JP2007052153A - Diffraction element, optical pickup and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diffraction element capable of suppressing absorption of moisture into material constituting a diffraction grating 2 to such a level as to exert no influence on characteristics of diffraction even when being exposed to environments of high temperature and high humidity. <P>SOLUTION: The diffraction element 1 comprising a transparent substrate 3 and the diffraction grating 2 formed on the surface of the transparent substrate 3 is provided with: the transparent substrate 3 in which prescribed transparent protruded members 4 constituting the diffraction grating 2 are disposed on the surface thereof; a transparent protective plate 6; a transparent packed member 5 which is packed between unevenness constituted by the transparent substrate 3 and the protruded member 4, and the transparent protective plate 6; and a sealing member 8 which binds the transparent substrate 3 to the transparent protective plate 6 and annularly surrounds the outside of the packed member 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a diffractive element, an optical pickup equipped with the diffractive element, and an optical disc apparatus.

  Conventionally, a diffraction element has a configuration including a diffraction grating in which a plurality of shallow thin grooves are formed on the surface of a transparent substrate. When light is transmitted through the diffractive element having such a configuration, light interference occurs due to an optical path difference between the concave portion at the bottom of the groove and the convex portion on the surface of the substrate. In order to prevent light interference, a diffraction element having a flat diffraction grating surface has been proposed. 14A is a front view of a conventional diffraction element in which the surface of the diffraction grating is flattened, and FIG. 14B is a plan view of the AA cross section of FIG.

  The transparent substrate 101 is a substrate such as optical glass or optical plastic. It is usually polished so that both the front and back surfaces are flat. The concavo-convex member 102 is a transparent resin containing an organic substance 105 having light absorption in a predetermined wavelength range. The uneven member 102 includes a resist material. The organic substance 105 has light absorption in a predetermined wavelength range. Among these, those that absorb light in the visible light region and dissolve in the uneven member 102 at the molecular level are dyes, and those that absorb light in the visible light region and are dispersed in the uneven member 102 in the particle state are called pigments. . The filling member 103 is a transparent resin that does not contain the organic substance 105, and fills the unevenness of the uneven member 102. The filling member 103 includes a photopolymer or the like. The transparent protective plate 104 is a substrate such as optical glass or optical plastic, and not only protects the filling member 103 and the concavo-convex member 102 but also serves to keep the thickness of the member including the filling member 103 and the concavo-convex member 102 constant. Bear. That is, the diffraction grating 106 fills the unevenness of the uneven member 102 and the uneven member 102 which are sandwiched between the transparent substrate 101 and the transparent protective plate 104 and is a transparent resin containing an organic substance 105 having light absorption in a predetermined wavelength range. It is the structure provided with the filling member 103. The diffraction grating 106 has a flat surface on both the transparent substrate 101 side and the transparent protective plate 104 side, and the combined thickness of the filling member 103 and the concavo-convex member 102 is constant. The diffraction element 107 includes a diffraction grating 106 having a flat surface on a transparent substrate 101, and the diffraction grating 106 is sandwiched between the transparent substrate 101 and the transparent protective plate 104 in this conventional example.

When the predetermined wavelength range of light absorption of the organic material 105 is slightly shorter than the wavelength λ1 of the wavelengths λ1 and λ2 (λ1 <λ2) used as the diffraction grating 106, the refractive index n1 (λ1) of the concavo-convex member 102 at the wavelengths λ1 and λ2 ), N1 (λ2) changes with respect to the case where the organic substance 105 is not included. The amount of change is larger at wavelength λ1 than at wavelength λ2. By properly selecting the materials of the concavo-convex member 102, the organic substance 105, and the filling member 103, the refractive index n1 (λ1) of the concavo-convex member 102 and the refractive index n2 (λ1) of the filling member 103 are substantially the same at the wavelength λ1, and the wavelength λ2 Thus, the refractive index n1 (λ2) of the concavo-convex member 102 and the refractive index n2 (λ2) of the filling member 103 can be made different. As a result, the diffraction grating 106 does not function as a diffraction grating at the wavelength λ1, but can function as a diffraction grating at the wavelength λ2, and can be separated into ± first-order light,. That is, a wavelength selective diffraction grating can be obtained. For the diffraction element 107 having such a configuration, refer to (Patent Document 1) and (Patent Document 2).
JP 2002-318306 A JP 2002-350625 A

  However, when the diffractive element having the conventional configuration is exposed to a high temperature and high humidity environment, the diffraction efficiency may change from the initial state. This is because, as a result of moisture entering from the gap between the transparent substrate and the transparent protective plate, at least one of the concavo-convex member or the filling member of the diffraction grating absorbs moisture and its refractive index changes.

  The present invention solves the conventional problems, and can provide a diffraction element, an optical pickup, and an optical pickup that can suppress the absorption of moisture in a material constituting the diffraction grating to a level that does not affect the diffraction characteristics even when exposed to a high-temperature and high-humidity environment. An object is to provide an optical disk device.

  The present invention is a diffraction element comprising a transparent substrate and a diffraction grating formed on the surface of the transparent substrate, the transparent substrate on which a predetermined transparent convex member constituting the diffraction grating is disposed, A transparent filling member that is filled between the transparent protective plate, an unevenness constituted by the transparent substrate and the convex member, and the transparent protective plate to constitute the diffraction grating, and the transparent substrate and the transparent protective plate And a sealing member that annularly surrounds the outer side of the filling member.

  Since the convex member and the filling member constituting the diffraction grating are surrounded by the transparent substrate, the transparent protective plate, and the sealing member, they are blocked from the outside. Therefore, it is possible to minimize the amount that the convex member and the filling member absorb moisture in the air.

  The diffraction element of the present invention can suppress the amount of moisture in the air that the material constituting the diffraction grating absorbs to a level that does not affect the diffraction characteristics, so that the diffraction characteristics can be maintained even when exposed to high-temperature and high-humidity environments. stable.

  According to a first aspect of the present invention, there is provided a diffractive element comprising a transparent substrate and a diffraction grating formed on the surface of the transparent substrate, wherein the predetermined transparent convex member constituting the diffraction grating is disposed on the surface. And connecting the transparent substrate and the transparent protective plate between the transparent protective plate, the transparent substrate and the transparent protective plate filled with the convex and concave portions constituted by the convex member and the transparent protective plate constituting the diffraction grating. And a sealing member that annularly surrounds the outer side of the filling member.

  Since the convex member and the filling member constituting the diffraction grating are surrounded by the transparent substrate, the transparent protective plate, and the sealing member, they are blocked from the outside. Therefore, it is possible to minimize the amount that the convex member and the filling member absorb moisture in the air. As a result of suppressing the amount of the moisture constituting the diffraction grating that absorbs moisture in the air to a level that does not affect the diffraction characteristics, the diffraction characteristics are stable even when exposed to high-temperature and high-humidity environments.

  A second invention is the diffraction element according to the first invention, wherein the water absorption rate of the sealing member is not more than the water absorption rate of the filling member.

  The range of selection of the filling member is expanded.

  A third invention is the diffraction element according to the first invention, wherein an organic substance having light absorption in a predetermined wavelength region is included in either the convex member or the filling member.

  A diffraction element having a wavelength selective diffraction grating can be obtained.

  A fourth invention is a diffraction element comprising a transparent substrate and a diffraction grating formed on the surface of the transparent substrate, a transparent diffraction grating member having two refractive indexes constituting the diffraction grating, and a diffraction grating member A diffraction element comprising: a transparent protective plate disposed on the front surface side; and a sealing member that connects the transparent substrate and the transparent protective plate and surrounds the outside of the diffraction grating member in an annular shape.

  Manufacture is easy because it is not necessary to physically create the uneven shape. Further, the diffraction grating is protected by the transparent protective plate.

  A fifth invention is the diffraction element according to the fourth invention, wherein the water absorption rate of the sealing member is equal to or lower than the water absorption rate of the diffraction grating member.

