CN100585705C - Object lens for optical pickup device, optical pickup device and optical information recording/reproducing device - Google Patents

Abstract

An objective lens used for an optical pickup device wherein the optical pickup device includes: light source; and a converging optical system including the objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium, and the optical pickup device is capable of recording and/or reproducing information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system, the objective lens being a plastic single lens and satisfying following formulas when NA is an image-side numerical aperture required for recording and/or reproducing information to the optical information recording medium and f (mm) is a focal length of the objective lens. Even in a plastic single lens having a high NA, thermal aberration does not increase excessively, and in a plastic single lens of a refraction type, thermal aberration within the temperature range of practical use in an optical pickup device is suppressed within an allowable range. NA >= 0.8 (1); 1.0 > f > 0.2 (2).

Description

The object lens of optical pick-up apparatus, optical pick-up apparatus and optical information recording/reproducing apparatus

The application is that application number is 03820542.4, the date of application is on August 28th, 2003, denomination of invention is divided an application for the application of " object lens of optical pick-up apparatus, optical pick-up apparatus and optical information recording/reproducing apparatus ".

Technical field

The present invention relates to optical pick-up apparatus, optical information recording/reproducing apparatus and their employed object lens, specifically, relate to optical pick-up apparatus, the optical information recording/reproducing apparatus that can carry out high-density optical information record or reproduce, and their employed object lens.

Background technology

Up to now, use the conduct of plastics simple lens at the optical pick-up apparatus or the employed object lens of optical information recording/reproducing apparatus that are used for writing down or reproducing the optical data recording medium such as CD, MD and DVD usually.

Specific density is lower owing to compare with glass lens, and plastic lens has an advantage: can reduce driving object lens so that the burden of the actuator that focuses on and follow the tracks of, and at full speed carry out the tracking of object lens in this respect.

In addition, by making desirable mould, can produce the plastic lens of producing by injection molding in a large number with higher accuracy.Therefore, though can play consistently the high-performance of lens,, also can plan to reduce cost.

By the way, in recent years, the research/development of new high density optical disc systems has been made significant headway, and in this system, blueness-violet laser diode light-source and the numerical aperture (NA) of using wavelength to be roughly 400nm are strengthened to roughly 0.85 object lens.As example, for NA be 0.85 and optical source wavelength be the execution information recording/regenerating of 405nm CD (below, such CD is called as " high density DVD "), with DVD diameter of a size be on the CD of 12cm, each face can write down 20 to 30GB information, and (NA is 0.6, optical source wavelength is 650nm, and memory capacity is 4.7GB).

Here, be used for the optical pick-up apparatus of this high density DVD, at NA is under the situation of plastic lens than higher object lens, follows the spherical aberration that variations in refractive index produced (below, such spherical aberration is called as " thermal aberration ") of temperature variation can become problem.Because therefore such problem, can take place than big two orders of magnitude of glass lens in plastic lens aspect change of refractive.At the NA that is used for high density DVD is that 0.85 object lens are under the situation of plastic lens, and it is very narrow that spendable temperature range becomes, because the bipyramid of thermal aberration and NA is proportional, correspondingly, this can become problem in actual applications.

In JP Tokukaihei-11-337818A, the technology of proofreading and correct the signal-lens such thermal aberration of plastics by the diffraction effect of using the ring-type phase structure form on its optical surface has been described.

In order to adopt this correction of typist's errors NA is the thermal aberration of 0.85 plastic lens, and the inclination angle (below, the inclination angle of such spherical aberration curve is called as " colored bulb surface aberration ") that must make the spherical aberration curve in wavelength change is for big.Therefore, can not use to have the laser diode that departs from standard wavelength's emission wavelength owing to foozle, thereby need to select laser diode, this makes that again cost uprises.

Shown specific example below with numerical value.The object lens that its lens data is displayed in Table 1 out are such plastics simple lenses: the incident beam diameter is 3mm, focal length is 2.5mm, NA is 0.6, design wavelength is 650nm, design temperature is 25 ℃, and proofreaies and correct thermal aberration by the diffraction effect that goes up the ring-type phase structure that forms at first surface (optical surface of light source example).On the other hand, the object lens that its lens data is displayed in Table 2 out are such plastics simple lenses: the incident beam diameter is 3mm, focal length is 1.76mm, NA is 0.85, design wavelength is 405nm, design temperature is 25 ℃, and proofreaies and correct thermal aberration by the diffraction effect of the ring-type phase structure that forms on first surface, and is the same with the mode of the object lens of table 1.Note that 10 power (for example, 2.5 * 10 ^-3) below will represent (for example, 2.5 * E-3) (comprising the lens data in the table) by using E.

Table 1

Surface No.	r(mm)	d(mm)	N650	vd	Remarks
						0		∞			Light source
1 2	1.6603 -4.5237	2.0500 1.0105	1.54090	56.7	Object lens
						3 4	∞ ∞	0.6000	1.57756	30.0	Protective seam

Asphericity coefficient

	First surface	Second surface
			K A4 A6 A8 A10	-6.8755E-01 3.0995E-03 2.6042E-04 4.5653E-05 -1.2223E-04	-7.9005E+00 4.3885E-02 -3.2001E-02 1.1954E-02 -1.9590E-03

The Difraction surface coefficient

Table 2

Surface No.	r(mm)	d(mm)	N405	vd	Remarks
						0		∞			Light source
1 2	1.2099 -1.5783	2.4500 0.3771	1.56013	56.7	Object lens
						3 4	∞ ∞	0.1000	1.61950	30.0	Protective seam

The non-spherical surface coefficient

	First surface	Second surface
			K A4 A6 A8 A10 A12 A14 A16 A18 A20	-7.1214E-01 5.4718E-03 5.1672E-03 1.5578E-03 1.0499E-03 -1.7777E-04 -1.4455E-05 1.7285E-04 -2.2142E-05 -1.2407E-05	-4.3724E+01 5.2395E-01 -1.1813E+00 1.2111E+00 -5.0156E-01 6.2662E-04

The Difraction surface coefficient

	First surface
		b2 b4 b6 b8 b10	-7.6944E-03 -8.9900E-03 1.1465E-03 2.2677E-04 -3.3067E-04

When optical axis direction is the x axle, be h perpendicular to the height of the direction of optical axis, when the radius-of-curvature of optical surface was r, the non-spherical surface in such object lens was represented by following formula 1.Note that k is the constant of the cone, A _2iIt is the non-spherical surface coefficient.

Formula 1

$X=\frac{{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="C2007101373950060H1.png"\; state="\{\{state\}\}">h</figure-callout>}}^2/\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="C2007101373950056H1.png"\; state="\{\{state\}\}">r</figure-callout>}}{1+\sqrt{1-(1+K){\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="C2007101373950060H1.png"\; state="\{\{state\}\}">h</figure-callout>}}^2/{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="C2007101373950060H1.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}}+\underset{i=2}{\mathrm{\&Sigma;}}{A}_{2i}{h}^{2i}$

In addition, in such object lens, express by the optical path difference of adding the transmitted wave front by diffraction structure to as the phase structure of the ring-type of the diffraction structure that on optical surface, forms.When the height perpendicular to the direction of optical axis is h, and b _2iWhen being Difraction surface coefficient (being also referred to as the optical path difference function coefficients), optical path difference is by the optical path difference function phi of following formula 2 definition _b(mm) express.

Formula 2

${\mathrm{\&Phi;}}_b=\underset{i=1}{\mathrm{\&Sigma;}}{b}_{2i}{h}^{2i}$

When based on the optical path difference function phi _bWhen value (mm) forms diffraction structure on the optical surface of object lens, each optical path difference function phi _b(mm) value is changed predetermined wavelength X _BN doubly when (n is a natural number), form anchor ring.In this manual, " diffraction structure is in wavelength X _BN is optimised with diffraction orders " the expression diffraction structure is in this way determined, and wavelength is called the optimization wavelength or produces wavelength.

Table 3 has shown the RMS value of thermal aberration when the environment temperature of two object lens improves 30 ℃, and when the RMS value of incident wavelength colored bulb surface aberration during than the long 5nm of design wavelength.

Table 3

	Thermal aberration (+30 ℃)	The colored bulb surface aberration (+5nm)
			NA0.6 NA0.85	0.010λrms 0.014λrms	0.003λrms 0.057λrms

As can be seen from Table 2, even be corrected in thermal aberration under the situation of 0.010 λ rms, NA is that 0.6 object lens are controlled at 0.003 λ rms with the colored bulb surface aberration, correspondingly, can use the laser diode of wavelength departure 5nm.Simultaneously, be 0.85 object lens as for NA, when thermal aberration is corrected to 0.014 λ rms, with NA be 0.6 object lens when similar, the colored bulb surface aberration becomes 0.057 λ rms, correspondingly, can not use the laser diode of wavelength departure 5nm.The laser diode that is used as light source in optical pick-up apparatus has in its emission wavelength approximately ± deviation of 5nm, correspondingly, need to select laser diode, and be that the production cost of optical pick-up apparatus will rise under the situation of 0.85 object lens using NA.

Note that in the object lens of table 1 and 2 making the change of refractive rate of following temperature to rise all is-9.0 * 10 ^-5, and make the wavelength change rate of following the incident light that temperature rises be respectively+0.2nm/ ℃ and+0.05nm/ ℃.

In addition, in the lens data of table 1, r (mm) represents radius-of-curvature, d (mm) presentation surface distance, the refractive index when N650 represents that wavelength is 650nm, vd represents the Abbe number of d in capable, in the lens data of table 2, r (mm) represents radius-of-curvature, d (mm) presentation surface distance, refractive index when N405 represents that wavelength is 405nm, vd represents the Abbe number of d in capable.

In addition, using blueness-violet laser diode generation wavelength to be approximately under the situation of short-wavelength light as light source (as the optical pick-up apparatus at high density DVD) of 400nm, the longitudianal aberration that produces in the object lens can become problem.In optical pick-up apparatus, the chromatic aberation of object lens is not considered as problem, because the laser that sends from laser diode has single wavelength (monotype).Yet in fact, owing to temperature variation, output change or the like, can produce the phenomenon that is called as " mode hopping ": centre wavelength can change several nanometers at once.Because mode hopping is the wavelength variations that causes at once, focalizer can not be followed the tracks of, and therefore, can produce a problem: when proofreading and correct the longitudianal aberration of object lens, interpolation corresponding to image form the position move defocus parts, and the focusing power of object lens reduces.

Because the 600nm that is dissipated in as the general lens of object lens is not so big to the scope interior (this is the wavelength coverage of infra-red laser diode and red laser diode) of 800nm, therefore, the decline of the focusing power of the object lens that cause owing to mode hopping can not become problem in CD and DVD.

Yet because (this is the wavelength coverage of blueness-velvet laser diode) becomes very big in the scope that is dissipated in 400nm of lens material, therefore, even the wavelength variations of several a little nanometers all can cause the image formation position of object lens to be departed from widely.Therefore, in high density DVD, when laser diode light source caused mode hopping, the focusing power of object lens reduced widely, and stable record and reproduction can not realize.

Summary of the invention

The present invention makes considering under the situation as described above, its purpose is to provide a kind of plastics simple lens, this plastics simple lens is suitable as the object lens of the optical pick-up apparatus that uses the object lens with high NA, have enough wide available temperature range, and the focusing power that causes owing to the mode hopping of light source descends slight.

In addition, the present invention also aims to provide a kind of plastics simple lens, this plastics simple lens is suitable as the object lens of the optical pick-up apparatus that uses the object lens with high NA, wherein, can be so that select laser diode light source unnecessary carrying out and can not cause the excessive increase of colored bulb surface aberration in the production stage of optical pick-up apparatus, even proofreading and correct thermal aberration so that enlarge under the situation of available temperature range.

In addition, the present invention also aims to provide a kind of the signal-lens optical pick-up apparatus of this plastics wherein has been installed, and the optical information recording/reproducing apparatus that this optical pick-up apparatus wherein has been installed.

Object lens according to the 1st described optical pick-up apparatus are the object lens that are used for optical pick-up apparatus,

Wherein, optical pick-up apparatus comprises: light source; And convergence optical system, this system comprises object lens, be used for the beam convergence that will send from light source information recording surface to optical data recording medium, and optical pick-up apparatus can write down and/or information reproduction by the beam convergence that will send from light source with this convergence optical system information recording surface to optical data recording medium, and

Wherein, these object lens are plastics simple lenses, and satisfy following formula:

NA≥0.8 (1)

1.0＞f＞0.2 (2)

Wherein, NA is the numerical aperture that information is write down and/or is rendered to the image-side of the required object lens of optical data recording medium, and f (mm) is the focal length of object lens.

