JP2000082232A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an optical pickup device capable of excellently performing one or more operations of recording/reproducing and erasing of information without needing any dedicated beam shaping means for two kinds of optical recording media different in substrate thickness. SOLUTION: A first light source LD 201 between light sources LD 201, 211 with light emitting wavelengths different from each other is turned on only when a first kind of optical recording medium 207 is used, and a second light source LD 211 is turned on only when a second kind of optical recording medium 217 is used. Then, coupling lenses 202, 212 are anamorphic lenses different in lens action in the directions that the divergent angle of incident luminous flux becomes maximum and becomes minimum, and are provided with functions substantially collimating and beam-shaping the luminous fluxes the first and second light sources LD 201, 211.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical pickup device.

[0002]

2. Description of the Related Art Recently, there is a strong demand for an optical recording medium represented by an optical disk to have a large recording capacity. In order to increase the recording capacity without increasing the size of the optical recording medium itself, it is necessary to reduce the diameter of a light spot for recording / reproducing information. Since the light spot diameter is proportional to the wavelength: λ, the recording capacity is inversely proportional to the square of the wavelength: λ. For this reason, the light source wavelength used in the optical pickup device has been shortened, and the light source wavelength: 6 compared to a conventional optical disc (CD-R) that performs recording / reproduction at a wavelength of 785 nm.
An optical disk (DVD) that performs recording and reproduction at 50 nm has been realized. The light beam from the light source is condensed as a light spot on the optical recording surface via the transparent substrate of the optical recording medium, but the shape of the light spot is degraded by coma caused by the inclination of the substrate. Coma is proportional to the cube of the numerical aperture of the objective lens, and is proportional to the substrate thickness of the optical recording medium. Therefore, in order to reduce the influence of coma aberration, the substrate thickness is set thin in an optical recording medium having a large recording capacity. By the way, the above CD-R
The substrate thickness in DVD is set to be as thin as 0.6 mm, whereas the substrate thickness in DVD is 1.2 mm. As an optical pickup device that can be used for any of different types of optical recording media having different substrate thicknesses as described above, two types of semiconductor lasers having different emission wavelengths (abbreviated as light source LD in this specification) are used as light sources. An optical pickup device having the same has been proposed (JP-A-6-259804).

By the way, as is well known, the light source LD
Is divergent, the divergence angle is the largest in the direction perpendicular to the active layer, the smallest in the direction parallel to the active layer, and the far field pattern (hereinafter FF)
P) is an elliptical shape. The light spot condensed on the optical recording medium is preferably “circular”, and as the light spot becomes “elliptical”, the recording / reproducing ability tends to decrease. In order to obtain a circular light spot, when coupling the light beam from the light source LD with the coupling lens, a part of the FFP in the long axis direction may be shielded to obtain a circular light beam cross section. In this method, an insignificant portion of the light beam from the light source is blocked from the optical recording medium, so that the efficiency of using the light energy used for recording / reproduction is low. When information is recorded on an optical recording medium by an optical pickup device, “light energy of 10 times or more of information reproduction” is required. For this purpose, the numerical aperture of the coupling lens is increased and the light source is increased. A larger portion of the light beam from the LD needs to be taken into light spot formation. At that time, simply taking in the edge of the light beam in the long axis direction of the FFP would result in an elliptical light spot shape. Is performed so that the beam approaches a circular shape. In the optical pickup device disclosed in the above publication, there is no problem regarding beam shaping. Beam shaping is generally performed using a combination of prisms as disclosed in Japanese Patent Application Laid-Open No. 4-34740. However, bending of the optical path by the prisms restricts the optical arrangement, and disadvantages in the layout of the optical system are disadvantageous. Many.

[0004]

According to the present invention, one or more of information recording / reproducing / erasing can be favorably performed on two types of optical recording media having different substrate thicknesses without using a dedicated beam shaping means. It is an object to realize an optical pickup device.

[0005]

An optical pickup device according to the present invention "performs at least one of information recording, reproduction, and erasure on first and second types of optical recording media having different substrate thicknesses. Optical pickup device ", the first and second
Light source LD, coupling lens, objective lens,
An optical path separating optical unit, a detecting unit, and a control unit are provided (claim 1). Hereinafter, for the sake of specificity of description, it is assumed that the substrate thickness of the first type optical recording medium is t ₁ , the substrate thickness of the second type optical recording medium is t _2, and t ₁ <t ₂ . That is, the first type optical recording medium has a larger recording capacity than the second type optical recording medium. The first light source LD is a for the first type of optical recording medium wavelength emits laser light of lambda _1. The second light source LD is
A laser beam having a wavelength of λ ₂ is emitted for the second type of optical recording medium. λ ₁ <λ ₂ . The coupling lens is a lens that couples a light beam from each light source LD,
It is provided individually for each light source LD or common to both light sources LD. The objective lens is a lens that condenses each light beam coupled by the coupling lens as a light spot on the optical recording surface of the corresponding optical recording medium, and individually or separately for each light source LD.
Are provided in common to The optical path separating optical unit is an optical unit that separates each light beam reflected by the optical recording medium and returned as a light beam through the objective lens from an irradiation optical path from the light source LD to the objective lens. It is provided individually or commonly for both light sources LD. The detecting means is a means for receiving each light beam separated by the optical path separating optical means and detecting information on a reflected light beam (return light beam). The detecting means can be provided individually for each light source LD, or at least a part of the detecting means can be shared for both light sources LD. The control means is means for performing focusing control and tracking control based on the detection result of the detection means. The first light source LD
Lights up only when the first type of optical recording medium is used,
The second light source LD is turned on only when the second type of optical recording medium is used. The coupling lens is an anamorphic lens having different lens functions in a direction in which the divergence angle of the incident light beam is maximized (the major axis direction of the FFP) and a direction in which the divergence angle is minimized (the minor axis direction of the FFP). The light beam from the two light sources LD is configured to have “substantially collimating function and beam shaping function”.
That is, in the optical pickup device of the present invention, since the coupling lens has a coupling function and a beam shaping function, it is not necessary to provide a dedicated beam shaping unit. Further, since the coupling lens collimates the light beam from the light source LD, the length of the optical path from the coupling lens to the objective lens can be freely set. Also, since there is no bending of the optical path due to beam shaping, the degree of freedom in the layout of the optical system is large.

As described above, in the optical pickup device according to the first aspect, the coupling lens, the objective lens, the optical path separating optical unit, and the detecting unit can be individually provided for each light source LD. Therefore, the first light source LD
And the first coupling lens, the first objective lens, the first optical path separating optical unit, and the first detecting unit, and the second light source LD with the second coupling lens. And the second objective lens, the second optical path separating optical unit, and the second detecting unit. In this case, the same type of lens is used as the first and second coupling lenses (claim 2). In the optical pickup device according to the second aspect, there are two types of optical pickups, an optical pickup used for a first type optical recording medium and an optical pickup used for a second type optical recording medium. Will be. An optical pickup device having two systems of optical pickups requires optical elements constituting each system, so that the cost tends to be high.
Since the same type of coupling lens can be used for the optical pickup of each system, the cost can be reduced as compared with the case where another type of coupling lens is used for each system. In the optical pickup device according to the second aspect, the control means may be individualized for each system of the optical pickup, or may be shared for both systems of the optical pickup.

