JP2006330487A - Optical element, method of manufacturing optical element, and optical desk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element having an identification mark capable of securing visibility without sacrificing an effective surface area even in the case of a small-sized optical element, and to provide a method of manufacturing the optical element, and an optical desk device. <P>SOLUTION: A diffractive element 8 is formed rectangular in the plane direction and the identification mark formed from an anti-refractive film 9 is formed from a metal film 8e on the corner part of the surface. The metal film 8e has excellent visibility and when the diffractive element 8 is formed rectangular, a large identification mark 9a is formed without sacrificing the effective surface area of the diffractive element 8 by forming the identification mark 9a using a nearly triangular region outside of a far field pattern LL of an optical beam. As a result, the visibility is improved even in the identification mark 9a formed out of the effective surface area of the small-sized diffractive element 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical element and a method for manufacturing the same. Specifically, the present invention relates to an optical element having an identification mark with excellent visibility, a method for manufacturing the optical element, and an optical disc apparatus.

For example, a CD (compact disc) device or the like includes a diffractive element as an optical element that divides a light beam from a light source into a plurality of light beams and diffracts them into an optical recording disk. As this diffraction element, for example, an element in which a convex periodic grating is formed on a translucent substrate is known.
Some optical elements such as diffractive elements have different optical characteristics and installation positions in the optical system, but some of them are difficult to distinguish with the naked eye because of their very similar shapes and colors. Furthermore, even with one optical element, since the optical characteristics are partially changed, there are some which have a limited installation posture or front and back. Therefore, as shown in Patent Document 1, in the conventional optical element, an identification mark is formed by a film made of the same material as the optical film in a portion other than the effective use area on the surface of the optical element.
JP-A-8-106002

  Although the identification mark disclosed in Patent Document 1 is not a problem as long as it is a relatively large optical element, in recent years, in the field of optical pickups, for example, 1 as an optical element used in the optical system as the apparatus is downsized. In the case of a diffraction element of 0.5 mm × 2.0 mm, the identification mark of Patent Document 1 has a problem that visibility is extremely poor and workability is lowered. In the worst case, there is a problem that the optical element is incorrectly attached. In order to improve the visibility, when the identification mark is enlarged, the identification mark is formed outside the predetermined area where the optical film is formed. There is a problem that the effective area of the optical element is reduced by reducing the area in the formed predetermined region.

  Accordingly, an object of the present invention is to provide an optical element having an identification mark that can ensure visibility without sacrificing the effective area of the optical element, even a small optical element, a method for manufacturing the optical element, and an optical disk To provide an apparatus.

  In order to solve the above problems, the present invention is characterized in that in the optical element in which the identification mark is formed, the identification mark is formed of a metal film.

  The optical element to which the present invention is applied can be used in an optical disc apparatus. Such an optical disk device has a laser light source, a photodetector, an outward path for guiding the light beam emitted from the laser light source to the optical recording disk, and a return path for guiding the return light reflected by the optical recording disk to the photodetector. An optical system comprising the optical element, wherein the optical system includes the optical element between the laser light source and the forward path or the return path between the optical recording disk and cuts off the light beam emitted from the laser light source. The identification mark is disposed outside the area.

  In the present invention, it is preferable that the optical element is formed in a quadrangular shape and the identification mark is formed in a corner portion thereof. The identification mark is preferably formed in a triangular shape. Since the cross-sectional area (far field pattern) of the light beam emitted from the semiconductor laser is elliptical, in the case of an optical element formed in a square, when the far field pattern is formed on the optical element to the maximum, the corner Is outside the far field pattern. Therefore, by forming the identification mark in a triangle along the corner triangle that is outside the far field pattern, a larger identification mark can be formed without sacrificing the effective area of the optical element. .

  In the present invention, the metal film preferably has a slit for relaxing the stress of the film itself. If comprised in this way, even if stress will arise in metal film itself, stress will be relieve | moderated by the slit formed in the metal film. Therefore, as compared with the case where the metal film is solidly formed on the surface of the optical element, the metal film can be configured to be less likely to peel from the surface of the optical element.

  In the present invention, the metal film may be a part of what is disposed in all the grooves of the diffraction element when the diffraction element as the optical element is formed.

  In the present invention, in the optical element manufacturing method, the diffractive element as the optical element is formed by a photolithography process, and a resist film that protects the metal film only at the position of the identification mark by a masking device in the photolithography process is provided. A metal film other than the metal film formed and protected by the resist film may be etched. If comprised in this way, the metal film as an identification mark can be formed with the masking apparatus in the photolithographic process which forms a diffraction element.

