JP2005161563A - Manufacturing method for aspheric shaped article and aspheric lens array formed by transferring aspheric shaped article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a plurality of aspheric shaped articles on a substrate with high interval precision and reduced irregularity, and an aspheric lens array reduced in aberration and uniform in characteristics using the aspheric shaped articles as molds. <P>SOLUTION: Particles 30 comprising a predetermined material are applied to the surface of a flat substrate 10 having a plurality of spherical or almost spherical recessed parts 20 formed to its surface from an inclined direction while rotating the flat substrate 10 around a rotary shaft 14 vertical to the surface of the flat substrate 10 under vacuum to form a film and the shape of the spherical or almost spherical recessed parts are processed to be adjusted to a desired aspheric shape. These aspheric recessed parts are used as molds to be filled with a transparent material having flowability and this transparent material is cured and released to form the aspheric lens array. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aspherical lens array used in the field of optical technology such as optical communication and information recording, and more particularly to a transfer mold manufacturing method used when the aspherical lens array is manufactured by a molding method.

  In the optical communication field, with the recent increase in communication capacity, it is necessary to transmit optical signals in parallel using a plurality of transmission paths. In the field of information recording using light, it is necessary to record and reproduce a large amount of information in parallel. In such a technique, it is necessary to simultaneously collect or collimate a plurality of light beams, and a lens with small aberration and uniform characteristics is required. An aspherical lens is a lens that meets such requirements, and its array is required.

Various methods for manufacturing an aspheric lens are known, but it is efficient to manufacture a lens array in which a plurality of lenses are arranged by a molding method. Conventionally, a transfer mold for lens molding has been manufactured by cutting a metal substrate (for example, see Patent Document 1) or wet etching of a glass substrate (for example, see Patent Document 2).
JP 2001-246684 A JP 2001-277261 A

  However, the fabrication of the microlens mold by the above-described cutting process can freely control the shape of the recesses, but each recess is processed independently, so a microlens array mold made up of a large number of microlenses is used. In the case of manufacturing, there is a problem that the lens diameter and the lens interval are likely to vary between lenses. Moreover, it has been virtually impossible to correct the shape of the mold once processed.

  Further, since the substrate is generally isotropically etched in the wet etching process, a spherical recess can be produced, but it is difficult to form an aspherical shape. Further, once the processed recess can be corrected by additional etching, it is impossible except for a large adjustment of the radius of the spherical surface.

  The present invention has been made paying attention to such conventional problems, and an object of the present invention is to provide a method of manufacturing an aspherical shaped object, particularly a plurality of surface recesses, with high spacing accuracy and small variations. It is in. Another object of the present invention is to provide an aspherical lens array with small aberration and uniform characteristics using the aspherical shape produced by the above method.

In the manufacturing method of an aspherical shape object of the present invention, a flat substrate having a plurality of spherical concave portions and / or convex portions arranged on the surface is arranged around a rotation axis perpendicular to the surface in a vacuum. The material particles are made incident from a direction inclined with respect to the surface of the substrate while being rotated, so that the shape of the spherical concave portion or convex portion is adjusted so as to be a desired aspherical shape.
It is desirable to process and adjust the shape of the spherical concave portion or convex portion by making the material particles incident and depositing on the substrate surface, or by making the material particles into ions and making them incident and etching the substrate.

  By rotating the spherical concave portion or convex portion and allowing the particles to enter from an oblique direction, film formation or etching having anisotropy can be performed, and processing adjustment from the spherical surface to the aspherical surface can be performed.

The spherical recess is preferably formed by liquid phase etching through a mask having a plurality of circular openings provided on the surface of the substrate.
If a mask is formed by photolithography and liquid phase etching is performed using this mask, spherical recesses can be easily obtained with an isotropic material substrate. And the dimensional variation of the recesses can be kept low. However, in an etching process, a spherical surface in an ideal sense is not always obtained. The spherical surface in the present invention includes a substantially spherical surface having some error with respect to such an ideal spherical surface.

  On the other hand, the spherical convex portion can be produced by filling the spherical concave portion formed as described above with a fluid material and curing it, and then transferring the spherical concave portion by peeling it from the substrate. desirable. Since the spherical concave portion is transferred as it is, the convex portion has the advantage of the concave portion as it is.

  The aspherical lens array of the present invention is produced by filling the surface concave portion of the aspherical shape formed by the above method with a fluid transparent material, curing it, and then peeling it off. Alternatively, the aspherical convex portion may be transferred once to prepare the aspherical concave portion, and then manufactured in the same manner.

