JP2010054658A - Diffraction element, optical pickup apparatus and optical disc apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diffraction element capable of being manufactured in a short time, an optical pickup apparatus and an optical disc apparatus. <P>SOLUTION: The diffraction element 10 receives light which has wavelengths λ 1, λ 2 from a light source 20, comprises a first member 13 and a second member 14 which are arrayed alternately in the light entrance surface thereof to constitute a diffraction grating 11 and allows the light having the wavelength λ1 transmitted therethrough and the light having wavelength λ2 separated form and emitted to an optical disc 21. The first member 13 comprises a first resin 15 and exhibits a prescribed refractive index to the light having wavelengths λ1, λ2. The second member 14 comprises a second resin 16 in which a dyestuff 17 is dissolved on the molecular level, absorbs light having a prescribed wavelength range Δλa, and the second member 14 has the same refractive index as that of the first member 13 to the light having the wavelength λ1 and the refractive index different from that of the first member to the light having the wavelength λ2. The maximum absorption wavelength λamax of the light absorbed by the second member 14 is set on outside the wavelengths λ1 and λ2 and the wavelength λa+ at one edge of the wavelength range Δλa is set between the wavelengths λ1 and λ2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a diffraction element, an optical pickup device, and an optical disk device mounted on an electronic device such as a personal computer or a notebook computer.

  Conventionally, in order to reduce the cost, an optical pickup device has used a light source that emits light of two wavelengths toward an optical disk. In order to cope with this, a diffraction grating has been used in which light of two wavelengths is incident from a light source, light of one wavelength is transmitted, and light of the other wavelength is separated.

  FIG. 12 is a sectional view of a conventional diffraction element. The diffraction element 200 includes a diffraction grating 201 formed on a substrate 202. The diffraction element 200 receives light of two wavelengths λ1 and λ2 from a light source 210. The diffractive element 200 includes a first member 203 and a second member 204 that are alternately arranged in a light incident surface and constitute a diffraction grating 201. The diffractive element 200 transmits light having one wavelength λ1 and separates light having the other wavelength λ2 and outputs the separated light to the optical disc 220.

  The first member 203 includes a first resin 205. The second member 204 includes a second resin 206 in which a dye 207 is dissolved at a molecular level. The surface of the diffraction grating 201 is protected from the external environment by bonding the substrate 208 with an adhesive 209.

  FIG. 13 is an explanatory diagram of the anomalous dispersion effect, and FIG. 14 is a diagram showing the relationship between the wavelength and refractive index of the conventional first member and second member. In FIG. 13, generally, a material in which a dye is dissolved at a molecular level has light absorption in a certain wavelength region, and the light absorption rate is larger than that in the case where the dye is not dissolved in that wavelength region. Further, the closer to the wavelength range having light absorption, the higher the refractive index of the material in which the dye is dissolved than in the case where the dye is not dissolved. This phenomenon is called an anomalous dispersion effect.

  Utilizing this anomalous dispersion effect, the wavelength dependency of the refractive index of the second member 204 in which the dye 207 is dissolved is made larger than the wavelength dependency of the refractive index of the first member 203. Therefore, in FIG. 14, the second member 204 can have the same refractive index as that of the first member 203 at one wavelength λ1 and a different refractive index from that of the first member 203 at the other wavelength λ2. Here, the light absorption at the wavelengths λ1 and λ2 is suppressed as much as possible by setting the wavelength region having light absorption to be outside the wavelengths λ1 and λ2.

  In FIG. 12, the refractive index of the 1st member 203 and the 2nd member 204 which comprise the diffraction grating 201 with wavelength (lambda) 1 is equal. Therefore, the light of wavelength λ1 incident on the diffraction grating 201 is transmitted as it is. The refractive index of the first member 203 and the second member 204 is different at the wavelength λ2. Therefore, the light of wavelength λ2 incident on the diffraction grating 201 is diffracted and separated.

(Patent Document 1) and (Patent Document 2) show the configuration of the diffraction element 200.
JP 2002-318306 A JP 2006-244665A

  However, it takes a long time to completely dissolve the dye in the second resin at the molecular level. The time required for dissolution is longer as the concentration of the dye is higher. Moreover, it takes a long time for the second resin to cure because the dye hinders curing. The time required for curing is longer as the concentration of the dye is higher. However, when the dye is dissolved in a short time and the concentration of the dye is decreased in order to cure the second resin, a predetermined refractive index cannot be obtained.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and to provide a diffraction element, an optical pickup device, and an optical disk device that require a short production time.

  In order to achieve the above object, the present invention includes a first member and a second member that receive light of two wavelengths from a light source and are alternately arranged in the light incident surface to form a diffraction grating. A diffractive element that transmits light having a wavelength of 1 and separates and emits light having the other wavelength to an optical disc, wherein the first member includes a first resin and has a predetermined refractive index at the two wavelengths. The two members include a second resin in which a dye is dissolved at a molecular level, have light absorption in a predetermined wavelength region, have the same refractive index as that of the first member at the one wavelength, and the wavelength at the other wavelength. The first member has a refractive index different from that of the first member, the maximum absorption wavelength in the light absorption of the second member is outside the two wavelengths, and one absorption edge wavelength is between the two wavelengths. And a diffraction element.

  The difference between the refractive index of the material in which the dye is dissolved and the refractive index of the material in which the dye is not dissolved is larger as the wavelength is closer to the maximum absorption wavelength, and the smaller the concentration of the dye is, the smaller. By using a dye having an absorption edge wavelength between two wavelengths, the maximum absorption wavelength approaches two wavelengths. Therefore, this difference in refractive index becomes large. On the other hand, the difference in refractive index can be reduced by reducing the concentration of the dye. Therefore, by using a dye having an absorption edge wavelength between two wavelengths, the concentration of the dye can be reduced without changing the difference in refractive index between the two wavelengths. Therefore, the time required to dissolve the dye in the second resin and the time required to cure the second resin can be shortened.

  The diffractive element of the present invention can shorten the time required for dissolving the dye in the second resin and the time required for curing the second resin, so that the time required for production can be shortened. it can.

  The invention according to claim 1 of the present invention includes a first member and a second member, which enter a light of two wavelengths from a light source and are alternately arranged in a light incident surface to constitute a diffraction grating, and have one wavelength. Is a diffractive element that transmits light of the other wavelength and separates light of the other wavelength and emits it to an optical disk. The first member has a first resin and has a predetermined refractive index at two wavelengths, and the second member has a dye. The second resin dissolved at the molecular level has light absorption in a predetermined wavelength range, has the same refractive index as the first member at one wavelength, and has a different refractive index from the first member at the other wavelength. The diffractive element has a maximum absorption wavelength in light absorption of the second member outside the two wavelengths and one absorption edge wavelength between the two wavelengths.

  The difference between the refractive index of the material in which the dye is dissolved and the refractive index of the material in which the dye is not dissolved is larger as the wavelength is closer to the maximum absorption wavelength, and the smaller the concentration of the dye is, the smaller. By using a dye having an absorption edge wavelength between two wavelengths, the maximum absorption wavelength approaches two wavelengths. Therefore, this difference in refractive index becomes large. On the other hand, the difference in refractive index can be reduced by reducing the concentration of the dye. Therefore, by using a dye having an absorption edge wavelength between two wavelengths, the concentration of the dye can be reduced without changing the difference in refractive index between the two wavelengths. Therefore, the time required to dissolve the dye in the second resin and the time required to cure the second resin can be shortened. Therefore, the time required for production can be shortened.

