KR100464008B1 - Manufacturing method of spherical lens, lens module and solid immersion lens, optical pick-up head for near field recorder - Google Patents

Abstract

The present invention includes a substrate bonding step of bonding the support thin plate on the substrate; A patterning step of forming a temporary spherical portion by patterning a lens forming material having fluidity, transparency and solidification on the support thin plate; A shape deformation step of deforming the shape of the temporary spherical portion by reflow to form a partial spherical portion; A solidifying step of solidifying the partial spherical portion; A substrate removing step of removing the substrate after the solidification; By presenting a manufacturing method of the spherical lens including, it is possible to increase the mass production and precision of the spherical processing, and to reduce the manufacturing cost.

Description

Manufacturing method of spherical lens, lens module, and solid-impregnated lens for optical field optical system, optical pick-up head using the same, MANUFACTURING METHOD OF SPHERICAL LENS

The present invention relates to a spherical lens which is a fine optical element applied to an optical pickup component, an optical communication system, and the like of a high density information recording apparatus. Specifically, the present invention provides fluidity to a lens forming material by a reflow method. By utilizing a spherical surface automatically formed by the surface tension of the fluid generated in this process as the surface of the spherical lens, a method of manufacturing the spherical lens more easily and precisely, and the optical recording and reproducing apparatus using the spherical lens It is about.

Recently, the rapid development of multimedia and information communication technology is largely due to the large capacity, high speed, low cost per information storage density. The improvement of personal computers, the rapid spread of data communication such as the Internet, the appearance of VOD (video on demand), and high-definition television are high-speed broadband optical signals that can transmit large amounts of data in real time, including video and audio signals. The need for optical communication is further increasing, and the need for mass information storage media is also increasing. In addition, in order to cope with the generalization of portable personal information devices according to the generalization of mobile communication environment, miniaturization, light weight, low power, and low cost of information storage devices, display devices, and imaging devices are required. The solution can be solved through miniaturization, light weight, and low cost of the optical elements constituting the device.

In view of the above trend, a new optical recording and reproducing method is required to overcome the limitations of the existing optical recording and reproducing method.

An optical recording medium or magneto-optical recording medium has a small bit (or recording mark) size and a narrow track width to have a high density recording capacity. However, the limitation due to the difference in the layer structure of the recording medium including the protective layer, the recording layer, and the reflective layer and the condensing method, the diffraction of the spot size of the light condensed on the recording medium to form bits in the recording film of the recording medium. Due to limitations such as limitations, studies on optical recording and reproducing methods are actively being conducted to overcome such limitations.

In order to solve the problem of the conventional far field optical recording and reproducing method, an optical recording and reproducing method using a near field has recently been proposed as a method for increasing the recording density in a region where light diffraction does not occur. .

The principle of near field optical recording and reproducing is as follows. Light entering the lens at an angle greater than or equal to the critical angle is totally reflected when traveling from a dense refractive index to a small one. At this time, due to total reflection of light, light of very small intensity exists on the surface of the lens, which is called an evanescent wave or dissipation wave. Using this evernet wave, it is possible to achieve high resolution, which is impossible because of the diffraction limit, which is an absolute limit of resolution due to diffraction of light in the far-field. The near field optical recording and reproducing optical system totally reflects the light in the lens to generate an Evernet wave on the surface of the lens, and records and plays back by coupling the Evernet wave and the recording medium.

On the other hand, a spherical lens for converging the light irradiated from the transmitting / receiving unit and irradiating the recording medium to the optical pickup head of the optical recording / reproducing apparatus, whether in a far field or near field method.

Conventionally, as a manufacturing method of the spherical lens, a method of processing the lens forming material by lapping and chemical-mechanical polishing, or after processing the mold of the lens, and melt the lens forming material therein After molding, the mold was cooled and fabricated.

However, the spherical lens is generally a hemispherical microscopic optical element, which is required to have a high degree of precision and a very small volume. Therefore, the manufacturing method is difficult. This has been pointed out as a problem.

An object of the present invention is to provide a manufacturing method of a spherical lens to solve the above problems, to increase the mass productivity and precision of spherical processing, and to reduce the manufacturing cost.