The deviation (thermal aberration) of the spherical aberration of being brought owing to the signal-lens change of refractive of following temperature to rise to produce of plastics and the bipyramid of focal length and NA increase pro rata.Correspondingly, even, also can relatively suppress thermal aberration by correspondingly dwindling focal length increasing NA so that increase under the situation of density of optical data recording medium.Therefore, for according to the 1st object lens, by the upper limit of focal length is set according to formula (2), even have under the signal-lens situation of plastics of the high NA that satisfies formula (1), also can stop thermal aberration exceedingly to increase.In addition, for the plastics simple lens of refractive type, can not make the complete vanishing of thermal aberration.Yet, can be no more than the upper limit of formula (2) by making focal length, the thermal aberration in the temperature range of the practical application of optical pick-up apparatus is suppressed in the permissible range.

On the other hand, although from the viewpoint of the generation that suppresses thermal aberration, it is favourable dwindling focal length,, from the viewpoint of operating distance and picture altitude feature, it is disadvantageous excessively dwindling focal length.For the design of object lens with high NA, with fixed focal length for preventing that clashing with optical data recording medium is unusual important problem.When focal length excessively dwindled, operating distance was also lost this amount, and this is disadvantageous.When attempting to obtain the picture altitude identical with the object lens with long relatively focal length, owing to increase to the incident angle of the object lens with short relatively focal length, astigmatic image error and coma aberration also can reduce.Correspondingly, also from the viewpoint of picture altitude feature, the focal length that dwindles object lens is disadvantageous.Therefore, by the upper limit of focal length is set according to formula (2), obtained necessary and enough operating distance and picture altitude features according to the 1st described object lens.

According to the object lens of the 2nd described optical pick-up apparatus, wherein, in according to the 1st described invention, when having wavelength X ₀(nm) (this is the first environment temperature T to the light of (this is its design wavelength) in environment temperature ₀=25 ℃) under when inciding object lens, W (λ ₀, T ₀) be the RMS value of the residual aberration of object lens, when having wavelength X ₀(nm) (this is the second environment temperature T to the light of (this is its design wavelength) in environment temperature ₁=55 ℃) under when inciding object lens, W (λ ₀, T ₁) be the RMS value of the residual aberration of object lens, then by the Δ W of following formula definition:

ΔW＝|W(λ ₀，T ₁)-W(λ ₀，T ₀)| (3)

Satisfy following formula:

ΔW＜0.035λrms (4)

For the plastics simple lens can be used, provide such temperature characterisitic under the preferable case in the temperature range of the practical application of optical pick-up apparatus: make focal length be no more than the upper limit of formula (2), therefore satisfy formula (4).Therefore, by in the temperature range of the practical application of optical pick-up apparatus, using the plastics simple lens, can carry out the good information recoding/reproduction for optical data recording medium.

According to the object lens of the 3rd described optical pick-up apparatus, wherein, in object lens according to the 1st or 2 described optical pick-up apparatus, the design wavelength lambda of Liar ₀Be no more than 500nm, under following situation, when wavelength is λ ₀(nm) (this is the first environment temperature T to light in environment temperature ₀=25 ℃) under when inciding object lens, fB (λ ₀, T ₀) be the back focal length of object lens, when wavelength is λ ₁(nm) (this compares wavelength X ₀Long 5nm) (this is the first environment temperature T to light in environment temperature ₀=25 ℃) under when inciding object lens, fB (λ ₁, T ₀) be the back focal length of object lens, then by the Δ fB of following formula definition

ΔfB＝|fB(λ ₁，T ₀)-fB(λ ₀，T ₀)| (5)

Satisfy following formula:

ΔfB＜0.001mm (6)

Because longitudianal aberration and focal length that the mode hopping of laser diode causes increase pro rata.Correspondingly, for example, even using under the blueness-situation of violet laser diode, also can relatively suppress longitudianal aberration when dwindling in that focal length is corresponding as light source.As for the simple lens of refractive type, can not make chromatic aberation be entirely zero.Yet, when in object lens, making the deviation of when incident wavelength is increased 5nm back focal length less than 0.001mm (formula (6)), as according to the 3rd described object lens, wherein, focal length is provided with like this, so that satisfy formula (2), and uses blueness-violet laser diode as light source, for because the deviation of the wavelength that the mode hopping of blueness-violet laser diode causes can make the deviation that comprises the wavefront aberration that defocuses component be suppressed to less than 0.035 λ rms.Therefore, even producing when reproducing condition switches to record condition under the situation of mode hopping, focusing power can significantly not reduce yet.

Object lens according to the 4th described optical pick-up apparatus, wherein, in according to any one the described invention in the 1-3 item, object lens are object lens of finite conjugate type, be used for focusing on the information recording surface of optical data recording medium, and satisfy following formula from the divergent beams that light source sends:

0.8＞f＞0.2(6A)

According to the 4th described object lens, in the preferred case as the object lens that require the optical pick-up apparatus of miniaturization, for example, can be as the object lens that are installed in the optical pick-up apparatus in the portable optic disk player.To form magnification be m and brightness and the object lens of the much the same finite conjugate type of object lens of unlimited type in order to obtain image, must design brightness and be the lens of (1-m) times of image-side numerical aperture of the object lens of unlimited type.At object lens are finite conjugate types, these object lens will focus on from the divergent beams that light source sends under the situation of information recording surface of optical data recording medium, the symbol of m is for negative, and the basic numerical aperture of image-side becomes greater than the numerical aperture of the image-side of the object lens of unlimited type.Correspondingly, when object lens that use the finite conjugate type during, make the object lens of thermal aberration greater than unlimited type as the plastics simple lens.In according to the 4th described object lens, the upper limit by making focal length is little more than formula (2), and as formula (6A), be provided with, even under the signal-lens situation of plastics, also thermal aberration can be suppressed in the permissible range of practical application with finite conjugate type that high NA and NA satisfy formula (1).At the object lens of the finite conjugate type that is used for the focus divergent light beam, to compare with the object lens of unlimited type with the same focal length, it is bigger that operating distance becomes.Correspondingly, as according to the 4th described object lens, also be under the upper limit that the makes focal length situation little more than formula (2), be disadvantageous from the viewpoint that obtains operating distance.

According to the object lens of the 5th described optical pick-up apparatus, wherein, in according to the 4th described invention, when m was the image formation magnification of object lens, m satisfied following formula:

0.2＞|m|＞0.02 (6B)

When image form magnification m greater than formula as described above (6B) following in limited time, even the object lens with short focal length that satisfy formula as described above (6A) also can obtain enough operating distances.On the other hand, prescribe a time limit less than going up of formula (6B), also thermal aberration can be suppressed in the permissible range of practical application, because the basic numerical aperture of image-side can exceedingly not increase when image forms magnification m.

According to the 6th the described object lens that are used for optical pick-up apparatus are the object lens that are used for optical pick-up apparatus, and wherein, optical pick-up apparatus comprises: light source; And convergence optical system, this system comprises and is used for the beam convergence that will send from the light source object lens to the information recording surface of optical data recording medium, and this optical pick-up apparatus can write down and/or information reproduction by the beam convergence that will send from light source with this convergence optical system information recording surface to optical data recording medium

Wherein, object lens are the plastics simple lenses that comprise the ring-type phase structure at least one optical surface, and this ring-type phase structure comprises a plurality of anchor rings, and forms so that adjacent anchor ring produces predetermined optical path difference to incident light, and satisfies following formula:

NA≥0.8 (7)

1.3＞f＞0.2 (8)

Wherein, NA is the numerical aperture of the image-side of object lens, and this carries out information record for optical data recording medium and/or reproduces requiredly, and f (mm) is the focal length of object lens.

Numerical aperture NA satisfies in the plastic objective lens of formula (7) therein, under the situation of proofreading and correct by the effect of the ring-type phase structure that forming on the optical surface by the spherical aberration of following temperature to rise to cause that variations in refractive index produced (thermal aberration), the inclination angle of the spherical aberration curve in the wavelength change (colored bulb surface aberration) exceedingly becomes big.Correspondingly, can not use to have the laser diode that departs from standard wavelength's emission wavelength owing to foozle, thereby need to select laser diode.

As mentioned above, since the deviation of the spherical aberration that the change of refractive of plastic objective lens is brought and the bipyramid of focal length and NA increase pro rata.Correspondingly, even increasing NA so that increase under the situation of density of optical data recording medium, also can focal length relatively suppresses because the spherical aberration that variations in refractive index produced of object lens by correspondingly dwindling.

For according to the 6th described object lens, can stop the colored bulb surface aberration after proofreading and correct thermal aberration, exceedingly to increase, because by the upper limit of focal length is set according to formula (8), make because the correcting value of the thermal aberration that the effect of ring-type phase structure is brought is suppressed to low.As a result,, can reduce production costs, because in production stage, needn't select laser diode for the optical pick-up apparatus that object lens of the present invention wherein have been installed.Simultaneously, although from the viewpoint of the generation that suppresses thermal aberration, it is favourable dwindling focal length,, from the viewpoint of operating distance and picture altitude feature, the excessive focal length that dwindles is disadvantageous.Therefore, object lens of the present invention have obtained necessary and enough operating distance and picture altitude features by the upper limit of focal length is set according to formula (8).

In this manual, on narrow sense, object lens represent to have the lens of focusing power, it is positioned at the position nearest with optical data recording medium, and it is relative with the optical data recording medium face under optical recording media is packed the state of optical pick-up apparatus into, on broad sense, object lens are the lens that can be driven by actuator on optical axis direction at least.Correspondingly, in this manual, the numerical aperture of the object lens on the optical data recording medium side (image-side) represents to be positioned at the numerical aperture with the lens surface of the nearest object lens of optical data recording medium.Still in this manual, (predetermined) numerical aperture that needs is represented the numerical aperture by the standard adjustment of corresponding optical data recording medium, or has a numerical aperture of the object lens of diffraction-limited ability, can obtain record or the required spot definition of information reproduction according to the wavelength of the employed light source of corresponding optical data recording medium.

Still in this manual, recording of information is illustrated in recorded information on the information recording surface that is similar to optical data recording medium as described above.In this manual, the reproduction of information represents to be reproduced in the information that writes down on the information recording surface that is similar to optical data recording medium as described above.Object lens of the present invention can be used for only writing down or only reproducing, and also can be used for not only writing down but also reproduce.Can be used for writing down and reproducing for another optical data recording medium for a certain optical data recording medium, perhaps, can be used for writing down or reproducing, and write down and reproduce for another optical data recording medium for a certain optical data recording medium.The term here " reproduction " includes only the information of reading.

For object lens according to the 7th described optical pick-up apparatus, in according to the 6th described invention, the ring-type phase structure is the diffraction structure with function of the predetermined incident light of diffraction, and object lens have constituted the convergent wave front, this wave front is owing to the effect that obtains by combination diffraction effect and refraction effect focuses on the information recording surface, and carrying out operation as described above effectively, is preferred therefore.

Object lens according to the 8th described optical pick-up apparatus have such spherical aberration feature, and when the incident light wavelength became according to the long wavelength in the 7th the described invention, spherical aberration changed in the direction of undercorrection.

Because the signal-lens refractive index of plastics reduces owing to temperature rises usually, therefore, spherical aberration changes in the direction of exaggerated correction.Simultaneously, the emission wavelength of laser diode has the tendency that changes along with the temperature rising usually in augment direction.Correspondingly, by providing because the object lens that the effect of diffraction structure has spherical aberration feature as described above, changed by the spherical aberration of exaggerated correction by the variations in refractive index of following temperature to rise, the variation that can be corrected not enough spherical aberration by means of the variation by the emission wavelength of the laser diode that causes because temperature rises comes in addition balance.Even for high NA plastics simple lens, because object lens of the present invention have the focal length that satisfies formula (8), the correcting value of the thermal aberration that causes because of the effect of diffraction structure is little, and the colored bulb surface aberration after proofreading and correct thermal aberration can not become excessive.

In this manual, the optical surface (Difraction surface) that has formed diffraction structure in the above is such surface, by be optical element the surface (for example, the surface of lens) provides burr and obtain the effect of diffraction incident beam, and, be the zone that is used to produce diffraction being useful on the zone that produces diffraction on the same optical surface and being not used under the situation in the zone that produces diffraction.Diffraction structure or diffraction pattern are the zones that is used to produce diffraction.As the shape of burr, for example, on optical element, form shape as the substantially concentric ring surface that with the optical axis is the center, when seeing the part on the plane that comprises optical axis, for corresponding ring surface, known have sawtooth or a stepped shape, also comprised these shapes simultaneously.

