JP2004151659A - Polarizing optical element, method for manufacturing polarizing optical element, optical pickup device, and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing optical element which has superior light use efficiency and is small-sized and inexpensive. <P>SOLUTION: A 1st optical member 50b which has 1st unevenness formed on its one surface and a 2nd optical member 50c which has 2nd unevenness formed opposite the 1st unevenness are united together across a filling member 50e which has isotropy. Then at least one of the 1st and 2nd optical members is an optical member which has optical anisotropy, so optical characteristics can be realized nearly as designed by using a general optical member which is more inexpensive than usual. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polarizing optical element, a method for manufacturing a polarizing optical element, an optical pickup device, and an optical disk device. More specifically, a polarizing optical element used for an optical pickup device, a method for manufacturing the polarizing optical element, and the polarizing optical element And an optical disc device provided with the optical pickup device.
[0002]
[Prior art]
In an optical disc device, recording or erasing of information is performed by irradiating a recording surface of an information recording medium, such as an optical disc, on which spiral or concentric tracks are formed with laser light, and information is recorded based on reflected light from the recording surface. Playing and so on. The optical disc device includes an optical pickup device as a device for irradiating a recording surface of the information recording medium with a laser beam to form a light spot and receiving reflected light from the recording surface.
[0003]
In general, an optical pickup device includes an objective lens, and guides a light beam emitted from a light source to a recording surface of an information recording medium and guides a light beam (return light beam) reflected by the recording surface to a predetermined light receiving position. , And a light receiving element arranged at a light receiving position. The light receiving element outputs a signal including not only reproduction information of data recorded on the recording surface but also information (servo information) necessary for controlling the position of the optical pickup device itself and the objective lens.
[0004]
In order to correctly record data at a predetermined position on the recording surface or to correctly reproduce data recorded at a predetermined position on the recording surface, a light spot must be accurately formed at a predetermined position on the recording surface. For that purpose, it is necessary to accurately detect the formation position of the light spot. As a method for detecting the formation position of the light spot on the recording surface, a method using the return light flux of one light spot formed on the recording surface (single beam method) and a method using three light spots formed on the recording surface are used. The method can be broadly classified into a method using each return light beam (three-beam method). When the three-beam method is used, it is necessary to divide a light beam emitted from the light source into three (three-beam) in order to form three light spots on the recording surface. Therefore, in this case, a grating is generally used as an optical element for converting a light beam emitted from the light source into three beams.
[0005]
As an optical pickup device compatible with a three-beam method, an optical pickup in which the above-described grating and a hologram for branching a return light beam reflected by a recording surface from a common optical path of an outward path and a return path and guiding the same to the light receiving position are integrated. An apparatus has been proposed (for example, see Non-Patent Document 1). In the optical pickup device disclosed in Non-Patent Document 1, as shown in FIG. 23 (A), irregularities having a pitch of 1 to 2 μm are formed on one surface of a glass substrate GP for the hologram HM, and the other is formed. Asperities having a pitch of 10 to 20 μm are formed on the surface for the grating GT. When a return light beam (hereinafter also referred to as “branch return light beam” for convenience) that is branched by the hologram HM toward the light receiving surface of the light receiving element PD enters the grating GT, the return light beam is diffracted by the grating GT. The amount of light received by the PD is reduced. Therefore, the distance L between the hologram HM and the grating GT is set to about 2 mm in order to prevent the split return light beam from entering the grating GT. Further, as shown in FIG. 23B, by making the area of the grating GT smaller than the area of the hologram HM, it is possible to prevent the branched return light beam from being incident on the grating GT. As a result, the size of the optical pickup device was reduced.
[0006]
However, in the above optical pickup device, the light beam emitted from the light source LD is also subjected to the hologram effect by the hologram HM, so that the light amount (irradiation light amount) of the light beam condensed on the recording surface decreases. When the optical pickup device is used only for reproduction, there is no problem as long as an irradiation light amount of about 1 mW is sufficient, but when it is used for recording, an irradiation light amount of 10 to 20 mW is required. When the speed is high, there is an inconvenience that it is difficult to respond. Also, since the rewritable optical disk has a low reflectance, if the irradiation light amount is small, the light amount of the return light beam received by the light receiving element is insufficient, and the signal level and the S / N ratio of the output signal of the light receiving element are low. there were. That is, the light use efficiency was low.
[0007]
In order to improve these inconveniences, an optical head device using a polarization diffraction element having a different diffraction efficiency depending on the polarization direction of an incident light beam has been devised (for example, see Patent Document 1). In the optical head device disclosed in Patent Document 1, as shown in FIG. 24, a glass substrate GH having hologram irregularities formed thereon and a glass substrate GG having grating irregularities formed thereon are optically separated. A polarization diffraction element integrated so that each uneven surface faces each other via a filler (for example, liquid crystal) FM having anisotropy is used. Here, one of the two glass substrates has a refractive index substantially equal to the ordinary light refractive index (for example, 1.5) of the filler FM, and the other has an extraordinary light refractive index (for example, 1.8) of the filler FM. They have approximately equal refractive indices. Thereby, since the light beam emitted from the light source is not subjected to the hologram effect by the hologram, it is possible to suppress a decrease in the irradiation light amount. Further, in the hologram, since most of the return light beam is branched, the amount of light received by the light receiving element increases, and the signal level and the S / N ratio of the output signal of the light receiving element can be increased. That is, the light use efficiency can be improved. Further, even if the branched return light beam enters the grating, it is not diffracted in a direction different from that of the light receiving element, so that the distance between the hologram and the grating can be reduced.
[0008]
[Patent Document 1]
JP-A-10-68820 (Page 2-7, FIG. 1)
[Non-patent document 1]
Yukio Kurata and 8 others, "Hologram pickup for CD using three-beam method", Sharp Technical Report, Sharp Corporation, September 1989, Vol. 42, p. 45-52
[0009]
[Problems to be solved by the invention]
However, in the optical head device disclosed in Patent Document 1, since the refractive indices of the glass substrate GH and the glass substrate GG constituting the polarization diffraction element are each limited, it is difficult to use an inexpensive general-purpose glass substrate. (Especially, general-purpose glass substrates having a refractive index of 1.8 are generally difficult to obtain.) As a result, there is a disadvantage that the polarization diffraction element becomes expensive. Further, since the materials (particularly hardness) of the glass substrate GH and the glass substrate GG are different from each other, for example, in a manufacturing process of the polarization diffraction element, a predetermined process is performed after integrating the glass substrate GH, the liquid crystal FM, and the glass substrate GG. In a cutting operation for cutting out a polarization diffraction element having a shape and dimensions, it is necessary to change a processing tool (for example, a dicing saw) or change a processing condition (for example, a feed speed) in the middle of the operation. However, there is a disadvantage that the cost is reduced and the cost is increased.
[0010]
The present invention has been made under such circumstances, and a first object of the present invention is to provide a small and inexpensive polarizing optical element having excellent light use efficiency.
[0011]
A second object of the present invention is to provide a manufacturing method for manufacturing a small-sized polarizing optical element having excellent light use efficiency at low cost.
[0012]
A third object of the present invention is to provide an optical pickup capable of outputting a signal including information necessary for controlling the position of an optical pickup device itself and an objective lens with high accuracy without increasing the size and cost. It is to provide a device.
[0013]
It is a fourth object of the present invention to provide an optical disk device capable of accurately and stably accessing an information recording medium at a high speed.
[0014]
[Means for Solving the Problems]
The invention according to claim 1 is a polarizing optical element used in an optical pickup device, wherein the first optical member has first unevenness formed on one surface thereof; and the first optical member faces the first unevenness. A second optical member having second irregularities formed therein; and a filling member having optical isotropy filled between the first optical member and the second optical member. At least one of the first optical member and the second optical member is an optical member having optical anisotropy, and is a polarization optical element.
[0015]
According to this, the first optical member having the first unevenness formed on one surface thereof, and the second optical member having the second unevenness formed opposite to the first unevenness are optically coupled. They are integrated via an isotropic filling member. Further, since at least one of the first optical member and the second optical member is an optical member having optical anisotropy, it is substantially designed using a general-purpose optical member which is inexpensive as compared with the above-described conventional polarization diffraction element. Various optical characteristics can be realized. Therefore, miniaturization and cost reduction can be promoted without lowering the light use efficiency.
[0016]
In this case, various members can be considered as the filling member. However, as in the polarization optical element according to claim 2, the filling member may be an ultraviolet curable resin having adhesiveness. . In such a case, it is easy to adjust the positional relationship between the first optical member and the second optical member, and the first optical member and the second optical member can be bonded together with an accurate positional relationship.
[0017]
In each of the polarizing optical elements according to the first and second aspects, as in the polarizing optical element according to the third aspect, the filling member may be an adhesive for an optical lens. In such a case, since a general-purpose product can be used, the material cost of the filling member can be reduced.
[0018]
In each of the polarizing optical elements according to the first to third aspects, as in the polarizing optical element according to the fourth aspect, the pitch of the first unevenness is larger than the pitch of the second unevenness, and the first The area of the region where the irregularities are formed can be larger than the area of the region where the second irregularities are formed.
[0019]
In each of the polarizing optical elements according to claims 1 to 4, as in the polarizing optical element according to claim 5, the first optical member is a grating and the second optical member is a hologram. Can be.
[0020]
In each of the polarizing optical elements according to claims 1 to 5, as in the polarizing optical element according to claim 6, the first optical member and the second optical member each have an optical anisotropy. The optical anisotropy of the first optical member and the optical anisotropy of the second optical member may have a predetermined relationship. In such a case, the first optical member and the second optical member only need to have a predetermined relationship in their optical anisotropy. It can be used as a member and a second optical member.
[0021]
In this case, as in the polarization optical element according to claim 7, the extraordinary light refractive index of the first optical member and the ordinary light refractive index of the second optical member can be substantially equal to each other.
[0022]
In this case, the refractive index of the filling member is substantially equal to the extraordinary light refractive index of the first optical member or the ordinary light refractive index of the second optical member. be able to. In such a case, in the first optical member, the ordinary light component in the incident light beam is diffracted, but the extraordinary light component is transmitted as it is without being diffracted. In the second optical member, the extraordinary light component in the incident light beam is diffracted, but the ordinary light component is transmitted as it is without being diffracted.
[0023]
In each of the polarizing optical elements according to claims 6 to 8, as in the polarizing optical element according to claim 9, the first optical member and the second optical member have substantially the same optical anisotropy. The second optical member may be arranged so that its ordinary ray direction forms an angle of approximately 90 degrees with respect to the ordinary ray direction of the first optical member. Here, the “angle” means a magnitude of an angle formed by the directions, and is a concept that does not include the angle direction (positive or negative). In this specification, the term “angle” is used as such a concept.
[0024]
In this case, the materials of the first optical member and the second optical member may be different from each other. However, as in the polarization optical element according to claim 10, the first optical member and the second optical member may have different materials. The materials may be the same. In such a case, since the same member can be used as the first optical member and the second optical member, cost reduction can be promoted.