  The invention of claim 2 is the diffraction element according to claim 1, wherein one of the absorption edge wavelengths is in the vicinity of the wavelength between the maximum absorption wavelength and one of the two absorption edge wavelengths. is there.

  At the absorption edge wavelength, there is no light absorption. Therefore, the light absorption is small even at the wavelength between the maximum absorption wavelength, which is the greater of the two wavelengths, and the one absorption edge wavelength, and the amount of light absorbed by the diffraction grating is small. The emitted light quantity is efficiently emitted to the optical disc.

  According to a third aspect of the present invention, in the first aspect of the invention, the light absorption rate of the second member at the wavelength between the maximum absorption wavelength and one of the two absorption wavelengths of the two wavelengths is that of the second resin. The diffraction element is slightly larger than the light absorption rate.

  Of the two wavelengths, the light absorption by the dye is small even at the wavelength between the maximum absorption wavelength and the one of the absorption edge wavelengths, which is the greater absorption of light, and the amount of light absorbed by the diffraction grating is small. The emitted light quantity is efficiently emitted to the optical disc.

  According to a fourth aspect of the present invention, there is provided a light source that emits light of two wavelengths toward the optical disc, and light of two wavelengths incident from the light source, and is arranged alternately on the light incident surface to constitute a diffraction grating. A diffraction element that includes one member and a second member, transmits light of one wavelength and separates light of the other wavelength and emits the light to an optical disc, and the first member includes a first resin at two wavelengths. Having a predetermined refractive index, the second member includes a second resin in which a dye is dissolved at a molecular level, has light absorption in a predetermined wavelength region, has the same refractive index as that of the first member at one wavelength, and An optical pickup device having a refractive index different from that of the first member at the other wavelength, and the predetermined wavelength of the two wavelengths is between the wavelength at which light absorption is maximum and the wavelength at the end of the predetermined wavelength range. is there.

  The difference between the refractive index of the material in which the dye is dissolved and the refractive index of the material in which the dye is not dissolved is larger as the wavelength is closer to the maximum absorption wavelength, and the smaller the concentration of the dye is, the smaller. By using a dye having an absorption edge wavelength between two wavelengths, the maximum absorption wavelength approaches two wavelengths. Therefore, this difference in refractive index becomes large. On the other hand, the difference in refractive index can be reduced by reducing the concentration of the dye. Therefore, by using a dye having an absorption edge wavelength between two wavelengths, the concentration of the dye can be reduced without changing the difference in refractive index between the two wavelengths. Therefore, the time required to dissolve the dye in the second resin and the time required to cure the second resin can be shortened. Therefore, the time required for production can be shortened.

  According to a fifth aspect of the present invention, there is provided a light source that emits light of two wavelengths toward the optical disc, and light of two wavelengths incident from the light source, and is arranged alternately on the light incident surface to constitute a diffraction grating. A diffraction element that includes one member and a second member, transmits light of one wavelength and separates light of the other wavelength and emits the light to an optical disc, and the first member includes a first resin at two wavelengths. Having a predetermined refractive index, the second member includes a second resin in which a dye is dissolved at a molecular level, has light absorption in a predetermined wavelength region, has the same refractive index as that of the first member at one wavelength, and The optical disk apparatus has a refractive index different from that of the first member at the other wavelength, and the predetermined wavelength of the two wavelengths is between the wavelength at which light absorption is maximum and the wavelength at the end of the predetermined wavelength range. .

  The difference between the refractive index of the material in which the dye is dissolved and the refractive index of the material in which the dye is not dissolved is larger as the wavelength is closer to the maximum absorption wavelength, and the smaller the concentration of the dye is, the smaller. By using a dye having an absorption edge wavelength between two wavelengths, the maximum absorption wavelength approaches two wavelengths. Therefore, this difference in refractive index becomes large. On the other hand, the difference in refractive index can be reduced by reducing the concentration of the dye. Therefore, by using a dye having an absorption edge wavelength between two wavelengths, the concentration of the dye can be reduced without changing the difference in refractive index between the two wavelengths. Therefore, the time required to dissolve the dye in the second resin and the time required to cure the second resin can be shortened. Therefore, the time required for production can be shortened.

(Embodiment 1)
The first embodiment will be described with reference to the drawings. First, an outline of the diffraction element of the first embodiment will be described. FIG. 1A is a cross-sectional view of the diffraction element according to the first embodiment, and FIG. 1B is a diagram showing the wavelength characteristics of the light absorptance and refractive index. The diffractive element 10 according to the first embodiment receives light of two wavelengths λ1 and λ2 from a light source 20 and is arranged alternately on the light incident surface to form the diffraction grating 11 and the second member 13. And a member 14. The diffractive element 10 transmits light having one wavelength λ1 and separates light having the other wavelength λ2 and outputs the separated light to the optical disc 21. The first member 13 includes a first resin 15 and has a predetermined refractive index at two wavelengths λ1 and λ2. The second member 14 includes a second resin 16 in which a dye 17 is dissolved at a molecular level and includes a predetermined wavelength range. Δλa has light absorption. The second member 14 has the same refractive index as that of the first member 13 at one wavelength λ1 and a different refractive index from that of the first member 13 at the other wavelength λ2. In the diffraction element 10 of the first embodiment, the maximum absorption wavelength λamax in light absorption of the second member 14 is outside the two wavelengths λ1 and λ2, and one absorption edge wavelength λa + is between the two wavelengths λ1 and λ2. It is characterized by that.

  The difference between the refractive index of the material in which the dye 17 is dissolved and the refractive index of the material in which the dye 17 is not dissolved is larger as the wavelength is closer to the maximum absorption wavelength, and the smaller the concentration of the dye 17 is, the smaller. By using the dye 17 having the absorption edge wavelength λa + between the two wavelengths λ1 and λ2, the maximum absorption wavelength λamax approaches the two wavelengths λ1 and λ2. Therefore, this difference in refractive index becomes large. On the other hand, the difference in refractive index can be reduced by reducing the concentration of the dye 17. Therefore, by using the dye 17 having the absorption edge wavelength λa + between the two wavelengths λ1 and λ2, the concentration of the dye 17 can be reduced without changing the difference in refractive index between the two wavelengths λ1 and λ2. . Therefore, the time required to dissolve the dye 17 in the second resin 16 and the time required to cure the second resin 16 can be shortened. Therefore, the time required for production can be shortened.

  The diffraction element 10 of the first embodiment will be described in further detail.

  In FIG. 1, a light source 20 emits light having a short wavelength λ1 and light having a long wavelength λ2 from close positions. The light of wavelength λ1 and the light of wavelength λ2 are laser beams. In the first embodiment, the light of wavelength λ1 is λ1 = about 650 nm for DVD, and the light of wavelength λ2 is λ2 = about 780 nm for CD. In the first embodiment, the light emitted from the light source 20 is for DVD and CD, but for example, a combination with light of other wavelengths such as light having a wavelength of about 405 nm for BD (Blu-ray Disc). It doesn't matter. The transparent substrates 12 and 18 are transparent substrates at the wavelengths λ1 and λ2, and are made of, for example, optical glass such as BK7. As the adhesive 19, a normal adhesive such as a thermosetting adhesive, an ultraviolet curable adhesive, an epoxy adhesive, or an anaerobic adhesive is used. The diffraction element 10 has a configuration in which a transparent substrate 12 on which a diffraction grating 11 is formed and a transparent substrate 18 are bonded with an adhesive 19 sandwiching the diffraction grating 11. The optical disk 21 is a CD, DVD, BD or the like as described above.