In addition, produced unnumbered diffraction light from the optical surface (Difraction surface) that forms diffraction structure thereon: the 0th rank diffraction light, ± 1 rank diffraction light, ± 2 rank diffraction lights ....For example, under the situation of Difraction surface with burr (its meridian partly is aforesaid serrate), the shape of burr can be arranged to make the diffraction efficiency on specific rank to be higher than the diffraction efficiency on other rank, and in some cases, make the diffraction efficiency on specific rank (for example ,+1 diffraction light on rank) be almost 100%.In the present invention, " diffraction structure is in wavelength X _BN is optimised with diffraction orders " expression is provided with the shape of diffraction structure (burr), and making wavelength with box lunch is λ _BLight when being incident light, the diffraction efficiency of the diffraction light of diffraction orders n becomes 100% theoretically.

According to the object lens of the 9th described optical pick-up apparatus, wherein, in according to the 7th or 8 described invention, when the optical path difference of adding the wave front by diffraction structure to by optical path difference function phi by following formula definition _bWhen representing:

Φ _b＝b ₂·h ²+b ₄·h ⁴+b ₆·h ⁶+...

(wherein, b ₂, b ₄, b ₆... be respectively the 2nd rank, the 4th rank, the 6th rank ... the optical path difference function coefficients), satisfy following formula:

-70＜(b ₄·h _MAX ⁴)/(f·λ ₀·10 ^-6·(NA·(1-m)) ⁴)＜-20 (8A)

Wherein, λ ₀(nm) be the design wavelength of object lens, h _MAXBe the effective diameter maximum height (mm) that has formed the optical surface of diffraction structure in the above, m is that the image of object lens forms magnification.

Design like this under the object lens preferable case of optical pick-up apparatus of the present invention: so that quadravalence optical path difference function coefficients b ₄, formed the effective diameter maximum height h of the optical surface of diffraction structure in the above _MAX, image forms the condition that magnification m, focal distance f and image-side numerical aperture NA satisfy formula as described above (8A).This condition is the EQUILIBRIUM CONDITION that is used for improving the generation of the correction of thermal aberration of the plastic lens that has wherein formed diffraction structure and colored bulb surface aberration.Under the situation of the lower limit of the formula on surpass, the generation of colored bulb surface aberration can exceedingly not increase, because thermal aberration can be by exaggerated correction, correspondingly, even can use and have the laser diode that departs from standard wavelength's emission wavelength owing to foozle, and can alleviate the alternative condition of laser diode, thereby reduce cost.Simultaneously, under the situation of the upper limit of the formula on be lower than, wide temperature range can be provided, in this scope, can use plastic lens, because can use by the spherical aberration that wavelength variations produced of laser diode balance in addition by the spherical aberration that variations in refractive index produces of plastic lens with high NA with high NA.

For object lens according to the 10th described optical pick-up apparatus, in according to the 6th described invention, the ring-type phase structure is by constituting adjacent anchor ring so that be shifted each other at optical axis direction, produce predetermined optical path difference for incident light, and object lens have constituted the convergent wave front, this wave front is owing to refraction effect focuses on the information recording surface, and carries out operation as described above effectively, so this is preferred.

Object lens according to the 11st described optical pick-up apparatus, in according to the 6th described invention, at least comprise an anchor ring, this anchor ring forms like this, so that compare with near the anchor ring more close optical axis one side, it moves to the inside, and comprise an anchor ring at least, this anchor ring forms like this, so that with more close optical axis one side near anchor ring compare, it moves laterally, and, be formed with more close optical axis one side near anchor ring compare the anchor ring that moves to the inside, than be formed with more close optical axis one side near anchor ring compare laterally the more close optical axis of anchor ring that moves, and thermal aberration can be proofreaied and correct well by in this way disposing the ring-type phase structure, and therefore, it is preferred.

According to the object lens of the 12nd described optical pick-up apparatus, wherein, in according to the 10th or 11 described invention, the sum of anchor ring from 3 to 20.

According to the object lens of the 13rd described optical pick-up apparatus, wherein, in according to any one the described invention in the 10-12 item, work as Δ _j(μ m) formed the boundary of anchor ring of the mutual vicinity in the ring-type phase structure that forms in the zone of height of 75% height to 100% of effective diameter maximum height of optical surface of ring-type phase structure in the above along the step-size amounts of any step-length in the step-length of optical axis direction, and n is a design wavelength lambda ₀During the refractive index of the object lens in the time of (nm), by the m of following formula representative _j

m _j＝INT(X) (8B)

(X=Δ wherein _j(n-1)/(λ ₀10 ^-3) and INT (X) be the integer that rounds up and obtained by to X) be to be not less than 2 integer.

In the 10th and 11 described object lens, the sum of anchor ring from 3 to 20 in addition, is worked as Δ _j(μ m) formed the step-size amounts of the anchor ring boundary of the mutual vicinity in the ring-type phase structure that forms in the zone of height of 75% height to 100% of effective diameter maximum height of optical surface of ring-type phase structure along any step-length in the step-length of optical axis direction in the above, and n is a design wavelength lambda ₀During the refractive index of the object lens in the time of (nm), by the m of (8B) as described above representative _jBe to be not less than 2 integer, the mold process of mold pressing object lens becomes and is easy to, for the time that mold process spent can shorten, because can obtain the big width of anchor ring in the direction perpendicular to optical axis.

Here, be that first surface (optical surface of light source side) has formed under the situation of ring-type phase structure, form " comparing with near the anchor ring more close optical axis one side; move to the inside " expression and form " comparing with near the anchor ring more close optical axis one side; the direction along second surface (optical surface of optical data recording medium side) moves ", and, form " comparing with near the anchor ring more close optical axis one side; move laterally " expression and form " compare with near the anchor ring more close optical axis one side, move in the opposite direction " along side with second surface (optical surface of optical data recording medium side).In addition, be that second surface (optical surface of optical data recording medium side) has formed under the situation of ring-type phase structure, form " comparing with near the anchor ring more close optical axis one side; move to the inside " expression and form " comparing with near the anchor ring more close optical axis one side; the direction along first surface (optical surface of light source side) moves ", and, form " comparing with near the anchor ring more close optical axis one side; move laterally " expression and form " compare with near the anchor ring more close optical axis one side, move in the opposite direction " along side with first surface (optical surface of light source side).

According to the object lens of the 14th described optical pick-up apparatus, wherein, in the described invention of any one in the 6-13 item, when having wavelength X ₀(nm) (this is the first environment temperature T to the light of (this is its design wavelength) in environment temperature ₀=25 ℃) under W (λ when inciding object lens ₀, T ₀) be the RMS value of the residual aberration of object lens, when having wavelength X ₁(nm) (this compares wavelength X ₀Long 5nm) (this is the first environment temperature T to light in environment temperature ₀=25 ℃) under W (λ when inciding object lens ₁, T ₀) be the RMS value of the residual aberration of object lens, and when having wavelength X ₂(nm) (this is the second environment temperature T to light in environment temperature ₁=55 ℃) under W (λ when inciding object lens ₂, T ₁) be the RMS value of the residual aberration of object lens, then by the Δ W1 and the Δ W2 of following formula definition:

ΔW1＝|W(λ ₂，T ₁)-W(λ ₀，T ₀)| (9)

ΔW2＝|W(λ ₁，T ₀)-W(λ ₀，T ₀)| (10)

Satisfy following formula:

ΔW1＜0.035λrms (11)

ΔW2＜0.035λrms (12)

Wherein

Work as λ ₀During＜600nm, λ ₂=λ ₀+ 1.5 (nm) and

Work as λ ₀During 〉=600nm, λ ₂=λ ₀+ 6 (nm).

In having the plastic lens of high NA, when proofreading and correct thermal aberration fully by the effect of the ring-type phase structure that on optical surface, forms, even satisfy at focal length that the colored bulb surface aberration also can excessively increase under the situation of formula (8), and can not use laser diode with the emission wavelength that departs from the standard wavelength, correspondingly, in the design of lens, must be with the generation of the correction of thermal aberration and colored bulb surface aberration balance in addition.Here, formula (9) is the formula corresponding to the thermal aberration under 30 ℃ the situation of rising in temperature, and formula (10) is the formula corresponding to the colored bulb surface aberration under the situation of the wavelength variations 5nm of incident light.For object lens of the present invention, under the preferable case, the formula (13) that total aberration of thermal aberration, colored bulb surface aberration and colored bulb surface aberration and thermal aberration satisfies formula (11) and (12) and describes after a while.

As according to the 14th described object lens, λ ₀＜600nm, the variation (+0.05nm/ ℃) of the emission wavelength that the condition of λ 2=λ 0+1.5 (nm) causes corresponding to rising owing to the temperature of blueness-violet laser diode, and λ ₀〉=600nm, λ ₂=λ ₀The variation (+0.2nm/ ℃) of the emission wavelength that the condition of+6 (nm) causes corresponding to rising owing to the temperature of red laser diode.

In this manual, the design wavelength of object lens is the wavelength that make the residual aberration minimum of object lens at the light that makes various wavelength under the situation that incides object lens under the same terms (image forms magnification, temperature, incident beam diameter or the like).In addition, in this manual, the design temperature of object lens is to measure the temperature that the same terms (image forms magnification, wavelength, incident beam diameter or the like) makes the residual aberration minimum of object lens down under the situation of the residual aberration of the object lens in the various environment temperatures.

According to the object lens of the 15th described optical pick-up apparatus, wherein, satisfy following formula according to the object lens in the 14th the described invention, therefore, it is preferred.

$\sqrt{({\left(\mathrm{\&Delta;W}1\right)}^2+{\left(\mathrm{\&Delta;W}2\right)}^2}<0.05\mathrm{\&lambda;rms}---\left(13\right)$

Object lens according to the 16th described optical pick-up apparatus, wherein, in the described invention of any one in the 6-15 item, object lens are object lens of finite conjugate type, be used for and will focus on information recording surface, and satisfy following formula from the divergent beams that light source sends:

1.1＞f＞0.2 (13A)

Operation of the present invention is identical with the operation and the effect of the 4th described invention with effect.

According to the object lens of the 17th described optical pick-up apparatus, wherein, in the 16th described invention, when m was the image formation magnification of object lens, object lens satisfied following formula:

0.2＞|m|＞0.02 (13B)

Operation of the present invention is identical with the operation and the effect of the 5th described invention with effect.

According to the object lens of the 18th described optical pick-up apparatus, wherein, in the described invention of any one in the 1-17 item, object lens satisfy following formula:

0.8＜d/f＜1.8 (14)

Wherein, d (mm) is the lens thickness along the optical axis of object lens, and f (mm) is a focal length.

Formula (14) is at the high NA object lens with minor diameter (wherein, focal length satisfies formula (2), (6A), (8) and (13A)) in obtain the condition of preferable image altitude feature, enough production tolerance and enough operating distance, and an advantage is arranged: when the value of d/f is prescribed a time limit greater than the following of formula (14), the 3rd rank astigmatic difference component can exceedingly not increase by wavefront aberration evaluate image altitude feature the time, and the high-order coma aberration component that is equal to or greater than the 5th rank can exceedingly not increase.Simultaneously, an advantage is arranged: the 3rd rank spherical aberration component, the 5th rank astigmatic difference component, the 3rd rank coma aberration component and astigmatic aberration can exceedingly not increase by wavefront aberration evaluate image altitude feature the time.In addition, because the tooth radius of the optical surface of light source side can exceedingly not dwindle, therefore, can suppress the coma aberration that the optical axis deviation owing to optical surface produces and obtain enough production tolerances.When the value of d/f is prescribed a time limit greater than the following of formula (14), can suppress the birefringence that produces owing to mold pressing, because obtained enough edge thickness, and uneven thickness can exceedingly not diminish than, simultaneously, when the value of d/f greater than the going up in limited time of formula (14), lens are lightened and drive by less actuator, and can obtain enough operating distances, because lens thickness can exceedingly not increase.

For object lens according to the 19th described optical pick-up apparatus, in the described invention of any one in the 1-18 item, the design wavelength lambda of object lens ₀(nm) satisfy following formula, and it can be used to be equipped with the optical pick-up apparatus of the short wavelength light source such as blueness-violet laser diode.