[0025]
In each of the polarizing optical elements according to claims 6 to 10, as in the polarizing optical element according to claim 11, the first optical member and the second optical member each include an organic stretched film. Can be. In such a case, fine processing can be performed accurately and easily, so that the yield is improved, and as a result, the cost can be reduced. Further, since the organic stretched film is inexpensive as compared with, for example, liquid crystal or the like, it is possible to promote a reduction in component cost. Furthermore, since the organic stretched film is in a sheet shape, it is possible to promote miniaturization.
[0026]
In each of the polarizing optical elements according to claims 6 to 11, as in the polarizing optical element according to claim 12, a first substrate that is disposed on the other side of the first optical member and holds the first optical member. And a second substrate that is arranged on a side of the second optical member opposite to the surface on which the second unevenness is formed, and that holds the second optical member.
[0027]
In this case, the first substrate and the second substrate may have the same thickness as each other, but as in the polarization optical element according to claim 13, the first substrate and the second substrate Alternatively, the thicknesses may be different from each other.
[0028]
In each of the polarizing optical elements according to Claims 12 and 13, as in the polarizing optical element according to Claim 14, the first substrate has a refractive index substantially equal to the ordinary light refractive index of the first optical member. The first optical member may be bonded via an agent. In such a case, for example, when the thickness of the adhesive layer is not uniform, the disorder of the planarity with respect to ordinary light at the bonding interface between the first optical member and the first substrate is corrected, and the light flux condensed on the recording surface is corrected. , It is possible to suppress the deterioration of the wavefront aberration.
[0029]
In each of the polarizing optical elements according to claims 12 to 14, as in the polarizing optical element according to claim 15, the second substrate has an adhesive having a refractive index substantially equal to the ordinary light refractive index of the second optical member. The second optical member may be bonded via an agent. In such a case, for example, when the thickness of the adhesive layer is non-uniform, the disorder of the flatness with respect to ordinary light at the bonding interface between the second optical member and the second substrate is corrected, and the light flux condensed on the recording surface is corrected. , It is possible to suppress the deterioration of the wavefront aberration.
[0030]
In each of the polarizing optical elements according to claims 12 to 15, as in the polarizing optical element according to claim 16, the first substrate and the second substrate can be made of substantially the same material. . In such a case, productivity can be improved and cost reduction can be promoted as compared with a case where the first substrate and the second substrate are made of different materials.
[0031]
In this case, the material of the first substrate and the material of the second substrate may be optical glass or transparent resin, respectively. In such a case, the cost of parts can be reduced.
[0032]
In each of the polarizing optical elements according to claims 12 to 17, as in the polarizing optical element according to claim 18, a third unevenness is formed on a surface of the first substrate opposite to the first optical member side. Can be formed.
[0033]
In this case, as in the polarization optical element according to claim 19, the third unevenness is an unevenness for a grating, and the third unevenness is optimized for a light flux having a wavelength different from that of the first unevenness. can do. In such a case, the present invention can be used for a so-called two-wavelength optical pickup device including two light sources that emit light beams having different wavelengths.
[0034]
In each of the polarizing optical elements according to claims 12 to 19, as in the polarizing optical element according to claim 20, a fourth unevenness is formed on a surface of the second substrate opposite to the side of the second optical member. Can be formed.
[0035]
In this case, as in the polarization optical element according to claim 21, the fourth unevenness is an unevenness for a hologram, and the fourth unevenness is optimized for a light beam having a wavelength different from that of the second unevenness. can do. In such a case, it can be used for a two-wavelength optical pickup device.
[0036]
In each of the polarizing optical elements according to claims 1 to 5, as in the polarizing optical element according to claim 22, the first optical member is an optical member having optical anisotropy, and the second optical member is May be an optical member having optical isotropy.
[0037]
In this case, the refractive index of the filling member may be substantially equal to the ordinary light refractive index or the extraordinary light refractive index of the first optical member.
[0038]
In each of the polarizing optical elements according to claims 22 and 23, as in the polarizing optical element according to claim 24, the refractive index of the filling member is different from the refractive index of the second optical member. it can.
[0039]
In each of the polarizing optical elements according to claims 22 to 24, as in the polarizing optical element according to claim 25, the first optical member can be formed of an organic stretched film. In such a case, fine processing can be performed accurately and easily, so that the yield is improved, and as a result, the cost can be reduced. Further, since the organic stretched film is inexpensive as compared with, for example, liquid crystal or the like, it is possible to promote a reduction in component cost. Furthermore, since the organic stretched film is in a sheet shape, it is possible to promote miniaturization.
[0040]
27. The polarizing optical element according to claim 22, wherein the third substrate is disposed on the other side of the first optical member and holds the first optical member, as in the polarizing optical element according to claim 26. May be further provided.
[0041]
In this case, as in the polarization optical element according to claim 27, the third substrate is attached to the first optical member via an adhesive having a refractive index substantially equal to the ordinary light refractive index of the first optical member. Can be combined.
[0042]
In each of the polarizing optical elements according to claims 26 and 27, as in the polarizing optical element according to claim 28, the second optical member and the third substrate are made of substantially the same material. it can. In such a case, productivity can be improved and cost reduction can be promoted as compared with the case where the second optical member and the third substrate are made of different materials.
[0043]
In each of the polarizing optical elements according to claims 26 to 28, as in the polarizing optical element according to claim 29, the second optical member and the third substrate can have different thicknesses from each other. .
[0044]
In each of the polarizing optical elements according to Claims 26 to 29, as in the polarizing optical element according to Claim 30, a fifth unevenness is formed on a surface of the third substrate opposite to the first optical member. Can be formed.
[0045]
In each of the polarizing optical elements according to claims 22 to 30, as in the polarizing optical element according to claim 31, the polarizing optical element is disposed on the side opposite to the surface on which the second unevenness is formed of the second optical member. And a fourth substrate having a different refractive index from the second optical member.
[0046]
In this case, as in the polarization optical element according to the thirty-second aspect, sixth irregularities may be formed on the surface of the fourth substrate opposite to the side of the second optical member.
[0047]
An invention according to claim 33 is a method for manufacturing a polarizing optical element used in an optical pickup device, wherein a first step of forming first irregularities on one surface of a first member having optical anisotropy. And a second step of forming second irregularities on one surface of the second member having optical anisotropy or optical isotropy; and so that the first irregularities and the second irregularities face each other. And a third step of bonding the first member and the second member via a filling member having an isotropic property.
[0048]
According to this, the first unevenness is formed on one surface of the first member having optical anisotropy (first step), and the second member having optical anisotropy or optical isotropy is formed. Second irregularities are formed on one surface (second step). Then, the first member and the second member are bonded via an isotropic filling member such that the first unevenness and the second unevenness face each other (third step). That is, since the first optical member is an optical member having optical anisotropy and the second optical member is an optical member having optical anisotropy or optical isotropy, the polarization diffraction in the prior art described above is performed. Using a general-purpose optical member that is inexpensive as compared with the element, it is possible to realize optical characteristics almost as designed. Therefore, it is possible to manufacture a small-sized polarizing optical element having excellent light use efficiency at low cost.
[0049]
In this case, as in the manufacturing method according to claim 34, prior to the first step, a fourth step of bonding the first member to a first substrate for holding the first member; and And a fifth step of bonding a second substrate for holding the second member and the second member. In such a case, for example, even if the first member and the second member are members that are easily deformed by an external force, they are held by the first substrate and the second substrate, respectively, so that workability in the subsequent steps is reduced. Can be suppressed.
[0050]
In this case, as in the manufacturing method according to claim 35, prior to the third step, a sixth step of forming third irregularities on a surface of the first substrate opposite to the first member is performed. It may further include.
[0051]
In each of the manufacturing methods according to claims 34 and 35, as in the manufacturing method according to claim 36, prior to the third step, a surface of the second substrate opposite to the side of the second member is provided with a second surface. The method may further include a seventh step of forming the four irregularities.
[0052]
An invention according to claim 37 is an optical pickup device that irradiates light onto a recording surface of an information recording medium and receives light reflected from the recording surface, comprising: a light source; and a light beam emitted from the light source. The polarization optics according to any one of claims 1 to 17, 22 to 29, and 31 arranged on an optical path of a light beam emitted from the light source toward the objective lens, the objective lens converging on the recording surface. An optical pickup device comprising: an element; an optical system for guiding a return light beam reflected by the recording surface to a predetermined light receiving position; and a photodetector arranged at the light receiving position.
[0053]
According to this, since the polarizing optical element according to any one of claims 1 to 17, 22 to 29, and 31 is provided, the optical pickup device itself and the optical pickup device can be manufactured without increasing the size and cost. It is possible to accurately output a signal including information necessary for controlling the position of the objective lens.
[0054]
An invention according to claim 38 is an optical pickup device that irradiates light onto recording surfaces of a plurality of types of information recording media and receives reflected light from the recording surfaces, wherein the plurality of information recording media are individually A plurality of light sources provided correspondingly to selectively emit light beams having different wavelengths; an objective lens for condensing each light beam emitted from the plurality of light sources on the recording surface; And the polarizing optical element according to any one of claims 18 to 21, 30, and 32, which is disposed on an optical path of a light beam toward the objective lens, and the return light beam reflected by the recording surface is subjected to a predetermined process. An optical pickup device comprising: an optical system for guiding to a light receiving position; and a photodetector disposed at the light receiving position.
[0055]
According to this, since the polarization optical element according to any one of claims 18 to 21, 30, and 32 is provided, the optical pickup device itself and the objective lens can be achieved without increasing the size and cost. It is possible to accurately output a signal including information necessary for the position control of the camera.
[0056]
In each of the optical pickup devices described in claims 37 and 38, as in the optical pickup device described in claim 39, the objective lens and the polarizing optical element can be integrated. In such a case, it is possible to prevent an offset component from being added to the output signal of the photodetector due to the shift of the objective lens.
[0057]
The invention according to claim 40 is an optical disc device that performs at least reproduction among information recording, reproduction, and erasure on an information recording medium, and the optical pickup according to any one of claims 37 to 39. An optical disc device comprising: a device; and a processing device that performs at least reproduction among recording, reproduction, and erasure of the information by using an output signal from the optical pickup device.
[0058]
According to this, based on the output signal from the optical pickup device according to any one of claims 37 to 39, an RF signal, a servo signal, and the like can be accurately and stably detected, and as a result, It is possible to accurately and stably perform at least high-speed access including information reproduction among information recording, reproduction, and erasure on an information recording medium. Furthermore, the miniaturization of the optical pickup device can promote the miniaturization of the optical disc device itself and the reduction of power consumption. For example, when the optical pickup device is used for portable use, it is easy to carry and can be used for a longer time. It becomes.
[0059]
BEST MODE FOR CARRYING OUT THE INVENTION
<< 1st Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
[0060]
FIG. 1 shows a schematic configuration of an optical disk device 20 according to the first embodiment of the present invention.
[0061]
The optical disk device 20 shown in FIG. 1 includes a spindle motor 22 for rotating and driving the optical disk 15, an optical pickup device 23, a laser control circuit 24, an encoder 25, a motor driver 27, a reproduction signal processing circuit 28, a servo controller 33, A buffer RAM 34, a buffer manager 37, an interface 38, a ROM 39, a CPU 40, a RAM 41, and the like are provided. Note that the arrows in FIG. 1 indicate typical flows of signals and information, and do not indicate all of the connection relationships of the respective blocks. In the first embodiment, an information recording medium conforming to the DVD standard is used for the optical disc 15 as an example.
