JP4251606B2 - Polarizing optical element, manufacturing method of polarizing optical element, optical pickup apparatus, and optical disc apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polarizing optical element, a manufacturing method of the polarizing optical element, an optical pickup device, and an optical disk device. More specifically, the polarizing optical element used in the optical pickup device, a manufacturing method of the polarizing optical element, and the polarizing optical element The present invention relates to an optical pickup device using the optical disk device and an optical disk device including the optical pickup device.
[0002]
[Prior art]
In an optical disc apparatus, information is recorded or erased by irradiating a laser beam onto a recording surface of an information recording medium such as an optical disc on which spiral or concentric tracks are formed, and information is recorded based on reflected light from the recording surface. Reproduction is performed. The optical disk device includes an optical pickup device as a device for irradiating the recording surface of the information recording medium with laser light to form a light spot and receiving reflected light from the recording surface.
[0003]
In general, an optical pickup device includes an objective lens, guides a light beam emitted from a light source to a recording surface of an information recording medium, and guides a light beam reflected by the recording surface (return light beam) to a predetermined light receiving position. And a light receiving element arranged at the light receiving position. This light receiving element outputs not only the reproduction information of the data recorded on the recording surface but also a signal including information (servo information) necessary for position control 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 and 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 this 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 a return light beam of one light spot formed on the recording surface (one beam method), or a method of detecting three light spots formed on the recording surface. It can be roughly divided into a method using each return light beam (3-beam method). In the case of using the three beam method, it is necessary to divide the light beam emitted from the light source into three (three beams) 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 a light source into three beams.
[0005]
As an optical pickup device corresponding to a three-beam system, an optical pickup device in which the grating and a hologram for branching the return light beam reflected by the recording surface from the common optical path of the forward path and the return path and guiding it to the light receiving position are integrated. Has been proposed (see Non-Patent Document 1). In this optical pickup device, as shown in FIG. 20A, irregularities having a pitch of 1 to 2 μm are formed for the hologram HM on one surface of the glass substrate GP, and the pitch is 10 to 10 on the other surface. An unevenness of 20 μm is formed for the grating GT. When a return light beam (hereinafter also referred to as a “branch return light beam” for convenience) that is branched by the hologram HM and enters the light receiving surface of the light receiving element PD is incident on the grating GT, the branch return light beam is diffracted by the grating GT. The amount of light received by the element PD is reduced. Therefore, the interval L between the hologram HM and the grating GT is set to about 2 mm so that the branched return light beam does not enter the grating GT. Furthermore, as shown in FIG. 20B, the area of the grating GT is made smaller than the area of the hologram HM, thereby preventing the branched return beam from entering the grating GT. Thereby, miniaturization of the optical pickup device was achieved.
[0006]
Furthermore, an optical head device using a polarizing optical element whose diffraction efficiency differs depending on the polarization state of the incident light beam has been devised (see, for example, Patent Document 1). In the optical head device disclosed in Patent Document 1, as shown in FIG. 21, an isotropic glass substrate GH on which projections and depressions for holograms are formed and isotropic on which projections and projections are formed. A polarizing optical element is used in which the glass substrate GG is integrated so that the concavo-convex surfaces face each other via a filler (for example, liquid crystal) FM having optical anisotropy. Here, one of the two glass substrates has a refractive index approximately 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. The refractive index is almost equal. Thereby, since the light beam emitted from the light source is hardly subjected to the hologram action in the hologram, it is possible to suppress a decrease in the light amount (irradiation light amount) of the light beam condensed on the recording surface. Further, in the hologram, since a larger amount of return light beam is branched than when there is no polarization, the amount of light received by the light receiving element is increased, and the signal level and S / N ratio in the output signal of the light receiving element are increased. Became possible. That is, the light utilization efficiency can be improved. Furthermore, even if the branched return light beam is incident on the grating, it is hardly diffracted by the grating, so that the distance between the hologram and the grating can be reduced.
[0007]
[Patent Document 1]
JP-A-10-68820 (page 2-7, FIG. 1)
[Non-Patent Document 1]
Yukio Kurata and eight others, “Hologram pickup for CD using the three-beam method”, Sharp Technical Journal, Sharp Corporation, September 1989, Vol. 42, p. 45-52
[0008]
[Problems to be solved by the invention]
[0009]
However, in the optical pickup device described in Non-Patent Document 1, since the light beam emitted from the light source LD is also subjected to the hologram action by the hologram HM, the amount of irradiation light is reduced. When this optical pickup device is used exclusively for reproduction, there is no problem as long as the irradiation light amount is about 1 mW. However, when it is used for recording, an irradiation light amount of 10 to 20 mW is required. There is an inconvenience that it is difficult to cope with a high recording speed. In addition, since the rewritable optical disk has a low reflectance, if the amount of irradiation light is small, the amount of the return light beam received by the light receiving element is insufficient, and the signal level and S / N ratio in the output signal of the light receiving element are low. there were. That is, the light utilization efficiency was low.
[0010]
Further, in the optical head device disclosed in Patent Document 1, since the refractive indexes of the glass substrate GH and the glass substrate GG constituting the polarizing optical element are limited, it is difficult to use an inexpensive general-purpose glass substrate. (In particular, a general-purpose glass substrate having a refractive index of 1.8 is generally difficult to obtain), and as a result, there is a disadvantage that a polarizing optical element becomes expensive. In addition, since the materials (particularly hardness) of the glass substrate GH and the glass substrate GG are different from each other, for example, in the manufacturing process of the polarizing optical element, the glass substrate GH, the liquid crystal FM and the glass substrate GG are performed after being integrated. In the cutting operation of cutting out the polarization optical element having the shape and size, it is necessary to change a processing tool (for example, a dicing saw) or change a processing condition (for example, a feeding speed) in the middle of the operation, resulting in productivity. However, there is a disadvantage that the cost is increased and the cost is increased.
[0011]
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 excellent in light utilization efficiency.
[0012]
A second object of the present invention is to provide a manufacturing method for manufacturing a small polarizing optical element excellent in light utilization efficiency at low cost.
[0013]
The third object of the present invention is to provide an optical pickup capable of accurately outputting a signal including information necessary for position control of the optical pickup device itself and the objective lens without causing an increase in size and cost. To provide an apparatus.
[0014]
A fourth object of the present invention is to provide an optical disc apparatus capable of accurately and stably accessing an information recording medium at a high speed.
[0015]
[Means for Solving the Problems]
  From a first viewpoint, the present invention provides:A polarizing optical element used in an optical pickup device, having a first optical member having optical anisotropy and having a first unevenness formed on one surface thereof; facing the first unevenness TheA pitch different from the pitch of the first unevenness.A second optical member having a second unevenness and having an optical anisotropy different from the optical anisotropy of the first optical member; and between the first optical member and the second optical member FilledThe higher refractive index of the ordinary light refractive index and the extraordinary light refractive index is the ordinary light refractive index and the extraordinary light refractive index of the optical member having the smaller concave / convex pitch of the first optical member and the second optical member. Is almost equal to the refractive index of the smaller oneA polarizing optical element comprising: a filling member;
[0016]
  According to this, the first optical member having optical anisotropy and having the first unevenness formed on the surface on one side thereof, and the first unevenness are opposed to each other.A pitch different from the pitch of the first unevennessA second optical member having an optical anisotropy different from the optical anisotropy of the first optical member, wherein the second unevenness is formed,The larger refractive index of the ordinary light refractive index and the extraordinary light refractive index is smaller of the ordinary light refractive index and the extraordinary light refractive index of the optical member having the smaller concave / convex pitch of the first optical member and the second optical member. Is almost equal to the refractive index ofThey are stacked and integrated via a filling member.In this case, for example, when the ordinary refractive index of the filling member and the ordinary optical refractive index of the second optical member are substantially equal, the extraordinary light component in the light beam incident on the second optical member is diffracted, but the ordinary light component is diffracted. Most of the light is transmitted as it is.Accordingly, it is possible to have a polarization characteristic almost as designed, and it is possible to promote downsizing and cost reduction without reducing light utilization efficiency.
