JP2002184017A - Optical head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-size lightweight optical head device, mounted with a phase correction element having small transmission wavefront aberrations and little changes in the transmission wavefront aberration over a wide temperature range. SOLUTION: In a phase correction element prepared, a liquid crystal layer 303 pinched between two substrates 301, 302 facing each other, he outer edges of the substrates 301, 302 are sealed with a sealing agent 304, an the border line where the sealing agent 304 is in contact with the liquid crystal layer 303 is set in an elliptical form with the ratio of the major axis to the minor axis of the ellipse being >=1.0 and <=1.3. The phase correction element is disposed between a quarter-wave plate and a collimation lens of the optical head device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical head device equipped with a phase correction element.

[0002]

2. Description of the Related Art The configuration of a conventional optical head device is basically the same as the configuration of the optical head device of the present invention. Therefore, the configuration will be described with reference to FIG. 6 showing the optical head device of the present invention. The linearly polarized (P-polarized) laser light emitted from the semiconductor laser 1 is transmitted through the polarization beam splitter 2, the collimator lens 3, the phase correction element 4, and the λ / 4 plate 5 in this order, and the P-polarized light is converted into circularly polarized light. The light passes through the objective lens 6 held by the actuator 7 and is focused on the optical recording medium 8. The condensed laser light is reflected including the optical information recorded on the optical recording medium 8 and travels in the opposite direction, and the λ / 4 plate 5 converts the circularly polarized light into a polarization plane S orthogonal to the P polarized light. The light is converted into polarized light, deflected by the polarization beam splitter 2, and
The optical information is read. The phase correction element 4 is controlled by the output voltage from the phase correction element control circuit 10, and changes the phase of the laser light from the semiconductor laser 1.

A phase correction element 4 used in a conventional optical head device is a liquid crystal sealing element and usually has a structure shown in FIGS. The liquid crystal sealing elements are substrates 101 and 102
A transparent electrode 106 in which an ITO transparent conductive film is processed on the surface of
A transfer unit 107 is formed, and two substrates 101, 1
02 has a cell structure in which the sealing agent 105 is applied to the outer edges of both substrates with the sides on which the transparent electrodes 106 and the like are formed facing each other, and thermocompression bonded. Liquid crystal is injected into the cell from an injection port 109 to form a liquid crystal layer 108.
Spacers for maintaining a desired cell gap and conductive beads coated with a conductive film to obtain conductivity between electrodes of two (upper and lower) substrates are mixed in the sealant 105. The liquid crystal layers are substrates 101, 1 in FIG.
However, it is not shown in FIG. 7 because it is very thin.

The transparent electrode 106 on the substrate 102 is composed of a plurality of partial electrodes. Each of the partial electrodes is conductively connected to the wiring electrode 103 of the electrode extraction portion 104 provided at the end of the substrate 102, and a voltage is supplied from the outside. The supply of the voltage to the electrode on the substrate 101 side which does not have the electrode take-out part is performed through the transfer part 107. The transfer portions 107 formed on both substrates are conductively connected by the sealant 105 mixed with conductive beads, and a voltage can be supplied from the wiring electrodes 103 of the electrode take-out portions 104 of the substrate 102.

[0005] The liquid crystal sealing element is mounted on an optical head device to improve the light condensing characteristics on an optical disk as the optical recording medium 8. The liquid crystal sealing element is disposed in the optical path of the laser light emitted from the semiconductor laser 1, and partially in the liquid crystal layer by the plurality of divided partial electrodes in the effective area of the liquid crystal sealing element through which the laser light passes. A voltage is applied to correct the wavefront aberration on the optical disk by changing the phase of the transmitted light at the applied portion.