[0062]
The optical pickup device 23 is a device for irradiating the recording surface on which the spiral or concentric tracks of the optical disk 15 are formed with laser light and receiving the reflected light from the recording surface. The configuration and the like of the optical pickup device 23 will be described later in detail.
[0063]
The reproduction signal processing circuit 28 detects a wobble signal, an RF signal, a servo signal (a focus error signal, a track error signal) and the like based on an output signal from the optical pickup device 23. Then, the reproduction signal processing circuit 28 extracts address information, a synchronization signal, and the like from the wobble signal. The address information extracted here is output to the CPU 40, and the synchronization signal is output to the encoder 25. Further, the reproduction signal processing circuit 28 performs error correction processing and the like on the RF signal, and then stores the RF signal in the buffer RAM 34 via the buffer manager 37. The servo signal is output from the reproduction signal processing circuit 28 to the servo controller 33.
[0064]
The servo controller 33 generates various control signals for controlling the optical pickup device 23 based on the servo signals, and outputs the generated signals to the motor driver 27.
[0065]
The buffer manager 37 manages the input and output of data to and from the buffer RAM 34, and notifies the CPU 40 when the accumulated data amount reaches a predetermined amount.
[0066]
The motor driver 27 outputs a drive signal to the optical pickup device 23 and the spindle motor 22 based on a control signal from the servo controller 33 and an instruction from the CPU 40.
[0067]
The encoder 25 extracts the data stored in the buffer RAM 34 through the buffer manager 37 based on an instruction from the CPU 40, modulates the data, adds an error correction code, and the like, and generates a write signal to the optical disk 15. At the same time, the write signal is output to the laser control circuit 24 in synchronization with the synchronization signal from the reproduction signal processing circuit 28.
[0068]
The laser control circuit 24 controls the output of a laser beam to be applied to the optical disc 15 based on a write signal from the encoder 25 and an instruction from the CPU 40.
[0069]
The interface 38 is a bidirectional communication interface with a host (for example, a personal computer) and conforms to a standard interface such as an ATAPI (AT Attachment Packet Interface) and a SCSI (Small Computer System Interface).
[0070]
The ROM 39 stores a program described in a code decodable by the CPU 40. The CPU 40 controls the operation of each of the above-described units according to a program stored in the ROM 39, and temporarily stores data and the like necessary for the control in the RAM 41.
[0071]
Next, the configuration and the like of the optical pickup device 23 will be described with reference to FIGS. 2 (A) to 7 (C).
[0072]
As shown in FIG. 2A, the optical pickup device 23 includes a light source unit 51, a polarization diffraction element 50 as a polarization optical element, a coupling lens 52, a λ / 4 plate 55, and a light receiver as a photodetector. 59, an objective lens 60, a drive system (a focusing actuator, a tracking actuator, and a seek motor (all not shown)) and the like.
[0073]
The light source unit 51 includes a semiconductor laser 51a as a light source that emits a light beam having a wavelength of 660 nm. Here, the maximum intensity emission direction of the light beam emitted from the semiconductor laser 51a (hereinafter also referred to as “emitted light beam” for convenience) is defined as the + X direction (rightward on the paper surface in FIG. 2A). In the first embodiment, as an example, the emitted light beam is assumed to be a P-polarized light beam.
[0074]
The polarization diffraction element 50 is disposed on the + X side of the light source unit 51. As shown in FIG. 2B, the polarization diffraction element 50 includes a first glass substrate 50a as a first substrate, a grating 50b as a first optical member, a filler 50e as a filler, and a second optical member. And a second glass substrate 50d as a second substrate.
[0075]
The grating 50b divides the emitted light beam into zero-order light and ± first-order diffracted light. As the material of the grating 50b, an organic stretched film having optical anisotropy (see JP-A-2000-075130) is used. Here, since the emitted light beam is a P-polarized light beam, as an example, the refractive index (ordinary refractive index) for a P-polarized light beam (ordinary light) is 1.6, and the refractive index (anomalous light) for an S-polarized light beam (extraordinary light) An organic stretched film having a refractive index of 1.5 (hereinafter, referred to as “first organic stretched film” for convenience) is used. Then, irregularities having a pitch of 10 to 30 μm and a depth of about 1.0 μm are formed on one surface of the first organic stretched film. The surface opposite to the surface on which the unevenness is formed (hereinafter referred to as “first unevenness forming surface”) is bonded to the first glass substrate 50a. That is, the grating 50b is held on the first glass substrate 50a. Therefore, the emitted light beam enters the grating 50b via the first glass substrate 50a.
[0076]
The hologram 50c splits the returning light beam from the recording surface of the optical disk 15 in the direction of the light receiving surface of the light receiving element 59. As a material of the hologram 50c, an organic stretched film having an optical anisotropy having a predetermined relationship with the optical anisotropy of the first organic stretched film is used. Here, since the returning light beam is an S-polarized light beam, as an example, an organic stretched film having an ordinary light refractive index of 1.5 and an extraordinary light refractive index of 1.7 (hereinafter, referred to as a “second organic stretched film” for convenience). Is used. That is, the extraordinary light refractive index of the grating 50b is equal to the ordinary light refractive index of the hologram 50c. Then, irregularities having a pitch of 1 to 5 μm and a depth of 2 to 5 μm are formed on the surface of the second organic stretched film. The surface opposite to the surface on which the unevenness is formed (hereinafter referred to as “second unevenness forming surface”) is bonded to the second glass substrate 50d. That is, the hologram 50c is held on the second glass substrate 50d. Therefore, the return light beam enters the hologram 50c via the second glass substrate 50d.
[0077]
In the first embodiment, as an example, as shown in FIG. 3, the area of a region (hereinafter also referred to as “grating region” for convenience) AG on which unevenness is formed on the first organic stretched film is equal to the area of the first organic stretched film. 2 is set to be larger than the area of the area AH where the unevenness is formed on the organic stretched film (hereinafter, also referred to as “hologram area” for convenience).
[0078]
The first organic stretched film and the second organic stretched film are polyester, polyimide, polyethylene, polycarbonate, polyvinyl alcohol, polymethyl methacrylate, polystyrene, polysulfone, polyethersulfone, and It is made from organic materials such as polyethylene terephthalate. The first glass substrate 50a and the second glass substrate 50d are made of the same material, and inexpensive glass such as BSC7 or quartz glass, which is a kind of optical glass, is used. Note that a white plate glass or a transparent resin substrate may be used as the first glass substrate 50a and the second glass substrate 50d.
[0079]
The filler 50e is isotropic and is filled in the grooves on the first uneven surface and the second uneven surface. Further, the filler 50e also has a role of an adhesive for bonding the grating 50b and the hologram 50c. That is, the filler 50e fills the space formed between the grating 50b and the hologram 50c. The refractive index of the filler 50e is set to 1.5 so as to match the extraordinary light refractive index in the grating 50b. Therefore, in the present embodiment, as the filler 50e, for example, an ultraviolet curable resin for lens bonding whose components are adjusted to have a refractive index of approximately 1.5 is used. Note that the refractive index of the filler 50e may be set to match the ordinary light refractive index (here, 1.5) of the hologram 50c.
[0080]
Since the polarization diffraction element 50 is configured as described above, as shown in FIGS. 4A and 4B, the grating 50b diffracts the light beam LBp of P-polarized light (ordinary light), The polarized light beam (abnormal light) LBs is transmitted as it is. In the hologram 50c, the S-polarized light beam LBs is diffracted, but the P-polarized light beam LBp is transmitted as it is.
[0081]
Here, an example of a method for manufacturing the polarization diffraction element 50 will be described with reference to FIGS. Note that FIGS. 5A to 7C show only a portion corresponding to one polarization diffraction element for convenience.
[0082]
First, a glass disk G1 serving as a first glass substrate 50a and an organic stretched film M1 serving as a first organic stretched film are attached with a first adhesive AD1 (see FIG. 5A). In addition, the glass disk G1 and the organic stretched film M1 each have a diameter (for example, about 10 cm) that is approximately the same as that of a normal silicon wafer. The first adhesive AD1 has a refractive index substantially equal to the ordinary light refractive index of the organic stretched film M1 (here, about 1.6).
[0083]
Further, a photosensitive resin (hereinafter, referred to as "photoresist") R is uniformly applied to the surface of the organic stretched film M1 by using a spin coater (not shown) (see FIG. 5B).
[0084]
Then, a grating pattern for grating corresponding to a light beam having a wavelength of 660 nm is transferred to the photoresist R using an exposure device (not shown), and then the photoresist R is developed using a developing device (not shown). A lattice pattern is formed by the resist R (see FIG. 5C). The pitch of this lattice pattern is 10 to 30 μm. Although one lattice pattern is shown in FIG. 5C for convenience, a plurality of lattice patterns identical to the lattice pattern shown in FIG. 5C are formed on the surface of the organic stretched film M1. .
[0085]
Then, the organic stretched film M1 in a portion where the photoresist R is not left is dry-etched using a reactive ion etching device (not shown) to form a groove having a depth of about 1.0 μm, and then a cleaning device (not shown) The photoresist R is removed with a solvent or a gas by using (omitted). Thereby, irregularities having a pitch of 10 to 30 μm and a depth of about 1.0 μm are formed on the surface of the organic stretched film M1 (see FIG. 5D).
[0086]
Next, a glass disk G2 serving as the second glass substrate 50d and an organic stretched film M2 serving as a second organic stretched film are attached with a second adhesive AD2 (see FIG. 6A). The glass disk G2 and the organic stretched film M2 have substantially the same diameter as the glass disk G1 and the organic stretched film M1, respectively. The second adhesive AD2 has a refractive index (about 1.5 in this case) substantially equal to the ordinary light refractive index of the organic stretched film M2.
[0087]
Further, a photoresist R is uniformly applied on the organic stretched film M2 using a spin coating device (not shown) (see FIG. 6B).
[0088]
Then, a hologram lattice pattern corresponding to a light beam having a wavelength of 660 nm is transferred to the photoresist R using an exposure device (not shown), and then the photoresist R is developed using a developing device (not shown). A lattice pattern is formed by the resist R (see FIG. 6C). The pitch of this lattice pattern is 1 to 5 μm. Although one lattice pattern is shown in FIG. 6C for convenience, a plurality of lattice patterns identical to the lattice pattern shown in FIG. 6C are formed on the surface of the organic stretched film M2. .
[0089]
Then, using a reactive ion etching device (not shown), the organic stretched film M2 in a portion where the photoresist does not remain is dry-etched to form a groove having a depth of 2 to 5 μm, and then a cleaning device (not shown) The photoresist R is removed by a solvent or a gas using the method described above. Thereby, irregularities having a pitch of 1 to 5 μm and a depth of 2 to 5 μm are formed on the surface of the organic stretched film M2 (see FIG. 6D).
[0090]
Subsequently, an ultraviolet curable resin UP serving as a filler 50e is filled into the uneven grooves formed on the surface of the organic stretched film M1 (see FIG. 7A). The concave and convex grooves formed on the surface of the organic stretched film M2 are also filled with the ultraviolet curable resin UP (see FIG. 7B).
