JP2006260743A - Optical unit, mirror and optical pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately conduct recording and/or reproducing of information for three kinds of optical recording media and to reduce the size of the optical pickup apparatus. <P>SOLUTION: An objective optical unit 6 for an optical pickup apparatus 1 is to conduct recording and or reproducing of information onto or from the first to third optical recording media by applying the first to third light beams emitted from the first to third light sources L1 to L3. The optical unit comprises a mirror section 7 having a dichroic mirror layer 71 including reflecting surfaces 71a and 70a on both surfaces and an objective lens 8 including a phase structure on the optical surface of the objective lens. The mirror section 7 reflects the first to second light beams by the reflection surface 71a and guides to the objective lens 8. The reflecting surface 70a reflects the third light beams, converts them to diverging light beams and guides them to the objective lens 8. The objective lens 8 corrects the spherical aberration of the first and the second light beams by the phase structure and focuses the first light beams onto a BD10, the second beams onto a DVD11 and the third beams onto a CD. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mirror and an optical unit that are disposed to face an optical recording medium, and an optical pickup device including the optical unit.

  2. Description of the Related Art Conventionally, there is an optical pickup device as a device for recording and reproducing information on an optical recording medium such as MO, CD, and DVD. This optical pickup device is provided with an optical element such as an objective lens for condensing light emitted from a semiconductor laser light source on an information recording surface of an optical recording medium.

In recent years, as such an optical pickup device, there is one in which an optical path is refracted in front of an objective lens by a mirror (for example, see Patent Document 1). According to the optical pickup device, amount that the linear distance from the light source to the optical recording medium becomes shorter, it is possible to miniaturize the apparatus.
JP 2002-40323 JP

  However, the optical pickup device disclosed in Patent Document 1 records and reproduces information with respect to two types of optical recording media. Therefore, even when simply applying the technique of this optical pickup device, while the optical pickup device is miniaturized, it is impossible to enable accurate recording and reproduction of information with respect to three kinds of optical recording medium.

  On the other hand, it occurs as another optical pickup device performs two kinds of recording and reproducing information on the same optical recording medium, by an objective lens with a diffractive structure, a diffraction effect for each light flux of the two different wavelengths In addition, there is known a technique for concentrating incident light with corrected spherical aberration on the information recording surface of each optical recording medium. However, this optical pickup device technology is applied to three types of optical recording media: CDs, DVDs, and BDs (Blu-ray Discs) or HD DVDs (High Definition DVDs), which are higher in density than DVDs. When recording and reproducing information, the wavelength used for BD and HDDVD has a relationship that is approximately an integral multiple of the wavelength used for CD. If it is generated, the light utilization efficiency is greatly reduced, and it becomes difficult to accurately record and reproduce information.

  The first object of the present invention is to enable accurate recording and / or reproducing information, a mirror of the optical pickup apparatus can be miniaturized, and an optical unit, an optical pickup apparatus including the optical unit Is to provide. The second object of the present invention is to provide a mirror, an optical unit, and an optical pickup device including the optical unit that can increase the light use efficiency.

The invention according to claim 1
The first optical recording medium, the second optical recording medium, and the third light are emitted from the light source using the first light flux, the second light flux, and the third light flux having wavelengths λ1, λ2, and λ3 (where λ1 <λ2 <λ3). an optical unit for an optical pickup apparatus for recording and / or reproducing information onto a recording medium,
An objective lens having a phase structure on at least one optical surface;
Of the first to third light fluxes, a first reflection surface that reflects two kinds of light fluxes and transmits the remaining one kind of light flux, and reflects the remaining one kind of light flux that has passed through the first reflection face. A second reflection surface that converts the light into divergent light, and a mirror unit that guides the reflected first to third light fluxes to the objective lens,
The objective lens is
The spherical aberration of the two kinds of light beams is corrected by the phase structure, the first light flux on the information recording surface of the first optical recording medium, the second light flux on the information recording surface of the second optical recording medium , characterized in that said third, respectively condensing the light beam on the information recording surface of the third optical recording medium.

  According to the first aspect of the present invention, the two types of light beams are condensed on the information recording surfaces of different optical recording media in a state where the spherical aberration is corrected by the phase structure. It is possible to accurately record and / or reproduce information. Further, the remaining one light flux is converted into divergent light while being reflected by the second reflecting surface of the mirror, because it is focused on the optical recording medium, different from the two kinds of optical recording medium the light it is possible to enable accurate recording and / or reproducing information on the recording medium. Accordingly, it is possible to accurately record and / or reproduce information on the three types of optical recording media.

  Further, since the guided to the object lens mirror is reflected first to third light fluxes respectively, amount that can shorten the straight line distance to the optical recording medium from the light source, it is possible to miniaturize the optical pickup device .

  Here, the phase structure is a general term for a structure having a plurality of steps in the optical axis direction and adding an optical path difference (phase difference) to the incident light flux. The optical path difference added to the incident light flux by this step may be an integer multiple of the wavelength of the incident light flux or a non-integer multiple. As a specific example of such a phase structure, said stepped diffractive structure and arranged with periodic interval in the direction perpendicular to the optical axis is aperiodic arranged at a distance optical path difference providing structure (phase difference providing structure Also called).

  More specifically, the diffractive structure is such that steps are arranged at periodic intervals in the direction perpendicular to the optical axis, and the pitch (diffraction power) and depth (blazed wavelength) are set. A step structure in which the diffraction efficiency of a specific order of diffracted light is higher than that of other orders of diffracted light with respect to a specific wavelength light.

The invention described in claim 2 is the optical unit according to claim 1,
The mirror part reflects the first light flux and the second light flux by the first reflection surface, and reflects the third light flux by the second reflection surface.

  According to the second aspect of the present invention, the first light beam and the second light beam, which have a shorter wavelength than the third light beam, are not divergent light, so that the first light beam and the second light beam are divergent light. The objective lens can be easily designed. Therefore, the cost of the optical unit can be reduced.

The invention described in claim 3 is the optical unit according to claim 2,
The wavelengths λ1, λ2, and λ3 are
1.9 <λ3 / λ1 <2.1, and is characterized by satisfying 1.5 <λ2 / λ1 <1.7.

  Here, in general, when one of the two wavelengths is an integral multiple of the other, it is difficult to correct the spherical aberration by the phase structure.

  According to the third aspect of the present invention, since the ratio of the wavelengths λ1 and λ3 is approximately 2, and the ratio of the wavelengths λ1 and λ2 is not an integer, the phase structure for correcting the spherical aberration of the light beams having the wavelengths λ1 and λ3 As compared with the above, the phase structure for correcting the spherical aberration of the light beams having the wavelengths λ1 and λ2 can be easily designed. Therefore, the cost of the optical unit can be reduced.

  Further, even in the case of using two kinds of light flux of the first light flux and the third light flux having a substantially integral multiple of the wavelength relationship, for converting only the third light flux to the divergent light by the second reflecting surface, these two It is possible to reduce the influence of the diffractive action by the phase structure on the luminous flux and to improve the light utilization efficiency.

  Examples of combinations of wavelengths that satisfy the above inequality formula include combinations of a wavelength for CD, a wavelength for DVD, and a wavelength for BD or HDDVD.

The invention according to claim 4 is the optical unit according to claim 2 or 3,
The second reflecting surface comprises a central region intersecting with the optical axis, and an outer peripheral area located on the outer peripheral side of the central region,
Of the third light beam incident on the second reflecting surface, only the light beam incident on the central region is condensed on the third optical recording medium by the objective lens.

  According to the fourth aspect of the present invention, of the third light flux incident on the second reflecting surface, only the light flux incident on the central area is condensed on the third optical recording medium by the objective lens and incident on the outer peripheral area. Is not condensed on the third optical recording medium, the aperture can be limited by the size of the central region. Therefore, the optical pickup device can be reduced in size as compared with the case where the aperture members are disposed before and after the mirror portion in order to limit the opening.

  Further, since the spot shape on the third optical recording medium can be deformed by the shape of the center region, the spot shape can be made circular even if the second reflecting surface is non-rotationally symmetric with respect to the optical axis. it can. In addition, the optical pickup device can be reduced in size as compared with the case where optical elements for adjusting the cross-sectional shape of the third light flux are arranged before and after the mirror portion.

  The third light flux incident on the peripheral region may be as it is absorbed in the outer peripheral region, it may be by passing through the outer peripheral region, reflected by the outer peripheral region, the spot of the third optical recording medium it may be a flare component which does not contribute to the formation.

The invention according to claim 5 is the optical unit according to claim 4,
The second reflective surface, characterized in that the optical axis is a rotationally asymmetric curved surface.

  Here, generally, when the reflecting surface is rotationally asymmetric with respect to the optical axis, the cross-sectional shape of the incident light to the reflective surface may be round to oval cross-sectional shape of the reflected light In addition, even if the sectional shape of the incident light is elliptical, the sectional shape of the reflected light can be circular.

  According to the fifth aspect of the present invention, since the second reflecting surface is a rotationally asymmetric curved surface with respect to the optical axis, also the incident light to the second reflection surface is an elliptical shape, the cross-sectional shape of the reflected light Can be circular. Accordingly, it is possible to accurately record and reproduce information using the third optical recording medium.

The invention according to claim 6 is the optical unit according to claim 4,
The second reflecting surface is a non-rotationally symmetric curved surface with respect to the optical axis,
The central region is elliptical.

  According to the sixth aspect of the present invention, the second reflecting surface is a rotational asymmetrical curved surface with respect to the optical axis, since the center region is elliptical, light incident on the second reflecting surface is a oval However, the cross-sectional shape of the reflected light can be circular depending on the orientation of the ellipse. Accordingly, it is possible to accurately record and reproduce information using the third optical recording medium.

The invention according to claim 7 is the optical unit according to claim 6,
The second reflecting surface is intended to reflect the remaining one light flux as divergent angle within the predetermined plane is maximum including the optical axis between said mirror portion and the objective lens,
The central region may be an ellipse having a major axis in a direction perpendicular to the predetermined plane.

  According to the invention of claim 7, wherein, the second reflecting surface is intended to reflect the remaining one light flux as divergent angle within the predetermined plane is maximum, the central region in the vertical direction of the predetermined plane Since it is an ellipse having a long axis, the cross section of the reflected light can be surely made circular.