1 to 6 show an embodiment of the present invention,

1 is a process chart showing a manufacturing method of a spherical lens

2 is a process chart showing a manufacturing method of a lens module

3 is a partially cutaway perspective view showing a lens module;

4 is a cross-sectional view of the lens module;

5 is a configuration diagram showing a configuration of a near field optical system

6 is a cross-sectional view showing the structure of a slide type optical pickup head;

** Description of the symbols for the main parts of the drawings **

1: partial spherical part 2: support sheet

3: lens holder 4: bonding layer

10: lens module

The present invention comprises a substrate bonding step of bonding the support plate on the substrate in order to achieve the object as described above; A patterning step of forming a temporary spherical portion by patterning a lens forming material having fluidity, transparency and solidification on the support thin plate; A shape deformation step of deforming the shape of the temporary spherical portion by reflow to form a partial spherical portion; A solidifying step of solidifying the partial spherical portion; A substrate removing step of removing the substrate after the solidification; It provides a method for producing a spherical lens comprising.

Here, the patterning step may be constituted by any one or a combination of two or more of a photo drawing process, a dry etching method, a wet etching method, an extrusion molding method, an injection molding method, a screen printing method.

In addition, as another means for achieving the object of the present invention, between the solidifying step and the substrate removing step, the bonding layer forming step of forming a bonding layer by applying a bonding material on the support sheet; A lens holder alignment bonding step of aligning and bonding the lens holder substrate on which the insertion hole of the partial spherical portion is formed on the bonding layer; It proposes a method of manufacturing a lens module comprising a.

Furthermore, the present invention provides a solid-impregnated lens for the near field optical system and an optical pickup head for the near field optical system using the lens module.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 to 5 show an embodiment of the present invention, Figure 1 is a process chart showing a manufacturing method of the spherical lens, Figure 2 is a process chart showing a manufacturing method of the lens module, Figure 3 is a lens module 4 is a cross-sectional view showing the lens module, FIG. 5 is a block diagram showing the configuration of the near field optical system, and FIG. 6 is a cross-sectional view showing the structure of the slide type optical pickup head.

As shown, the manufacturing method of the spherical lens according to the present invention includes a substrate bonding step (FIG. 1A) for bonding the support plate 2 on the substrate 12; A patterning step of forming a temporary spherical portion 11 by patterning a lens forming material having fluidity, transparency and solidification on the supporting thin plate 2 (FIG. 1A); A shape deformation step (FIG. 1B) of deforming the shape of the temporary spherical portion by reflow to form a partial spherical portion 1; A solidifying step of solidifying the partial spherical portion (1); Removing the substrate 12 after the solidification (step 1c); It is configured to include.

The temporary spherical portion 11 formed by patterning the lens forming material on the supporting thin plate 2 has a structure having a predetermined sag height h and a radius R, and the supporting thin plate 2 is a transparent membrane. The temporary spherical portion 11 is formed in a state where the lens forming material is solidified.

Since the temporary spherical portion 11 is formed of a lens forming material having fluidity when melted, the temporary spherical portion 11 is automatically deformed into a partial spherical shape by reflow to form the partial spherical portion 1.

The lens forming material is optically transparent, and a material that can be melted by heating, or a material that is diluted and fluidized with an organic solvent or the like can be used.

Examples include polycarbonate, polymer such as PMMA, photoresist, glass with low melting temperature, and the like, and may also be determined according to the refractive index of the required material. When the temporary spherical portion 11 is melted, the lens forming material having fluidity is formed in a solidified state, and then the temporary spherical portion 11 is heated to be above the melting temperature of the lens forming material forming the temporary spherical portion 11 to have fluidity. It can be.

In addition, the optical performance of the spherical lens can be adjusted by adjusting the refractive index and the thickness of the support thin plate 2.

As shown in FIG. 1, a transparent supporting thin plate 2 having a thickness d is formed on one surface of the substrate 12, and then, by forming a temporary spherical portion 11 having a thickness h and a contact surface diameter D on the surface thereof. This process is described in detail as follows. First, the characteristics of the lens-forming material have a fluidity when heated and melted or dissolved in a solvent in a solidified state, and in this state, the surface tension is applied. have. The lens forming material also has transparency, at least when solidified. In addition, the lens-forming material has a solidification property that is solidified again over time in the molten state.