  The diffraction grating 11 is configured so that the first member 13 is formed in a predetermined concavo-convex shape and the second member 14 is filled with the concavo-convex shape within the incident surface of the light from the light source 20. In the diffraction grating 11, the refractive index of the first member 13 and the refractive index of the second member 14 are equal at the wavelength λ1, and the refractive index of the first member 13 and the refractive index of the second member 14 are different at the wavelength λ2. Configured. Therefore, no diffraction occurs between the first member 13 and the second member 14 at the wavelength λ1, and the light of the wavelength λ1 is transmitted as it is. At the wavelength λ2, diffraction occurs by the difference in refractive index between the first member 13 and the second member 14, and the light of the wavelength λ2 is separated into 0th order light, ± first order light,. Concave and convex depth and spacing of the concave and convex shapes according to the difference in refractive index between the first member 13 and the second member 14 at the wavelength λ2 so that the separated light is directed in a predetermined direction with a predetermined spectral ratio. The direction of the concavo-convex incident surface is determined. That is, the diffraction element 10 includes a diffraction grating 11 for CD.

  In order to realize the refractive index of the first member 13 and the refractive index of the second member 14, the first member 13 includes a first resin 15, and the second member 14 is a second material in which a dye 17 is dissolved at a molecular level. Resin 16 was provided. The first resin 15 and the second resin 16 are usually selected from materials that do not have a large wavelength dependency of the refractive index. The first resin 15 and the second resin 16 are transparent at the wavelength λ1 and the wavelength λ2. As the first resin 15 and the second resin 16, a thermosetting resin, an ultraviolet curable resin, an epoxy resin, or the like is used. For example, Epo-tek 310, 320, 330 and the like are used, and these resins are thermosetting resins.

  The second member 14 including the second resin 16 in which the dye 17 is dissolved at the molecular level has light absorption in a predetermined wavelength range Δλa. The longest wavelength of the wavelength region Δλa having light absorption is the absorption edge wavelength λa +, and the shortest wavelength is the absorption edge wavelength λa−. Further, the maximum absorption wavelength λamax at which light absorption is maximized is near the center of the wavelength region Δλa.

  The refractive index of the second member 14 is larger than the refractive index of the second resin 16 alone due to the anomalous dispersion effect due to the dye 17, and the difference in refractive index between the second member 14 and the second resin 16 alone is close to the maximum absorption wavelength λamax. It is so big. That is, the second member 14 has a wavelength dependency of the refractive index greater than that of the second resin 16 alone. Therefore, by combining the first resin 15, the second resin 16, and the dye 17, the refractive index of the first member 13 and the refractive index of the second member 14 are equal at the wavelength λ1, and the first member 13 at the wavelength λ2. The refractive index of the second member 14 may be different from the refractive index of the second member 14.

  In the first embodiment, the maximum absorption wavelength λamax in the light absorption of the second member 14 is shorter than the wavelength λ1, and the absorption edge wavelength λa + is between the wavelengths λ1 and λ2. That is, the wavelength λ1 which is one of the used wavelengths is in the wavelength range Δλa where the second member 14 absorbs light.

  FIG. 2A is a diagram showing a comparison of refractive indexes when the absorption edge wavelength is between the wavelengths λ1 and λ2, and FIG. 2B is a relationship between the light absorption rate and the refractive index depending on the dye concentration. FIG.

  In FIG. 2A, when the absorption edge wavelength λa + of the second member 14 indicated by the broken line is not between the wavelength λ1 and the wavelength λ2, the wavelength λ1 is far from the maximum absorption wavelength λamax. The difference in refractive index between the two members 14 and the second resin 16 alone indicated by a dotted line is small. On the other hand, when the absorption edge wavelength λa + of the second member 14 indicated by the solid line is between the wavelengths λ1 and λ2, the wavelength λ1 is close to the maximum absorption wavelength λamax, and therefore the second member 14 indicated by the solid line at the wavelength λ1 and the dotted line The difference in refractive index between the second resin 16 and the second resin 16 is large. Therefore, the refractive index of the second member 14 at the wavelength λ1 is larger when the absorption edge wavelength λa + of the second member 14 is between the wavelengths λ1 and λ2.

  Next, in FIG. 2B, when the same dye 17 is used, the light absorptance and the refractive index at the same wavelength are larger in the case where the concentration indicated by the broken line is higher than in the case where the concentration of the dye 17 indicated by the solid line is low. Accordingly, the refractive index n1 at the wavelength λ1 when the absorption edge wavelength λa + of the second member 14 is not between the wavelengths λ1 and λ2, and the absorption edge wavelength λa + of the second member 14 is between the wavelength λ1 and the wavelength λ2. In this case, it can be realized by reducing the concentration of the dye 17.

  The time required to dissolve the dye 17 in the second resin 16 when the second member 16 is dissolved at the molecular level by curing the second resin 16 as a result of configuring the second member 14 with a lower concentration of the dye 17. And the time required to cure the second resin 16 can be shortened. Therefore, the time required for production can be shortened. In addition, when the second resin 16 is cured by dissolving the dye 17 at the molecular level, there is an effect that the amount of the disturbing dye 17 is small and the curing reaction of the second resin 16 is easily completed. In that case, no uncured and physically unstable portion remains in the second resin 16, so that the diffraction grating 11 does not easily change its volume even if the laser beam is irradiated for a long period of time and repeated use. As a result, the diffractive element 10 has stable characteristics over a long period of time.

  Here, it is desirable that the absorption edge wavelength λa + be in the vicinity of the wavelength λ1 that is the wavelength between the maximum absorption wavelength λamax and the absorption edge wavelength λa + of the two wavelengths λ1 and λ2. That is, since the light absorption is lost at the absorption edge wavelength λa +, the light absorption is small even at the wavelength λ1 if the absorption edge wavelength λa + is near the wavelength λ1. Therefore, since the amount of light absorbed by the diffraction grating 11 is small, the amount of light emitted from the light source 20 is efficiently emitted to the optical disc 21. In the first embodiment, since the concentration of the dye 17 is low, the light absorptance at the wavelength λ1 can be further reduced.

  Further, the light absorption rate of the second member 14 at the wavelength λ1 which is the wavelength between the maximum absorption wavelength λamax and the one absorption edge wavelength λa + of the two wavelengths λ1 and λ2 is the light of the second resin 16. It is desirable to make it slightly larger than the absorption rate. That is, light absorption by the dye 17 is small even at the wavelength λ1. Since the amount of light absorbed by the diffraction grating 11 is small, the amount of light emitted from the light source 20 is efficiently emitted to the optical disc 21.

  The light absorption rate of the second member 14 at the wavelength λ1 is preferably 5% or less. When the light absorption rate exceeds 5%, the ratio of the amount of light emitted from the light source 20 to the optical disc 21 decreases, and the amount of light emitted from the light source 20 is increased in order to keep the amount of light emitted to the optical disc 21 constant. This is necessary. In addition, the light absorption rate of the second member 14 at the wavelength λ1 is preferably 1% or more. This is because if the light absorptance is less than 1%, the concentration of the dye 17 is not so low, and the curing reaction of the second resin 16 is difficult to complete completely.

