JP3332155B2 - Objective lens and optical pickup device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device capable of recording and reproducing information on and from an optical recording medium such as an optical disk, and an objective lens used in the optical pickup device. The present invention relates to an optical pickup device capable of accurately recording and reproducing information on a recording medium and an objective lens used in the optical pickup device and having a variable numerical aperture.

[0002]

2. Description of the Related Art In recent years, optical recording media such as optical discs are capable of recording a large amount of information signals at a high density, and have been used in many fields such as audio, video, and computers. Currently, commercially available optical disks such as a compact disk (CD), a video disk, a mini disk (MD), and a magneto-optical disk for a computer use a substrate having a thickness of 1.2 mm. For this reason, a general objective lens used in an optical pickup device is designed to correct aberrations caused by a substrate having a thickness of 1.2 mm.

Various studies have been made to increase the recording capacity of an optical disc. For example, a method of improving the optical resolution by increasing the numerical aperture NA of an objective lens, and shortening the wavelength used. A method is used.

Generally, the condensed beam diameter φ has a relationship expressed by the following equation 1 with respect to the numerical aperture NA of the objective lens and the laser wavelength λ.

Φ = K × λ / NA (K: constant) (Equation 1)

Therefore, when the numerical aperture NA of the objective lens is increased, the condensed beam diameter φ decreases proportionally. On the other hand, the permissible error of the disk inclination decreases in proportion to the cube of the numerical aperture NA. Therefore, it is necessary to reduce the thickness of the disk substrate in order to make the allowable error of the disk inclination approximately the same. For example, when the numerical aperture NA of the objective lens is 0.5 and the disk inclination tolerance is about the same as that when the substrate thickness is 1.2 mm, the numerical aperture NA of the objective lens is 0.6.
Thus, the thickness of the substrate becomes about 0.6 mm. In other words, in order to increase the density, the thickness of the substrate and the numerical aperture NA of the objective lens are required.
Therefore, if the thickness of the substrate is changed, the compatibility with the conventional optical disk cannot be maintained, and the numerical aperture NA of the objective lens needs to be changed correspondingly.

Therefore, the numerical aperture N of the objective lens
Several methods for changing A have been proposed.

For example, in Japanese Patent Application Laid-Open No. 8-287508, an aperture switching plate having a mechanism for selectively switching a plurality of apertures having different diameters and an objective lens are arranged on an optical path and mounted on a movable portion. By switching the aperture of the aperture switching plate according to the thickness of the optical disk, the numerical aperture NA of the objective lens can be changed.
Is disclosed (conventional example 1).

Japanese Patent Application Laid-Open No. 6-124777 discloses that a liquid crystal filter, a polarizing beam splitter, and an objective lens are arranged on an optical path, a polarization direction of transmitted light is arbitrarily selected by the liquid crystal filter, and the transmitted light is selected. There is disclosed a method of changing the numerical aperture of an objective lens according to the thickness of an optical disk by changing the shape of a light beam by transmitting the light beam through a polarizing beam splitter (conventional example 2).

In this liquid crystal filter, for example, an electrode is divided into concentric circles such as an inner peripheral portion and an outer peripheral portion and patterned, and the polarization direction becomes 9 with application of a voltage.
It is divided into a part that rotates 0 degrees and a part that does not rotate. Therefore, the transmitted light of the liquid crystal filter is divided into a reflected component and a transmitted component when passing through the polarizing beam splitter, and the numerical aperture NA of the objective lens is changed by changing the diameter of the light beam incident on the objective lens.

Further, Japanese Patent Application Laid-Open No. 9-54977 discloses that
A method using an aperture limiting element in which a transmission region changes according to a wavelength is disclosed (conventional example 3).

In this aperture limiting element, for example, a wavelength filter film is formed only outside a circular region having a diameter smaller than the effective diameter of the objective lens, and a phase compensation film is formed inside the circular region. For this reason, reflection and transmission are switched according to the wavelength outside the circular region, whereas light incident into the circular region is transmitted regardless of the wavelength. That is, the numerical aperture NA of the objective lens is changed by changing the diameter of a beam transmitted through the aperture limiting element according to the wavelength.

[0013]

However, in the case of the above-mentioned method using the aperture switching plate of the first conventional example, it is necessary to newly provide an aperture switching plate having a high-precision aperture switching mechanism. In addition to the increase in size, the mechanism becomes complicated, resulting in an increase in cost and a problem in mass productivity. In addition, since it is necessary to drive a movable part on which the aperture switching plate and the objective lens are mounted, there arises a problem that the weight of the movable part increases and the servo performance of the actuator decreases.