[0006]

The liquid crystal sealing element is shown in FIG.
As shown in FIG. 2, the outer edge of the substrate 201 and the outer edge of the substrate 202 are generally fixed with a sealant 203.
Also in FIG. 9, the liquid crystal layer is very thin and is not shown. A substrate constituting the liquid crystal sealing element is bent by expansion or contraction of a liquid crystal layer in the liquid crystal sealing element due to a change in environmental temperature, and the cross-sectional shape of the element is, for example, as shown in FIG. FIG. 11 and FIG. 11 (cross-sectional view taken along the line BB ′ in FIG. 9). Here, 2 in FIGS. 10 and 11
04 is a liquid crystal layer. When the substrate is deformed as described above, the thickness of the liquid crystal layer is thicker at the center and thinner at the outer edge, and the wavefront of light passing through the liquid crystal sealing element is deformed, causing a phase lag at the center, causing Due to the transmitted wavefront aberration, the light-collecting characteristics on the optical disk deteriorate. SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and is equipped with a liquid crystal sealing element (phase correction element) having a small transmitted wavefront aberration over a wide temperature range. It is an object to provide a head device.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a semiconductor laser that emits light that is linearly polarized light, a phase correction element that changes the phase of the emitted light, and a light source that emits the phase-changed light. An optical head device comprising: an objective lens for condensing light on a recording medium; and a photodetector for detecting reflected light of the light from the optical recording medium, wherein the phase correction element comprises two opposing transparent substrates. A liquid crystal layer is interposed therebetween, and has a structure in which an outer edge of the transparent substrate is sealed with a sealant. A shape of a boundary line where the sealant and the liquid crystal layer are in contact is an ellipse, and the length of the ellipse is The ratio of the length of the axis to the minor axis is 1.
Provided is an optical head device characterized by being not less than 0 and not more than 1.3.

Also, a semiconductor laser that emits linearly polarized light, a phase correction element that changes the phase of the emitted light, and an objective lens that condenses the phase-changed light on an optical recording medium An optical head device comprising: a light detector that detects reflected light of the light from the optical recording medium, wherein the phase correction element has a liquid crystal layer sandwiched between two opposing transparent substrates, The transparent substrate has a structure in which an outer edge portion is sealed with a sealant, and a shape of a boundary line where the sealant and the liquid crystal layer are in contact is a polygon, and a shape of a boundary line between the liquid crystal layer and the optical axis of the light. Provided is an optical head device, wherein the ratio of the length of the longest perpendicular to the shortest perpendicular among the perpendiculars drawn from the intersection to each side of the polygon is 1.0 or more and 1.3 or less. I do.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an optical head device according to the present invention,
In the first embodiment of the phase correction element as a liquid crystal sealing element, as shown in FIG. 1A, an adhesive as a sealant 304, a liquid crystal layer 303 sealed after being injected from an injection port 305, and the like.
The shape of the boundary line contacting with is made elliptical. Then, the optical axis 306 of the light that is linearly polarized light from the semiconductor laser
Is designed so that the ratio of the length of the major axis to the minor axis is 1.0 or more and 1.3 or less in the ellipse centered at. With such a design, it is possible to reduce the fluctuation of the transmitted wavefront aberration caused by the expansion or contraction of the liquid crystal when the environmental temperature changes. The two substrates 301 and 302 have different lengths as shown in the cross-sectional view of FIG. Hereinafter, the substrate means a transparent substrate.

The ratio of the length of the major axis to the minor axis of the ellipse is 1.
When 0, the ellipse has a special shape, that is, a circle. It is preferable that the shape of the boundary line be a circle because the fluctuation of the wavefront aberration due to the temperature change of the environment can be further reduced.

A method for manufacturing the above-described phase correction element will be described below. First, using a screen printing machine, a dispenser, or the like, an adhesive is applied to the outer edge of one substrate 302 as a sealant 304. As the substrate, a glass substrate may be used, or a plastic substrate such as polycarbonate may be used. As the adhesive, any material may be used as long as the two opposing substrates can be bonded. However, a resin-based adhesive such as an epoxy resin or an acrylic resin is preferable because it can be cured by heat or light.

Next, another substrate 301 is placed on the substrate 302,
After the outer edges of the two substrates 301 and 302 are bonded and sealed with an adhesive to form a cell structure, liquid crystal is injected to form a liquid crystal layer 303, and a liquid crystal injection port 305 is sealed.