  An aspherical lens can be designed to reduce aberrations in a spherical lens. However, in the present invention, the shape of the concave portion serving as a transfer mold can be accurately and collectively corrected, so a lens array comprising a plurality of lenses can be produced. However, there is little variation in the characteristics of the individual lenses, and the arrangement accuracy of the array can be improved.

  In the present invention, fine adjustment of the aspherical shape is performed in order to adjust the processing from the spherical surface to the aspherical surface by performing film formation or etching having anisotropy while rotating the spherical concave portion or convex portion. Can do. Moreover, an aspherical lens can be easily manufactured by using this aspherical concave portion or convex portion as a transfer mold.

The principle of the method of manufacturing the aspherical concave portion or convex portion according to the present invention will be described.
As shown in FIG. 1A, for example, a metal film is formed on the surface of the substrate 10 on which a plurality of spherical recesses 20 are formed by a method such as vacuum evaporation or sputtering. At this time, as shown in FIG. 2, the substrate stage 12 is tilted so that the deposited particles (film-forming particles) 30 are incident at an angle θ with respect to the perpendicular standing on the flat portion 22 of the substrate surface.

  When the film is formed in such an arrangement, the thickest film thickness is obtained on the concave surface having a normal line in the direction that coincides with the direction in which the film forming particles are incident, and almost no shadow is formed on the portion that is shadowed with respect to the evaporation source. No film is formed. For this reason, the film thickness of the film adhering to the surface inclined with respect to the incident direction of the flying film forming particles is distributed.

  Next, after the substrate was rotated by a certain angle around the rotation axis 14 perpendicular to the substrate surface and then formed in the same manner, a film having a film thickness distribution similar to the first film was formed in the first film formation. It is further formed on the film by shifting by the rotation angle. If this process is repeated, a film thickness that is simply the number of film formation times that of the first film formation is obtained at the bottom of the spherical concave portion, and the film thickness varies in the other portions because the film thickness varies with the number of times.

  When film formation is repeated many times while changing the rotation angle, the film thickness of the film formed on the spherical concave portion approaches a symmetric distribution around the bottom. The same applies even when the film is formed while the substrate is continuously rotated. Therefore, the film thickness distribution on the spherical concave surface is determined by the relationship between the substrate tilt angle during film formation, the film formation speed, the film formation time, the rotation angle increment or rotation speed of the substrate, the directivity of the film formation particles, etc. The aspherical shape can be freely controlled by changing the parameters. The directivity of the film formation particles can be controlled by adjusting the atmospheric pressure in the film formation tank.

  It is also possible to form a film while rotating it to a predetermined film thickness at a certain incident angle, and after changing the incident angle, it is possible to form a film while rotating it again to a predetermined film thickness. A non-spherical shape can be formed.

  Further, if the film is formed by making particles incident on the spherical convex portion 21 formed on the surface of the substrate 11 as shown in FIG. 1B from a certain angle, the film thickness is distributed. Therefore, an aspherical convex part can also be formed. Further, a case where both spherical concave portions and convex portions are arranged with respect to the substrate surface can be targeted.

An example of specific film forming conditions will be described.
A gold (Au) film is formed by vacuum deposition on the surface of the substrate on which the spherical recess is formed. The substrate is placed in a vacuum vapor deposition tank so that the incident angle θ of the film forming particles is 45 °. Film formation is performed by rotating the substrate by 30 ° every time a film thickness of 10 nm is formed. Assuming the case where vapor deposition is performed in a state where the inside of the tank is highly vacuumed and the directivity is enhanced, the film thickness distribution in the normal direction at each position after the 12th film formation is calculated as follows.

Spherical concave bottom (10nm / √2) x 12 times = 85nm
Substrate surface (flat part) (10 nm / √2) × 12 times = 85 nm
Inside spherical recess (position 45 ° from the bottom)
10 nm × 1 time + (10 nm × √3 / 2) × 2 times + (10 nm / 2) × 2 times = 37 nm

  Therefore, under this condition, an Au film is obtained in which the film thickness is distributed so that the film thickness decreases from the bottom to the shallower part in the spherical recess, and the spherical recess is converted to an aspheric recess. The

  When transfer molding is performed using this aspherical concave portion as a mold, an aspherical shape having a convex portion with a crest suppressed to a lower level than the original spherical surface can be produced. When the shape formed in this way is formed of a transparent material, it becomes an aspheric lens as it is.