In the case of using the liquid crystal filter of the second prior art, if the liquid crystal filter is integrated with the movable part, the movable part becomes large and a power supply mechanism for driving the liquid crystal filter is provided. Must be provided so as to be movable, and the mechanism becomes complicated, leading to an increase in cost,
There is also a problem in mass production. On the other hand, if the liquid crystal filter is provided separately from the movable portion, there is a problem that the optical axis of the lens and the center of the pattern of the liquid crystal filter are displaced when the objective lens is driven. Furthermore, since the liquid crystal material in the liquid crystal filter easily changes its material characteristics such as the refractive index depending on the temperature, there is a problem that desired performance cannot be satisfied due to a change in environmental conditions.

In the case of using the method using the wavelength filter film of the above-mentioned conventional example 3, the wavelength filter film needs to be formed as a part separate from the objective lens for patterning.
The number of components of the optical system increases, which is a problem in reducing the thickness and size of the optical pickup device. In addition, since a phase difference occurs between a portion where the wavelength filter film is present and a portion where the wavelength filter film is not present, it is necessary to coat the phase compensation film in accordance with the pattern of the wavelength filter film. In addition, mass productivity was extremely poor, and there was also a problem in terms of manufacturing cost.

The present invention solves the above-mentioned problems of the prior art, and provides an objective lens with a variable numerical aperture without substantially changing the basic configuration of an optical system, and a plurality of types of objective lenses having different thicknesses. It is an object of the present invention to provide an optical pickup device capable of recording and reproducing information on a standard optical storage medium.

Another object of the present invention is to achieve a reduction in thickness and size, a high reliability with little deterioration in optical performance, an excellent mass productivity, and a reduction in manufacturing cost. It is to provide an objective lens and an optical pickup device that can be used.

[0018]

According to the present invention, there is provided an objective lens comprising:
According to the wavelength of the incident light, a variable aperture film having a characteristic that the transmittance at the incident angle is different is integrally formed on the lens surface or in the vicinity thereof, and the variable aperture film has a predetermined property with respect to the incident light.
With characteristics that the transmittance changes greatly from the angle of incidence
In a transition region where the transmittance of the variable aperture film changes.
Correspondingly, an annular light-shielding band on or near the lens surface
It is characterized in that it is formed, thereby achieving the above object.

[0019]

Preferably, the variable aperture film has a characteristic of having a high transmittance with respect to incident light having a short wavelength irrespective of an incident angle, and an incident angle with respect to incident light having a long wavelength is larger than a predetermined angle. It is considered that the transmittance decreases sharply as the size increases.

Preferably, the variable aperture film has one
Alternatively, it is configured to include a plurality of dielectric films.

The optical pickup device of the present invention is an optical pickup device capable of recording and reproducing information on a plurality of types of optical recording media having different thicknesses. A light source that emits a plurality of types of light having different corresponding wavelengths; and the objective lens according to any one of the above, which condenses light from the light source onto the optical recording medium, thereby achieving the object described above. Is achieved.

The operation of the present invention will be described below.

According to the above arrangement, the variable aperture film having the characteristic that the transmittance at the incident angle is different depending on the wavelength of the incident light is integrally formed on or near the lens surface of the objective lens. Therefore, the angle of incidence on the variable aperture film is defined by the inclination of the objective lens surface, and the transmittance characteristics of the objective lens are determined.

Further, since the variable aperture film is formed integrally with the objective lens, there is no need to position the objective lens and the aperture, which is necessary when the objective lens and the aperture member are separately fixed. In addition, even if the objective lens shifts during tracking, the center of the objective lens will not be misaligned with the aperture.

By forming the variable aperture film with, for example, one or a plurality of dielectric films, a desired transmittance characteristic corresponding to the wavelength of the incident light can be obtained by the film design.

Further, when the variable aperture film has a characteristic that the transmittance of incident light changes greatly from a predetermined incident angle, a transient region where the transmittance of the variable aperture film changes at or near the surface of the objective lens. When the annular light-shielding band is formed corresponding to the above, even if the transmittance of the variable aperture film does not have a characteristic of sharply decreasing, the boundary is clarified by the light-shielding band and the transmission of the variable aperture film according to the incident angle. Switching of the rate can be performed reliably.

