lens 21 of present embodiment respectively, the state of the light when making laser focusing to separately the information recording layer of BD60, DVD70, CD80.

Fig. 8 (a) expression is 0.85 to make the laser focusing of wavelength 405nm with NA, the state of the light of optically focused during to BD60.Equally, Fig. 8 (b) expression is 0.60 to make the laser focusing of wavelength 655nm with NA, the state of the light of optically focused during to DVD70.Fig. 8 (c) expression is 0.47 to make the laser focusing of wavelength 785nm with NA, the state of the light of optically focused during to CD80.State when each has all represented to carry out recording of information or regeneration.

Make laser focusing when BD60, laser has seen through the reserved area and the public domain both sides of object lens 1, and when being concentrated on DVD70 or CD80, laser has only seen through the public domain.

Fig. 9 is the corrugated aberration diagram of laser focusing when BD60 that makes wavelength 405nm, has represented that incident angle of light is 0.0deg (a) and 0.5deg (b).Equally, Figure 10 is the corrugated aberration diagram of laser focusing when DVD70 that makes wavelength 655nm, and Figure 11 is the corrugated aberration diagram of laser focusing when CD80 that makes wavelength 785nm.Wherein, the mark of Fig. 9～Figure 11 is identical with Fig. 3～5.

Shown in Fig. 9～11, even if make the incident angle of light of laser be changed to 0.5deg, can confirm also that the corrugated aberration is obtained respectively from 0.0deg ± 1 λ is with interior value.

Figure 12 is a RMS corrugated aberration diagram of representing incident angle of light at transverse axis.Represented among Figure 12 to make the light of wavelength 405nm be concentrated on BD60 situation, make the light of wavelength 655nm be concentrated on the situation of DVD70 and make the light of wavelength 785nm be concentrated on the situation of CD80.

According to Figure 12, all be the incident angle of light of 0.0deg～0.5deg with respect to the value of RMS corrugated aberration under any situation, can confirm that all have all adopted the following following value of diffraction limit of 0.07 λ (λ/14).This has represented the superperformance of object lens 21.

In addition, present embodiment also at the laser focusing that makes wavelength 785nm when CD80, laser is incided in the object lens 21 as diverging light.And, when the laser that utilizes wavelength 655nm writes down DVD70 or regenerates, incide in the object lens 21 as convergence light.All make optical system bring into play function under any one situation as limited system.As a result, utilize the object lens 21 of present embodiment make the operating distance of laser focusing when CD80 for 0.43mm more than, enough big.

In addition, the object lens 21 of present embodiment are with respect to the position of the best (minimum) corrugated aberration of 405nm, change at the corrugated aberration of the best (minimum) of the RMS corrugated aberration of wavelength 406m, 404nm is about ± 0.5 μ m, has good wavelength dispersion compensation performance.

And in the object lens 21 of present embodiment, the maximal value at the angle that is become with reference plane with section that arbitrfary point on first 31i, the 31o face joins is 65.6deg, can easily make the aspheric mould that is used to form object lens.

And for the object lens 21 of present embodiment, because reference lens 21a is K-VC79, connecting airtight lens 21b is polycarbonate, so, can connect airtight and be formed on the formed reference lens 1a connecting airtight lens 1b.

As mentioned above, the object lens 21 of present embodiment when each CD corresponding with these wavelength carried out record regenerating, show the good optical performance at each CD utilizing wavelength 405nm, 660nm, these three kinds of light sources of 785nm respectively.Utilized the above-mentioned optical head or the optical disc apparatus of these object lens to carry out good record or regeneration to BD, DVD, these three kinds of CDs of CD.

In addition, in embodiment 1 and 2, used K-VC79 (nd=1.610, υ d=57.8), utilized polycarbonate (nd=1.584, υ d=30.1) as the material of connecting airtight lens 1b and connecting airtight lens 21b as the material of reference lens 1a and reference lens 21a.But material is not limited to these materials.As long as reference lens and connect airtight lens and be made of different materials is made as nd1 in the refractive index with reference lens, Abbe number is made as υ d1, and the refractive index of connecting airtight lens is made as nd2, and is when Abbe number is made as υ d2, satisfied

Nd1＞nd2 and υ d1＞υ d2 ... (formula 2)

Relation get final product.

By the such refractive index and the combination of Abbe number, as mentioned above, can proofread and correct to change (chromatic aberation on the axle) in the other direction by the lens that connect airtight, can obtain the situation of good wavelength dispersion compensation performance with concavees lens effect to the best image point position that in reference lens, produces as convex lens.

And preferred index nd1 is,

1.60＜υ d＜1.85 ... (formula 3),

Refractive index n d2 is,

1.45＜υ d1＜1.60 ... (formula 4),

Abbe number υ d1 is,

40＜υ d1＜60 ... (formula 5),

Abbe number υ d2 is,

20＜υ d2＜40 ... (formula 6).

By selecting such refractive index and Abbe number,, can obtain good wavelength dispersion compensation performance with of the combination of general optics with glass material and resin material.

The material of preferred reference lens is a glass material.Especially in order to prolong the die life when being shaped, be easy to cheapness manufacturing, preferably the glass transformation temperature with this glass material is made as below 550 ℃.As the material of concrete reference lens, the glass that preferably uses optics to use, for example preferably K-VC79, K-VC78, K-VC81, K-VC89 etc.

On the other hand, the material of preferably connecting airtight lens is resin materials.Preferably connecting airtight property of relative datum lens is outstanding, transmitance is high and photostability, material that moisture-proof is outstanding.

Form in reference lens in order to connect airtight, the glass transformation temperature of this resin material must be lower than the glass transformation temperature of the employed glass material of reference lens.General optics is about 350 degree～550 degree with the glass transformation temperature of glass material, optics such as especially above-mentioned K-VC79, K-VC78, K-VC81, K-VC89 are about 500 degree with the glass transformation temperature of glass material, therefore, the glass transformation temperature of the resin material that preferably connects airtight lens and adopted is below 300 degree.

Like this, connect airtight the reference lens that forms in glass material, do not need reference lens and the contraposition of connecting airtight face of connecting airtight lens by the lens that connect airtight with resin material.

On the other hand, by the object lens that lens constitute that connect airtight of the reference lens of glass material and other glass materials, very outstanding aspect against weather, moisture-proof.Here, if at the glass transformation temperature of reference lens with connect airtight and have to a certain degree poor aspect the glass transformation temperature of lens, the lens that connect airtight of other glass materials that then can be shaped at the reference lens of glass material.The difference of the glass transformation temperature under preferred this situation is more than 200 degree.In addition, under the situation of connecting airtight lens of the reference lens of so using glass material and other glass materials, preferred reference lens and connect airtight lens and bond together by cementing agent.

And, can also will connect airtight lens as ultraviolet hardening resin, be formed on the reference lens by so-called photopolymer method (2P).By utilizing the photopolymer method to form, do not need reference lens and the contraposition of connecting airtight face of connecting airtight lens.