[0091]
Then, the organic stretched film M1 and the organic stretched film M2 are overlapped so that the surfaces on which the irregularities are formed face each other via the ultraviolet curable resin UP (see FIG. 7C).
[0092]
Next, the ultraviolet curable resin UP is irradiated with ultraviolet light using an ultraviolet irradiation device (not shown) to cure the ultraviolet curable resin UP. Thus, a disc in which the glass disc G1, the organic stretched film M1, the ultraviolet curable resin UP, the glass disc G2, and the organic stretched film M2 are laminated and integrated (hereinafter, referred to as “first laminated disc” for convenience). HP is made.
[0093]
After the ultraviolet curable resin UP is sufficiently cured, the first laminated disk HP is set in a cutting device (not shown) and cut into predetermined dimensions. Then, through a finishing step, a washing / drying step, an inspection step, and the like, the polarization diffraction element 50 is obtained. That is, a plurality of polarization diffraction elements 50 can be obtained from one first laminated disk HP.
[0094]
Returning to FIG. 2A, the coupling lens 52 is disposed on the + X side of the polarization diffraction element 50, and converts each light beam divided by the grating 50b into substantially parallel light. On the + X side of the coupling lens 52, the λ / 4 plate 55 for adding an optical phase difference of １ ／ wavelength to the transmitted light flux is disposed. On the + X side of the λ / 4 plate 55, the objective lens 60 that condenses the light flux transmitted through the λ / 4 plate 55 and forms a light spot on the recording surface of the optical disk 15 is disposed.
[0095]
The light receiver 59 is arranged near the light source unit 51, and receives the return light beam diffracted by the hologram 50c. The light receiver 59 includes a plurality of light receiving elements corresponding to the three-beam method.
[0096]
The operation of the optical pickup device 23 configured as described above will be described.
[0097]
A light beam of linearly polarized light (here, P-polarized light) emitted from the semiconductor laser 51a enters the grating 50b via the first glass substrate 50a. This light beam is split by the grating 50b into zero-order light and ± first-order diffracted light. Then, each light beam passes through the hologram 50 c without undergoing the hologram effect, becomes substantially parallel light by the collimator lens 52, is circularly polarized by the λ / 4 plate 55, and is recorded on the optical disk 15 via the objective lens 60. Each light is focused on the surface as a minute spot.
[0098]
Each reflected light reflected on the recording surface of the optical disc 15 becomes circularly polarized light in the opposite direction to the outward path, is converted into substantially parallel light again by the objective lens 60 as a return light beam, and a straight line orthogonal to the outward path by the λ / 4 plate 55. It is polarized (here, S-polarized). Then, each return light beam is transmitted through the collimator lens 52, then diffracted by the hologram 50 c, transmitted through the grating 50 b as it is, and received by the light receiver 59. Each light receiving element constituting the light receiver 59 outputs a signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0099]
Next, a processing operation for recording data on the optical disk 15 using the above-described optical disk device 20 will be briefly described.
[0100]
Upon receiving the recording request command from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 to the motor driver 27 based on the recording speed, and reproduces that the recording request command has been received from the host. Notify the signal processing circuit 28. Further, the CPU 40 instructs the buffer manager 37 to store the data (hereinafter, referred to as “user data”) received from the host in the buffer RAM 34.
[0101]
When the rotation of the optical disk 15 reaches a predetermined linear velocity, the reproduction signal processing circuit 28 detects a servo signal (track error signal and focus error signal) based on the output signal of the light receiver 59, and outputs the detection result to the servo controller 33. Output to
[0102]
The servo controller 33 controls the tracking actuator of the optical pickup device 23 via the motor driver 27 based on the track error signal, and corrects a track shift. Further, the servo controller 33 controls the focusing actuator of the optical pickup device 23 via the motor driver 27 based on the focus error signal, and corrects a focus shift. In this way, tracking control and focus control are performed.
[0103]
Further, the reproduction signal processing circuit 28 detects a wobble signal based on the output signal of the light receiver 59 and notifies the CPU 40 of address information extracted from the wobble signal. Then, the CPU 40 outputs a signal for controlling the seek motor of the optical pickup device 23 to the motor driver 27 based on the address information from the reproduction signal processing circuit 28 so that the optical pickup device 23 is located at the designated write start point. I do. The reproduction signal processing circuit 28 extracts address information at predetermined timings, and notifies the CPU 40 of the extracted address information.
[0104]
When receiving from the buffer manager 37 that the amount of user data stored in the buffer RAM 34 has exceeded a predetermined amount, the CPU 40 instructs the encoder 25 to create a write signal.
[0105]
When the CPU 40 determines that the position of the optical pickup device 23 is the writing start point based on the address information, the CPU 40 notifies the encoder 25. Thus, the user data is recorded on the optical disk 15 via the encoder 25, the laser control circuit 24, and the optical pickup device 23.
[0106]
Next, a brief description will be given of a processing operation when reproducing the user data recorded on the optical disk 15 using the optical disk device 20 described above.
[0107]
When the CPU 40 receives a reproduction request command from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 to the motor driver 27 based on the reproduction speed, and reproduces that the reproduction request command has been received from the host. Notify the signal processing circuit 28. Then, when the rotation of the optical disk 15 reaches a predetermined linear velocity, tracking control and focus control are performed as in the case of the recording processing. Also, the reproduction signal processing circuit 28 extracts the address information and notifies the CPU 40 of the address information, as in the case of the recording processing.
[0108]
The CPU 40 outputs a signal for controlling the seek motor to the motor driver 27 based on the address information so that the optical pickup device 23 is located at the designated reading start point. When the CPU 40 determines that the position of the optical pickup device 23 is the reading start point based on the address information, the CPU 40 notifies the reproduction signal processing circuit 28.
[0109]
Then, the reproduction signal processing circuit 28 detects the RF signal based on the output signal of the light receiver 59, performs demodulation processing, error correction processing, and the like, and stores the RF signal in the buffer RAM 34. The buffer manager 37 transfers the reproduced data stored in the buffer RAM 34 to the host via the interface 38 when the data is prepared as sector data.
[0110]
Note that the tracking control and the focus control are performed at predetermined timings until the recording processing and the reproduction processing are completed.
[0111]
As is clear from the above description, in the optical disc device according to the first embodiment, a processing device is realized by the reproduction signal processing circuit 28, the CPU 40, and the program executed by the CPU 40. However, it goes without saying that the present invention is not limited to this. That is, the first embodiment is merely an example, and at least a part of each component realized by the processing according to the program by the CPU 40 may be configured by hardware, or all the components may be configured by hardware. It is good also as comprising.
[0112]
As described above, according to the polarization diffraction element 50 according to the first embodiment, the organic stretched film having the optical anisotropy in which the unevenness for the grating is formed and the optically stretched film having the unevenness for the hologram are formed. Since the organically stretched film having optical anisotropy is integrated via the optically isotropic filler, it is possible to easily satisfy the design conditions regarding the respective refractive indexes. That is, since an inexpensive material can be used, cost reduction can be promoted without lowering the light use efficiency.
[0113]
Further, according to the first embodiment, the organic stretched film M1 having the unevenness for the grating and the organic stretched film M2 having the unevenness for the hologram are held on the same glass substrate. Therefore, when cutting out the polarization diffraction element 50 from the first laminated disk HP, there is no need to change a processing tool (for example, a dicing saw) or change a processing condition (for example, a feed speed) during the operation. Therefore, productivity is improved, and cost reduction can be promoted.
[0114]
According to the first embodiment, the first adhesive AD1 for bonding the glass disk G1 and the organic stretched film M1 has a refractive index substantially equal to the ordinary light refractive index of the organic stretched film M1. For example, as shown in FIG. 8A, when the thickness of the adhesive layer is not uniform, the planarity at the bonding interface between the organic stretched film M1 and the first adhesive AD1 is disturbed. Is corrected, and deterioration of the wavefront aberration in the light beam condensed on the recording surface can be suppressed. Similarly, since the second adhesive AD2 for bonding the glass disk G2 and the organic stretched film M2 has a refractive index substantially the same as the ordinary light refractive index of the organic stretched film M2, FIG. As shown in (B), when the thickness of the adhesive layer is not uniform, the irregularity of the flatness at the adhesive interface between the organic stretched film M2 and the second adhesive AD2 is corrected, and the unevenness on the recording surface is corrected. It is possible to suppress the deterioration of the wavefront aberration in the emitted light beam. That is, it is possible to suppress a decrease in light use efficiency.
[0115]
Further, according to the first embodiment, since the organic stretched film is used as the material having optical anisotropy, fine processing is easy, and predetermined irregularities can be accurately formed. Therefore, it is possible to obtain a polarization characteristic substantially as designed, and it is possible to suppress a decrease in light use efficiency. Further, since the thickness of the organic stretched film is extremely thin, 50 to 100 μm, it is possible to suppress the generation of wavefront aberration even when the organic stretched film is disposed in the divergent light path.
[0116]
Further, according to the first embodiment, since the area of the grating area is set to be larger than the area of the hologram area, for example, there is a displacement during assembly or a lens shift of the objective lens. Also, the return light beam diffracted by the hologram 50c always passes through the grating region and is received by the light receiver 59. Thus, the return light beam diffracted by the hologram 50c is transmitted through the grating 50b with a substantially constant transmittance, and is received by the light receiver 59 with almost no disturbance of the wavefront aberration. Therefore, the stability of the signal output from the light receiver 59 can be improved.
[0117]
It is generally known that the diffraction angle θ of a hologram is represented by the following equation (1). Here, λ is the wavelength of the incident light beam, and Λ is the pitch of the unevenness (hologram pitch).
[0118]
sin θ = λ / Λ (1)
[0119]
Therefore, when the wavelength of the light beam becomes shorter, it is necessary to reduce the hologram pitch or to reduce the distance between the light source and the light receiver. All of these involve work difficulties and increase costs. However, according to the first embodiment, since the return light beam diffracted by the hologram 50c is not affected by the grating 50b, the thickness of the polarization diffraction element can be reduced. For example, a blue light source (λ = 405 nm) is used. Even in this case, a return light beam of a predetermined light amount can be received by the light receiver simply by changing the position of the polarization diffraction element without changing any of the hologram pitch and the distance between the light source and the light receiver.
[0120]
Further, according to the optical pickup device according to the first embodiment, since a small and inexpensive polarization diffraction element having excellent light use efficiency is used, the optical pickup device can be manufactured without increasing the size and cost. It is possible to accurately output a signal including information necessary for controlling the position of itself and the objective lens.
[0121]
Further, according to the optical disc device 20 according to the first embodiment, since the position of the optical pickup device itself and the position of the objective lens can be accurately controlled based on the output signal of the optical pickup device 23, information at a high speed can be obtained. It is possible to accurately and stably perform an access including at least the reproduction among the recording, reproduction, and erasing. Furthermore, the miniaturization of the optical pickup device can promote the miniaturization of the optical disc device itself and the reduction of power consumption. For example, when the optical pickup device is used for portable use, it is easy to carry and can be used for a longer time. It becomes.