An optical pickup device emits a plurality of types of light having different wavelengths corresponding to a plurality of types of optical recording media having different thicknesses, and the aperture for condensing the light from the light source on the optical recording medium. With a configuration having an objective lens integrally formed with a variable film, information can be recorded / reproduced on / from a plurality of types of optical recording media having different thicknesses.

For example, the variable aperture film is made to have a characteristic that the transmittance is high regardless of the incident angle with respect to the incident light of a short wavelength, and the transmittance becomes steep when the incident angle becomes larger than a predetermined incident angle with respect to the incident light of a long wavelength. When the characteristics are lowered, the apertures corresponding to the two types of optical discs having different thicknesses are selected, and a desired condensed beam diameter can be obtained, so that the data of the two types of optical discs having different standards can be recorded and reproduced well. Becomes

[0030]

Embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIG. 1 shows Embodiment 1 of the objective lens of the present invention.

As shown in FIG. 1, the objective lens 3 of the first embodiment has a variable aperture film 2 having a characteristic that the transmittance at an incident angle is different depending on the wavelength of the incident light on or near the surface of the lens body 1. Are integrally formed. Therefore, the angle of incidence on the aperture variable film 2 is defined by the inclination of the surface of the lens body 1, and the transmittance characteristics of the objective lens 3 are determined.

The objective lens 3 is not formed by separately forming the lens main body 1 and the variable aperture film 2 and then positioning and bonding them together to form an integral variable film. 2 is continuously and integrally formed by coating or the like.

Accordingly, there is no need for a holder for integrating the lens main body 1 and the aperture variable film 2, and the objective lens and the aperture required when the objective lens and the aperture member are separately fixed. Positioning becomes unnecessary, and
Even if the objective lens shifts during tracking, the center of the objective lens will not be misaligned with the aperture.

Next, the characteristics of the objective lens 3 will be described in detail with reference to FIGS.

As shown in FIG. 2, this objective lens 3
It has the characteristic that the numerical aperture NA, which is the beam diameter that passes through the lens, varies according to the wavelength of the incident light.

For example, as shown in FIG. 2A, when the wavelength of the incident light is λ: A, the total incident light LA1 having the beam diameter φS is obtained.
Refracts the objective lens 3 and transmits it, and the transmitted light LA2 converges on a point F 'on the thin optical disk 4'.

On the other hand, as shown in FIG. 2B, when the wavelength of the incident light is λ: B, all the incident light LB1 within the beam diameter φT
Refracts the objective lens 3 and transmits it, and the transmitted light LB2 is condensed at a point F on the thick optical disk 4. On the other hand, the incident light LB3 having the beam diameter φS whose beam diameter φ is larger than T
Is reflected light L reflected by the variable aperture film of the objective lens 3.
B4.

That is, the numerical aperture of the objective lens 3 changes according to the wavelength λ of the incident light. Accordingly, the apertures φS and φT corresponding to the two types of optical disks 4 ′ and 4 having different thicknesses depending on the wavelength λ of the incident light are selected, and a desired condensed beam diameter can be obtained. Focus F ',
Since the light is focused on F, data on two types of optical discs having different standards can be recorded and reproduced well.

FIG. 3 shows characteristics obtained by integrally forming the objective lens 3 with the lens body 1 and the variable aperture film 2 in comparison with a conventional example.

The conventional example of the aperture fixing method shown in FIG. 3A has a configuration in which the aperture member 5 is provided in the fixing portion, and the lens body 1 and the aperture member 5 are separately fixed. If the main body 1 shifts during tracking, the center LC of the lens main body 1 will be out of alignment with the design center BC which is also the center of the aperture. In this case, the incident light L
Numeral NA is limited by the aperture φU of the aperture member 5, the incident light L5 passes through the lens body 1, the transmitted light L6 is reflected at the point F on the optical disk 4, and the reflected light L
7 passes through the lens body 1 and the transmitted light L8 returns to the photodetector, while the incident light L1 passes through the end of the lens body 1 and the transmitted light L2 is And the reflected light L3 passes through the other end of the lens body 1 and the transmitted light L4 proceeds to a region other than the opening φU of the opening member 5, so that the light indicated by the hatched region R is reflected by the opening member. 5
Vignetting occurs. For this reason, there is a problem that the amount of light returning to the photodetector changes depending on the shift amount d of the lens body 1.