An optical pickup device according to a third aspect is characterized in that "at least a coupling lens is shared" for the first and second light sources LD. in this case,
The two light sources LD may be mechanically displaced to switch the combination with a common coupling lens, or a coupling common to the first and second light sources LD. Optical path merging means for merging the optical paths of the first and second light sources LD with the lens may be provided. An optical pickup device according to a fifth aspect is the optical pickup device according to the first, third, or fourth aspect, wherein the objective lens is provided with the first and second light sources L.
The optical characteristics (such as spherical aberration) of the objective lens with respect to the wavelength (λ ₁ ) used for the optical recording medium having the smaller substrate thickness (the first type of optical recording medium), The optical characteristics are set to be equal to or greater than the optical characteristics with respect to the wavelength (λ ₂ ) used for the thick optical recording medium (second type optical recording medium). When an objective lens is used in common for each light source LD, the objective lens must form a good light spot on the optical recording surface of each optical recording medium having a different substrate thickness. In this case, the optical conditions for light spot imaging are more severe for the first type of optical recording medium having a small diameter of the light spot to be formed, so the optical characteristics of the objective lens are set as described above. . In the optical pickup device according to the fourth or fifth aspect, the coupling lens and the optical path separating optical unit are shared with the first and second light sources LD, and at least a part of the detecting unit is shared. (Claim 6). Of course, in this case, a common objective lens can be used.

In the optical pickup device according to any one of the first to fifth aspects, a first light source LD, a first light receiving element for receiving a return light beam from a first type of optical recording medium, While transmitting the light beam from the first light source LD,
A first hologram element that diffracts the return light beam toward the first light receiving element is formed as a single unit, and the second light source LD and the second light receiving the return light beam from the second optical recording medium are used. The light receiving element and the second hologram element that transmits the light beam from the second light source LD and diffracts the returning light beam toward the second light receiving element can be a single unit. . Further, in the optical pickup device according to the sixth aspect, the first light source LD, the second light source LD, the return light flux from the first type optical recording medium and the second light source LD are provided.
A light receiving element that receives the return light beam from the optical recording medium of the same kind in common and a hologram element that transmits the light beam from each light source LD and diffracts each return light beam toward the light receiving element are configured as a single unit. (Claim 8). 9. The optical pickup device according to claim 7, wherein the hologram element is a polarization hologram, and the polarization plane of each return beam is rotated by 90 degrees with respect to the polarization plane of the beam from each light source LD toward the optical recording medium. A configuration having a / 4 wavelength plate can be adopted. The polarization hologram is a "hologram having a different hologram effect depending on the polarization state of the incident light beam with respect to the hologram".
When a polarization hologram is used, the light beam from the light source LD is transmitted without the diffraction effect of the hologram, and 1 /
Using a four-wavelength plate, the polarization plane of the return light beam is set to 9
By turning by 0 degrees, the returning light beam can be diffracted by the hologram. Therefore, light use efficiency is high. In the optical pickup device according to any one of claims 1 to 9, the coupling lens can be made of a single kind of glass material (claim 10), and both surfaces of the coupling lens are aspherical. (Claim 1
1). The substrate thickness of the first type optical recording medium is 0.6 m
m, the substrate thickness of the second type optical recording medium can be set to 1.2 mm (claim 12).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment shown in FIG.
Reference numeral 207 denotes a first type optical recording medium, and reference numeral 217 denotes a second type optical recording medium. Reference numeral 201 denotes a first light source LD, and reference numeral 211 denotes a second light source LD. In this embodiment,
An example in which the optical pickup device is composed of “two types of optical pickups”: an optical pickup used for the first type optical recording medium 207 and an optical pickup used for the second type optical recording medium 217. It is. For the first type of optical recording medium (e.g. DVD), when the recording and reproducing or erasing of information is performed, the first light source LD201 is turned, the wavelength is emitted: the laser light flux of lambda ₁ is the first The coupling is performed by the coupling lens 202. The coupling lens 202 is an anamorphic lens having different lens functions in the major axis direction and the minor axis direction of the FFP of the laser beam emitted from the light source LD201.
The laser beam from the light source 01 is substantially collimated, and the cross-sectional shape of the coupled light beam is made substantially circular by a beam shaping function. The coupled light beam passes through the polarizing beam splitter 103 and
The light is converted into circularly polarized light by the wavelength plate 104, and the polarization prism 1
05, the optical path is bent by 90 degrees and is incident on the objective lens 206. By the action of the objective lens 206, the light is focused toward the first type optical recording medium 207, and the substrate of the optical recording medium 207 (thickness: t ₁ ). And condensed as an optical spot on the optical recording surface. The light beam reflected by the optical recording surface is
06, which is transmitted in the opposite direction to become a return light flux,
5 and transmitted through the quarter-wave plate 104, the polarization plane is turned 90 degrees from the initial polarization state, reflected by the polarization beam splitter 103, and transmitted through the cylinder lens 108 to astigmatism. The light enters the light receiving element 109 after being given an aberration. The output of the light receiving element 109 is input to a control unit 110 such as a microcomputer. The control means 110 generates a focus error signal by the astigmatism method and a track error signal by the push-pull method based on the input signal, and also generates a reproduction signal in the case of information reproduction. The focus error signal and the track error signal are applied to a servo system actuator (not shown), and the objective lens 20
Focusing and tracking are performed by the drive of 6.

When information is recorded / reproduced or erased from / to a second type of optical recording medium (eg, CD),
The second light source LD211 is turned on and emitted wavelength: λ
_{The two} laser beams are coupled by the second coupling lens 212. The coupling lens 212 is the same as the coupling lens 201, and includes a light source LD211.
While substantially collimating the laser beam from
The cross-sectional shape of the coupled light beam is shaped into a substantially circular beam. The coupled light beam passes through the polarizing beam splitter 213, is converted into circularly polarized light by the 波長 wavelength plate 214, and is incident on the objective lens 216.
Converged toward the seed optical recording medium 217 and the optical recording medium 2
The light passes through the substrate No. 17 (thickness: t ₂ ) and is focused on the optical recording surface as a light spot.

The light beam reflected by the optical recording surface is reflected by the objective lens 21.
The reflected light is transmitted through the quarter-wave plate 214, reflected by the polarization beam splitter 213, transmitted through the cylinder lens 218, given astigmatism by the astigmatism, and enters the light receiving element 219. The output of the light receiving element 219 is input to the control unit 110 to generate a focus error signal and a track error signal, and also generate a reproduction signal in the case of reproducing information. The focus error signal and the track error signal are applied to a servo system actuator (not shown), and focusing and tracking are performed by driving the objective lens 216 by the actuator. In the embodiment shown in FIG. 1, one of the two types of optical pickups is disposed in the active position depending on whether the first type optical recording medium 207 or the second type optical recording medium 217 is used. And the other is evacuated from the working position. Further, the deflecting prism 105 may be omitted depending on the layout of the optical system, and a deflecting prism may be provided between the quarter-wave plate 214 and the objective lens 216. The control means common to the two systems of optical pickups may be provided separately for each optical pickup.

