JP2002174711A - Diffraction element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a diffraction element, by which even after the direction of the diffraction element is controlled so as to correctly guide the reflected light from a disk by the diffraction pattern to a detecting part, the angle between the optical axis of a 1/4 wavelength plate included in the diffraction element an the polarization plane of the light from a laser light source is stably approximately 45 deg.. SOLUTION: The diffraction element 3 consists of a 1/4 wavelength plate 6, an upper transparent substrate 11a and a lower transparent substrate 11b stacked to interpose the 1/4 wavelength plate, and a UV-curing polymer member 13a as a diffraction pattern forming plate which has a diffraction pattern on its surface and which is staked on the upper side of the upper transparent substrate 11a. The angle between the optical axis of the diffraction pattern possessed by the diffraction pattern forming plate and the optical axis of the 1/4 wavelength plate 6 is approximately 45 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a diffraction element for use in an optical pickup device incorporated in an apparatus for optically recording or reproducing information on an information recording medium.

[0002]

2. Description of the Related Art An optical disk, which is an information recording medium capable of optically recording or reproducing information, is capable of recording a large amount of information at a high density, and is therefore used in many fields such as audio, video, and computers. An optical pickup device is used for recording and reproducing information on an optical disk. In order to improve the recording / reproducing characteristics of the optical pickup device, it is necessary that more signal light is incident on a photodetector in the optical pickup device. On the other hand, conventionally, signal quality has been improved by employing a polarization optical system.

However, in recent years, due to advances in optical pickup devices and drive technologies, sufficient characteristics can be obtained with less signal light, and the need for miniaturization and cost reduction has increased. A system that does not employ a polarization optical system and employs a simpler optical system has been gaining importance. A typical example is a so-called integrated unit optical system in which a light source and a light detection unit are integrated by using a diffraction element. This integrated unit optical system is basically a very simple one composed of an integrated unit and an objective lens. Further, as the integrated unit optical system, as a variation, a type in which a collimator lens is inserted between the objective lens and the integrated unit, or a type in which a startup mirror is inserted between the objective lens and the integrated unit are considered. Can be FIG. 24 shows an example in which both the collimator lens 7 and the rising mirror 8 are inserted between the objective lens 5 and the integrated unit 4.

As the diffraction element 3 used in the optical system of the integrated unit, a diffraction element 3 made of glass has conventionally been used. However, Japanese Patent Application Laid-Open No. 10-254335 and
As described in Japanese Patent No. 187014, a resin-made one is used, and the use of such a resin-made diffraction element is more expensive than the conventional glass-made one. This is preferable because the cost can be reduced, and the cost in the manufacturing process can be reduced.

On the other hand, in recent years, DVD (Digital Video Dis
In c) and the like, in order to further increase the recording density, the disk thickness should be reduced in parallel with increasing the NA of the objective lens (“NA” means lens aperture ratio = lens radius / focal length). Is planned.

However, the thinning of the disk causes a problem that the birefringence generated at the time of forming the disk increases. Therefore, there is a need for an optical pickup device capable of recording and reproducing information stably even on a disk having a large birefringence.

For example, an optical pickup device disclosed in Japanese Patent Application Laid-Open No. Hei 10-83552 discloses a polarizing optical system which includes a liquid crystal element or a Faraday rotation element capable of controlling the angle of rotation, or a wavelength plate capable of controlling the attitude. With this arrangement, the direction of the plane of polarization is controlled so that the amount of reflected light is maximized even for a disk having a large birefringence. Further, the optical pickup device disclosed in JP-A-6-309690 employs a non-polarizing beam splitter, so that regardless of the degree of birefringence of the disk,
It is stated that the reflected light from the disk can be separated into a light receiving section. Further, by disposing a quarter-wave plate between the non-polarizing beam splitter and the objective lens, it is possible to reduce interference noise between the primary light and the secondary light due to reflection at the resonator end face of the laser light source. And These two
The inventions described in the two publications have in common that an element for generating a phase difference such as a wavelength plate (hereinafter, referred to as a “phase difference generating element”) is provided to mitigate the influence of birefringence of the disk. It is possible.

[0008]

In the optical system using the above-mentioned integrated unit, since no polarizing element is used, even if the polarization state of the reflected light changes due to the birefringence of the disk, the light enters the detector. No adverse effect such as a change in the signal light amount occurs.

However, in practice, due to the influence of the birefringence of the disk, the state of diffraction at the information pits formed on the disk may change, which may affect the signal quality. That is, even in the non-polarization optical system, if the birefringence of the disk is large, there is a problem that the disk reflected light itself, which is the pit diffracted light, fluctuates. In short, the light reflected from the disk fluctuates depending on the relationship between the direction of the plane of polarization of the light incident on the disk and the direction of the optic axis of the birefringence of the disk.