On the other hand, the objective lens 3 of the first embodiment
Since the lens body 1 and the variable aperture film 2 are integrally formed, it is assumed that the lens body 1 shifts by a shift amount d with respect to the design center BC during tracking as shown in FIG. Also, since the lens body 1 and the variable aperture film 2 move together, the center LC of the lens body 1 always coincides with the center of the aperture. Therefore, for example, the numerical aperture NA of the incident light L0 is limited by the aperture variable film 2, and the incident light L0
10 passes through the lens body 1, the transmitted light L11 is reflected at a point F on the optical disk 4, the reflected light L12 passes through the lens body 1, and the transmitted light L13 returns to the photodetector. Vignetting unlike the conventional example of the aperture fixing method does not occur. Therefore, the amount of light returning to the photodetector can be kept constant without being changed by the shift amount d of the lens body 1. That is, since the servo signal and the information signal do not fluctuate according to the shift of the objective lens 3, a stable recording / reproducing operation can be performed.

As shown in FIG. 4, the variable aperture film 2
It can be composed of a dielectric film 6 having a multi-layer coating. Specifically, a fluoride 41 such as MgF is formed on the lens body 1.
And an oxide 42 such as SiO ₂ are alternately laminated. Since the dielectric film 6 with the multilayer coating can be formed only by uniformly coating the surface of the lens body 1 without special patterning, it is excellent in mass productivity. In addition, since it is not necessary to use a special material as described above, it is inexpensive and excellent in reliability.

Next, with reference to FIGS. 5 and 6, the optical characteristics when the above-mentioned dielectric film 6 is used as the variable aperture film 2 will be described below.

FIG. 5 shows the relationship between the incident angle (numerical aperture) of the dielectric film 6 and the transmittance. When the wavelength of the incident light is λ: A,
As shown by the curve S1, the transmittance is almost constant irrespective of the incident angle, and all the light incident on the objective lens is transmitted. On the other hand, when the wavelength of the incident light is λ: B, as shown by the curve S2. When the incident angle exceeds a predetermined value α, the transmittance suddenly decreases, and the transmittance becomes almost zero before the incident angle becomes β.

That is, as shown in FIG. 6, if the incident light has a wavelength λ: B, and if the incident angles corresponding to the two types of numerical aperture NA are α and β, the incident light whose incident angle is smaller than α The LB 61 transmits through the objective lens 1 and becomes transmitted light LB 62, whereas when the incident angle becomes β larger than α, the incident light LB 63 is reflected by the dielectric film 6 to become reflected light LB 64.

As described above, the numerical aperture NA of the objective lens can be changed by the wavelength λ of the incident light.

Here, it is preferable that the width of the incident angle until the transmittance is reduced to zero is as narrow as possible because the switching of the numerical aperture NA of the objective lens becomes sensitive. Further, the start of the decrease in the transmittance may be slightly before the incident angle α.

(Embodiment 2) FIG. 7 shows Embodiment 2 of the objective lens of the present invention. Objective lens 3 of Embodiment 2
Has an annular light-shielding band 7 smaller than the diameter φS at a position where the incident beam diameter on the lens body 1 is φT,
A multilayer dielectric film 6 as a variable aperture film is formed thereon. This annular light-shielding band 7 is, for example,
This is a diffusion surface formed on the surface of the lens body 1, and if an annular rough surface is formed on the surface of the lens mold, it can be formed integrally when the lens is molded. The light-shielding band 7 is formed of one or a plurality of dielectric films, and has an optical characteristic that transmits light when the wavelength of the incident light is λ: A and hardly transmits light when the wavelength of the incident light is λ: B. Is preferred. Note that the annular light-shielding band 7 may be formed on the opposite surface of the lens body 1, but in this case, it is formed so as to have a diameter smaller than φT in consideration of the refraction effect at the lens portion. There is a need.

(Embodiment 3) FIG. 8 shows Embodiment 3 of the objective lens of the present invention. In the third embodiment, the objective lens 3 and the annular light-shielding band 9 are formed as separate members and integrated. For example, as shown in FIG. 9, the annular light-shielding band 9 has a configuration in which an N region of a shielding plate made of resin, metal, or the like is hollowed out, and the annular light-shielding band 9 is supported by a support portion 8 ′ of the fixing member 8. A method of positioning the annular light-shielding band 9 using this fixing member 8 and fixing it to the lens body 1 or a method of forming a light-shielding band of metal or the like on a glass substrate can be adopted.