A second embodiment of the phase correction element in the optical head device of the present invention is, for example, as shown in FIG.
The shape of the boundary line where the sealant 404 and the liquid crystal layer 403 injected from the injection port 405 are in contact is a square which is one of polygons. The ratio of the length of the longest perpendicular to the shortest perpendicular among the perpendiculars drawn to each side of the rectangle from the intersection of the liquid crystal layer and the optical axis 406 of the light that is linearly polarized light from the semiconductor laser is 1.0 or more. And it is designed to be 1.3 or less.
Here, the square means a square and a rectangle.

In the above example, a square was described as a polygon. However, the present invention is not limited to this, and a polygon may be a triangle, a quadrangle, a pentagon, a hexagon, or the like. It may be a regular polygon. However, it is preferable that the shape is a regular polygon and the number of sides is large because the fluctuation of the wavefront aberration can be reduced. The method of manufacturing the phase correction element according to the second embodiment basically differs from the phase correction element according to the first embodiment only in the shape of the boundary line where the sealant 404 and the liquid crystal layer 403 are in contact. Is the same.

Further, the manufactured phase correction element can reduce the variation of the transmitted wavefront aberration similarly to the case of the phase correction element of the first embodiment. The manufactured phase correction element according to the first or second embodiment is arranged, for example, in the optical path between the collimator lens 3 and the λ / 4 plate 5, as shown in FIG. And CD, CD-ROM, D
An electric signal is supplied from the phase correction element control circuit 10 to the phase correction element 4 in order to improve the light condensing characteristics on an optical disk such as a VD, a phase change optical disk, a magneto-optical disk, and the like. The phase of the linearly polarized light from the semiconductor laser 1 transmitted through the λ / 4 plate is changed to circularly polarized light, and is converged on the optical recording medium 8 by the objective lens 6.

When the λ / 4 plate is not disposed, the liquid crystal sealing element is disposed, for example, between the collimator lens 3 and the objective lens 6. Although the phase of the linearly polarized light from the semiconductor laser 1 transmitted through the liquid crystal sealing element is changed, the linearly polarized light is condensed on the optical recording medium 8 by the objective lens 6 with the linearly polarized light.

The phase correction element according to the present invention can suppress the aberration generated by the phase correction element itself over a wide temperature range, and has a great effect in increasing the degree of light condensing on the optical recording medium.

[0018]

EXAMPLE 1 As shown in FIGS. 3 and 4, a phase correction element used in an optical head device was manufactured by first forming various electrodes on two substrates. I by sputtering
A TO transparent electrode film was formed to a thickness of 30 nm, a thickness of 0.5
Electrodes are patterned on 3 mm glass substrates 802 and 804 by a photolithography method and a wet etching method to form patterning electrodes 801, 803,
805 and a wiring electrode 806 were formed. Here, the patterning electrode 803 is divided into five partial electrodes.

A gap of 10 μm was provided between the partial electrodes to maintain mutual insulation. In FIG. 4, the solid line between the respective partial electrodes represents a gap of 10 μm. When connecting the other partial electrode and the wiring electrode across one partial electrode, a gap of 10 μm was provided between the former partial electrode and the wiring electrode for insulation.

Next, a polyimide film having a thickness of about 60 nm was applied on the substrates 802 and 804 on which the patterning electrodes were formed by flexographic printing and baked. After subjecting the polyimide film to an alignment treatment by rubbing using a cloth,
As shown in FIG. 5, an epoxy resin-based adhesive was printed as a sealant 901 by a screen printing method on a substrate on which a patterning electrode was formed. The sealant 901 includes:
3% of a fiber spacer having a diameter of 5 μm (based on mass, the same applies hereinafter) was mixed with 2% of an acrylic resin ball of 5.5 μm having a surface coated with a conductive coating. here,
The fiber spacer is for maintaining a gap between the liquid crystal cells, and the acrylic resin sphere is for obtaining conductivity between the patterning electrode 801 of the substrate 802 and the patterning electrode 805 of the substrate 804.

The substrates 802 and 804 are overlapped after the alignment between the patterning electrodes 801, 803 and 805 as shown in FIG. At 170 ° C., the external force 6 × 10 ⁴ N / m ² crimped in addition to these substrates, a liquid crystal cell was produced. An injection port 902 is formed in the liquid crystal cell by vacuum injection.
After injecting liquid crystal into the liquid crystal layer 904 from the
2 is sealed with a UV-curable adhesive, and the external dimensions are 10 ×
A 13 mm phase correction element was manufactured.