Therefore, even in a non-polarizing optical system, the above-mentioned Japanese Patent Application Laid-Open No. 10-83552 and Japanese Patent Application Laid-Open No.
It is necessary to optimize the polarization state of the light incident on the disk by inserting a phase difference generating element such as a wave plate into the optical system as performed in the optical pickup device described in Japanese Patent Application Publication No. 0-205. However, if a rotation-controllable wave plate or an element for controlling the angle of rotation as described in the above-mentioned publication is newly mounted, the number of parts and the number of parts requiring assembly adjustment are increased. Further, the wavelength plate and the like are more expensive than optical components such as ordinary mirrors, so that the cost of the optical pickup device is increased.

This problem can be solved by mounting a phase difference generating element in an integrated unit described in Japanese Patent Application No. 2000-025234 filed by the present inventor. A structure in which a phase difference generating element is provided inside a diffraction element will be described with reference to FIGS. 25 and 26 as one example of mounting a phase difference generating element in an integrated unit. FIG. 26 is a sectional view showing the structure of the integrated unit 4 used in the integrated unit optical system shown in FIG. 25 in detail.

As shown in FIG. 26, the integrated unit 4
The device includes a diffraction element 3 and a laser body 10. The diffractive element 3 has a multilayer structure, and a core portion thereof includes:
It has a structure in which the phase difference generating element 60 is sandwiched between the transparent substrates 11a and 11b from above and below. Transparent substrate 11
Primer processing layers 14a and 14b are formed so as to further sandwich a and 11b from above and below. UV curable polymer members 13a and 13b are formed so as to further sandwich the upper and lower primer processing layers 14a and 14b from above and below, and the antireflection film 15 is further sandwiched from above and below.
a and 15b are formed. The diffractive element 3 is fixed so as to close the opening of the seal cap 16 of the laser main body 10 via an ultraviolet curable adhesive 18. The laser main body 10 includes a laser light source 1 and a detection unit 2 inside a seal cap 16, and a cap glass 17 at an opening of the seal cap 16 so that light can enter and exit.

FIG. 24 shows a state in which the integrated unit 4 is incorporated in an optical pickup device. The light emitted from the laser light source 1 passes through the diffraction element 3, is converted into parallel light by a collimator lens 7, is bent in a direction perpendicular to the disk 9 by a rising mirror 8, and is irradiated on the surface of the disk 9 by an objective lens 5. Is done. In this optical system, the light incident on the surface of the disk 9 needs to be substantially circularly polarized in order to minimize the fluctuation of the reflected light from the disk as described above. First, the phase difference generated by the phase difference generating element 60 included in the diffraction element 3 is approximately 波長 wavelength, that is, the phase difference generating element 60 Second, the plate 6
That is, the optical axis of the quarter-wave plate 6 is approximately 45 ° with respect to the plane of polarization of the laser beam.

In order to satisfy the second condition, the element including the quarter-wave plate 6 is ostensibly mounted on the seal cap 16.
When mounted on the optical disk, the quarter-wave plate 6 may be rotated and adjusted so that the optical axis of the quarter-wave plate 6 forms approximately 45 ° with respect to the plane of polarization of the laser light, and fixed. However, here, the element including the quarter-wave plate 6 is the diffraction element 3, and the diffraction element 3 has a diffraction pattern provided to guide the reflected light from the disk 9 to the detection unit 2. The direction in which the diffraction pattern should be diffracted is determined by the position of the detection unit 2.

Therefore, conventionally, when the diffraction element 3 is mounted, the attitude of the diffraction element 3 is adjusted while monitoring the optical signal received by the detection unit 2 already installed at a fixed position. Are adjusted and fixed so as to be in an optimal position and posture. When the attitude of the diffraction element 3 is adjusted, the attitude of the quarter-wave plate 6 included therein is also changed at the same time. Therefore, in the adjusted attitude of the diffraction element 3, the optical axis of the quarter-wave plate 6 must be There is no guarantee that the angle is approximately 45 ° with respect to the plane of polarization of the laser light. As this angle deviates from 45 °, the light that reaches the disk 9 moves away from circularly polarized light.

Therefore, the present invention includes the diffraction element even if the direction of the diffraction element is adjusted so that the reflected light from the disk is correctly guided to the detection section by the diffraction pattern included in the diffraction element. It is an object of the present invention to provide a method for manufacturing a diffraction element in which the angle between the optical axis of a quarter-wave plate and the plane of polarization of light from a laser light source stably becomes approximately 45 °.

[0017]

In order to achieve the above object, a diffraction element according to the present invention comprises a quarter-wave plate having an upper surface and a lower surface, and a quarter-wave plate overlying the quarter-wave plate. The disposed upper transparent substrate, the lower transparent substrate disposed so as to overlap the lower side of the quarter-wave plate, and disposed above the upper transparent substrate so as to have a diffraction pattern formed on the surface. A diffraction pattern forming plate, wherein the optical axis of the diffraction pattern of the diffraction pattern forming plate and the optical axis of the quarter-wave plate form an angle of approximately 45 °.