500≥λ ₀≥350 (15)

According to the object lens of the 20th described optical pick-up apparatus, wherein, in the described invention of any one in the 1-19 item, object lens satisfy following formula:

$0.40\&le;(X1-X2)\&CenterDot;(N-1)/(\mathrm{NA}\&CenterDot;f\&CenterDot;\sqrt{(1+|m\left|\right)})\&le;0.63---\left(16\right)$

Wherein

X1: perpendicular to optical axis and and the outermost part of tangent plane, the top of the optical surface of light source side and effective diameter in the optical surface (inciding the position of NA on the surface of light source side wherein at the edge light beam) of light source side between the distance (mm) of optical axis direction, wherein, with reference to positive tangent plane along X1 under the situation of the orientation measurement X1 of optical data recording medium for just, along X1 under the situation of the orientation measurement X1 of light source for negative

X2: perpendicular to optical axis and with the outermost part of tangent plane, the top of the optical surface of optical data recording medium side and effective diameter in the optical surface of optical data recording medium side, the distance of the optical axis direction between (inciding the position of NA on the surface of optical data recording medium side wherein at the edge light beam), (mm), wherein, with reference to positive tangent plane along X2 under the situation of the orientation measurement X2 of optical data recording medium for just, along X2 under the situation of the orientation measurement X2 of light source for negative

N: in design wavelength lambda ₀The time object lens refractive index,

F: the focal length of object lens (mm), and

M: the image of object lens forms magnification.

The 20th the sagging relevant condition formula of having regulated with the optical surface of the optical surface of light source side and optical data recording medium side is so that correcting spherical aberration preferably.When the X1 that defines by as described above mode be on the occasion of and its absolute value hour, maybe when the X2 that define by as described above mode be negative value and its absolute value hour, the effect of the spherical aberration of exaggerated correction edge light beam uprises, and, when the X1 that defines by as described above mode be on the occasion of and its absolute value when big, maybe when the X2 that defines by as described above mode be that negative value and its absolute value are when big, effect to the spherical aberration correction deficiency of edge light beam uprises, therefore, (X1-X2) must be limited in a certain scope, so that correcting spherical aberration.From above as can be seen, satisfy formula (16) under the preferable case, when greater than down in limited time, the not overcorrect exceedingly of edge light beam, when less than last in limited time, the edge light beam is undercorrection exceedingly not.Specifically, (be λ wherein, at the object lens that adopt unlimited type at design wavelength ₀The time image to form magnification be zero) situation under, preferably satisfy following formula:

$0.40\&le;(X1-X2)\&CenterDot;(N-1)/(\mathrm{NA}\&CenterDot;f\&CenterDot;\sqrt{(1+|m\left|\right)})\&le;0.55---\left(16^{\&prime;}\right)$

In addition, focus under the situation of the object lens on the information recording surface, preferably satisfy following formula at the divergent beams that are used for sending that adopt the finite conjugate type from light source:

$0.48\&le;(X1-X2)\&CenterDot;(N-1)/(\mathrm{NA}\&CenterDot;f\&CenterDot;\sqrt{(1+|m\left|\right)})\&le;0.63---\left(16^{\&prime;\&prime;}\right)$

Comprise according to the 21st described optical pick-up apparatus: light source; And convergence optical system, this system comprises object lens, be used for the beam convergence that will send from light source information recording surface to optical data recording medium, and this optical pick-up apparatus can write down and/or information reproduction by the beam convergence that will send from light source with the convergence optical system information recording surface to optical data recording medium

Wherein, object lens are plastics simple lenses, and satisfy following formula:

NA≥0.8 (1)

1.0＞f＞0.2 (2)

Wherein, NA is the image-side numerical aperture that information is write down and/or is rendered to the required object lens of optical data recording medium, and f (mm) is the focal length of object lens.

Operation of the present invention is identical with the operation and the effect of the 1st described invention with effect.

According to the 22nd described optical pick-up apparatus, wherein, in according to the 21st described invention, when having wavelength X ₀(nm) (this is the first environment temperature T to the light of (this is its design wavelength) in environment temperature ₀=25 ℃) under W (λ when inciding object lens ₀, T ₀) be the RMS value of the residual aberration of object lens, and when having wavelength X ₀(nm) (this is the second environment temperature T to the light of (this is its design wavelength) in environment temperature ₁=55 ℃) under W (λ when inciding object lens ₀, T ₁) be the RMS value of the residual aberration of object lens, then by the Δ W of following formula definition:

ΔW＝|W(λ ₀，T ₁)-W(λ ₀，T ₀)| (3)

Satisfy following formula:

ΔW＜0.035λrms (4)

Operation of the present invention is identical with the operation and the effect of the 2nd described invention with effect.

According to the 23rd described optical pick-up apparatus, wherein, in according to the 21st or 22 described invention, the design wavelength lambda of Liar ₀Be no more than 500nm, under following situation, when wavelength is λ ₀(nm) (this is the first environment temperature T to light in environment temperature ₀=25 ℃) under fB (λ when inciding object lens ₀, T ₀) be the back focal length of object lens, and when wavelength be λ ₁(nm) (this compares wavelength X ₀Long 5nm) (this is the first environment temperature T to light in environment temperature ₀=25 ℃) under fB (λ when inciding object lens ₁, T ₀) be the back focal length of object lens, by the Δ fB of following formula definition

ΔfB＝|fB(λ ₁，T ₀)-fB(λ ₀，T ₀)| (5)

Satisfy following formula:

ΔfB＜0.001mm (6)

Operation of the present invention is identical with the operation and the effect of the 3rd described invention with effect.

According to the 24th described optical pick-up apparatus, wherein, in the described invention of any one in the 21-23 item, object lens are object lens of finite conjugate type, be used for focusing on the information recording surface of optical data recording medium, and satisfy following formula from the divergent beams that light source sends:

0.8＞f＞0.2 (6A)

Operation of the present invention is identical with the operation and the effect of the 4th described invention with effect.

According to the 25th described optical pick-up apparatus, wherein, in according to the 24th described invention, when m was the image formation magnification of object lens, m satisfied following formula:

0.2＞|m|＞0.02 (6B)

Operation of the present invention is identical with the operation and the effect of the 5th described invention with effect.

According to the 26th described optical pick-up apparatus, wherein, in according to the 24th or 25 described invention, object lens and light source are combined by actuator, are driven at least, so that follow the tracks of.

To its incident in the object lens of finite conjugate type of divergent beams, be a problem by the coma aberration that tracking error produced.Reason is, when object lens since tracking error from the launching site of light source when eccentric, send a little become object lens from the axle object point.Although the off-centre of the object lens that cause owing to tracking error in the ordinary optical pick device is approximately 0.2 to 0.3mm, but, object lens of the present invention are the short focus lens that have that satisfy formula as described above (6A), correspondingly, can significantly produce coma aberration and astigmatic difference, and when object lens because tracking error and eccentric about 0.2 to 0.3mm the time can not be carried out good recoding/reproduction to optical data recording medium.Therefore, be configured to make object lens and light source to be combined, be driven at least, so that follow the tracks of by actuator according to the 22nd described optical pick-up apparatus.Therefore, can solve because the coma aberration that tracking error produced and the problem of astigmatic difference.

Comprise according to the 27th described optical pick-up apparatus: light source; And convergence optical system, this system comprises object lens, be used for the beam convergence that will send from light source information recording surface to optical data recording medium, and this optical pick-up apparatus can write down and/or information reproduction by the beam convergence that will send from light source with the convergence optical system information recording surface to optical data recording medium

Wherein, object lens are the plastics simple lenses that comprise the ring-type phase structure at least on an optical surface, and the ring-type phase structure comprises a plurality of anchor rings, and form and make adjacent anchor ring produce predetermined optical path difference for incident light, and satisfy following formula:

NA≥0.8 (7)

1.3＞f＞0.2 (8)

Wherein, NA is the image-side numerical aperture of object lens, and this carries out information record for optical data recording medium and/or reproduces requiredly, and f (mm) is the focal length of object lens.

Operation of the present invention is identical with the 6th operation and effect with effect.

According to the 28th described optical pick-up apparatus, wherein, in according to the 27th described invention, the ring-type phase structure is the diffraction structure with function of the predetermined incident light of diffraction, and object lens have constituted the convergent wave front, and this wave front is owing to be focused on information recording surface by the combination effect that diffraction effect and refraction effect obtained.Operation of the present invention is identical with the 7th operation and effect with effect.

According to the 29th described optical pick-up apparatus, wherein, in according to the 28th described invention, object lens have such spherical aberration feature: when the incident light wavelength became long wavelength, spherical aberration changed in the direction of undercorrection.Operation of the present invention is identical with the 8th operation and effect with effect.

According to the 30th described optical pick-up apparatus, wherein, in according to the 28th or 29 described invention, when the optical path difference of adding the wave front by diffraction structure to by optical path difference function phi by following formula definition _bWhen representing:

Φ _b＝b ₂·h ²+b ₄·h ⁴+b ₆·h ⁶+...

Wherein, b ₂, b ₄, b ₆... be respectively the 2nd rank, the 4th rank, the 6th rank ... the optical path difference function coefficients), satisfy following formula:

-70＜(b ₄·h _MAX ⁴)/(f·λ ₀·10 ^-6·(NA·(1-m)) ⁴)＜-20 (8A)

Wherein, λ ₀(nm) be the design wavelength of object lens, h _MAXBe the effective diameter maximum height (mm) that has formed the optical surface of diffraction structure in the above, m is that the image of object lens forms magnification.Operation of the present invention is identical with the 9th operation and effect with effect.

According to the 31st described optical pick-up apparatus, wherein, in according to the 27th described invention, the ring-type phase structure is by constituting adjacent anchor ring so that be shifted each other at optical axis direction, thereby produce predetermined optical path difference for incident light, object lens have constituted the convergent wave front, and this wave front is owing to refraction effect focuses on the information recording surface.Operation of the present invention is identical with the 10th operation and effect with effect.

According to the 32nd described optical pick-up apparatus, wherein, in according to the 31st described invention, when the anchor ring that comprises optical axis is called the center anchor ring, the toroid of anchor ring outside, contiguous center becomes along optical axis direction and moves, so that have the optical path length shorter than center anchor ring, toroid in the maximum effective diameter position becomes along optical axis direction and moves, so that have the neighbour nearly longer optical path length of its inboard anchor ring, anchor ring in 75% position of maximum effective diameter is formed mobile, so that have the shorter optical path length of anchor ring in neighbour nearly its inboard anchor ring and contiguous its outside.Operation of the present invention is identical with the 11st operation and effect with effect.

According to the 33rd described optical pick-up apparatus, wherein, in according to the 21st or 22 described invention, the sum of anchor ring from 3 to 20.Operation of the present invention is identical with the 12nd operation and effect with effect.

According to the 34th described optical pick-up apparatus, wherein, in according to any one the described invention in the 21-23 item, work as Δ _j(μ m) formed in the above that the boundary of contiguous anchor ring is along the step-size amounts of any step-length in the step-length of optical axis direction mutually in the ring-type phase structure that forms in the zone of height of 75% height to 100% of effective diameter maximum height of optical surface of ring-type phase structure, and n is a design wavelength lambda ₀During the refractive index of the object lens in the time of (nm), by the m of following formula representative _j

m _j＝INT(X) (8B)

(X=Δ j (n-1)/(λ wherein ₀10 ^-3) and INT (X) be the integer that rounds up and obtained by to X) be to be not less than 2 integer.Operation of the present invention is identical with the 13rd operation and effect with effect.

According to the 35th described optical pick-up apparatus, wherein, in according to any one the described invention in the 27-37 item, when having wavelength X ₀(nm) (this is the first environment temperature T to the light of (this is its design wavelength) in environment temperature ₀=25 ℃) under W (λ when inciding object lens ₀, T ₀) be the RMS value of the residual aberration of object lens, when having wavelength X ₁(nm) (this compares wavelength X ₀Long 5nm) (this is the first environment temperature T to light in environment temperature ₀=25 ℃) under W (λ when inciding object lens ₁, T ₀) be the RMS value of the residual aberration of object lens, and when having wavelength X ₂(nm) (this is the second environment temperature T to light in environment temperature ₁=55 ℃) under W (λ when inciding object lens ₂, T ₁) be the RMS value of the residual aberration of object lens, by the Δ W1 and the Δ W2 of following formula definition:

ΔW1＝|W(λ ₂，T ₁)-W(λ ₀，T ₀)| (9)

ΔW2＝|W(λ ₁，T ₀)-W(λ ₀，T ₀)| (10)

Satisfy following formula:

ΔW1＜0.035λrms (11)

ΔW2＜0.035λrms (12)

Wherein

Work as λ ₀During＜600nm, λ ₂=λ ₀+ 1.5 (nm) and

Work as λ ₀During 〉=600nm, λ ₂=λ ₀+ 6 (nm).

Operation of the present invention is identical with the 14th operation and effect with effect.

Under the preferable case, satisfy according to the following formula in the 35th the described invention according to the 36th described optical pick-up apparatus:

$\sqrt{{\left(\mathrm{\&Delta;W}1\right)}^2+{\left(\mathrm{\&Delta;w}2\right)}^2}<0.05\mathrm{\&lambda;rms}---\left(13\right)$

Operation of the present invention is identical with the 15th operation and effect with effect.