The shape of the boundary between the sealant 901 for sealing the liquid crystal and the liquid crystal layer 904 is circular with the optical axis 905 as the center. When the transmitted wavefront aberration was measured within a circle having a radius of 4 mm and centered on the optical axis 905 of the manufactured phase correction element, it was 0.025λ or less within a temperature range from −40 ° C. to + 90 ° C.

As shown in FIG. 6, the produced phase correcting element is installed as a phase correcting element 4 between the λ / 4 plate 5 and the collimating lens 3 arranged in the optical head device. 4 was controlled by the output voltage from the phase correction element control circuit 10. The linearly polarized (P-polarized) laser light emitted from the semiconductor laser 1 is polarized by a polarization beam splitter 2, a collimating lens 3, a phase correction element 4, and a λ / 4 plate 5.
, And the P-polarized light was converted into circularly polarized light, passed through the objective lens 6 held by the actuator 7, and collected on the optical recording medium 8. The condensed laser light is reflected including the optical information recorded on the optical recording medium 8 and travels in the opposite direction, and the λ / 4 plate 5 converts the circularly polarized light into a polarization plane S orthogonal to the P polarized light. The light was converted into polarized light, deflected by the polarizing beam splitter 2, and optical information was read by the photodetector 9. The optical head device equipped with this phase correction element had excellent light condensing characteristics on the optical disk, and the read optical information had good jitter characteristics.

Example 2 As in Example 1, a phase correction element used in an optical head device was manufactured by first forming various electrodes on two substrates, as shown in FIGS. On a glass substrate 802 and 804 having a thickness of 0.4 mm, an ITO transparent electrode film having a thickness of 30 nm was formed by a sputtering method.
The electrode is patterned by photolithography and wet etching to form a patterned electrode 80.
1, 803, 805 and a wiring electrode 806 were formed.
Here, the patterning electrode 803 is divided into five partial electrodes.

A gap of 15 μm was provided between each of the partial electrodes to maintain mutual insulation. In FIG. 4, a solid line between each of the partial electrodes represents a gap of 15 μm. When connecting the other partial electrode and the wiring electrode across one partial electrode, a gap of 15 μm was provided between the former partial electrode and the wiring electrode for insulation.

Next, a polyimide film having a thickness of about 40 nm was applied on the substrates 802 and 804 on which the patterning electrodes were formed by flexographic printing and baked. After subjecting the polyimide film to an alignment treatment by rubbing using a cloth,
As shown in FIG. 5, an epoxy resin-based adhesive was printed as a sealant 901 by a screen printing method on a substrate on which a patterning electrode was formed. The sealant 901 includes:
3% of fiber spacers having a diameter of 8 μm and 2 μm of acrylic resin balls having a diameter of 9 μm having a conductive coating on the surface.
% Mixed. Here, the fiber spacer is for maintaining the gap between the liquid crystal cells, and the acrylic resin sphere is provided between the patterning electrode 801 of the substrate 802 and the substrate 8.
This is for obtaining conductivity with the patterning electrode 805 of FIG.

As shown in FIG. 5, the substrates 802 and 804 are overlapped after the alignment between the patterning electrodes 801, 803 and 805. At 170 ° C., an external force of 6 × 10 ⁴ N / m ² was applied, and these substrates were pressed to produce a liquid crystal cell. An injection port 902 is formed in the liquid crystal cell by vacuum injection.
After injecting liquid crystal into the liquid crystal layer 904 from the
2 is sealed with a UV-curable adhesive, and the external dimensions are 8 × 1
A 0 mm phase correction element was produced.

The shape of the boundary between the sealant 901 for sealing the liquid crystal and the liquid crystal layer 904 is circular with the optical axis 905 as the center. When the transmitted wavefront aberration was measured within a circle having a radius of 4 mm and centered on the optical axis 905 of the manufactured phase correction element, it was 0.025λ or less within a temperature range from −40 ° C. to + 90 ° C.