By adopting the above configuration, the polarization plane of the laser beam from the laser light source is made parallel to the optical axis of the diffraction pattern, and the polarization plane of the laser beam and the optical axis of the quarter-wave plate are aligned. It is possible to ensure that the angle formed is approximately 45 °. As a result, the light incident on the disk becomes substantially circularly polarized light, and the fluctuation of the reflected light due to the birefringence of the recording medium can be reduced.

In order to achieve the above object, in one aspect of the method for manufacturing a diffraction element according to the present invention, a quarter-wave plate having an upper surface and a lower surface is overlapped on the upper side of the quarter-wave plate. And a lower transparent substrate disposed below the quarter-wave plate and having an orientation determining side that is a side for determining the direction. With respect to the wavelength substrate, with reference to the azimuth determining side, a diffraction pattern forming azimuth determining step of determining an azimuth for setting the optical axis of the diffraction pattern, and the azimuth determined in the diffraction pattern forming azimuth determining step is an optical axis Forming a diffraction pattern above the upper transparent substrate.

By adopting the above method, the angle between the optical axis of the diffraction pattern and the optical axis of the quarter wavelength substrate can be set to a desired angle. For example, approximately 45 °
By setting the optical axis of the diffraction pattern parallel to the plane of polarization of the laser beam, the laser beam incident on the recording medium can be circularly polarized, and the fluctuation of the reflected light due to the birefringence of the recording medium. Can be reduced.

In the above invention, preferably, the azimuth determining side is parallel to the optical axis of the quarter wavelength substrate.
By adopting this method, when the angle between the optical axis of the diffraction pattern and the optical axis of the quarter-wavelength substrate is set to a desired angle, the optical axis of the diffraction pattern is determined based on the direction of the azimuth determining side. Easy to decide the direction.

In order to achieve the above object, in another aspect of the method of manufacturing a diffraction element according to the present invention, a quarter-wave plate having an upper surface and a lower surface is provided on a top of the quarter-wave plate. The upper transparent substrate arranged in the lower side, comprising a lower transparent substrate placed over the lower side of the quarter-wave plate, measuring the orientation of the optical axis of the quarter-wave plate, A diffraction pattern forming direction determining step of determining an direction for setting an optical axis of the diffraction pattern based on the measurement result; and forming the diffraction pattern such that the direction determined in the diffraction pattern forming direction determining step is set as an optical axis. And forming a diffraction pattern. By adopting this method, even when the optical axis of the quarter-wave plate is unknown, the optical axis of the quarter-wave plate and the optical axis of the diffraction pattern can be at a desired angle. . For example, if the angle is set to approximately 45 °, by making the optical axis of the diffraction pattern parallel to the plane of polarization of the laser beam, the laser beam incident on the recording medium can be circularly polarized, and the birefringence of the recording medium can be obtained. The fluctuation of the reflected light due to the above can be reduced.

Preferably, in the above invention, the diffraction pattern is formed such that the optical axis of the diffraction pattern and the optical axis of the quarter-wavelength substrate form an angle of 45 °. By making the optical axis of the diffraction pattern parallel to the plane of polarization of the laser beam, the plane of polarization of the laser beam and the optical axis of the quarter-wavelength substrate make an angle of 45 °. The incident laser light can be circularly polarized, and the fluctuation of reflected light due to birefringence of the recording medium can be reduced.

Preferably, in the above invention, the formation of the diffraction pattern is performed by disposing an ultraviolet-curable resin and irradiating the resin with ultraviolet rays in a state where the resin is deformed into a shape corresponding to the diffraction pattern, and is cured. By employing this method, a diffraction pattern can be efficiently and uniformly formed.

In the above invention, preferably, the diffraction pattern has a dividing line, and one of the dividing lines is parallel to an optical axis of the diffraction pattern. By adopting this method, even if the optical axis of the diffraction pattern cannot be directly recognized, the direction of the polarization plane of the laser light can be determined based on the dividing line. This is convenient when determining the angle between the two.

In the above invention, preferably, after the diffraction pattern forming step, a dicing step of making the quarter-wavelength substrate circular and dividing by dicing is included. By adopting this configuration, even if the optical axis or the dividing line of the diffraction pattern is formed in any direction at the stage of the quarter wavelength substrate, it is once processed into a circular shape and then divided by dicing. Therefore, what is obtained as a part corresponding to one diffraction element can have a desired geometrical relationship between the outer side and the dividing line.

In order to achieve the above object, an integrated unit according to the present invention comprises a laser light source, a detection unit for detecting light emitted from the laser light source, reflected by a recording medium, and returned, A light source and the detection unit are housed therein, and a seal cap having an opening through which light enters and exits, and covers the opening, and an optical axis of the diffraction pattern and a polarization plane of laser light incident from the laser light source. And the above-described diffraction element arranged so as to be parallel to each other. By employing this configuration, the angle between the polarization plane of the laser beam and the optical axis of the quarter-wave plate can be set to approximately 45 °. As a result, the light incident on the recording medium becomes substantially circularly polarized light, and the fluctuation of the reflected light due to the birefringence of the recording medium can be reduced.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) Before describing a diffraction element according to Embodiment 1 of the present invention,
First, how the angle formed between the optical axis of the quarter-wave plate and the plane of polarization of light from the laser light source stably becomes approximately 45 ° will be examined.