Invention of Claim 8 is an optical unit as described in any one of Claims 1-7,
The objective lens is a single lens.

  According to the eighth aspect of the present invention, since the objective lens is a single lens, the optical pickup device can be downsized as compared with the case where the objective lens is a lens unit.

The invention according to claim 9 is the optical unit according to any one of claims 1 to 8,
Wherein the phase structure is a diffractive structure,
The diffractive structure relates to the aforementioned first through third light flux, characterized in that they exhibit a maximum diffraction efficiency at the same diffraction order.

  According to the invention of claim 9, wherein the diffractive structure exhibits a maximum diffraction efficiency at the same diffraction orders relates first to the third light flux, the results which occur as the strength of the long and short are directly diffraction effect of wavelength? 1 to? 3, In the first to third light beams, the third light beam is most strongly diffracted. Therefore, when the light beam is converted into divergent light by the second reflection surface is the third light flux, the third light flux and the second reflecting surface of the mirror, the spherical aberration in two steps by the diffractive structure of the objective lens Will be corrected. Therefore, the minute part of the function to correct spherical aberration is shared by the diffractive structure, it is possible to reduce the divergence degree of the third light flux by the second reflecting surface, of the optical pickup device with respect to the third optical recording medium Focusing performance and tracking performance can be improved.

The invention described in claim 10 is the optical unit according to claim 9,
The diffractive structure relates to the aforementioned first through third light flux, characterized in that they exhibit a maximum diffraction efficiency in the first order diffracted light.

Here, generally, when light beams of a plurality of wavelengths exhibit the maximum diffraction efficiency at the same diffraction order, the diffraction efficiency of each light beam increases as the diffraction order decreases.
According to the invention of claim 10, since the diffractive structure exhibits the maximum diffraction efficiency with the first-order diffracted light with respect to the first to third light beams, the diffraction efficiency of the first to third light beams can be increased.

The invention according to claim 11 is the optical unit according to claim 3,
The phase structure is
Transmitting the incident first light flux and the third light flux;
Regarding the second light flux incident, characterized by indicating the maximum diffraction efficiency in the first order diffracted light.

According to claim 11 the invention described, because the first light flux and the phase structure of the third light flux is incident to directly passes, maintaining the light use efficiency at a high level for these first and third light fluxes It is possible to record or reproduce information accurately.
In addition, with respect to the incident second light beam, the phase structure exhibits the maximum diffraction efficiency with the first-order diffracted light, so that aberration can be corrected with respect to the second light beam to enable accurate information recording or reproduction. .

  The phase structure preferably transmits the incident first and third light beams without diffracting them.

The invention of claim 12, wherein, in the optical unit according to any one of claims 1 to 11,
Characterized in that it comprises an actuator for moving integrally with the objective lens and the mirror unit.

  According to the invention described in claim 12, since the actuator moves the objective lens and the mirror unit integrally, coma aberration caused by the movement of the objective lens compared to the case where the objective lens and the mirror unit move separately. Can be reduced. Therefore, it is possible to improve the focusing performance and tracking the performance of the optical pickup device.

Invention of Claim 13 is an optical unit as described in any one of Claims 1-12,
A protective layer thickness t ₁ of the first optical recording medium;
A protective layer thickness t ₂ of the second optical recording medium;
The protective layer thickness t ₃ of the third optical recording medium is
It is characterized by satisfying t ₁ <t ₂ <t ₃ .

  According to the invention of the thirteenth aspect, the same effect as that of the invention according to any one of the first to twelfth aspects can be obtained.

Invention of Claim 14 is an optical unit as described in any one of Claims 1-13,
The first optical recording medium is BD,
The second optical recording medium is a DVD,
The third optical recording medium is a CD.

  According to the invention of claim 14, the same effect as that of any one of claims 1 to 13 can be obtained.

The invention according to claim 15 is the optical unit according to any one of claims 1 to 14,
The objective lens corrects spherical aberration caused by a difference in protective layer thickness of two types of optical recording media corresponding to the two types of light beams among the first to third optical recording media by the phase structure. Features.

  According to the invention of claim 15, wherein, the objective lens is corrected by the phase structure for the spherical aberration caused by the difference of the protective layer thickness of the optical recording medium corresponding to the two kinds of light beams, a more accurate recording of information and / Or reproduction can be made possible.

The invention according to claim 16 is an optical pickup device,
The optical unit according to any one of claims 1 to 15,
A first light source that emits the first luminous flux;
A second light source that emits the second light flux;
And a third light source that emits the third light flux.

  According to the invention of the sixteenth aspect, the same effect as that of the invention according to any one of the first to fifteenth aspects can be obtained.

The invention according to claim 17 is the optical pickup device according to claim 16,
The optical axis of the remaining one type of light flux before being incident on the mirror portion is offset with respect to the optical axes of the two kinds of light fluxes.

  Here, the reflection position on the second reflection surface is offset from the reflection position of the light beam on the first reflection surface by at least the thickness of the mirror portion.

  According to the seventeenth aspect of the present invention, since the optical axis of the one kind of light beam is offset with respect to the optical axis of the two kinds of light flux before being incident on the mirror part, the light is emitted from the mirror part. Later, the optical axis of the one kind of light flux can be made to coincide with the optical axis of the two kinds of light flux. Accordingly, it is possible to accurately record and reproduce information using the first to third optical recording media.

The invention according to claim 18
A mirror that selectively transmits or reflects the first light beam, the second light beam, and the third light beam having wavelengths λ1, λ2, and λ3 (where λ1 <λ2 <λ3);
A first reflecting surface that reflects two types of light beams among the first to third light beams incident thereon and transmits the remaining one type of light beams;
And a second reflecting surface that reflects the remaining one type of light beam that has passed through the first reflecting surface to convert it into divergent light.

  According to the invention of claim 18, for example, it is used as an optical element of an optical pickup device that records and / or reproduces information on the first to third optical recording media using the first to third light beams, When an objective lens having a phase structure is arranged on the optical recording medium side with respect to the mirror, the two kinds of light beams are condensed on the information recording surfaces of different optical recording media in a state where spherical aberration is corrected by the phase structure. Therefore, it is possible to accurately record and / or reproduce information on two types of optical recording media. The remaining one type of light beam is reflected by the second reflecting surface of the mirror, converted into divergent light, and then condensed on the optical recording medium. Therefore, the optical recording is different from the two types of optical recording media. it is possible to enable accurate recording and / or reproducing information for the media. Accordingly, it is possible to accurately record and / or reproduce information on the three types of optical recording media.

  Further, since the mirror is guided to the object lens of the first to third light flux reflected respectively, amount that can shorten the straight line distance to the optical recording medium from the light source, the optical pickup apparatus can be miniaturized.

The invention according to claim 19 is the mirror according to claim 18,
The wavelengths λ1, λ2, and λ3 are
1.9 <λ3 / λ1 <2.1, and is characterized by satisfying 1.5 <λ2 / λ1 <1.7.

  According to the nineteenth aspect of the invention, since the ratio between the wavelengths λ1 and λ3 is approximately 2, and the ratio between the wavelengths λ1 and λ2 is not an integer, the phase structure for correcting the spherical aberration of the light fluxes with the wavelengths λ1 and λ3 As compared with the above, the phase structure for correcting the spherical aberration of the light beams having the wavelengths λ1 and λ2 can be easily designed. Therefore, it is possible to cost reduction of the optical unit with the mirror.

  Further, even in the case of using two kinds of light flux of the first light flux and the third light flux having a substantially integral multiple of the wavelength relationship, by these two types of one the remaining one light flux of the light beam, the Since only the light beam is converted into divergent light by the second reflecting surface, the influence of the diffractive action by the phase structure on these two types of light beam can be reduced, and the light utilization efficiency can be increased.

The invention according to claim 20 is the mirror according to claim 18 or 19, wherein
The second reflective surface, characterized in that the optical axis is a rotationally asymmetric curved surface.

  According to the invention of claim 20 wherein, the second reflecting surface is a rotationally asymmetric curved surface with respect to the optical axis, also the incident light to the second reflection surface is an elliptical shape, the cross-sectional shape of the reflected light Can be circular. Accordingly, it is possible to accurately record and reproduce information using the optical recording medium corresponding to the remaining one type of light beam.

The invention according to claim 21 is the mirror according to claim 18 or 19,
The first reflecting surface and the second reflecting surface reflect the incident first to third light fluxes and guide them to a subsequent optical element,
The second reflecting surface is a non-rotationally symmetric curved surface with respect to the optical axis,
A central region intersecting with the optical axis,
An outer peripheral region located on the outer peripheral side of the central region,
Of the remaining one of the light beam incident on the second reflecting surface to guide only light flux incident on the central region on the optical elements of the subsequent stage,
The central region is
It is elliptical.

  According to the twenty-first aspect, of the remaining one type of light beam incident on the second reflecting surface, only the light beam incident on the central region is guided to the optical element at the subsequent stage, and the light beam incident on the outer peripheral region is guided. It does not, can be an aperture restriction by the size of the central area. Therefore, the optical pickup device can be reduced in size as compared with the case where the aperture members are disposed before and after the mirror to limit the aperture.

  In addition, since the spot shape on the optical recording medium corresponding to the remaining one type of light beam can be deformed by the shape of the central region, even if the second reflecting surface is non-rotationally symmetric with respect to the optical axis, Can be rounded. In addition, the optical pickup device can be downsized as compared with the case where optical elements for adjusting the cross-sectional shape of the remaining one type of light beam are arranged before and after the mirror.

  In addition, the second reflecting surface is a non-rotationally symmetric curved surface with respect to the optical axis, and the central region is elliptical. Therefore, even if the incident light to the second reflecting surface is elliptical, it is reflected by the direction of the ellipse. The cross-sectional shape of the light can be circular. Therefore, it is possible to accurately record / reproduce information using the remaining one type of optical recording medium.

The latter stage means the opposite side to the light source.
Further, the light beam incident on the peripheral region may be as it is absorbed in the outer peripheral region, may be by passing through the outer peripheral region, is guided in a portion other than the optical elements of the subsequent stage is reflected by the outer peripheral region It's also good.