In according to the 37th described optical pick-up apparatus, in according to any one the described the present invention in the 27-36 item, object lens are object lens of finite conjugate type, and the divergent beams that are used for sending from light source focus on information recording surface, and satisfy following formula:

1.1＞f＞0.2 (13A)

Operation of the present invention is identical with the 16th operation and effect with effect.

According to the 38th described optical pick-up apparatus, when m when forming magnification according to the image of the object lens in the 37th the described invention, satisfies following formula:

0.2＞|m|＞0.02 (13B)

Operation of the present invention is identical with the 17th operation and effect with effect.

According to the 39th described optical pick-up apparatus, wherein, in according to the 37th or 38 described invention, object lens and light source are combined by actuator, are driven at least, so that follow the tracks of.Operation of the present invention is identical with the 26th operation and effect with effect.

According to the 40th described optical pick-up apparatus, satisfy the following formula in any one the described invention in the 21-39 item:

0.8＜d/f＜1.8 (14)

Wherein, d (mm) is the lens thickness along the optical axis of object lens, and f (mm) is a focal length.

Operation of the present invention is identical with the 18th operation and effect with effect.

According to the 41st described optical pick-up apparatus, wherein, in the described invention of any one in the 21-40 item, the design wavelength lambda of object lens ₀(nm) satisfy following formula:

500≥λ ₀≥350 (15)

Operation of the present invention is identical with the 19th operation and effect with effect.

Satisfy following formula in any one described invention in the 21-41 item according to the 42nd described optical pick-up apparatus:

$0.40\&le;(X1-X2)\&CenterDot;(N-1)/(\mathrm{NA}\&CenterDot;f\&CenterDot;\sqrt{(1+|m\left|\right)})\&le;0.63---\left(16\right)$

Wherein

X1: perpendicular to optical axis and and the outermost part of tangent plane, the top on light source-side optical surface and effective diameter in the optical surface (the edge light beam incides the position of NA on the surface of light source side wherein) of light source side between along the distance (mm) of optical axis direction, wherein, with reference to positive tangent plane along under the situation of the orientation measurement X1 of optical data recording medium its for just, along under the situation of the orientation measurement X1 of light source its for negative

X2: perpendicular to optical axis and and the optical data recording medium sidelight learn between the optical surface (the edge light beam incides the position of NA on the surface of optical data recording medium side wherein) of the optical data recording medium side in the outermost part of tangent plane, the top on surface and effective diameter distance (mm) along optical axis direction, wherein, with reference to positive tangent plane under the situation of the orientation measurement X2 of optical data recording medium its for just, it is for negative under the situation of the orientation measurement X2 of light source

N: in design wavelength lambda ₀The time the refractive index of object lens,

F: the focal length of object lens (mm), and

M: the image of object lens forms magnification.

Operation of the present invention is identical with the 20th operation and effect with effect.

Comprise optical pick-up apparatus according to the 43rd described optical information recording/reproducing apparatus, this optical pick-up apparatus comprises: light source; And convergence optical system, this system comprises object lens, be used for the beam convergence that will send from light source information recording surface to optical data recording medium, and this optical pick-up apparatus can write down and/or information reproduction by the beam convergence that will send from light source with the convergence optical system information recording surface to optical data recording medium, wherein, object lens are plastics simple lenses, and satisfy following formula:

NA≥0.8 (1)

1.0＞f＞0.2 (2)

Wherein, NA is the numerical aperture that information is write down and/or is rendered to the image-side of the required object lens of optical data recording medium, and f (mm) is the focal length of object lens.

Operation of the present invention is identical with the 1st operation and effect with effect.

According to the 44th described optical information recording/reproducing apparatus, wherein, in according to the 43rd described invention, when having wavelength X ₀(nm) (this is the first environment temperature T to the light of (this is its design wavelength) in environment temperature ₀=25 ℃) under W (λ when inciding object lens ₀, T ₀) be the RMS value of the residual aberration of object lens, and when having wavelength X ₀(nm) (this is the second environment temperature T to the light of (this is its design wavelength) in environment temperature ₁=55 ℃) under W (λ when inciding object lens ₀, T ₁) be the RMS value of the residual aberration of object lens, then by the Δ W of following formula definition:

ΔW＝|W(λ ₀，T ₁)-W(λ ₀，T ₀)| (3)

Satisfy following formula:

ΔW＜0.035λrms (4)

Operation of the present invention is identical with the 2nd operation and effect with effect.

According to the 45th described optical pick-up apparatus, wherein, in according to the 43rd or 44 described invention, the design wavelength lambda of Liar ₀Be no more than 500nm, under following situation: when wavelength is λ ₀(nm) (this is the first environment temperature T to light in environment temperature ₀=25 ℃) under fB (λ when inciding object lens ₀, T ₀) be the back focal length of object lens, when wavelength is λ ₁(nm) (this compares wavelength X ₀Long 5nm) (this is the first environment temperature T to light in environment temperature ₀=25 ℃) under fB (λ when inciding object lens ₁, T ₀) be the back focal length of object lens, then by the Δ fB of following formula definition

ΔfB＝|fB(λ ₁，T ₀)-fB(λ ₀，T ₀)| (5)

Satisfy following formula:

ΔfB＜0.001mm (6)

Operation of the present invention is identical with the 3rd operation and effect with effect.

According to the 46th described optical information recording/reproducing apparatus, wherein, in according to any one the described invention in the 43-45 item, object lens are object lens of finite conjugate type, be used for focusing on the information recording surface of optical data recording medium, and satisfy following formula from the divergent beams that light source sends:

0.8＞f＞0.2 (6A)

Operation of the present invention is identical with the 4th operation and effect with effect.

According to the 47th described optical information recording/reproducing apparatus, wherein, in according to the 46th described invention, when m was the image formation magnification of object lens, m satisfied following formula:

0.2＞|m|＞0.02 (6B)

Operation of the present invention is identical with the 5th operation and effect with effect.

According to the 48th described optical information recording/reproducing apparatus, wherein, in according to the 46th or 47 described invention, object lens and light source are combined by actuator, are driven at least to be used to follow the tracks of.Operation of the present invention is identical with the 26th operation and effect with effect.

According to the 49th described optical information recording/reproducing apparatus, comprise optical pick-up apparatus, this optical pick-up apparatus comprises: light source; And convergence optical system, this system comprises object lens, be used for the beam convergence that will send from light source information recording surface to optical data recording medium, and this optical pick-up apparatus can write down and/or information reproduction by the beam convergence that will send from light source with the convergence optical system information recording surface to optical data recording medium, wherein, object lens are the plastics simple lenses that comprise the ring-type phase structure at least one optical surface, the ring-type phase structure comprises a plurality of anchor rings, and form and make adjacent anchor ring produce predetermined optical path difference for incident light, and satisfy following formula:

NA≥0.8 (7)

1.3＞f＞0.2 (8)

Wherein, NA is the numerical aperture of the image-side of object lens, and this carries out information record for optical data recording medium and/or reproduces requiredly, and f (mm) is the focal length of object lens.

Operation of the present invention is identical with the 6th operation and effect with effect.

According to the 50th described optical information recording/reproducing apparatus, wherein, in according to the 49th described invention, the ring-type phase structure is the diffraction structure with function of the predetermined incident light of diffraction, object lens have constituted the convergent wave front, and this wave front is owing to focus on the information recording surface by the combination effect that diffraction effect and refraction effect obtained.Operation of the present invention is identical with the 7th operation and effect with effect.

According to the 51st described optical information recording/reproducing apparatus, wherein, in according to the 50th described invention, object lens have such spherical aberration feature: when the incident light wavelength became long wavelength, spherical aberration changed in the direction of undercorrection.Operation of the present invention is identical with the 8th operation and effect with effect.

According to the 52nd described optical information recording/reproducing apparatus, wherein, in according to the 50th or 51 described invention, when the optical path difference of adding the wave front of transmission by diffraction structure to by optical path difference function phi by following formula definition _bWhen representing:

Φ _b＝b ₂·h ²+b ₄·h ⁴+b ₆·h ⁶+...

Wherein, b ₂, b ₄, b ₆... be respectively the 2nd rank, the 4th rank, the 6th rank ... the optical path difference function coefficients), satisfy following formula:

-70＜(b ₄·h _MAX ⁴)/(f·λ ₀·10 ^-6·(NA·(1-m)) ⁴)＜-20 (8A)

Wherein, λ ₀(nm) be the design wavelength of object lens, h _MAXBe the effective diameter maximum height (mm) that has formed the optical surface of diffraction structure in the above, m is that the image of object lens forms magnification.Operation of the present invention is identical with the 9th operation and effect with effect.

According to the 53rd described optical information recording/reproducing apparatus, wherein, in according to the 49th described invention, the ring-type phase structure is by constituting adjacent anchor ring so that be shifted each other at optical axis direction, thereby produce predetermined optical path difference for incident light, object lens have constituted the convergent wave front, and this wave front is owing to refraction effect focuses on the information recording surface.Operation of the present invention is identical with the 10th operation and effect with effect.

According to the 54th described optical information recording/reproducing apparatus, wherein, in according to the 53rd described invention, when the anchor ring that comprises optical axis is called the center anchor ring, the toroid of anchor ring outside, contiguous center becomes along optical axis direction and moves, so that have the optical path length shorter than center anchor ring, toroid in the maximum effective diameter position becomes along optical axis direction and moves, so that have the neighbour nearly longer optical path length of its inboard anchor ring, anchor ring in 75% position of maximum effective diameter is formed mobile, so that have the shorter optical path length of anchor ring in neighbour nearly its inboard anchor ring and contiguous its outside.Operation of the present invention is identical with the 11st operation and effect with effect.

According to the 55th described optical information recording/reproducing apparatus, wherein, in according to the 53rd or 54 described invention, the sum of anchor ring from 3 to 20.Operation of the present invention is identical with the 12nd operation and effect with effect.

According to the object lens of the 56th described optical pick-up apparatus, wherein, in according to any one the described invention in the 53-55 item, work as Δ _j(μ m) formed in the ring-type phase structure that forms in the zone of height of 75% height to 100% of effective diameter maximum height of optical surface of ring-type phase structure mutually the boundary of contiguous anchor ring in the above along the step-size amounts of any step-length in the step-length of optical axis direction, and n is a design wavelength lambda ₀(nm) time during refractive index of object lens, by the m of following formula representative _j

m _j＝INT(X) (8B)

(X=Δ j (n-1)/(λ wherein ₀10 ^-3) and INT (X) be the integer that rounds up and obtained by to X) be to be not less than 2 integer.Operation of the present invention is identical with the 13rd operation and effect with effect.

According to the 57th described optical information recording/reproducing apparatus, wherein, in the described invention of any one in the 49-56 item, under following situation, when having wavelength X ₀(nm) (this is the first environment temperature T to the light of (this is its design wavelength) in environment temperature ₀=25 ℃) under W (λ when inciding object lens ₀, T ₀) be the RMS value of the residual aberration of object lens, when having wavelength X ₁(nm) (this compares wavelength X ₀Long 5nm) (this is the first environment temperature T to light in environment temperature ₀=25 ℃) under W (λ when inciding object lens ₁, T ₀) be the RMS value of the residual aberration of object lens, and when having wavelength X ₂(nm) (this is the second environment temperature T to light in environment temperature ₁=55 ℃) under W (λ when inciding object lens ₂, T ₁) be the RMS value of the residual aberration of object lens, then by the Δ W1 and the Δ W2 of following formula definition:

ΔW1＝|W(λ ₂，T ₁)-W(λ ₀，T ₀)| (9)

ΔW2＝|W(λ ₁，T ₀)-W(λ ₀，T ₀)| (10)

Satisfy following formula:

ΔW1＜0.035λrms (11)

ΔW2＜0.035λrms (12)

Wherein

Work as λ ₀During＜600nm, λ ₂=λ ₀+ 1.5 (nm) and

Work as λ ₀During 〉=600nm, λ ₂=λ ₀+ 6 (nm).

Operation of the present invention is identical with the 14th operation and effect with effect.

Under the preferable case, satisfy following formula in the 47th the described invention according to the 58th described optical information recording/reproducing apparatus:

$\sqrt{{\left(\mathrm{\&Delta;W}1\right)}^2+{\left(\mathrm{\&Delta;w}2\right)}^2}<0.05\mathrm{\&lambda;rms}---\left(13\right)$

Operation of the present invention is identical with the 15th operation and effect with effect.

