JP3600462B2 - Method for manufacturing hologram element - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hologram-mounted laser incorporated in an optical pickup used in an optical disk system, for example, a compact disk or a video disk.
[0002]
This is because the hologram element divides the light of the semiconductor laser reflected back to the disk and separates the tracking information signal and the recording signal for accurately reading out the recording signal, and the light receiving element or signal processing integrated with the light receiving element is separated. It is used in an apparatus for guiding each circuit to obtain an output signal.
[0003]
[Prior art]
1 and 2 show a conventional example.
[0004]
FIG. 1 shows an example of an element having a hologram pattern only on the upper surface, which is usually made of a material having good light transmission characteristics such as glass or acrylic resin.
[0005]
FIG. 2 schematically shows an example of a path of a laser beam diffracted by the hologram pattern of FIG. 1 and an example of a path of a portion of the laser emission light that does not contribute to signal processing.
[0006]
[Problems to be solved by the invention]
FIG. 2 schematically shows the state of diffracted light in a conventional hologram element.
[0007]
For simplicity, this figure omits the effects of refraction.
[0008]
In this example, the hologram element uses its 0th-order diffracted light and 1st-order diffracted light. The zero-order diffracted light is used to guide the emitted light of the laser as it is to irradiate the optical disk, and the plus first-order diffracted light of the returned light is projected onto a necessary portion of the light receiving element.
[0009]
However, as a characteristic of the hologram, in a glass hologram element which is particularly difficult to be blazed, the intensity of the minus primary light is the same as that of the plus primary light, and although the intensity is weak, high-order diffracted light is also generated at the same time. These lights do not contribute to signal processing and become stray light.
[0010]
In general, light emitted from a semiconductor laser has a certain spread and intensity distribution.
[0011]
In the design, not all the emitted light amount is introduced into the hologram pattern, but the size of the pattern is optimized according to the numerical aperture of the objective lens.
[0012]
For this reason, light that has not passed through the hologram pattern becomes unnecessary light, and light reflected at the hologram element interface can be the above-mentioned stray light. FIG. 3 schematically shows this state.
[0013]
These stray lights enter the light receiving element and cause a deterioration in the signal-to-noise ratio.
[0014]
Generally, an anti-reflection film is formed on the upper and lower surfaces of the hologram element to reduce reflection, but it is impossible to make the reflection zero.
[0015]
The present invention has been made in order to solve the above-described problems, and has as its object to reduce stray light.
[0016]
[Means for Solving the Problems]
The hologram element according to the present onset Ming, in a plane perpendicular to the emission axis of the laser beam of the semiconductor laser, a hologram element in which at least one hologram pattern is disposed on at least one of its sides, the The above object is achieved by forming a light absorbing material layer that absorbs light having the wavelength of the emitted light of the semiconductor laser.
[0017]
The above object is achieved by forming the light absorbing material layer on almost the entire surface except for the hologram pattern.
[0018]
The above object is achieved by the light absorbing material layer being the same material as the material forming the hologram pattern.
[0019]
At least the light absorbing material layer and the hologram pattern are formed on a core material made of a material transparent to the emitted light of the semiconductor laser, and the upper surface of the core material is flush. Achieve the above objectives.
[0020]
At least the light absorbing material layer and the hologram pattern are formed on a core material made of a material transparent to light emitted from the semiconductor laser, and the upper surface of the core material is used for signal processing. The above object is achieved by being inclined except for a region through which light passes.
[0021]
When manufacturing the above-described hologram device, connected by a runner the axis, and a step of integrally molding a light-absorbing material layer around including a step of integrally molding a plurality of the core material, at least side surfaces of said core member, The above object is achieved by the step of dividing the runner.
[0022]
That is, in view of the above problems, the present invention forms a layer of a light absorbing material on the side surface of the hologram element to reduce the reflection on the side surface.
[0023]
Further, by devising the shape of glass or resin serving as a core material of the hologram element, stray light components that do not pass through the hologram pattern and do not contribute to signal processing are absorbed to reduce stray light.
[0024]
Hereinafter, the operation of the present invention will be described.
[0025]
4 and 5 are schematic views of a hologram having a light absorbing layer according to the present invention on the side.
[0026]
The side light absorbing layer reduces stray light due to multiple reflections inside the core material.
[0027]
In this case, particularly with respect to the absorbing layer, if the refractive index is different at the interface with the core material, reflection occurs and the effect is reduced. Therefore, the material of the absorbing layer is preferably basically the same as the core material.
[0028]
On the other hand, when the core material is molded with resin, the degree of design freedom can be increased as compared with the case where glass is used. Therefore, a hologram having a structure in which a combination of the core material having the shape shown in FIG. 6 and the above-described absorption layer further absorbs laser output light other than the portion used in signal processing as shown in FIG. By forming the element, stray light can be further reduced.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0030]
FIG. 7 is a diagram showing an embodiment of the present invention. In the figure, a hologram pattern 2 is provided on the upper surface of a core material 1, a) is an example in which the entire side surface of the core material 1 is covered with a light absorbing material layer 3, and b) is an example of the core material 1. This is an embodiment in which only two side surfaces are covered with the light absorbing material layer 3, and c) is an embodiment in which the periphery of the hologram pattern 2 above the core material 1 and all side surfaces are covered with the light absorbing material layer 3.
[0031]
When covered with a light absorbing material, the diffraction state of light is absorbed as shown in FIG. 4 to reduce stray light, and as shown in FIG. 5, stray light generated from a light beam passing through the hologram element is also reduced.
[0032]
Here, the shape of the core portion 6 is formed substantially flush with the hologram pattern 2, but the present invention is not limited to this, and the hologram of the core portion 6 is formed as shown in FIGS. The pattern 2 forming surface may have an angle, and the light absorbing material layer 3 is buried by the angle, so that the upper surface of the light absorbing material layer 3 and the hologram pattern 2 forming surface are substantially flush. Is also good.
[0033]
FIG. 8 shows a method of manufacturing a hologram element. 8A shows an example of a conventional method, and FIG. 8B shows an embodiment based on the present invention.
[0034]
In the conventional example shown in FIG. 8A), a plurality of hologram patterns 2 are formed on a glass plate 4 (a-1) and cut out by dicing to form one element 5 (a-2).
[0035]
On the other hand, in the embodiment shown in FIG. 8B), the plurality of core portions 6 are integrally formed so as to be connected by the runner 7 (b-1). Next, the light absorbing material layer 3 is integrally molded (b-2), and then cut out by dicing or the like to manufacture one element 5. When the hologram pattern 2 and the light-absorbing material layer 3 are formed of the same material, it is preferable that the hologram pattern 2 and the light-absorbing material layer 3 be formed at the same time when they are integrally molded.
[0036]
【The invention's effect】
According to the present invention, it is possible to reduce stray light as compared with the conventional hologram element. By using this hologram element to form a hologram laser, the signal-to-noise ratio can be improved, and as a result, the laser Since the output of the hologram laser can be reduced, it is possible to provide a hologram laser with higher reliability and higher performance.
[0037]
Further, in the case of a hologram element using a resin, since the light absorption layer can be formed by integral molding with the core material, mass production becomes possible and cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a conventional hologram element.
FIG. 2 is a schematic diagram showing a diffraction state of light for signal detection by the conventional hologram element shown in FIG.
FIG. 3 is a schematic diagram of a beam of laser output passing through the hologram element by the conventional hologram element shown in FIG. 1;
FIG. 4 is a schematic view of a hologram element according to one embodiment of the present invention.
FIG. 5 is a schematic view of a hologram element according to one embodiment of the present invention.
FIG. 6 is a diagram showing a modification of the embodiment of the present invention when the shape of the core material of the hologram element shown in FIGS. 4 and 5 is changed.
FIG. 7 is a diagram showing one embodiment of the present invention.
FIG. 8 is a diagram comparing a manufacturing method of the present invention with a conventional manufacturing method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Core material 2 Hologram pattern 3 Light absorption material layer 4 Glass plate 5 Element 6 Core part 7 Runner