By providing such a light-shielding band, the following effects can be obtained. FIG. 10 shows the relationship between the incident angle and the transmittance when the light-shielding band is provided, as compared with the transmittance characteristic when there is no light-shielding band 7 shown in FIG. In FIG. 10, when the wavelength of the incident light is λ: A, the transmittance becomes zero in the range indicated by W corresponding to the region of the light-shielding band 7 as shown by the curve S1 ′. In the range excluding, the transmittance is almost constant irrespective of the incident angle, and all the light incident on the objective lens is transmitted. On the other hand, in the case of the wavelength λ: B of the incident light, the incident angle is When the value exceeds the predetermined value α and enters the region of the light-shielding band 7, the transmittance suddenly decreases, and the light-shielding band 7
The transmittance in the range indicated by W corresponding to the region of is zero.
The transmittance at the outer portion beyond the area of the light-shielding band 7 is not zero but is a sufficiently small value, and the transmittance becomes almost zero before the incident angle becomes β. In other words, even if the transmittance of the dielectric film itself is reduced slowly by providing the light-shielding band 7, the transmittance characteristic is equivalent to that when the incident angle is larger than α, the transmittance is sharply reduced. Is obtained,
Switching of the numerical aperture NA becomes sensitive.

(Embodiment 4) FIG. 11 shows Embodiment 4 which is a configuration example of an optical pickup device equipped with the objective lens 3 of the present invention. For convenience of explanation, the components from the hologram laser units 13 and 14 to the collimator lens 11 are shown in a top view, and the components from the rising mirror 10 to the disks 4 and 4 'are shown in a side view. This optical pickup device
Hologram laser units 13 and 14 having light sources for emitting a plurality of types of light having different wavelengths corresponding to a plurality of types of optical recording media 4 and 4 'having different thicknesses, and light from these light sources being transmitted to the optical recording media 4, 4' And the objective lens 3 of the present invention that converges light on the top, and enables recording and reproduction of information with respect to a plurality of types of optical recording media 4 and 4 ′ having different thicknesses.

The optical pickup device will be described in more detail according to the operation. The light LA11 emitted from the hologram laser unit 13 having a short wavelength (λ: A) is reflected by the beam splitter 12, and the reflected light LA12 passes through the collimator lens 11. Is transmitted and converted into a parallel light LA13,
The parallel light LA13 is reflected by the rising mirror 10, and the reflected light LA14 is transmitted through the aperture member 15 to a predetermined beam diameter φS.
After that, the light is focused by the objective lens 3 onto a point F ′ on the thin optical disk 4 ′. The reflected light from the thin optical disk 4 'passes through the reverse of the outward path and enters the photodetector in the unit 13.

On the other hand, the light LB11 emitted from the hologram laser unit 14 having a long wavelength (λ: B) passes through the beam splitter 12, and the transmitted light LB12 is converted into a parallel light LB13 by the collimator lens 11, and this parallel light LB13
Is reflected by the rising mirror 10, and the reflected light LB 14 is limited to a predetermined beam diameter φT by the objective lens 3 of the present invention, and then condensed on a point F on the thick optical disk 4. The reflected light from the thick optical disc 4 passes through the opposite
Incident on the photodetector inside.

According to this pickup device, since the objective lens 3 capable of selectively changing the numerical aperture NA depending on the wavelength λ of the incident light is mounted, the pickup device can handle two types of optical discs having different thicknesses. Good recording and reproduction can be performed using light sources of different wavelengths λ. Further, since no new optical components or movable mechanisms other than the objective lens 3 are required, the entire apparatus can be simplified and the size can be reduced.

In the fourth embodiment, the hologram laser units 13 and 14 in which the light source and the photodetector are integrated are employed in order to simplify the optical system. It may be an optical system.

[0056]

As described above, in the objective lens of the present invention, the aperture variable film having the characteristic that the transmittance at the incident angle differs according to the wavelength of the incident light is integrally formed on the surface of the lens body or in the vicinity thereof. With this configuration, the angle of incidence on the variable aperture film is defined by the inclination of the surface of the objective lens, and the transmittance characteristics of the objective lens are determined. Therefore, it is possible to provide an objective lens having a variable numerical aperture without substantially changing the basic configuration of the optical system. Further, the optical pickup device equipped with this objective lens can accurately record and reproduce information on optical storage media of a plurality of types having different thicknesses.