[0122]
In the above-described first embodiment, the case where the optical anisotropy of the first organic stretched film and the optical anisotropy of the second organic stretched film are different from each other has been described. For example, the first organic stretched film may be used instead of the second organic stretched film. In this case, the ordinary ray direction in the first organic stretched film on the first substrate and the ordinary ray direction in the first organic stretched film on the second substrate are arranged at an angle of 90 degrees to each other. That is, in the hologram, the ordinary light refractive index is 1.5 and the extraordinary light refractive index is 1.6. Although the extraordinary light refractive index is smaller and the diffraction efficiency is lower than when the second organic stretched film is used, the diffraction efficiency is reduced by making the groove deeper than in the case of the first embodiment. It is possible to suppress the decrease. In addition, since one type of the organic stretched film is used, cost reduction can be promoted.
[0123]
In the first embodiment, the case where the first adhesive AD1 for bonding the glass disk G1 and the organic stretched film M1 has a refractive index substantially equal to the ordinary light refractive index of the organic stretched film M1 will be described. However, for example, when the adhesive layer is extremely thin or when the flatness of the bonding interface is secured, the refractive index does not necessarily have to be the same as the ordinary light refractive index of the organic stretched film M1. Similarly, the second adhesive AD2 for bonding the glass disk G2 and the organic stretched film M2 is also used, for example, when the adhesive layer is extremely thin or when the flatness of the bonding interface is ensured. However, the refractive index does not necessarily have to be the same as the ordinary light refractive index of the organic stretched film M2.
[0124]
In the first embodiment, the case where the organic stretched film is used as the material having optical anisotropy has been described, but the present invention is not limited to this. However, for example, as shown in FIG. 9, in the case of a polarization diffraction element 50N using lithium niobate LN1 or LN2 as a material having optical anisotropy, a glass substrate is not necessary, so that the entire element has a polarization It becomes thinner than the diffraction element 50. However, since the thickness of the optical member having optical anisotropy becomes thicker than that of the polarization diffraction element 50 and the wavefront aberration becomes large in the non-parallel optical path, there is a restriction that the polarization diffraction element 50N can be arranged only in the parallel optical path. is there. Further, as shown in FIG. 9 as an example, in the case of a polarization diffraction element 50L using liquid crystals LC1 and LC2 as materials having optical anisotropy, the thickness of the optical member having optical anisotropy is It is thinner than the element 50. However, since the liquid crystal needs to be sandwiched between the glass plates LG, the entire device is thicker than the polarization diffraction device 50.
[0125]
In the first embodiment, the case where the first glass substrate 50a and the second glass substrate 50d have the same plate thickness has been described. However, the present invention is not limited to this, and the plate thickness of the first glass substrate 50a and the second glass substrate 50d may be different. The thickness of the substrate 50d may be different from each other. For example, as shown in FIG. 10, a first glass substrate 50a 'having a greater thickness than the first glass substrate 50a is used instead of the first glass substrate 50a, and a second glass substrate 50d is used instead of the second glass substrate 50d. Even the polarization diffraction element 50 'using the second glass substrate 50d' having a smaller thickness can be manufactured in the same manner as the polarization diffraction element 50. In this case, the plate thickness of the first glass substrate 50a 'is larger than the plate thickness of the second glass substrate 50d'. Thereby, as shown in FIGS. 11A and 11B as an example, the distance in the X-axis direction between the hologram (hologram 50c ') and the light receiver 59 in the polarization diffraction element 50' is increased. Since the distance in the X-axis direction between the hologram (hologram 50 c) and the light receiver 59 in 50 is longer, the diffraction angle of the hologram in the polarization diffraction element 50 ′ can be smaller than that in the polarization diffraction element 50. . Therefore, it is possible to increase the pitch of the unevenness in the hologram 50c 'as compared with the hologram 50c. That is, the formation of the hologram irregularities becomes easy, and the yield can be improved.
[0126]
Further, in the first embodiment, a case has been described in which a semiconductor laser that emits a light beam having a wavelength of 660 nm is used as a light source. However, the present invention is not limited to this. For example, a light source that emits a light beam having a wavelength of 405 nm and a wavelength Any of the light sources that emit a light beam of 780 nm may be used. However, in this case, the unevenness for the grating and the unevenness for the hologram correspond to the wavelength of the light beam emitted from the light source used.
[0127]
<< 2nd Embodiment >>
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.
[0128]
In the second embodiment, as shown in FIG. 12A as an example, an optical pickup device 23 'corresponding to a light beam of two wavelengths is used instead of the optical pickup device 23 in the first embodiment. It is characterized in that In the optical pickup device 23 ′, a light source unit 71 having two light sources that emit light beams having different wavelengths is used instead of the light source unit 51, and the light source unit 71 corresponds to a light beam of two wavelengths instead of the polarization diffraction element 50. A polarization diffraction element 70 is used. The configuration of the other optical pickup device and optical disk device is substantially the same as that of the first embodiment, although the processing content is slightly different depending on the wavelength. Therefore, in the following, description will be made focusing on differences from the first embodiment, and the same or equivalent components as those in the first embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted. Shall be. Also, the preconditions are the same as in the first embodiment.
[0129]
The light source unit 71 is configured to include a first semiconductor laser 71a as a light source that emits a light beam having a wavelength of 660 nm and a second semiconductor laser 71b as a light source that emits a light beam having a wavelength of 780 nm. . Therefore, an information recording medium (hereinafter, referred to as “DVD”) conforming to the DVD standard and an information recording medium (hereinafter, referred to as “CD”) conforming to the CD standard are used for the optical disc 15. That is, the optical disk device is a so-called combo drive device.
[0130]
The polarization diffraction element 70 includes, in the polarization diffraction element 50 in the first embodiment, a grating (hereinafter, also referred to as a “CD grating” for convenience) that divides a light beam having a wavelength of 780 nm into zero-order light and ± first-order diffraction light, A hologram (hereinafter, also referred to as “CD hologram” for convenience) that branches a return light beam having a wavelength of 780 nm in the light receiving surface direction of the light receiving element 59 is added. Here, as an example, as shown in FIG. 12B, irregularities for the CD grating 70a are formed on the light source unit 71 side surface of the first glass substrate 50a, and the coupling lens 52 side of the second glass substrate 50d is formed. Are formed on the surface of the CD hologram 70b. That is, the polarization diffraction element 70 includes a grating 50b (hereinafter also referred to as “DVD grating” for convenience) that divides a light beam having a wavelength of 660 nm into zero-order light and ± first-order diffraction light, and a light receiving element 59 that receives a return light beam having a wavelength of 660 nm. (Hereinafter also referred to as "DVD hologram" for convenience) 50c, a CD grating 70a, and a CD hologram 70b. The CD grating 70a and the CD hologram 70b are non-polarizing. Therefore, the area of the CD grating 70a is set smaller than the area of the CD hologram 70b so that the return light beam split by the CD hologram 70b does not enter.
[0131]
Here, a method for manufacturing the polarization diffraction element 70 will be described with reference to FIGS. FIGS. 13A to 15C show only a portion corresponding to one polarization diffraction element for convenience.
[0132]
First, in the same manner as in the case of the polarization diffraction element 50, the glass disk G1 and the organic stretched film M1 are bonded to each other with the first adhesive AD1, and the pitch is 10 to 30 μm and the depth is on the surface of the organic stretched film M1. Form irregularities for a DVD grating of about 1.0 μm (see FIGS. 5A to 5D).
[0133]
Next, the glass disk G1 is inverted so that the glass disk G1 faces upward (see FIG. 13A). Further, a photoresist R is uniformly applied on the glass disk G1 by using a spin coating apparatus (not shown) (see FIG. 13B).
[0134]
Then, a grating pattern corresponding to a light beam having a wavelength of 780 nm is transferred to the photoresist R using an exposure device (not shown), and then the photoresist R is developed using a developing device (not shown). A lattice pattern is formed by the resist R (see FIG. 13C). Although one lattice pattern is shown in FIG. 13C for convenience, a plurality of lattice patterns identical to the lattice pattern shown in FIG. 13C are formed on the surface of the glass disk G1. .
[0135]
Then, after dry etching the glass disk G1 in a portion where the photoresist R does not remain using a reactive ion etching device (not shown), the photoresist R is removed with a solvent or gas using a cleaning device (not shown). Is removed. Thereby, irregularities for the CD grating are formed on the surface of the glass disk G1 (see FIG. 13D).
[0136]
Further, in the same manner as in the case of the polarization diffraction element 50, after the glass disk G2 and the organic stretched film M2 are bonded with the second adhesive AD2, the pitch is 1 to 5 μm and the depth is on the surface of the organic stretched film M2. Form irregularities for a DVD hologram of 2 to 5 μm (see FIGS. 6A to 6D).
[0137]
Next, the glass disk G2 is inverted so that the glass disk G2 faces upward (see FIG. 14A). Further, a photoresist R is uniformly applied onto the glass disk G2 using a spin coating apparatus (not shown) (see FIG. 14B).
[0138]
Then, a hologram lattice pattern corresponding to a light beam having a wavelength of 780 nm is transferred to the photoresist R using an exposure device (not shown), and then the photoresist R is developed using a developing device (not shown). A lattice pattern is formed by the resist R (see FIG. 14C). Although one grid pattern is shown in FIG. 14C for convenience, a plurality of the same grid patterns as those shown in FIG. 14C are formed on the surface of the glass disk G2. .
[0139]
Then, after dry etching the glass disk G2 in a portion where the photoresist R does not remain using a reactive ion etching device (not shown), the photoresist R is removed with a solvent or gas using a cleaning device (not shown). Is removed. Thereby, irregularities for a CD hologram are formed on the surface of the glass disk G2 (see FIG. 14D).
[0140]
Subsequently, an ultraviolet curable resin UP serving as a filler 50e is filled in the concave and convex grooves formed on the surface of the organic stretched film M1 (see FIG. 15A). Further, the concave and convex grooves formed on the surface of the organic stretched film M2 are filled with the ultraviolet curable resin UP (see FIG. 15B).
[0141]
Then, the organic stretched film M1 and the organic stretched film M2 are overlapped so that the surfaces on which the irregularities are formed face each other via the ultraviolet curable resin UP (see FIG. 15C).
[0142]
Next, the ultraviolet curable resin UP is irradiated with ultraviolet light using an ultraviolet irradiation device (not shown) to cure the ultraviolet curable resin UP. As a result, a disk (hereinafter, referred to as a “second laminated disk”) WP in which the glass disk G1, the organic stretched film M1, the ultraviolet curable resin UP, the glass disk G2, and the organic stretched film M2 are integrated is formed. Made.
[0143]
After the ultraviolet curable resin UP is sufficiently cured, the second laminated disk WP is set in a cutting device (not shown) and cut into predetermined dimensions. Then, through a finishing step, a washing / drying step, an inspection step, etc., the polarization diffraction element 70 is obtained. That is, a plurality of polarization diffraction elements 70 can be obtained from one second laminated disk WP.
[0144]
The operation of the optical pickup device 23 'configured as described above will be described. First, the case where the optical disk 15 is a DVD will be described with reference to FIGS. 16 (A) and 16 (B).