  The maximum absorption wavelength λamax in the light absorption of the second member 14 is shorter than the wavelength λ1 and the absorption edge wavelength λa + is between the wavelengths λ1 and λ2. Examples of the dye 17 include Solvent Red91 and Solvent Red122. There is.

  In the present invention, the dye 17 includes not only those that appear colored, but also those that have light absorption properties in the ultraviolet and infrared wavelength regions and are colorless and transparent. The dye 17 is dissolved in the second resin 16 at a molecular level, and is distinguished from a pigment in which particles are dispersed and suspended in the resin.

  In the first embodiment, the maximum absorption wavelength λamax in the light absorption of the second member 14 is shorter than the wavelength λ1, and the absorption edge wavelength λa + is between the wavelengths λ1 and λ2. However, the maximum absorption wavelength λamax may be longer than the wavelength λ2, and the absorption edge wavelength λa− may be between the wavelengths λ1 and λ2. At this time, the absorption edge wavelength λa− is preferably set in the vicinity of the wavelength λ2. In addition, the light absorption rate of the second member 14 at the wavelength λ <b> 2 is preferably slightly larger than the light absorption rate of the second resin 16.

  In the first embodiment, the second member 14 has the same refractive index as that of the first member 13 at the wavelength λ1 and has a different refractive index from that of the first member 13 at the wavelength λ2. However, the second member 14 may have the same refractive index as that of the first member 13 at the wavelength λ2 and a different refractive index from that of the first member 13 at the wavelength λ1. In that case, the diffraction element 10 includes a diffraction grating 11 for DVD.

  Next, a method for manufacturing the diffraction element 10 according to the first embodiment will be described. First, the first resin 15 is applied on the transparent substrate 12 to a uniform thickness. Examples of the application method include spin coating and spraying. Next, the first resin 15 is cured according to a method for curing the first resin 15.

  Next, the surface of the first resin 15 is irradiated with ultraviolet light through a mask pattern that forms a predetermined pattern and developed to form a predetermined uneven shape by the first member 13. As a specific method for manufacturing an uneven shape, for example, there are the following methods. One is a method in which a resist is applied onto the first resin 15, ultraviolet rays are irradiated through a mask pattern so as to form a predetermined pattern, and after development, dry etching is performed. Alternatively, a photosensitive material may be used as the first resin 15, applied to a predetermined uniform thickness, and developed by irradiating with ultraviolet rays through a mask pattern so as to have a predetermined uneven shape. .

  Separately, the dye 17 is dissolved in the second resin 16 at a molecular level and sufficiently stirred, and applied so as to fill a predetermined uneven shape of the first member 13. The method of application is a spin coating method, a spray method, or the like as in the case of the first resin 15. Next, the second resin 16 is cured by the second resin 16 curing method with the solvent 17 dissolved at the molecular level to obtain the second member 14 and the diffraction grating 11.

  Finally, the transparent substrate 18 is bonded to the diffraction grating 11 with an adhesive 19. The diffraction grating 11 is sandwiched between the transparent substrate 12 and the transparent substrate 18 and is protected from the external environment, such as prevention of scratches and prevention of moisture and gas from entering from the outside.

  FIG. 3 is a cross-sectional view of a diffraction element having another configuration according to the first embodiment. It is good also as a structure like the diffraction element 24 shown in FIG. In contrast to the diffraction grating 11, the diffraction grating 25 in FIG. 3 is configured such that the second member 14 is formed in a predetermined uneven shape, and the first member 13 is filled with the uneven shape. The difference between the diffraction grating 11 and the diffraction grating 25 is only the above, and the difference between the diffraction element 10 and the diffraction element 24 is only the difference between the diffraction grating 11 and the diffraction grating 25. Therefore, the description of the diffraction element 10 and the diffraction grating 11 is used for the description of the diffraction element 24 and the diffraction grating 25.

  FIG. 4 is a cross-sectional view of a diffraction element to which the diffraction element of the first embodiment is applied. In FIG. 4, the diffraction element 30 includes a first diffraction grating 31 and a second diffraction grating 38 arranged in series with respect to the traveling direction of the light emitted from the light source 20. The first diffraction grating 31 receives light of two wavelengths λ1 and λ2 from the light source 20, and is arranged alternately on the light incident surface to form the first member 33 and the second member constituting the first diffraction grating 31. Member 34. The first diffraction grating 31 transmits the light having the wavelength λ1 and separates the light having the wavelength λ2 to be emitted to the second diffraction grating 38. The second diffraction grating 38 receives light of two wavelengths from the first diffraction grating 31, and is arranged alternately in the light incident surface to constitute the second diffraction grating 38, a third member 40 and a fourth member 41, Is provided. The second diffraction grating 38 separates the light of wavelength λ1 and transmits the light of wavelength λ2 to be emitted to the optical disc 21.

  The first diffraction grating 31 is formed on the transparent substrate 32. The second diffraction grating 38 is formed on the transparent substrate 39. The first diffraction grating 31 and the second diffraction grating 38 are bonded with an adhesive 45.

  The first member 33 includes a first resin 35 and has a predetermined refractive index at two wavelengths λ1 and λ2. The second member 34 includes a second resin 36 in which a dye 37 is dissolved at a molecular level, and has light absorption in a predetermined wavelength range. The second member 34 has the same refractive index as the first member 33 at the wavelength λ1 and a different refractive index from the first member 33 at the wavelength λ2.

  On the other hand, the third member 40 includes a third resin 42 and has a predetermined refractive index at two wavelengths λ1 and λ2. The fourth member 41 includes a fourth resin 43 in which a dye 44 is dissolved at a molecular level and has light absorption in a predetermined wavelength range. The fourth member 41 has a refractive index different from that of the third member 40 at the wavelength λ1 and the same refractive index as that of the third member 40 at the wavelength λ2.

  Here, since the first member 33 and the third member 40 are the same as the first member 13, the description thereof is incorporated. Moreover, since the 2nd member 34 and the 4th member 41 are the same as that of the 2nd member 14, the description is used. In this way, it is possible to configure the diffraction element 30 capable of independently diffracting the light with the wavelength λ1 and the light with the wavelength λ2.

  The maximum absorption wavelength λamax of the second member 34 in the light absorption of the second member 34 is outside the two wavelengths λ1 and λ2, and the absorption edge wavelength λa + of the second member 34 is between the two wavelengths λ1 and λ2. It is characterized by that. The maximum absorption wavelength λamax of the fourth member 41 in the light absorption of the fourth member 41 is outside the two wavelengths λ1 and λ2, and the absorption edge wavelength λa + of the fourth member 41 is between the two wavelengths λ1 and λ2. It is characterized by that. The second member 34 can reduce the concentration of the dye 37. For this reason, the time required to dissolve the dye 37 in the second resin 36 and the time required to cure the second resin 36 can be shortened. The fourth member 41 can also reduce the concentration of the dye 44. For this reason, the time required to dissolve the dye 44 in the fourth resin 43 and the time required to cure the fourth resin 43 can be shortened. Therefore, the time required for production can be shortened.

(Embodiment 2)
The second embodiment will be described with reference to the drawings. First, an outline of the optical pickup device of the second embodiment will be described. FIG. 5 is a diagram showing an optical system of the optical pickup device according to the second embodiment, FIG. 6A is a top view with the cover of the optical pickup device according to the second embodiment removed, and FIG. 6B is an optical pickup. It is a bottom view of an apparatus.