And, by the reference lens that will be formed separately with connect airtight on the anchor clamps that lens are inserted into regulation, can also be similar to and keep reference lens with connecting airtight and connect airtight lens.According to such formation, also can realize effect of the present invention.

In addition, in the object lens 1 and 21 of embodiment 1 and 2, all lens effective coverages of first, second (connecting airtight face) and the 3rd, all having public domain (central effective coverage) that comprises lens axis and the reserved area (peripheral effective coverage) that does not comprise lens axis to constitute, is respectively that the situation of different aspherical shape is narrated to the public domain and the reserved area of face separately.

But the present invention is not limited to this, and the lens effective coverage of at least one face can be to possess public domain and the reserved area of being represented by different separately aspherical shape in for example first～the 3rd.In addition, also can be that the lens effective coverage of at least one face is the formation with zone more than three.

And, effective coverage second (connecting airtight face), possess under the situation of the public domain represented by variant aspherical shape and reserved area, when section that will join with arbitrfary point on the face in second the effective coverage and plane perpendicular to optical axis are that the reference plane angulation is when being made as θ, by according to boundary at public domain and reserved area, the mode that θ value and its symbol change constitutes public domain and reserved area, can significantly change the amount of spherical aberration that public domain and reserved area are produced.

" symbol of θ " is defined as follows and gets final product.For example, be to be that the solid of revolution at center is when being prerequisite with the optical axis with lens, as long as in lens profile figure (Fig. 1 etc.), judging that clockwise/counterclockwise clamping " tangent line " of boundary of public domain and reserved area " tangent line " " point ", the public domain and reserved area, get final product with the angle of " datum line " of expression reference plane.

In addition, above-mentioned " θ value and its symbol change " can further utilize other computing method to judge.For example, regulation comprises the suitable three-dimensional system of coordinate of above-mentioned object lens, calculates the inner product of the normal line vector C of the inner product of the normal line vector C of the normal line vector in section at the some a place in the public domain and reference plane, the normal line vector in section that reaches the interior some b place of the reserved area of points of proximity a and reference plane.The comparison of the absolute value by each inner product, variation has taken place in the value that can be judged as θ, the comparison of the symbol by each inner product, variation has taken place in the symbol that can be judged as θ.

For example, owing to when the recording/reproducing of the DVD70 shown in Fig. 2 (b), only write down, regenerate by the public domain, so common element or the formation that does not incide the mode limiting aperture of reserved area according to laser is necessary.But according to above-mentioned formation, the laser that incides reserved area can produce very large spherical aberration on DVD70, do not form luminous point, does not need to control the element or the formation in aperture in fact.

And the public domain by at least one face in first, second and the 3rd and the boundary of reserved area are provided with the jump of optical mode, and the discrete of phase place that can produce the intersection at public domain and reserved area proofreaied and correct.

In addition, the aberration during for the record of proofreading and correct BD60 or regeneration can make first reserved area have diffraction structure.Constitute the littler effect of corrugated aberration in the time of to obtain to make record or regeneration BD60 according to this.

Preferred diffraction structure is designed to make with the diffraction efficiency more than 80% laser diffraction of provision wavelengths (under embodiment 1 and 2 the object lens 1 and 21 situations, wavelength is 405nm).

Thereby make laser focusing to the optical system that the information recording layer of each CD of BD, DVD and these three kinds of CD is used to carry out recording of information or regeneration to the object lens 1 and 21 of above-mentioned embodiment 1 and 2, be illustrated.But the present invention is not limited to BD.

In addition, the number with the information recording layer of CD in explanation so far is made as 1, but also can be a plurality of.When having a plurality of information recording layer, above-mentioned " protective substrate thickness " means: be present in from the surface of the CD of laser light incident side to as thickness the information recording layer of the object of information record or regeneration, hyaline layer.The information recording layer that can also in this hyaline layer, comprise the object that does not write down or regenerate as information.

(embodiment 3)

Figure 13～15 expressions constitute based on the summary of the optical head 7 of present embodiment.The state of the light path when Figure 13～15 have represented respectively that CD is BD60, DVD70, CD80 in the optical head 7.

Optical head 7 has object lens 1, light source 2, beam splitter 3, collimation lens 4, limited aperture element 5 and photo detector 6.

Object lens 1 are based on the object lens of embodiment 1.

Light source 2 can be distinguished the bluish violet color laser of emission wavelength 405nm, the red laser of wavelength 655nm and the infrared laser of wavelength 785nm.

Limited aperture element 5 has corresponding light wavelength from light emitted, makes the function of the beam diameter variation of the light beam that incides object lens 1.The reason that limited aperture element 5 is set is that when the information at BD60, DVD70, CD80 write down or regenerates, employed separately numerical aperture was different.Aperture control element 5 is made of diaphragm of mechanical diaphragm, optical profile type etc.

As the example of mechanical diaphragm, can prepare a plurality of tabular bodys with hole of the diameter corresponding with numerical aperture, constitute the mechanism that the kind according to CD exchanges.And, can use wavelength selectivity dichroic filter or dichroic prism etc. as the example of optical profile type diaphragm.Wherein, mechanical type diaphragm and optical profile type diaphragm are example.The present invention is not limited to the two.

In addition, limited aperture element 5 limits numerical aperture according to the control signal that is used to control numerical aperture.Control signal is sent by differentiating the optical disc controller (aftermentioned) that whether has loaded any one CD among BD60, DVD70, the CD80.Optical disc controller (control part) when optical head is installed on optical disc apparatus, is arranged on the optical disc apparatus in the lump.

For beam splitter 3, collimation lens 4 and photo detector 6, can adopt known optical element.

Then, the action of the optical head 7 of information record or regeneration is carried out in narration to BD60, DVD70, each CD of CD80.

Among Figure 13, the bluish violet color laser transmitted beam separation vessel 3 of the wavelength 405nm that launches from light source 2, collimated lens 4 are transformed to approximate directional light, by limited aperture element 5 limiting apertures so that NA is 0.85.Then, bluish violet color laser is crossed the information recording layer of protective substrate optically focused to BD60 based on object lens 1, and as luminous point.By the laser after the reflection of the information recording layer of BD60, see through object lens 1, limited aperture element 5, collimation lens 4 once more, reflected by beam splitter 3, import in the photo detector 6.

Equally, in Figure 14, the red laser of the wavelength 655nm that launches from light source 2, transmitted beam separation vessel 3, collimated lens 4 are transformed to convergence light, by limited aperture element 5 control apertures so that NA becomes 0.60.Then, red laser is crossed the information recording layer of protective substrate optically focused to DVD70 based on object lens 1, and becomes luminous point.Seen through object lens 1, limited aperture element 5, collimation lens 4 once more by the laser after the reflection of the information recording layer of DVD70, reflected, import in the photo detector 6 by beam splitter 3.

As shown in figure 14, when DVD70 being write down or regenerate, collimation lens 4 writes down or the position of collimation lens 4 when regenerating BD60 from shown in Figure 13, along optical axis direction object lens 1 side shifting.Thus, make the emergent light of collimation lens 4 become convergence light and incide in the object lens 1, and with the information recording layer of laser focusing to DVD70.