The invention according to claim 22
First, second, and third light beams having wavelengths λ1, λ2, and λ3 (1.9 <λ3 / λ1 <2.1) emitted from the light source are used for the first optical recording medium and the second light. recording medium, an optical unit for an optical pickup apparatus for recording and / or reproducing information for the third optical recording medium,
An objective lens having a phase structure on at least one optical surface;
A first reflecting surface that transmits one of the first light beam and the third light beam, and reflects two types of light beams, the other light beam and the second light beam, and the first reflecting surface. A second reflection surface that reflects the one light beam, and a mirror unit that guides the reflected first to third light beams to the objective lens,
The second reflecting surface converts the incident one light beam into a light beam whose spherical aberration can be corrected by the objective lens and guides it to the objective lens,
The objective lens is
The spherical aberration of the two kinds of light beams reflected by the first reflecting surface is corrected by the phase structure, the first light flux on the information recording surface of the first optical recording medium, the said second light flux second on the information recording surface of the optical recording medium, characterized by said third respectively condensing the light beam on the information recording surface of the third optical recording medium.

  According to the invention of claim 22, since the two kinds of light beams are condensed on the information recording surfaces of different optical recording media in a state where the spherical aberration is corrected by the phase structure, these two kinds of optical recording media are used. it is possible to enable accurate recording and / or reproducing of information for. Further, while the light flux of the one is reflected by the second reflecting surface of the mirror, after the spherical aberration is converted to a light beam allows correction in the objective lens, because it is focused on the optical recording medium, the two It is possible to accurately record and / or reproduce information on an optical recording medium different from the optical recording medium. Accordingly, it is possible to accurately record and / or reproduce information on the three types of optical recording media.

  Further, since the mirror portion reflects the first to third light beams and guides them to the objective lens, the optical pickup device can be miniaturized because the linear distance from the light source to the optical recording medium can be shortened. .

  Further, even when two types of light beams, ie, a first light beam and a third light beam having a wavelength relationship of substantially an integral multiple are used, only one of the light beams is second reflected into a light beam whose spherical aberration can be corrected by the objective lens. Since the surface conversion is performed, the influence of the diffraction effect by the phase structure on these two types of light beams can be reduced, and the light utilization efficiency can be increased.

The invention according to claim 23 is the optical unit according to claim 22,
The wavelengths λ1 and λ2 are
1.5 <λ2 / λ1 <1.7 is satisfied.

  According to the twenty-third aspect, since the ratio of the wavelengths λ1 and λ3 is approximately 2, and the ratio of the wavelengths λ1 and λ2 is not an integer, the phase structure for correcting the spherical aberration of the light beams having the wavelengths λ1 and λ3. As compared with the above, the phase structure for correcting the spherical aberration of the light beams having the wavelengths λ1 and λ2 can be easily designed. Therefore, the cost of the optical unit can be reduced.

The invention according to claim 24 is the optical unit according to claim 22 or 23, wherein
Characterized in that it comprises an actuator for moving integrally with the objective lens and the mirror unit.

  According to the invention of claim 24, since the actuator moves the objective lens and the mirror unit integrally, coma aberration caused by the movement of the objective lens compared to the case where the objective lens and the mirror unit move separately. Can be reduced. Therefore, focusing performance and tracking performance of the optical pickup device can be improved.

The invention according to claim 25 is the optical unit according to any one of claims 22 to 24,
A protective layer thickness t ₁ of the first optical recording medium;
A protective layer thickness t ₂ of the second optical recording medium;
The protective layer thickness t ₃ of the third optical recording medium is
It is characterized by satisfying t ₁ <t ₂ <t ₃ .

  According to invention of Claim 25, the effect similar to the invention as described in any one of Claims 22-24 can be acquired.

The invention according to claim 26 is the optical unit according to any one of claims 22 to 25,
The first optical recording medium is BD,
The second optical recording medium is a DVD,
The third optical recording medium is a CD.

  According to the twenty-sixth aspect of the present invention, the same effects as those of the twenty-second aspect of the present invention can be obtained.

The invention according to claim 27 is the optical unit according to any one of claims 22 to 26, wherein:
The objective lens corrects spherical aberration caused by a difference in protective layer thickness of two types of optical recording media corresponding to the two types of light beams among the first to third optical recording media by the phase structure. Features.

  According to the twenty-seventh aspect of the invention, since the objective lens corrects the spherical aberration caused by the difference in the protective layer thickness of the optical recording medium corresponding to the two kinds of light beams by the phase structure, more accurate information recording and / or Or reproduction can be made possible.

The invention according to claim 28 provides
Of the at least two kinds of light beams emitted from the light source, performs recording and / or reproducing of information for the first optical recording medium with a light beam relatively short first wavelength, a relatively long first 2 wavelength (where 1.9 <second wavelength / first wavelength <2.1) a second recording information on an optical recording medium and / or an optical pickup apparatus for reproducing using a light beam An optical unit for
An objective lens;
A first reflecting surface that transmits one of the first wavelength and the second wavelength and reflects the other; and the one that passes through the first reflecting surface. And a mirror part for guiding the reflected light beam of the first wavelength and the light beam of the second wavelength to the objective lens,
The mirror unit converts the light beam having the first wavelength or the light beam having the second wavelength into a light beam whose spherical aberration can be corrected by the objective lens, and guides the light to the objective lens.
The objective lens is
The light beam having the first wavelength is condensed on the information recording surface of the first optical recording medium, and the light beam having the second wavelength is condensed on the information recording surface of the second optical recording medium. .

  According to the invention of claim 28, wherein, after being converted into the light flux spherical aberration is correctable by the objective lens by the light flux and the light flux of the second wavelength of the first wavelength mirror unit, a corresponding optical recording medium Since the light is condensed or the light is condensed on the information recording surface of the corresponding optical recording medium without being subjected to the same conversion depending on the mirror unit, the information can be accurately recorded and / or recorded on the two types of optical recording media. Playback can be made possible.

  Further, since the mirror part reflects the light beams of the first and second wavelengths and guides them to the objective lens, the optical pickup device can be miniaturized by the amount that the linear distance from the light source to the optical recording medium can be shortened. be able to.

  In addition, even when two types of light beams, a first wavelength light beam and a second wavelength light beam having a substantially integer multiple wavelength relationship, are used, spherical aberration can be corrected with the objective lens for only one light beam. Therefore, it is possible to reduce the influence of the diffractive action due to the phase structure on these two types of light beams and to increase the light utilization efficiency.

The invention according to claim 29 is the optical unit according to claim 28,
Characterized in that it comprises an actuator for moving integrally with the objective lens and the mirror unit.

  According to the twenty-ninth aspect of the present invention, since the actuator moves the objective lens and the mirror unit integrally, coma aberration caused by the movement of the objective lens compared to the case where the objective lens and the mirror unit move separately. Can be reduced. Therefore, focusing performance and tracking performance of the optical pickup device can be improved.

The invention according to claim 30 is the optical unit according to claim 28 or 29,
The second reflective surface, characterized in that the optical axis is a rotationally asymmetric curved surface.

  According to the invention of claim 30 wherein, the second reflecting surface is a rotationally asymmetric curved surface with respect to the optical axis, also the incident light to the second reflection surface is an elliptical shape, the cross-sectional shape of the reflected light Can be circular. Accordingly, it is possible to accurately record and reproduce information using the optical recording medium corresponding to the one light beam.

The invention according to claim 31 is the optical unit according to any one of claims 28 to 30, wherein
The second reflecting surface is
A central region intersecting the optical axis, and an outer peripheral region located on the outer peripheral side of the central region,
The one light flux is reflected so that a divergence angle within a predetermined plane including the optical axis between the mirror unit and the objective lens is maximized,
Of the one light beam incident on the second reflecting surface, only the light beam incident on the center region is condensed on the optical recording medium corresponding to the light beam by the objective lens,
The central region may be an ellipse having a major axis in a direction perpendicular to the predetermined plane.

  According to the invention of claim 31, of the one light beam incident on the second reflecting surface, only the light beam incident on the central region is condensed on the optical recording medium corresponding to the light beam by the objective lens, and the outer peripheral region. Since the light beam incident on the optical recording medium is not condensed on the optical recording medium, the aperture can be limited by the size of the central region. Therefore, the optical pickup device can be reduced in size as compared with the case where the aperture members are disposed before and after the mirror portion in order to limit the opening.

  In addition, since the spot shape on the optical recording medium corresponding to the one light beam can be deformed by the shape of the central region, the spot shape can be changed even if the second reflecting surface is non-rotationally symmetric with respect to the optical axis. Can be rounded. Further, the optical pickup device can be reduced in size as compared with the case where optical elements for adjusting the cross-sectional shape of the one light beam are arranged before and after the mirror portion.

  The second reflecting surface is intended to reflect the one of the light beam as diverging angle is the maximum in a predetermined plane, the central region is an ellipse having a major axis in the vertical direction of the predetermined plane, The cross section of the reflected light can be surely made circular. Accordingly, it is possible to accurately record and reproduce information using the optical recording medium corresponding to the one light beam.

The invention according to claim 32 is the optical unit according to any one of claims 28 to 31,
A protective layer thickness t _{1 of} the first optical recording medium;
The protective layer thickness t ₂ of the second optical recording medium is:
It is characterized by satisfying t ₁ <t ₂ .

  According to the thirty-second aspect of the invention, the same effect as that of any of the twenty-eighth to thirty-first aspects can be obtained.

The invention according to claim 33 is the optical unit according to any one of claims 28 to 32,
The first optical recording medium is BD,
The second optical recording medium is a CD.

  According to the invention of claim 33, the same effect as that of the invention described in any one of claims 28 to 32 can be obtained.

The invention of claim 34 is the optical unit according to any one of claims 28 to 32,
The first optical recording medium is an HD DVD,
The second optical recording medium is a CD.

  According to the invention of claim 34, the same effect as that of the invention described in any one of claims 28 to 32 can be obtained.

The invention according to claim 35 is an optical pickup device,
An optical unit according to any one of claims 28 to 34;
A first light source that emits a light flux of the first wavelength;
And a second light source that emits a light beam having the second wavelength.

  According to the invention of claim 35, the same effect as that of any one of claims 28 to 34 can be obtained.

The invention of claim 36 is the optical pickup device of claim 35,
The optical axis of the one light beam before being incident on the mirror section is offset with respect to the optical axis of the other light beam.

  According to the thirty-sixth aspect of the invention, since the optical axis of the one light flux is offset with respect to the optical axis of the other light flux before being incident on the mirror portion, It is possible to make the optical axis of the one luminous flux coincide with the optical axis of the other luminous flux. Accordingly, it is possible to accurately record and reproduce information using the first and third optical recording media.