  In the present invention, in the optical element manufacturing method, a plurality of the optical elements are formed on a substrate, and then the identification marks are formed on the surfaces of the plurality of optical elements, and then the substrate is cut to form the optical elements. You may make it isolate | separate every. If comprised in this way, workability | operativity can be improved.

  As described above, in the optical element according to the present invention, the identification mark is formed of the metal film. The metal film has very high visibility compared to the optical film. Therefore, even a small identification mark formed outside the effective area of a small optical element can improve visibility. As a result, the effective area of the optical element can be increased.

[Embodiment 1]
(overall structure)
FIG. 1 is an explanatory view schematically showing a configuration of a main part of the optical disc apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, the optical disc apparatus 1 of the present embodiment includes a semiconductor laser 2 that emits a laser beam having a wavelength of 650 nm, for example, and a photodetector 3. Further, the optical disc apparatus 1 includes an optical system 40 including a beam splitter 41, a collimating lens 42, a rising mirror 43, and an objective lens 44 from the semiconductor laser 2 toward the optical recording disc 10, and these The optical element forms a forward path that guides the light beam emitted from the semiconductor laser 2 to the optical recording disk 10. Further, the optical system 40 includes a sensor lens 45 between the beam splitter 41 and the photodetector 3, and the objective lens 44, the rising mirror 43, the collimator lens 42, the beam splitter 41, and the sensor lens 45, A return path is configured to guide the return light reflected by the optical recording disk 10 to the photodetector 3. A front monitor 5 (monitoring light detection for detecting light reflected from the beam splitter 41 out of the light beam directed from the semiconductor laser 2 toward the optical recording disk 10 is located behind the beam splitter 41 when viewed from the photodetector 3. Device).

  The photodetector 3 is used to generate a focusing error signal and a tracking error signal when recording information by detecting return light reflected by the optical recording disk 10 or reproducing information. The focusing error signal and the tracking error signal are fed back to the objective lens driving device 7.

  In the optical disk apparatus 1 of the present embodiment, between the semiconductor laser 2 and the beam splitter 41, from the light beam emitted from the semiconductor laser 2, a sub beam composed of −1st order diffracted light, a main beam composed of 0th order light, and +1 A diffraction element 8 made of a grating or hologram element for generating a sub-beam made of the next diffracted light is provided. For this reason, it is possible to reproduce information by focusing a main beam composed of zero-order light on the track of the optical recording disk 10 by the objective lens 44 and detecting the return light by the photodetector 3. In addition, information can be recorded by condensing a main beam composed of zero-order light on the track of the optical recording disk 10 by the objective lens 44. Further, the sub-beam consisting of −1st order diffracted light and the subbeam consisting of + 1st order diffracted light are condensed by the objective lens 44 at a position sandwiching the spot of the main beam in the tangential direction of the track of the optical recording disk 10, and the return light is light By detecting with the detector 3, a tracking error signal can be obtained by the DPP method or the like.

(Configuration of diffraction element 8)
2 (a), 2 (b), and 2 (c) are plan views of the diffractive element used in Embodiment 1 of the present invention, respectively, and the diffractive element is cut along the longitudinal direction and a part thereof is enlarged. FIG. 2 is an enlarged view of the identification mark shown in FIG.

  As shown in FIG. 2A, the diffractive element 8 used in the optical disc apparatus 1 according to the present embodiment is a translucent substrate, for example, a glass substrate. Further, a diffraction grating 8c in which a planar direction is formed in a rectangular shape and a plurality of grooves 8g and protrusions 8h are alternately arranged along the direction orthogonal to the longitudinal direction (L) of the diffraction element 8 is formed on the surface. Have. Furthermore, a metal film 8e is formed on only one of the four corners of the diffraction element 8, and an antireflection film 9 is formed on the upper surface of the diffraction element 8 including the metal film 8e. In the case of this embodiment, by forming the metal film 8e as the identification mark 9a in this way, a specific corner is identified by the contrast between the region where the metal film 8e is formed and the region where the metal film 8e is not formed. can do. As shown in FIG. 2C, the identification mark 9a of this embodiment has a plurality of stripe-shaped metal films 8e arranged in parallel. In other words, a plurality of stripe-shaped slits 8f are formed in the metal film 8e.

  Here, as shown in FIG. 2A, the far field pattern LL which is a cross-sectional area of the light beam emitted from the semiconductor laser 2 is an ellipse, and the major axis direction thereof is the longitudinal direction (L) of the diffraction element. The minor axis direction corresponds to the direction orthogonal to the long direction (L) of the diffraction element. Also, the light beam emitted from the semiconductor laser 2 is used for condensing the optical recording disk 10 in the region indicated by the circle LL in FIG. In order to use the effective area of the diffractive element 8 to the maximum, the far field pattern LL is formed on the diffractive element 8 at the maximum, but the corner of the diffractive element 8 is outside the far field pattern LL. In the present embodiment, the identification mark 9a is formed in a triangle along the corner triangle that is outside the far field pattern LL.