According to the 59th described optical information recording/reproducing apparatus, wherein, in according to any one the described invention in the 49-58 item, object lens are object lens of finite conjugate type, be used for and focus on information recording surface from the divergent beams that light source sends, and satisfy following formula.Operation of the present invention is identical with the 16th operation and effect with effect.

1.1＞f＞0.2 (13A)

According to the 60th described optical information recording/reproducing apparatus, when m satisfies following formula when forming magnification according to the image of the object lens in the 59th the described invention:

Operation of the present invention is identical with the 17th operation and effect with effect.

0.2＞|m|＞0.02 (13B)

According to the 61st described optical information recording/reproducing apparatus, wherein, in according to the 59th or 60 described invention, object lens and light source are combined by actuator, are driven at least to be used to follow the tracks of.Operation of the present invention is identical with the 26th operation and effect with effect.

Satisfy following formula in any one described invention in the 43-61 item according to the 62nd described optical information recording/reproducing apparatus:

0.8＜d/f＜1.8 (14)

Wherein, d (mm) is the lens thickness along the optical axis direction of object lens, and f (mm) is a focal length.

Operation of the present invention is identical with the 18th operation and effect with effect.

According to the 63rd described optical information recording/reproducing apparatus, wherein, in the described invention of any one in the 43-62 item, the design wavelength lambda of object lens ₀(nm) satisfy following formula:

500≥λ ₀≥350 (15)

Operation of the present invention is identical with the 19th operation and effect with effect.

Satisfy following formula in any one described invention in the 43-63 item according to the 64th described optical information recording/reproducing apparatus:

$0.40\&le;(X1-X2)\&CenterDot;(N-1)/(\mathrm{NA}\&CenterDot;f\&CenterDot;\sqrt{(1+|m\left|\right)})\&le;0.63---\left(16\right)$

Wherein

X1: perpendicular to optical axis and and the outermost part of tangent plane, the top of the optical surface of light source side and effective diameter in the optical surface (the edge light beam incides the position of NA on the surface of light source side wherein) of light source side between along the distance (mm) of optical axis direction, wherein, with reference to positive tangent plane along X1 under the situation of the orientation measurement X1 of optical data recording medium for just, along X1 under the situation of the orientation measurement X1 of light source for negative

X2: perpendicular to optical axis and with the outermost part of tangent plane, the top of the optical surface of optical data recording medium side and effective diameter in the optical surface of optical data recording medium side, between (the edge light beam incides the position of NA on the surface of optical data recording medium side wherein) along the distance of optical axis direction, (mm), wherein, with reference to positive tangent plane along X2 under the situation of the orientation measurement X2 of optical data recording medium for just, along X2 under the situation of the orientation measurement X2 of light source for negative

N: in design wavelength lambda ₀The time the refractive index of object lens,

F: the focal length of object lens (mm), and

M: the image of object lens forms magnification.

Operation of the present invention is identical with the 20th operation and effect with effect.

Description of drawings

Fig. 1 is the schematic representation that shows the object lens 1 of present embodiment;

Fig. 2 is the schematic representation that shows the object lens 4 of present embodiment;

To be displays temperature rise under 30 ℃ the situation than design temperature Fig. 3, has the view of situation of the signal-lens wave front of biconvex plastics of two optical surfaces (aspheric surface);

Fig. 4 is the view of the configuration of the summary optical pick-up apparatus (optical information recording/reproducing apparatus) that shows first embodiment;

Fig. 5 is the view of explanation back focal length fB; And

Fig. 6 is the view of the configuration of the summary optical pick-up apparatus (optical information recording/reproducing apparatus) that shows second embodiment;

Embodiment

Describe according to embodiments of the invention below with reference to the accompanying drawings.Fig. 1 is the schematic representation that shows the object lens 1 of present embodiment, (A) is front view (FV), (B) is side view, (C) is the view of expansion side.Object lens 1 for example are applied to use the optical pick-up apparatus that is used for recoding/reproduction high density DVD, MO or the like of the short wavelength light source such as blueness-violet laser diode, and have and be used for the laser focusing that will send from the light source function to the information recording surface of CD.

Object lens 1 are the biconvex plastics simple lenses with two aspherics surfaces 2 and 3.Shown in Fig. 1 (A), be that the ring-type phase structure of the concentric diffraction structure at center forms on optical surface 2 as optical axis wherein.Shown in Fig. 1 (C), the ring-type phase structure has step delta as Fresnel lens at the boundary of each anchor ring along optical axis direction.The laser that incides any anchor ring of ring-type phase structure is diffracted into by perpendicular to the determined direction of the width of the anchor ring in the direction of optical axis (in this manual, such edge is called as " anchor ring spacing " perpendicular to the width of the anchor ring of the direction of optical axis).

The ring-type phase structure has such spherical aberration feature: along with the wavelength lengthy of incident light, spherical aberration changes in the direction of undercorrection.Because the signal-lens refractive index of plastics reduces owing to temperature rises, therefore, spherical aberration changes along the direction of exaggerated correction.On the other hand, the emission wavelength of laser diode rises owing to temperature and changes in elongated direction.For example, because blueness-violet laser diode makes variation in emission wavelength+0.05nm/ ℃ owing to temperature rises, therefore, and when temperature rises+30 ℃ the time, the wavelength 1.5nm that can extend.Correspondingly, because the object lens that provide have the spherical aberration feature that along with the wavelength lengthy of incident light spherical aberration changes in the direction of undercorrection, so, spherical aberration by the exaggerated correction of following temperature to rise to cause that variations in refractive index caused changes, and can come in addition balance by the variation of the spherical aberration of the undercorrection that variation caused of the emission wavelength of the laser diode that cause because temperature rises.

In order in this way to come correcting spherical aberration, must expressly produce the colored bulb surface aberration by the diffraction effect of ring-type phase structure.Yet, when attempting proofreading and correct fully when having the signal-lens thermal aberration of plastics of high NA, the generation of colored bulb surface aberration must be disposed more greatly, correspondingly, can not use to have the laser diode that departs from standard wavelength's emission wavelength owing to foozle.For object lens 1, in order to dwindle the correcting value of thermal aberration, focal length is configured to satisfy formula (8) or (13A), in addition, the generation of the correction of thermal aberration and colored bulb surface aberration coupling is so that satisfy formula (11) respectively to (13).Correspondingly, object lens 1 are the plastics simple lenses with high NA, still have the lens of good thermal aberration and colored bulb surface aberration.

Fig. 2 is the schematic representation that shows the object lens 4 of another embodiment, (A) is front view (FV), (B) is outboard profile.Optical surface 2, the same with object lens 1, be applied to use the optical pick-up apparatus that is used for recoding/reproduction high density DVD, MO or the like of the short wavelength light source such as blueness-violet laser diode, and have and be used for the laser focusing that to send from the light source function to the information recording surface of CD.

Object lens 4 are the biconvex plastics simple lenses with two aspherics surfaces 5 and 6.Shown in Fig. 2 (A), be that the ring-type phase structure of the concentric diffraction structure at center is formed on the optical surface 5 as optical axis wherein.The ring-type phase structure has step delta at the boundary of each anchor ring along optical axis direction, each step delta is what to determine by this way, so that make the optical path difference of wavelength of integral multiple of the wavelength the when laser of transmission by adjacent anchor ring has 25 ℃ (this is a design temperature).

In addition, shown in Fig. 2 (B), this ring-type phase structure comprises at least one anchor ring, this toroid becomes at optical axis direction and moves, so that have than being positioned near its inboard short optical path length of anchor ring, and comprise at least one anchor ring, this toroid becomes at optical axis direction and moves, so that have than being positioned near its inboard long optical path length of anchor ring, wherein, be formed in optical axis direction and move so that have than the anchor ring that is positioned near the short optical path length of its anchor ring inboard, move so that have than the anchor ring that is positioned near the long optical path length of its anchor ring inboard and compare with being formed in optical axis direction, a side nearer at the distance optical axis forms.Below, will the principle of in this way definite ring-type phase structure to the correction of the signal-lens thermal aberration of plastics be described.

Fig. 3 is the view that is presented at the situation of the signal-lens wave front of biconvex plastics that has two optical surfaces (aspheric surface) under the situation of temperature than 30 ℃ of design temperature risings, and transverse axis is represented the effective radius of optical surface, and the longitudinal axis is represented optical path difference.In the plastics simple lens, the influence of the change of refractive that causes by following temperature to rise produces spherical aberration, and wave front changes along with the lines Ag among Fig. 3.Lines Bg among Fig. 3 has shown the optical path difference of adding the wave front of transmission by the ring-type phase structure of determining by mode as described above to, and lines Cg has shown that transmission is by the situation of the wave front of ring-type phase structure under 30 ℃ the situation of rising than design temperature.Be appreciated that from lines Bg and Cg, under the situation of temperature than 30 ℃ of design temperature risings, because transmission is by the wave front of plastics ring-type phase structure and the balance of the signal-lens wave front of plastics, the wave front of laser that focuses on the information recording surface of CD becomes the good wave front that leniently view does not have optical path difference, and the signal-lens thermal aberration of plastics is proofreaied and correct by the ring-type phase structure.

The same with the situation of proofreading and correct thermal aberration as the diffraction effect of diffraction structure by the ring-type phase structure, proofread and correct under the situation of the signal-lens thermal aberration of plastics in effect with high NA by the ring-type phase structure determined by above mode, can not use to have the laser diode that departs from standard wavelength's emission wavelength owing to foozle, become too big because attempt proofreading and correct fully the generation that thermal aberration can cause the colored bulb surface aberration.

For object lens 4, in order to dwindle the correcting value of thermal aberration, focal length is configured to satisfy formula (8) or (13A), in addition, the generation of the correction of thermal aberration and colored bulb surface aberration coupling is so that satisfy formula (11) respectively to (13).Correspondingly, object lens 4 are the plastics simple lenses with high NA, and are the lens with good thermal aberration and colored bulb surface aberration, and are the same with object lens 1.

Fig. 4 is the view that summary shows the configuration of the optical pick-up apparatus (optical information recording/reproducing apparatus) that is equipped with object lens of the present invention.Optical pick-up apparatus 7 comprises as the laser diode 8 of light source and object lens 9.

Laser diode 8 is to produce the blueness based on GaN-violet laser diode that wavelength is approximately the light of 400nm.Except the blueness based on GaN as described above-violet laser diode, the light source that the generation wavelength is approximately the light of 400nm can use SHG blueness-violet laser diode.

Object lens 9 are any one in the object lens 4 of the object lens 1 of its focal length plastics simple lens of satisfying formula (2), Fig. 1 and Fig. 2.Object lens 9 comprise the flange section 9A perpendicular to optical axis extending.Object lens 9 can be connected to optical pick-up apparatus 7 exactly by flange section 9A.The numerical aperture of the object lens 9 of CD 10 1 sides is no less than 0.80.

Also pass through collimation lens 12 and quarter-wave plate 13 from the divergent beams transmission that laser diode 8 sends by polarization beam splitter 11; to become the circular polarization parallel beam; subsequently; beam diameter is regulated by diaphragm 14, and is become one by the protective seam 10A of the CD 10 of high density DVD and the luminous point that forms by object lens 9 on information recording surface 10B.For object lens 9, carry out focus control and tracking Control by being positioned at its actuator 15 on every side.

By the folded light beam of the modulated with information bits among the information recording surface 10B once more transmission by object lens 9, diaphragm 14, quarter-wave plate 13 and collimation lens 12, subsequently, being polarized beam splitter 11 becomes focused beam and is reflected, by means of having obtained astigmatic difference, and focus on the photodetector 18 by cylindrical lens 16 and concavees lens 17.Subsequently, can read the information of record on the CD 10 by using the output signal of photodetector 18.

Fig. 6 is the view that summary shows the configuration of another optical pick-up apparatus (optical information recording/reproducing apparatus) that is equipped with object lens of the present invention.Optical pick-up apparatus 7 ' comprise laser diode 8 and object lens 9 as light source.

Laser diode 8 is to produce the blueness based on GaN-violet laser diode that wavelength is approximately the light of 400nm.Except the blueness based on GaN as described above-violet laser diode, the light source that the generation wavelength is approximately the light of 400nm can use SHG blueness-violet laser diode.

Object lens 9 are any one in the object lens 4 of the object lens 1 of its focal length plastics simple lens of satisfying formula (6A), Fig. 1 as described above and Fig. 2.Object lens 9 are object lens of finite conjugate type, and the protective seam 10A that is used for the CD 10 by high density DVD will focus on information recording surface 10B from the divergent beams that laser diode 8 sends.Object lens 9 comprise the flange section 9A perpendicular to optical axis extending.Object lens 9 can by flange section 9A be connected to exactly optical pick-up apparatus 7 '.The numerical aperture of the object lens 9 of CD 10 1 sides is no less than 0.80.