As described above, even when the direction of the diffraction element 3 is adjusted while monitoring the light receiving state by the detector 2,
The optical axis of the diffraction pattern included in the diffraction element 3 should eventually settle in a certain direction determined by the position of the detector 2. Note that the term “optic axis” originally means an axis in a direction in which birefringence does not occur in a birefringent material, and is not a term used for a diffraction pattern. For convenience, the direction perpendicular to the stripe pattern of the diffraction pattern is referred to as the “optical axis of the diffraction pattern”.

Therefore, if the optical axis of the diffraction pattern included in the diffraction element 3 and the optical axis of the quarter-wave plate 6 are always at a constant angle, the light receiving state is monitored by the detector 2 and the diffraction element is monitored. As a result of adjusting the direction of 3, the optical axis of the diffraction pattern should be settled in a fixed direction, and at the same time, the optical axis of the quarter-wave plate 6 should be settled in a fixed direction. Then, when assembling as the integrated unit 4, the polarization plane of the laser light is set at 45 ° with the optical axis of the quarter-wave plate 6 by a known means such as transmitting light from the laser light source 1 to a polarizer. What is necessary is just to set the angle to make.

(Structure) Therefore, as shown in FIG. 1, the diffraction element according to the present embodiment is arranged so as to sandwich the quarter-wave plate 6 from above and below. The transparent substrates 11a, 11b and the transparent substrates 11a, 11
b are arranged from above and below, and are provided with diffraction pattern forming plates 13a and 13b having a diffraction pattern formed on the surface. Further, the diffraction pattern forming plates 13a, 13b
And the optical axis of the quarter-wave plate 6 form an angle of approximately 45 °.

(Function / Effect) With the above-described structure of the diffraction element 3, the polarization plane of the laser beam from the laser light source 1 is simply made parallel to the optical axis of the diffraction pattern, and the polarization plane of the laser beam is The angle between the quarter-wave plate 6 and the optical axis can be reliably set to approximately 45 °. As a result, the light incident on the disk 9 becomes substantially circularly polarized light, and the fluctuation of the reflected light due to the birefringence of the disk 9 can be reduced.

When the integrated unit 4 is constructed by using such a diffractive element 3 with the same structure as that shown in FIG. 26, the light incident on the disk 9 becomes substantially circularly polarized light.
Variations in reflected light due to birefringence of the disk 9 can be reduced.

(Second Embodiment) (Manufacturing Method) In a second embodiment according to the present invention, a method of manufacturing the diffraction element 3 described in the first embodiment will be described. The manufacturing process is the same as the method of manufacturing a diffractive element (hologram element) using an ultraviolet curable resin described in JP-A-10-254335 and JP-A-10-187014, which will be described below.

In this embodiment, as shown in FIG. 2, the quarter-wave plate 6 is sandwiched between two transparent substrates 21a and 21b and bonded to each other and used as the quarter-wave substrate 20.

First, the primer processing step will be described with reference to FIG. In the primer treatment step, the primer liquid 23 is applied to the surface of the quarter-wavelength substrate 20 and spread over the entire surface of the quarter-wavelength substrate 20 by spin coating. Similarly, the primer solution 23 is applied to the back surface and spread over the entire surface by spin coating. Primer solution 23 applied on both sides
Allow to dry. In this step, the ultraviolet curable resin 42 for forming a diffraction pattern is formed on the front and back of the quarter-wavelength substrate 20.
This is a step performed so that a and 42b can easily adhere to each other.

Referring to FIG. 4, 2P (Photo Polymer)
The molding step will be described. This step is performed as shown in FIG.
This is performed using a P molding device 50. The 2P molding device 50
A die set unit 30 is provided. The die set unit includes an upper die set base 31 and a lower die set base 32.
And can be opened and closed. On the side of the upper die set base 31 facing the lower die set base 32, an upper stamper 40 is fixed via a transparent base 33. A lower stamper 41 is fixed to a side of the lower die set base 32 facing the upper die set base 31. Above the die set unit 30, an ultraviolet irradiator 38 for curing the ultraviolet curable resin is disposed.

As shown in FIG. 6, an ultraviolet curable resin 42 is provided on the upper surface of the transparent substrate 21a and the upper surface of the lower stamper 41.
a and 42b are applied respectively. As shown in FIG. 7, the die set unit 30 is closed. That is, the upper die set base 31 and the lower die set base 32 approach by the die set opening / closing Z-axis 36, and the ultraviolet curable resin 42
a, 42b. UV curable resin 42a, 42
b spreads along the quarter-wavelength substrate 20, and the irregularities of the upper stamper 40 and the lower stamper 41 are transferred. FIG.
As shown in FIG. 3, the transparent base 33 and the upper stamper 40 are positioned from above the die set unit 30 by the ultraviolet irradiation device 38.
UV light is irradiated through the UV-curable resin 42a, 4
2b is cured. As shown in FIG. 9, by opening the die set unit 30 by the die set opening / closing Z axis 36, the diffraction grating is patterned on both the front and back surfaces of the quarter-wavelength substrate 20. As a result, the state shown in FIG. 4 is obtained.