  The optical pickup device 50 according to the second embodiment includes the light source 20 and the diffraction element 10 described in the first embodiment. As described in the first embodiment, the light source 20 emits light of two wavelengths λ1 and λ2 toward the optical disc 21. As described in the first embodiment, the diffraction element 10 receives light of two wavelengths λ1 and λ2 from the light source 20, and is arranged alternately on the light incident surface to constitute the diffraction grating 11. And a second member 14. The diffractive element 10 transmits light having one wavelength λ1 and separates light having the other wavelength λ2 and outputs the separated light to the optical disc 21. The first member 13 includes a first resin 15 and has a predetermined refractive index at two wavelengths λ1 and λ2. The second member 14 includes a second resin 16 in which a dye 17 is dissolved at a molecular level, absorbs light in a predetermined wavelength range Δλa, has the same refractive index as the first member 13 at one wavelength λ1, and the other And a refractive index different from that of the first member 13 at the wavelength λ2. The maximum absorption wavelength λamax in light absorption of the second member 14 is outside the two wavelengths λ1 and λ2, and one absorption edge wavelength λa + is between the two wavelengths λ1 and λ2.

  The difference between the refractive index of the material in which the dye 17 is dissolved and the refractive index of the material in which the dye 17 is not dissolved is larger as the wavelength is closer to the maximum absorption wavelength, and the smaller the concentration of the dye 17 is, the smaller. By using the dye 17 having the absorption edge wavelength λa + between the two wavelengths λ1 and λ2, the maximum absorption wavelength λamax approaches the two wavelengths λ1 and λ2. Therefore, this difference in refractive index becomes large. On the other hand, the difference in refractive index can be reduced by reducing the concentration of the dye 17. Therefore, by using the dye 17 having the absorption edge wavelength λa + between the two wavelengths λ1 and λ2, the concentration of the dye 17 can be reduced without changing the difference in refractive index between the two wavelengths λ1 and λ2. . Therefore, the time required to dissolve the dye 17 in the second resin 16 and the time required to cure the second resin 16 can be shortened. Therefore, the time required for production can be shortened.

  Next, the optical system of the optical pickup device 50 according to the second embodiment will be described in detail with reference to FIG. The light source 20 and the diffraction element 10 are as described in the first embodiment, and the description thereof is incorporated. The diffractive element 10 generates light used for CD tracking control.

  The integrated prism 51 is made of optical glass such as BK7, and has three inclined surfaces 51a, 51b, 51c in order from the side closer to the diffraction element 10 inside. A polarization separation film 51d is formed on the inclined surface 51a. The polarization separation film 51d is formed of a dielectric film, and transmits light emitted from the light source 20 that is P-polarized light and reflects light reflected from the optical disk 21 that is S-polarized light. A wavelength selective polarization separation film 51e is formed on the inclined surface 51b. The wavelength selective polarization separation film 51e is formed of a dielectric film, transmits outgoing light that is P-polarized light, transmits light of wavelength λ1 among reflected light that is S-polarized light, and reflects light of wavelength λ2. A hologram 51f is formed on the inclined surface 51c. Light having a wavelength λ2 reflected by the optical disc 21 is incident on the hologram 51f. The hologram 51f is formed with a diffraction grating. The hologram 51f includes light used for focus control and light used for tracking control according to a region where the reflected light having the wavelength λ2 from the optical disc 21 is incident on the hologram 51f. To separate.

  The collimating lens 52 makes light emitted from the light source 20 that is diffused light substantially parallel light, and makes reflected light from the optical disk 21 that is parallel light become focused light. The reflection mirror 53 reflects and bends the optical path so as to make the size of the optical pickup device 50 compact. The reflection mirror 53 transmits part of the light from the light source 20. The light transmitted through the reflection mirror 53 enters the light receiver 58 and is used to control the amount of light emitted from the light source 20. The rising prism 54 is a prism for raising the emitted light from the light source 21 that is substantially parallel to the optical disc 21 in a direction substantially perpendicular to the optical disc 21. The rising prism 54 may be a rising mirror.

  The hologram element 55 includes a polarization hologram 55a and a wavelength plate 55b. The polarization hologram 55a is made of a material having wavelength selectivity so as to act only on the light of wavelength λ1 among the reflected light from the optical disc 21. The polarization hologram 55a is formed with a diffraction grating, and the polarization hologram 55a is used for focus control and tracking control according to the region where the reflected light of wavelength λ1 from the optical disc 21 is incident on the polarization hologram 55a. Separated into light. The wave plate 55b converts the outgoing light from the light source 20 that is P-polarized light into circularly polarized light, and converts the reflected light from the optical disk 21 that is circularly polarized light into S-polarized light. The wave plate 55b is set to have a refractive index and a thickness so as to act on both the wavelengths λ1 and λ2. The hologram element 55 is mounted on the objective lens driving device 62 together with the objective lens 56 and moves together with the objective lens 56 in the focus direction and the tracking direction with respect to the optical disc 21.

  The objective lens 56 is a bifocal objective lens, and is configured such that light of wavelength λ1 and light of wavelength λ2 emitted from the light source 20 are focused on the recording surface of the optical disc 21, respectively. 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 light receiver 57 receives the reflected light from the optical disc 21, converts it into an electrical signal for reproduction, an electrical signal for focus control, an electrical signal for tracking control, etc., and outputs it. The light receiver 58 receives the emitted light from the light source 20, converts it into an electrical signal for output control of the emitted light, and outputs it.

  The light having the wavelength λ 1 emitted from the light source 20 passes through the diffraction grating 11 of the diffraction element 10 as it is, enters the integrated prism 51, passes through as it is, and enters the collimating lens 52. The outgoing light that has passed through the collimating lens 52 enters the DVD that is the optical disk 21 via the reflecting mirror 53, the rising prism 54, the hologram element 55, and the objective lens 56. The reflected light reflected by the optical disk 21 enters the hologram element 55 via the objective lens 56. The reflected light from the optical disk 21 separated into the focus control light and the tracking control light by the polarization hologram 55 a is incident on the integrated prism 51 via the rising prism 54, the reflection mirror 53, and the collimator lens 52. The reflected light passes through the wavelength selective polarization separation film 51e, is reflected by the polarization separation film 51d, and enters the light receiver 57.

  On the other hand, the light of wavelength λ2 emitted from the light source 20 is separated and transmitted to the tracking control light by the diffraction grating 11 of the diffraction element 10, enters the integrated prism 51, passes through as it is, and enters the collimator lens 52. . The outgoing light that has passed through the collimating lens 52 is incident on the CD that is the optical disk 21 via the reflecting mirror 53, the rising prism 54, the hologram element 55, and the objective lens 56. The reflected light reflected by the optical disk 21 enters the hologram element 55 via the objective lens 56 and is transmitted without being separated, and passes through the rising prism 54, the reflection mirror 53, and the collimating lens 52 to the integrated prism 51. Incident. The reflected light is reflected by the wavelength selective polarization separation film 51e, separated into light for focus control and light for tracking control by the hologram 51f, and enters the light receiver 57.

  Next, the configuration of the optical pickup device 50 will be described. In FIG. 6, a base 59 forms a skeleton of the optical pickup device 50, and components constituting the optical pickup device 50 including various optical components are attached to the base 59 directly or via an attachment member. The base 59 is made of an alloy material such as a Zn alloy or an Mg alloy, or a hard resin material.