In the present embodiment,, collimation lens 4 is provided with driving mechanism (not shown) for being moved.Driving mechanism is based on moving of drive signal control collimation lens 4.Drive signal is exported from above-mentioned optical disc controller.Driving mechanism based on this drive signal, makes collimation lens move to the corresponding position of wavelength of light emitted with institute along optical axis direction.Thus, the position of the collimation lens 4 when record or regeneration DVD70, the position of the collimation lens 4 during from record or regeneration BD60 moves to object lens 1 side.In addition, owing in ensuing embodiment, describe the formation and the action of driving mechanism in detail, so, this explanation can be quoted and be explanation based on the drive unit of present embodiment.

And, in Figure 15, the infrared laser transmitted beam separation vessel 3 of the wavelength 785nm that launches from light source 2, collimated lens 4 are transformed to diverging light, by limited aperture element 5 control apertures so that NA becomes 0.47.Then, infrared laser is crossed the information recording layer of protective substrate optically focused to CD80 based on object lens 1, as luminous point.Seen through object lens 1, limited aperture element 5, collimation lens 4 once more by the laser after the reflection of the information recording layer of CD80, reflected, import in the photo detector 6 by beam splitter 3.

As understandable from Figure 15, when CD80 being write down or regenerate, collimation lens 4 also writes down or the position of collimation lens 4 when regenerating BD60 from shown in Figure 13 based on driving mechanism (not shown), moves to light source 2 sides along optical axis.Thus, make the emergent light of collimation lens 4 become diverging light and incide in the object lens 1, with the information recording layer of laser focusing to CD80.

In addition, for the convergence of switched laser, disperse and be an example along the formation that optical axis moves collimation lens.As other example, also can switch lens self by the kind of the CD that writes down or regenerate.

Above-mentioned optical head is had the related object lens of embodiment 1 to be illustrated.But also can replace object lens 1 and adopt the related object lens 21 of embodiment 2.

And, as illustrated in the embodiment 1, object lens 1 are when record or regeneration BD60, and the change of the best image point position of the RMS corrugated aberration of the change of wavelength ± 1nm of centre wavelength 405nm is about ± 0.5 μ m relatively, has good wavelength dispersion compensation performance.But, be used for chromatic aberation correcting element that the change of the best image point position that produces because of wavelength change is proofreaied and correct in order further to improve the function of record or regeneration, more preferably to possess.Chromatic aberation correcting element under this situation can utilize the achromat of 2 pieces of general formations etc.

And, in above-mentioned optical head 7, the bluish violet color laser from light source 2 emission wavelength 405nm, the red laser of wavelength 655nm, the infrared laser of wavelength 785nm have been described.But the present invention is not limited to this.For example also can launch bluish violet color laser, red laser and infrared laser respectively from a plurality of light sources that are configured in diverse location.For example light source 2 can constitute and only launch bluish violet color laser, launches red laser and infrared laser from the light source (not shown) different with light source 2.Red laser and infrared laser or bluish violet color laser can be imported in the collimation lens 4 by optical elements such as semi-permeable and semi-reflecting mirror.Certainly, also can be provided for launching three light sources of three-wavelength laser separately.

In addition, each Wavelength of Laser is made as 405nm, 655nm and 785nm, but these can not fixed values also.As described in the description of the present embodiment beginning, so long as the wavelength of specialized range then can adopt equally.

In addition, the photo detector 6 of present embodiment is configured in the position different with light source 2, but for example also light source 2 can be configured to identical position with photo detector 6.And, do not need a photo detector 6 to receive all laser.For example, three photo detectors (not shown) can be set, receive bluish violet color laser, red laser, infrared laser respectively.And, can also be provided with in the three-wavelength and photo detector that wavelength receives and to a remaining photo detector that wavelength receives.

In addition, CD is not limited to the combination of BD60, DVD70, CD80.Also can substitute BD and constitute: (protective substrate thickness is about 0.6mm with other high density compact disc; NA is 0.65), (protective substrate thickness is about 0.6mm to DVD; NA is 0.60), the such different types of CD correspondence of CD (protective substrate thickness is about 1.2mm, and NA is 0.47).

(embodiment 4)

Figure 16～18 expressions constitute based on the summary of the optical head 100 of present embodiment.The state of the light path in the optical head 100 when Figure 16～18 have represented respectively that CD is BD60, DVD70, CD80.

Optical head 100 has object lens 1, light source 42, beam splitter 43, relay lens 44, dichroic prism 45, collimation lens 46, chromatic aberation correcting element 47, limited aperture element 48, photo detector 49 and is subjected to the luminous body member 50 of light.

Object lens 1 are the related object lens of embodiment 1.

Light source 42 emission bluish violet color lasers.

Limited aperture element 48, have corresponding with the light wavelength that goes out from light emitted, the function that the beam diameter that incides the light beam in the object lens 1 is changed.The formation of limited aperture element 48 is identical with the limited aperture element 5 shown in Figure 13～15 (embodiment 3).

Photo detector 49 receives bluish violet color laser.

Be subjected to 50 emissions of the luminous body member of light, receive red laser and infrared laser.The light of the wavelength that dichroic prism 45 reflection regulations are following.Comprise the wavelength 405nm of bluish violet color laser in " wavelength that regulation is following ", but do not comprise the wavelength 655nm of red laser and the wavelength 785nm of infrared laser.That is, " regulation " is set between the wavelength 655nm of the wavelength 405nm of bluish violet color laser and red laser.

In addition, the protective substrate thickness as BD60 is about 0.1mm in principle, but if 2 layers BD, then protective substrate thickness is about 0.1mm or is about 0.075mm.

Then, the action of the optical head 7 of information record or regeneration is carried out in narration to BD60, DVD70, each CD of CD80.

At first, with reference to Figure 16, narration is carried out the action of the optical head 100 of recording of information or regeneration to BD60.The bluish violet color laser of the wavelength 405nm that launches from light source 42, transmitted beam separation vessel 43, relay lens 44.And then after by dichroic prism 45 reflection, collimated lens 46 are transformed to approximate directional light, see through chromatic aberation correcting element 47, by limited aperture element 48 limiting apertures so that NA becomes 0.85.Then, bluish violet color laser is crossed protective substrate as the information recording surface of luminous point optically focused to BD60 based on object lens 1.

Seen through object lens 1, limited aperture element 48, chromatic aberation correcting element 47, collimation lens 46 once more by the information recording surface laser light reflected of BD60, after dichroic prism 45 reflection, having been seen through relay lens 44, reflected by beam splitter 43, import in the photo detector 49.

Under the situation that BD60 is write down or regenerate, approximate directional light is incided in the object lens 1.Here, so-called " approximate directional light " is meant at protective substrate thickness and is about under the situation of 0.0875mm completely parallel light.Thus, in the information recording layer of BD60, spherical aberration is approximate to be designed to 0.On the other hand, be about at protective substrate thickness under the situation of 0.1mm, the light of dispersing is a little incided in the object lens 1, be about at protective substrate thickness under the situation of 0.075mm, make convergent light incident a little.Thus, in either event, can both make spherical aberration be approximately 0.