  The range of selection of the diffraction grating member is expanded.

  A sixth invention is characterized in that, in the fourth invention, the diffraction grating member includes an organic substance having light absorption in a predetermined wavelength range, and the organic substance in one refractive index region has lost at least part of light absorption. Diffraction element.

  Regions having different refractive indexes can be made without producing irregularities, so that production is easy and inexpensive.

  According to a seventh aspect of the present invention, in a diffraction element comprising a transparent substrate and a diffraction grating formed on the surface of the transparent substrate, a transparent diffraction grating member having two refractive indexes constituting the diffraction grating, and a diffraction grating member And a transparent sealing member that covers the diffraction element.

  Since the surface of the diffraction grating itself is flat and a transparent protective plate can be dispensed with, the manufacturing cost can be reduced accordingly.

  An eighth invention is the diffraction element according to the seventh invention, wherein the water absorption rate of the sealing member is not more than the water absorption rate of the diffraction grating member.

  The range of selection of the diffraction grating member is expanded.

  A ninth invention is characterized in that, in the seventh invention, the diffraction grating member includes an organic substance having light absorption in a predetermined wavelength region, and the organic substance in one refractive index region has lost at least part of light absorption. Diffraction element.

  Regions having different refractive indexes can be made without producing irregularities, so that production is easy and inexpensive.

  According to a tenth aspect of the present invention, in a diffraction element comprising a transparent substrate and a diffraction grating formed on the surface of the transparent substrate, a transparent substrate having predetermined irregularities forming the diffraction grating formed on the surface, a transparent protective plate, A transparent filling member that is filled between the unevenness of the transparent substrate and the transparent protective plate to form a diffraction grating, and a sealing member that connects the transparent substrate and the transparent protective plate and surrounds the outer side of the filling member in an annular shape, A diffractive element comprising:

  Since the concavo-convex shape is formed by the transparent substrate itself, a stable concavo-convex shape can be obtained. In addition, an optimum diffraction grating can be designed for a single wavelength.

  An eleventh invention is the diffraction element according to the tenth invention, wherein the water absorption rate of the sealing member is equal to or lower than the water absorption rate of the filling member.

  The range of selection of the filling member is expanded.

  A twelfth invention is an optical pickup comprising the diffraction element according to any one of the first invention, the fourth invention, the seventh invention, and the tenth invention.

  The installed diffractive element can suppress the absorption of moisture to a level that does not affect the diffraction characteristics of the material that constitutes the diffraction grating so that it can diffract even when exposed to high temperature and high humidity environments. The characteristics are stable. For this reason, the optical pickup of the present invention is also stable because the characteristics of information recording and reproduction with respect to the optical disk are hardly changed.

  A thirteenth aspect of the invention is an optical disc apparatus comprising the optical pickup of the twelfth aspect of the invention.

  Characteristics of information recording and reproduction with respect to the optical disk of the optical pickup to be mounted are not easily changed. For this reason, the optical disk apparatus of the present invention is also stable because the characteristics of information recording and reproduction with respect to the optical disk hardly change.

(Embodiment 1)
The first embodiment will be described with reference to the drawings. FIG. 1A is a front view of the diffraction element according to the first embodiment, and FIG. 1B is a plan view of the AA cross section of FIG.

  The transparent substrate 3 is a substrate such as optical glass or optical plastic. In the present invention, the term “transparent” means that light in the wavelength region in which the diffraction element is used is substantially transmitted. The transparent substrate 3 is usually polished so that both the front surface and the back surface are flat. The transparent substrate 3 has a cylindrical shape or a rectangular parallelepiped shape, but may have other shapes such as an elliptical column, a rounded rectangular column, a C chamfered shape, or a R chamfered shape by design.

  The convex member 4 is a transparent resin containing an organic substance 7 having light absorption in a predetermined wavelength range. The convex member 4 includes an epoxy-based thermosetting adhesive such as Epo-Teks 310, 320, and 330, an acrylic ultraviolet curable adhesive such as OG114, a photosensitive polyimide such as PIMEL7640, and a resist such as AZ6130.

  The organic substance 7 has light absorption in a predetermined wavelength range. Among these, those having light absorption in the visible light region and dissolved in the convex member 4 at the molecular level are dyes, those having light absorption in the visible light region and dispersed in the convex member 4 in the particle state It is called a pigment. The organic matter 7 includes those having light absorption outside the visible light region. When the predetermined wavelength range of light absorption of the organic material 7 is slightly shorter than the wavelength λ1 of the wavelengths λ1, λ2 (λ1 <λ2) used as the diffraction grating 2, the refractive index n1 (λ1 of the convex member 4 at the wavelengths λ1 and λ2 ), N1 (λ2) changes with respect to the case where the organic substance 7 is not included. The amount of change is larger at wavelength λ1 than at wavelength λ2. By properly selecting the materials of the convex member 4, the organic substance 7, and the filling member 5, the refractive index n1 (λ1) of the convex member 4 and the refractive index n2 (λ1) of the filling member 5 are made substantially the same at the wavelength λ1, and the wavelength λ2 Thus, the refractive index n1 (λ2) of the convex member 4 and the refractive index n2 (λ2) of the filling member 5 can be made different. As a result, the diffraction grating 2 does not function as a diffraction grating at the wavelength λ1 and allows only the 0th-order light to pass therethrough, but at the wavelength λ2, it functions as a diffraction grating and separates into ± first-order light,. Can be made. That is, a wavelength selective diffraction grating can be obtained.

  Therefore, the organic substance 7 is selected according to the wavelength range in which the diffraction element is used. Assuming that the wavelengths to be used are λ1 and λ2 (λ1 <λ2), the organic matter 7 has light absorption in a wavelength region shorter than the wavelength λ1 and the wavelength λ1 is about 650 nm. . Further, copper chlorophyllin sodium or the like may be used in the case where the light absorption is in a wavelength region shorter than the wavelength λ1 and λ1 is about 405 nm. Furthermore, it is good also as NK-4432, NK-4489, NK-2911, etc. by Hayashibara Biochemical Laboratories Co., Ltd. as a case where it has optical absorption in a wavelength range longer than wavelength λ2 and wavelength λ2 is about 780 nm. The above is dissolved in the convex member 4 at the molecular level, but pigments such as pigment red 254 and pigment red 177 may be used. The organic substance 7 may be a mixture of a plurality of types of organic substances in order to provide light absorption in a predetermined wavelength range. The convex member 4 appears colored when it contains a dye or pigment, but is transparent because it transmits light of wavelengths λ1 and λ2.

  The filling member 5 is a transparent resin that does not contain the organic substance 7, and fills the unevenness formed by the convex portion formed by the convex member 4 and the concave portion that is the surface of the transparent substrate 3. Examples of the filling member 5 include epoxy thermosetting adhesives such as Epo-Teks 310, 320, and 330, acrylic ultraviolet curing adhesives such as OG114, photosensitive polyimide such as PIMEL7640, and resists such as AZ6130.

  The transparent protective plate 6 is a substrate such as optical glass or optical plastic, and not only protects the filling member 5 and the convex member 4, but also serves to keep the thickness of the combined member of the filling member 5 and the convex member 4 constant. Bear. That is, the diffraction grating 2 fills the convex and concave portions of the convex member 4 and the convex member 4 which are sandwiched between the transparent substrate 3 and the transparent protective plate 6 and are a transparent resin containing an organic substance 7 having light absorption in a predetermined wavelength range. The filling member 5 is provided. The diffraction grating 2 has a flat surface on both the transparent substrate 3 side and the transparent protective plate 6 side, and the combined thickness of the filling member 5 and the convex member 4 is constant. The diffraction element 1 includes a diffraction grating 2 having a flat surface on a transparent substrate 3, and the diffraction grating 2 is sandwiched between the transparent substrate 3 and the transparent protective plate 6 in the first embodiment.