[0145]
The light beam of linearly polarized light (here, P-polarized light) emitted from the first semiconductor laser 71a enters the CD grating 70a. As shown in FIG. 16A, this light flux is hardly split by the CD grating 70a, and most of the light passes through the CD grating 70a. The luminous flux transmitted through the CD grating 70a is transmitted through the first glass substrate 50a, and is split into zero-order light and ± first-order diffracted light by the DVD grating 50b. Then, each light beam passes through the DVD hologram 50c and enters the CD hologram 70b. Each light beam transmitted through the CD hologram 70b is converted into substantially parallel light by the collimator lens 52, then circularly polarized by the λ / 4 plate 55, and collected as a minute spot on the recording surface of the optical disk 15 via the objective lens 60. Is lighted.
[0146]
Each reflected light reflected on the recording surface of the optical disc 15 becomes circularly polarized light in the opposite direction to the outward path, is converted into substantially parallel light again by the objective lens 60 as a return light beam, and a straight line orthogonal to the outward path by the λ / 4 plate 55. It is polarized (here, S-polarized). Each return light beam enters the CD hologram 70b after passing through the collimator lens 52. As shown in FIG. 16B, each return light beam transmitted through the CD hologram 70b is diffracted by the DVD hologram 50c, transmitted directly through the DVD grating 50b, and received by the light receiver 59. Each light receiving element constituting the light receiver 59 outputs a signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0147]
Next, the case where the optical disc 15 is a CD will be described with reference to FIGS.
[0148]
The linearly polarized light (here, P-polarized light) emitted from the second semiconductor laser 71b is split into zero-order light and ± first-order diffracted light by a CD grating 70a as shown in FIG. The light passes through one glass substrate 50a and enters the DVD grating 50b. Each light beam transmitted through the DVD grating 50b transmits through the DVD hologram 50c and enters the CD hologram 70b. Each light beam transmitted through the CD hologram 70b is converted into substantially parallel light by the collimator lens 52, then circularly polarized by the λ / 4 plate 55, and collected as a minute spot on the recording surface of the optical disk 15 via the objective lens 60. Is lighted.
[0149]
Each reflected light reflected on the recording surface of the optical disc 15 becomes circularly polarized light in the opposite direction to the outward path, is converted into substantially parallel light again by the objective lens 60 as a return light beam, and a straight line orthogonal to the outward path by the λ / 4 plate 55. It is polarized (here, S-polarized). After returning through the collimator lens 52, each return light beam is diffracted by the CD hologram 70b and received by the light receiver 59 via the DVD hologram 50c and the DVD grating 50b, as shown in FIG. 17B. Each light receiving element constituting the light receiver 59 outputs a signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0150]
Whether the optical disk 15 is a CD or a DVD can be determined from the intensity of light reflected from the recording surface. Usually, this determination is performed when the optical disk 15 is inserted into a predetermined position of the optical disk device 20, that is, at the time of loading. In addition, the type of the optical disc 15 can be determined based on TOC (Table Of Contents) information, PMA (Program Memory Area) information, a wobble signal, and the like, which are recorded in the optical disc 15 in advance. Then, the determination result is notified to the laser control circuit 24, and the laser control circuit 24 selects one of the first semiconductor laser 71a and the second semiconductor laser 71b. The determination result is also notified to other circuits or the like that perform processing according to the type of the optical disk.
[0151]
In the optical disc device according to the second embodiment, when the optical disc 15 is a DVD, recording of data on the optical disc 15 and reproduction of data recorded on the optical disc 15 are performed in the same manner as in the first embodiment. Done. When the optical disk 15 is a CD, processing is slightly different from that for a DVD, but recording and reproduction are performed in substantially the same procedure as for a DVD.
[0152]
As is clear from the above description, in the optical disk device according to the second embodiment, a processing device is realized by the reproduction signal processing circuit 28, the CPU 40, and the program executed by the CPU 40. However, it goes without saying that the present invention is not limited to this. That is, the second embodiment is merely an example, and at least a part of each component realized by the processing according to the program by the CPU 40 may be configured by hardware, or all the components may be configured by hardware. It is good also as comprising.
[0153]
As described above, according to the polarization diffraction element 70 according to the second embodiment, the irregularities for the CD grating 70a are formed on the light source side surface of the first glass substrate 50a, and the cup of the second glass substrate 50d is formed. Since the irregularities for the CD hologram 70b are formed on the surface on the ring lens side, the size can be reduced as compared with the conventional two-wavelength compatible diffraction element KS as shown in FIG. 18 as an example. In the diffraction element KS, the light beam emitted from the light source for CD is converted into three beams by the grating Gcd for CD, and the light beam emitted from the light source for DVD is converted into three beams by the grating Gdvd for DVD. The return light beam from the CD is branched by the hologram Hcd for CD, and the return light beam from the DVD is branched by the hologram Hdvd for DVD. That is, the polarization diffraction element 70 can shorten the gap between the grating and the hologram for both CD and DVD than before.
[0154]
According to the second embodiment, the DVD grating, the DVD hologram CD grating, and the CD hologram are arranged via the same glass substrate, respectively. When cutting 70, there is no need to replace a processing tool (for example, a dicing saw) or change processing conditions (for example, feed speed) during the operation. Therefore, it is possible to improve the productivity and reduce the cost of the polarization diffraction element having excellent light use efficiency.
[0155]
In addition, according to the optical pickup device according to the second embodiment, since a compact and inexpensive two-wavelength compatible polarization diffraction element having excellent light use efficiency is used, an optical disk to be accessed is a CD or a DVD. In any case, it is possible to output a signal including information necessary for controlling the position of the optical pickup device itself and the objective lens with high accuracy.
[0156]
Further, according to the optical disk device according to the second embodiment, regardless of whether the optical disk to be accessed is a CD or a DVD, the position of the optical pickup device itself and the position of the objective lens are determined based on the output signal of the optical pickup device. Can be controlled with high accuracy, so that at least high-speed information recording, reproduction, and erasure can be performed with high accuracy and stable access to the optical disk. Furthermore, the miniaturization of the optical pickup device can promote the miniaturization of the optical disc device itself and the reduction of power consumption. For example, when the optical pickup device is used for portable use, it is easy to carry and can be used for a longer time. It becomes.
[0157]
In the second embodiment, the case where the CD hologram 70b is formed on the second glass substrate 50d and integrated with the DVD hologram 50c has been described. However, the present invention is not limited to this. When it is necessary to adjust the CD hologram 70b, a CD hologram 70b may be formed on a new glass substrate 70c as shown in FIG. 19 as an example. In this case, the second glass substrate 50d and the glass substrate 70c are bonded after the position adjustment between the DVD hologram and the CD hologram is performed.
[0158]
Further, in the second embodiment, the case has been described where the light beam emitted from the light source has two wavelengths, but the present invention is not limited to this.
[0159]
In the second embodiment, the case where the light source that emits the light beam having the wavelength of 660 nm and the light source that emits the light beam having the wavelength of 780 nm is described, but the present invention is not limited to this. For example, a light source that emits a light beam having a wavelength of 405 nm may be provided instead of one of the light sources.
[0160]
In the second embodiment, the case where the organic stretched film is used as the material having optical anisotropy has been described, but the present invention is not limited to this.
[0161]
In the first and second embodiments, the case where the first optical member and the second optical member are each formed of an organic stretched film has been described. However, the present invention is not limited to this, and one of them is formed of an organic stretched film. Is also good.
[0162]
Further, in the first and second embodiments, the case where the first optical member and the second optical member are held by the same glass substrate is described. However, the present invention is not limited to this. It may be held by a substrate. For example, even if the materials of the respective glass substrates are different from each other, there is no possibility of lowering the productivity unless there is a large difference in mechanical properties.
[0163]
Further, in the first and second embodiments, the case where the first optical member and the second optical member are each held by the glass substrate has been described. However, the present invention is not limited to this. It is not necessary to be held by the glass substrate.
[0164]
<< 3rd Embodiment >>
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. 20 (A) and 20 (B).
[0165]
In the third embodiment, an optical pickup device 23 "as shown in FIG. 20A is used as an example instead of the optical pickup device 23 in the first embodiment. This optical pickup device 23" Is a modification in which the polarization diffraction element 50 of the optical pickup device 23 is changed to a polarization diffraction element 80, and is characterized in that the hologram is non-polarizing. Other configurations of the optical pickup device and the optical disk device are the same as those of the first embodiment. Therefore, in the following, description will be made focusing on differences from the first embodiment, and the same or equivalent components as those in the first embodiment will be denoted by the same reference numerals, and the description thereof will be simplified or omitted. Shall be. Also, the preconditions are the same as in the first embodiment.
[0166]
As shown in FIG. 20B, the polarization diffraction element 80 includes a glass substrate 80a as a third substrate, a grating 80b as a first optical member, a filler 80e as a filler, and a filler 80e as a second optical member. The hologram 80c is included.
[0167]
The grating 80b divides the emitted light beam into zero-order light and ± first-order diffracted light. As a material of the grating 80b, an organic stretched film having optical anisotropy is used. Here, since the emitted light beam is a P-polarized light beam, an organic stretched film having an ordinary light refractive index of 1.6 and an extraordinary light refractive index of 1.5 (hereinafter, referred to as a “third organic stretched film”) is used as an example. Can be Then, irregularities having a pitch of 10 to 30 μm and a depth of about 1.0 μm are formed on one surface of the third organic stretched film. The surface opposite to the surface on which the unevenness is formed (hereinafter referred to as “third unevenness forming surface”) is bonded to the glass substrate 80a. That is, the grating 80b is held on the glass substrate 80a. Therefore, the emitted light beam enters the grating 80b via the glass substrate 80a.
[0168]
The filler 80e is made of the same material as the filler 50e in the first embodiment. That is, a UV-curable resin for bonding a lens, whose components are adjusted so that the refractive index becomes approximately 1.5, is used.
[0169]
The hologram 80c splits the returning light beam from the recording surface of the optical disk 15 in the direction of the light receiving surface of the light receiving element 59. As the material of the hologram 80c, optical glass (for example, BSC7 and quartz glass) of the same material as the glass substrate 80a is used. Then, irregularities having a pitch of 1 to 5 μm and a depth of about 3 μm are formed on the surface of the optical glass. For example, when quartz glass having a refractive index of 1.45 is used as the optical glass, a difference of 0.05 between the filler 80e and the filler 80e occurs, and a part of the incident light beam is diffracted. However, unlike the first embodiment, since the hologram 80c is made of an optically isotropic optical member, its diffraction efficiency is constant without depending on the polarization state of the incident light beam. That is, it is a non-polarized hologram. The surface on which the irregularities are formed (hereinafter, referred to as “fourth irregularity forming surface”) faces the third irregularity forming surface. Note that a white plate glass or a transparent resin substrate may be used instead of the optical glass.
[0170]
In the third embodiment, as in the first embodiment, the area of the grating region is set to be larger than the area of the hologram region.
[0171]
Since the polarization diffraction element 80 is configured as described above, the P-polarized light (ordinary light) is diffracted by the grating 80b, but the S-polarized light (abnormal light) is transmitted as it is. In the hologram 80c, both the P-polarized light beam and the S-polarized light beam are partially diffracted.
[0172]
The polarization diffraction element 80 can be manufactured more easily than the polarization diffraction element 50.