Equally, in Figure 17, see through dichroic prism 45 from the red laser that is subjected to the wavelength 655nm that the luminous body member 50 of light launches, the collimation lens 46 that is moved to object lens 1 side is transformed to convergence light, see through chromatic aberation correcting element 47, and by limited aperture element 48 limiting apertures so that NA becomes 0.60.Then, red laser is crossed protective substrate as the information recording surface of luminous point optically focused to DVD70 based on object lens 1.Seen through object lens 1, limited aperture element 48, chromatic aberation correcting element 47, collimation lens 46, dichroic prism 45 once more by the laser after the information recording surface of the DVD70 reflection, turn back to and be subjected to the luminous body member 50 of light and be received.

Among Figure 18, see through dichroic prism 45 from the infrared laser that is subjected to the wavelength 785nm that the luminous body member 50 of light launches, be moved to and be subjected to the collimation lens 46 of the luminous body member of light 50 sides to be transformed to diverging light, see through chromatic aberation correcting element 47, and by limited aperture element 48 limiting apertures so that NA becomes 0.47.Then, infrared laser is crossed protective substrate as the information recording surface of luminous point optically focused to CD80 based on object lens 1.Seen through object lens 1, limited aperture element 48, chromatic aberation correcting element 47, collimation lens 46, dichroic prism 45 once more by the laser after the information recording surface of the CD80 reflection, turn back to and be subjected to the luminous body member 50 of light and be received.

Under the situation that DVD70 is write down or regenerate, need be to object lens 1 incident object distance-the convergence light of 85mm; Under the situation that CD80 is write down or regenerate, need be to object lens 1 incident object distance+diverging light of 70mm.

Then, with reference to Figure 19 and Figure 20, the collimation lens 46 of present embodiment and the formation of periphery thereof are elaborated.

Figure 19 (a) and (b) expression collimation lens 46, and the summary that drives the driving mechanism of collimation lens 46 along optical axis direction constitute.Each has all represented the position of corresponding different collimation lens 46, the state that the diffusion of light is different.

Driving mechanism has stepper motor 56, screw shaft 57, lens holder 58 and guide rod 59.

Shown in Figure 19 (b), make screw shaft 57 rotation by drive stepping motor 56, can be along guide rod 59, along the optical axis direction of collimation lens, mobile collimation lens 46 and keep the lens holder 58 of collimation lens 46.

In addition, if utilize stepper motor 56, then do not need to monitor the position of the optical axis direction of collimation lens 46.Its reason is,, then rotates if be endowed pulse signal owing to stepper motor with the step units of predesignating, so, can correctly control rotation angle with the number of times of giving pulse signal.Therefore, even use location sensor etc. not also can correctly be controlled at collimation lens 46 optional position of optical axis direction according to the relation of the number of times of giving pulse signal and displacement.If adopt stepper motor 56, then do not need to monitor the formation of usefulness, have can simplified system advantage.

But, also can substitute stepper motor 56, for example by based on other formation such as the executive component of the driving of magnetic loop or piezoelectric element, collimation lens 46 is moved along optical axis direction.Because based on the executive component of the driving of magnetic loop or piezoelectric element, its drive part is little, so, the advantage of the miniaturization of suitable optical head had.

The state of the light when Figure 20 represents along optical axis direction driving collimation lens 46.The spherical aberration that produces because of the difference in thickness of the protective substrate of BD60; the dispersing of the laser that incides in the object lens 1, degree of convergence are changed; by producing the spherical aberration of the spherical aberration opposed polarity that produces with difference in thickness, can proofread and correct it because of protective substrate.

Therefore, be benchmark for example when the emergent light with collimation lens 6 becomes the Figure 20 (a) that is similar to directional light, shown in Figure 20 (b), when light source side moved, the emergent light of collimation lens 46 became diverging light with collimation lens 46.Thus, the spherical aberration that is produced in the time of can proofreading and correct the transparency carrier thickening of BD60.

On the other hand, when shown in Figure 20 (c), make collimation lens 46 when the object lens side shifting, the emergent light of collimation lens 46 becomes convergence light.Thus, the spherical aberration that is produced in the time of can proofreading and correct the transparency carrier attenuation of BD60.

Then, to making collimation lens 46 move, come the dispersing of switched laser, convergent action to be elaborated along optical axis direction.

The relation of the focal length of collimation lens 46 focal length of collimation lens 46 when receiving red laser from DVD70/CD80/infrared laser when Figure 21 represents to receive from the bluish violet color laser of BD60.

As shown in figure 21, the focal distance f c1 of the collimation lens 46 of present embodiment is 16mm, the multiplying power of the optical system of DVD70 and CD80 (optics multiplying power: collimation lens focal distance f c1/ objective focal length fo1=16.0mm/2.36mm) be about 6.8 times.This optics multiplying power according to DVD70 and CD80 being write down or light utilization ratio when regenerating and the viewpoint that edge (rim) intensity is guaranteed, decides.

And the focal distance f r1 of relay lens 44 is-12mm (bearing) that collimation lens 46 is 10mm with the lenticular spacing of relay lens 44 from d (air conversion).At this moment, collimation lens 46 can be obtained by (formula 2) with the synthetic focal distance f s of relay lens 44.

Fs=fc1 * fr1/ (fc1+fr1-d) ... (formula 2)

According to (formula 2), synthetic focal distance f s is 32mm.That is, the optics multiplying power of BD60 (synthetic focal distance f s/ objective focal length fo1=32.0mm/2.3mm) is about 13.9 times.This optics multiplying power is according to BD60 being write down or the light utilization ratio when regenerating and the viewpoint that edge strength is guaranteed decide.

Shown in present embodiment, by clip dichroic prism 5 at the opposition side of collimation lens 46, be light source 2 sides configuration relay lens 44, the optics multiplying power when the optics multiplying power in the time of can be with record or regeneration BD60, record or regeneration DVD70, CD80 is made as setting respectively.

For example in the present embodiment, BD60 is determined to guarantee the optics multiplying power that necessary edge strength and light utilization ratio increase, DVD70, CD80 have been set in the optical head purposes that meets the DVD that to write down or to regenerate the extensively optics multiplying power of the universal specification that is subjected to the luminous body member 50 of light of institute.

Like this, can determine the focal length of collimation lens 46 and relay lens 44.And the luminous point of light source 42 is as long as be configured in and collimation lens 46 distance when the reference position, between the principal point when collimation lens 46 and relay lens 44 synthesize is the position of 32.0mm (air conversion).In addition, " reference position " is meant that the bluish violet color laser of launching from light source 42 becomes the position of the collimation lens 46 of directional light based on collimation lens 46.

And, be subjected to the luminous point of the luminous body member 50 of light, shown in Figure 22 (a), if be configured in and collimation lens 46 principal point when the said reference position, collimation lens 46 between distance be the position of 15.6mm (air conversion).