  The sealing member 8 surrounds the periphery of the diffraction grating 2 together with the transparent substrate 3 and the transparent protective plate 6 so that the material constituting the diffraction grating 2 is not exposed to the surrounding air. Accordingly, the water absorption rate of the sealing member 8 is preferably small. In particular, it is desirable to use a material having a water absorption rate lower than that of the filling member 5. However, the material of the sealing member 8 may be the same as that of the filling member 5. Therefore, epoxy thermosetting adhesives such as Epo-Teks 310, 320, and 330, acrylic ultraviolet curing adhesives such as OG114, photosensitive polyimides such as PIMEL7640, resists such as AZ6130, and the like are used. For example, when a material as the filling member 5 is selected from the above materials from the optical characteristics, the sealing member 8 may be selected from a material having a water absorption rate equal to or lower than the water absorption rate of the filling member 5. By doing so, it is not necessary to consider the water absorption rate of the filling member 5, so the range of selection of the filling member 5 is expanded. Furthermore, it is more preferable that the water absorption rate of the sealing member 8 is equal to or lower than the water absorption rate of the convex member 4. This is because the diffraction grating 2 is formed even though the convex member 4 is covered with the filling member 5, and the change in the refractive index can be more reliably suppressed. Here, the water absorption is the mass change rate before and after being left in pure water at 100 ° C. for 2 hours.

  Since the sealing member 8 is a place where neither the light with the wavelength λ1 nor the light with the wavelength λ2 is incident, the sealing member 8 need not be a transparent material as described above.

  Next, a manufacturing method will be described. First, the convex member 4 containing the organic substance 7 is applied to the transparent substrate 3 with a predetermined uniform thickness by spin coating or the like. Next, it is heated and held and cured. Next, a predetermined convex pattern is formed on the convex member 4. As a method for producing the convex pattern, for example, there is a method in which a resist is applied as the convex member 4, ultraviolet rays are irradiated through a mask pattern so as to form a predetermined pattern, and dry etching is performed after development. Alternatively, a photosensitive material may be used as the convex member 4, applied to a predetermined uniform thickness, and developed by irradiating ultraviolet rays through a mask pattern so as to form a predetermined pattern. The height of the convex shape by the convex member 4 is the depth of the diffraction grating 2. Next, the filling member 5 is applied so as to fill between the convex shape by the convex member 4. At this time, the amount and position of application are controlled so that the filling member 5 is not applied to unnecessary portions. Similarly, the sealing member 8 is applied by controlling the amount and position. Examples of the application of the filling member 5 and the sealing member 8 include a screen printing method. The transparent protective plate 6 is superposed on it and the whole is heated and held. The filling member 5 and the sealing member 8 strongly bond the transparent substrate 3, the convex member 4, and the transparent protective plate 6. Finally, it is cut to a predetermined dimension and completed.

  Moreover, when the viscosity before hardening of the sealing member 8 is low, it can also be set as the following manufacturing methods. After a predetermined convex shape by the convex member 4 is formed on the surface of the transparent substrate 3, only the filling member 5 is applied, the transparent protective plate 6 is overlaid thereon, and the whole is heated and held. Next, using the capillary phenomenon from the gap between the transparent substrate 3 and the transparent protective plate 6, the sealing member 8 is injected over the entire circumference under normal pressure or reduced pressure, and the whole is heated and held to be cured. Then, it cuts into a predetermined dimension and is completed.

  In general, the organic substance 7 dissolved in the convex member 4 at a molecular level including a dye tends to lose a predetermined light absorption property because a part of the structure is destroyed by ultraviolet rays. Therefore, the convex member 4 containing the organic substance 7 having a predetermined light absorption property can be formed by using the convex member 4 that leaves a portion that is not exposed to ultraviolet rays when irradiated and developed with ultraviolet rays.

  In FIG. 1, the filling member 5 and the sealing member 8 are described so as to have a gap, but it is not necessary to provide a gap. The sealing member 8 may be in contact with the entire outside of the filling member 5, or the filling member 5 and the sealing member 8 may not be in contact with each other. However, it is not preferable that the materials of the filling member 5 and the sealing member 8 are mixed. This is because the sealing member 8 may adversely affect the optical characteristics including the refractive index of the filling member 5.

  Further, the sealing member 8 needs to cover the entire outer periphery of the diffraction grating 2. This is because, if there is even a slight gap, moisture may enter the diffraction grating 2 together with the surrounding air from there to change the refractive index of at least one of the filling member 5 or the convex member 4.

  In the first embodiment, the convex member 4 includes the organic matter 7. However, the present invention is not limited to this, and the filling member 5 may include the organic material 7. Further, neither the convex member 4 nor the filling member 5 may contain the organic matter 7. When the filling member 5 includes the organic substance 7, even if the convex member 4 is irradiated with ultraviolet rays through the mask pattern, the organic substance 7 is not included, so that the light absorption property is not lost. Therefore, the range of selection of the material of the convex member 4 and the organic substance 7 is expanded. Moreover, since the filling member 5 containing the organic substance 7 is cured without using ultraviolet rays, there is no inconvenience. On the other hand, when neither the convex member 4 nor the filling member 5 contains the organic matter 7, it can function as the diffraction element 1 having at least a single wavelength by providing a difference between the refractive index n1 of the convex member 4 and the refractive index n2 of the filling member. . Therefore, the degree of freedom in designing the diffraction element is great. Further, since the organic matter 7 is not included in the first place, there is no need to worry about deterioration of a predetermined light absorption property due to partial destruction of the structure of the organic matter 7 due to ultraviolet irradiation.

  In addition, although the planar shape of the diffraction grating 2 is shown to be a substantially square shape, it is not limited thereto, and may be a circular shape, an elliptical shape, a polygonal shape, or the like. Moreover, although it arrange | positioned so that each of the convex member 4 of the diffraction grating 2 may be located in a stripe form, it is not restricted to it and arrangement | positioning and a shape can be changed by design. Moreover, although the level | step difference of the convex member 4 has cut | disconnected at right angle at 1 step | paragraph, it may cut | disconnect in step shape and may cut in the shape of a slope.

  As described above, in the diffraction element 1 according to the first embodiment, the convex member 4 and the filling member 5 constituting the diffraction grating 2 are surrounded by the transparent substrate 1, the transparent protective plate 6, and the sealing member 8, and the surrounding air Not touching. Therefore, the absorption of moisture in the filling member 5 and the convex member 4 constituting the diffraction grating 2 can be suppressed to a level that does not affect the diffraction characteristics.

(Embodiment 2)
The second embodiment will be described with reference to the drawings. 2A is a front view of the diffraction element according to the second embodiment, and FIG. 2B is a plan view of the AA cross section of FIG. The diffraction element 1 according to the second embodiment is different from the diffraction element 1 according to the first embodiment in providing a sealing member. That is, the diffraction element 1 of the second embodiment is the same as the first embodiment, the transparent substrate 3, the transparent protective plate 6, the convex member 4, the filling member 5, and the organic substance 7. 6, the sealing member 8 is provided in a ring shape on the outer periphery thereof.

  Therefore, the transparent substrate 3, the transparent protective plate 6, the convex member 4, the filling member 5, and the organic substance 7 are the same as those in the first embodiment, and the description thereof is cited. The sealing member 8 may be the same as in the first embodiment, but in the second embodiment, it is more preferable when the viscosity before curing is high.

  Next, a manufacturing method will be described. First, the diffraction grating 2 composed of the convex member 4, the filling member 5, and the organic substance 7 is formed between the transparent substrate 3 and the transparent protective plate 6 in the same manner as in the first embodiment. At that time, the sealing member 8 is not used. Next, it is cut into predetermined dimensions. Finally, the sealing member 8 is passed over the gap between the transparent substrate 3 and the transparent protective plate 6 and applied to the outer periphery of the sealing member 8 in a ring shape and cured to complete.