[0017]
  From a second viewpoint, the present invention is a polarizing optical element used in an optical pickup device, which has optical anisotropy and has a first concavo-convex formed on one surface thereof. An optical anisotropy different from the optical anisotropy of the first optical member, wherein a second unevenness having a pitch different from the pitch of the first unevenness is formed opposite to the first unevenness; A second optical member having a property; the first optical member is filled between the first optical member and the second optical member, and the smaller one of the ordinary light refractive index and the extraordinary light refractive index is the first optical member. And a filling member substantially equal to the smaller refractive index of the ordinary light refractive index and the extraordinary light refractive index of the optical member having the larger concave-convex pitch of the second optical member.
  According to this, the first optical member having optical anisotropy and having the first unevenness formed on the surface on one side thereof, and the second unevenness being formed facing the first unevenness, The second optical member having an optical anisotropy different from the optical anisotropy of the first optical member has a smaller refractive index of the first optical member and the ordinary light refractive index and the extraordinary light refractive index. The second optical member is laminated and integrated through a filling member that is substantially equal to the refractive index of the smaller one of the ordinary light refractive index and the extraordinary light refractive index of the optical member having the larger uneven pitch. In such a case, for example, when the extraordinary refractive index of the filling member and the extraordinary refractive index of the first optical member are substantially equal, the ordinary light component in the light beam incident on the first optical member is diffracted, but the extraordinary light component is Most of the light is transmitted as it is without being diffracted. Accordingly, it is possible to have a polarization characteristic almost as designed, and it is possible to promote downsizing and cost reduction without reducing light utilization efficiency.
[0018]
  In this case,in frontWhen the pitch of the first unevenness is larger than the pitch of the second unevenness, the area of the region where the first unevenness is formed is larger than the area of the region where the second unevenness is formed. It may be wide.
[0021]
  UpEachIn the polarizing optical element, various members can be considered as the filling member.,in frontThe filling member may be a liquid crystal. In such a case, since a general-purpose product can be used, the material cost of the filling member can be reduced.
[0022]
  UpEachIn polarizing optical elements,in frontThe first optical member may be a grating, and the second optical member may be a hologram. In such a case, for example, even if the polarization optical element is arranged on the common optical path of the light beam forward and return in the optical pickup device, the light beam that has been made into three beams by the grating can pass through the hologram as it is, As a result, a decrease in the amount of irradiated light can be suppressed. In this case, the return light beam diffracted by the hologram can pass through the grating as it is, and as a result, a decrease in the amount of light received by the light receiving element can be suppressed.
[0023]
  UpEachIn polarizing optical elements,in frontA first substrate disposed on the other side of the first optical member and holding the first optical member; and disposed on an opposite side of the surface of the second optical member on which the second unevenness is formed, And a second substrate for holding the second optical member. In such a case, handling becomes easy and, for example, even if oil adheres, it can be easily removed with a solvent or the like without affecting each optical member.
[0024]
  In this case, the first substrate and the second substrate may have the same thickness.,in frontThe first substrate and the second substrate may have different plate thicknesses.
[0025]
  UpEachIn polarizing optical elements,in frontThe first substrate may be bonded to the first optical member via an adhesive having a refractive index substantially equal to either the ordinary light refractive index or the extraordinary light refractive index of the first optical member. .
[0026]
  UpEachIn polarizing optical elements,in frontThe second substrate may be bonded to the second optical member via an adhesive having a refractive index substantially equal to either the ordinary light refractive index or the extraordinary light refractive index of the second optical member. .
[0027]
  UpEachIn polarizing optical elements,in frontThe 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 the case where the first substrate and the second substrate are made of different materials.
[0028]
  In this case,in frontThe material of the first substrate and the second substrate can be optical glass or transparent resin, respectively. In such a case, an inexpensive general-purpose product can be used, and the material cost of the optical member can be reduced.
[0029]
  UpEachIn polarizing optical elements,in frontAt least one of the first optical member and the second optical member can be made of an organic stretched film. In such a case, since the organic stretched film has high transparency, it is possible to suppress a decrease in light utilization efficiency. In addition, since the organic stretched film is inexpensive and can be finely processed accurately and easily, the yield can be improved, and as a result, cost reduction can be promoted. Furthermore, since the organic stretched film has a sheet shape, it is possible to promote downsizing.
[0030]
  UpEachIn polarizing optical elements,in frontThe 3rd unevenness | corrugation can be supposed to be formed in the surface on the opposite side to the said 1st optical member side in the 1st board | substrate.
[0031]
  UpEachIn polarizing optical elements,in frontThe 4th unevenness | corrugation can be made to be formed in the surface on the opposite side to the said 2nd optical member side in the 2nd board | substrate.
[0032]
  From a third viewpoint, the present invention provides:A method of manufacturing a polarizing optical element used in an optical pickup device,Bonding a first substrate for holding a first member having optical anisotropy to the first member; and having an optical anisotropy different from the optical anisotropy of the first member Bonding the second substrate for holding the second member and the second member;Forming first irregularities on one surface of the first member;WorkBefore;No.2nd unevenness is formed on one surface of two membersWorkAbout;Forming third irregularities on a surface of the first substrate opposite to the first member;The optical anisotropy having a predetermined relationship with the optical anisotropy of the first member and the optical anisotropy of the second member so that the first unevenness and the second unevenness face each other. Bonding the first member and the second member through a filling member havingWorkAnd a method for manufacturing a polarizing optical element.
[0033]
  According to this,lightIt becomes possible to manufacture a small polarizing optical element excellent in utilization efficiency at low cost.
[0036]
  UpMakingIn the manufacturing method,The first member and the second member are bonded togetherPrior to the step, a fourth unevenness is formed on the surface of the second substrate opposite to the second member side.WorkThe process can be further included. In such a case, it is possible to manufacture a small-sized polarizing optical element excellent in light utilization efficiency used in the two-wavelength optical pickup device at low cost.
[0037]
  From the fourth viewpoint, the present invention provides:An optical pickup device that irradiates light onto a recording surface of an information recording medium and receives reflected light from the recording surface, comprising: a light source; and an objective lens that focuses a light beam emitted from the light source on the recording surface And arranged on the optical path of the light beam emitted from the light source and directed to the objective lensThe present inventionAnd an optical system that guides the returned light beam reflected by the recording surface to a predetermined light receiving position; and a photodetector disposed at the light receiving position.
[0038]
  According to this,The present inventionTherefore, it is possible to accurately output a signal including information necessary for position control of the optical pickup device itself and the objective lens without causing an increase in size and cost. .
[0039]
  From the fifth viewpoint, the present invention provides:An optical pickup device that irradiates light onto a recording surface of a plurality of types of information recording media and receives reflected light from the recording surface, and is provided corresponding to each of the plurality of information recording media and having different wavelengths A plurality of light sources that selectively emit light beams; an objective lens that condenses each light beam emitted from the plurality of light sources on the recording surface; and light beams emitted from the plurality of light sources and directed toward the objective lens Placed on the streetThe present inventionAnd an optical system that guides the returned light beam reflected by the recording surface to a predetermined light receiving position; and a photodetector disposed at the light receiving position.
[0040]
  According to this,The present inventionBecause of this polarization optical element, a signal containing information necessary for the position control of the optical pickup device itself and the objective lens for a plurality of types of information recording media without causing an increase in size and cost. Can be output with high accuracy.
[0041]
  UpEachIn optical pickup device,in frontThe 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.
[0042]
  From a sixth viewpoint, the present invention provides:An optical disc apparatus that performs at least reproduction of information recording, reproduction, and erasure with respect to an information recording medium,The present inventionAn optical pickup device, and a processing device for performing at least reproduction of recording, reproduction and erasure of the information using an output signal from the optical pickup device.
[0043]
  According to this,The present inventionThe RF signal, servo signal, etc. can be detected accurately and stably based on the output signal from the optical pickup device, resulting in recording, reproducing and erasing information on the information recording medium at a high speed. It is possible to perform access including reproduction at least with high accuracy and stability.
[0044]
DETAILED DESCRIPTION OF THE INVENTION
<< First Embodiment >>
A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic configuration of an optical disc apparatus 20 according to the first embodiment of the present invention.
[0045]
The optical disk apparatus 20 shown in FIG. 1 includes a spindle motor 22, an optical pickup apparatus 23, a laser control circuit 24, an encoder 25, a motor driver 27, a reproduction signal processing circuit 28, a servo controller 33, and the like. 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 the flow of typical signals and information, and do not represent the entire connection relationship of each block. In the first embodiment, as an example, an information recording medium compliant with the DVD standard is used for the optical disc 15.