At this moment; being used for the protective substrate thickness 0.0875mm with BD60 is the center; protective substrate thickness comprises the discrete of CD and the displacement of the spherical aberration optical axis direction that proofread and correct, collimation lens 46 that produced when changing in the scope from 0.060mm to 0.115mm, for ± 1.0mm.

And, to DVD70 write down or when regenerating (Figure 17), collimation lens 46 to the displacement of object lens 1 direction (, the laser that penetrates from collimation lens 46 becomes the distance of object distance for the convergence light of-85mm) L1, with CD80 is write down or when regenerating (Figure 18), collimation lens 46 all is 3.4mm to the displacement that is subjected to the luminous body member of light 50 directions (, the laser that penetrates from collimation lens 46 becomes the distance of object distance for the diverging light of+70mm) L2.In addition, these displacements are values that collimation lens 46 and relay lens 44 are calculated as paraxial lens.

As described above, in the optics of present embodiment constitutes, the collimation lens 46 that can move at optical axis direction of the spherical aberration correction by will being used for BD60 originally, the optical system that is used for DVD70 and CD80 can be switched the incident angle (dispersing the degree of convergence) that incides the light in the object lens 1.Therefore, even under the different situation of the angle of the light in inciding object lens 1 (object point position), the red laser that also can be used in record or regeneration DVD70 be used to write down or the luminous point of the infrared laser of the CD80 that regenerates consistent, utilizable energy is enough launched the light source of the laser of two wavelength.And, consistent by the luminous point that so makes red laser and infrared laser, can also make the photo detector that receives each laser integrated.That is, that utilizes as present embodiment that two wavelength use is subjected to the luminous body member 50 of light, optics is constituted simplify.

Emission is used to write down or the red laser of the DVD70 that regenerates and being used to writes down or these both sides of infrared laser of the CD80 that regenerates, and receive the catoptrical luminous body member of light that is subjected to respectively, aspect the optical head purposes of DVD that can write down or regenerate, extensively popularize from DVD70 and CD80.Can obtain to be subjected to the luminous body member of light at an easy rate.By widening the movable range of collimation lens 46, laser is made as convergence or diverging light, can constitute optical head at an easy rate, be very effective.

In addition, illustrated in the present embodiment, utilization is incided in the object lens 1 at the bluish violet color laser that the mode with approximate directional light is used in record or regeneration BD60, the red laser that is used in record or regeneration DVD70 in the mode that restrains light incides in the object lens 1, the infrared laser that is used in record or regeneration CD80 in the diverging light mode incides the object lens that can obtain good aberration performance under the situation of object lens, the example of design optical head.But, BD60, DVD70, CD80 are write down or the object lens of regenerating carry out combination parallel, that restrain, disperse and are not limited to this to being used for.Its reason is their combination depends on what kind of object lens of design.

For example, be provided with that red laser that state with approximate directional light is used in record or regeneration BD60 and DVD70 incides in the object lens 1, the infrared laser that is used in record or regeneration CD80 in the mode of diverging light incides the object lens 1 in the object lens.If in CD80, need to import the diverging light of object distance for+70mm, then shown in Figure 22 (b), as long as be configured in by the luminous point of the luminous body member 50 of light, and the distance between the principal point of the collimation lens 46 of collimation lens 46 when the reference position is that the position of 14.1mm (air conversion) gets final product.In addition, under this situation DVD70 being write down or make when regenerating collimation lens 46 write down or make collimation lens 46 to the distance L 2 ' that is subjected to the luminous body member of light 50 side shiftings when regenerating to the distance L 1 ' of object lens 1 side shifting with to CD80, all is 1.9mm.

Equally, be provided with that bluish violet color laser that state with approximate directional light is used in record or regeneration BD60 incides in the object lens 1, the infrared laser that is used in record or regeneration DVD70 and CD80 in the mode of diverging light incides the object lens 1 in the object lens 1.So, for the luminous point binary that is subjected to the luminous body member 50 of light, the principal point distance apart from collimation lens 46 in the time of collimation lens 46 can being positioned at the reference position disposes forr a short time than the example shown in Figure 22 (b).

In addition,, also can consider following such lens,, then can obtain good aberration performance if, be used in the infrared laser incident of record or regeneration CD80 promptly in the mode of approximate directional light or convergence light as the design example of object lens.But, in mode laser is incided under the situation of object lens with approximate directional light or convergence light, the emergent light convergent position that can cause object lens is near object lens.As a result, the situation that incides object lens with the illustrated mode with diverging light of present embodiment is compared, and the object lens when CD80 being write down or regenerate diminish to the operating distance (WD, Working Distance) of CD80.For the CD of recordable type, the preferred motion distance is more than the 0.40mm, but in above-mentioned example, also little sometimes than 0.4mm.As a result, object lens and unfavorable conditions such as dish contacts can take place.Therefore, shown in present embodiment, the infrared laser that preferably is used in record or regeneration CD80 incides in the object lens 1 in the mode of diverging light.

In addition,, can also design following such object lens, promptly incide under the situation of object lens, can obtain good aberration performance at the bluish violet color laser that is used in record or regeneration BD60 with convergence light or diverging light as other example.But, the object lens of long light source of radiothermy and light NA write down or the situation of CD that regenerate, as BD under, from the viewpoints such as off-axis aberration performance that the mobile grade of guaranteeing with object lens accompanies, be preferred for writing down or the bluish violet color laser of the BD60 that regenerates incides in the object lens 1 in the mode of approximate directional light.

On the other hand, the NA of needed object lens is littler than the NA of the needed object lens of BD60 when record or regeneration DVD70.Therefore, even convergence light or diverging light incide in the object lens, also guarantee the off-axis aberration performance easily.And, in that convergence light is incided under the situation of object lens, also guarantee operating distance easily.

According to above reason, the red laser that more preferably bluish violet color laser that is used in record or regeneration BD60 according to the mode with approximate directional light incides in the object lens, the infrared laser that is used in record or regeneration CD80 in the mode of diverging light incides in the object lens, be used in record or regeneration DVD70 with approximate directional light, diverging light or convergence light incides the mode in the object lens, forms optical texture.

In above-mentioned example, be adjusted into divergent state or convergence state (promptly owing to being transformed to preferred state) owing to will incide laser in the object lens, so, collimation lens 46 is moved along optical axis direction.But also can adopt other method.

For example, form lens, by applying electric field, magnetic field or heat the index distribution of index distribution changeable material is changed, thereby change the focal length of lens by at least one index distribution changeable material.

For example, Figure 23 (a)～(c) has represented to be provided with in the object lens side of collimation lens 46 example of index distribution changeable material 54.Shown in Figure 23 (a)～(c), can make up the collimation lens 46 and the index distribution variable lens 54 of general glass material.Under this situation, the laser that goes out from light emitted sees through collimation lens 46 with defined terms, becomes approximate directional light, by when the index distribution variable lens 54, be transformed to desirablely disperse, convergence state, incide in the object lens.