That is, the optical pickup device shown in FIG. 1 according to the embodiment has _first substrate thicknesses t ₁ and t ₂ different from each other.
An optical pickup device for performing at least one of recording, reproducing, and erasing of information on a seed and a second kind of optical recording media 207 and 217, wherein first and _second light emitting wavelengths: λ ₁ and λ ₂ are different from each other. , Light source LDs 201 and 211, and coupling lenses 202 and
212, objective lenses 206 and 216 for condensing each coupled light beam as an optical spot on the optical recording surface of the corresponding optical recording medium, and reflected by the optical recording media 207 and 217, the objective lenses 206 and 216 Optical path separating optical means 103, 104 and 213, 214 for separating each light flux returned as a light flux from the irradiation light paths from the light sources LD 201, 211 to the objective lenses 206, 216.
Detecting means 108 and 109 for receiving each light beam separated by the optical path separating optical means and detecting information on the reflected light beam.
And 218 and 219, and a control unit 110 that performs focusing control and tracking control based on the detection result of the detection unit.
Only when the kind of optical recording medium 207 is used, the second light source LD 211 is turned on.
The coupling lenses 202 and 212 are anamorphic lenses having different lens functions depending on the direction in which the divergence angle of the incident light beam is maximized and the direction in which the divergence angle of the incident light beam is minimized. It is configured to have a function of substantially collimating a light beam from the LD and a function of beam shaping (claim 1). Further, for the first light source LD201, the first coupling lens 202, the first objective lens 206, the first optical path separating optical units 103 and 104, and the first detecting units 108 and 109.
Are combined, and the second coupling lens 212 and the second objective lens 21 are provided for the second light source LD211.
6. The second optical path separating optical means 213 and 214 and the second detecting means 218 and 219 are combined, and the first and second coupling lenses 202 and 212 are of the same type (claim). Item 2). In the embodiment shown in FIG. 1, "the same kind of optical element" including a coupling lens can be used for two systems of optical pickups.

The embodiment shown in FIG. 2 is an "example in which parts other than the light source LD and the objective lens are shared". In order to avoid complication, the same reference numerals as those in FIG. When recording / reproducing or erasing information from / to a first type optical recording medium 207 such as a DVD, for example, the first light source LD 201 is arranged in a combined configuration with the coupling lens 202 as shown in FIG. At the same time, the objective lens 206 is arranged in the use state shown in the figure. When the light source LD201 is turned on, the emitted laser beam of wavelength: λ ₁ is coupled by the coupling lens 202 to become a parallel beam having a substantially circular beam cross section, and the polarization beam splitter 1
03, is converted into circularly polarized light by the quarter-wave plate 104A, and the optical path is bent by 90 degrees by the deflecting prism 105 to enter the objective lens 206. The first type of optical recording medium is operated by the objective lens 206. The light is converged toward 207, passes through the substrate (thickness: t ₁ ) of the optical recording medium 207, and is condensed as a light spot on the optical recording surface. The light beam reflected by the optical recording surface becomes a return light beam through the objective lens 206, is reflected by the deflecting prism 105, and is
4A, is reflected by the polarizing beam splitter 103, is transmitted through the cylinder lens 108, is given astigmatism, and is incident on the light receiving element 109. The output of the light receiving element 109 is input to the control means 110, and generates a focus error signal by the astigmatism method and a track error signal by the push-pull method. In the case of information reproduction, a reproduction signal is also generated. The focus error signal and the track error signal are applied to a servo system actuator (not shown), and focusing and tracking are performed by driving the objective lens 206 by the actuator.

A second type optical recording medium 21 such as a CD
7, when information is recorded / reproduced or erased, the second light source LD211 is connected to the coupling lens 20.
2 and the objective lens 2
Deploy 16 in use. Objective lenses 206, 216
Switching and focusing / tracking for each lens can be performed by using a twin lens actuator (optical technology contact Vol. 33. No. 11 (1995)) which is known for a twin lens type DVD optical pickup.
61 pages or less). Second light source LD
When the lamp 211 is turned on, the emitted laser beam having a wavelength of λ ₂ is coupled by the coupling lens 202, collimated and beam-shaped, passes through the polarization beam splitter 103, and passes through the quarter-wave plate 104A.
Is converted into circularly polarized light and enters the objective lens 216,
The light is converged toward the second type optical recording medium 217, passes through the substrate (thickness: t ₂ ) of the optical recording medium 217, and is condensed as an optical spot on the optical recording surface. The light beam reflected by the optical recording surface becomes a return light beam through the objective lens 216, passes through the quarter-wave plate 104A, is reflected by the polarization beam splitter 103, and is given astigmatism by passing through the cylinder lens 218. The light enters the light receiving element 219. The output of the light receiving element 219 is input to the control unit 110 to generate a focus error signal and a track error signal, and also generate a reproduction signal in the case of reproducing information. The focus error signal and the track error signal are applied to a servo system actuator (not shown), and focusing and tracking are performed by driving the objective lens 216 by the actuator. That is, the optical pickup device of the embodiment shown in FIG. 2 records and reproduces information on the first and second types of optical recording media 207 and 217 having different substrate thicknesses t ₁ and t ₂ from each other. An optical pickup device for performing at least one erasing operation, wherein first and second light sources LD 201 and 211 having different emission wavelengths: λ ₁ and λ ₂ , and a coupling lens for coupling a light beam from each light source LD; 202, objective lenses 206 and 216 for condensing each coupled light beam as an optical spot on the optical recording surface of the corresponding optical recording medium, and reflected by the optical recording media 207 and 217, via the objective lenses 206 and 216. Optical path separating optical means 103 and 104A for separating the returned light fluxes from the irradiation light paths from the light sources LD 201 and 211 to the objective lenses 206 and 216; There are detecting means 108 and 109 for receiving each light beam separated by the path separating optical means and detecting information of the reflected light beam, and a control means 110 for performing focusing control and tracking control based on the detection result of the detecting means. And the first light source LD20
1 is turned on only when the first type optical recording medium 207 is used, the second light source LD211 is turned on only when the second type optical recording medium 217 is used, and the coupling lens 202 is An anamorphic lens having different lens functions depending on the direction in which the divergence angle becomes the maximum and the direction in which the divergence angle becomes the minimum, and has a function of substantially collimating the light beams from the first and second light sources LD and a function of beam shaping. (Claim 1). In addition, the optical pickup device of FIG. 2 includes first and second light sources LD20.
1 and 211, at least the coupling lens 2
02 is shared (claim 2). In the embodiments shown in FIGS. 1 and 2, if there is a margin in the light amount of the light sources LD 201 and 211, the polarization beam splitter 10
Instead of 3, 213, a normal beam splitter may be used. In this case, of course, the 1/4 wavelength plate 1
04, 114 and 104A are unnecessary. The quarter-wave plate 104A used in the embodiment shown in FIG. 2 functions as a quarter-wave plate for lights having different wavelengths: λ ₁ and λ ₂ . Such a wave plate has a wavelength: λ ₁ ,
A thin film is formed using a birefringent material in which the “difference in the refractive index for each polarized light component” with respect to the light of λ ₂ is Δn ₁ and Δn ₂ , respectively. As integers, Δn ₁ · D = {j + (1/4)} · λ ₁ , Δn ₂ · D = {k + (1/4)} ·
λ ₂ can be realized.