FIG. 10 shows the pattern shapes of the upper stamper 40 and the lower stamper 41. The upper stamper 40 and the lower stamper 41 are made of a transparent material, and the diffraction gratings 44 having the same shape are arranged at equal intervals on the surface. FIG.
FIG. 11 shows an enlarged view of one section of 0. The diffraction grating 44 has two diffraction grating regions 45a and 45b composed of grating fringes having different pitches. Diffraction grating area 45
The space between a and 45b is divided by a dividing line 45 extending in a direction perpendicular to these lattice fringes.

As shown in FIG. 12 after the assembly and adjustment, the diffraction grating regions 45a and 45b are for condensing the reflected light from the disk 9 on the segments 2a and 2b of the detection unit 2, respectively. . The detection unit 2 is divided into such a plurality of segments in order to perform signal processing. In order to guide light at diffraction angles corresponding to the segments 2a and 2b at different positions, the diffraction grating regions 45a and 4b
The pitch of 5b is different. The detection unit 2
A position where the division line 45 can be correctly received beforehand when the division line 45 is parallel to the polarization plane of the laser light from the laser light source 1 toward the disk 9 is selected and arranged. Therefore, when the adjustment of the direction of the diffraction element 3 is completed, the dividing line 45
Is naturally parallel to the plane of polarization of the laser beam toward the disk 9.

Returning again to the description of the manufacturing method shown in FIG.
As shown in FIG. 13, a substrate punching step of removing the outside so as to form a circular substrate having only the effective pattern portion is performed. Thus, a circular quarter wavelength substrate 25 is obtained. Antireflection films 15a and 15b are formed on both surfaces.

A dicing step is performed to cut out a diffraction element 3 of an arbitrary size from the circular quarter-wavelength substrate 25 as shown in FIG. As shown in FIG. 11, the upper stamper 40 and the lower stamper 41 have a dicing line 4 at the same time as the diffraction grating 44 as a mark for dicing.
6 are patterned, and in the dicing step, dicing may be performed along the dicing line 46. As is apparent from FIG. 11, the dicing lines 46 are patterned perpendicularly or parallel to the dividing lines 45 of the diffraction grating 44. Therefore, the outer side of the diffraction element 3 obtained after the dicing is perpendicular or parallel to the dividing line 45.

Thus, the diffraction element 3 is obtained. next,
The 2P molding process will be described in detail. This is because there are two types of the quarter-wavelength substrate 20, and the 2P molding process differs depending on which one is used. In other words, there are two cases, one in which the direction of the optical axis of the quarter-wave plate 6 with respect to the outer shape of the quarter-wavelength substrate 20 is known, and the other case.

Example 1 First, an example in which the direction of the optical axis of the quarter-wave plate 6 is known with respect to the outer shape of the quarter-wave substrate 20 will be described. Here, as a further example, when the quarter-wavelength substrate 20 is formed, the optical axis of the quarter-wavelength plate 6 is parallel to one of the outer sides of the transparent substrates 21a and 21b. In the case where it is known that the information is pasted in FIG.
This is performed with reference to FIG.

In performing the 2P molding process, first,
As shown in FIG. 15, the quarter wavelength substrate 20 is mounted on the die set unit 30 in the 2P molding apparatus 100. The quarter wavelength substrate 20 includes a substrate gripping hand 103,
It is gripped by 104. Quarter wavelength substrate 20
Above the three CCs as shown in FIG. 15 and FIG.
The D cameras 101, 105, and 106 are respectively arranged so as to look down at the quarter wavelength substrate 20.

As shown in FIG. 16, the outer sides 22a and 22b of the quarter wavelength substrate 20 are recognized by the CCD camera 101. Next, the division lines 45 of the diffraction grating 44 drawn on the upper stamper 40 are recognized by the other CCD cameras 105 and 106. Here, the image processing device 110 calculates the angle between the outer sides 22a and 22b and the dividing line 45. If this angle is not 45 °, the target value of 4
The difference from 5 °, that is, the correction angle is calculated, and the quarter-wavelength substrate 20 gripped by the substrate gripping hands 103 and 104 (see FIG. 15) is rotated by the correction angle by a driving source (not shown).

Here, the transparent substrates 21a, 21b
The example in which the optical axis of the quarter-wave plate 6 is parallel to any one of the outer sides of FIG. Since the direction of the optical axis of the quarter-wavelength substrate 20 can be derived in consideration of the angle, the correction angle can be calculated based on the derived optical axis, and the rotation can be adjusted similarly.