The patterning step may be any one of photolithography, dry etching, wet etching, press molding, injection molding, and screen printing. It can be easily implemented by one or a combination of two or more.

In the case where the lens forming material is a photosensitive film, the temporary spherical portion 11 can be easily processed by a development process by a photo drawing process, and processing precision and reproducibility are also very high.

In the drawing, although the temporary spherical portion 11 is illustrated in the form of a micro disc, assuming a spherical shape of the final lens, it may be changed into various shapes according to the shape of the lens required. Here, the dry or wet etching method is performed in the patterning step. In the case of use, the lens forming material is etched in a solidified state, so there is no fluidity and no surface tension is applied. On the other hand, when the extrusion forming method, the injection molding method, and the screen printing technique are used, the lens forming material is molten. Since it is molded to have fluidity, the surface tension also acts. However, in this process, since it is formed in an arbitrary shape in the process of being extruded or injected in the extrusion or injection exposure and the screen printing process, the partial spherical portion 1 of the desired shape cannot be obtained as the surface tension acting at this time.

The partial spherical portion 1 forms the temporary spherical portion 11 by reflow as described above, and the lens forming material, which has fluidity due to the reflow, has a shape that is part of the spherical surface by surface tension.

After the partial spherical shape has been formed, solidification of the fluidized lens forming material completes the partial spherical portion 1 of the microminiature spherical lens. That is, the temporary spherical portion 11 is formed into a desired spherical shape. In this state, if the temporary spherical portion 11 is reflowed, the temporary spherical portion 11 has fluidity, and the surface tension acts to form the desired spherical surface. When the solid state is solidified in this state, the partial spherical portion 1 can be obtained. will be.

The sag height Z and radius R of the partial spherical portion 1 formed by the reflow are determined by the size D and thickness h of the substrate contact surface of the temporary spherical portion 11 before reflow, the temperature of the reflow process, and the like. In addition, the partial spherical portion 1 formed by reflow and solidification may also be determined depending on the physical properties of the lens forming material forming the temporary spherical portion 11.

In other words, if the shape of the temporary spherical portion 11 is precisely reproducible, a reproducible spherical shape can be obtained.

As shown in FIG. 2, a bonding layer forming step (FIG. 2A) forming a bonding layer 4 by applying a bonding material on the supporting thin plate 2 between the solidifying step and the substrate removing step; A lens holder alignment bonding step (FIG. 2B) for aligning and bonding the lens holder 3 substrate having the insertion hole of the partial spherical portion 1 onto the bonding layer 4; It can be configured to include.

Thereby, as shown in FIG. 3 and FIG. 4, the lens module which has the structure provided with the lens holder 3 can be obtained.

A substrate 12 including a partial spherical portion 1 formed by a reflow technique and a separate lens holder 3 substrate having an insertion hole formed thereon are formed on the bonding layer 4 so that the partial spherical portion 1 can be inserted. After assembling and selectively removing the substrate 12 under the support thin plate 2, the spherical module can be obtained by dividing the substrate into individual lens units by dicing or the like.

In particular, the lens holder 3 can be precisely processed into any shape so as to easily assemble additional optical elements such as a focusing lens to the spherical lens according to the present invention, so that the additional optical elements can be manually assembled ( passive alignment). That is, the thickness of the lens holder 3 should be adjusted according to the depth of focus of the optical system to be added, and the size of the opening may be processed in accordance with the size and the clear aperture diameter of the optical element to be added.

According to the manufacturing method according to the present invention, when the partial spherical portion 1 is processed in the form of hemispheres, the prepared spherical lens can be used as a solid-impregnated lens (SIL) for near field optical system.

The near field optical recording and reproducing apparatus shown in FIGS. 5 and 6 will be described according to the optical path as follows.

The laser beam irradiated from the input light source 21 passes through a series of collimators 22, polarized beam splitters 23, and another optical splitter 24 to change the optical path 45 ° mirror 25. Is irradiated to the sliding optical pickup head 100 through the objective lens 26 which is a component of the sliding optical pickup head 100, and the focused laser light is optically aligned with the objective lens 26. Is incident on the assembled lens module 10 and irradiated onto the recording layer of the optical disk 20.

Here, the lens module 10 is manufactured by the manufacturing method according to the present invention.