  When the sealing member 8 is applied, the gap between the transparent substrate 3 and the transparent protective plate 6 must be completely sealed. This is because if there is even a slight gap, moisture may enter the diffraction grating 2 together with the surrounding air from there and the refractive index of at least one of the filling member 5 or the convex member 4 may change. The same applies to the first embodiment. Conversely, the sealing member 8 may enter the gap between the transparent substrate 3 and the transparent protective plate 6.

  As described above, the diffractive element 1 of the second embodiment is similar to the diffractive element 1 of the first embodiment in that the convex member 4 and the filling member 5 constituting the diffraction grating 2 are the transparent substrate 1, the transparent protective plate 6, the sealing member. Surrounded by the stop member 8, the surrounding air is not touched. Therefore, the absorption of moisture in the filling member 5 and the convex member 4 constituting the diffraction grating 2 can be suppressed to a level that does not affect the diffraction characteristics.

(Embodiment 3)
The third embodiment will be described with reference to the drawings. FIG. 3A is a front view of one shape of the diffraction element according to the third embodiment, and FIG. 3B is a plan view of the AA cross section of FIG. FIG. 4A is a front view of another shape of the diffraction element according to the third embodiment, and FIG. 4B is a plan view of the AA cross section of FIG.
The third embodiment is a diffractive element in which the diffraction grating portion on the surface of the transparent substrate 3 is uneven, and has the configuration in which the sealing member 8 described in the first and second embodiments is provided.

  The transparent substrate 3 is the same as the transparent substrate 3 described in the first embodiment, but further has irregularities 9 formed on the surface. 3 and 4, the unevenness 9 is a concave shape, but may be a convex shape or an uneven shape. The unevenness 9 can be produced, for example, by etching the surface of the transparent substrate 3 into a predetermined shape. Moreover, it can also be produced by forming a shape having a predetermined shape and a concavity and convexity in advance on a mold and supplying the raw material of the transparent substrate 3 therefor to transfer it.

  The filling member 5 and the transparent protective plate 6 are the same as those in the first embodiment, and the description thereof is incorporated. In order to ensure the function as the diffraction grating 2, the refractive index of the transparent substrate 3 and the refractive index of the filling member 5 are made different at the wavelength to be used.

  The manufacturing method of the diffraction element 1 having the shape shown in FIG. 3 is as follows. The filling member 5 is applied to the surface of the transparent substrate 3 having the irregularities 9 formed on the surface. In that case, the filling member 5 is apply | coated so that it may fill between the concave shape by the unevenness | corrugation 9, and a concave shape. Further, the amount and position of application are controlled so that the filling member 5 is not applied to unnecessary portions. Similarly, the sealing member 8 is applied by controlling the amount and position. Examples of the application of the filling member 5 and the sealing member 8 include a screen printing method. The transparent protective plate 6 is overlaid thereon, the whole is heated and held, and then cut into a predetermined dimension to complete. The filling member 5 and the sealing member 8 strongly bond the transparent substrate 3 and the transparent protective plate 6.

  As in the first embodiment, when the viscosity of the sealing member 8 before curing is low, the following may be performed. That is, first, only the filling member 5 is applied to the surface of the transparent substrate 3 on which the unevenness 9 is formed, and the transparent protective plate 6 is overlaid thereon, and the whole is heated and held. Next, using the capillary phenomenon from the gap between the transparent substrate 3 and the transparent protective plate 6, the sealing member 8 is injected over the entire circumference under normal pressure or reduced pressure, and the whole is heated and held to be cured. Then, it cuts into a predetermined dimension and is completed.

  The manufacturing method of the diffraction element 1 having the shape shown in FIG. 4 is as follows. The filling member 5 is applied to the surface of the transparent substrate 3 on which the unevenness 9 is formed, and the transparent protective plate 6 is overlaid, and the whole is heated and held. Thereafter, as described in the second embodiment, it is cut into a predetermined size, and the sealing member 8 is applied to the outer periphery of the transparent substrate 3 and the transparent protective plate 6 in an annular shape, Cure to completion.

  The refractive index of the transparent substrate 3 and the refractive index of the filling member 5 are made different so that the diffraction grating 2 functions as a diffraction grating for at least a predetermined single wavelength at the wavelength used. At this time, since the surface of the diffraction grating 2 is flat, interference caused by the optical path length difference is unlikely to occur.

  As in the first embodiment, the filling member 5 may include an organic substance 7 that absorbs light in a predetermined wavelength range, and the wavelength selective diffraction element may be used. At that time, the transparent substrate 3, the filling member 5, the refractive index at the wavelength λ 1 and the wavelength λ 2 of the transparent substrate 3 and the refractive index at the wavelength λ 1 and the wavelength λ 2 of the filling member 5 containing the organic substance 7 are set to predetermined values. Organic matter 7 must be selected.

  Further, when a material as the filling member 5 is selected from the above materials from the optical characteristics, the sealing member 8 may be selected from a material having a water absorption rate equal to or lower than the water absorption rate of the filling member 5. By doing so, it is not necessary to consider the water absorption rate of the filling member 5, so the range of selection of the filling member 5 is expanded.

  As described above, the diffractive element 1 according to the third embodiment is similar to the diffractive element 1 according to the first and second embodiments in that the filling member 5 constituting the diffraction grating 2 together with the transparent substrate 3 is the transparent substrate 1 and the transparent protective plate. 6. Surrounded by the sealing member 8, the surrounding air is not touched. Therefore, moisture absorption of the filling member 5 constituting the diffraction grating 2 can be suppressed to a level that does not affect the diffraction characteristics.

(Embodiment 4)
A fourth embodiment will be described with reference to the drawings. FIG. 5A is a front view of one shape of the diffraction element according to the fourth embodiment, and FIG. 5B is a plan view of the AA cross section of FIG. FIG. 6A is a front view of another shape of the diffraction element according to the fourth embodiment, and FIG. 6B is a plan view of the AA cross section of FIG. The fourth embodiment is a diffractive element having a diffraction grating 2 that does not form irregularities, and is configured to include the sealing member 8 described in the first and second embodiments.

  The transparent substrate 3, the transparent protective plate 6, and the sealing member 8 are the same as those in the first embodiment, and the description thereof is cited. The diffraction grating member 10 is a resin containing an organic substance 7 having light absorption in a predetermined wavelength range. The diffraction grating member 10 is an epoxy thermosetting adhesive such as Epo-Tek 310, 320, or 330, an acrylic ultraviolet curable adhesive such as OG114, a photosensitive polyimide such as PIMEL7640, or a resist such as AZ6130. The organic matter 7 is the same as that described in the first embodiment. However, as will be described later, it is necessary to selectively irradiate ultraviolet rays so as to lose the light absorption property of the region 12 irradiated with the ultraviolet rays. For this reason, it is preferable that a part of the structure that is easily destroyed by ultraviolet rays and that is dissolved in the diffraction grating member 10 at a molecular level is more preferable than that which is dispersed in the diffraction grating member 10 in a particle state. Since the region 12 irradiated with ultraviolet rays loses the light absorption property of the organic matter 7, the refractive index of the region 12 irradiated with ultraviolet rays and the refractive index of the region 11 not irradiated with ultraviolet rays are transmitted through the diffraction grating 2. A difference occurs depending on the wavelength of the laser beam. Therefore, the diffraction element 1 can be a wavelength selective diffraction element.