And, also can substitute index distribution variable lens 54, the multiple non-Combination liquid different by refractive index constitute lens.By applying the voltage of the size corresponding with Wavelength of Laser, can make the interface curvature variation of this non-Combination liquid, thus, can also change dispersing/convergent degree (in other words, the focal length of lens) of laser.

In addition, the variable lens of these focal lengths can be shown in Figure 23 (a)～(c), as with collimation lens independently lens be inserted in the light path, from the miniaturization of optical head and the viewpoint that reduces cost, also can make it have the function of collimation lens.Like this, utilize again under the dispersing of the variable lens transformation laser of focal length/convergent situation because and make method that collimation lens moves along optical axis direction relatively, do not have drive part, so, have the advantage that can make integral miniaturization.

As mentioning in the explanation of above embodiment, the wavelength of LASER Light Source can be because change from the variation of regeneration the action switching of the luminous power (time) or environment temperature when the switching of operation of recording etc.Here, especially Wavelength of Laser is short more, and the influence that is brought by the material refractive index change change that cause, best image point position of the object lens that accompany with wavelength variation becomes big more.

The object lens 1 of present embodiment, with respect to the position of the best (minimum) corrugated aberration of 405nm, RMS corrugated aberration is about ± 0.5 μ m with respect to the change of the best (minimum) corrugated aberration of wavelength 406m, 404nm.Wherein, for the high density compact disc of recordable type, be used for chromatic aberation correcting element that the change of the best image point position that produces because of wavelength change is proofreaied and correct in order to improve record or regenerability, preferably to possess.

For example, Figure 24 represents the example of diffraction type chromatic aberation correcting element 47.Chromatic aberation correcting element 47 possesses the plane of refraction that has towards the recessed lens power of light incident side (light source side), and possesses the diffraction surfaces that has towards the protruding optical power of exiting side (object lens side).

Chromatic aberation correcting element 47 is under the reference wavelength 405nm of bluish violet color laser, and recessed optical power equates with protruding optical power, as afocal lens performance function.On the other hand, under the elongated situation of optical maser wavelength, it is big that angle of diffraction in the diffraction surfaces becomes, and makes protruding optical power strengthen, in incident under the situation of directional light as the lens performance function that penetrates convergence light.On the contrary, under the situation that optical maser wavelength shortens, the angle of diffraction in the diffraction surfaces diminishes, and makes recessed optical power grow, in incident under the situation of directional light as the lens performance function of outgoing diverging light.Its mode according to the change of offsetting the best image point position that is produced in the object lens 1 is brought into play function.

In addition,, then do not limit such diffraction type chromatic aberation correcting element, can also utilize the achromat of 2 pieces of general formations if be defined as the function that chromatic aberation is proofreaied and correct.

Corrugated aberration diagram when Figure 25 (a)～(d) has represented that BD60 carried out record or regeneration.The PX axle is represented the axle vertical with optical axis.And the longitudinal axis is represented the corrugated aberration, and smallest scale is represented-1 λ, maximum expression+1 λ.

Figure 25 (a) is the corrugated aberration diagram when utilizing design wavelength for the laser of 405nm BD60 (substrate thickness is about 0.0875mm) to be carried out record or regeneration, has represented good characteristic.

Then, Figure 25 (b) utilizes the laser of the wavelength 410nm departed from design wavelength that BD60 is write down or the corrugated aberration diagram when regenerating.According to Figure 25 (b) as can be known, on the basis of three spherical aberrations, also produced the spherical aberration of high order.For three spherical aberrations, move about 0.6mm, incide in the object lens 1 to light source side by making collimation lens 6 in the diverging light mode, can proofread and correct to as Figure 25 (c).

But, for the high order spherical aberration more than 5 times remaining among Figure 25 (c), can't proofread and correct by moving of collimation lens 6.

Therefore, can utilize the phase place jump, the high order spherical aberration that produces accompanying with this wavelength variation is proofreaied and correct.

As being expressed as " lens face (recessed)+phase place jump " among Figure 24, the concavees lens face at chromatic aberation correcting element 7 in the present embodiment is formed with the phase place jump.

Figure 26 represents the example of the shape of phase place jump.In Figure 26, transverse axis is represented the radius of chromatic aberation correcting element 47, and the longitudinal axis is illustrated in the phase shift amount that causes because of the phase place jump in this radius.The magnitude of misalignment of phase place integral multiple when design wavelength 405nm is made as 1 λ, wavelength X is represented.

As shown in figure 26, in the present embodiment, the laser of wavelength X is poor through the optical path length that is produced when the phase place jump, is set to the integral multiple (10 λ and 20 λ) of 10 λ.The phase place jump of the integral multiple by being made as 10 λ can produce the high order spherical aberration corresponding with the wavelength variation of bluish violet color laser under situation the about corrugated of red laser (wavelength 655nm) and infrared laser (wavelength 785nm) not being impacted.The corrugated shape that Figure 26 (d) expression is proofreaied and correct based on this phase place jump.

The phase place jump can be used as independently that optical element is configured in the light path, also can be shown in present embodiment, and by being formed on the concavees lens face of chromatic aberation correcting element 47, integrally formed with plane of refraction.And, can also cut down number of components, can realize miniaturization and densification, therefore be more preferably.

As described above, the spherical aberration that produces with being accompanied by wavelength variation and three spherical aberration corrections realizing based on moving of collimation lens 46 together utilize the phase place jump, can also proofread and correct the high order spherical aberration.

More than, the optical head 100 of present embodiment has the light source of bluish violet color laser, red laser, these three kinds of wavelength of infrared laser, and the record regenerating of the pairing CD of these wavelength had the good optical performance respectively, the optical head that has utilized these object lens for example can write down well or regenerates BD, DVD, these three kinds of CDs of CD.

In addition, the wavelength of each light source, the position that each light source is set, the position that photo detector 9 is set can suitably be changed.Also can divide and be subjected to the luminous body member 50 of light for each light source and photo detector.On the contrary, can also be only that all light sources is integrated, and then all photo detectors can be configured to identical position, as being subjected to the luminous body member of light.

And CD is not limited to the combination of BD60, DVD70, CD80.Also can replace BD; (protective substrate thickness is about 0.6mm for formation and other high density compact disc; NA is 0.65), DVD (protective substrate thickness is about 0.6mm, and NA is 0.60), the such different types of CD correspondence of CD (protective substrate thickness is about 1.2mm, and NA is 0.47).

The object lens 1 that above-mentioned optical head is had based on embodiment are illustrated.But also can replace object lens 1, and adopt object lens 21 based on embodiment 2.

(embodiment 5)

Figure 27 represents to constitute based on the summary of the optical disc apparatus 30 of present embodiment.

Optical disc apparatus 30 possesses optical head 20, disc drives portion 35, control part 36.Wherein, Figure 27 has represented to be filled into the BD60 in the optical disc apparatus 30, but this is for convenience of explanation.Certainly, BD60 can be exchanged into DVD70 or CD80.Wherein, BD60, DVD70 and CD80 can take off from optical disc apparatus 30, are not the inscapes of optical disc apparatus 30.Below unless otherwise specified, be that BD60 describes all with CD.