[0015] The embodiment shown in FIG.
Optical path merging means 301 and 302 for merging the optical paths of the first and second light sources LD with the coupling lens 202 shared by the light sources LD 201 and 211 (claim 4). This is an example in which the coupling lens 202, the optical path separating optical unit 301, and "at least a part of the detecting unit" are shared by the two light sources LD 201 and 211 (claim 6). First-type optical recording medium 207
When recording / reproducing or erasing information with respect to the first light source LD201, the first light source LD201 is turned on. Light source LD20
A laser beam having a wavelength: λ ₁ radiated from the beam splitter ₁ is reflected by the beam splitter 302 and is coupled to the coupling lens 20.
The light is coupled by the light source 2 into a parallel light beam having a substantially circular light beam cross section. The light path is bent by 90 degrees by the deflecting prism 105 and is incident on the objective lens 206. The light is converged toward the recording medium 207 and the substrate of the optical recording medium 207 (thickness: t
₁ ) The light is transmitted and condensed as an optical spot on the optical recording surface. The light beam reflected by the optical recording surface becomes a return light beam through the objective lens 206, is reflected by the deflecting prism 105, passes through the coupling lens 202, becomes a focused light beam, passes through the beam splitter 302, and passes through the beam splitter 30.
The light is reflected by 1, is given astigmatism by the cylinder lens 108, passes through the beam splitter 220, and enters the light receiving element 109. The output of the light receiving element 109 is input to control means (not shown). The control means generates a focus error signal by the astigmatism method and a track error signal by the phase difference method, and also generates a reproduction signal in the case of information reproduction. The focus error signal and the track error signal are applied to a servo system actuator (not shown), and focusing and tracking are performed by driving the objective lens 206 by the actuator.

When recording / reproducing or erasing information from / to the second type optical recording medium 217, the objective lens 2
17 is in the use position. Objective lenses 206, 21
The switching, focusing and tracking of No. 6 are performed using the twin lens actuator. Second light source L
When D211 is turned on, the emitted laser beam of wavelength: λ ₂ passes through the beam splitters 301 and 302, is coupled by the coupling lens 202, is collimated and beam-shaped, and is deflected.
5, the light enters the objective lens 216, is focused toward the second type of optical recording medium 217, passes through the substrate (thickness: t ₂ ) of the optical recording medium 217, and forms an optical spot on the optical recording surface. Collect light. The light beam reflected by the optical recording surface is
6, the reflected light beam is reflected by the deflecting prism 105, passes through the coupling lens 202, becomes a focused light beam, passes through the beam splitter 302, is reflected by the beam splitter 301, and gives astigmatism by the cylinder lens 108. The light is reflected by the beam splitter 220 and enters the light receiving element 219. Light receiving element 219
Is output to a control means (not shown), which generates a focus error signal by the astigmatism method and a track error signal by the phase difference method, and also generates a reproduction signal in the case of information reproduction. The focus error signal and the track error signal are applied to an actuator of a servo system (not shown), and the objective lens 2
Focusing and tracking are performed by driving the 16. That is, in this embodiment, the first and second
In addition to the coupling lens 202 and the optical path separating optical unit 301, the cylinder lens 108 and the beam splitter 220 that are a part of the detecting units 108, 220, 109, and 219 are shared by the light sources LD 201 and 211 (claim). Item 6). As the beam splitter 220, a “dichroic filter film” is used as a beam separation film, and the dichroic filter film transmits a light beam having a wavelength of λ ₁ and reflects a light beam having a wavelength of λ _2. In addition, it is possible to increase the amount of light flux incident on the light receiving elements 109 and 219.

The embodiment shown in FIG.
Optical path merging means 303 for merging the optical paths of the first and second light sources LD with the coupling lens 202 shared by the light sources LD 201 and 211 (claim 4);
An example in which the detection means 231 and 232 are shared with the first and second light sources LD 201 and 211 together with the coupling lens 202 and the optical path separation optical means 230 (claim 6), and the objective lens 26 is further shared. It is.
That is, in this embodiment, the objective lens 26 is “wavelength: λ
_The parallel light flux incident at ₁ is collected as a good light spot on the optical recording surface of the optical recording medium 207, and the parallel light flux incident at a wavelength of λ ₂ is collected as a good light spot on the optical recording surface of the optical recording medium 217. It is designed to "light." For this reason, the objective lens 26 is provided on the optical recording medium 20 having a small substrate thickness.
The optical characteristics for lambda _1, a wavelength is used on a thick optical recording medium 217 of the substrate thickness: wavelength used 6 is set above the optical characteristics for lambda ₂ (Claim 5).

In FIG. 4A, when recording / reproducing or erasing information on / from the first type optical recording medium 207, the first light source LD201 is turned on. Light source LD
A laser beam having a wavelength of λ ₁ radiated from the laser beam 201 passes through the beam splitter 303 and is coupled to the coupling lens 202.
Into a parallel light beam having a substantially circular light beam cross section, passes through the beam splitter 230, is bent by 90 degrees in the optical path by the deflecting prism 105, enters the objective lens 26, and is acted upon by the action of the objective lens 26. Are focused toward the optical recording medium 207 and the optical recording medium 2
07 and converge as a light spot on the optical recording surface. The light flux reflected by the optical recording surface becomes a return light flux via the objective lens 26, is reflected by the deflecting prism 105,
The light is reflected by the beam splitter 230 and enters the light receiving element 232 via the hologram element 231. The hologram element exerts a lens action and a diffraction action on the transmitted light beam. The above-mentioned lens action is “an action that gives astigmatism”. When recording / reproducing or erasing information on / from the second type optical recording medium 217, the second light source LD201 is turned on. The laser beam of wavelength: λ ₂ emitted from the light source LD 211 is a beam splitter 303.
And is coupled by the coupling lens 202 to become a parallel light beam having a substantially circular light beam cross section, passes through the beam splitter 230, is bent by 90 degrees in the optical path by the deflecting prism 105, and enters the objective lens 26. Then, the optical recording medium 21
7 and converges as a light spot on the optical recording surface through the substrate of the optical recording medium 217. The light beam reflected by the optical recording surface becomes a return light beam through the objective lens 26, is reflected by the deflection prism 105, is reflected by the beam splitter 230, and is incident on the light receiving element 232 through the hologram element 231. The light receiving element 232 is the same as that shown in FIG.
As shown in (b), the two quadrant light receiving sections 2321 and 2321 are provided.
322 are formed in parallel. Since the diffraction effect of the hologram element 231 differs depending on the wavelength,
Return light beams having wavelengths of λ ₁ and λ ₂ are given astigmatism, respectively, and enter the four-divided light receiving sections 2321 and 2322, respectively. The output of each of the four divided light receiving units is input to a control unit (not shown) to generate a focus error signal by an astigmatism method and a focus error signal by a push-pull method. In the case of information reproduction, a reproduction signal is also generated. The focus error signal and the track error signal are applied to a servo system actuator (not shown), and focusing and tracking are performed by driving the objective lens 206 by the actuator. In FIG. 4B, reference characters L1,
L2 indicates a light beam cross-sectional shape (an elliptical shape due to a focus error) of the return light beam incident on the four-divided light receiving unit. In the embodiment of FIG. 4, the beam splitter 3
03, a light beam of wavelength: λ ₁ is transmitted, and a wavelength of λ ₂
By using the one having the dichroic filter film that reflects the light beam of the above, the light beams from the respective light sources LD can be combined with the light paths with high light use efficiency. Further, the beam splitter 230 is a polarization beam splitter, and the above-described 1 is disposed between the splitter 230 and the objective lens 26.
The 波長 wavelength plate 104A may be used, so that light loss in the beam splitter 230 can be eliminated. When the objective lens 26 is shared by the two light sources LD as in this embodiment, the numerical aperture of the objective lens 26 is switched according to the wavelengths used: λ ₁ and λ ₂ (for example, DVD). For N
A = 0.6, NA = 0.5 with respect to CD, etc.). This is because, for example, an aperture limiting element as disclosed in Japanese Patent Application Laid-Open No. It should be deployed on the side. Needless to say, the detecting means in the embodiment of FIG. 3 can be replaced by the detecting means in the embodiment of FIG.