The invention of claim 37 is
And the light flux of the relatively short first wavelength, the two types of light beams between the light beams of relatively longer second wavelength (where 1.9 <second wavelength / first wavelength <2.1) A selectively transmitting or reflecting mirror,
A first reflecting surface that transmits one of the two kinds of light beams and reflects the other light beam, and a first reflecting surface that transmits the first reflecting surface is reflected and converted into divergent light. And 2 reflective surfaces.

  According to the invention of claim 37, wherein, for example, used as an optical element of the two kinds of two with a light beam of recording information on an optical recording medium and / or an optical pickup apparatus for reproducing, the objective lens When arranged on the optical recording medium side of the mirror, one light beam is converted into divergent light by the second reflecting surface, and then condensed on the corresponding optical recording medium, and the other light beam is reflected by the second reflecting surface. Are not converted in the same manner and are condensed on the information recording surface of the corresponding optical recording medium, so that it is possible to accurately record and / or reproduce information on two types of optical recording media.

  In addition, since the mirror reflects the light beams of the first and second wavelengths and guides them to the objective lens, the optical pickup device can be miniaturized as much as the linear distance from the light source to the optical recording medium can be shortened. Can do.

  Further, even in the case of using two kinds of light beams of the first and second beams of wavelengths having approximately an integral multiple of the wavelength relationship, converting the divergent light only one light flux by the second reflecting surface Therefore, it is possible to reduce the influence of the diffractive action by the phase structure on these two kinds of light fluxes and to increase the light utilization efficiency.

The invention according to claim 38 is the mirror according to claim 37,
The second reflective surface, characterized in that the optical axis is a rotationally asymmetric curved surface.

  According to the invention of claim 37 wherein, the second reflecting surface is a rotationally asymmetric curved surface with respect to the optical axis, also the incident light to the second reflection surface is an elliptical shape, the cross-sectional shape of the reflected light Can be circular. Accordingly, it is possible to accurately record and reproduce information using the optical recording medium corresponding to the one light beam.

  According to the first aspect of the present invention, it is possible to accurately record and / or reproduce information on three types of optical recording media. In addition, the optical pickup device can be reduced in size.

  According to the second aspect of the present invention, the same effect as that of the first aspect of the invention can be obtained, and the cost of the optical unit can be reduced.

  According to the invention described in claim 3, the same effect as that of the invention described in claim 2 can be obtained, and the cost of the optical unit can be reduced. In addition, light utilization efficiency can be increased.

  According to the invention described in claim 4, the same effect as that of the invention described in claim 2 or 3 can be obtained, and the optical pickup device can be downsized.

  According to the fifth and sixth aspects of the invention, the same effect as that of the fourth aspect of the invention can be obtained, and information can be accurately recorded and reproduced using the third optical recording medium. can do.

  According to the seventh aspect of the invention, the same effect as that of the sixth aspect of the invention can be obtained, and the cross section of the reflected light can be surely made circular.

  According to the invention of claim 8, wherein, of course the invention and be able to obtain the same effect according to any one of claims 1 to 7, the optical pickup apparatus can be miniaturized.

  According to the ninth aspect of the present invention, it is possible to obtain the same effect as that of any one of the first to eighth aspects, as well as focusing of the optical pickup device with respect to the third optical recording medium. Performance and tracking performance can be improved.

  According to the tenth aspect of the present invention, it is possible to increase the diffraction efficiency of the first to third light beams, as well as to obtain the same effect as the ninth aspect of the invention.

  According to the invention of claim 11, wherein, of course according to claim 3 it is possible to obtain the same effect as described was kept the light use efficiency at a high level for the first light flux and the third light flux It is possible to record or reproduce information accurately. In addition, it is possible to accurately record or reproduce information.

  According to the twelfth aspect of the present invention, it is possible to obtain the same effect as the invention according to any one of the first to eleventh aspects, as well as the focusing performance and tracking performance of the optical pickup device. Can be made.

  According to the invention of Claims 13 and 14, the same effect as that of any one of Claims 1 to 12 can be obtained.

  According to the invention of claim 15, wherein, of course the invention and be able to obtain the same effect according to any one of claims 1 to 14, a more accurate recording and / or reproducing information Can be possible.

According to the invention of the sixteenth aspect, the same effect as that of the invention according to any one of the first to fifteenth aspects can be obtained.
According to the invention of claim 17, wherein, of course be able to obtain the same effect as the invention of claim 16 wherein the enable accurate recording and reproduction of information using the first to third optical recording medium It can be.

  According to the eighteenth aspect of the invention, it is possible to accurately record and / or reproduce information on three types of optical recording media. In addition, the optical pickup device can be reduced in size.

  According to the nineteenth aspect of the invention, the same effect as that of the eighteenth aspect of the invention can be obtained, and the cost of the optical unit can be reduced. In addition, light utilization efficiency can be increased.

  According to the invention of claim 20, claim 18 or 19 can be obtained the same effect as the invention described is of course, possible to enable accurate recording and reproduction of information using the optical recording medium Can do.

  According to the twenty-first aspect of the invention, it is possible to obtain the same effect as that of the eighteenth or nineteenth aspect of the invention, and it is possible to downsize the optical pickup device. Further, it is possible to accurately record and reproduce information.

  According to the twenty-second aspect, it is possible to accurately record and / or reproduce information on three types of optical recording media. In addition, the optical pickup device can be reduced in size. In addition, light utilization efficiency can be increased.

  According to the twenty-third aspect of the invention, it is possible to obtain the same effect as that of the twenty-second aspect of the invention and to reduce the cost of the optical unit.

According to the invention of claim 24 wherein, be able to obtain the same effect as the invention of claim 22 or 23, wherein it of course, can improve the focusing performance and tracking the performance of the optical pickup device.
According to the invention of claim 25 wherein, it is possible to obtain the same effect as described in any one of claims 22 to 24.

  According to the invention of claim 27, of course the invention and be able to obtain the same effect according to any one of claims 22 to 26, a more accurate recording and / or reproducing information Can be possible.

  According to the 28th aspect of the invention, it is possible to accurately record and / or reproduce information. In addition, the optical pickup device can be reduced in size. In addition, light utilization efficiency can be increased.

  According to claim 29 the invention described, it of course is possible to obtain the same effect as the invention of claim 28, it is possible to improve the focusing performance and tracking the performance of the optical pickup device.

  According to the thirty-third aspect of the invention, it is possible to obtain the same effect as that of the twenty-eighth or twenty-ninth aspect of the invention, and it is possible to accurately record and reproduce information.

  According to the invention of claim 31, wherein, of course the invention and be able to obtain the same effect according to any one of claims 28 to 30, the optical pickup apparatus can be miniaturized. Further, it is possible to accurately record and reproduce information.

According to the invention of claim 32 to 35, wherein it is possible to obtain the same effect as described in any one of claims 28 to 31.
According to the thirty-sixth aspect of the invention, the same effect as the thirty-fifth aspect of the invention can be obtained, and information can be accurately recorded and reproduced.

According to the thirty-seventh aspect of the invention, it is possible to accurately record and / or reproduce information. In addition, the optical pickup device can be reduced in size. In addition, light utilization efficiency can be increased.
According to the thirty-eighth aspect of the invention, the same effects as those of the thirty-seventh aspect of the invention can be obtained, and information can be accurately recorded and reproduced.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

First, a schematic configuration of the optical pickup device according to the present invention will be described.
FIG. 1 is a cross-sectional view showing a schematic configuration of the optical pickup device 1.
As shown in this figure, the optical pickup device 1 includes semiconductor laser light sources L1, L2, and L3 as the first to third light sources in the present invention.

  The semiconductor laser light source L1, when conducting recording / reproducing of information for a BD (Blu-ray disc) 10 as the first optical recording medium of the present invention (first optical recording medium), specific in wavelength 350~450nm The first light flux having the wavelength λ1 is emitted. The wavelength λ1 is the “first wavelength” in the present invention, and the first light flux is the “first wavelength light flux” in the present invention. In the present embodiment, the thickness of the protective layer of the BD 10 is 0.085 mm or 0.0875 mm. As the wavelength λ1, for example, 405 nm, 407 nm, 408 nm, or the like can be used.

  The semiconductor laser light source L2, when conducting recording / reproducing of information for DVD11 of the second optical recording medium of the present invention, a specific wavelength .lambda.2 in wavelength 620~680nm (1.5 <λ2 / λ1 <1. 7) The second light flux is emitted. In the present embodiment, the thickness of the protective layer of the DVD 11 is 0.6 mm. As the wavelength .lambda.2, it can be used, for example 655nm or 658 nm. In the present specification, DVD and may or DVD-ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW or the like, a general term of the optical recording medium of DVD series is there.

  The semiconductor laser light source L3, when recording / reproducing information for CD12 as the third optical recording medium of the present invention (second optical recording medium), a specific wavelength [lambda] 3 (1.9 in 750~810nm A third light flux of <λ3 / λ1 <2.1) is emitted. This semiconductor laser light source L3 is integrated with the photodetector 26 to form a hologram laser unit 27. The wavelength λ3 is the “second wavelength” in the present invention, and the third light flux is the “second wavelength light flux” in the present invention. Further, in the present embodiment, the thickness of the protective layer of CD12 is 1.2 mm. As the wavelength [lambda] 3, it can be used, for example 785 nm. In this specification, the CD is a general term for CD series optical recording media such as CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW, and the like.

  In the optical axis direction of the first light beam emitted from the semiconductor laser light source L1, the beam splitters 20 and 21, the collimator lens 22, the beam splitter 23, and the objective optical unit 6 are arranged in order from the lower side to the upper side in FIG. It is arranged. At a position facing the objective optical unit 6, a BD 10, DVD 11 or CD 12 as an optical recording medium is arranged.