  Next, a method for manufacturing the diffraction element 1 having the shape shown in FIG. 5 will be described. A diffraction grating member 10 containing an organic substance 7 in advance is applied to the transparent substrate 3. At this time, the amount and position of application are controlled so that the diffraction grating member 10 is not applied to unnecessary portions. Similarly, the sealing member 8 is applied by controlling the amount and position. Examples of the application of the diffraction grating member 10 and the sealing member 8 include a screen printing method. The transparent protective plate 6 is superposed on it and the whole is heated and held. The diffraction grating member 10 and the sealing member 8 strongly bond the transparent substrate 3, the convex member 4, and the transparent protective plate 6. Next, ultraviolet rays are irradiated from the lower surface side of the transparent substrate 3 or the upper surface side of the transparent protective plate 6 through a mask pattern that forms a predetermined pattern. A pattern of the region 11 that is not irradiated with ultraviolet rays and the region 12 that is irradiated with ultraviolet rays is generated. The region 11 that is not irradiated with ultraviolet rays is not affected at all, but the organic matter 7 in the region 12 that is irradiated with ultraviolet rays loses its light-absorbing property because a part of the structure is decomposed. Finally, it is cut to a predetermined dimension and completed.

  As in the first embodiment, when the viscosity of the sealing member 8 before curing is low, the following may be performed. That is, first, the diffraction grating member 10 is applied to the transparent substrate 3, the transparent protective plate 6 is overlaid thereon, and the whole is heated and held. Next, using the capillary phenomenon from the gap between the transparent substrate 3 and the transparent protective plate 6, the sealing member 8 is injected over the entire circumference under normal pressure or reduced pressure, and the whole is heated and held to be cured. Next, ultraviolet rays are irradiated from the lower surface side of the transparent substrate 3 or the upper surface side of the transparent protective plate 6 through a mask pattern that forms a predetermined pattern. A pattern of the region 11 that is not irradiated with ultraviolet rays and the region 12 that is irradiated with ultraviolet rays is generated. Finally, it is cut into predetermined dimensions to complete. In this case, a predetermined pattern may be generated on the diffraction grating member 10 before the sealing member 8 is injected.

  A method for producing the diffraction element 1 having the shape shown in FIG. 6 is as follows. A diffraction grating member 10 containing an organic substance 7 in advance is applied to the transparent substrate 3. At this time, the amount and position of application are controlled so that the diffraction grating member 10 is not applied to unnecessary portions. The transparent protective plate 6 is superposed on it and the whole is heated and held. Next, ultraviolet rays are irradiated through a mask pattern that forms a predetermined pattern. Next, it cut | disconnects to a predetermined dimension, the sealing member 8 is passed over the clearance gap between the transparent substrate 3 and the transparent protective board 6, is apply | coated to the outer peripheral part cyclically | annularly, and it hardens | cures and is completed.

  Since the diffraction element 1 according to the fourth embodiment forms the diffraction grating 2 without forming a concavo-convex shape, a wavelength selective diffraction element can be produced by a simple process.

  Further, when a material as the diffraction grating member 10 is selected from the above materials from the optical characteristics, the sealing member 8 may be selected from a material having a water absorption rate equal to or lower than the water absorption rate of the diffraction grating member 10. By doing so, it becomes unnecessary to consider the water absorption rate of the diffraction grating member 10, so the range of selection of the diffraction grating member 10 is expanded.

  As described above, in the diffraction element 1 of the fourth embodiment, similarly to the diffraction elements 1 of the first and second embodiments, the diffraction grating member 10 constituting the diffraction grating 2 includes the transparent substrate 1, the transparent protective plate 6, and the sealing. Surrounded by the stop member 8, the surrounding air is not touched. Therefore, moisture absorption of the diffraction grating member 10 constituting the diffraction grating 2 can be suppressed to a level that does not affect the diffraction characteristics.

(Embodiment 5)
The fifth embodiment will be described with reference to the drawings. FIG. 7A is a front view of one shape of the diffraction element according to the fifth embodiment, and FIG. 7B is a plan view of the AA cross section of FIG. FIG. 8A is a front view of another shape of the diffraction element according to the fifth embodiment, and FIG. 8B is a plan view of the AA cross section of FIG. In the fourth embodiment, the transparent protective plate 6 was overlaid and heated as a whole when producing the diffraction grating 2 with no irregularities. In the fifth embodiment, the whole was heated without overlapping the transparent protective plate 6. Is the case. The constituent materials are the same as those in the fourth embodiment.

  Next, a method for manufacturing the diffraction element 1 having the shape shown in FIG. 7 will be described. A diffraction grating member 10 containing an organic substance 7 in advance is applied to the transparent substrate 3. Application may be by spin coating or the like. The diffraction grating member 10 is cured by heating and holding. Next, ultraviolet rays are irradiated through a mask pattern that forms a predetermined pattern. The region 11 that is not irradiated with ultraviolet rays is not affected at all, but the organic matter 7 in the region 12 that is irradiated with ultraviolet rays loses its light-absorbing property because a part of the structure is decomposed. Next, unnecessary portions are removed by etching or the like. Alternatively, the diffraction grating member 10 is applied by limiting the application position by screen printing or the like. Next, the sealing member 8 is apply | coated to the whole, the transparent protective plate 6 is piled up, and the whole is heat-held. Finally, it is cut to a predetermined dimension and completed. The sealing member 8 strongly bonds the transparent substrate 3, the diffraction grating member 10, and the transparent protective plate 6. Since the sealing member 8 is also irradiated with light, a material transparent to the light having the wavelength to be used is selected.

  When the sealing member 8 is applied, it may be applied around the diffraction grating member 10 by a screen printing method or the like instead of the whole. The shape in that case is the same as in FIG.

  Further, as shown in FIG. 8, the diffraction grating member 10 may be covered from the upper surface by the sealing member 8 without providing the transparent protective plate 6. In this case, after forming the diffraction grating 2, the sealing member 8 is applied and cured so that the surface of the diffraction grating 2 is flat so as to cover the surface of the diffraction grating 2 by a method such as spin coating. To do. Then, it cuts into a predetermined dimension.

  Thus, when the whole is heated without overlapping the transparent protective plate 6 and the ultraviolet rays are irradiated through the mask pattern, the pattern can be clearly formed because the distance from the mask pattern to the diffraction grating member 10 is small. On the other hand, when the transparent protective plate 6 is overlaid as in Embodiment 4, the pattern is slightly unclear because the distance from the mask pattern to the diffraction grating member 10 is large, but the diffraction grating member 10 is cured and transparent. Since the protection plate 6 can be fixed at the same time, the process is simplified and the manufacturing cost can be reduced.

  Further, when the transparent protective plate 6 is not provided as shown in FIG. 8, the configuration and the manufacturing method are simplified, and the manufacturing cost can be reduced. On the contrary, when the transparent protective plate 6 is provided as in other configurations, the cost is slightly increased, but the function of protecting the diffraction grating 2 can be dramatically improved.

  If a material as the diffraction grating member 10 is selected from the above materials from the optical characteristics, the sealing member 8 may be selected from a material having a water absorption equal to or lower than the water absorption of the diffraction grating member 10. By doing so, it becomes unnecessary to consider the water absorption rate of the diffraction grating member 10, so the range of selection of the diffraction grating member 10 is expanded.

  As described above, in the diffraction element 1 according to the fifth embodiment, the diffraction grating member 10 constituting the diffraction grating 2 is surrounded by the transparent substrate 1, the sealing member 8, and the transparent protective plate 6, and does not touch the surrounding air. Absent. Therefore, moisture absorption of the diffraction grating member 10 constituting the diffraction grating 2 can be suppressed to a level that does not affect the diffraction characteristics.

(Embodiment 6)
A sixth embodiment will be described with reference to the drawings. The sixth embodiment is an optical pickup provided with the wavelength selective diffraction element described in the first to fifth embodiments. FIG. 9 is a configuration diagram of the optical system of the optical pickup according to the sixth embodiment, and FIG. 10 is a configuration diagram of the optical pickup according to the sixth embodiment.