Disc drives portion 35 is motors that rotation drives BD60.

Optical head 20 is based on the optical head of embodiment 3 or 4.

Control part 36 is so-called optical disc controllers, carries out the driving and the control of disc drives portion 35 and optical head 20.And control part 36 also carries out being subjected to the control signal of light, the signal Processing of information signal by optical head 20, makes exchange (interface) information signal between the inscape of optical disc apparatus 30 and the external unit (for example main frame).

Example to the processing of control part 36 describes.35 outputs of 36 pairs of disc drives portions of control part are used to rotate the control signal that drives the CD that is loaded.Then, be that the CD that is loaded is BD60 if control part 36 is differentiated, then indicate from the light emitted bluish violet color laser.The driving mechanism of the collimation lens that is mentioned in embodiment 3 and 4 (for example Figure 19 (a) reaches (b)) sends drive signal then, and the control collimation lens moves to optical axis direction.Thus, will be approximate directional light from the laser beam transformation that light emitted goes out by collimation lens.And, also limited aperture element 5 being sent the control signal that is used to adjust the aperture, limiting aperture in limited aperture element 5 is so that NA is 0.85.

Because optical disc apparatus 30 is equipped with embodiment 3 or 4 described any one optical head,, writes down well respectively or regenerate so the optical disc apparatus 30 of present embodiment can be to the record regenerating of a plurality of light sources and the CD corresponding with them.

Industrial utilizability

Can realize record or the regeneration of high density compact disc, DVD and CD owing to utilized the optical head of object lens of the present invention, so, can simplify the formation of optical head, realize the raising of productivity ratio, and, can make optical disc apparatus self miniaturization, lightweight and high precision int, and optical disc apparatus can be provided at an easy rate.

Claims (48)

1, a kind of object lens are assembled in optical head, wherein,

Described object lens comprise first lens and second lens that connected airtight in fact according to the mode of mutual optical axis unanimity, and whole as convex lens performance function,

Described first lens and described second lens have respectively: comprise the core of optical axis and be positioned at described core around peripheral part,

The core of described first lens is brought into play function as convex lens,

The core of described second lens is brought into play function as concavees lens,

Be made as nd1 in the refractive index that the d line (wavelength 587.56nm) of described first lens is located, to utilize the represented Abbe number of refractive index of d line, F line (wavelength 486.13nm) and C line (wavelength 656.56nm) to be made as υ d1, the refractive index of the d line of described second lens is made as nd2, when the represented Abbe number of refractive index that utilizes d line, F line and C line is made as υ d2, satisfy nd1＞nd2 and υ d1＞υ d2.

2, object lens according to claim 1 is characterized in that,

Described refractive index n d1 satisfies 1.60＜nd1＜1.85, and

Described refractive index n d2 satisfies 1.45＜nd2＜1.60, and

Described Abbe number υ d1 satisfies 40＜υ d1＜60, and

Described Abbe number υ d2 satisfies 20＜υ d2＜40.

3, object lens according to claim 1 is characterized in that,

Described first lens and described second lens engage or bond together.

4, object lens according to claim 1 is characterized in that,

Also possess the anchor clamps that described first lens and described second lens are connected airtight in fact, keep.

5, object lens according to claim 1 is characterized in that,

Described first lens are formed by glass material, and described second lens are formed by resin material.

6, object lens according to claim 5 is characterized in that,

The glass transformation temperature of described resin material is below 300 degree.

7, object lens according to claim 5 is characterized in that,

Described second lens are formed by ultraviolet hardening resin.

8, object lens according to claim 5 is characterized in that,

Described resin material is a polycarbonate.

9, object lens according to claim 1 is characterized in that,

Described first lens and described second lens are formed by glass material.

10, object lens according to claim 9 is characterized in that,

Described first lens are formed by the mutual different glass material of glass transformation temperature with described second lens.

11, object lens according to claim 9 is characterized in that,

The difference of the glass transformation temperature of the glass material of the glass transformation temperature of the glass material of described first lens and described second lens is more than 200 degree.

12, object lens according to claim 1 is characterized in that,

Described object lens have three lens faces with described optical axis intersection, do not face first lens face of a lens face side, that be described first lens mutually with described second lens that is:; Second lens face of described first lens that formation is connected airtight in fact and the boundary of described second lens; And the 3rd lens face of not facing a lens face side, that be described second lens with described first lens mutually,

In the effective coverage of at least one lens face of described first lens face, described second lens face and described the 3rd lens face, comprise the central effective coverage and the peripheral effective coverage on every side that is positioned at described middle section of optical axis, form by different aspherical shape.

13, object lens according to claim 12 is characterized in that,

For described first lens face, described second lens face and described the 3rd lens face, described middle section is separately formed by different aspherical shape with described neighboring area.

14, object lens according to claim 12 is characterized in that,

In the section that will join with the arbitrfary point on the face in effective diameter of described second lens face, be reference plane angulation when being made as θ with the plane vertical with optical axis,

At the central effective coverage of described second lens face and the intersection of peripheral effective coverage, the value of described θ changes.

15, object lens according to claim 14 is characterized in that,

At the central effective coverage of described second lens face and the intersection of peripheral effective coverage, at least one side of the absolute value of described θ and symbol changes.

16, object lens according to claim 12 is characterized in that,

At described first lens face, described second lens face and the described middle section that at least one lens face had of described the 3rd lens face and the intersection of described neighboring area, be provided with optical jump.

17, object lens according to claim 12 is characterized in that,

The peripheral effective coverage of described first lens face possesses the diffraction structure of the light of the provision wavelengths made from the diffraction efficiency diffraction more than 80%.

18, a kind of optical head, wherein,

Possess: a plurality of light sources of the light of emission different wave length; And the object lens put down in writing of the light convergent claim 12 that makes an emission from described a plurality of light sources.

19, optical head according to claim 18 is characterized in that,

Described object lens utilize described core and described peripheral part, make the light convergence from first light source in described a plurality of light sources,

In fact only utilize described core, make light convergence from the secondary light source in described a plurality of light sources.

20, optical head according to claim 19 is characterized in that,

Described first light source is compared with described secondary light source, the light of emission shorter wavelength.

21, optical head according to claim 20 is characterized in that,

Also possess transformation component, described transformation component is transformed to approximate directional light, diverging light or convergence light according to light wavelength with described light, and it is incided in the described object lens.

22, optical head according to claim 21 is characterized in that,

Described transformation component will be transformed to approximate directional light from the light that described first light emitted goes out.

23, optical head according to claim 21 is characterized in that,

Described transformation component will be transformed to convergence light, diverging light or approximate directional light from the light that described secondary light source is launched.

24, optical head according to claim 21 is characterized in that,

Also possess the 3rd light source, described the 3rd light source is compared with described secondary light source with described first light source, launches more long wavelength's light,

Described transformation component will be transformed to diverging light from the light that described the 3rd light emitted goes out.