  The light source 20, the diffraction element 10, the integrated prism 51, and the light receiver 57 are mounted on one coupling member 60 to constitute a light source module 61. The light source module 61 is attached to the base 59 via the coupling member 60. The objective lens 56 and the hologram element 55 are mounted on the objective lens driving device 62, and the objective lens driving device 62 is attached to the base 59. The collimating lens 52, the reflecting mirror 53, the rising prism 54, and the light receiver 58 are attached to the base 59 directly or via other members.

  In the optical pickup device 50 having such a configuration, since the diffraction element 10 that separates the tracking control light has a stable characteristic for a long period of time, the optical pickup apparatus 50 on which the diffraction element 10 is mounted also has a long period of time. Has stable characteristics. The diffraction element 10 may be the diffraction element 24.

  FIG. 7 is a diagram showing an optical system having another configuration of the optical pickup device according to the second embodiment. The optical system in FIG. 7 includes the diffraction element 30 described in the first embodiment. The description of the first embodiment is used for the diffraction element 30 and the light source 20. The diffraction element 30 separates light of wavelength λ1 and light of wavelength λ2 into light used for tracking control independently of each other.

  The integrated prism 71 is made of optical glass such as BK7, and includes inclined surfaces 71 a and 71 b in order from the side closer to the diffraction element 30. A polarization separation film 71c is formed on the slope 71a. The polarization separation film 71c transmits light emitted from the light source 20 that is P-polarized light and reflects light reflected from the optical disk 21 that is S-polarized light. An astigmatism generation element 71d is formed on the inclined surface 71b. The astigmatism generation element 71d makes the focal positions in two cross sections orthogonal to each other including the optical axis of the reflected light from the optical disc 21 be the front side and the rear side of the light receiver 76, respectively. This light is used for focus control.

  The wave plate 72 is the wave plate 55b, the collimating lens 73 is the collimating lens 52, the rising mirror 74 is the rising prism 54, the objective lens 75 is the objective lens 56, the light receiver 76 is the light receiver 57, and the light receiver 77 is the light receiver 58. Since it corresponds almost, those explanations are used. However, the reflection mirror 53 is abolished so that outgoing light transmitted through the rising mirror 74 enters the light receiver 77. The light source 20, the diffraction element 30, the integrated prism 71, and the light receiver 76 are attached to one coupling member 78 to constitute a light source module 79. The objective lens 75 is mounted on the objective lens driving device 80.

  Light emitted from the light source 20 having wavelengths λ1 and λ2 is incident on the diffraction element 30, light having the wavelength λ1 is separated by the second diffraction grating 38 for tracking control, and light having the wavelength λ2 is tracked by the first diffraction grating 31. The light is separated for control and emitted toward the optical disc 21. The emitted light is focused and incident on the optical disc 21 via the wave plate 72, the collimating lens 73, the rising mirror 74, and the objective lens 75. The reflected light reflected by the optical disk 21 enters the integrated prism 71 via the objective lens 75, the rising mirror 74, the collimating lens 73, and the wave plate 72. The reflected light is reflected by the polarization separation film 71 c, and light for focus control is generated by the astigmatism generation element 71 d and is incident on the light receiver 76. Light incident on the light receivers 76 and 77 is converted into an electrical signal and output.

  In the diffraction element 30, the second member 34 can reduce the concentration of the dye 37. For this reason, the time required to dissolve the dye 37 in the second resin 36 and the time required to cure the second resin 36 can be shortened. The fourth member 41 can also reduce the concentration of the dye 44. For this reason, the time required to dissolve the dye 44 in the fourth resin 43 and the time required to cure the fourth resin 43 can be shortened. Therefore, the time required for production of the diffraction element 30 can be shortened. Therefore, the time required for the production of the optical pickup device including the diffraction element 30 can be shortened.

  FIG. 8 is a diagram showing an optical system of still another configuration of the optical pickup device in the second embodiment. This optical system has a configuration in which another optical source 81 is added to the optical system shown in FIG.

  In the configuration of FIG. 8, the light emitted from the light source 20 is DVD light having a wavelength λ1 = about 650 nm and CD light having a wavelength λ2 = about 780 nm. The light emitted from the light source 81 is BD light having a wavelength λ3 = about 405 nm.

  The integrated prism 82 functions as a beam splitter so that the light emitted from the light source 81 is directed toward the optical disc 21 and the reflected light reflected by the optical disc 21 is directed toward the light receiver 84 instead of the light source 81. The astigmatism generation element 83 makes the focal positions in two cross sections orthogonal to each other including the optical axis of the reflected light from the optical disc 21 be the front side and the rear side of the light receiver 84, respectively. This light is used for focus control. The light receiver 84 receives the reflected light from the optical disc 21, converts it into an electrical signal for BD reproduction signal, an electrical signal for focus control, an electrical signal for tracking control, etc., and outputs it. The light source 81, the integrated prism 82, the astigmatism generation element 83, and the light receiver 84 are attached to the coupling member 85 to form a light source module 86.

  The hologram 87 transmits the light emitted from the light source 81 as it is. The hologram 87 diffracts the reflected light from the optical disk 21 and separates it into light used for tracking control and light used for focus control according to the position where the light is incident on the hologram 87.

  The beam splitter 88 has a slope inside, and the light having the wavelength λ1 and the light having the wavelength λ2 transmit the light emitted from the light source 20 and the light reflected from the optical disc 21 as they are. Further, the beam splitter 88 reflects light emitted from the light source 81 and reflected light from the optical disc 21 on the inclined surface. In this way, the beam splitter 88 aligns the light emitted from the light source 20 and the light emitted from the light source 81 on almost one optical path, and the light reflected from the optical disk 21 toward the light receiver 76 and the light receiver 84. Separated into the light going to.

  The wave plate 89 is a reflecting plate corresponding to three wavelengths. The collimating lens 90 makes light of three wavelengths substantially parallel.

  The rising mirror 91 reflects the light having the wavelength λ1 and the light having the wavelength λ2 that has been approximately parallel to the optical disk 21 until then, rises in a direction substantially perpendicular to the optical disk 21, and transmits the light having the wavelength λ3. The objective lens 95 converts the light raised by the rising mirror 91 into focused light and focuses it on a predetermined recording surface of the optical disc 21.

  The rising mirror 92 reflects the light having the wavelength λ3 that has been substantially parallel to the optical disc 21 until then, and rises in a direction substantially perpendicular to the optical disc 21. The objective lens 94 converts the light raised by the rising mirror 92 into focused light and focuses it on a predetermined recording surface of the optical disc 21. The rising mirror 92 transmits light having the wavelength λ1 and light having the wavelength λ2. The rising mirror 92 transmits part of the light having the wavelength λ3.

  The light transmitted through the rising mirror 92 enters the light receiver 93. The light incident on the light receiver 93 is converted into an electrical signal and output so as to be used for controlling the output of the emitted light from the light source 20 and the emitted light from the light source 81.

  The objective lens driving device 96 arranges the objective lens 94 and the objective lens 95 on one holder and moves the objective lens 94 and the objective lens 95 in the focus direction and the tracking direction, respectively.

  Also in the configuration of FIG. 8, the diffraction element 30 can shorten the time required for production of the diffraction element 30. Therefore, the time required for the production of the optical pickup device including the diffraction element 30 can be shortened.