  The laser light source 21 is a two-wavelength semiconductor in which a light emitting point that emits laser light having a wavelength λ1 (about 650 nm) for DVD and a light emitting point that emits laser light having a wavelength λ2 (about 780 nm) for CD are mounted in one package. A laser light source was used. The distance between the two light emitting points is close to about 110 μm. There are two types of two-wavelength semiconductor laser light sources. One is a so-called monolithic type two-wavelength semiconductor laser in which two light emitting points are integrated in one semiconductor laser element, and the other is a so-called hybrid having two semiconductor laser elements having one light emitting point adjacent to each other. This is a type 2 wavelength semiconductor laser. The laser light source 21 in the sixth embodiment may be either type.

  The diffraction element 1 is a wavelength selective diffraction element as described above. The laser beam having the wavelength λ1 passes through the diffraction element 1, and the laser beam having the wavelength λ2 is converted into three beams used for the tracking servo signal. The organic substance 7 has light absorption in a wavelength range slightly shorter than the wavelength λ1. At the wavelength λ 1, the refractive index of the convex member 4 and the refractive index of the filling member 5 or the refractive index of the region 11 not irradiated with ultraviolet rays and the refractive index of the region 12 irradiated with ultraviolet rays are made substantially equal. Then, the refractive index of the convex member 4 and the refractive index of the filling member 5 or the refractive index of the non-irradiated region 11 and the refractive index of the region 12 irradiated with ultraviolet rays are made different at the wavelength λ2. The pattern of the diffraction grating 2 is formed so that two regions are alternately arranged in a stripe pattern. The direction of the parallel arrangement is determined so that the condensed spots of the three light beams are aligned with the tangential direction of the circumference of the optical disk 28 at a predetermined minute angle. The pitch of the diffraction grating 2 is about 5 to 20 μm, and the depth of the diffraction grating 2 is about 1 to 10 μm.

  The integrated optical member 22 is made of optical glass having a plurality of inclined surfaces therein, and a polarization separation film, a hologram, and the like are formed on the inclined surfaces. The collimating lens 23 is a lens that makes laser light substantially parallel light in the forward light, and is made of optical glass or optical plastic. The beam splitter 24 is made of optical glass or the like, and has a polarization separation film formed on the surface thereof. The beam splitter 24 transmits only part of the laser light and reflects most of it. The rising prism 25 raises the optical axis that has been in a plane substantially parallel to the surface of the optical disc 28 until then, substantially perpendicular to the optical disc 28. Although the rising prism is used in the sixth embodiment, it may be a rising mirror. The hologram element 26 includes a polarization hologram 26a and a quarter wavelength plate 26b. The polarization hologram 26a is made of a material having wavelength selectivity so as to act only on light having a wavelength of DVD. The quarter wavelength plate 26b is set to have a refractive index and a thickness so as to act on both wavelengths of DVD and CD. The objective lens 27 is a bifocal objective lens and is configured to focus on the light of wavelength λ1 and the light of wavelength λ2. As the bifocal objective lens, a combination of a condensing lens and a Fresnel lens or a hologram lens, a combination in which a condensing lens for DVD is provided with aperture limiting means during CD reproduction, or the like can be used. The optical disk 28 is a CD, a CD-ROM, a CD-R / RW, a DVD-ROM, a DVD ± R / RW, a DVD-RAM, etc., except for a read-only medium for a CD and a DVD. All can be recorded and played back. In the sixth embodiment, for CD and DVD, not only the combination but also the combination with BD (Blu-ray Disc), HD DVD (High Definition DVD), etc., which are so-called next generation DVDs, is general. I will not lose.

  A light receiving sensor 29 that receives reflected light from the optical disk 28 and generates an electrical signal receives the reflected light from the optical disk 28 and outputs an electrical signal that generates an RF signal, a tracking error signal, a focus error signal, and the like. It is. The light receiving sensor 29 is divided into several light receiving portions. The tracking error signal differs between CD and DVD. This is because the CD uses the three-beam method that uses all three light beams separated by the diffraction element 1, whereas the DVD uses the one-beam method that uses only one central light beam.

  The front light monitor 30 is an optical sensor, converts a part of the laser light from the laser light source 21 into an electrical signal, and feeds back the result to the laser light source 21 through a control circuit (not shown). It works to keep the light quantity of the light source 21 constant.

  The coupling base 31 fixes the diffraction element 1, the integrated optical element 22, the laser light source 21, and the light receiving sensor 29 at predetermined positions and is fixed to the carriage 32. The material forming the coupling base 31 is required to have a relatively lightweight and highly accurate shape workability capable of realizing a finished dimension, good heat dissipation, and the like. Therefore, Zn, Zn alloy, Al, Al alloy, Ti, Ti alloy and the like are preferably used. In the sixth embodiment, it is manufactured by Zn die casting in consideration of cost and the like. The carriage 32 forms a skeleton of the optical pickup 20, and components constituting the optical pickup 20 including various optical components are attached to the carriage 32 directly or via other components. The carriage 32 is made of an alloy material such as Zn alloy or Mg alloy, or a hard resin material.

  The collimating lens 23, the beam splitter 24, the rising prism 25, and the front light monitor 30 are fixed to the carriage 32 directly or via an attachment member.

  The hologram element 26 and the objective lens 27 are fixed to a lens holder 34 having a coil. The lens holder 34 is movably supported by the fixed portion 36 via the suspension wire 35. The fixed part 36 is fixed to a yoke 37 provided with a magnet. At this time, the lens holder 34 should not be touched except for the suspension wire 35. The actuator 33 includes an objective lens 27, a coil, and a magnet. The actuator 33 is fixed to the carriage 32 with an adhesive. The actuator 33 contacts the carriage 32 only via the adhesive. The actuator 33 drives the objective lens 27 so that the focused spot is focused on the track on the recording surface of the optical disk 28 by focus servo and tracking servo.

  Next, the optical path will be described. The laser beam having the wavelength λ 1 for DVD passes through the diffraction element 1 and the integrated optical member 22 and enters the collimating lens 23. In the diffractive element 1, the light of wavelength λ1 is transmitted as it is as described above. The collimator lens 23 is converted into substantially parallel light and enters the beam splitter 24. Some light passes through the beam splitter 24 and enters the front light monitor 30. The light incident on the front light monitor 30 is converted into an electrical signal and used to control the amount of laser light having the wavelength λ1. Most of the remaining light incident on the beam splitter 24 is reflected and enters the rising prism 25. The light incident on the rising prism 25 passes through the hologram element 26 and the objective lens 27 and is focused on the recording surface of the optical disk 28.

  When transmitting through the hologram element 26, the polarization direction of the light is set so that it is transmitted as it is without being influenced by the polarization hologram 26a, and is converted from linearly polarized light (P-polarized light) to circularly polarized light by the quarter wavelength plate 26b. The

  The light reflected by the optical disk 28 passes through the objective lens 27, the hologram element 26, the rising prism 25, the beam splitter 24, and the collimator lens 23 and enters the integrated optical member 22. When transmitting again through the hologram element 26, the quarter wavelength plate 26b converts the circularly polarized light to the forward linearly polarized light which is P-polarized light, which is perpendicular to the linearly polarized light, that is, S-polarized light. The polarization hologram 26a separates the signal light component corresponding to the RF signal, tracking error signal, focus error signal, and the like. The beam splitter 24 totally reflects.

  The polarization separation film provided on the inclined surface 22 a in the integrated optical member 22 transmits the P-polarized laser light emitted from the laser light source 21 and reflects the S-polarized light reflected by the optical disk 28. The configuration is adopted. Therefore, the light incident on the integrated optical member 22 is reflected by the polarization separation film provided on the inclined surface 22 a and enters the light receiving sensor 29. Each signal light component separated by the polarization hologram 26 a and entering the light receiving sensor 29 is converted into various electric signals by the light receiving sensor 29.