[0173]
1. Similarly to the case of the polarization diffraction element 50, after a glass disk for a glass substrate (hereinafter referred to as a “glass disk for grating”) and an organic stretched film serving as a third organic stretched film are bonded with an adhesive, Grating irregularities having a pitch of 10 to 30 μm and a depth of about 1.0 μm are formed on the surface of the organic stretched film. The adhesive has a refractive index substantially the same as the ordinary light refractive index of the organic stretched film.
2. A photoresist R is uniformly applied on a hologram glass disk using a spin coating apparatus. In the post-process, some commercially available semiconductor manufacturing equipment is used.In order to improve the workability in the post-process, the thickness of the glass disk for the hologram is smaller than the thickness of the glass disk for the grating. Has become. Here, as an example, the thickness of the hologram glass disk is about 0.6 mm, and the thickness of the grating glass disk is about 1.0 mm.
3. After transferring the hologram lattice pattern to the photoresist R using an exposure device, the photoresist R is developed using a developing device to form a lattice pattern using the photoresist R. The pitch of this lattice pattern is 1 to 5 μm.
4. The glass disk at the portion where the photoresist R is not left is dry-etched using a reactive ion etching apparatus to form a groove having a depth of about 3 μm, and then the photoresist R is etched with a solvent or gas using a cleaning apparatus. Is removed. Thus, hologram irregularities having a pitch of 1 to 5 μm and a depth of about 3 μm are formed on the surface of the hologram glass disk.
5. The grooves of the grating irregularities and the hologram irregularities are each filled with an ultraviolet curable resin to be the filler 80e.
6. After the grating unevenness and the hologram unevenness are superimposed on each other, the ultraviolet curable resin is irradiated with ultraviolet rays using an ultraviolet irradiation device to cure the ultraviolet curable resin. As a result, a disc (hereinafter, referred to as a “third laminated disc” for convenience) is formed by laminating and integrating the glass disc for grating, the organic stretched film, the ultraviolet curable resin, and the glass disc for hologram.
7. After the UV-curable resin is sufficiently cured, the third laminated disk is set in a cutting device and cut into predetermined dimensions. Then, through a finishing step, a washing / drying step, an inspection step, and the like, the polarization diffraction element 80 is obtained.
[0174]
The operation of the optical pickup device 23 ″ configured as described above will be described.
[0175]
A light beam of linearly polarized light (here, P-polarized light) emitted from the semiconductor laser 51a enters the grating 80b via the glass substrate 80a. This light beam is split into zero-order light and ± first-order diffracted light by the grating 80b. A part of each light beam is diffracted by the hologram 80c, but most of the light beam is transmitted through the hologram 80c, becomes substantially parallel light by the collimator lens 52, and is then circularly polarized by the λ / 4 plate 55. The light is condensed as minute spots on the recording surface of the optical disc 15 via the lens 60.
[0176]
Each reflected light reflected on the recording surface of the optical disk 15 is converted into a substantially parallel light again by the objective lens 60 as a return light beam, transmitted through the λ / 4 plate 55 and the collimating lens 52, diffracted by the hologram 80c, and then grating. The light passes through 80 b as it is and is received by the light receiver 59. Each light receiving element constituting the light receiver 59 outputs a signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0177]
In the optical disk device according to the third embodiment, recording of data on the optical disk 15 and reproduction of data recorded on the optical disk 15 are performed in the same manner as in the first embodiment.
[0178]
As described above, according to the polarization diffraction element 80 according to the third embodiment, since the hologram is non-polarized light, even if the return light beam incident on the hologram contains the P-polarized component, a predetermined amount of light is emitted. The return light beam can be received by the light receiving device, and the signal level and the S / N ratio of the output signal from the light receiving device can be increased.
[0179]
Generally, in an optical disk, a recording surface is formed on a transparent resin substrate, and a light beam from an objective lens passes through the resin substrate and is condensed on the recording surface. From the viewpoint of productivity, most of the resin substrate is an injection molding method in which a molten resin is injected while being pressed into a molding die (usually a mold) having a cavity having a shape similar to a molded product, and the like. It is manufactured by a method. In the case where the molded product is a disk shape like an optical disk, a molding method using a radial flow type molding die having a direct gate (injection port) at the center of the cavity (a portion corresponding to the rotation center of the substrate) ( Method) is usually adopted, and the molten resin flows from the central part of the cavity to the outer peripheral part through the direct gate. Since the temperature and cooling rate of the resin injected into the cavity are not constant, internal stress may remain in the molded product or the density of the resin may be non-uniform. Therefore, the resin substrate of the optical disk manufactured as described above may have a property (birefringence) in which the refractive index differs from each other in the tangential direction of the track and in the direction perpendicular thereto. When the resin substrate has birefringence as described above, since the refractive index of the light beam transmitted through the resin substrate differs depending on the direction, a wavefront aberration including an astigmatism component occurs. Then, the light reflected on the recording surface of the optical disk becomes elliptically polarized light. When the elliptically polarized return light beam enters the λ / 4 plate, the return light beam incident on the hologram contains a P-polarized component. When the hologram has a polarization property as in the first embodiment, the P-polarized component is transmitted without being affected by the hologram, so that the amount of light received by the light receiver decreases. Further, since the birefringence of the resin substrate is usually not uniform, the output signal of the light receiver becomes unstable. In the third embodiment, since the hologram is non-polarized, when a poor optical disk having a large birefringence is used, a decrease in the amount of light received by the light receiver can be suppressed, and the signal detection can be stabilized. Can be performed.
[0180]
Further, according to the third embodiment, since the organic stretched film is used as the material of the grating, the size can be reduced as compared with the case where the lithium niobate crystal (LN crystal) is used. Further, in the case of using a liquid crystal as a material of the grating to form a polarization diffraction element by a so-called selective exposure method, as shown in FIG. 21 as an example, the unevenness P for the grating and the unevenness Q for the hologram are opposed to each other. Becomes difficult, and the hologram unevenness Q is exposed, so that handling becomes troublesome. On the other hand, the polarization diffraction element 80 is easy to handle because both the light source side surface and the optical disk side surface are glass planes, and the thickness can be adjusted by polishing even after completion.
[0181]
Further, according to the third embodiment, since the adhesive for bonding the glass disk for grating and the organic stretched film has a refractive index substantially the same as the ordinary light refractive index of the organic stretched film, When the thickness of the agent layer is not uniform, the disorder of the flatness of ordinary light at the bonding interface between the organic stretched film and the adhesive is corrected, and the deterioration of wavefront aberration in the light beam focused on the recording surface is suppressed. Can be.
[0182]
According to the third embodiment, when the polarization diffraction element 80 is manufactured, the thickness of the hologram glass disk is made smaller than the thickness of the grating glass disk. The handling in the process becomes easy, and the yield can be improved.
[0183]
Further, according to the optical pickup device according to the third embodiment, since a small and inexpensive polarization diffraction element having excellent light use efficiency is used, the same effect as the optical pickup device according to the first embodiment is obtained. Can be obtained.
[0184]
Further, according to the optical disc device of the third embodiment, the position of the optical pickup device itself and the position of the objective lens can be controlled with high accuracy based on the output signal of the optical pickup device 23 ″. It is possible to obtain the same effect as the optical disc device according to the above.
[0185]
In the third embodiment, as shown in FIG. 22, hologram irregularities are formed on an isotropic optical member TK having a large difference in refractive index from the filler 80e. It may be held by a glass plate KG (fourth substrate). For example, when the refractive index of the optical member TK is 1.7, the difference between the refractive index of the optical member TK and the filler 80e is 0.2, and the groove depth of the hologram unevenness can be reduced to 1/4. This facilitates the creation of the hologram concavities and convexities, reduces the operation cost, reduces the variation, and improves the product yield. That is, the material of the hologram may be different from the glass substrate holding the grating. Further, the material of the optical glass plate KG may be the same as or different from the glass substrate holding the grating.
[0186]
Further, in the third embodiment, irregularities (grating irregularities) may be formed on the surface of the glass substrate 80a on the light source unit side, for example, to convert the emitted light beam for CD into three beams. Thereby, miniaturization of the two-wavelength optical pickup device can be promoted. Further, irregularities (hologram irregularities) for branching a return light beam for a CD, for example, may be formed on the surface of the optical glass plate KG on the optical disk side.
[0187]
In the third embodiment, the case where the adhesive for bonding the grating glass disk and the organic stretched film has a refractive index substantially equal to the ordinary light refractive index of the organic stretched film has been described. When the agent layer is extremely thin or when the flatness of the bonding interface is ensured, the refractive index does not necessarily have to be the same as the ordinary light refractive index of the organic stretched film.
[0188]
In the third embodiment, the case where the organic stretched film is used as the material having optical anisotropy has been described, but the present invention is not limited to this. When there is no possibility that the grating is deformed, the glass substrate for holding the grating may not be provided.
[0189]
In each of the above embodiments, the case where the semiconductor laser and the light receiver are individually mounted has been described. However, the present invention is not limited thereto, and the semiconductor laser and the light receiver may be mounted in the same housing. Further, in each of the above embodiments, the case where the light source unit and the polarization diffraction element are individually mounted has been described. However, the present invention is not limited to this, and the light source unit and the polarization diffraction element may be integrated. As a result, it is possible to promote downsizing of the optical pickup device, reduce the number of components at the time of assembling, simplify assembling work and adjustment work, and reduce work costs. Become.
[0190]
In each of the above embodiments, the case where the polarization diffraction element is disposed between the light source unit and the coupling lens has been described. However, the present invention is not limited to this. For example, the output from the light receiver due to the shift of the objective lens is described. When there is a possibility that an offset may be added to the signal, the polarization diffraction element and the objective lens may be integrated. At this time, since the polarization diffraction element is thinner than the conventional one, no major design change is required.
[0191]
Further, in each of the above embodiments, the optical disk device capable of recording and reproducing information has been described. However, the present invention is not limited to this, and any optical disk device capable of at least reproducing among information recording, reproduction, and erasing may be used.
[0192]
Further, in each of the above embodiments, the case where the semiconductor laser is used as the light source has been described, but the present invention is not limited to this.
[0193]
Further, in each of the above embodiments, an information recording medium such as a CD, a DVD, and a magneto-optical disk, which performs at least reproduction among information recording, reproduction, and erasure by using light, can be used as the optical disk.
[0194]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the polarizing optical element which concerns on this invention, there exists an effect that size reduction and cost reduction can be promoted, without reducing light use efficiency.
[0195]
Further, according to the method for manufacturing a polarizing optical element according to the present invention, there is an effect that a small polarizing optical element having excellent light use efficiency can be manufactured at low cost.
[0196]
Further, according to the optical pickup device of the present invention, it is possible to accurately output a signal including information necessary for controlling the position of the optical pickup device itself and the objective lens without increasing the size and cost. This has the effect.
[0197]
Further, according to the optical disc device of the present invention, there is an effect that high-speed access to the information recording medium can be performed accurately and stably.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an optical disc device according to a first embodiment of the present invention.
FIG. 2A is a diagram showing a schematic configuration of an optical system in the optical pickup device 23 in FIG. 1, and FIG. 2B is a detailed configuration of a polarization diffraction element 50 in FIG. 2A. FIG.