[0046]
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 reflected light from the recording surface. The configuration of the optical pickup device 23 will be described in detail later.
[0047]
The reproduction signal processing circuit 28 detects a wobble signal, an RF signal, a servo signal (focus error signal, track error signal) and the like based on the output signal of the optical pickup device 23. Then, the reproduction signal processing circuit 28 extracts ADIP (Address In Pregroove) information and a synchronization signal from the wobble signal. The extracted ADIP information is output to the CPU 40, and the synchronization signal is output to the encoder 25. Further, the reproduction signal processing circuit 28 performs demodulation processing, error correction processing, and the like on the RF signal, and then stores the reproduction data 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. During access to the optical disk 15, ADIP information and servo signals are output from the reproduction signal processing circuit 28 at each predetermined timing.
[0048]
The servo controller 33 generates various control signals for controlling the optical pickup device 23 based on the servo signals, and outputs them to the motor driver 27.
[0049]
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.
[0050]
The buffer manager 37 manages input / output of data to / from the buffer RAM 34, and notifies the CPU 40 when the accumulated data amount reaches a predetermined amount.
[0051]
The encoder 25 extracts data stored in the buffer RAM 34 via the buffer manager 37 based on an instruction from the CPU 40, modulates data, adds an error correction code, etc., and generates a write signal to the optical disk 15. At the same time, a write signal is output to the laser control circuit 24 in synchronization with the synchronization signal from the reproduction signal processing circuit 28.
[0052]
The laser control circuit 24 controls the output of the laser light applied to the optical disc 15 based on a write signal from the encoder 25 and an instruction from the CPU 40.
[0053]
The interface 38 is a bidirectional communication interface with a host (for example, a personal computer), and conforms to standard interfaces such as ATAPI (AT Attachment Packet Interface) and SCSI (Small Computer System Interface).
[0054]
The ROM 39 stores a program written in a code readable by the CPU 40. The CPU 40 controls the operation of each unit according to a program stored in the ROM 39 and temporarily stores data necessary for control in the RAM 41.
[0055]
Next, the configuration and the like of the optical pickup device 23 will be described with reference to FIG. 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 (focusing actuator, tracking actuator, seek motor (all not shown)) and the like.
[0056]
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 (the right side in FIG. 2A). In the first embodiment, as an example, the emitted light beam is a P-polarized light beam.
[0057]
The polarization diffractive element 50 is disposed on the + X side of the light source unit 51, converts the emitted light beam into three beams, and branches the return light beam from the recording surface of the optical disc 15 from the common optical path of the forward path and the return path. The configuration and the like of the polarization diffraction element 50 will be described in detail later.
[0058]
The coupling lens 52 is disposed on the + X side of the polarization diffractive element 50, and the light beams converted into three beams by the polarization diffractive element 50 are substantially parallel light. The λ / 4 plate 55 is disposed on the + X side of the coupling lens 52, and adds an optical phase difference of ¼ wavelength to the incident light beam.
[0059]
The objective lens 60 is disposed on the + X side of the λ / 4 plate 55, collects the light beam transmitted through the λ / 4 plate 55, and forms a light spot on the recording surface of the optical disk 15.
[0060]
The light receiver 59 is disposed in the vicinity of the light source unit 51 and receives the return light beam branched by the polarization diffraction element 50. The light receiver 59 includes a plurality of light receiving elements corresponding to the three beam method.
[0061]
Here, the configuration and the like of the polarization diffraction element 50 will be described with reference to FIG. 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 filling member, a hologram 50c as a second optical member, and a second as a second substrate. The glass substrate 50d and the sealing material SE are included.
[0062]
The grating 50b divides the emitted light beam into 0th order light and ± 1st order diffracted light. As the material of the grating 50b, an organic stretched film having optical anisotropy (see Japanese Patent Laid-Open No. 2000-075130) is used. And the predetermined | prescribed unevenness | corrugation is formed in the surface at the side of + X of the organic stretched film (henceforth "the 1st organic stretched film" for convenience). The surface (the −X side 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 through the first glass substrate 50a.
[0063]
The hologram 50 c branches 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 50c, an organic stretched film having optical anisotropy different from that of the first organic stretched film (hereinafter referred to as “second organic stretched film” for convenience) is used. ing. And the predetermined unevenness | corrugation is formed in the surface (surface on the -X side) of the 2nd organic stretched film which opposes the said 1st unevenness | corrugation formation surface. A surface (+ X side 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. Therefore, the return light beam enters the hologram 50c through the second glass substrate 50d.
[0064]
In the first embodiment, as shown in FIG. 3 as an example, the area of the region (hereinafter also referred to as “grating region” for convenience) AG where the unevenness is formed on the first unevenness forming surface is Is set so as to be larger than the area of the region (hereinafter also referred to as “hologram region” for convenience) AH where the unevenness is formed.
[0065]
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.
[0066]
The filler 50e has optical anisotropy and is filled between the grating 50b and the hologram 50c. Here, as an example, it is assumed that the ordinary light refractive index of the filler 50e is set to 1.8 and the extraordinary light refractive index is set to 1.6. The filler 50e can be easily formed by adjusting a display liquid crystal such as a nematic liquid crystal or a smectic liquid crystal, a polymer liquid crystal, a liquid crystal monomer, and a liquid crystal composition, which are used for general purposes. The filler 50e is held between the grating 50b and the hologram 50c by the sealing material SE.
[0067]
Here, since the outgoing light beam is a P-polarized light beam (ordinary light) and the return light beam is an S-polarized light beam (abnormal light), the first organic stretched film is ordinary light different from the ordinary light refractive index of the filler 50e. It has a refractive index and has an extraordinary light refractive index that substantially matches the extraordinary light refractive index of the filler 50e. In the first embodiment, as an example, the first organic stretched film has an ordinary light refractive index of 1.7 and an extraordinary light refractive index of 1.6. The second organic stretched film has an ordinary light refractive index that substantially matches the ordinary light refractive index of the filler 50e, and has an extraordinary refractive index that is different from the extraordinary refractive index of the filler 50e. In the first embodiment, as an example, the second organic stretched film has an ordinary light refractive index of 1.8 and an extraordinary light refractive index of 1.9. It is very easy to impart each optical anisotropy to the organic stretched film. Therefore, as shown in FIG. 4A, the emitted light beam LBp is diffracted by the grating 50b, but is transmitted through the hologram 50c as it is. On the other hand, as shown in FIG. 4B, the return light beam LBs is diffracted by the hologram 50c, but is transmitted as it is by the grating 50b.
[0068]
The diffraction efficiency of the hologram 50c is determined by the product of the difference Δn between the extraordinary light refractive index of the filler 50e and the extraordinary light refractive index of the second organic stretched film and the groove depth d of the unevenness. It is known that the diffraction efficiency becomes maximum when the product becomes equal to ½ of the wavelength. Therefore, in the first embodiment, since the difference Δn is 0.3 and the wavelength is 660 nm, the uneven groove depth d is 1.1 μm. Conventionally, Δn is about 0.1, and the groove depth of the unevenness has exceeded 3 μm.
[0069]
The first glass substrate 50a and the second glass substrate 50d are made of the same material, and inexpensive glass such as BSC7 and quartz glass, which are a kind of optical glass, is used. A transparent resin substrate may be used instead of the first glass substrate 50a and the second glass substrate 50d.
[0070]
Here, an example of a method for manufacturing the polarization diffraction element 50 will be described with reference to FIGS. In practice, a plurality of polarization diffraction elements are manufactured at the same time, but only the portions corresponding to one polarization diffraction element are shown in FIGS. 5 to 7 for convenience.
[0071]
1. A glass disk G1 to be the first glass substrate 50a and an organic stretched film M1 to be the first organic stretched film are attached with the first adhesive AD1 (see FIG. 5A). The glass disk G1 and the organic stretched film M1 have the same diameter (for example, about 10 cm) as that of a normal silicon wafer. Further, the first adhesive AD1 has a refractive index (here, about 1.7) that is substantially the same as the ordinary light refractive index of the organic stretched film M1.