(Diffraction element manufacturing method)
FIG. 3 is a diagram schematically showing a part of the diffraction element according to the first embodiment of the present invention, and is an explanatory diagram for explaining the manufacturing method thereof.

  Hereinafter, an embodiment of a method for producing the diffraction element 8 of the present invention will be described in detail with reference to FIG. First, in the first step, as shown in (a), for example, a glass substrate 1 is prepared as a translucent substrate.

  Next, in the second step, as shown in (b), a metal film is formed. As the metal film, a material that is different in etching property from a glass substrate and a diffraction grating film and that does not change during the deposition of the diffraction grating film is used.

  Next, in the third step, as shown in (c), a resist 11 is applied, then in the fourth step, pre-baking is performed to volatilize the solvent in the resist 11, and then in the fifth step, (d) As shown in the figure, the portion corresponding to the convex portion (grating portion) of the diffraction grating 8c is exposed using the glass mask plate 12, and then developed in the sixth step to melt the exposed resist 11 portion and remove it. The exposed portion 11a is left.

  Next, rinsing is performed in the seventh step, followed by drying (post-baking) in the eighth step, and then, in the ninth step, the metal film 8e is wet-etched as shown in (e).

  Here, in this embodiment, the metal film 8e is over-etched by the wet etching, and the remaining metal film 8e is made smaller than the non-exposed portion 11a as shown in (e). Yes.

  Next, in the tenth step, a diffraction grating film 8b is deposited as shown in FIG. When the diffraction grating film 8b is deposited, the diffraction grating film 8b is deposited on the non-exposed portion 11a and on the glass substrate 8a where the resist 11 does not exist when viewed from above. That is, as described above, since the cross-sectional saddle shape is formed by the remaining metal film 8e and the non-exposed portion 11a on the metal film 8e, the diffraction grating film 8b is formed on the non-exposed portion 11a and the glass. It becomes difficult to connect with the substrate 8a.

  Next, in the eleventh step, as shown in (g), the non-exposed portion 11a is removed using a resist stripping solution (for example, an acetone-based solvent) to remove the diffraction grating film 8b on the non-exposed portion 11a. The so-called lift-off is performed.

  Thereafter, the photolithography process is performed again. That is, in the twelfth step, as shown in (h), the resist 11 is applied, and then in the thirteenth step, pre-baking is performed to volatilize the solvent in the resist 11, and then in the fourteenth step, (i) As shown in FIG. 5, the portion corresponding to the position of the identification mark 9a is exposed in a state where it is shielded by using the glass mask plate 12, and then developed in the fifteenth step to dissolve the exposed portion of the resist 11 so that it is not exposed. The exposed portion 11a is left.

  Next, rinsing is performed in the sixteenth step, followed by drying (post-baking) in the seventeenth step, and then, in the eighteenth step, the metal film 8e is wet-etched as shown in (j). At that time, only the metal film 8e protected by the non-exposed portion 11a remains without being wet etched.

  Next, in a nineteenth step, as shown in (k), the resist 11 is removed using a resist stripping solution. Then, a diffraction grating 8c having a convex periodic grating 8c formed on the glass substrate 8a and a metal film 8e remaining only at the position of the identification mark are obtained.

  Next, in the twentieth step, as shown in (l), the diffraction element 8 having the identification mark 9a made of the metal film 8e is obtained by depositing the antireflection film 8d as a translucent material.

  In addition, in the said manufacturing method, although the manufacturing method was demonstrated using FIG. 3 which showed a part of diffraction element 8 typically for convenience, in the case of this form, it manufactures the several diffraction element 8 collectively. Yes. That is, the diffraction grating 8c corresponding to the plurality of diffraction elements 8 is formed on the glass substrate 8a, and then the identification mark 9a is formed for each diffraction element 8, and then the glass substrate 8a is cut to form the plurality of diffraction elements 8. Is manufacturing. FIG. 3 exaggerates the lamination of the glass substrate 8a in consideration of the ease of understanding of the explanation, but it is actually a very thin film.

(Effect of this embodiment)
As described above, the diffraction element 8 according to the present embodiment has a quadrangular planar direction, and the identification mark 9a is formed by the metal film 8e at the corner of the surface. The metal film 8e is excellent in visibility, and in the case of the diffraction element 8 formed in a square, by forming an identification mark 9a using a substantially triangular region outside the far field pattern LL of the light beam, A larger identification mark 9a can be formed without sacrificing the effective area of the diffraction element 8. Therefore, even the identification mark 9a formed outside the effective area of the small diffractive element 8 can improve visibility.