(Embodiment 3)
The third embodiment will be described with reference to the drawings. 9 is a block diagram of the optical pickup module according to the third embodiment, FIG. 10 is a block diagram of the optical disk device according to the third embodiment, and FIG. 11 is a diagram showing a servo flow of the optical disk device according to the third embodiment. is there. In the third embodiment, the optical disk device 110 will be described as being equipped with the diffraction element 10 and the optical pickup device 50. However, the diffraction element 24 described with reference to FIG. 3, the diffraction element 30 described with reference to FIG. The optical pickup apparatus having the optical system described in FIG. 8 may be mounted.

  In FIG. 9, the drive mechanism of the optical disk device 110 including a rotation drive unit that rotates the optical disk 21 and a moving unit that moves the optical pickup device 50 closer to or away from the rotation drive unit is referred to as an optical pickup module 100. The base 101 forms a framework of the optical pickup module 100, and the optical pickup module 100 is configured by disposing each component directly or indirectly on the base 101.

  The rotation drive unit includes a spindle motor 102 having a turntable 102a on which the optical disk 21 is placed. The spindle motor 102 is fixed to the base 101. The spindle motor 102 generates a rotational driving force that rotates the optical disc 21.

  The moving unit includes a feed motor 103, a screw shaft 104, a main shaft 105, and a sub shaft 106. The feed motor 103 is fixed to the base 101. The feed motor 103 generates a rotational driving force necessary for the optical pickup device 50 to move between the inner periphery and the outer periphery of the optical disc 21. As the feed motor 103, a stepping motor, a DC motor, or the like is used. The screw shaft 104 has a spiral groove and is connected to the feed motor 103 directly or via several stages of gears. In the third embodiment, the feed motor 103 is directly connected. The main shaft 105 and the sub shaft 106 are fixed to the base 101 via holding members at both ends. The main shaft 105 and the sub shaft 106 support the optical pickup device 50 so as to be movable in the radial direction of the optical disc 21. The optical pickup device 50 includes a rack 107 having guide teeth that mesh with the grooves of the screw shaft 104. Since the rack 107 converts the rotational driving force of the feed motor 103 transmitted to the screw shaft 104 into a linear driving force, the optical pickup device 50 can move between the inner periphery and the outer periphery of the optical disc 21.

  Note that the rotation drive unit is not limited to the configuration described in the third embodiment as long as it can rotate the optical disc 21 at a predetermined rotation speed. The moving unit is not limited to the configuration described in the third embodiment as long as it can move the optical pickup device 50 to a predetermined position between the inner periphery and the outer periphery of the optical disc 21.

  The optical pickup device 50 is the same as that described in the second embodiment, and has a cover 63 attached to the configuration shown in FIG. The optical pickup device 50 mounted on the optical disc device 110 according to the third embodiment includes the light source 20 and the diffraction element 10 described in the first embodiment. As described in the first embodiment, the light source 20 emits light of two wavelengths λ1 and λ2 toward the optical disc 21. As described in the first embodiment, the diffraction element 10 receives light of two wavelengths λ1 and λ2 from the light source 20, and is arranged alternately on the light incident surface to constitute the diffraction grating 11. And a second member 14. The diffractive element 10 transmits light having one wavelength λ1 and separates light having the other wavelength λ2 and outputs the separated light to the optical disc 21. The first member 13 includes a first resin 15 and has a predetermined refractive index at two wavelengths λ1 and λ2. The second member 14 includes a second resin 16 in which a dye 17 is dissolved at a molecular level, absorbs light in a predetermined wavelength range Δλa, has the same refractive index as the first member 13 at one wavelength λ1, and the other And a refractive index different from that of the first member 13 at the wavelength λ2. The maximum absorption wavelength λamax in light absorption of the second member 14 is outside the two wavelengths λ1 and λ2, and one absorption edge wavelength λa + is between the two wavelengths λ1 and λ2.

  The difference between the refractive index of the material in which the dye 17 is dissolved and the refractive index of the material in which the dye 17 is not dissolved is larger as the wavelength is closer to the maximum absorption wavelength, and the smaller the concentration of the dye 17 is, the smaller. By using the dye 17 having the absorption edge wavelength λa + between the two wavelengths λ1 and λ2, the maximum absorption wavelength λamax approaches the two wavelengths λ1 and λ2. Therefore, this difference in refractive index becomes large. On the other hand, the difference in refractive index can be reduced by reducing the concentration of the dye 17. Therefore, by using the dye 17 having the absorption edge wavelength λa + between the two wavelengths λ1 and λ2, the concentration of the dye 17 can be reduced without changing the difference in refractive index between the two wavelengths λ1 and λ2. . Therefore, the time required to dissolve the dye 17 in the second resin 16 and the time required to cure the second resin 16 can be shortened. Therefore, the time required for production can be shortened. As a result, the time required for production of the optical disc apparatus 110 including the diffraction element 10 can also be shortened.

  The tilts of the main shaft 105 and the sub shaft 106 are adjusted by an adjustment mechanism that constitutes a holding member so that laser light emitted from the objective lens 56 of the optical pickup device 50 is incident on the optical disk 21 at a right angle.

  In FIG. 10, the casing 111 of the optical disc apparatus 110 is configured by combining an upper casing 111a and a lower casing 111b and fixing them together using screws or the like. The tray 112 is provided in the casing 111 so as to be able to appear and disappear. In the tray 112, the optical pickup module 100 provided with the cover 108 is arranged from the lower surface side. The cover 108 has an opening to expose the objective lens 56 of the optical pickup device 50 and the turntable 102a of the spindle motor 102. Further, in the case of the third embodiment, the feed motor 103 is also exposed so that the thickness of the optical pickup module 100 is reduced. The tray 112 has an opening and exposes at least a part of the objective lens 56, the turntable 102a, and the cover 108. The bezel 113 is provided on the front end surface of the tray 112, and is configured to close the entrance and exit of the tray 112 when the tray 112 is stored in the housing 111. The bezel 113 is provided with an eject switch 114, and when the eject switch 114 is pressed, the engagement between the housing 111 and the tray 112 is released, and the tray 112 can be brought into and out of the housing 111. The rails 115 are slidably attached to both sides of the tray 112 and the casing 111, respectively. There are circuit boards (not shown) inside the casing 111 and the tray 112, and a signal processing system IC, a power supply circuit, and the like are mounted. The external connector 116 is connected to a power / signal line provided in an electronic device such as a computer. Then, electric power is supplied into the optical disc apparatus 110 via the external connector 116, an electric signal from the outside is guided into the optical disc apparatus 110, or an electric signal generated by the optical disc apparatus 110 is sent to an electronic device or the like. To do.

  A flow of focus control and tracking control of the optical pickup device 50 will be described. In FIG. 11, the emitted light of wavelength λ1 for DVD emitted from the light source 20 passes through the diffraction grating 11 of the diffraction element 10 as it is and enters the optical disc 21. The reflected light reflected by the optical disk 21 is separated into focus control light and tracking control light by the polarization hologram 55 a of the hologram element 55 and enters the light receiver 57. The light emitted from the light source 20 having the wavelength λ 2 for CD is separated into light used for tracking control by the diffraction grating 11 of the diffraction element 10 and is incident on the optical disk 21. The reflected light reflected by the optical disk 21 is separated into focus control light and tracking control light by the hologram 51 f of the integrated prism 51 and enters the light receiver 57.

  The light of wavelength λ1 and the light of wavelength λ2 incident on the light receiver 57 are converted into electrical signals and sent to the analog signal processing unit 110a on the circuit board (not shown) of the optical disc apparatus 110 main body.