2. A photosensitive resin (hereinafter referred to as “photoresist”) R is uniformly applied to the surface of the organic stretched film M1 using a spin coater (see FIG. 5B).
3. After the grating pattern for grating corresponding to the light beam having a wavelength of 660 nm is transferred to the photoresist R using the exposure device, the photoresist R is developed using the developing device to form the grating pattern by the photoresist R (FIG. 5 (C)). The pitch of this lattice pattern is 10 to 30 μm. FIG. 5C shows one lattice pattern for convenience, but 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. Yes.
4). A portion of the organic stretched film M1 where the photoresist R does not remain is dry-etched using a reactive ion etching device to form a groove having a depth of about 1.0 μm, and then a solvent or gas is used using a cleaning device. The photoresist R is removed. 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).
5). A glass disc G2 to be the second glass substrate 50d and an organic stretched film M2 to be the second organic stretched film are attached with the second adhesive AD2 (see FIG. 6A). The glass disc G2 and the organic stretched film M2 have substantially the same diameter as the glass disc G1 and the organic stretched film M1, respectively. Further, the second adhesive AD2 has a refractive index (here, about 1.8) that is substantially the same as the ordinary light refractive index of the organic stretched film M2.
6). Photoresist R is uniformly coated on the surface of the organic stretched film M2 using a spin coater (see FIG. 6B).
7. After the hologram grating pattern corresponding to the light beam having a wavelength of 660 nm is transferred to the photoresist R using the exposure device, the photoresist R is developed using the developing device to form a grating pattern by the photoresist R (FIG. 6 (C)). The pitch of this lattice pattern is 1 to 5 μm. Although FIG. 6C shows one lattice pattern 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. Yes.
8). A portion of the organic stretched film M2 where the photoresist is not left is dry-etched using a reactive ion etching apparatus to form a groove having a depth of about 1.1 μm, and then a photo is generated using a cleaning device or a solvent or gas. The resist R is removed. Thereby, irregularities having a pitch of 1 to 5 μm and a depth of about 1.1 μm are formed on the surface of the organic stretched film M2 (see FIG. 6D).
9. An alignment agent (for example, polyimide) is applied to the surface of the organic stretched film M1 on which the unevenness is formed and the surface of the organic stretched film M2 on which the unevenness is formed, respectively, and then a predetermined heat treatment is performed.
10. On the surface of the organic stretched film M1 on which the irregularities are formed, the portions corresponding to one polarization diffraction element are surrounded by the sealing material SE (see FIG. 7A). Here, an ultraviolet curable adhesive is used as the sealing material SE. Note that a liquid crystal inlet and an air vent (both not shown) are provided in a part of the sealing material SE in order to fill the concave and convex grooves with liquid crystal in a later step.
11. The organic stretched film M1 and the organic stretched film M2 are overlaid so that the surfaces with the unevenness are opposed to each other (see FIG. 7B).
12 The sealing material SE is cured by irradiating the sealing material SE with ultraviolet rays using an ultraviolet irradiation device.
13. The space between the organic stretched film M1 and the organic stretched film M2 is filled with the liquid crystal UP to which the photopolymerization initiator is added (see FIG. 7C).
14 The liquid crystal UP is irradiated with ultraviolet rays using an ultraviolet irradiation device to polymerize the liquid crystal UP. As a result, a disc (hereinafter referred to as “first laminated disc” for convenience) HP in which the glass disc G1, the organic stretched film M1, the liquid crystal UP, the organic stretched film M2, and the glass disc G2 are laminated and integrated is produced. It is done.
15. The first laminated disk HP is set in a cutting device and cut into predetermined dimensions. Then, the polarization diffraction element 50 is obtained through a finishing process, a cleaning / drying process, an inspection process, and the like. That is, a plurality of polarization diffraction elements 50 can be obtained from one first laminated disk HP.
[0072]
Explaining the operation of the optical pickup device 23 configured as described above, the light beam of linearly polarized light (here, P-polarized light) emitted from the semiconductor laser 51a enters the grating 50b through the first glass substrate 50a. This light beam is split into 0th order light and ± 1st order diffracted light by the grating 50b. Each light beam passes through the hologram 50 c without being subjected to the hologram action, becomes substantially parallel light by the collimator lens 52, is then circularly polarized by the λ / 4 plate 55, and is recorded on the optical disk 15 via the objective lens 60. The light is condensed as a minute spot on the surface. Each reflected light reflected by the recording surface of the optical disk 15 becomes circularly polarized light opposite to the outward path, and is converted into substantially parallel light again by the objective lens 60 as a return beam, and a straight line orthogonal to the outward path by the λ / 4 plate 55. Polarized light (here, S-polarized light) is used. Each return beam passes through the collimator lens 52, is diffracted by the hologram 50c, passes through the grating 50b 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.
[0073]
Next, a processing operation when data is recorded on the optical disk 15 using the optical disk device 20 described above will be briefly described.
[0074]
When the CPU 40 receives a recording request command from the host, it 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. The signal processing circuit 28 is notified. Further, the CPU 40 instructs the buffer manager 37 to store data received from the host (hereinafter referred to as “user data”) in the buffer RAM 34.
[0075]
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 the detection result is used as the servo controller 33. Output to.
[0076]
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 to correct the track deviation. 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 the focus shift. In this way, tracking control and focus control are performed.
[0077]
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 ADIP information extracted from the wobble signal. Based on the ADIP information from the reproduction signal processing circuit 28, the CPU 40 outputs a signal for controlling the seek motor of the optical pickup device 23 to the motor driver 27 so that the optical pickup device 23 is positioned at the designated writing start point. To do. Note that the reproduction signal processing circuit 28 extracts ADIP information at predetermined timings and notifies the CPU 40 of the extracted ADIP information.
[0078]
When the CPU 40 receives a notification 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.
[0079]
When the CPU 40 determines that the position of the optical pickup device 23 is the writing start point based on the ADIP information, the CPU 40 notifies the encoder 25. As a result, user data is recorded on the optical disc 15 via the encoder 25, the laser control circuit 24, and the optical pickup device 23.
[0080]
Next, the processing operation when reproducing the user data recorded on the optical disc 15 using the optical disc apparatus 20 described above will be briefly described.
[0081]
When receiving 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. The signal processing circuit 28 is notified. 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 process. Further, the reproduction signal processing circuit 28 extracts ADIP information and notifies it to the CPU 40 as in the case of the recording process.
[0082]
Based on the ADIP information, the CPU 40 outputs a signal for controlling the seek motor to the motor driver 27 so that the optical pickup device 23 is positioned 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 ADIP information, the CPU 40 notifies the reproduction signal processing circuit 28.
[0083]
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 then stores them in the buffer RAM 34. The buffer manager 37 transfers the reproduction data stored in the buffer RAM 34 to the host via the interface 38 when the reproduction data is prepared as sector data.
[0084]
Note that tracking control and focus control are performed at predetermined timings until the recording process and the reproduction process are completed.
[0085]
As is clear from the above description, in the optical disc apparatus 20 according to the first embodiment, a processing apparatus is realized by the reproduction signal processing circuit 28, the CPU 40, and a 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 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.
[0086]
As described above, the polarization diffraction element 50 according to the first embodiment has optical anisotropy (ordinary refractive index 1.7, extraordinary refractive index 1.6), on the objective lens side. A first organic stretched film having grating irregularities (first irregularities) formed on the surface thereof, and hologram irregularities (second irregularities) opposite to the grating irregularities to form the first The second organic stretched film having optical anisotropy (ordinary refractive index 1.8, extraordinary refractive index 1.9) different from the organic stretched film is different from the optical anisotropy of each organic stretched film. They are integrated via a liquid crystal having optical anisotropy (ordinary refractive index 1.8, extraordinary refractive index 1.6) having a predetermined relationship. The extraordinary refractive index of the liquid crystal is set to be approximately equal to the extraordinary refractive index of the first organic stretched film, and the ordinary refractive index of the liquid crystal is set to be substantially equal to the ordinary refractive index of the second organic stretched film. Therefore, the ordinary light component in the light beam incident on the grating is diffracted, but the extraordinary light component is transmitted as it is without being diffracted, and the extraordinary light component in the light beam incident on the hologram is diffracted, but the ordinary light component Most of the light is transmitted without being diffracted. Accordingly, it is possible to have a polarization characteristic almost as designed, and it is possible to promote downsizing and cost reduction without reducing light utilization efficiency.