Thereafter, as described above, the ultraviolet curable resins 42a and 42b are applied to predetermined locations, and the upper
0 and the lower stamper 41 are sandwiched and pressurized to perform patterning.

By such a step, the angle between the outer sides 22a and 22b of the quarter-wavelength substrate 20 and the dividing line 45 becomes 45 °, and the angle between the outer edges 22a and 22b and the optical axis of the quarter-wavelength plate 6 is divided. The angle formed by the line 45 is also 45 °. Therefore, the quarter-wave substrate 20 thus patterned
Therefore, the angle between the outer edge of the diffraction element 3 obtained by cutting out as shown in FIGS. 13 and 14 and the optical axis of the quarter-wave plate 6 is necessarily 45 °.

Example 2 As Example 2, a quarter-wavelength substrate 2
One example in which the direction of the optical axis of the quarter-wave plate 6 with respect to the outer shape of 0 is unknown is described.

As shown in FIG. 17, the quarter wavelength substrate 2
0 is the die set unit 30 in the 2P molding apparatus 150
Attached to The point that the quarter-wavelength substrate 20 is gripped by the substrate gripping hands 103 and 104 is shown in FIG.
Same as 5. However, as shown in FIGS. 17 and 18, two CCD cameras 105 and 106 are arranged above the quarter wavelength substrate 20 so as to look down on the quarter wavelength substrate 20, respectively. Further, as shown in FIG. 18, the phase difference measuring device 200 is arranged so as to sandwich a part of the quarter wavelength substrate 20.

As shown in FIG. 18, the phase difference measuring device 20
By 0, the optical axis of the quarter wavelength substrate 20 is measured. The mechanism of the phase difference measuring device 200 will be described later.

The dividing lines 45 of the diffraction grating 44 drawn on the upper stamper 40 are recognized by the CCD cameras 105 and 106. The angle between the dividing line 45 and the optical axis of the quarter wavelength substrate 20 is calculated by the image processing device 110. If the angle is not 45 °, a difference from the target value of 45 °, that is, a correction angle is calculated, and the substrate gripping hands 103,
The quarter-wavelength substrate 20 gripped by 104 (see FIG. 15) is rotated by a correction angle by a driving source (not shown).

Thereafter, as described above, the ultraviolet curable resins 42a and 42b are applied to predetermined locations, and the upper
0 and the lower stamper 41 are sandwiched and pressurized to perform patterning.

By such a process, the angle between the optical axis of the quarter-wave plate 6 and the dividing line 45 becomes 45 °.
Therefore, the outer edge of the diffraction element 3 obtained by cutting out the quarter-wavelength substrate 20 patterned as described above as shown in FIGS. 13 and 14 and the optical axis of the quarter-wavelength plate 6 are formed. The angle is necessarily 45 °.

(Example 3) Further, as Example 3, another example in which the direction of the optical axis of the quarter-wave plate 6 with respect to the external shape of the quarter-wave substrate 20 is unknown. Will be described.

As shown in FIGS. 19 to 21 (a) and (b), the optical axis of the quarter wavelength substrate 20 is measured by the phase difference measuring device 200, and the quarter wavelength substrate 20 is measured. Is a method for adjusting the outer side of the lens to a desired constant angle with respect to the optical axis. For example, it is convenient to arrange them so as to be parallel or vertical.

Specifically, first, as shown in FIGS. 19 and 20, the quarter-wavelength substrate 20 is
0 XYθ stage 162. The direction of the optical axis 47 of the quarter wavelength substrate 20 is measured by the phase difference measuring device 200. The angle is adjusted by the θ axis of the XYθ stage 162 so that the optical axis 47 is parallel to the dicing direction of the dicing cutter 161 of the dicing device 160. Further, the outer side of the quarter-wavelength substrate 20 is diced as shown by a straight line in FIG. 19 in accordance with the position to be diced along the X and Y axes of the XYθ stage 162.
By performing this operation on four sides, as shown in FIG. 21A, the outer side of the quarter-wavelength substrate 20 and the optical axis 47 are connected.
Even if and were at random angles,
As shown in FIG. 1B, a new quarter-wavelength substrate 20n in which the outer side and the optical axis 47 are parallel or perpendicular can be obtained. If such a quarter-wavelength substrate 20n is obtained, the process can proceed according to Example 1.

(Phase Difference Measuring Apparatus) The above-described phase difference measuring apparatus will be described with reference to FIGS.

As shown in FIG. 22, laser light emitted from a laser light source 201 passes through a polarizer 202, a quarter-wave plate 203, and an analyzer 204 in this order. The light transmitted through the analyzer 204 is received by the power meter 205, and the amount of light is measured.