FIG. 5 shows an embodiment of the optical pickup device according to the seventh aspect. As shown in FIG. 5A, in this embodiment, a first light source LD21 in the form of a chip, a first light receiving element 31 for receiving a return light beam from the first type of optical recording medium 207, First light source LD21
Hologram element 4 that transmits the light flux from the first light source and diffracts the return light flux toward the first light receiving element 31
1 in the same can 51 to form a single unit, and a chip-shaped second light source LD22,
A second light receiving element 32 that receives the return light beam from the second type optical recording medium 217, transmits the light beam from the second light source LD22, and diffracts the return light beam toward the second light reception element 32. By providing the second hologram element 42 on the same can 52, a single unit is obtained. When recording / reproducing or erasing information on / from the first type optical recording medium 207, the first light source LD21 is turned on. The laser beam having a wavelength of λ ₁ emitted from the light source LD 21 is supplied to the hologram element 41 and the beam splitter 30.
And a quarter-wave plate 104A, and are coupled by a coupling lens 202 to become a parallel light beam having a substantially circular light beam cross section. The light path is bent by 90 degrees by a deflecting prism 105 and enters the objective lens 26. Then, the light is converged toward the optical recording medium 207 by the action of the objective lens 26 and condensed as a light spot on the optical recording surface of the optical recording medium 207. The light beam reflected by the optical recording surface is
, Is reflected by the deflecting prism 105, passes through the coupling lens 202, becomes a converged light beam, and is transmitted through the quarter-wave plate 104A so that the deflecting surface is turned by 90 degrees from the initial state to form a beam. Splitter 3
0 is transmitted, and enters the light receiving element 31 under the diffraction effect of the hologram element 41. Second type optical recording medium 217
The first light source LD22 is turned on when recording / reproducing or erasing information with respect to the data. The laser beam of wavelength: λ ₂ emitted from the light source LD 22 is
, Is reflected by the beam splitter 30, passes through the 波長 wavelength plate 104 </ b> A, is coupled by the coupling lens 202, becomes a parallel light having a substantially circular light beam cross section, and passes through the deflecting prism 105. The light enters the objective lens 26, is converged toward the optical recording medium 207 by the action of the objective lens 26, and is condensed as a light spot on the optical recording surface of the optical recording medium 217. The light beam reflected by the optical recording surface becomes a return light beam through the objective lens 26, is reflected by the deflecting prism 105, passes through the coupling lens 202 to become a focused light beam, passes through the quarter-wave plate 104A, and is polarized as initially. Are orthogonal to each other, are reflected by the beam splitter 30 and are incident on the hologram element 42, and are incident on the light receiving element 32 due to the diffraction effect of the hologram element 42. That is, in the embodiment shown in FIG. 5A, the first and second light sources LD21 and LD22 are
The coupling lens 202 is shared (claim 3),
There is provided an optical path merging means 30 for merging the optical paths of the first and second light sources LD with the coupling lens 202 (claim 4). Further, the objective lens 26 is shared by the first and second light sources LD21 and LD22, and the optical characteristics of the objective lens 26 with respect to the wavelength used for the optical recording medium 207 having a small substrate thickness are as follows. Thick optical recording medium 2
The optical characteristics are set to be equal to or higher than the optical characteristics with respect to the wavelength used in claim 17 (claim 5). The beam splitter 30 as an optical path merging means also functions as an optical path separating optical means. Beam splitter 30 is, in this example wavelength is transmitted through the lambda ₁ of the light beam, wavelength: but those having a dichroic filter film for reflecting the lambda ₂ light fluxes is not limited thereto, using conventional beam splitter Is also good. Further, the beam splitter 30 may be a polarization beam splitter. In this case, the return light having the wavelength: λ ₁ may be detected by the light receiving element 32, and the return light having the wavelength: λ ₂ may be detected by the light receiving element 31. The hologram elements 41 and 42 are polarization holograms, and have different hologram functions depending on the polarization direction of the incident light beam. OPlu as a polarization hologram
sE March 1991, page 86 et seq., LiNb
The O ₃ was used and "polarization hologram element" can appropriately utilize what is known as "high density dual Bragg gratings for the magneto-optical head" described in the optical Vol. 20 No. 8 (August 1991) . It is also possible to use a polarization hologram using a birefringent thin film developed recently.

That is, in the embodiment shown in FIG. 5A, the hologram elements 41 and 42 are polarization holograms, and each of the hologram elements 41 and 22 is directed to the polarization plane of the light beam traveling from the light source LD 21 or 22 to the optical recording medium 207 or 217. There is a quarter-wave plate 104A for rotating the polarization plane of the return light beam by 90 degrees (claim 9).

Taking the hologram polarizing element 41 as an example, the hologram polarizing element 41 has three hologram areas A, B and C as shown in FIG. 5B. The holograms forming the hologram areas A, B, and C are polarization holograms, and transmit the light beam emitted from the light source LD21 as it is without exerting a hologram effect. The hologram element 41 becomes a return light beam.
The light flux returning to is diffracted by the hologram function of the hologram element 41 because the polarization plane is rotated by 90 degrees from the beginning. As shown in FIG. 5C, the light receiving element 31 has light receiving units E and F divided into two and light receiving units G and H separated from each other. The return light beam portion diffracted by the hologram area A of the hologram element 41 is condensed on the boundary between the light receiving portions E and F while being condensed by the action of the coupling lens 201. Therefore, a “focus error signal by the knife edge method” can be generated based on the difference between the outputs of the light receiving units E and F. The return beam portion diffracted by the hologram regions B and C is received by the light receiving element 31.
Are focused on the light receiving sections G and H, respectively. A “track error signal” can be generated based on the difference between the outputs of the light receiving units G and H. In addition, a reproduced signal can be generated by the output sum of the light receiving units E, F, G, and H (or the sum of some of them). The output of each light receiving unit is input to control means (not shown) to generate each of the above-mentioned signals, and the focus error signal / track error signal is applied to an actuator of a servo mechanism (not shown) for focusing / tracking. The hologram element 42 and the light receiving element 32 are the same as the hologram element 41 and the light receiving element 31, and the signal generation based on them is performed in the same manner as described above.