Also pass through quarter-wave plate 13 from the divergent beams transmission that laser diode 8 sends by polarization beam splitter 11; to become circularly polarized light; subsequently; beam diameter is regulated by diaphragm 14, and is become one by the protective seam 10A of the CD 10 of high density DVD and the luminous point that forms by object lens 9 on information recording surface 10B.By the folded light beam of the modulated with information bits among the information recording surface 10B once more transmission by object lens 9, diaphragm 14 and quarter-wave plate 13, subsequently, be polarized beam splitter 11 reflection, by means of having obtained astigmatic difference, and focus on the photodetector 18 by cylindrical lens 16 and concavees lens 17.Subsequently, can read the information of record on the CD 10 by using the output signal of photodetector 18.

Optical pick-up apparatus 7 ' in, laser diode 8, object lens 9, polarization beam splitter 11, quarter-wave plate 13, cylindrical lens 16, concavees lens 17 and photodetector 18 all are integrated on the substrate as module.In tracking Control, these assemblies are driven as a whole by actuator 19.

Next, six preferred exemplary of embodiment as described above will be introduced.Example 1 to 6 is the object lens that are applied to the optical pick-up apparatus of high density DVD, and wherein, the wavelength that is used for recoding/reproduction information is 405nm, and the thickness of protective seam is 0.1mm.Example 1 is such plastics simple lens, wherein, by focal length is set so that satisfy formula (2), the generation that can suppress thermal aberration and longitudianal aberration is low, example 2 and 3 boths are such plastics simple lenses, wherein, proofread and correct thermal aberration by the effect that goes up the ring-type phase structure that forms at first surface (optical surface of light source one side).Example 4 is plastics simple lenses of finite conjugate type, wherein, by focal length is set so that satisfy formula (6A), the generation that can suppress thermal aberration and longitudianal aberration is low, example 5 and 6 boths are plastics simple lenses of finite conjugate type, wherein, proofread and correct thermal aberration by the effect that goes up the ring-type phase structure that forms at first surface (optical surface of light source one side).

Table 4 has shown the lens data of the object lens of example 1, and table 5 has shown the lens data of the object lens of example 2, and table 6 has shown the lens data of the object lens of example 3.In table 4,5 and 6 lens data, r (mm) represents radius-of-curvature, d (mm) presentation surface distance, and the refractive index when N405 represents that wavelength is 405nm, Vd represents the Abbe number of d in capable.

Table 4

Surface number	r(mm)	d(mm)	N405	vd	Remarks
						0		∞			Light source
1 2	0.3353 -0.3615	0.6600 0.0762	1.56013	56.7	Object lens
						3 4	∞ ∞	0.1000	1.61950	30.0	Protective seam

The non-spherical surface coefficient

	First surface	Second surface
			K A4 A6 A8 A10 A12 A14 A16 A18 A20	-6.9542E-01 7.9891E-01 1.3935E+00 3.3472E+01 -7.8778E+01 -7.8324E+02 6.6992E+03 3.4753E+04 -1.9498E+05 -5.8872E+05	-1.7907E+01 1.5728E+01 -3.5161E+02 3.4150E+03 -1.3187E+04 -5.2600E+02

Table 5

Surface number	r(mm)	d(mm)	N405	vd	Remarks
						0		∞			Light source
1 2	0.6157 -0.9615	1.1400 0.2018	1.56013	56.7	Object lens
						3 4	∞ ∞	0.1000	1.61950	30.0	Protective seam

The non-spherical surface coefficient

	First surface	Second surface
			K A4 A6 A8 A10 A12 A14 A16 A18 A20	-6.3213E-01 5.0716E-02 5.2621E-02 5.2319E-01 -7.1277E-01 -9.9374E-01 3.4591E+00 -2.1262E+00 3.3120E+00 -8.7979E+00	-4.7996E+01 1.7646E+00 -9.5272E+00 1.8626E+01 1.2599E+00 -4.0506E+01

The Difraction surface coefficient

	First surface
		b2 b4 b6 b8 b10	-2.4634E-02 -5.1397E-02 5.7231E-02 -9.6553E-02 -4.4043E-02

Table 6

Surface number	r(mm)	d(mm)	N405	vd	Remarks
						0		∞			Light source
1 2	See below-0.5177	See below 0.1190	1.56013	56.7	Object lens
						3 4	∞ ∞	0.1000	1.61950	30.0	Protective seam

The non-spherical surface coefficient

	Second surface
		K A4 A6 A8 A10 A12 A14 A16 A18 A20	-2.7583E+01 5.6751E+00 -6.8184E+01 3.5710E+02 -7.5179E+02 -4.5183E+01

Example 1 is such plastics simple lens: the incident beam diameter is 0.8mm, and focal distance f=0.47mm, NA are 0.85, and design wavelength is 405nm, and design temperature is 25 ℃.Because focal length is set to satisfy formula (2), so it is the plastics simple lens with high NA, and is all reasonable camera lens of spherical aberration when producing thermal aberration and mode hopping, and is as shown in table 7.

Table 7

	Thermal aberration (+30 ℃)	Mode hopping (+1nm)
			Example 1	0.020λrms	0.028λrms

In table 7, in order to calculate thermal aberration, the change of refractive rate of following the temperature rising to cause of plastic lens is-9.0 * 10 ^-5, and the wavelength change rate of the incident light of following temperature to rise to cause is+0.05nm/ ℃.Spherical aberration when producing mode hopping in order to calculate suppose that the deviation owing to the wavelength of blueness-violet laser diode that mode hopping produces is+1nm that the focal position of object lens is fixed on the optimized image surface location of 405nm.

For the object lens of example 1, the value of Δ W (formula (3)) is Δ W=0.019 λ rms, because W is (λ ₀, T ₀)=0.001 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₀, T ₁)=0.020 λ rms (λ ₀=405nm, T ₁=55 ℃).The value of Δ fB (formula (5)) is Δ fB=0.0004mm, because fB is (λ ₀, T ₀)=0.0762mm (λ ₀=405nm, T ₀=25 ℃), fB (λ ₁, T ₀)=0.0766mm (λ ₁=410nm, T ₀=25 ℃).As shown in Figure 5, the back focal length fB in this instructions is illustrated in the optical surface S2 of optical data recording medium one side object lens and the light beam incidence surface S of optical data recording medium _INBetween along the distance of optical axis.

Example 2 is such plastics simple lenses: the incident beam diameter is 1.5mm, and focal distance f=0.88mm, NA are 0.85, and design wavelength is 405nm, and design temperature is 25 ℃, is the appropriate objective lens as the object lens 1 among the embodiment as described above.As shown in table 8, formed its border in the effective diameter on the first surface of the object lens of example 2 and comprised that 80 sections ring-type phase structures along about 0.7 μ m of optical axis direction to the step delta of 1.2 μ m are as diffraction structure.When making when the laser that blueness-the violet laser diode sends incides the ring-type phase structure, produce the 1st rank diffraction light in case have the maximum diffraction light quantity (that is, the ring-type phase structure wavelength be 405nm and diffraction orders be 1 o'clock optimised).By the diffraction effect of ring-type phase structure, thermal aberration is well proofreaied and correct.

Table 8

The anchor ring numbering	Beginning height (mm)	Finish height (mm)
			1	0.000	0.126
2	0.126	0.176
			3	0.176	0.213
4	0.213	0.243
			5	0.243	0.269
6	0.269	0.291
			7	0.291	0.312
8	0.312	0.330
			9	0.330	0.347
10	0.347	0.363
			11	0.363	0.378
12	0.378	0.392
			13	0.392	0.406
14	0.406	0.418
			15	0.418	0.430
16	0.430	0.441
			17	0.441	0.452
18	0.452	0.463
			19	0.463	0.473
20	0.473	0.482
			21	0.482	0.491
22	0.491	0.500
			23	0.500	0.509
24	0.509	0.517
			25	0.517	0.525
26	0.525	0.533
			27	0.533	0.540
28	0.540	0.547
			29	0.547	0.554
30	0.554	0.561
			31	0.561	0.568
32	0.568	0.574
			33	0.574	0.580
34	0.580	0.586
			35	0.586	0.592
36	0.592	0.598
			37	0.598	0.603
38	0.603	0.609
			39	0.609	0.614
40	0.614	0.619

The anchor ring numbering	Beginning height (mm)	Finish height (mm)
			41	0.619	0.624
42	0.624	0.629
			43	0.629	0.633
44	0.633	0.638
			45	0.638	0.642
46	0.642	0.647
			47	0.647	0.651
48	0.651	0.655
			49	0.655	0.659
50	0.659	0.663
			51	0.663	0.667
52	0.667	0.671
			53	0.671	0.675
54	0.675	0.678
			55	0.678	0.682
56	0.682	0.685
			57	0.685	0.689
58	0.689	0.692
			59	0.692	0.695
60	0.695	0.699
			61	0.699	0.702
62	0.702	0.705
			63	0.705	0.708
64	0.708	0.711
			65	0.711	0.714
66	0.714	0.717
			67	0.717	0.719
68	0.719	0.722
			69	0.722	0.725
70	0.725	0.727
			71	0.727	0.730
72	0.730	0.733
			73	0.733	0.735
74	0.735	0.738
			75	0.738	0.740
76	0.740	0.743
			77	0.743	0.745
78	0.745	0.747
			79	0.747	0.750
80	0.750	0.752

For the object lens of example 2, the value of Δ W1 (formula (9)) is Δ W1=0.019 λ rms, because W is (λ ₀, T ₀)=0.001 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₂, T ₁)=0.020 λ rms (λ ₂=406.5nm, T ₁=55 ℃).The value of Δ W2 (formula (10)) is Δ W2=0.021 λ rms, because W is (λ ₀, T ₀)=0.001 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₁, T ₀)=0.022 λ rms (λ ₁=410nm, T ₀=25 ℃).The value of the formula in the example 2 (8A) is-42.

Example 3 is such plastics simple lenses: the incident beam diameter is 1.0mm, and focal distance f=0.59mm, NA are 0.85, and design wavelength is 405nm, and design temperature is 25 ℃, is the appropriate objective lens as the object lens 4 among the embodiment as described above.As shown in table 6, in the effective diameter on the first surface of the object lens of example 3, formed its border and comprised that 6 sections ring-type phase structures along about 1.3 μ m of optical axis direction to the step delta of 2.3 μ m are as diffraction structure.When making from laser incident ring-type phase structure that blueness-violet laser diode sends, produce the 1st rank diffraction light in case have the maximum diffraction light quantity (that is, the ring-type phase structure wavelength be 405nm and diffraction orders be 1 o'clock optimised).By the effect of ring-type phase structure, thermal aberration is well proofreaied and correct.

For the object lens of example 3, the value of Δ W1 (formula (9)) is Δ W1=0.013 λ rms, because W is (λ ₀, T ₀)=0.002 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₂, T ₁)=0.015 λ rms (λ ₂=406.5nm, T ₁=55 ℃).The value of Δ W2 (formula (10)) is Δ W2=0.013 λ rms, because W is (λ ₀, T ₀)=0.002 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₁, T ₁)=0.015 λ rms (λ ₁=410nm, T ₀=25 ℃).For the value of the formula in the example 3 (8B), the 5th ring surface is m _jThe=3, the 6th ring surface is m _j=3.

Example 2 and 3 object lens all are provided with the focal length that satisfies formula (8), thereby reduce the correcting value of thermal aberration, in addition, also has such configuration, wherein, the generation of the correction of thermal aberration and colored bulb surface aberration coupling is so that satisfy formula (11) respectively to (13).Therefore, they are the plastics simple lenses with high NA, still have the lens of good thermal aberration and colored bulb surface aberration, and are as shown in table 9.

Table 9

	Thermal aberration (+30 ℃)	The colored bulb surface aberration (+5nm)
			Example 2 examples 3	0.020λrms 0.015λrms	0.022λrms 0.015λrms

In table 9, in order to calculate thermal aberration, the change of refractive rate of following the temperature rising to cause of plastic lens is-9.0 * 10 ^-5, the wavelength change rate of the incident light of following temperature to rise to cause is+0.05nm/ ℃.

Table 11 has shown the lens data of the object lens of example 5, and table 15 has shown the lens data of the object lens of example 6.In table 10,11 and 15 lens data, r (mm) represents radius-of-curvature, d (mm) presentation surface distance, and the refractive index when N405 represents that wavelength is 405nm, Vd represents the Abbe number of d in capable.