To the beam splitter 20, the semiconductor laser light source L2 are arranged on the right side in FIG.
The thickness is different optical recording medium of the protective layer, and for example, BD10 and CD12, when performing recording and reproduction of information using a BD10 and DVD11 is usually the final focusing optical system during recording and reproduction of information surface, in this embodiment the distance between the most image side of the optical surface of the later of the objective lens 8, a light source side surface of each optical recording medium, a so-called working distance (WD) is different for each optical recording medium. Therefore, when recording / reproducing is performed using optical recording media having different protective layer thicknesses, when the mirror unit 7 and the objective lens 8 are integrally driven in the optical axis direction (Z-axis direction) as described later, by an amount corresponding to a difference in working distance, to shift the optical axis in the vertical direction (Y axis direction), that is, necessary to offset the optical axis of the other light beam to the optical axis of one light beam is used There is. Therefore, in the present embodiment, although not particularly illustrated, the optical axis of the second light beam emitted from the semiconductor laser light source L2 is set in advance by this shift amount before entering the objective optical unit 6. It is offset in the Y-axis direction in the figure with respect to the optical axis of the first light flux.

  Here, the Y-axis direction is an optical axis direction, that is, a direction perpendicular to the Z-axis direction. Each optical element of the optical pickup device 1 is a surface object with respect to the YZ plane including the Y-axis direction and the Z-axis direction.

Further, as a method for offsetting the optical axis of the second light flux to the optical axis of the first light flux, for example, the following three methods.
That is, in the first method (1), a light beam emitted from the semiconductor laser light source L2 is converted into a parallel light beam by a collimator lens, and then reflected by a prism or a beam splitter by 90 degrees so that each optical element is parallel to the first light beam. In this method, the distance between the collimating lens and the prism is changed according to the wavelength. According to this method, when the distance between the prism and the collimator lens is changed, the reflection position in the prism is changed, the state optical axis of the second light flux that is offset with respect to the optical axis of the first light flux It becomes. As a method for changing the distance between the collimating lens and the prism, the semiconductor laser light source L2 and the collimating lens are integrated to form a light emitting unit, and the light emitting unit is moved to Z while the position of the prism is fixed. A method of shifting along the axis or the Y axis can be mentioned.

  The second method (2), together with the light emitting point is disposed in close proximity to the semiconductor laser light source L1 and the semiconductor laser light source L2 to be shifted slightly, between the collimating lens 22 and the objective optical unit 6 In this method, a diffractive element that diffracts only the second light beam is disposed, and the optical axes of the semiconductor laser light source L1, the collimating lens 22, and the diffractive element are aligned. According to this method, the first light beam is converted into a parallel light beam by the collimator lens 22, and then passes through the diffraction element and enters the objective optical unit 6. On the other hand, the second light beam is converted into a substantially parallel light beam by the collimator lens 22 as an off-axis light beam, and then diffracted by the diffraction element and becomes parallel to the first light beam, so that the optical axis of the second light beam is the first light beam. It is in a state offset with respect to the optical axis. The diffraction element and the collimating lens 22 may be integrated.

  In the third method (3), each optical element is arranged so that the light beam emitted from the semiconductor laser light source L2 is collimated by a collimator lens and then reflected by a galvano mirror so as to be substantially parallel to the first light beam. This is a method of rotating the galvanometer mirror. According to this method, when the galvanometer mirror rotates, the reflection position of the galvanometer mirror changes, so that the optical axis of the second light beam is offset with respect to the optical axis of the first light beam.

  Further, a sensor lens 24 and a photodetector 25 are sequentially arranged on the right side in FIG. Sensor lens 24 is provided with a cylindrical lens 240 and concave lens 241.

  Further, a collimator lens 28 and a hologram laser unit 27 are sequentially arranged on the right side in FIG. The optical axis of the third light flux emitted from the semiconductor laser light source L3 of the hologram laser unit 27, before entering the objective optical unit 6, the optical axis of the first light flux, the offset in the Y-axis direction in FIG. Has been. In the present embodiment, the first method by (1) the optical axis of the third light flux has been offset with respect to the optical axis of the first light flux, the second offset by the method (2) It is also good to do.

Next, the objective optical unit 6 will be described in detail.
The objective optical unit 6 is an optical unit according to the present invention, and the first to third light beams emitted from the respective semiconductor laser light sources L1, L2, and L3 are placed on the information recording surfaces 10a, 11a, and 12a of the BD10, DVD11, and CD12. It has a function to condense. The objective optical unit 6 includes a mirror unit 7 and an objective lens 8. Note that these mirror 7 and the objective lens 8 because it has become integrally movable in the Y-axis direction and the Z-axis direction by an actuator (not shown), when the objective lens 8 and a mirror unit 7 is moved separately As a result of the reduction in coma caused by the movement of the objective lens 8, the focusing performance and tracking performance of the optical pickup device 1 are improved. Further, between these mirror 7 and the objective lens 8, the diaphragm member is disposed (not shown).

  Mirror unit 7, the first through third light flux emitted from the semiconductor laser light sources L1, L2, L3 is reflected is intended to guide the objective lens 8, and a dichroic mirror layer 71 and the substrate 70.

  The dichroic mirror layer 71 is a wavelength selective transmission layer in the present invention, and includes a reflective surface 71a that reflects the first light flux and the second light flux on the surface. The reflecting surface 71a is the first reflecting surface in the present invention, and transmits the third light flux into the dichroic mirror layer 71 without reflecting it. In the present embodiment, the reflecting surface 71a is a flat surface and is inclined 45 degrees with respect to the Z-axis direction in the YZ plane.

  The substrate 70 is a total reflection mirror provided on the back side of the dichroic mirror layer 71, and includes a reflection surface 70a that reflects the third light flux that has passed through the dichroic mirror layer 71 and converts it into divergent light.

  The reflective surface 70a is a second reflective surface in the present invention. The reflective surface 70a has a rotationally asymmetric free-form surface with respect to the optical axis. The free-form surface may be a rotationally symmetric curved surface with respect to the optical axis or a non-rotationally symmetric curved surface. However, in order to reliably correct the spherical aberration caused by the third light beam, the free-form surface is not rotationally symmetric. A curved surface is preferred. In the present embodiment, the reflecting surface 70a is a predetermined surface including the optical axis between the mirror unit 7 and the objective lens 8, so that the spherical aberration of the third light beam can be corrected by the objective lens 8. In the embodiment, the third light flux is reflected so that the divergence angle in the YZ plane is maximized.

  Specifically, in the present embodiment, the shape of the reflecting surface 70a is defined by the following formula (1).

In this formula (1), the left side of the Z (h) is an optical axis direction of the axis when the direction of travel of light is positive. The first term on the right side is a spherical term, and the second term is a free-form term. Also, "i", "j" is 0 or a positive integer, "C _ij" free surface coefficients, "k" is a conic coefficient (conic constant), "r" is the radius of curvature, "h" from the optical axis Represents the height of. In this embodiment, since the respective optical elements as described above has a surface target with respect to the YZ plane, of the free-form surface coefficients C _ij, which corresponds to the odd terms of X are all 0 It can be. Further, since the spherical term can be replaced with a free-form term such as X ² or Y ² , c = 0 and k = 0 can be set. Further, since the dichroic mirror layer 71 is inclined 45 degrees to the incident light, the center of the reflecting surface 70a to pass through the optical axis of the third light beam, and, if inclined 45 degrees as a whole reflecting surface 70a among the free surface coefficients C _ij, it may be 0 even terms corresponding to Y ^1.

  As shown in FIG. 2, the reflecting surface 70a is divided into a central region 70b intersecting the optical axis and an outer peripheral region 70c located on the outer peripheral side of the central region 70b.

  The center region 70b has an elliptical shape having a major axis in the direction perpendicular to the YZ plane, that is, the X-axis direction in FIG. The central region 70 b reflects the incident third light beam and guides it to the objective lens 8.

  The outer peripheral region 70c reflects the incident third light beam and is a flare component that does not contribute to spot formation on the information recording surface 12a of the CD 12.

  In addition, the above mirror part 7 may be shape | molded with glass, may be shape | molded with resin, and may be shape | molded with glass and plastic. As a mirror part molded with glass and plastic, for example, there is one in which the substrate 70 is made of glass and the dichroic mirror layer 71 is made of plastic.

  As shown in FIG. 1, the objective lens 8 condenses the first light beam on the information recording surface 10a of the BD 10, the second light beam on the information recording surface 11a of the DVD 11, and the third light beam on the information recording surface 12a of the CD 12. It is like that. The objective lens 8 is a single lens, and the optical pickup device 1 can be downsized as compared with the case where it is a lens unit.

  Incidentally, the image side numerical aperture NA of the objective lens 8, 0.85 for the first light flux emitted from the semiconductor laser light source L1, for the second light flux emitted from the semiconductor laser light source L2 0.66 The third light flux emitted from the semiconductor laser light source L3 is 0.51. The focal length of the objective lens is 1.76 mm for the first light beam emitted from the semiconductor laser light source L1, and 1.89 mm for the second light beam emitted from the semiconductor laser light source L2. and it has a 1.93mm for the third light flux emitted from L3. The refractive index of the objective lens 8 has a 1.55.

  Of the two optical surfaces of the objective lens 8, at least the optical surface on the light source side is divided into a first region 80, a second region 81, and a third region 82, as shown in FIG.

  The first region 80 is a region through which the first to third light beams that form a condensed spot on the information recording surfaces 10a, 11a, and 12a of the BD 10, the DVD 11, and the CD 12 are transmitted. The second area 81 is an area through which the first light flux and the second light flux that form a condensed spot on the information recording surfaces 10a and 11a of the BD 10 and the DVD 11 are transmitted. The third region 82 is a region through which the first light beam emitted from the semiconductor laser light source L1 that forms a focused spot on the information recording surface 10a of the BD 10 is transmitted.

  Among these first region 80, second region 81, and third region 82, at least the first region 80 and the second region 81 have a phase structure (not shown), or a diffraction structure in the present embodiment. This diffractive structure causes the spherical aberration of the first light flux and the second light flux by generating an optical path difference, that is, spherical aberration caused by the wavelength difference between the light fluxes, and BD10 and DVD11 which are relatively larger than this aberration. It is adapted to correct spherical aberration caused by a difference of protective layer thickness. In addition, this diffractive structure shows the maximum diffraction efficiency with the first-order diffracted light with respect to the first to third light beams.