  The analog signal processing unit 110a performs calculation / band processing on the input signal and outputs the result to the servo processing unit 110b. The servo processing unit 110b generates a focus error signal FES and a tracking error signal TES based on the signal from the analog signal processing unit 110a and outputs the focus error signal FES and the tracking error signal TES to the motor driving unit 110c. The motor driving unit 110c generates a current for driving the objective lens driving unit 62 on which the objective lens 56 is mounted based on the input focus error signal FES and tracking error signal TES. As a result, control is performed so that the deviation of the focal point of the light beam collected on the optical disc 21 and the deviation with respect to the track are minimized.

  The controller 110d receives signals sent from the analog signal processing unit 110a, the servo processing unit 110b, and the motor driving unit 110c. The controller 110d performs arithmetic processing of these signals, sends out the result (signal) of this arithmetic processing to each unit, and controls each unit by causing each unit to drive and execute processing.

  As described above, the optical disc apparatus 110 according to the third embodiment includes the diffraction element 10 according to the first embodiment. Even if the diffraction element 10 is irradiated with light over a long period of time and used repeatedly, the diffraction grating 11 hardly changes in volume. As a result, since the diffractive element 10 has stable characteristics over a long period of time, the optical disk device 110 on which the diffractive element 10 is mounted also has stable characteristics over a long period of time.

  As described above, the diffractive element, the optical pickup device, and the optical disk device of the present invention have stable characteristics over a long period of time, and thus are preferably mounted on electronic devices such as personal computers and notebook computers.

(A) Cross-sectional view of the diffraction element according to the first embodiment, (b) Diagram showing wavelength characteristics of optical absorptance and refractive index (A) The figure which shows the comparison of the refractive index with and without the absorption edge wavelength between the wavelength λ1 and the wavelength λ2, and (b) The relation between the light absorption and the refractive index depending on the dye concentration Sectional drawing of the diffraction element of another structure in this Embodiment 1. Sectional drawing of the diffraction element which applied the diffraction element of this Embodiment 1 The figure which shows the optical system of the optical pick-up apparatus in this Embodiment 2. (A) Top view of the optical pickup device in Embodiment 2 with the cover removed, (b) Bottom view of the optical pickup device The figure which shows the optical system of another structure of the optical pick-up apparatus in this Embodiment 2. The figure which shows the optical system of another structure of the optical pick-up apparatus in this Embodiment 2. FIG. Configuration diagram of optical pickup module according to Embodiment 3 Configuration diagram of optical disc apparatus according to Embodiment 3 The figure which shows the flow of the servo of the optical disk apparatus in this Embodiment 3. Sectional view of a conventional diffraction element Illustration of anomalous dispersion effect The figure which shows the relationship between the wavelength and refractive index of the conventional 1st member and 2nd member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 24 Diffraction element 11, 25 Diffraction grating 12 Transparent substrate 13 1st member 14 2nd member 15 1st resin 16 2nd resin 17 Dye 18 Transparent substrate 19 Adhesive 20 Light source 21 Optical disk 22 Solvent 23 Solution 30 Diffraction element 31 1st 1 diffraction grating 32 transparent substrate 33 first member 34 second member 35 first resin 36 second resin 37 dye 38 second diffraction grating 39 transparent substrate 40 third member 41 fourth member 42 third resin 43 fourth resin 44 dye 45 Adhesive 50 Optical Pickup Device 51 Integrated Prism 51a, 51b, 51c Slope 51d Polarization Separation Film 51e Wavelength Selection Polarization Separation Film 51f Hologram 52 Collimator Lens 53 Reflection Mirror 54 Standing Prism 55 Hologram Element 55a Polarization Hologram 55b Wavelength Plate 56 Objective Lens 57, 58 Receiver 59 Base 60 Coupling member 61 Light source module 62 Objective lens driving device 63 Cover 71 Integrated prism 71a, 71b Slope 71c Polarization separation film 71d Astigmatism generating element 72 Wave plate 73 Collimating lens 74 Rising mirror 75 Objective lens 76, 77 Light receiver 78 coupling member 79 light source module 80 objective lens driving device 81 light source 82 integrated prism 83 astigmatism generation element 84, 93 light receiver 85 coupling member 86 light source module 87 hologram 88 beam splitter 89 wave plate 90 collimating lens 91, 92 standing mirror 94, 95 Objective lens 96 Objective lens driving device 100 Optical pickup module 101 Base 102 Spindle motor 102a Turntable 103 Feed motor 104 Screw shaft 105 In-shaft 106 Sub-shaft 107 Rack 108 Cover 110 Optical disk device 110a Analog signal processing unit 110b Servo processing unit 110c Motor drive unit 110d Controller 111 Housing 111a Upper housing 111b Lower housing 112 Tray 113 Bezel 114 Eject switch 115 Rail 116 External connector

Claims (5)

Light of two wavelengths is incident from a light source, and includes a first member and a second member that are alternately arranged in the light incident surface to form a diffraction grating, and transmits light of one wavelength and transmits light of the other wavelength. The light is a diffractive element that is separated and emitted to an optical disc,
The first member comprises a first resin and has a predetermined refractive index at the two wavelengths,
The second member includes a second resin in which a dye is dissolved at a molecular level, has light absorption in a predetermined wavelength region, has the same refractive index as the first member at the one wavelength, and the other wavelength. And having a refractive index different from that of the first member,
The diffraction element according to claim 1, wherein a maximum absorption wavelength in the light absorption of the second member is outside the two wavelengths, and one absorption edge wavelength is between the two wavelengths. 2. The diffraction element according to claim 1, wherein the one absorption edge wavelength is in the vicinity of a wavelength between the maximum absorption wavelength and the one absorption edge wavelength of the two wavelengths. The light absorption rate of the second member at a wavelength between the maximum absorption wavelength and the one absorption edge wavelength of the two wavelengths is slightly larger than the light absorption rate of the second resin. The diffraction element according to claim 1. A light source that emits light of two wavelengths toward the optical disc;
The light source includes light of the two wavelengths, and includes a first member and a second member that are alternately arranged within the light incident surface to form a diffraction grating, and transmits light of one wavelength. A diffractive element that separates and emits light of a wavelength to an optical disc,
The first member comprises a first resin and has a predetermined refractive index at the two wavelengths,
The second member includes a second resin in which a dye is dissolved at a molecular level, has light absorption in a predetermined wavelength region, has the same refractive index as the first member at the one wavelength, and the other wavelength. And having a refractive index different from that of the first member,
The optical pickup device, wherein the second member has a maximum absorption wavelength in the light absorption outside the two wavelengths and one absorption edge wavelength is between the two wavelengths. A light source that emits light of two wavelengths toward the optical disc;
The light source includes light of the two wavelengths, and includes a first member and a second member that are alternately arranged within the light incident surface to form a diffraction grating, and transmits light of one wavelength. A diffractive element that separates and emits light of a wavelength to an optical disc,
The first member comprises a first resin and has a predetermined refractive index at the two wavelengths,
The second member includes a second resin in which a dye is dissolved at a molecular level, has light absorption in a predetermined wavelength region, has the same refractive index as the first member at the one wavelength, and the other wavelength. And having a refractive index different from that of the first member,
An optical disc apparatus characterized in that a maximum absorption wavelength in the light absorption of the second member is outside the two wavelengths, and one absorption edge wavelength is between the two wavelengths.

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