FIG. 6 shows an example of the configuration of a single unit combining a light source LD, a hologram element and a light receiving element. As shown, a casing 500 includes a light source LD50 and a hologram element 51 which is a polarization hologram.
, A transparent plate 52 and a light receiving element 53 are assembled.
The hologram element 51 is a polarization hologram as shown in FIG. 5B, and the light receiving element 53 has a light receiving section as shown in FIG. 5C. The laser beam emitted from the light source LD50 passes through the transparent plate 52 and the hologram element 51 and is emitted. The return light beam is diffracted by the hologram element 51, and the oblique side portion 52A formed on a part of the transparent plate 52 is formed.
(Reflected film is formed as a reflective surface) and is incident on the light receiving element 53. FIG. 7 schematically shows an embodiment of the optical pickup device according to claim 8.

The chip-shaped first and second light sources LD21,
22, a light receiving element 33 for receiving in common the return light beam from the first type optical recording medium 207 and the return light beam from the second type optical recording medium 217, and transmitting the light beam from each light source LD and returning each light beam. The hologram element 43 that diffracts the light beam toward the light receiving element 33 is incorporated into the same can to form a single unit. First type optical recording medium 20
For recording / reproducing or erasing information with respect to 7, the first light source LD21 is turned on. Light source LD21
Wavelength emitted from: laser light flux of lambda ₁ is transmitted through the hologram element 43, is coupled to become a parallel beam having a substantially circular light beam cross section by a coupling lens 202, passes through the 1/4-wave plate 104A Then, the light enters the objective lens 26 via the deflecting prism 105 and is condensed as a light spot on the optical recording surface of the optical recording medium 207 by the action of the objective lens 26. The light beam reflected by the optical recording surface becomes a return light beam via the objective lens 26,
The light is reflected at 05, passes through the 波長 wavelength plate 104A, turns the deflecting surface 90 degrees from the initial state, passes through the coupling lens 202, becomes a focused light beam, and passes through the hologram element 43. The hologram element 43 is shown in FIG.
This is a polarization hologram similar to that described with reference to FIG. The returning light beam is diffracted by the diffraction action of the hologram element 43 and enters the light receiving element 33. When recording / reproducing or erasing information on / from the second type optical recording medium 217, the second light source LD22 is turned on. Light source LD
The laser beam of wavelength: λ ₂ emitted from 22 passes through hologram element 43 and is coupled by coupling lens 202 to become a parallel beam having a substantially circular beam cross section. The transmitted light is incident on the objective lens 26 via the deflecting prism 105, and is condensed as a light spot on the optical recording surface of the optical recording medium 217 by the action of the objective lens 26. The luminous flux reflected by the optical recording surface becomes a return luminous flux via the objective lens 26, is reflected by the deflecting prism 105, passes through the coupling lens 202 via the 波長 wavelength plate 104A, and becomes a converged luminous flux to pass through the hologram element 43. The light is transmitted, diffracted by the element 43, and enters the light receiving element 33. The 波長 wavelength plate 104A may be formed on the substrate of the hologram element 43. The light receiving element 33 is the same as that described with reference to FIG. 5C, and as shown in FIG.
F ′ and light receiving sections G ′ and H ′ separated from each other. The return beam portion diffracted by the hologram element 43 is separated into three portions, and while being condensed by the action of the coupling lens 201,
Part of the light is collected on the boundary between the light receiving portions E 'and F'. A “focus error signal by the knife edge method” is generated based on the difference between the outputs of the light receiving units E ′ and F ′. The other two portions of the diffracted light beam are condensed on the light receiving portions G 'and H', respectively. Light receiving section G,
A “track error signal” is generated by the difference between the outputs of H. A reproduced signal can be generated by the output sum of the light receiving units E ′, F ′, G ′, and H ′ (or a sum of some of them). The output of each light receiving unit is input to control means (not shown) to generate each of the above-mentioned signals, and the focus error signal / track error signal is applied to an actuator of a servo mechanism (not shown) for focusing / tracking. Since the diffraction effect of the hologram element 43 depends on the wavelength, the focus position of the return light beam incident on the light receiving element 43 is, as shown in FIG. 7B, the wavelengths of the return light beams λ ₁ and λ _2.
Deviate from each other according to Light receiving units E ', F', G ', H'
Is set to such a size as to be able to receive the return light beam of each wavelength in consideration of the shift of the light condensing position. As in this embodiment, by integrating the first and second light sources LD and the light receiving element that receives the return light beam of the laser light beam emitted therefrom together with the hologram element,
The light source and detection means can be simplified and made compact.

[0024]

EXAMPLES Specific examples will be described below. In each of the embodiments described below, the emission wavelength of the first light source LD:
λ ₁ = 635 nm, emission wavelength of the second light source LD: λ ₂ = 785 nm. Substrate thickness of first optical recording medium: t ₁ = 0.6 mm, second
The thickness of the substrate of the optical recording medium is t ₂ = 1.2 mm.
2).

In each embodiment, the same coupling lens is used for the first and second light sources LD individually or in common, and the objective lens is used for the first and second light sources LD. An individually optimized one is used. Therefore, Example 1 and Example 2 described below can be specific examples of the embodiment described with reference to FIGS. In each embodiment, the coupling lens is a single lens made of a single glass material (Claim 10), and both surfaces of the coupling lens are aspherical (Claim 11). In the following description, the direction of the optical axis in the coupling lens and the objective lens is defined as the Z direction, the major axis direction in the FFP of the laser beam from the light source LD is defined as the X direction, and the minor axis direction is defined as the Y direction. Example 1 Coupling lens Refractive index of glass material: n ₆₃₅ (wavelength: λ ₁ = 635 nm) = 1.72687
9, n ₇₈₅ (wavelength: λ ₂ = 785 nm) = 1.718770, thickness on the optical axis of the lens: 5.9144 mm Both surfaces of the coupling lens are aspherical surfaces, and each surface is represented by the following equation (1). . Z = (R _X X ² + R _Y Y ² ) / [1 + √ {1- (1 + K _X ) R _X ² X ^2- (1 + K _Y ) R _Y ² Y ² } + A _R [(1 -A _P ) X ² + (1 + A _P ) Y ² ] ² + B _R [(1-B _P ) X ² + (1 + B _P ) Y ² ] ³ + C _R [(1-C _P ) X ² + (1 + C _P ) Y ² ] ⁴ + D _R [(1-D _P ) X ² + (1 + D _P ) Y ² ] ⁵ (1) where Z is a lens in the optical axis direction. Surface coordinates, R _X ,
R _Y is the paraxial curvature of the lens surface in the ZX plane and ZY plane, respectively, K _X and K _Y are conical constants, and A _R , B _R , C _R , and D _R are
4 following a conical, sixth, eighth, rotationally symmetric element of the 10th order deformation _{coefficient, A P, B P, C} P, D P is the fourth-order conical, sixth,
Represents the non-rotationally symmetric components of the eighth and tenth order deformation coefficients. Since the radius of curvature is more general than the curvature as lens data, in the following data, a paraxial radius of curvature (reciprocal of curvature) is given instead of the paraxial radius of curvature. First surface (side of optical recording medium) 1 / R _X = 31.37083, 1 / R _Y = 6.444850, K _X = -6.55035, K _Y = 0.16
0280, A _R = -0.509955E-5, B _R = -0.119283E-5, C _R = 0.46660
1E-6, D _R = -0.360245E-7, A _P = -0.439089E + 1, _BP = 0.84191
5E + 0, C _P = 0.458520E + 0, D _P = 0.436494E-0 Second surface (light source LD side surface) 1 / R _X = -24.94260, 1 / R _Y = 5.62131, K _X = 0.839450, K _Y = 1.8
60382, A _R = -0.179779E-6, B _R = 0.480492E-7, C _R = -0.2501
00E-9, D _R = 0.144679E-6, A _P = 0.309997E + 2, B _P = -0.1742
37E + 1, C _P = 0.560766E + 1, D _P = 0.160343E-0 FIGS. 8A and 8B show the shape of the coupling lens in the XZ plane and the shape in the YZ plane and the coupling action.
(B). In the above, for example, “E-6” is changed to “10
~ ⁶ ", and this numerical value relates to the immediately preceding numerical value, and so on. The focal length of the coupling lens is X
Fx = 25 mm in the Z plane and fz = 30 mm in the YZ plane. Also, the entrance pupil of the coupling lens: 4.0 mm
The wavefront aberration (unit: λ) with respect to is as follows. Wavefront aberration (lambda ₁ = 635 nm) wave front aberration (lambda ₂ = 785 nm) angle (degree) X and Y directions X and Y directions 0.0 0.004 0.004 0.002 0.002 0.5 0.013 0.002 0.009 0.002 1.0 0.024 0.009 0.018 0.009 .