  In the present embodiment, since the identification mark 9a is formed in a triangle, the identification mark 9a is formed in a triangle so that the outer side of the far field pattern LL of the light beam is substantially along the triangle. A larger identification mark 9a can be formed without sacrificing the effective area.

  Furthermore, in this embodiment, the identification mark 9a of this embodiment has a plurality of stripe-shaped metal films 8e arranged in parallel. In other words, since a plurality of stripe-shaped slits 8f are formed in the metal film 8e, even if stress occurs in the metal film 8e itself, the stress is relieved by the slits 8f formed in the metal film 8e, and the diffraction element It becomes difficult to peel from the surface of 8.

  In the present invention, in the optical element manufacturing method, the diffractive element 8 is formed by a photolithography process, and a resist 11 film that protects the metal film 8e only at the position of the identification mark 9a is formed by a masking device in the photolithography process. Since the metal film 8e other than the metal film 8e protected by the 11 film is etched, the metal film 8e as the identification mark 9a can be formed by a masking device in the photolithography process for forming the diffraction element 8.

  Furthermore, in this embodiment, after the diffraction grating 8c corresponding to the plurality of diffraction elements 8 is formed on the glass substrate 8a in the method for manufacturing the diffraction element 8, and then the identification mark 9a is formed for each diffraction element 8. Since the plurality of diffraction elements 8 are manufactured by cutting the glass substrate 8a, workability can be improved.

[Other embodiments]
Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say, for example, in the above-described embodiment, the identification mark is a triangle, but is not limited thereto, and may be formed in various shapes such as an L shape and a quadrangle. Moreover, in the said embodiment, although the translucent board | substrate is made into the glass substrate 8a, it is not limited to this, For example, it is good also as a plastic substrate.

  Moreover, in the said embodiment, although the identification mark 9a is formed in the triangle, it is not necessarily limited to a triangle, A square may be sufficient. Furthermore, although a plurality of stripe-shaped slits 8f are formed in the metal film 8e, the metal film 8e may be formed as a solid without providing any slits 8f.

  Further, in the diffraction grating 8, grooves and protrusions are arranged along a direction orthogonal to the longitudinal direction (L) of the diffraction element 8, but the arrangement direction of the diffraction element 8 is limited to this. Instead, it may be formed in various shapes. For example, the groove portion and the ridge portion may be disposed along the longitudinal direction (L), or the groove portion and the ridge portion may be disposed at an inclination of 45 degrees with respect to the longitudinal direction (L). May be.

It is explanatory drawing which shows typically the structure of the principal part of the optical disk apparatus based on Embodiment 1 of this invention. (A), (b) is the top view of the diffraction element used in Embodiment 1 of this invention, respectively, and sectional drawing which cut | disconnects a diffraction element along a elongate direction and expands the part. is there It is explanatory drawing for demonstrating a part of diffraction element in Embodiment 1 of this invention typically, and explaining the manufacturing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 2 Laser light source 3 Photodetector 8 Diffraction element (optical element)
8a Glass substrate (substrate)
8e Metal film 8f Slit 8g Groove 9a Identification mark 10 Optical recording disk 11 Resist

Claims (8)

In the optical element on which the identification mark is formed,
An optical element in which the identification mark is formed of a metal film.   2. The optical element according to claim 1, wherein the optical element is formed in a quadrangular shape and the identification mark is formed in a corner portion thereof.   3. The optical element according to claim 1, wherein the identification mark is formed in a triangular shape.   4. The optical element according to claim 1, wherein the metal film has a slit for relaxing the stress of the film itself.   5. The optical device according to claim 1, wherein the metal film is a part of the metal film disposed in all the groove portions of the diffractive element when the diffractive element is formed as the optical element. element.   6. The method of manufacturing an optical element according to claim 1, wherein the diffractive element as the optical element is formed by a photolithography process, and only the position of the identification mark is formed by a masking device in the photolithography process. A method for manufacturing an optical element, comprising: forming a resist film for protecting a film; and etching the metal film other than the metal film protected by the resist film.   In Claim 6, after forming the said some optical element on a board | substrate, and forming the said identification mark on the surface of the said some optical element after that, the said board | substrate was cut | disconnected and separated for every said optical element. A method for manufacturing an optical element. An optical disc apparatus comprising the optical element defined in any one of claims 1 to 5,
A laser light source, a light detector, and an optical system constituting a forward path for guiding the light beam emitted from the laser light source to the optical recording disk and a return path for guiding the return light reflected by the optical recording disk to the light detector. And
The optical system includes the optical element between the laser light source and the forward path or the backward path of the optical recording disk,
An optical disc apparatus, wherein the identification mark is disposed outside a cross-sectional area of a light beam emitted from the laser light source.

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