The variable aperture film does not require special patterning, and can be formed, for example, only by coating one or a plurality of dielectric films on the lens body. Therefore, the variable aperture film is excellent in mass productivity. Since the material of the film is also a general material, the manufacturing cost can be reduced. In addition, the objective lens and the optical pickup device can be made thinner and smaller.

In the objective lens according to the present invention, since the variable aperture film and the lens body are integrally formed, the objective lens and the aperture required when the objective lens and the aperture member are separately fixed are employed. Positioning is not required, and
Even if the objective lens shifts during tracking, the center of the objective lens does not deviate from the center of the aperture, so that the optical performance is hardly reduced and the reliability can be increased.

Further, in the case where the variable aperture film has a characteristic that the transmittance changes greatly with respect to incident light from a predetermined incident angle, a transient region where the transmittance of the variable aperture film changes on or near the surface of the objective lens. In the case where the annular light-shielding band is formed so as to correspond to the above, even if the transmittance of the variable aperture film does not have a characteristic of decreasing steeply, the boundary is clarified by the light-shielding band and the aperture according to the incident angle is changed. Switching of the transmittance of the variable film can be reliably performed. Therefore, in the optical pickup device equipped with this objective lens, it is possible to more accurately record and reproduce information on optical storage media of a plurality of types having different thicknesses. In addition, this shading zone
Since the objective lens is formed directly at the time of molding processing, a special lens mold is not required, and it can be easily formed without performing positioning and bonding work. Therefore, it is excellent in terms of mass productivity and reliability.

[Brief description of the drawings]

FIG. 1 is a diagram showing Embodiment 1 of an objective lens of the present invention.

FIG. 2 is a diagram illustrating characteristics relating to a wavelength and a numerical aperture of incident light in the objective lens of the present invention.

FIG. 3 is a diagram showing characteristics when an objective lens of the present invention shifts during tracking in comparison with a conventional example.

FIG. 4 is a diagram showing an example in which the variable aperture film of the objective lens of the present invention is composed of a plurality of dielectric films.

FIG. 5 is a graph showing a relationship between an incident angle and a transmittance of the variable aperture film according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a characteristic that incident light having a specific wavelength transmits or reflects through an aperture variable film depending on an incident angle.

FIG. 7 is a diagram showing Embodiment 2 of the objective lens of the present invention.

FIG. 8 is a diagram showing Embodiment 3 of the objective lens of the present invention.

FIG. 9 is a diagram illustrating an example of a light-shielding band used in Embodiment 3 of the objective lens of the present invention.

FIG. 10 is a graph showing a relationship between an incident angle and a transmittance of a variable aperture film provided with a light blocking zone according to Embodiments 2 and 3 of the present invention.

FIG. 11 is a diagram illustrating a configuration of an optical pickup device equipped with the objective lens of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens main body 2 Aperture variable film 3 Objective lens 4 Optical storage medium 5, 15 Opening member 6 Dielectric film 7, 9 Shielding band 8 Fixing member 10 Start-up mirror 11 Collimator lens 12 Beam splitter 13, 14 Hologram laser unit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-208275 (JP, A) JP-A-10-162409 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/12-7/135 G02B 13/00-13/18

Claims (4)

(57) [Claims] 1. A depending on the wavelength of the incident light, are integrally formed on the aperture-adjustment film lens or near the surface with transmittance different characteristics at the incident angle, opening the variable film is given to the incident light Transmittance from incident angle
Has a characteristic that greatly changes the
In response to the transient region where the transmittance of the changing film changes, the lens
Features an annular light-shielding band formed on or near the surface
And the objective lens. 2. The variable aperture film has a high transmittance with respect to incident light of a short wavelength regardless of the incident angle, and
Claims incident angle to the incident light of longer wavelength and transmittance becomes larger than a predetermined angle is a characteristic to decrease abruptly
2. The objective lens according to 1 . Wherein the aperture-adjustment film, one or more of a dielectric film according to claim 1 or 2, wherein the objective lens. 4. An optical pickup device capable of recording and reproducing information on a plurality of types of optical recording media having different thicknesses, wherein the plurality of types have different wavelengths corresponding to the plurality of types of optical recording media having different thicknesses. A light source that emits different types of light, and light from the light source is collected on the optical recording medium.
An optical pickup device comprising the objective lens according to claim 3 .