Objective lens combined with the first light source LD (first objective lens) Refractive index of glass material: n ₆₃₅ (wavelength: λ ₁ = 635 nm) = 1.72659
2. Thickness on the optical axis of the lens: 1.5mm The lens surface is aspherical on both sides, and Z direction (optical axis direction)
And a direction orthogonal as y-direction, a known equation ^{(2) Z = (y 2} / R) / [1 + √ {1- (1 + K) (y / R) 2} + A 4 y 4 + represented by ^{_{A 6 y 6 + A 8 y}} 8 + A 10 y 10 + A 12 y 12 + A 14 y 14 + ... (2). R is the paraxial radius of curvature, K is the conic constant, A ₄ ,
A ₆ , A ₈ , A ₁₀ , A ₁₂ , and A ₁₄ are higher order aspherical coefficients. 1st surface (light source LD side surface) R = 2.04808, K = -1.035674, A ₄ = 0.800204E-2, A ₆ = 0.5456
42E-4, A ₈ = 0.312394E-3, A ₁₀ = -0.242959E-3, A ₁₂ = 0.8
_{68334E-4, A 14 = -0.121603E} -4 a second surface (optical recording medium side) R = 124.76465, K = -10310.38073 , A 4 = 0.283742E-2, A 6 = -
0.164780E-2, A ₈ = 0.724141E-3, A ₁₀ = -0.162198E-3, A
₁₂ = 0.0, A ₁₄ = 0.0 Objective lens combined with the second light source LD (second objective lens) Refractive index of glass material: n ₇₈₅ (wavelength: λ ₂ = 785 nm) = 1.71877
0, Thickness on the optical axis of the lens: 1.5 mm The lens surface is aspherical on both surfaces, and is expressed by the above equation (2). First surface (side surface of light source LD) R = 2.01457, K = 0.103221, A ₄ = -0.906922E-2, A ₆ = -0.4288
_{85E-2, A 8 = 0.124844E} -2, A 10 = -0.553283E-3 a second surface (optical recording medium side) R = -9.55565, K = -235.507118 , A 4 = -0.219996E-1, A 6 = 0.19
0672E-1, A ₈ = -0.891788E-2, A ₁₀ = 0.164671E-2
.

A first objective lens is combined with the coupling lens to form a light beam (wavelength: λ) from the first light source LD.
₁ = 635 nm) on the optical recording surface of a first-type optical recording medium (substrate thickness: 0.6 mm) with an NA = 0.6, the wavefront aberration is 0.001λ on-axis, and the diffraction limit Is sufficient to obtain a light spot of Further, a second objective lens is combined with the coupling lens, and a light beam (wavelength: λ ₁ = 635 nm) from the second light source LD is optically recorded on a second type optical recording medium (substrate thickness: 1.2 mm). When a light spot is formed on the surface with NA = 0.5, the wavefront aberration is 0.001λ on the axis, which is sufficient to obtain a diffraction-limited light spot.

Example 2 Coupling lens Refractive index of glass material: n ₆₃₅ (wavelength: λ ₁ = 635 nm) = 1.72687
9, n ₇₈₅ (wavelength: λ ₂ = 785 nm) = 1.718770, thickness on the optical axis of the lens: 8.36862 mm Both surfaces of the coupling lens are aspherical surfaces, and each surface is represented by the above formula (1). First surface (side surface of optical recording medium) 1 / R _X = 62.86178, 1 / R _Y = 5.78511, K _X = −72.446826, K _Y = 0.
171136, A _R = -0.323481E-6, B _R = 0.571124E-9, C _R = -0.256
975E-6, D _R = -0.166469E-11, A _P = -0.279816E + 2, B _P = -0.25
5397E + 2, C _P = -0.141214E + 1, D _P = 0.514634E-1 Second surface (light source LD side surface) 1 / R _X = -10.02826, 1 / R _Y = 3.09780, K _X = 3.771989, K _Y = 0.6
78061, A _R = 0.445838E-6, B _R = -0.295592E-7, C _R = -0.1093
79E-9, D _R = 0.151651E-7, A _P = 0.361759E + 2, B _P = 0.1110
74E + 2, C _P = -0.179133E + 2, D _P = -0.117326E-1 The focal length of the coupling lens is within the XZ plane.
fx = 12.5 mm, and fz = 30 mm in the YZ plane. The wavefront aberration (unit: λ) with respect to the entrance pupil: 4.0 mm of the coupling lens is as follows. Wavefront aberration (lambda ₁ = 635 nm) wave front aberration (lambda ₂ = 785 nm) angle (degree) X and Y directions X and Y directions 0.0 0.007 0.007 0.004 0.004 0.5 0.013 0.005 0.009 0.004 1.0 0.025 0.015 0.017 0.013 .

Example 1 for the above coupling lens
And the first objective lens is combined, and the light flux (wavelength: λ ₁ = 635 nm) from the first light source LD is applied to the optical recording surface of the first type optical recording medium (substrate thickness: 0.6 mm) by NA = 0.6 light. When the spot is formed, the wavefront aberration is 0.003λ on the axis, which is sufficient to obtain a diffraction-limited light spot. Further, the coupling lens is combined with the second objective lens of the first embodiment, and the light flux (wavelength: λ ₁ = 635 nm) from the second light source LD is applied to the second type optical recording medium (substrate thickness: 1.2 mm). NA = 0.5 on the optical recording surface
When a light spot is formed by the above, the wavefront aberration is 0.00
3λ is sufficient to obtain a diffraction-limited light spot. FIGS. 9A to 9D show the image forming state from the light source LD to the optical recording surface in the XZ plane and the YZ plane in the second embodiment. (A) and (b) show the imaging state of the second light source LD, and (c) and (d) show the imaging state of the first light source LD.