  Here, in general, when one of the two wavelengths is an integral multiple of the other, it is known that it is difficult to correct the spherical aberration by the phase structure. In this embodiment, as described above, The ratio between the wavelengths λ1 and λ3 is approximately 2, and the ratio between the wavelengths λ1 and λ2 is not an integer. Therefore, the diffractive structure for correcting the spherical aberration of the light beams having the wavelengths λ1 and λ2 as described above has the spherical aberration of the light beams having the wavelengths λ1 and λ3, that is, the spherical aberration caused by the wavelength difference between the light beams and the aberration. a relatively large aberration is readily designed as compared with the diffractive structure for correcting the spherical aberration caused by a difference of protective layer thickness between BD10 and CD12, it enables cost reduction of the objective optical unit 6 ing.

  In general, when light beams of a plurality of wavelengths exhibit the maximum diffraction efficiency at the same diffraction order, it is known that the smaller the diffraction order, the higher the diffraction efficiency of each light beam. Therefore, when the diffractive structure exhibits the maximum diffraction efficiency with the first-order diffracted light with respect to the first to third light beams as described above, the diffraction efficiency of the first to third light beams is increased.

  In addition, since the diffractive structure shows the maximum diffraction efficiency at the same diffraction order with respect to the first to third light beams, the lengths of the wavelengths λ1 to λ3 are generated as they are as the strength of the diffracting action, so that in the first to third light beams, The third light beam is most strongly diffracted. Therefore, the third light flux is converted into divergent light by the reflective surface 70a is a reflecting surface 70a of the mirror unit 7, so that the spherical aberration is corrected in two stages by the diffractive structure of the objective lens 8. Therefore, when the diffractive structure exhibits the maximum diffraction efficiency with the first-order diffracted light with respect to the first to third light beams as described above, a part of the function for correcting the spherical aberration is shared by the diffractive structure. Since the divergence degree of the third light beam at 70a can be reduced, the focusing performance and tracking performance of the optical pickup device 1 with respect to the CD 12 can be improved.

  Note that the objective lens 8 described above may be made of glass, resin, or glass and plastic.

  Here, when the objective lens 8 is made of glass, it becomes difficult to be affected by a change in the refractive index due to a temperature change, so that the operating temperature range can be widened. Further, if a glass material having a small specific gravity, preferably a glass material having a specific gravity of 3.0 or less, more preferably a specific gravity of 2.8 or less, the burden on the actuator can be reduced. In addition, if a glass material having a glass transition point Tg of 400 ° C. or lower is used, molding at a relatively low temperature is possible, so that the life of a mold used for molding can be extended. Examples of the glass material having a low glass transition point Tg include “K-PG325” and “K-PG375” (trade names, manufactured by Sumita Optical Glass Co., Ltd.).

In the case of the objective lens 8 is made of resin, it is preferable to use the resin material of cyclic olefin, in particular, the refractive index at a temperature 25 ° C. for the wavelength 405nm is in the range of 1.54 to 1.60 there are a range of refractive index change rate dN / dT (℃ ^-1) is ^{-10 × 10 -5 ~-8 ×} 10 -5 with respect to the wavelength 405nm with temperature change within the temperature range of 70 ° C. from -5 ° C. It is preferable to use an inner resin material.

Further, as the resin material, it is also possible to use so-called "athermal resin". The athermal resin, uniformly mixing the particles with a refractive index change rate inversely refractive index change rate of the code of the matrix resin due to temperature changes in the base material resin, a resin material is dispersed. Examples of the matrix resin, Japanese Patent Application No. 2002-308933, Japanese Patent Application No. 2002-309040, may be appropriately employed preferably resins as described in Japanese Patent Application No. 2002-308964 or the like. As particles to be dispersed, particles having a diameter of 30 nanometers or less, preferably 20 nanometers or less, and more preferably 10 to 15 nanometers can be used. The fine particles are preferably inorganic and more preferably oxides. And in oxidation state is not saturated, is preferably an oxide which is not oxidized any more. If the particles are inorganic, the reaction with the matrix resin, which is a high molecular organic compound, can be kept low, and if the particles are oxides, deterioration due to use can be prevented. In particular, if the fine particles of inorganic oxide, high temperature and, even under severe conditions of being irradiated with the laser beam, it is possible to prevent deterioration due to oxidation. Of course, an antioxidant may be added to the athermal resin in order to prevent the base resin from being oxidized due to other factors. Further, the mixing / dispersing of the base resin and the particles is preferably performed in-line at the time of injection molding of the objective lens. In other words, the mixed / dispersed material is preferably not cooled / solidified until it is molded into the objective lens. In order to prevent aggregation of fine particles, it is preferable to disperse the particles by applying an electric charge to the particle surface. The ratio of the base resin to the fine particles can be adjusted as appropriate between 90:10 and 60:40. If the ratio is less than 90:10, the effect of suppressing the temperature change is reduced. On the other hand, if it exceeds 60:40, a problem occurs in the moldability of the resin, which is not preferable. However, the volume ratio can be appropriately increased or decreased in order to control the rate of change of the refractive index with respect to the temperature, and a plurality of types of nano-sized inorganic particles can be blended and dispersed. As an athermal resin as described above, for example, an acrylic resin in which fine particles of niobium oxide (Nb ₂ O ₅ ) are dispersed at a volume ratio of about 80:20 is available.

  When the objective lens 8 is made of glass and plastic, a hybrid lens in which a resin layer having a phase structure or a non-rotationally symmetric surface is bonded on a glass substrate may be used. In this case, it is possible to provide an objective lens with a wide operating temperature range, and it is possible to improve the transferability of the phase structure and the non-rotationally symmetric surface. In addition, as a method of forming the resin layer, a method of forming a resin layer by pressing a mold having a phase structure or a non-rotationally symmetric surface against an ultraviolet curable resin applied on a glass substrate and irradiating with ultraviolet rays is manufactured. Top suitable.

Next, the operation and action of the optical pickup device 1 will be briefly described.
During reproduction of information in the recording time and BD10 information to BD10 is a semiconductor laser light source L1 emits the first light flux. This first light beam is first transmitted through the beam splitters 20 and 21 and then converted into parallel light by the collimator lens 22 as indicated by the solid line in FIG. Next, the first light flux passes through the beam splitter 23 and then enters the objective optical unit 6. Next, the first light beam is reflected by the reflecting surface 71a of the mirror unit 7, is the diffractive structure corrects spherical aberration by being focused by the objective lens 8, the focused spot on the BD10 information recording surface 10a Form. At this time, the objective lens 8 performs focusing and tracking by the actuator arranged around the objective lens 8. In the present embodiment, since the objective lens 8 and the mirror unit 7 are integrally moved by the actuator to perform focusing, the reflection position at the mirror unit 7 changes during the focusing. The optical axis of the emitted light beam is shifted. Therefore, in focusing, by using the first method (1) or the third method for offsetting the optical axis (3), it is preferable to correct the optical axis deviation.

  Next, the light that forms the condensed spot is modulated by the information pits on the information recording surface 10a of the BD 10 and reflected. Next, the reflected light passes through the objective optical unit 6, the beam splitter 23 and the collimator lens 22 and is reflected by the beam splitter 21, and then astigmatism is given by the sensor lens 24 to reach the photodetector 25. To do. Then, by using the output signal of the photodetector 25, the information in the BD 10 is reproduced.

  Further, when recording information on the DVD 11 or reproducing information on the DVD 11, the semiconductor laser light source L2 emits the second light flux. The second light flux is first reflected by the beam splitter 20 and transmitted through the beam splitter 21, and then converted into parallel light by the collimator lens 22. Next, the second light flux passes through the beam splitter 23 and then enters the objective optical unit 6. Next, the second light beam, after being reflected by the reflecting surface 71a of the mirror unit 7 is corrected spherical aberration in the diffractive structure while being focused by the objective lens 8, converged spot on the information recording surface 11a of the DVD11 Form. At this time, the objective lens 8 performs focusing and tracking by the actuator arranged around the objective lens 8.

  Here, since the optical axis of the second light beam is offset in the Y-axis direction with respect to the optical axis of the first light beam before entering the mirror unit 7, unlike the case where it is not offset, the mirror unit 7 The optical axis of the second light flux after being emitted coincides with the optical axis of the first light flux. In focusing, it is preferable to correct the deviation of the optical axis in the same manner as focusing on the BD 10.

  Next, the light that forms the condensed spot is modulated by the information pits on the information recording surface 11a of the DVD 11 and reflected. Next, the reflected light passes through the objective optical unit 6, the beam splitter 23, and the collimator lens 22 and is reflected by the beam splitter 21, and then astigmatism is given by the sensor lens 24 to reach the photodetector 25. To do. Then, the information in the DVD 11 is reproduced by using the output signal of the photodetector 25.

  Further, when recording information on the CD 12 or reproducing information on the CD 12, the semiconductor laser light source L3 emits a third light beam. As shown by the broken line in FIG. 1, the third light beam is first converted into parallel light by the collimator lens 28, then reflected by the beam splitter 23, and incident on the objective optical unit 6. Next, the third light beam is reflected while being converted into divergent light by the reflecting surface 70a of the mirror unit 7, and then condensed by the objective lens 8 to form a condensed spot on the information recording surface 12a of the CD 12. At this time, the objective lens 8 performs focusing and tracking by the actuator arranged around the objective lens 8.

  Here, as shown in FIG. 4, the optical axis of the third light beam is offset in the Y-axis direction with respect to the optical axis of the first light beam before being incident on the mirror unit 7, and thus is not offset. Unlike the above, the optical axis of the third light flux after being emitted from the mirror unit 7 and the optical axis of the first light flux coincide with each other. Further, of the third light flux incident on the reflecting surface 70a, only the light flux incident on the central area 70b is condensed on the CD 12 by the objective lens 8, and the light flux incident on the outer peripheral area 70c is not condensed on the CD 12, so that the central area The opening is limited by the size of 70b. The reflecting surface 70a is a non-rotationally symmetric curved surface with respect to the optical axis so that the divergence angle of the third light flux after reflection is maximized in the YZ plane, and the central region 70b is a long axis in the X-axis direction. Therefore, the cross-sectional shape and the focused spot of the reflected light of the third light beam are circular. In focusing, it is preferable to correct the deviation of the optical axis in the same manner as focusing on the BD 10.

  Next, the light that forms the condensed spot is modulated by the information pits on the information recording surface 12a of the CD 12 and reflected. Next, the reflected light passes through the objective optical unit 6, is reflected by the beam splitter 23, is condensed by the collimating lens 28, and reaches the photodetector 26. Then, by using the output signal of the photodetector 26, information in the CD 12 is reproduced.