[0087]
Further, according to the first embodiment, an organic stretched film is used as a material for the grating and the hologram. Since the organic stretched film has high transparency, the loss of light amount in the polarization diffraction element can be suppressed. That is, a decrease in light utilization efficiency can be suppressed. Moreover, since the organic stretched film is inexpensive, it is possible to reduce the component cost. Furthermore, since the organic stretched film has a sheet shape, it is possible to promote downsizing. Moreover, since the refractive index of the organic stretched film with respect to a light beam having a wavelength of 660 nm is around 1.6, it can be used as a filler by slightly adjusting a general-purpose optical anisotropic material.
[0088]
In addition, according to the first embodiment, since the inexpensive liquid crystal is used as the filler, the component cost can be reduced.
[0089]
Further, according to the first embodiment, since the difference Δn between the extraordinary refractive index of the second organic stretched film and the extraordinary refractive index of the liquid crystal is set to 0.3, the unevenness in the hologram The depth of the groove can be made significantly shallower than before. As a result, the Q value, which is a parameter indicating the degree of volume hologram, is reduced, and the incident angle dependency of diffraction efficiency is reduced. Accordingly, variations in diffraction efficiency are reduced, and the stability of the signal output from the light receiver 59 can be improved.
[0090]
Further, according to the first embodiment, the first glass substrate 50a and the grating 50b are bonded by an adhesive having a refractive index substantially equal to the ordinary refractive index (1.7) of the first organic stretched film. Therefore, as shown in FIG. 8A as an example, when the thickness of the adhesive layer is uneven, the disorder of the planarity at the bonding interface between the grating 50b and the adhesive AD1 with respect to the emitted light beam is corrected. Therefore, it is possible to suppress the deterioration of wavefront aberration in the light spot formed on the recording surface. Similarly, since the second glass substrate 50d and the hologram 50c are bonded by an adhesive having a refractive index substantially equal to the ordinary light refractive index (1.8) of the second organic stretched film, as an example, FIG. As shown in (B), when the thickness of the adhesive layer is not uniform, the planarity disturbance at the bonding interface between the hologram 50c and the adhesive AD2 with respect to the emitted light beam is corrected, and the light formed on the recording surface Deterioration of wavefront aberration at the spot can be suppressed. That is, it is possible to suppress a decrease in light utilization efficiency.
[0091]
Further, according to the first embodiment, since the area of the grating region is set to be larger than the area of the hologram region, the return light beam diffracted by the hologram 50c always passes through the grating region. The light is received by the light receiver 59. As a result, the return light beam diffracted by the hologram 50c passes through the grating 50b with a substantially constant transmittance and is received by the light receiver 59 with almost no disturbance of wavefront aberration. That is, it is possible to reduce the light amount fluctuation and uneven distribution of the diffracted light received by the light receiver 59. Therefore, the stability and reliability of the signal output from the light receiver 59 can be improved.
[0092]
In addition, according to the method for manufacturing a polarization diffraction element according to the first embodiment, the organic stretched film M1 having the grating irregularities and the organic stretched film M2 having the hologram irregularities are made of the same material. Since the polarization diffraction element 50 is cut out from the first laminated disk HP because it is held by the glass substrate, a processing tool (for example, a dicing saw) is replaced during the operation, or processing conditions (for example, a feed rate). There is no need to change. Therefore, productivity can be improved and cost reduction can be promoted.
[0093]
In addition, according to the first embodiment, since the depth of the concave and convex grooves formed on the surface of the organic stretched film M2 can be reduced to about 1/3 compared to the conventional case, in the manufacturing process of the polarization diffraction element In addition, it is possible to shorten the operation time for forming the hologram unevenness on the surface of the organic stretched film M2, improve the yield, and promote cost reduction.
[0094]
Further, according to the first embodiment, since the organic stretched film is used as the material having optical anisotropy in the grating and the hologram, the microfabrication is easy, and the organic stretched film M1 and the organic stretched film M2 are easy to process. Predetermined irregularities can be accurately formed on the surface. Accordingly, the yield can be improved, cost reduction can be promoted, and polarization characteristics can be obtained almost as designed.
[0095]
In addition, according to the optical pickup device according to the first embodiment, since a small and inexpensive polarization diffraction element having excellent light utilization efficiency is used, the optical pickup device does not increase in size and cost. It is possible to output a signal including information necessary for position control of itself and the objective lens with high accuracy.
[0096]
In addition, according to the optical disc device according to the first embodiment, the positions of the optical pickup device itself and the objective lens can be accurately controlled based on the output signal of the optical pickup device, so that information can be recorded at a high speed. Thus, access including at least reproduction among reproduction and erasure can be performed accurately and stably. Furthermore, the downsizing of the optical pickup device can also promote the downsizing of the optical disc device itself and the reduction of power consumption. For example, when used for portable use, it is easy to carry and can be used for a long time. It becomes.
[0097]
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 the same as the ordinary refractive index of the organic stretched film M1 will be described. However, for example, when the adhesive layer is extremely thin or the flatness of the bonding surface is ensured, the refractive index is not necessarily the same as the ordinary refractive index of the organic stretched film M1. Similarly, for the second adhesive AD2 for bonding the glass disk G2 and the organic stretched film M2, for example, when the adhesive layer is extremely thin or the flatness of the joint surface is ensured. The refractive index is not necessarily the same as the ordinary refractive index of the organic stretched film M2.
[0098]
Moreover, although the said 1st Embodiment demonstrated the case where an organic stretched film was used as a material of a grating and a hologram, this invention is not limited to this. However, for example, as shown in FIG. 9, in the case of the polarization diffraction element 50N using lithium niobate LN1 and LN2 as the material of the grating and hologram, a glass substrate is unnecessary, and therefore the polarization diffraction element as a whole is not necessary. It becomes thinner than 50. However, since the total thickness of the members having optical anisotropy is significantly thicker than that of the polarization diffraction element 50, there is a restriction that the polarization diffraction element 50N can be disposed only in the parallel optical path. As an example, as shown in FIG. 9, in the case of the polarization diffraction element 50L using the liquid crystals LC1 and LC2 as the material of the grating and hologram, the total thickness of the members having optical anisotropy is the polarization diffraction element. It becomes thinner than the case of 50. However, since the liquid crystal needs to be sandwiched between the glass plates LG, the entire element is thicker than the polarization diffraction element 50.
[0099]
Moreover, although the said 1st Embodiment demonstrated the case where the 1st glass substrate 50a and the 2nd glass substrate 50d were the same board thickness, it is not restricted to this, The board thickness of the 1st glass substrate 50a and the 2nd glass The board thickness of the substrate 50d may be different from each other. For example, as shown in FIG. 10, instead of the first glass substrate 50a, a first glass substrate 50a ′ that is thicker than the first glass substrate 50a is used, and instead of the second glass substrate 50d, the second glass substrate 50d. Even the polarization diffraction element 50 ′ using the second glass substrate 50d ′ having a smaller plate thickness can be manufactured in the same manner as the polarization diffraction element 50. In this case, the thickness of the first glass substrate 50a 'is thicker than the thickness of the second glass substrate 50d'. Accordingly, as shown in FIG. 11A and FIG. 11B as an example, the distance in the X-axis direction between the hologram (hologram 50c ′) in the polarization diffraction element 50 ′ and the light receiver 59 is the polarization diffraction element. 50 becomes longer than the distance in the X-axis direction between the hologram (hologram 50c) and the light receiver 59, so that the diffraction angle of the hologram in the polarization diffraction element 50 ′ can be made smaller than that in the polarization diffraction element 50. . Therefore, the pitch of the concaves and convexes can be made larger in the hologram 50c ′ than in the hologram 50c. That is, it becomes easy to form hologram irregularities on the surface of the organic stretched film M2, and the yield can be improved.
[0100]
In the first embodiment, the semiconductor laser that emits a light beam having a wavelength of 660 nm is used as the light source. However, the present invention is not limited to this. For example, the light source and the wavelength that emit a light beam having a wavelength of 405 nm are used. Any light source that emits a light beam having a wavelength of 780 nm may be used. However, in that case, the irregularities for the grating and the irregularities for the hologram correspond to the wavelength of the light beam emitted from the light source used.