The laser light incident on the recording layer of the optical disc 20 changes the property of the reflected light according to the optical property of the incident position. At this time, the input light is irradiated by the reflected light property (Kerr rotation angle, reflectivity, etc.). The digital information of the data stored in the location can be determined.

The optical information reflected from the recording layer of the optical disk 20 reverses the input optical path, and thus the lens module 10, the objective lens 26, the mirror 25, the optical splitter 24, and the half wavelength (λ / 2) A first photodiode 29 and a second photodiode 30 capable of reading a differential signal reflected from the recording layer of the optical disc via a plate 27 and a second polarized light splitter. The incident is divided.

The above process is for reading data stored in a high density optical disk, and in order to record information on the disk, the system can be configured to match the information recording method of the disk.

When the disc recording material is in the optical phase change method, data recording is possible by raising the optical power of the input light source to locally increase the temperature of the recording position on the disc to generate the phase shift of the recording layer.

In another case, when the material of the magneto-optical (MO) method is the information recording layer, information may be recorded and rewritten directly through the magnetic field generating device 40 coupled with the near field optical system.

That is, the magneto-optical information may be recorded by adjusting the direction and intensity of the magnetic field generated by the magnetic field generating unit and the intensity of the laser beam irradiated at this position according to the digital information to be recorded.

In order to adjust the intensity of the incident laser beam, a photo detector 34 may be applied to the system, and a portion of the laser light incident from the light source 21 passes through the first polarized light splitter 23 through the third focusing lens. It enters into the photodetector 34 which observes the intensity of the input laser light in real time, and feeds back the output of this photodetector so that the intensity of the input light emitted from the laser light source 21 is constant to the intensity necessary for recording / reproducing. It can be maintained.

The third photodiode 32, another optical detector, uses a portion of the laser light signal reflected from the optical disk 20 to provide a servo signal for tracking and focusing correction of near-field optics. It is used for the purpose of detecting).

The micro-gap between the optical disk 20 and the lens module 10 is a trailing edge of the lens module 10 having the objective lens 26 mounted on the slider microstructure 41 based on the sliding rectangle of the slider 41. It is held by the slide type optical pickup head 100 which is bonded to the side corresponding to ().

The sliding optical pickup head 100 is suspended by a suspension made to be flexible in the direction perpendicular to the surface of the optical disk 20 so that it can float and track on the surface of the rotating optical disk 20.

The spherical lens manufacturing method according to the present invention can improve the surface processing accuracy compared to the conventional, spherical forming process is naturally formed and high reproducibility, and the reflow process is simple, so that the aspect of spherical processing can be improved. This has the effect of reducing the manufacturing cost.

In addition, it is possible not only to freely adjust the protruding height and the radius of curvature of the partial spherical portion, but also to adjust the lens performance by arbitrarily adjusting the thickness of the support sheet, and to apply the various support sheet materials to adjust the refractive index. Ultimately, it will provide a variety of ways to adjust lens performance.

In addition, the lens holder not only provides an alignment image for mounting a focusing lens or the like by adjusting the thickness and the size of the insertion hole, but also provides convenience in handling the micro lens, and damages the lens portion. It also has a side effect of preventing it.

Claims (5)

A substrate bonding step of bonding the support thin plate on the substrate; A patterning step of forming a temporary spherical portion by patterning a lens forming material having fluidity, transparency and solidification on the support thin plate; A shape deformation step of deforming the shape of the temporary spherical portion by reflow to form a partial spherical portion; A solidifying step of solidifying the partial spherical portion; A substrate removing step of removing the substrate after the solidification; Method for producing a spherical lens comprising. The method of claim 1, The patterning step A method for producing a spherical lens, characterized by comprising any one or a combination of two or more of a photographing process, a dry etching method, a wet etching method, an extrusion molding method, an injection molding method, and a screen printing technique. The method of claim 1, Between the solidification step and the substrate removal step A bonding layer forming step of forming a bonding layer by applying a bonding material on the supporting thin plate; A lens holder alignment bonding step of aligning and bonding the lens holder substrate on which the insertion hole of the partial spherical portion is formed on the bonding layer; Method for producing a lens module, characterized in that it comprises a. A solid-impregnated lens for a near field optical system formed by the manufacturing method of claim 1. An optical pickup head for a near field optical system using a lens module formed by the manufacturing method of claim 3.