25, optical head according to claim 18 is characterized in that,

Also possess the light wavelength that goes out according to from light emitted, limit the limited aperture portion of the beam diameter of described light.

26, optical head according to claim 19 is characterized in that,

Also possess the 3rd light source, described the 3rd light source is compared with described secondary light source with described first light source, launches more long wavelength's light,

The light of the described first light emitted wavelength X 1, the light of described secondary light source emission wavelength lambda 2, the light of described the 3rd light emitted wavelength X 3, described wavelength X 1, described wavelength X 2 and described wavelength X 3 satisfy

350nm＜λ1＜450nm，

600nm＜λ2＜700nm，

700nm＜λ3＜850nm。

27, optical head according to claim 26 is characterized in that,

Also possess: transformation component, it is used for the light of described wavelength X 1 is transformed to approximate directional light, and the light of described wavelength X 2 is transformed to convergence light, and the light of described wavelength X 3 is transformed to diverging light and it is incided in the described object lens.

28, optical head according to claim 26 is characterized in that,

Also possess the chromatic aberation correcting element that is used for the correcting colour aberration,

The chromatic aberation of the described object lens that described chromatic aberation correcting element produces the light wavelength change that is accompanied by described wavelength X 1 is proofreaied and correct.

29, optical head according to claim 26 is characterized in that,

In light time by described object lens optically focused wavelength X 3, the arbitrfary point in the effective coverage of described object lens with by optically focused the interval W of optical recording media of light, more than 0.30mm.

30, optical head according to claim 27 is characterized in that,

When the light that makes described wavelength X 1 was concentrated on optical recording media, the thickness at the focus place of described light because of the light transmission layer of optical recording media produced spherical aberration,

The spherical aberration that described transformation component produces the focus place of the light of described wavelength X 1 changes.

31, optical head according to claim 26 is characterized in that,

Described transformation component possesses: collimation lens, and it makes the light of described wavelength X 1 incide described object lens as approximate directional light at least; And drive division, its based on the corresponding drive signal of institute's wavelength of light emitted, described collimation lens is moved along optical axis direction.

32, optical head according to claim 31 is characterized in that,

When the position that the light that can make described wavelength X 1 is incided the described collimation lens in the described object lens as approximate directional light is made as the reference position,

Described drive division according to the drive signal corresponding with the light of described wavelength X 2, makes described collimation lens move from the direction of described reference position to described object lens, thereby the light of described wavelength X 2 is incided in the described object lens,

According to the drive signal corresponding, described collimation lens is moved from described reference position to the direction opposite with described object lens, thereby the light of described wavelength X 3 is incided in the described object lens with the light of described wavelength X 3.

33, optical head according to claim 26 is characterized in that,

Described transformation component utilizes the index distribution changeable material to constitute at least, and the index distribution of described index distribution changeable material because of electric field, magnetic field or the heat that applies from the outside accordingly with the institute wavelength of light emitted, and changes.

34, optical head according to claim 26 is characterized in that,

Described transformation component is the lens that utilize the different multiple non-Combination liquid of refractive index to constitute, the interface of described multiple non-Combination liquid, and corresponding to institute's wavelength of light emitted, its curvature changes.

35, optical head according to claim 26 is characterized in that,

Described secondary light source and described the 3rd light source are configured in roughly the same position.

36, optical head according to claim 26 is characterized in that,

Described secondary light source and described the 3rd light source are by integrated.

37, optical head according to claim 26 is characterized in that,

Between described first light source and the described transformation component and have only on the light path that the light of described wavelength X 1 passes through, also possesses relay lens with negative focal length.

38, optical head according to claim 28 is characterized in that,

In described chromatic aberation correcting element, be provided with the phase place jump,

Described phase place jump constitutes, the difference of the optical path length that is produced during the described phase place jump of the light transmission of described wavelength X 1 is about 10 times of described wavelength X 1, thus, the light wavelength that can proofread and correct because of described wavelength X 1 changes the spherical aberration that produces in the focal position of described light.

39, optical head according to claim 26 is characterized in that,

Also possess for the part of the light of described wavelength X 1 optical element as phase place jump performance function,

The difference of the optical path length that is produced during the described phase place jump of the light transmission that described phase place jump constitutes described wavelength X 1 is about 10 times of described wavelength X 1, thus, the light wavelength that can proofread and correct because of described wavelength X 1 changes the spherical aberration that produces in the focal position of described light.

40, according to the described optical head of claim 38, it is characterized in that,

In the spherical aberration that is accompanied by the light wavelength change of described wavelength X 1 and produces,

Described transformation component is mainly proofreaied and correct spherical aberration three times,

The main number of corrections of described phase place jump is the spherical aberration more than five times.

41, a kind of optical drive possesses: the described optical head of claim 18, be used to rotate motor that drives optical recording media and the control part of controlling described optical head and described motor.

42, a kind of object lens are assembled in optical head, wherein,

Described object lens comprise first lens and second lens that connected airtight in fact according to the mode of mutual optical axis unanimity, and whole as convex lens performance function,

Described first lens and described second lens have respectively: the core that comprises optical axis; And the peripheral part on every side that is positioned at described core,

The core of described first lens is brought into play function as convex lens,

The core of described second lens is brought into play function as concavees lens,

With at least one lens face described optical axis intersection, described object lens, have: the peripheral effective coverage that comprises the central effective coverage of described optical axis and do not comprise described optical axis, described central effective coverage forms different aspherical shape with described peripheral effective coverage.

43, according to the described object lens of claim 42, it is characterized in that,

By described first lens and described second lens regulation: not a side of facing mutually with described second lens, be first lens face of the lens face of described first lens; Second lens face of described first lens that formation is connected airtight in fact and the boundary of described second lens; And a side of not facing mutually with described first lens, be the 3rd lens face of the lens face of described second lens,

In the effective coverage of at least one lens face of described first lens face, described second lens face and described the 3rd lens face, the middle section that comprises optical axis is formed by different aspherical shape with the neighboring area on every side that is positioned at described middle section.

44, according to the described object lens of claim 43, it is characterized in that,

For described first lens face, described second lens face and described the 3rd lens face, described middle section separately and described neighboring area are formed by different aspherical shape.

45, according to the described object lens of claim 43, it is characterized in that,

In the section that will join with the arbitrfary point on the face in the effective diameter of described second lens face, with plane perpendicular to optical axis be the reference plane angulation, when being made as θ,

At the central effective coverage of described second lens face and the intersection of peripheral effective coverage, the value of described θ changes.

46, according to the described object lens of claim 45, it is characterized in that,

At the central effective coverage of described second lens face and the intersection of peripheral effective coverage, at least one side of the absolute value of described θ and symbol changes.

47, according to the described object lens of claim 42, it is characterized in that,

At described first lens face, described second lens face and the described middle section that at least one lens face had of described the 3rd lens face and the intersection of described neighboring area, be provided with optical jump.

48, according to the described object lens of claim 42, it is characterized in that,

The peripheral effective coverage of described first lens face possesses the diffraction structure of the light of the provision wavelengths made from the diffraction efficiency diffraction more than 80%.

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