[0101]
In the first embodiment, the case where an information recording medium conforming to the DVD standard is used as the optical disc 15 has been described. However, the present invention is not limited to this, and a light spot is formed using the three-beam method. Any information recording medium that detects the position may be used.
[0102]
<< Second Embodiment >>
The second embodiment of the present invention will be described below with reference to FIGS.
[0103]
In the second embodiment, the optical disc apparatus is an information recording medium (hereinafter abbreviated as “CD system”) compliant with a CD standard and an information recording medium (hereinafter “DVD system”) compliant with a DVD standard. It is characterized in that each can be accessed. Therefore, as an example, as shown in FIG. 12A, an optical pickup device 23 'corresponding to a two-wavelength light beam is used instead of the optical pickup device 23 in the first embodiment. In this optical pickup device 23 ′, a light source unit 71 that selectively emits two light beams having different wavelengths is used instead of the light source unit 51 in the first embodiment, and 2 instead of the polarization diffraction element 50. A polarization diffraction element 70 corresponding to a light beam having a wavelength is used. Other configurations of the optical pickup device and the optical disk device are substantially the same as those in the first embodiment. Accordingly, the following description will be focused on the differences from the first embodiment, and the same reference numerals will be used for the same or equivalent components as in the first embodiment, and the description thereof will be simplified or omitted. Shall.
[0104]
The light source unit 71 includes a first semiconductor laser 71a serving as a light source that emits a light beam having a wavelength of 660 nm and a second semiconductor laser 71b serving as a light source that emits a light beam having a wavelength of 780 nm. .
[0105]
The polarization diffraction element 70 is a grating that divides a light beam having a wavelength of 780 nm into zero-order light and ± first-order diffraction light (hereinafter also referred to as “CD grating” for convenience), to the polarization diffraction element 50 in the first embodiment. A hologram (hereinafter also referred to as a “CD hologram” for the sake of convenience) for branching the returning light beam having a wavelength of 780 nm in the direction of the light receiving surface of the light receiving element 59 is added. Here, as an example, as shown in FIG. 12 (B), irregularities for the CD grating 70a are formed on the surface on the light source unit 71 side of the first glass substrate 50a, and the coupling lens 52 side of the second glass substrate 50d. Asperities for CD hologram 70b are formed on this surface. That is, the polarization diffraction element 70 includes a grating (hereinafter also referred to as “DVD grating” for convenience) 50b that splits a light beam having a wavelength of 660 nm into zero-order light and ± first-order diffraction light, and a return light beam having a wavelength of 660 nm. A hologram (hereinafter also referred to as “DVD hologram” for convenience) 50c, a CD grating 70a, and a CD hologram 70b are provided. 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 branched by the CD hologram 70b does not enter.
[0106]
Here, a method of manufacturing the polarization diffraction element 70 will be described with reference to FIGS. In practice, a plurality of polarization diffraction elements are manufactured at the same time, but only the portions corresponding to one polarization diffraction element are shown in FIGS. 13 to 15 for convenience.
[0107]
1. Similarly to the case of the polarization diffraction element 50 in the first embodiment, the glass disk G1 and the organic stretched film M1 are bonded with the first adhesive AD1, and then the pitch is 10 to 10 on the surface of the organic stretched film M1. Irregularities for a DVD grating having a thickness of 30 μm and a depth of about 1.0 μm are formed (see FIGS. 5A to 5D).
2. The glass disk G1 is inverted so that it is on the upper side (see FIG. 13A).
3. Photoresist R is uniformly applied on glass disk G1 using a spin coater (see FIG. 13B).
4). After the grating pattern for grating corresponding to the light beam having a wavelength of 780 nm is transferred to the photoresist R using the exposure apparatus, the photoresist R is developed using the developing apparatus to form the grating pattern by the photoresist R (FIG. 13 (C)). Although FIG. 13C shows one lattice pattern for convenience, a plurality of lattice patterns identical to the lattice pattern shown in FIG. 13C are formed on the surface of the glass disc G1. .
5). After dry etching the glass disk G1 where the photoresist R does not remain using a reactive ion etching apparatus, the photoresist R is removed with a solvent or gas using a cleaning apparatus. Thereby, irregularities for the CD grating are formed on the surface of the glass disc G1 (see FIG. 13D).
6). Similarly to the case of the polarization diffraction element 50 in the first embodiment, after the glass disk G2 and the organic stretched film M2 are bonded with the second adhesive AD2, the pitch is 1 to 1 on the surface of the organic stretched film M2. Unevenness for a DVD hologram having a depth of 5 μm and a depth of about 1.1 μm is formed (see FIGS. 6A to 6D).
7. The glass disk G2 is inverted so that it is on the upper side (see FIG. 14A).
8). Photoresist R is uniformly applied on glass disk G2 using a spin coater (see FIG. 14B).
9. A hologram grating pattern corresponding to a light beam having a wavelength of 780 nm is transferred to the photoresist R using an exposure device, and then the photoresist R is developed using a developing device to form a grating pattern by the photoresist R (FIG. 14 (C)). Although FIG. 14C shows one lattice pattern for convenience, a plurality of lattice patterns identical to the lattice pattern shown in FIG. 14C are formed on the surface of the glass disc G2. .
10. After the dry etching of the glass disk G2 where the photoresist R does not remain using a reactive ion etching apparatus, the photoresist R is removed with a solvent or gas using a cleaning apparatus. Thereby, irregularities for the CD hologram are formed on the surface of the glass disc G2 (see FIG. 14D).
11. An alignment agent (for example, polyimide) is applied to the surface of the organic stretched film M1 on which the unevenness is formed and the surface of the organic stretched film M2 on which the unevenness is formed, respectively, and then a predetermined heat treatment is performed.
12 On the surface of the organic stretched film M1 on which the irregularities are formed, the portions corresponding to one polarization diffraction element are surrounded by the sealing material SE (see FIG. 15A). Here, an ultraviolet curable adhesive is used as the sealing material SE. Note that a liquid crystal inlet and an air vent (both not shown) are provided in a part of the sealing material SE in order to fill the concave and convex grooves with liquid crystal in a later step.
13. The organic stretched film M1 and the organic stretched film M2 are overlaid so that the surfaces on which the irregularities are formed face each other (see FIG. 15B).
14 The sealing material SE is cured by irradiating the sealing material SE with ultraviolet rays using an ultraviolet irradiation device.
15. The space between the organic stretched film M1 and the organic stretched film M2 is filled with liquid crystal UP to which a photopolymerization initiator is added (see FIG. 15C).
16. The liquid crystal UP is irradiated with ultraviolet rays using an ultraviolet irradiation device to polymerize the liquid crystal UP. As a result, a disk WP (hereinafter referred to as “second laminated disk” for convenience) WP in which the glass disk G1, the organic stretched film M1, the liquid crystal UP, the organic stretched film M2, and the glass disk G2 are laminated and made is produced. It is done.
17. The second laminated disk WP is set in a cutting device and cut into a predetermined dimension. Then, the polarization diffraction element 70 is obtained through a finishing process, a cleaning / drying process, an inspection process, and the like. That is, a plurality of polarization diffraction elements 70 can be obtained from one second laminated disc WP.
[0108]
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 system will be described.
[0109]
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 beam is hardly divided by the CD grating 70a, and most of the light passes through the CD grating 70a. The light beam that has passed through the CD grating 70a passes through the first glass substrate 50a and is converted into three beams by the DVD grating 50b. Each light beam passes through the DVD hologram 50c and enters the CD hologram 70b. Each light beam that has passed through the CD hologram 70 b becomes substantially parallel light by the collimator lens 52, is then circularly polarized by the λ / 4 plate 55, and is collected as a minute spot on the recording surface of the optical disk 15 via the objective lens 60. To be lighted.
[0110]
Each reflected light reflected by the recording surface of the optical disk 15 becomes circularly polarized light opposite to the outward path, and is converted into substantially parallel light again by the objective lens 60 as a return beam, and a straight line orthogonal to the outward path by the λ / 4 plate 55. Polarized light (here, S-polarized light) is used. Each return light beam passes through the collimating lens 52 and then enters the CD hologram 70b. As shown in FIG. 16B, each return light beam transmitted through the CD hologram 70b is diffracted by the DVD hologram 50c, passes through the DVD grating 50b 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.