  According to the optical pickup device 1 described above, it is possible to accurately record and reproduce information with respect to the BD 10, the DVD 11, and the CD 12. Further, since the mirror unit 7 as described above is guided to the object lens 8 by the first through third light flux reflected respectively, it is possible to shorten the straight line distance from the semiconductor laser light source L1~L3 to BD10, DVD 11, CD12 As much as possible, the optical pickup device 1 can be miniaturized.

  Further, it is possible to the aperture restriction by the size of the central area 70b, as compared with the case of arranging a diaphragm member before and after the mirror 7 to the aperture limitation, to miniaturize the optical pickup device 1 be able to.

  Further, since the condensing spot of the third light flux on the information recording surface 12a of the CD 12 can be made circular due to the elliptical shape of the central region 70b, information recording / reproduction using the CD 12 can be performed accurately.

  Further, the optical axis and the first light flux of the third light flux after being emitted from the mirror unit 7, since the optical axis of the second light flux can be matched, the recording and reproducing of the BD10, DVD 11, information with CD12 Can be done accurately.

  Further, since the first light flux and second light flux shorter wavelength than the third light flux is not divergent light by the mirror portion 7, as compared with the case where the first light flux and second light flux is divergent light, the objective lens 8 It becomes easy to design. Therefore, the cost of the objective optical unit 6 can be reduced.

  In the above embodiment, the mirror unit 7 converts the first and second light fluxes into light fluxes whose spherical aberration can be corrected by the objective lens 8, but this converts the incident parallel light flux into divergent light. It is not limited to converting. In short, depending on which wavelength of the incident light beam the objective lens 8 is optimized, the incident light beam of other wavelengths may be converted into a light beam as necessary. That is, in the present embodiment (more specifically, a second example described later), the mirror unit 7 when the objective lens 8 is optimized so as to be able to correct spherical aberration with respect to the light beam for the BD 10 is provided. Although shown, when the objective lens 8 is optimized in the light flux for CD12, the mirror unit 7 with respect to the first light flux for BD10 or HDDVD, also be converted in a direction to converge the incident light beam good.

  In addition, the phase structure of the objective lens 8 has been described as showing the maximum diffraction efficiency with the first-order diffracted light with respect to the first to third light beams, but the first and third light beams are transmitted without being diffracted, and With respect to the two light beams, the maximum diffraction efficiency may be exhibited by the first-order diffracted light.

Further, although the first optical recording medium in the present invention has been described as BD10, it may be HDDVD.
Further, the reflecting surface 70a of the mirror unit 7 has been described as a shape defined by equation (1), it may be other shapes.

Next, examples of the objective optical unit 6 shown in the above embodiment will be described. However, the present invention is not limited to the examples.
Table 1 to Table 3 show CD, DVD, the data of the objective optical unit of the present embodiment for BD.

  In these tables, the surface number “1” indicates the light emitting points of the semiconductor laser light sources L1 to L3, the surface numbers “2” and “3” indicate the reflecting surfaces 71a and 70a of the mirror unit 7, and the surface number “4” indicates the mirror. In the air layer between the portion 7 and the objective lens 8, the surface number “5” indicates a diaphragm member. Surface numbers “6-1”, “6-2”, and “6-3” indicate the first region 80, the second region 81, and the third region 82 on the light source side optical surface of the objective lens 8, and the surface number “ Reference numeral 7 ”denotes an optical surface of the objective lens 8 on the optical recording medium side. The surface number “8” indicates the air layer between the objective lens 8 and the optical recording medium, the surface number “9” indicates the protective layer of the optical recording medium, and the surface number “10” indicates the information recording surface of the optical recording medium. Show. Note that the thickness of the air layer having the surface number “8” is a so-called working distance.

Further, the reflection surface 70a of the mirror section 7 is formed in a shape defined by a mathematical formula in which the free-form surface coefficient C _ij in Table 4 below is substituted into the above formula (1). Here, the terms Y ² , Y ³ , and Y ⁴ work so that the marginal ray in the Y-axis direction emitted from the dichroic mirror layer 71 becomes divergent light. In particular, the term Y ^{3 is} a term that compensates for the asymmetry of the optical system in the Y-axis direction. The terms X ² , X ² Y, X ⁴ , and X ² Y ² work so that the marginal ray in the X-axis direction emitted from the mirror unit 7 becomes divergent light. In particular, X ² Y, term of X ² Y ² is a term for adjusting a divergence degree that depends on the height of the Y-axis direction.

  In the mirror part 7 described above, the reflecting surfaces 70a and 71a as a whole are inclined by 45 degrees with respect to the optical axis, and the center of the reflecting surface 71a is offset by -0.2665 mm in the Y-axis direction with respect to the center of the reflecting surface 70a. Yes.

Further, the light source side optical surface of the objective lens 8 is formed on the aspherical surface defined by equation obtained by substituting the equation (2) below aspherical coefficients B _2i in Table 5 below. In the formula (2), the left side of the Z (h) is an optical axis direction of the axis when the direction of travel of light is positive.

The diffractive structure formed on this optical surface is expressed using an optical path length added to the transmitted wavefront. Further, this optical path difference is represented by an optical path difference function Φ defined by substituting the diffraction coefficient C _2i shown in Table 6 below into the following formula (3). However, in Formula (3), “m” is the diffraction order of the diffracted light indicating the maximum amount of diffracted light among the diffracted light generated on the diffractive surface. Further, "lambda" is the wavelength of the incident light beam, 'lambda _B "is the preparation wavelength.

Further, the optical surface of the objective lens 8 on the optical recording medium side is formed as an aspheric surface defined by an equation obtained by substituting the aspheric coefficient B _2i in the following Table 7 into the equation (2).

  In this objective lens 8, the image-side numerical aperture NA is 0.85 for BD10, 0.66 for DVD11, and 0.51 for CD12. The focal length of the objective lens 8 is 1.76 mm for the BD 10, 1.89 mm for the DVD 11, and 1.93 mm for the CD 12. The pupil diameter of the stop surface of the objective lens 8 is 3.0 mm for BD10, 2.44 mm for DVD11, and 2.0 mm for CD12. In addition, the value of the height h for the first region 80 is 0 mm ≦ h ≦ 1.02 mm, the value of the height h for the second region 81 is 1.02 mm ≦ h ≦ 1.225 mm, The value of the height h for the three regions 82 is 1.225 mm ≦ h ≦ 1.6 mm.

  Next, another example of the objective optical unit 6 shown in the above embodiment will be described. However, the present invention is not limited to the examples.

  Tables 8 to 10 below show data of the objective optical unit of the present example for CD, DVD, and BD.

  The surface numbers in Tables 8 to 10 are the same as in Example 1 described above.

The reflection surface 70a of the mirror unit 7 is formed in a shape defined by a mathematical formula in which the free-form surface coefficient C _ij in the following Table 11 is substituted into the above formula (1). Terms such as “Y ² ” are the same as those in the first embodiment.

  In the mirror part 7 described above, the reflecting surfaces 70a and 71a as a whole are inclined by 45 degrees with respect to the optical axis, and the center of the reflecting surface 71a is offset by -0.2665 mm in the Y-axis direction with respect to the center of the reflecting surface 70a. Yes.

Further, the light source side optical surface of the objective lens 8 is formed to aspherical surface coefficients B _2i in the following Table 12 to the non-spherical surface which is defined by the equation obtained by substituting the above equation (2).

The diffractive structure formed on this optical surface is expressed using an optical path length added to the transmitted wavefront. Further, this optical path difference is represented by an optical path difference function Φ defined by substituting the diffraction coefficient C _2i shown in Table 13 below into the above-described equation (3).

Further, the optical surface of the objective lens 8 on the optical recording medium side is formed as an aspheric surface defined by an equation obtained by substituting the aspheric coefficient B _2i in the following Table 14 into the above equation (2).

  In this objective lens 8, the image-side numerical aperture NA is 0.85 for BD10, 0.60 for DVD11, and 0.51 for CD12. The focal length of the objective lens 8 is 1.76 mm for the BD 10, 1.88 mm for the DVD 11, and 1.82 mm for the CD 12. The pupil diameter of the stop surface of the objective lens 8 is 3.0 mm for BD10, 2.22 mm for DVD11, and 2.0 mm for CD12. In the objective lens according to the present embodiment, unlike the first embodiment, a step structure having different characteristics for each of the plurality of regions is not formed.

  Above, in the objective optical unit 6 of Examples 1 and 2, the root mean square of the aberration on the optical axis, 0.013Ramudarms at wavelength [lambda] 3, 0.006Ramudarms a wavelength .lambda.2, good results and 0.002λrms at wavelength λ1 showed that. Further, the root mean square of the aberration when the incident angle to the objective lens 8 is 0.5 degrees is 0.060 λrms at the wavelength λ3.

  When the diffraction order indicating the maximum diffraction efficiency of the objective lens 8 is the second order at the wavelength λ2 and the first order at the wavelength λ1, the mean square of the aberration when the incident angle of the objective lens 8 is 0.5 degrees. The square root was 0.160 λrms or more at the wavelength λ3, and the aberration was not sufficiently corrected.