First, the adjustment before the measurement will be described.
The laser light emitted from the laser light source 201 is linearly polarized light whose polarization plane is unknown. When this laser beam passes through the polarizer 202, the plane of polarization is aligned in a fixed direction. For the sake of simplicity, the direction of this plane of polarization is defined as the X-axis direction. The optical axis of the quarter-wave plate 203 is also adjusted to be in the X-axis direction. In the state after the adjustment, the light transmitted through the quarter-wave plate 203 is linearly polarized light, and the polarization plane direction is the X-axis direction. Next, the analyzer 204 is inserted between the quarter-wave plate 203 and the power meter 205, and the polarization direction of the analyzer 204 is adjusted so as to be in the Y-axis direction perpendicular to the X-axis direction. This adjustment is performed by the analyzer 204.
, And selecting the direction in which the amount of light detected by the power meter 205 is minimized.
In this state, the light transmitted through the analyzer 204 is in the extinction state.

The measuring method will be described with reference to FIG. Between the polarizer 202 and the quarter-wave plate 203,
A quarter wavelength substrate 20 as a sample is inserted. Polarizer 2
Light transmitted through 02 is linearly polarized light in the X-axis direction.
By transmitting this light through the quarter-wavelength substrate 20, if the optical axis of the quarter-wavelength substrate 20 is not equal to the X-axis direction, the light is changed from linearly polarized light to elliptically polarized light. When the elliptically polarized light passes through the quarter-wave plate 203, it becomes linearly polarized light again. In this state of linearly polarized light, the plane of polarization deviates from the X-axis direction and becomes a tilted direction. This direction is the optical axis direction of the quarter wavelength substrate 20. This direction can be specified by rotating the analyzer 204 and selecting the direction in which the amount of light detected by the power meter 205 is minimum.

(Function / Effect) According to the above-described method for manufacturing a diffraction element, the first embodiment can be applied to the case where the direction of the optical axis of the quarter-wavelength substrate 20 is known or unknown. A diffractive element as described can be manufactured.

The above embodiment disclosed this time is an example in all respects and is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes any modifications within the scope and meaning equivalent to the terms of the claims.

[0065]

According to the present invention, since the optical axis of the diffraction pattern and the optical axis of the quarter-wave plate make an angle of approximately 45 °, the polarization plane of the laser light from the laser light source is diffracted. Just by making it parallel to the optical axis of the pattern, the angle between the polarization plane of the laser beam and the optical axis of the quarter-wave plate will be approximately 45 °.
It can be made to be. As a result, the light incident on the recording medium becomes substantially circularly polarized light, and the fluctuation of the reflected light due to the birefringence of the recording medium can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a diffraction element according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a quarter wavelength substrate according to a second embodiment of the present invention.

FIG. 3 is an explanatory view of a first step of a method for manufacturing a diffraction element according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a second step of the method for manufacturing the diffraction element according to the second embodiment based on the present invention.

FIG. 5 is a conceptual diagram of a 2P molding apparatus according to a second embodiment based on the present invention.

FIG. 6 is an explanatory diagram of a third step in the method for manufacturing a diffraction element according to the second embodiment based on the present invention.

FIG. 7 is an explanatory diagram of a fourth step in the method for manufacturing a diffraction element according to the second embodiment based on the present invention.

FIG. 8 is an explanatory diagram of a fifth step in the method for manufacturing a diffraction element according to the second embodiment of the present invention.

FIG. 9 is an explanatory diagram of a sixth step in the method for manufacturing the diffraction element according to the second embodiment based on the present invention.

FIG. 10 is a plan view showing a pattern shape of upper and lower stampers according to a second embodiment of the present invention.

FIG. 11 is an enlarged plan view of one section of the pattern shape shown in FIG. 10;

FIG. 12 is an explanatory diagram showing a state of light collection from a diffraction element to a detection unit after assembly and adjustment.

FIG. 13 is an explanatory diagram of a seventh step in the method for manufacturing a diffraction element in the second embodiment based on the present invention.

FIG. 14 is an explanatory diagram of an eighth step of the method for manufacturing the diffraction element according to the second embodiment based on the present invention.

FIG. 15 is a plan view showing a state in which a quarter-wavelength substrate is mounted in a 2P molding apparatus in Example 1 of Embodiment 2 based on the present invention.

FIG. 16 is a conceptual diagram of a 2P molding apparatus in Example 1 of Embodiment 2 based on the present invention.

FIG. 17 is a plan view showing a state in which a quarter-wavelength substrate is mounted in a 2P molding apparatus in Example 2 of Embodiment 2 based on the present invention.

FIG. 18 is a conceptual diagram of a 2P molding apparatus in Example 2 of Embodiment 2 based on the present invention.

FIG. 19 is a first explanatory diagram showing a state where a quarter-wavelength substrate is mounted on a dicing apparatus in Example 3 of Embodiment 2 based on the present invention.

FIG. 20 is a second explanatory diagram showing a state where a quarter-wavelength substrate is mounted on a dicing device in Example 3 of Embodiment 2 based on the present invention.

FIGS. 21 (a) and (b) are illustrations of dicing for adjusting an optical axis of a quarter-wavelength substrate in Example 3 of Embodiment 2 based on the present invention.

FIG. 22 is an explanatory diagram of adjustment before measurement of the phase difference measurement device according to the second embodiment based on the present invention.