[0111]
Next, the case where the optical disk 15 is a CD system will be described.
[0112]
As shown in FIG. 17A, the light beam of linearly polarized light (here P-polarized light) emitted from the second semiconductor laser 71b is converted into three beams by the CD grating 70a, and passes through the first glass substrate 50a. , Enters the DVD grating 50b. Each light beam that has passed through the DVD grating 50b passes through the DVD hologram 50c and enters the CD hologram 70b. Each light beam that has passed through the CD hologram 70 b becomes substantially parallel light by the collimator lens 52, is then circularly polarized by the λ / 4 plate 55, and is collected as a minute spot on the recording surface of the optical disk 15 via the objective lens 60. To be lighted.
[0113]
Each reflected light reflected by the recording surface of the optical disk 15 becomes circularly polarized light opposite to the outward path, and is converted into substantially parallel light again by the objective lens 60 as a return beam, and a straight line orthogonal to the outward path by the λ / 4 plate 55. Polarized light (here, S-polarized light) is used. Each return light beam passes through the collimating lens 52, and then is diffracted by the CD hologram 70b and received by the light receiver 59 through the DVD hologram 50c and the DVD grating 50b, as shown in FIG. 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.
[0114]
Whether the optical disk 15 is a CD system or a DVD system can be determined from the intensity of reflected light from the recording surface. Normally, this determination is performed when the optical disk 15 is inserted into a predetermined position of the optical disk apparatus, that is, at the time of loading. It is also possible to determine the type of the optical disk 15 based on TOC (Table Of Contents) information, PMA (Program Memory Area) information, a wobble signal, and the like recorded in advance on the optical disk 15. Then, the determination result is notified to the laser control circuit, and the laser control circuit selects one of the first semiconductor laser 71a and the second semiconductor laser 71b. In addition, the determination result is also notified to other circuits that perform processing according to the type of the optical disk.
[0115]
In the optical disc apparatus according to the second embodiment, when the optical disc 15 is a DVD system, data recording to the optical disc 15 and data reproduction recorded on the optical disc 15 are performed in the same manner as in the first embodiment. Is done. When the optical disk 15 is a CD system, recording and reproduction are performed in substantially the same procedure as the DVD system, although there are slightly different processes from those of the DVD system.
[0116]
As is clear from the above description, in the optical disc device according to the second embodiment, the 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 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.
[0117]
As described above, according to the polarization diffraction element 70 according to the second embodiment, in the polarization diffraction element 50 according to the first embodiment, the surface of the first glass substrate 50a on the light source side is further used for the CD grating 70a. 18 is formed on the surface of the second glass substrate 50d on the side of the coupling lens, and the unevenness for the CD hologram 70b (fourth unevenness) is formed as an example in FIG. As shown, the size can be reduced as compared with the conventional two-wavelength compatible diffraction element KS. In the diffraction element KS, the light beam emitted from the light source for CD is converted into three beams by the CD grating Gcd, 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 optical disk is branched by the CD hologram Hcd, and the return light beam from the DVD optical disk is branched by the DVD hologram Hdvd. That is, the polarization diffraction element 70 can shorten the interval between the grating and the hologram for both CD and DVD as compared with the conventional case.
[0118]
Further, according to the method of manufacturing a polarization diffraction element according to the second embodiment, the DVD grating, the DVD hologram, the CD grating, and the CD hologram are arranged through the glass substrates made of the same material. When the polarization diffraction element 70 is cut out from the laminated disk WP, there is no need to change a processing tool (for example, a dicing saw) or change a processing condition (for example, a feeding speed) during the operation. Therefore, productivity can be improved and cost reduction of the polarization diffraction element having excellent light utilization efficiency can be realized.
[0119]
In addition, according to the optical pickup device of the second embodiment, since a small and inexpensive dual-wavelength polarization diffraction element with excellent light utilization efficiency is used, the optical disk to be accessed is a CD system and In any DVD system, it is possible to accurately output a signal including information necessary for position control of the optical pickup device itself and the objective lens.
[0120]
In addition, according to the optical disk device according to the second embodiment, the optical pickup device itself and the objective lens are based on the output signal of the optical pickup device, regardless of whether the optical disk to be accessed is a CD system or a DVD system. Therefore, it is possible to accurately and stably perform access including at least reproduction among recording, reproduction, and erasure of information at a high speed with respect to the optical disc.
[0121]
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. For example, the DVD hologram and the CD hologram are individually provided. For example, as shown in FIG. 19, a CD hologram 70b may be formed on a new glass substrate 70c. In this case, after adjusting the position of the DVD hologram and the CD hologram, the second glass substrate 50d and the glass substrate 70c are bonded.
[0122]
Moreover, although the said 2nd Embodiment demonstrated the case where an organic stretched film was used as a material which has optical anisotropy, this invention is not limited to this.
[0123]
Moreover, although the said 2nd Embodiment demonstrated the case where the wavelength of the light beam radiate | emitted from a light source unit was two types, this invention is not limited to this.
[0124]
Moreover, although the said 2nd Embodiment demonstrated the case where the light source which radiate | emits a 660 nm wavelength light source and the light source which radiate | emits a 780 nm wavelength light beam were provided, this invention is not limited to this. For example, instead of any one of the light sources, a light source that emits a light beam having a wavelength of 405 nm may be provided.
[0125]
In the second embodiment, the case where a CD-type and DVD-type information recording medium is used as the optical disc 15 has been described. However, the present invention is not limited to this, and the formation position of the light spot using the three-beam method. Any information recording medium can be used.
[0126]
In each of the above embodiments, the case where liquid crystal is used as the filler 50e has been described, but the present invention is not limited to this. What is necessary is just to have the same optical anisotropy.
[0127]
In each of the above 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 either of them may be formed of an organic stretched film.
[0128]
In each of the above embodiments, the first optical member and the second optical member are described as being held by glass substrates made of the same material. However, the present invention is not limited to this, and the first optical member and the second optical member are held by glass substrates made of different materials. Also good. For example, even if the materials of the glass substrates are different from each other, there is no possibility that productivity is lowered unless there is a great difference in mechanical properties.
[0129]
In each of the above 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 thereto, and for example, when there is no risk of deformation, the first optical member and the second optical member are held by the glass substrate It does not have to be.
[0130]
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 to this, and the semiconductor laser and the light receiver may be mounted in the same casing.
[0131]
Moreover, although each said embodiment demonstrated the case where the light source unit and the polarization | polarized-light diffraction element were mounted separately, not only this but a light source unit and a polarization | polarized-light diffraction element may be integrated. As a result, miniaturization of the optical pickup device can be promoted, the number of components during assembly can be reduced, assembly work and adjustment work can be simplified, and work costs can be reduced. Become. When there is a possibility that an offset is added to the output signal from the light receiver due to the shift of the objective lens, 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, a large design change is not required.
[0132]
In each of the above embodiments, the optical disk apparatus capable of recording and reproducing information has been described. However, the present invention is not limited to this, and any optical disk apparatus capable of reproducing at least information recording, reproduction, and erasure may be used. In short, any optical disk device that controls the position of the optical pickup device itself and the objective lens by the three-beam method may be used.
[0133]
Moreover, although each said embodiment demonstrated the case where a semiconductor laser was used as a light source, this invention is not limited to this.
[0134]
【The invention's effect】
According to the polarizing optical element of the present invention, there is an effect that it is possible to promote downsizing and cost reduction without reducing light utilization efficiency.
[0135]
In addition, 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 excellent in light utilization efficiency can be manufactured at low cost.
[0136]
In addition, according to the optical pickup device of the present invention, it is possible to accurately output a signal including information necessary for position control of the optical pickup device itself and the objective lens without causing an increase in size and cost. There is an effect.
[0137]
In addition, according to the optical disk apparatus of the present invention, there is an effect that the information recording medium can be accessed at high speed with high accuracy and stability.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical disc apparatus according to a first embodiment of the present invention.
2A is a diagram illustrating a schematic configuration of an optical system in the optical pickup device of FIG. 1, and FIG. 2B illustrates a detailed configuration of the polarization diffraction element in FIG. 2A. It is a figure for doing.