Table 10

[example 4]

Surface number	r(mm)	d(nm)	N405	vd	Remarks
						0		3.7500			Light source
1 2	0.2136 -0.2910	0.3750 0.0742	1.56013	56.7	Object lens
						3 4	∞ ∞	0.1000	1.61950	30.0	Protective seam

The non-spherical surface coefficient

	First surface	Second surface
			K A4 A6 A8 A10 A12 A14 A16 A18 A20	-6.5380E-01 5.9438E-01 2.0735E+01 -2.1582E+01 2.8863E+03 5.9020E+03 -5.2839E+05 -1.7610E+06 4.3204E+07 -3.1642E+08	-2.9101E-01 -8.1619E+00 3.9794E+01 -1.4824E+03 3.2709E+04 -4.4513E+05 3.4193E+06 -1.1349E+07

Table 11

[example 5]

Surface number	r(mm)	d(mm)	N405	vd	Remarks
						0		5.0000			Light source
1 2	0.2769 -0.3763	0.5240 0.1000	1.56013	56.7	Object lens
						3 4	∞ ∞	0.1000	1.61950	30.0	Protective seam

The non-spherical surface coefficient

	First surface	Second surface
			K A4 A6 A8 A10 A12 A14 A16 A18 A20	-6.8145E-01 -3.0262E-02 1.1148E+00 -1.5150E+01 3.1738E+02 2.4517E+02 -1.9895E+04 -2.8487E+03 9.0622E+05 -4.9449E+06	-9.4697E+00 1.9844E+01 -4.5104E+02 6.0959E+03 -5.2115E+04 2.5579E+05 -5.5335E+05

The Difraction surface coefficient

Table 15

	Thermal aberration (+30 ℃)	The colored bulb surface aberration (+5nm)
			Example	0.018λrms	0.019λrms

Example 4 is such plastics simple lenses: focal length is 0.30mm, and NA is 0.85, and design wavelength is 405nm, and it is-0.084 that image forms magnification f, and design temperature is 25 ℃.Be placed under the situation of surperficial apical position of the first surface in the object lens of example 4 at the diaphragm that will regulate light beam, its diaphragm diameter becomes 0.532mm.Because focal length is set to satisfy formula (6A), so it is the plastics simple lens with high NA of finite conjugate type, and still all reasonable camera lens of spherical aberration when producing thermal aberration and mode hopping is as shown in table 12.

Table 12

Surface number	r(mm)	d(mm)	N405	vd	Remarks
						0		5.000			Light source
1 2	See below-0.3424	See below 0.0956	1.56013	56.7	Object lens
						3 4	∞ ∞	0.1000	1.61950	30.0	Protective seam

The non-spherical surface coefficient

	Second surface
		K A4 A6 A8 A10 A12 A14 A16 A18 A20	-9.1512E+00 1.9167E+01 -4.5257E+02 6.1555E+03 -5.1764E+04 2.4522E+05 -5.0382E+05

In table 12, in order to calculate thermal aberration, the change of refractive rate of following the temperature rising to cause of plastic lens is-9.0 * 10 ^-5, the wavelength change rate of the incident light of following temperature to rise to cause is+0.05nm/ ℃.Spherical aberration when producing mode hopping in order to calculate suppose owing to the deviation of the wavelength of blueness-violet laser diode that mode hopping produces to be+1nm, and the focal position of object lens is fixed on the optimized image surface location of 405nm.

For the object lens of example 4, the value of Δ W (formula (3)) is Δ W=0.028 λ rms, because W is (λ ₀, T ₀)=0.000 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₀, T ₁)=0.028 λ rms (λ ₀=405nm, T ₁=55 ℃).The value of Δ fB (formula (5)) is Δ fB=0.0004mm, because fB is (λ ₀, T ₀)=0.0742mm (λ ₀=405nm, T ₀=25 ℃), fB (λ ₁, T ₀)=0.0746mm (λ ₁=410nm, T ₀=25 ℃).

Example 5 is such plastics simple lens: focal distance f=0.40mm, and NA is 0.85, and design wavelength is 405nm, and it is-0.083 that image forms magnification f, and design temperature is 25 ℃, is the appropriate objective lens as the object lens 1 among the embodiment as described above.Be placed under the situation of surperficial apical position of the first surface in the object lens of example 5 at the diaphragm that will regulate light beam, its diaphragm diameter becomes 0.708mm.As shown in table 13, in the effective diameter on the first surface of the object lens of example 5, formed its border and comprised that 27 sections ring-type phase structures along about 0.7 μ m of optical axis direction to the step delta of 1.1 μ m are as diffraction structure.When making, produce the 1st rank diffraction light so that have maximum diffraction light quantity (that is, the ring-type phase structure is that 405nm and diffraction orders are optimised (diffraction efficiency is the highest) at wavelength) at 1 o'clock from laser incident ring-type phase structure that blueness-violet laser diode sends.By the diffraction effect of ring-type phase structure, thermal aberration is well proofreaied and correct.

Table 13

	Thermal aberration (+30 ℃)	Mode hopping (+1nm)
			Example 4	0.028λrms	0.024λrms

For the object lens of example 5, the value of Δ W1 (formula (9)) is Δ W1=0.018 λ rms, because W is (λ ₀, T ₀)=0.000 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₂, T ₁)=0.018 λ rms (λ ₂=406.5nm, T ₁=55 ℃).The value of Δ W2 (formula (10)) is Δ W2=0.019 λ rms, because W is (λ ₀, T ₀)=0.000 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₁, T ₀)=0.019 λ rms (λ ₁=410nm, T ₀=25 ℃).

The object lens of example 5 are provided with focal length so that satisfy formula (13A), thereby reduce the correcting value of thermal aberration, in addition, also have such configuration, and wherein, the generation of the correction of thermal aberration and colored bulb surface aberration coupling is so that satisfy formula (9) respectively to (11).Therefore, it is the plastics simple lens with high NA of finite conjugate type, still has the lens of good thermal aberration and colored bulb surface aberration, and is as shown in table 14.

Table 14

The anchor ring numbering	Beginning height (mm)	Finish height (mm)
			1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27	0.000 0.187 0.218 0.238 0.254 0.266 0.277 0.286 0.294 0.301 0.308 0.314 0.319 0.325 0.330 0.334 0.339 0.343 0.347 0.351 0.354 0.358 0.361 0.364 0.368 0.371 0.373	0.187 0.218 0.238 0.254 0.266 0.277 0.286 0.294 0.301 0.308 0.314 0.319 0.325 0.330 0.334 0.339 0.343 0.347 0.351 0.354 0.358 0.361 0.364 0.368 0.371 0.373 0.376

In table 14, in order to calculate thermal aberration, the change of refractive rate of following the temperature rising to cause of plastic lens is-9.0 * 10 ^-5, the wavelength change rate of the incident light of following temperature to rise to cause is+0.05nm/ ℃.The value of the formula in the example 5 (8A) is-45.

Example 6 is such plastics simple lens: focal distance f=0.40mm, and NA is 0.85, and design wavelength is 405nm, and it is-0.083 that image forms magnification f, and design temperature is 25 ℃, is the appropriate objective lens as the object lens 4 among the embodiment as described above.Be placed under the situation of surperficial apical position of the first surface in the object lens of example 6 at the diaphragm that will regulate light beam, its diaphragm diameter becomes 0.702mm.As shown in Table 15, in the effective diameter on the first surface of the object lens of example 6, formed its border and comprised that 7 sections ring-type phase structures along about 1.5 μ m of optical axis direction to the step delta of 4.0 μ m are as diffraction structure.By the diffraction effect of ring-type phase structure, thermal aberration is well proofreaied and correct.

For the object lens of example 6, the value of Δ W1 (formula (9)) is Δ W1=0.018 λ rms, because W is (λ ₀, T ₀)=0.002 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₂, T ₁)=0.020 λ rms (λ ₂=406.5nm, T ₁=55 ℃).The value of Δ W2 (formula (10)) is Δ W2=0.030 λ rms, because W is (λ ₀, T ₀)=0.002 λ rms (λ ₀=405nm, T ₀=25 ℃), W (λ ₁, T ₁)=0.032 λ rms (λ ₁=410nm, T ₀=25 ℃).For the value of the formula in the example 6 (8B), the 6th ring surface is m _jThe=5, the 7th ring surface is m _j=7.

The object lens of example 6 are provided with focal length so that satisfy formula (6A), thereby reduce the correcting value of thermal aberration, in addition, also have such configuration, and wherein, the generation of the correction of thermal aberration and colored bulb surface aberration coupling is so that satisfy formula (11) respectively to (13).Correspondingly, it is the plastics simple lens with high NA of finite conjugate type, still has the lens of good thermal aberration and colored bulb surface aberration, and is shown in table 16.

Table 16

	Thermal aberration (+30 ℃)	The colored bulb surface aberration (+5nm)
			Example 6	0.020λrms	0.0320λrms

In table 16, in order to calculate thermal aberration, the change of refractive rate of following the temperature rising to cause of plastic lens is-9.0 * 10 ^-5, the wavelength change rate of the incident light of following temperature to rise to cause is+0.05nm/ ℃.

The value of the formula as described above (16) in each example (is $\{(X1-X2)\&CenterDot;(N-1)/\mathrm{NA}\&CenterDot;f\&CenterDot;\sqrt{(1+|m\left|\right)}\}$ As follows:

Example 1:0.471

Example 2:0.454

Example 3:0.490

Example 4:0.576

Example 5:0.538

Example 6:0.558

According to the present invention, a kind of plastics simple lens can be provided, this plastics simple lens is suitable as the object lens that use the signal-lens optical pick-up apparatus of plastics with high NA, wherein, available temperature range is enough wide, the decline of the focusing power that causes owing to the mode hopping of light source is slight, therefore, can provide a kind of have high performance optical pick-up apparatus and optical information recording/reproducing apparatus.

Claims (8)

1. object lens that are used for optical pick-up apparatus,

Wherein, this optical pick-up apparatus comprises: light source; And

Object lens are used for the beam convergence that will send from the light source information recording surface to optical data recording medium, and

This optical pick-up apparatus can write down and/or information reproduction by the beam convergence that will send from light source with the object lens information recording surface to optical data recording medium,

Wherein, object lens are plastics simple lenses, and this plastics simple lens comprises the ring-type phase structure at least one optical surface, and this ring-type phase structure comprises a plurality of anchor rings, and form and make adjacent anchor ring produce predetermined optical path difference for incident light,

Wherein, when the anchor ring that comprises optical axis is called the center anchor ring, the toroid of the outside of contiguous center anchor ring becomes along optical axis direction and moves, so that have the optical path length shorter than center anchor ring, toroid in the maximum effective diameter position becomes along optical axis direction and moves, so that have the long optical path length of neighbour nearly its inboard anchor ring, and

Wherein, object lens satisfy following formula:

NA≥0.8

1.3＞f＞0.2

Wherein, NA carries out the image-side numerical aperture that information write down and/or reproduced required object lens to optical data recording medium, and f is the focal length of object lens, and the unit of f is mm.

2. the object lens of optical pick-up apparatus according to claim 1, wherein, the toroid in 75% position of maximum effective diameter becomes and is moved, so that have the short optical path length of anchor ring in neighbour nearly its inboard anchor ring and contiguous its outside.

3. the object lens of optical pick-up apparatus according to claim 1, wherein, the sum of anchor ring from 3 to 20.

4. the object lens of optical pick-up apparatus according to claim 1, wherein, object lens have such spherical aberration feature: when the incident light wavelength was elongated, spherical aberration changed proofreading and correct more not enough direction.

5. the object lens of optical pick-up apparatus according to claim 1 wherein, are the Δ of μ m when unit _jBe to have formed in the ring-type phase structure that forms in the zone of height of 75% height to 100% of effective diameter maximum height of optical surface of ring-type phase structure mutually the boundary of contiguous anchor ring in the above, and n is that unit is the design wavelength lambda of nm along the step-size amounts of step-length arbitrarily in the step-length of optical axis direction ₀The time object lens refractive index the time, by the m of following formula representative _j

m _j＝INT(X)

Be to be not less than 2 integer, X=Δ wherein _j(n-1)/(λ ₀10 ^-3), and INT (X) is the integer that rounds up and obtained by to X.

6. the object lens of optical pick-up apparatus according to claim 1, wherein, object lens satisfy following formula:

0.8＜d/f＜1.8

Wherein, d is the lens thickness along the optical axis of object lens, and its unit is mm, and f is the focal length that is used for the object lens of light source, and its unit is mm.

7. the object lens of optical pick-up apparatus according to claim 5, wherein, the unit of object lens is the design wavelength lambda of nm ₀Satisfy following formula:

500≥λ ₀≥350。

8. the object lens of optical pick-up apparatus according to claim 1, wherein, described ring-type phase structure is proofreaied and correct thermal aberration.

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