  The laser beam having the wavelength λ 2 for CD passes through the diffraction element 1 and the integrated optical member 22 and enters the collimating lens 23. In the diffractive element 1, the light of wavelength λ2 is separated into three light beams as described above. The light is converted into substantially parallel light by the collimator lens 23 and enters the beam splitter 24. Part of the light passes through the beam splitter 24 and enters the front light monitor 30. The light incident on the front light monitor 30 is converted into an electric signal and used for controlling the amount of laser light having a wavelength λ2. Most of the remaining light incident on the beam splitter 24 is reflected and enters the rising prism 25. The light incident on the rising prism 25 passes through the hologram element 26 and the objective lens 27 and is focused on the recording surface of the optical disk 28. When transmitting through the hologram element 26, the wavelength λ2 is not affected by the polarization hologram 26a and is transmitted as it is, and is converted from linearly polarized light (P-polarized light) to circularly polarized light by the quarter-wave plate 26b.

  The light reflected by the optical disk 28 passes through the objective lens 27, the hologram element 26, the rising prism 25, the beam splitter 24, and the collimator lens 23 and enters the integrated optical member 22. When transmitting again through the hologram element 26, the quarter wavelength plate 26b converts the circularly polarized light to the forward linearly polarized light which is P-polarized light, which is perpendicular to the linearly polarized light, that is, S-polarized light. Since the wavelength λ2 is not affected by the polarization hologram 26a, it passes through the polarization hologram 26a as it is. The beam splitter 24 totally reflects.

  The polarization separation film provided on the inclined surface 22b in the integrated optical member 22 transmits the light emitted from the laser light source 21, reflects the laser light having the wavelength λ2 reflected by the optical disk 28, and laser light having the wavelength λ1. A film configuration that transmits the light is adopted. Therefore, the light incident on the integrated optical member 22 is reflected by the polarization separation film provided on the inclined surface 22b, is incident on the hologram provided on the inclined surface 22c, and corresponds to an RF signal, a tracking error signal, a focus error signal, and the like. Separated into signal light components. The separated light enters the light receiving sensor 29 and is converted into various electric signals.

  In the sixth embodiment, the diffractive element 1 has wavelength selectivity, allows laser light of wavelength λ1 for DVD to pass through, and separates only laser light of wavelength λ2 for CD into three light beams used for tracking servo. To do. Moreover, since the material constituting the diffraction grating 2 having a water absorption rate exceeding 5% is not exposed to air, the diffraction element 1 has stable diffraction characteristics. Therefore, the optical pickup 20 equipped with the diffraction element 1 has a stable tracking servo and stable recording and reproduction characteristics.

(Embodiment 7)
The seventh embodiment will be described with reference to the drawings. The seventh embodiment is an optical pickup provided with the single-wavelength diffraction element described in the third embodiment. FIG. 11 is a configuration diagram of an optical system of the optical pickup according to the seventh embodiment. The laser light source 21a emits laser light having a wavelength λ1 (about 650 nm) for DVD. The laser light source 21b emits laser light having a wavelength λ2 (about 780 nm) for CD.

  Since the diffractive element 1 allows only the laser beam having the wavelength λ2 to pass therethrough, it is not necessary to include the organic substance 7 and to have a wavelength selective function. Therefore, the diffraction element 1 according to the seventh embodiment can have optimum diffraction characteristics with respect to the laser light having the wavelength λ2. Since the material constituting the diffraction grating 2 having a water absorption rate exceeding 5% is not exposed to air, the diffraction element 1 has stable diffraction characteristics. The laser light having the wavelength λ2 is separated into three light beams used for the tracking servo signal. The pattern of the diffraction grating 2 is formed so that the two regions of the transparent substrate 3 and the filling member 5 are alternately arranged in a stripe pattern. The direction of the parallel arrangement is determined so that the condensed spots of the three light beams are aligned with the tangential direction of the circumference of the optical disk 28 at a predetermined minute angle. The pitch of the diffraction grating 2 is about 5 to 20 μm, and the depth of the diffraction grating 2 is about 1 to 10 μm.

  The integrated optical member 22 has the same function and configuration as the integrated optical member 22 of Embodiment 6 except that the function for the laser beam having the wavelength λ1 emitted from the laser light source 21a is unnecessary, and the description thereof is incorporated. The reflecting mirror 38 converts the traveling direction of the laser light having the wavelength λ1 into the direction of the optical disk 28. The reflecting mirror 38 has a total reflection film on the surface. The collimating lens 23a converts the divergent laser light emitted from the laser light source 21a into substantially parallel light. The collimating lens 23b converts the diverging laser beam emitted from the laser light source 21b into substantially parallel light. The collimating lenses 23a and 23b are made of optical glass or optical plastic.

  The beam splitter 24 has an inclined surface with a wavelength selective polarization separation film inside. The wavelength selective polarization separation film transmits most of the laser light having the wavelength λ1 emitted from the laser light source 21a and reflects a part thereof. Further, most of the laser light having the wavelength λ2 emitted from the laser light source 21b is reflected and partially transmitted. Further, the laser light having the wavelengths λ1 and λ2 reflected by the recording surface of the optical disk 28 is substantially totally reflected.

  The rising prism 25, the hologram element 26, the objective lens 27, the optical disk 28, the light receiving sensor 29, and the front light monitor 30 are the same as those in the sixth embodiment, and the description thereof is cited. The coupling base 31 uses a laser light source 21b instead of the laser light source 21 mounted on the coupling base 31 of the sixth embodiment. In addition to the carriage 32 of the sixth embodiment, the carriage 32 of the seventh embodiment also fixes the laser light source 21a, the reflecting mirror 38, and the collimating lens 23a directly or via an attachment member. The actuator 33 is the same as that of the sixth embodiment, and the description thereof is cited.

  Regarding the optical path, the laser light having the wavelength λ2 is the same as that of the sixth embodiment, and the description thereof is cited. The laser light having the wavelength λ1 emitted from the laser light source 21a is reflected by the reflecting mirror 38 and enters the collimating lens 23a. The light is converted into substantially parallel light by the collimator lens 23 a and enters the beam splitter 24. The laser light reflected by the beam splitter 24 enters the front light monitor 30 and is used for controlling the output of the laser light source 21a. Most of the laser light transmitted through the beam splitter 24 enters the rising prism 25. Since the optical path of the laser beam having the wavelength λ1 is the same as that in the sixth embodiment, the description thereof is cited.

  As described above, since the optical pickup 20 of the seventh embodiment has stable diffraction characteristics of the diffraction element 1, the tracking servo is stable. As a result, recording and playback characteristics are stabilized.

(Embodiment 8)
An eighth embodiment will be described with reference to the drawings. The eighth embodiment is an optical disk device provided with the optical pickup of the sixth or seventh embodiment. FIG. 12 is a block diagram of an optical pickup module according to the eighth embodiment, and FIG. 13 is a block diagram of an optical disk device according to the eighth embodiment.

  Of the optical disk device 50, a drive mechanism that drives the optical disk 28 and the optical pickup 20 is referred to as an optical pickup module 40. The base 41 forms a framework of the optical pickup module 40, and each component is fixed directly or indirectly to the base 41.

  A spindle motor 42 having a turntable on which the optical disk 28 is placed is fixed to the base 41. The spindle motor 42 generates a rotational driving force that rotates the optical disk 28.

  The feed motor 43 is fixed to the base 41. The feed motor 43 generates a rotational driving force necessary for the optical pickup 20 to move between the inner periphery and the outer periphery of the optical disk 28. A stepping motor, a DC motor, or the like is used as the feed motor 43. The screw shaft 44 has a groove formed in a spiral shape, and is connected to the feed motor 43 directly or through several stages of gears. In the eighth embodiment, it is directly connected to the feed motor 43. The guide shafts 45 and 46 are fixed to the base 41 via support members at both ends. The guide shafts 45 and 46 support the optical pickup 20 so as to be movable. The optical pickup 20 includes a rack having guide teeth that mesh with the grooves of the screw shaft 44. The optical pickup 20 can move between the inner periphery and the outer periphery of the optical disk 28 so that the rack converts the rotational driving force of the feed motor 43 transmitted to the screw shaft 44 into a linear driving force.