FIG. 3 is a diagram for explaining a relationship between an area of a grating region and an area of a hologram region in the polarization diffraction element according to the first embodiment.
FIGS. 4A and 4B are diagrams for explaining polarization characteristics of the polarization diffraction element in the first embodiment, respectively.
FIGS. 5A to 5D are views (No. 1) for describing a method of manufacturing a polarization diffraction element in the first embodiment, respectively.
FIGS. 6A to 6D are views (No. 2) for explaining the method of manufacturing the polarization diffraction element in the first embodiment, respectively.
FIGS. 7A to 7C are views (No. 3) for describing the method of manufacturing the polarization diffraction element in the first embodiment, respectively.
FIGS. 8A and 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 material of the grating and hologram and the size of the element in the polarization diffraction element.
FIG. 10 is a diagram for explaining an example of a polarization diffraction element in which the thickness of the first glass substrate is different from the thickness of the second glass substrate.
FIGS. 11A and 11B are diagrams for explaining the advantages of the polarization diffraction element of FIG.
12A is a diagram showing a schematic configuration of an optical pickup device according to a second embodiment of the present invention, and FIG. 12B is a diagram of the polarization diffraction element in FIG. 12A. It is a figure for demonstrating a detailed structure.
FIGS. 13A to 13D are views (No. 1) for describing a method of manufacturing a polarization diffraction element in the second embodiment, respectively.
FIGS. 14A to 14D are views (No. 2) for describing the method of manufacturing the polarization diffraction element in the second embodiment, respectively.
FIGS. 15A to 15C are views (No. 3) for describing the method of manufacturing the polarization diffraction element in the second embodiment, respectively. FIGS.
FIGS. 16A and 16B are diagrams for explaining the operation of the polarization diffraction element when the optical disc is a DVD system, respectively.
FIGS. 17A and 17B are diagrams for explaining the operation of the polarization diffraction element when the optical disc is a CD system, respectively.
FIG. 18 is a diagram for explaining a difference in thickness between the polarization diffraction element according to the second embodiment and a conventional diffraction element corresponding to two wavelengths.
FIG. 19 is a diagram for explaining a modification of the polarization diffraction element in the second embodiment.
20A and 20B are diagrams for explaining an example of a conventional diffractive element that does not have polarization.
FIG. 21 is a diagram for explaining an example of a conventional polarizing optical element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 15 ... Optical disk (information recording medium), 20 ... Optical disk apparatus, 23,23 '... Optical pick-up apparatus, 28 ... Reproduction signal processing circuit (part of processing apparatus), 40 ... CPU (part of processing apparatus), 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 ... light receiver (photodetector), 60 ... objective lens, 70 ... polarization diffraction element (polarization optical element), 70a ... CD grating, 70b ... CD hologram, 71a ... first semiconductor laser (light source), 71b ... second semiconductor laser (light source), AD1 ... first adhesive (adhesive), AD2 ... second contact Agent (adhesive), G1, G2 ... glass disk (first member), M1, M2 ... organic stretch film (second member), UP ... liquid crystal (filler member).

Claims (20)

A polarizing optical element used in an optical pickup device,
A first optical member having optical anisotropy and having first irregularities formed on one surface thereof;
Opposite the first irregularities, second irregularities having a pitch different from the pitch of the first irregularities are formed, and have an optical anisotropy different from the optical anisotropy of the first optical member. A second optical member;
Filled between the first optical member and the second optical member, and the larger refractive index of the ordinary light refractive index and the extraordinary light refractive index is uneven in the first optical member and the second optical member. And a filling member substantially equal to the smaller refractive index of the ordinary light refractive index and the extraordinary light refractive index in the optical member having the smaller pitch . A polarizing optical element used in an optical pickup device,
A first optical member having optical anisotropy and having first irregularities formed on one surface thereof;
Opposite the first irregularities, second irregularities having a pitch different from the pitch of the first irregularities are formed, and have an optical anisotropy different from the optical anisotropy of the first optical member. A second optical member;
The space between the first optical member and the second optical member is filled, and the smaller one of the ordinary light refractive index and the extraordinary light refractive index is uneven in the first optical member and the second optical member. And a filling member substantially equal to the smaller refractive index of the ordinary light refractive index and the extraordinary light refractive index in the optical member having the larger pitch. The pitch of the first unevenness is larger than the pitch of the second unevenness, and the area of the region where the first unevenness is formed is wider than the area of the region where the second unevenness is formed. The polarizing optical element according to claim 1 or 2 . The filler member polarizing optical element according to any one of claims 1 to 3, characterized in that a liquid crystal. Wherein the first optical member is a grating, a polarizing optical element according to any one of claims 1 to 4, wherein said second optical member is a hologram. A first substrate disposed on the other side of the first optical member and holding the first optical member;
Wherein the said second unevenness formed surface of the second optical member disposed on the opposite side, a second substrate that holds the second optical member; claim 1-5, characterized by further comprising a The polarizing optical element according to any one of the above. The polarizing optical element according to claim 6 , wherein the first substrate and the second substrate have different plate thicknesses. The first substrate is bonded to the first optical member via an adhesive having a refractive index substantially equal to either the ordinary light refractive index or the extraordinary light refractive index of the first optical member. Item 8. The polarizing optical element according to Item 6 or 7 . The second substrate is bonded to the second optical member via an adhesive having a refractive index substantially equal to either the ordinary light refractive index or the extraordinary light refractive index of the second optical member. Item 9. The polarizing optical element according to any one of Items 6 to 8 . The polarizing optical element according to any one of claims 6 to 9 , wherein the first substrate and the second substrate are made of substantially the same material. The polarizing optical element according to claim 10 , wherein the material of the first substrate and the second substrate is optical glass or transparent resin, respectively. Wherein at least one of the first optical member and the second optical member, the polarizing optical element according to any one of claims 1 to 11, characterized in that it consists of an organic stretched film. 13. The polarizing optical element according to claim 6, wherein a third unevenness is formed on a surface of the first substrate opposite to the first optical member side. 14. The polarizing optical element according to claim 6, wherein a fourth unevenness is formed on a surface of the second substrate opposite to the second optical member side. A method of manufacturing a polarizing optical element used in an optical pickup device,
Bonding a first substrate for holding a first member having optical anisotropy and the first member;
Bonding a second substrate for holding a second member having an optical anisotropy different from the optical anisotropy of the first member and the second member;
As engineering that form a first irregularities on one surface of the first member and;
As engineering that form a second irregularity on one surface of the second member and;
Forming third irregularities on a surface of the first substrate opposite to the first member;
The optical anisotropy having a predetermined relationship with the optical anisotropy of the first member and the optical anisotropy of the second member so that the first unevenness and the second unevenness face each other. And a step of bonding the first member and the second member through a filling member having the manufacturing method of the polarizing optical element. Prior to the step of bonding the second member and the first member, characterized in further comprise as engineering that form a fourth irregularities on a surface thereof opposite to the second member side in the second substrate The method for producing a polarizing optical element according to claim 15 . An optical pickup device that irradiates light onto a recording surface of an information recording medium and receives reflected light from the recording surface,
With a light source;
An objective lens for focusing a light beam emitted from said light source to said recording surface, is emitted from the light source according to any one of the light beam according to claim 1 to 12 arranged on an optical path of towards the objective lens An optical system that includes a polarizing optical element and guides the returned light beam reflected by the recording surface to a predetermined light receiving position;
An optical pickup device comprising: a photodetector 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 reflected light 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;
The objective lens which condenses each light beam radiate | emitted from these light sources on the said recording surface, and the optical path of the light beam which is radiate | emitted from these light sources and goes to the said objective lens of Claim 13 or 14 An optical system that includes a polarizing optical element and guides the returned light beam reflected by the recording surface to a predetermined light receiving position;
An optical pickup device comprising: a photodetector disposed at the light receiving position. The optical pickup device according to claim 17 or 18 , wherein the objective lens and the polarizing optical element are integrated. An optical disc apparatus that performs at least reproduction of information recording, reproduction, and erasure with respect to an information recording medium,
An optical pickup device according to any one of claims 17 to 19 ;
An optical disk apparatus comprising: a processing device that performs at least reproduction among recording, reproduction, and erasure of the information using an output signal from the optical pickup device.

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