FIG. 3 is a diagram for explaining a relationship between an area of a grating area AG and an area of a hologram area AH in the polarization diffraction element 50.
FIGS. 4A and 4B are diagrams for explaining the polarization characteristics of the polarization diffraction element 50, respectively.
FIGS. 5A to 5D are diagrams (part 1) for explaining a method of manufacturing the polarization diffraction element 50. FIGS.
FIGS. 6A to 6D are diagrams for explaining a method of manufacturing the polarization diffraction element 50 (part 2). FIGS.
FIGS. 7A to 7C are diagrams (part 3) for explaining a method of manufacturing the polarization diffraction element 50. FIGS.
FIG. 8A and FIG. 8B are diagrams for explaining an adhesive for bonding a glass substrate and an organic stretched film, respectively.
FIG. 9 is a diagram for explaining the relationship between the type of a member having optical anisotropy and a polarization diffraction element.
FIG. 10 is a diagram for describing an example in which the plate thickness of the first glass substrate is different from the plate thickness of the second glass substrate.
FIGS. 11A and 11B are diagrams for explaining advantages of the polarization diffraction element of FIG. 10;
FIG. 12A is a diagram illustrating a schematic configuration of an optical pickup device according to a second embodiment of the present invention, and FIG. 12B is a diagram illustrating a polarization diffraction element 70 in FIG. FIG. 3 is a diagram for explaining a detailed configuration of FIG.
FIGS. 13A to 13D are diagrams (part 1) for explaining a method of manufacturing the polarization diffraction element 70;
FIGS. 14A to 14D are diagrams (part 2) for describing a method of manufacturing the polarization diffraction element 70. FIGS.
FIGS. 15A to 15C are views (No. 3) for explaining a method of manufacturing the polarization diffraction element 70. FIGS.
FIGS. 16A and 16B are diagrams illustrating the operation of the polarization diffraction element 70 when the optical disc is a DVD.
17 (A) and 17 (B) are diagrams for explaining the operation of the polarization diffraction element 70 when the optical disc is a CD.
FIG. 18 is a diagram for explaining a difference in thickness between the polarization diffraction element 70 and a conventional polarization diffraction element KS.
FIG. 19 is a view for explaining a modification of the polarization diffraction element according to the second embodiment.
20A is a diagram illustrating a schematic configuration of an optical pickup device according to a third embodiment of the present invention, and FIG. 20B is a diagram illustrating the polarization diffraction element 80 in FIG. FIG. 3 is a diagram for explaining a detailed configuration of FIG.
FIG. 21 is a diagram illustrating a case where liquid crystal is used as an optical member having optical anisotropy.
FIG. 22 is a view for explaining a modification of the polarization diffraction element according to the third embodiment.
FIGS. 23A and 23B are diagrams illustrating examples of a conventional diffraction element having no polarization.
FIG. 24 is a view for explaining an example of a conventional polarization diffraction element.
[Explanation of symbols]
15 optical disk (information recording medium), 20 optical disk device, 23 optical pickup device, 28 reproduction signal processing circuit (part of processing device), 40 CPU (part of processing device), 50, 50 ' Polarization diffraction element (polarization optical element), 50a: first glass substrate (first substrate), 50b: grating (first optical member), 50c: hologram (second optical member), 50d: second glass substrate (second Substrate), 50e: Filler (filling member), 51a: Semiconductor laser (light source), 59: Photodetector (photodetector), 60: Objective lens, 70: Polarization diffraction element (polarization optical element), 70a: CD grating (Third unevenness), 70b: CD hologram (fourth unevenness), 71a: first semiconductor laser (light source), 71b: second semiconductor laser (light source), 80: polarization diffraction element (polarization optical element) , 80a: glass substrate (third substrate), 80b: grating (first optical member), 80c: hologram (second optical member), 80e: filler (filling member), AD1: first adhesive ( AD2: second adhesive (adhesive), G1, G2: glass disk (first member), KG: optical glass plate (fourth substrate), M1, M2: organic stretched film (second) Member), UP: UV-curable resin (filling member).

Claims (40)

A polarizing optical element used in an optical pickup device,
A first optical member having first irregularities formed on one surface thereof;
A second optical member having second irregularities formed opposite to the first irregularities;
A filling member filled between the first optical member and the second optical member and having optical isotropy;
A polarizing optical element, wherein at least one of the first optical member and the second optical member is an optical member having optical anisotropy. The polarizing optical element according to claim 1, wherein the filling member is an ultraviolet-curable resin having adhesiveness. The polarizing optical element according to claim 1, wherein the filling member is an adhesive for an optical lens. The pitch of the first unevenness is larger than the pitch of the second unevenness,
The polarizing optical element according to claim 1, wherein an area of the region where the first unevenness is formed is larger than an area of the region where the second unevenness is formed. . The polarization optical element according to claim 1, wherein the first optical member is a grating, and the second optical member is a hologram. The first optical member and the second optical member are both optical members having optical anisotropy,
The polarization optics according to any one of claims 1 to 5, wherein the optical anisotropy of the first optical member and the optical anisotropy of the second optical member have a predetermined relationship. element. 7. The polarization optical element according to claim 6, wherein an extraordinary refractive index of the first optical member and an ordinary refractive index of the second optical member are substantially equal to each other. The polarizing optical element according to claim 7, wherein a refractive index of the filling member is substantially equal to an extraordinary light refractive index of the first optical member or an ordinary light refractive index of the second optical member. The first optical member and the second optical member have substantially the same optical anisotropy,
9. The second optical member according to claim 6, wherein an ordinary ray direction of the second optical member is substantially 90 degrees with respect to an ordinary ray direction of the first optical member. The polarizing optical element according to Item. The polarization optical element according to claim 9, wherein the first optical member and the second optical member are made of the same material. The polarizing optical element according to any one of claims 6 to 10, wherein the first optical member and the second optical member are each made of an organic stretched film. A first substrate disposed on the other side of the first optical member and holding the first optical member;
12. A second substrate which is arranged on a side of the second optical member opposite to a surface on which the second unevenness is formed, and which holds the second optical member. The polarizing optical element according to any one of the above. 13. The polarization optical element according to claim 12, wherein the first substrate and the second substrate have different thicknesses. 14. The first substrate according to claim 12, wherein the first substrate is bonded to the first optical member via an adhesive having a refractive index substantially equal to the ordinary light refractive index of the first optical member. Polarizing optical element. 15. The second optical member according to claim 12, wherein the second substrate is bonded to the second optical member via an adhesive having a refractive index substantially equal to the ordinary light refractive index of the second optical member. The polarizing optical element according to claim 1. The polarizing optical element according to claim 12, wherein the first substrate and the second substrate are made of substantially the same material. 17. The polarization optical element according to claim 16, wherein a material of the first substrate and the second substrate is an optical glass or a transparent resin, respectively. The polarization optical element according to any one of claims 12 to 17, wherein third irregularities are formed on a surface of the first substrate opposite to the first optical member. 19. The polarization optical element according to claim 18, wherein the third unevenness is a grating unevenness, and is optimized for a light flux having a different wavelength from the first unevenness. 20. The polarization optical element according to claim 12, wherein a fourth unevenness is formed on a surface of the second substrate opposite to the second optical member. 21. The polarization optical element according to claim 20, wherein the fourth irregularities are irregularities for a hologram, and are optimized for a light beam having a different wavelength from the second irregularities. The said 1st optical member is an optical member which has optical anisotropy, and the said 2nd optical member is an optical member which has optical isotropy, The Claim 1 characterized by the above-mentioned. 3. The polarizing optical element according to item 1. 23. The polarization optical element according to claim 22, wherein a refractive index of the filling member is substantially equal to an ordinary light refractive index or an extraordinary light refractive index of the first optical member. 24. The polarization optical element according to claim 22, wherein a refractive index of the filling member is different from a refractive index of the second optical member. 25. The polarization optical element according to claim 22, wherein the first optical member is made of an organic stretched film. The polarizing optical element according to any one of claims 22 to 25, further comprising a third substrate disposed on the other side of the first optical member and holding the first optical member. 27. The polarization optic according to claim 26, wherein the third substrate is bonded to the first optical member via an adhesive having a refractive index substantially equal to the ordinary light refractive index of the first optical member. element. 28. The polarization optical element according to claim 26, wherein the second optical member and the third substrate are made of substantially the same material. The polarizing optical element according to any one of claims 26 to 28, wherein the second optical member and the third substrate have different thicknesses from each other. 30. The polarizing optical element according to claim 26, wherein fifth unevenness is formed on a surface of the third substrate opposite to the first optical member. 23. The device according to claim 22, further comprising a fourth substrate disposed on a side of the second optical member opposite to the surface on which the second unevenness is formed, and having a different refractive index from the second optical member. 31. The polarization optical element according to any one of the items 30. 32. The polarization optical element according to claim 31, wherein sixth irregularities are formed on a surface of the fourth substrate opposite to the side of the second optical member. A method for manufacturing a polarizing optical element used in an optical pickup device,
A first step of forming first irregularities on one surface of a first member having optical anisotropy;
A second step of forming second irregularities on one surface of a second member having optical anisotropy or optical isotropy;
A third step of bonding the first member and the second member via an isotropic filling member such that the first unevenness and the second unevenness face each other. Manufacturing method. Prior to the first step,
A fourth step of bonding a first substrate for holding the first member and the first member;
The method for manufacturing a polarizing optical element according to claim 33, further comprising: a fifth step of bonding a second substrate for holding the second member and the second member. 35. The polarization optic according to claim 34, further comprising a sixth step of forming third irregularities on a surface of the first substrate opposite to the first member, prior to the third step. Device manufacturing method. 36. The method according to claim 34, further comprising, before the third step, a seventh step of forming fourth irregularities on a surface of the second substrate opposite to the second member. A method for manufacturing a polarizing optical element. An optical pickup device that irradiates light onto a recording surface of an information recording medium and receives reflected light from the recording surface,
A light source;
32. An objective lens for converging a light beam emitted from the light source on the recording surface, and disposed on an optical path of a light beam emitted from the light source and traveling toward the objective lens. An optical system that includes the polarization optical element according to any one of claims 1 to 3, and guides a return light beam reflected on the recording surface to a predetermined light receiving position;
An optical detector disposed at the light receiving position. An optical pickup device that irradiates light onto a recording surface of a plurality of types of information recording media and receives light reflected from the recording surface,
A plurality of light sources provided individually corresponding to the plurality of information recording media and selectively emitting light beams having different wavelengths;
31. An objective lens for condensing each light beam emitted from the plurality of light sources on the recording surface, and disposed on an optical path of a light beam emitted from the plurality of light sources toward the objective lens. 33. An optical system comprising: the polarization optical element according to any one of 32; and guiding a return light beam reflected by the recording surface to a predetermined light receiving position;
An optical detector disposed at the light receiving position. 39. The optical pickup device according to claim 37, wherein the objective lens and the polarization optical element are integrated. An optical disc device that performs at least reproduction of information recording, reproduction, and erasure on an information recording medium,
An optical pickup device according to any one of claims 37 to 39;
An optical disk device comprising: a processing device that performs at least reproduction among recording, reproduction, and erasure of the information by using an output signal from the optical pickup device.

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