In the optical head device according to the present embodiment, the λ / 4 plate 5 shown in FIG. 6 is not used, and a non-polarizing beam splitter is arranged in the same place instead of the polarizing beam splitter 2 so that the collimating lens 3 and Between the objective lens 6, the produced phase correction element is installed as the phase correction element 4,
It was controlled by the output voltage from the phase correction element control circuit 10.

The optical head device equipped with this phase correction element had excellent light condensing characteristics on an optical disk, and the read optical information had good jitter characteristics.

[0031]

As described above, according to the present invention, the shape of the boundary line between the sealant of the phase correction element installed in the optical head device and the liquid crystal layer is made elliptical or polygonal and optimized. In addition, the transmitted wavefront aberration of the phase correction element can be reduced, and the fluctuation of the wavefront aberration due to the fluctuation of the environmental temperature can be reduced. Accordingly, the transmitted wavefront aberration is reduced, so that the optical head device incorporating this element has improved light focusing characteristics and jitter characteristics, and can record and reproduce information at high density.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing an example of a first embodiment of a phase correction element according to the present invention, wherein FIG. 1A is a plan view and FIG.

FIG. 2 is a plan view showing an example of a second embodiment of the phase correction element according to the present invention.

FIG. 3 is a pattern diagram of a transparent electrode formed on one substrate constituting the phase correction element of the embodiment.

FIG. 4 is a pattern diagram of a transparent electrode formed on the other substrate to be matched with the pattern of the transparent electrode of FIG. 3;

5 is a plan view of a phase correction element configured by combining the patterns of the transparent electrodes in FIGS. 3 and 4. FIG.

FIG. 6 is a conceptual diagram showing an example of an optical head device according to the present invention.

FIG. 7 is a perspective view showing an example of a conventional liquid crystal sealing element.

FIG. 8 is a plan view showing an example of a conventional liquid crystal sealing element.

FIG. 9 is a perspective view showing another example of a conventional liquid crystal sealing element.

FIG. 10 is a sectional view taken along line A-A ′ of the liquid crystal sealing element of FIG. 9;

FIG. 11 is a sectional view taken along line B-B ′ of the liquid crystal sealing element in FIG. 9;

[Explanation of symbols]

 1: Semiconductor laser 4: Phase correction element (liquid crystal sealing element) 6: Objective lens 8: Optical recording medium 301, 302, 802, 804: Substrate 304, 404, 901: Sealant 303, 403, 904: Liquid crystal layer 306 , 406, 905: Optical axis 305, 405, 902: Sealing port

Claims (3)

[Claims] 1. A semiconductor laser that emits light that is linearly polarized light, a phase correction element that changes the phase of the emitted light, and an objective lens that condenses the light whose phase has been changed on an optical recording medium. And a photodetector that detects light reflected from the optical recording medium of the light, wherein the phase correction element has a liquid crystal layer sandwiched between two opposing transparent substrates, The transparent substrate has a structure in which an outer edge portion is sealed with a sealant, and a shape of a boundary line where the sealant and the liquid crystal layer are in contact is an ellipse, and a length of a major axis of the ellipse with respect to a minor axis is smaller. An optical head device having a ratio of 1.0 or more and 1.3 or less. 2. The optical head device according to claim 1, wherein a ratio of a length of the major axis to the minor axis is 1.0. 3. A semiconductor laser that emits linearly polarized light, a phase correction element that changes the phase of the emitted light, and an objective lens that condenses the phase-changed light on an optical recording medium. And a photodetector that detects light reflected from the optical recording medium of the light, wherein the phase correction element has a liquid crystal layer sandwiched between two opposing transparent substrates, The transparent substrate has a structure in which an outer edge portion is sealed with a sealant, and a shape of a boundary line where the sealant and the liquid crystal layer are in contact is a polygon, and the boundary between the liquid crystal layer and the optical axis of the light is From the intersection,
An optical head device, wherein a ratio of a length of a longest perpendicular line to a shortest perpendicular line among perpendicular lines dropped on each side of the polygon is 1.0 or more and 1.3 or less.