Claims (5)

A hologram element in which at least one hologram pattern is arranged on a surface perpendicular to a direction of an emission axis of a laser beam of a semiconductor laser, wherein at least one of side surfaces has light having a wavelength of emission light of the semiconductor laser. When manufacturing a hologram element formed by forming a light absorbing material layer that absorbs light, a step of integrally molding a plurality of core materials connected by a runner serving as an axis, and light around the core material including at least side surfaces of the core material A method for manufacturing a hologram element, comprising: a step of integrally molding an absorbing material layer; and a step of dividing the runner. A hologram element in which at least one hologram pattern is arranged on a surface perpendicular to the direction of the emission axis of the laser beam of the semiconductor laser, and the entire surface of the hologram pattern excluding the hologram pattern has a wavelength of the emission light of the semiconductor laser. When manufacturing a hologram element formed by forming a light absorbing material layer that absorbs light, a step of integrally molding a plurality of core materials connected by a runner serving as an axis, and substantially excluding the hologram pattern of the core material A method for manufacturing a hologram element, comprising: a step of integrally molding a light absorbing material layer over the entire surface; and a step of dividing the runner. 3. The method according to claim 1, wherein the light absorbing material layer is made of the same material as the material forming the hologram pattern. At least the light absorbing material layer and the hologram pattern are formed on a core material made of a material transparent to the emitted light of the semiconductor laser, and the upper surface of the core material is flush. The method for manufacturing a hologram element according to claim 1, wherein: At least the light absorbing material layer and the hologram pattern are formed on a core material made of a material transparent to the emission light of the semiconductor laser, and the upper surface of the core material is a laser used for signal processing. 4. The method for manufacturing a hologram element according to claim 1, wherein the hologram element is inclined except for a region through which light passes.

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