It is a figure which shows schematic structure of the optical pick-up apparatus which concerns on this invention. It is a figure which shows the reflective surface of the board | substrate of a mirror part. It is a figure which shows the optical surface by the side of the light source of an objective lens. It is a figure for demonstrating the optical axis of the offset 3rd light beam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical pick-up apparatus L1-L3 Semiconductor laser light source 6 Objective optical unit (optical unit)
7 Mirror unit 8 Objective lens 10 BD (first optical recording medium)
11 DVD (second optical recording medium)
12 CD (third optical recording medium)
70 Substrate 70a Reflecting surface (second reflecting surface)
70b the central region 70c outer peripheral region 71 dichroic mirror layer 71a reflecting surface (first reflecting surface)

Claims (38)

The first optical recording medium, the second optical recording medium, and the third light are emitted from the light source using the first light flux, the second light flux, and the third light flux having wavelengths λ1, λ2, and λ3 (where λ1 <λ2 <λ3). An optical unit for an optical pickup device for recording and / or reproducing information on a recording medium,
An objective lens having a phase structure on at least one optical surface;
Among the first to third light fluxes, two a first reflecting surface that transmits the remaining one light flux with reflecting light beams, wherein by reflecting the remaining one of the light beam transmitted through the first reflecting surface A second reflection surface that converts the light into divergent light, and a mirror unit that guides the reflected first to third light fluxes to the objective lens,
The objective lens is
The spherical aberration of the two kinds of light beams is corrected by the phase structure, the first light flux on the information recording surface of the first optical recording medium, the second light flux on the information recording surface of the second optical recording medium , an optical unit, characterized in that said third, respectively condensing the light beam on the information recording surface of the third optical recording medium. The optical unit according to claim 1, wherein
The optical unit, wherein the mirror unit reflects the first light flux and the second light flux by the first reflecting surface and the third light flux by the second reflecting surface. The optical unit according to claim 2, wherein,
The wavelengths λ1, λ2, and λ3 are
Optical unit and satisfies the 1.9 <λ3 / λ1 <2.1 and 1.5 <λ2 / λ1 <1.7,. The optical unit according to claim 2 or 3,
The second reflecting surface comprises a central region intersecting with the optical axis, and an outer peripheral area located on the outer peripheral side of the central region,
Wherein one of the third light flux by the second incident on the reflecting surface, an optical unit, characterized in that only the light beam incident on the central area is converged on the third optical recording medium by the objective lens. The optical unit according to claim 4, wherein
The optical unit, wherein the second reflecting surface is a non-rotationally symmetric curved surface with respect to the optical axis. The optical unit according to claim 4, wherein
The second reflecting surface is a non-rotationally symmetric curved surface with respect to the optical axis,
The optical unit is characterized in that the central region is elliptical. The optical unit according to claim 6, wherein
The second reflecting surface is intended to reflect the remaining one light flux as divergent angle within the predetermined plane is maximum including the optical axis between said mirror portion and the objective lens,
Said central region, an optical unit, characterized in that the vertical direction of the predetermined plane is elliptical with a major axis. In the optical unit according to any one of claims 1 to 7,
2. The optical unit according to claim 1, wherein the objective lens is a single lens. In the optical unit according to any one of claims 1 to 8,
Wherein the phase structure is a diffractive structure,
The diffractive structure relates to the aforementioned first to third light fluxes, an optical unit, characterized in that indicating the maximum diffraction efficiency at the same diffraction order. The optical unit according to claim 9, wherein
The diffractive structure relates to the aforementioned first to third light fluxes, an optical unit, characterized in that indicating the maximum diffraction efficiency in the first order diffracted light. The optical unit according to claim 3, wherein,
The phase structure is
Transmitting the incident first light flux and the third light flux;
Wherein for the second light flux, the optical unit, characterized in that indicating the maximum diffraction efficiency in the first order diffracted light incident. In the optical unit according to any one of claims 1 to 11,
An optical unit comprising an actuator for integrally moving the objective lens and the mirror unit. In the optical unit according to any one of claims 1 to 12,
A protective layer thickness t ₁ of the first optical recording medium;
A protective layer thickness t ₂ of the second optical recording medium;
The protective layer thickness t ₃ of the third optical recording medium is
An optical unit satisfying t ₁ <t ₂ <t ₃ . In the optical unit according to any one of claims 1 to 13,
The first optical recording medium is BD,
The second optical recording medium is DVD,
The optical unit, wherein the third optical recording medium is a CD. In the optical unit according to any one of claims 1 to 14,
The objective lens corrects a spherical aberration caused by a difference in protective layer thickness of two types of optical recording media corresponding to the two types of light beams among the first to third optical recording media by the phase structure. A featured optical unit. The optical unit according to any one of claims 1 to 15,
A first light source that emits the first luminous flux;
A second light source that emits the second light flux;
An optical pickup device comprising: a third light source that emits the third light flux. The optical pickup device according to claim 16, wherein
An optical pickup device, wherein an optical axis of the remaining one type of light flux before being incident on the mirror portion is offset with respect to an optical axis of the two kinds of light flux. A mirror that selectively transmits or reflects the first light beam, the second light beam, and the third light beam having wavelengths λ1, λ2, and λ3 (where λ1 <λ2 <λ3);
A first reflecting surface that reflects two types of light beams among the first to third light beams incident thereon and transmits the remaining one type of light beams;
A mirror comprising: a second reflecting surface that reflects the remaining one type of light flux that has passed through the first reflecting surface to convert it into divergent light. The mirror of claim 18.
The wavelengths λ1, λ2, and λ3 are
Mirror and satisfies the 1.9 <λ3 / λ1 <2.1 and 1.5 <λ2 / λ1 <1.7,. In the mirror according to claim 18 or 19, wherein,
The mirror, wherein the second reflecting surface is a non-rotationally symmetric curved surface with respect to the optical axis. The mirror according to claim 18 or 19,
The first reflecting surface and the second reflecting surface reflect the incident first to third light fluxes and guide them to a subsequent optical element,
The second reflecting surface is a non-rotationally symmetric curved surface with respect to the optical axis,
A central region intersecting the optical axis;
An outer peripheral region located on the outer peripheral side of the central region,
Of the remaining one type of light beam incident on the second reflecting surface, only the light beam incident on the central region is guided to the subsequent optical element,
The central region is
A mirror characterized by being elliptical. First, second, and third light beams having wavelengths λ1, λ2, and λ3 (1.9 <λ3 / λ1 <2.1) emitted from the light source are used for the first optical recording medium and the second light. recording medium, an optical unit for an optical pickup apparatus for recording and / or reproducing information for the third optical recording medium,
An objective lens having a phase structure on at least one optical surface;
A first reflecting surface that transmits one of the first light beam and the third light beam, and reflects two types of light beams, the other light beam and the second light beam, and the first reflecting surface. A second reflection surface that reflects the one light beam, and a mirror unit that guides the reflected first to third light beams to the objective lens,
The second reflecting surface converts the incident one light beam into a light beam whose spherical aberration can be corrected by the objective lens and guides it to the objective lens,
The objective lens is
The spherical aberration of the two types of light beams reflected by the first reflection surface is corrected by the phase structure, and the first light beam is applied to the information recording surface of the first optical recording medium, and the second light beam is applied to the second light beam. An optical unit for focusing the third light flux on the information recording surface of the third optical recording medium, respectively, on the information recording surface of the optical recording medium. The optical unit of claim 22, wherein,
The wavelengths λ1 and λ2 are
An optical unit satisfying 1.5 <λ2 / λ1 <1.7. 24. The optical unit according to claim 22 or 23.
An optical unit comprising an actuator for integrally moving the objective lens and the mirror unit. The optical unit according to any one of claims 22 to 24,
A protective layer thickness t ₁ of the first optical recording medium;
A protective layer thickness t ₂ of the second optical recording medium;
The protective layer thickness t ₃ of the third optical recording medium is
An optical unit satisfying t ₁ <t ₂ <t ₃ . The optical unit according to any one of claims 22 to 25,
The first optical recording medium is a BD,
The second optical recording medium is a DVD,
The optical unit, wherein the third optical recording medium is a CD. The optical unit according to any one of claims 22 to 26,
The objective lens, among the first to third optical recording medium, to correct spherical aberration caused by the difference of the protective layer thickness of 2 kinds of optical recording medium corresponding to the two kinds of light beams by the phase structure A featured optical unit. Of the at least two kinds of light beams emitted from the light source, performs recording and / or reproducing of information for the first optical recording medium with a light beam relatively short first wavelength, a relatively long first Optical pickup apparatus for recording and / or reproducing information on a second optical recording medium using a light beam having two wavelengths (provided that 1.9 <second wavelength / first wavelength <2.1) An optical unit for
An objective lens;
A first reflecting surface that transmits one of the first wavelength and the second wavelength and reflects the other; and the one that passes through the first reflecting surface. And a mirror part for guiding the reflected light beam of the first wavelength and the light beam of the second wavelength to the objective lens,
The mirror unit converts the light beam having the first wavelength or the light beam having the second wavelength into a light beam whose spherical aberration can be corrected by the objective lens, and guides the light to the objective lens.
The objective lens is
The light beam having the first wavelength is condensed on the information recording surface of the first optical recording medium, and the light beam having the second wavelength is condensed on the information recording surface of the second optical recording medium. Optical unit. The optical unit according to claim 28,
An optical unit comprising an actuator for integrally moving the objective lens and the mirror unit. 30. The optical unit according to claim 28 or 29.
The optical unit, wherein the second reflecting surface is a non-rotationally symmetric curved surface with respect to the optical axis. The optical unit according to any one of claims 28 to 30, wherein
The second reflecting surface is
A central region intersecting the optical axis, and an outer peripheral region located on the outer peripheral side of the central region,
The one light flux is reflected so that a divergence angle within a predetermined plane including the optical axis between the mirror unit and the objective lens is maximized,
Of the one light beam incident on the second reflecting surface, only the light beam incident on the center region is condensed on the optical recording medium corresponding to the light beam by the objective lens,
Said central region, an optical unit, characterized in that the vertical direction of the predetermined plane is elliptical with a major axis. The optical unit according to any one of claims 28 to 31,
A protective layer thickness t _{1 of} the first optical recording medium;
The protective layer thickness t ₂ of the second optical recording medium is:
An optical unit satisfying t ₁ <t ₂ . The optical unit according to any one of claims 28 to 32,
The first optical recording medium is BD,
The optical unit, wherein the second optical recording medium is a CD. The optical unit according to any one of claims 28 to 32,
The first optical recording medium is an HD DVD,
The optical unit, wherein the second optical recording medium is a CD. An optical unit according to any one of claims 28 to 34;
A first light source that emits a light flux of the first wavelength;
An optical pickup device comprising: a second light source that emits a light beam having the second wavelength. 36. The optical pickup device according to claim 35, wherein
The optical pickup device according to claim 1, wherein an optical axis of the one light beam before being incident on the mirror portion is offset with respect to an optical axis of the other light beam. Two types of light fluxes, a light flux having a relatively short first wavelength and a light flux having a relatively long second wavelength (where 1.9 <second wavelength / first wavelength <2.1), A selectively transmitting or reflecting mirror,
A first reflecting surface that transmits one of the two kinds of light beams and reflects the other light beam, and a first reflecting surface that transmits the first reflecting surface is reflected and converted into divergent light. A mirror comprising two reflecting surfaces. 38. The mirror of claim 37.
The mirror, wherein the second reflecting surface is a non-rotationally symmetric curved surface with respect to the optical axis.

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