[0030]

As described above, according to the present invention, one or more of information recording / reproducing / erasing can be performed on two types of optical recording media having different substrate thicknesses without a dedicated beam shaping means. An optical pickup device that can be favorably performed can be realized. Since the optical pickup device of the present invention has a coupling lens having a function of collimating the light beams from the first and second light sources D and shaping the beam,
Since a dedicated beam shaping means is not required, it can be realized at low cost, the coupled light beam becomes a parallel light beam, and there is no optical path bending due to beam shaping, so that the optical arrangement layout between the coupling lens and the objective lens is Large degree of freedom. According to the second aspect of the present invention, the same optical element including the coupling lens can be used in the two-system optical pickup, so that the cost can be reduced. According to the third and fourth aspects of the present invention, since the coupling lens is used in common for the first and second light sources LD, only one coupling lens is required, the cost is reduced, and the optical pickup device is compact. Is possible. Claim 5
In the invention described in the sixth aspect, the objective lens is shared by the first and second light sources LD, and the optical characteristics of the objective lens with respect to the wavelength used for the optical recording medium having a small substrate thickness are changed by the optical recording with a large substrate thickness. Since the optical characteristics are set to be higher than the optical characteristics with respect to the wavelength used for the medium, only one objective lens is required, so that the cost can be reduced and the optical pickup device can be made compact. According to the seventh and eighth aspects of the present invention, the optical pickup device can be made compact by unitizing the light source unit and the detection unit. According to the ninth aspect of the present invention, by using the polarization hologram, it is possible to make the optical pickup compact and to enhance the light use efficiency to enhance the reliability of the optical pickup device. According to the tenth aspect of the present invention, the coupling lens can be made compact, and according to the eleventh aspect of the present invention, good optical performance of the coupling lens can be realized. A twelfth aspect of the present invention provides a recording system of a conventionally known CD (CD-R or CD-R).
RW, etc.) and DVD.

[Brief description of the drawings]

FIG. 1 is a diagram for describing one embodiment of the present invention.

FIG. 2 is a diagram for explaining another embodiment of the present invention.

FIG. 3 is a diagram for explaining another embodiment of the present invention.

FIG. 4 is a diagram for explaining still another embodiment of the present invention.

FIG. 5 is a diagram for explaining still another embodiment of the present invention.

FIG. 6 is a diagram for explaining an example of unitizing a light source LD, a hologram element, and a light receiving element.

FIG. 7 is a diagram for explaining still another embodiment of the present invention.

FIG. 8 is a diagram illustrating a coupling action of the coupling lens in the first embodiment.

FIG. 9 is a diagram showing an image forming state in a combination of a coupling lens and each objective lens in Example 2.

[Explanation of symbols]

 201 First light source LD 211 Second light source LD 202, 212 Coupling lens 103, 213 Polarizing beam splitter 104, 214 Quarter wave plate 206, 216 Objective lens 207 First type optical recording medium 217 Second type Optical recording medium

Claims (12)

[Claims] A first type and a second type having different substrate thicknesses from each other.
Recording / reproducing / erasing information for various types of optical recording media
An optical pickup device for performing the above, comprising: a first light source LD and a second light source LD having different emission wavelengths; a coupling lens for coupling light beams from each light source LD; and each coupled light beam. An objective lens for condensing as an optical spot on an optical recording surface of the optical recording medium; and irradiating each light flux reflected by the optical recording medium and returned as a light flux through the objective lens from the light source LD to the objective lens. Optical path separating optical means for separating light from the optical path; detecting means for receiving each light beam separated by the optical path separating optical means and detecting information of a reflected light beam; focusing control and tracking based on the detection result of the detecting means Control means for performing control, wherein the first light source LD is turned on only when the first type of optical recording medium is used, and The light source LD is turned on only when the second type of optical recording medium is used, and the coupling lens is an anamorphic lens having different lens functions in a direction in which the divergence angle of the incident light beam is maximum and a direction in which the divergence angle is minimum. An optical pickup device comprising: a lens having a function of substantially collimating a light beam from the first and second light sources LD and a function of beam shaping. 2. The optical pickup device according to claim 1, wherein a first coupling lens, a first objective lens, a first optical path separating optical unit, and a first light source LD are provided for the first light source LD.
And a second coupling lens, a second objective lens, a second optical path separating optical unit, and a second light source LD.
An optical pickup device, wherein the same type of lens is used as the first and second coupling lenses. 3. The optical pickup device according to claim 1, wherein at least a coupling lens is shared with the first and second light sources LD. 4. The optical pickup device according to claim 3, wherein an optical path of the first and second light sources LD is merged with a coupling lens shared by the first and second light sources LD. An optical pickup device characterized by having means. 5. The optical pickup device according to claim 1, wherein the objective lens is used in common for the first and second light sources LD, and is used for an optical recording medium having a smaller substrate thickness. An optical pickup device, wherein the optical characteristics of the objective lens with respect to the wavelength to be set are set to be equal to or higher than the optical characteristics with respect to the wavelength used for an optical recording medium having a thick substrate. 6. The optical pickup device according to claim 4, wherein a coupling lens and an optical path separating optical unit are shared with the first and second light sources LD, and at least one of the detecting units is provided. An optical pickup device having a common unit. 7. The optical pickup device according to claim 1, wherein: a first light source LD; a first light receiving element for receiving a return light beam from the first type of optical recording medium; A first hologram element that transmits the light beam from the first light source LD and diffracts the return light beam toward the first light receiving element is formed into a single unit. A second light receiving element for receiving return light beams from the two types of optical recording media; and a second light receiving element for transmitting the light beam from the second light source LD and diffracting the return light beam toward the second light reception element. And a hologram element as a single unit. 8. The optical pickup device according to claim 6, wherein the first light source LD, the second light source LD, the return light flux from the first type optical recording medium and the light flux from the second type optical recording medium. A light characterized by comprising a light receiving element for receiving a return light beam in common and a hologram element for transmitting a light beam from each light source LD and diffracting each return light beam toward the light receiving element as a single unit. Pickup device. 9. The optical pickup device according to claim 7, wherein the hologram element is a polarization hologram, and the polarization plane of each return light beam is set at 90 degrees with respect to the polarization plane of the light beam from each light source LD toward the optical recording medium. An optical pickup device comprising a quarter-wave plate for turning. 10. The optical pickup device according to claim 1, wherein the coupling lens is made of a single kind of glass material. 11. The optical pickup device according to claim 1, wherein both surfaces of the coupling lens are aspherical. 12. The optical pickup device according to claim 1, wherein the first optical recording medium has a substrate thickness of 0.6 mm, and the second optical recording medium has a substrate thickness of 0.6 mm. An optical pickup device characterized by being 1.2 mm.