FIG. 23 is a diagram illustrating a measurement method of the phase difference measurement device according to the second embodiment of the present invention.

FIG. 24 is a configuration diagram showing an example of an integrated unit optical system based on a conventional technology.

FIG. 25 is a configuration diagram showing an example in which a phase difference generating element of an integrated unit optical system based on the prior art is provided.

FIG. 26 is a sectional view of an integrated unit according to the related art.

[Explanation of symbols]

1 laser light source, 2 detectors, 2a, 2b segments, 3 diffraction elements, 4 integrated units, 5 objective lenses,
6 Quarter wave plate, 7 Collimator lens, 8 Start-up mirror, 9 Disk, 10 Laser body, 11
a, 11b, 21a, 21b Transparent substrate, 13a, 13
b UV curable polymer member, 14a, 14b primer treatment layer, 15a, 15b antireflection film, 17 cap glass, 18 UV curable adhesive, 20, 20n
Quarter-wave substrate, 22a, 22b outer edge, 23 primer liquid, 25 circular quarter-wave substrate, 30 die set unit, 31 upper die set base, 32 lower die set base, 33 transparent base, 36 Z axis for opening and closing die set, 38 UV irradiation machine, 40 Upper stamper, 41
Lower stamper, 42a, 42b UV curable resin, 4
4 diffraction grating, 45 division line, 45a, 45b diffraction grating area, 46 dicing line, 47 optical axis, 50
2P molding device, 60 phase difference generating element, 100, 150
2P molding device, 101, 105, 106 CCD camera, 110 Image processing device, 160 dicing device, 1
61 dicing cutter, 162 XYθ stage,
200 phase difference measuring device, 201 laser light source (of phase difference measuring device), 202 polarizer, 203 quarter wave plate (of phase difference measuring device), 204 analyzer, 205 power meter.

Claims (9)

[Claims] 1. A quarter-wave plate having an upper surface and a lower surface, an upper transparent substrate disposed on top of the quarter-wave plate, and a lower side of the quarter-wave plate. A lower transparent substrate arranged in an overlapped manner, and a diffraction pattern forming plate arranged in a superimposed manner on the upper transparent substrate and having a diffraction pattern formed on a surface thereof; A diffractive element, wherein the axis and the optical axis of the quarter-wave plate make an angle of approximately 45 °. 2. A quarter-wave plate having an upper surface and a lower surface; an upper transparent substrate disposed on top of the quarter-wave plate; and a lower side of the quarter-wave plate. For a quarter-wavelength substrate comprising a lower transparent substrate arranged in an overlapping manner and having an orientation determining side that is a side for determining the orientation, with reference to the orientation determining side, the optical axis of the diffraction pattern A diffraction pattern forming azimuth determining step of determining an azimuth to set, and a diffraction pattern forming the diffraction pattern above the upper transparent substrate so that the azimuth determined in the diffraction pattern forming azimuth determining step is used as an optical axis. A method for manufacturing a diffraction element, comprising: a forming step. 3. The method according to claim 2, wherein the direction determining side is parallel to an optical axis of the quarter wavelength substrate. 4. A quarter-wave plate having an upper surface and a lower surface, an upper transparent substrate disposed on top of the quarter-wave plate, and a lower surface of the quarter-wave plate. A diffraction pattern comprising a lower transparent substrate arranged in an overlapping manner, measuring the orientation of the optical axis of the quarter-wave plate, and determining the orientation for setting the optical axis of the diffraction pattern based on the measurement result. A method of manufacturing a diffraction element, comprising: a forming direction determining step; and a diffraction pattern forming step of forming the diffraction pattern such that the direction determined in the diffraction pattern forming direction determining step is used as an optical axis. 5. The optical axis of the diffraction pattern and the optical axis of the quarter-wavelength substrate form an angle of 45 °.
The method for manufacturing a diffraction element according to claim 2, wherein the diffraction pattern is formed. 6. The method according to claim 2, wherein the formation of the diffraction pattern is performed by arranging an ultraviolet-curable resin, irradiating ultraviolet rays in a state where the resin is deformed into a shape corresponding to the diffraction pattern, and curing the resin. A method for manufacturing a diffraction element according to any one of the above. 7. The method of manufacturing a diffraction element according to claim 2, wherein the diffraction pattern has a dividing line, and one of the dividing lines is parallel to an optical axis of the diffraction pattern. 8. The method of manufacturing a diffraction element according to claim 2, further comprising, after the diffraction pattern forming step, a dicing step in which the quarter-wavelength substrate is made circular and divided by dicing. 9. A laser light source; a detection unit for detecting light emitted from the laser light source, reflected by a recording medium and returned; and containing the laser light source and the detection unit inside, and receiving light. A seal cap having an opening for performing the operation, and covering the opening, and disposed so that an optical axis of the diffraction pattern and a polarization plane of laser light incident from the laser light source are parallel to each other. An integrated unit, comprising: the diffraction element according to (1).