  The optical pickup 20 has been described in the sixth embodiment or the seventh embodiment. The optical pickup 20 performs at least one of recording and reproduction of information with respect to the optical disk 28 and emits laser light toward the optical disk 28 for that purpose. The inclination of the guide shafts 45 and 46 is adjusted by an adjusting mechanism that constitutes a support member so that the laser light emitted from the optical pickup 20 is incident on the optical disk 28 at a right angle.

  The upper casing 51a and the lower casing 51b are combined and fixed to each other using screws or the like to form the casing 51. The tray 52 is provided in the casing 51 so as to be able to appear and disappear. In the tray 52, the optical pickup module 40 to which the cover 53 is attached is arranged from the lower surface side. The cover 53 has an opening to expose a part including the objective lens 27 of the optical pickup 20 and the turntable of the spindle motor 42. In the case of the eighth embodiment, the feed motor 43 is also exposed. A bezel 54 is provided on the front end surface of the tray 52 so that when the tray 52 is stored in the housing 51, the entrance and exit of the tray 52 is closed.

  The bezel 54 is provided with an eject switch 55. When the eject switch 55 is pressed, the engagement between the housing 51 and the tray 52 is released, and the tray 52 can be brought into and out of the housing 51. The rails 56 are slidably attached to both sides of the tray 52 and the casing 51, respectively.

  There is a circuit board (not shown) inside the casing 51 and inside the tray 52, and a signal processing system IC, a power supply circuit, and the like are mounted. An external connector 57 (not shown) is connected to a power / signal line provided in an electronic device such as a computer. Then, power is supplied into the optical disc device 50 via the external connector 57, an electric signal from the outside is guided into the optical disc device 50, or an electric signal generated by the optical disc device 50 is supplied to an external electronic device or the like. Or send it out.

  As described above, the optical disc apparatus 50 according to the eighth embodiment includes the optical pickup 20 described in the sixth embodiment or the seventh embodiment. In the optical pickup 20 of the sixth embodiment or the seventh embodiment, the tracking servo is stable, and therefore the recording and reproduction characteristics are stable. Therefore, the optical disc apparatus 50 according to the eighth embodiment can perform stable recording and reproduction with stable tracking servo.

  As described above, the diffraction element of the present invention can suppress the absorption of moisture to a level that does not affect the diffraction characteristics of the material constituting the diffraction grating 2 so as to absorb moisture in the air. The diffraction characteristics are stable even when exposed to. Therefore, the diffractive element of the present invention is useful for an optical pickup and an optical disc apparatus equipped with the optical pickup.

(A) Front view of diffraction element of Embodiment 1, (b) Plan view of AA cross section of (a) (A) Front view of diffraction element of Embodiment 2, (b) Plan view of AA cross section of (a) (A) Front view of one shape of diffraction element of Embodiment 3, (b) Plan view of AA cross section of (a) (A) The front view of the other shape of the diffraction element of this Embodiment 3, (b) The top view of the AA cross section of (a). (A) Front view of one shape of diffraction element of Embodiment 4, (b) Plan view of AA cross section of (a) (A) The front view of the other shape of the diffraction element of this Embodiment 4, (b) The top view of the AA cross section of (a). (A) Front view of one shape of diffraction element of Embodiment 5, (b) Plan view of AA cross section of (a) (A) The front view of the other shape of the diffraction element of this Embodiment 5, (b) The top view of the AA cross section of (a). Configuration diagram of optical system of optical pickup of Embodiment 6 Configuration diagram of optical pickup of Embodiment 6 Configuration diagram of optical system of optical pickup of Embodiment 7 Configuration diagram of optical pickup module according to Embodiment 8 Configuration diagram of optical disk apparatus according to Embodiment 8 (A) Front view of a diffraction element of a conventional example in which the surface of the diffraction grating is flattened, (b) Plan view of the AA section of (a)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diffraction element 2 Diffraction grating 3 Transparent substrate 4 Convex member 5 Filling member 6 Transparent protective plate 7 Organic substance 8 Sealing member 9 Concavity and convexity 10 Diffraction grating member 11 Area | region where ultraviolet rays were not irradiated 12 Area | region irradiated with ultraviolet rays 20 Optical pick-up 21 Laser Light source 22 Integrated optical member 23 Collimator lens 24 Beam splitter 25 Rising prism 26 Hologram element 26a Polarization hologram 26b 1/4 wavelength plate 27 Objective lens 28 Optical disk 29 Light receiving sensor 30 Front light monitor 31 Coupling base 32 Carriage 33 Actuator 34 Lens holder 35 Suspension wire 36 Fixed portion 37 Yoke 38 Reflector 40 Optical pickup module 41 Base 42 Spindle motor 43 Feed motor 44 Screw shaft 45, 46 Guide shaft 51 Housing Body 51a Upper housing 51b Lower housing 52 Tray 53 Cover 54 Bezel 55 Eject button 56 Rail 57 External connector

Claims (13)

In a diffraction element comprising a transparent substrate and a diffraction grating formed on the surface of the transparent substrate, the transparent substrate on which a predetermined transparent convex member constituting the diffraction grating is disposed, and a transparent protective plate The transparent substrate and the transparent protective plate are connected between the transparent substrate and the transparent protective plate, and the transparent filling member that is filled between the transparent protective plate and the concave and convex portions formed of the transparent substrate and the convex member. And a sealing member that annularly surrounds the outside of the filling member. The diffraction element according to claim 1, wherein a water absorption rate of the sealing member is equal to or less than a water absorption rate of the filling member. 2. The diffraction element according to claim 1, wherein an organic substance having light absorption in a predetermined wavelength region is included in one of the convex member and the filling member. In a diffraction element comprising a transparent substrate and a diffraction grating formed on the surface of the transparent substrate, a transparent diffraction grating member having two refractive indexes constituting the diffraction grating, and a surface side of the diffraction grating member A diffraction element, comprising: a transparent protective plate disposed; and a sealing member that connects the transparent substrate and the transparent protective plate and surrounds the diffraction grating member in an annular shape. The diffraction element according to claim 4, wherein a water absorption rate of the sealing member is equal to or less than a water absorption rate of the diffraction grating member. The diffraction according to claim 4, wherein the diffraction grating member includes an organic substance having light absorption in a predetermined wavelength region, and the organic substance in one of the refractive index regions has lost at least part of the light absorption. element. In a diffraction element comprising a transparent substrate and a diffraction grating formed on the surface of the transparent substrate, a transparent diffraction grating member having two refractive indexes constituting the diffraction grating, and a transparent covering the diffraction grating member A diffraction element comprising: a sealing member. The diffraction element according to claim 7, wherein a water absorption rate of the sealing member is equal to or less than a water absorption rate of the diffraction grating member. 8. The diffraction according to claim 7, wherein the diffraction grating member includes an organic substance having light absorption in a predetermined wavelength range, and the organic substance in one of the refractive index regions has lost at least part of the light absorption. element. In a diffraction element comprising a transparent substrate and a diffraction grating formed on the surface of the transparent substrate, the transparent substrate on the surface of which predetermined unevenness constituting the diffraction grating is formed, a transparent protective plate, and the transparent A transparent filling member that is filled between the unevenness of the substrate and the transparent protective plate to constitute the diffraction grating, and a seal that surrounds the outside of the filling member in an annular shape by connecting the transparent substrate and the transparent protective plate And a diffraction element. The diffraction element according to claim 10, wherein a water absorption rate of the sealing member is equal to or less than a water absorption rate of the filling member. An optical pickup comprising the diffraction element according to any one of claims 1, 4, 7, and 10. An optical disc apparatus comprising the optical pickup according to claim 12.

Images