Moreover, it is also possible to produce an aspherical concave lens by using the produced aspherical object having a convex part as a transfer mold.
Alternatively, it is also possible to transfer the produced aspherical shape having a convex portion to once form an aspherical concave portion and then retransfer this to form an aspherical lens as necessary.

The method for finely adjusting the spherical shape by forming a film with a distributed film thickness on the substrate surface has been described above. However, the shape can be similarly finely adjusted by means of etching the substrate surface by anisotropic etching. Is possible. Since charged ions can be incident on the substrate from a certain direction by being accelerated by an electric field, vapor-phase etching using the ions is suitable for the present invention.
The present invention will be described below based on examples.

  First, a chromium (Cr) film was formed on the surface of a quartz glass substrate, and openings having a diameter of 10 μm were provided at intervals of 250 μm by patterning by photolithography. Next, the glass substrate was etched with a hydrofluoric acid aqueous solution through this Cr film mask to form a plurality of spherical recesses.

  Next, an Au film is formed by vacuum deposition. The substrate is fixed to a substrate stage inclined at an angle of 45 ° with respect to the direction in which the film forming particles are incident from the vapor deposition source. The substrate stage is fixed to a rotation axis perpendicular to the surface thereof and includes a mechanism capable of rotating at a predetermined angle. The film formation was performed in units of film formation time for which the film thickness on the surface on which the film formation particles are perpendicularly incident becomes 10 nm. When the film was formed by rotating the substrate by 30 ° for each unit film formation time, the distribution was thick at the bottom of the spherical recess and the flat portion of the substrate surface where no recess was formed, and thin at the side of the recess. Obtained.

  The original spherical concave portion was used as a reference spherical surface, and the displacement of the obtained aspherical concave portion with respect to the reference spherical surface was evaluated by a three-dimensional shape measuring machine. It was confirmed that a spherical shape was obtained.

  Etching was performed in the same procedure as shown in Example 1 to form a plurality of spherical recesses. The concave portion was filled with an ultraviolet curable fluid resin, bonded to a quartz glass substrate, cured, and the cured resin was peeled off together with the substrate to form a plurality of spherical convex portions.

  Next, an Au film is formed on the obtained spherical convex portion by vacuum deposition. The substrate is fixed to a substrate stage inclined at an angle of 45 ° with respect to the direction in which the film forming particles enter from the vapor deposition source, as in Example 1. When film formation was performed under the same conditions as in Example 1, a thick film thickness distribution was obtained on the top of the spherical convex portion and on the flat portion of the substrate surface where the convex portion was not formed, and on the convex portion side surface.

  When the deviation with respect to the reference spherical surface was evaluated, it was confirmed that an aspherical shape in which a portion corresponding to the top surface of the hemispherical surface and the side surface of the intermediate portion of the edge was recessed was obtained.

The quartz glass substrate was etched in the same manner as in Example 1 to form a plurality of spherical recesses.
Next, this spherical recess is additionally processed by reactive ion beam etching. As an etching gas, carbon tetrafluoride CF ₄ was used. By applying a high frequency to the substrate by a power source independent of the high frequency power source for generating plasma, the directionality of ions can be enhanced. The substrate is fixed to a substrate stage inclined at an angle of 60 ° with respect to the direction in which ions are incident from the ion source. The substrate holder is fixed to a rotation axis perpendicular to the surface of the substrate holder and has a mechanism capable of rotating at a predetermined angle. The high frequency power is adjusted so that the etching rate is 200 nm / min while rotating the substrate by 30 °. Etching was performed.

  By etching with strong directivity, the side surface of the spherical recess can be processed to be recessed. When the obtained shape and the reference sphere were compared, it was confirmed that an aspheric shape was obtained.

Next, production of an aspheric lens array used as a collimator lens array will be described.
The aspherical shape of the aspherical lens is generally expressed by the following equation.
Z = Cr ² / {1+ (1−C ² r ² ) ^1/2 } + AD · r ⁴ + AE · r ⁶ + ···
Here, r is a distance in the radial direction from the center of the lens, and Z is a sag amount, that is, a distance in the optical axis direction from the lens vertex of the lens surface at the position of r. If the radius of curvature on the optical axis is R _D , C = 1 / R _D , and AD, AE,. Here, when all the higher-order coefficients of AD, AE,... Are 0, that is, Z represented only by the first term on the right side of the above expression indicates a spherical surface.

In this design example, it is assumed that a lens is formed of a resin having a refractive index of 1.41 on a quartz glass substrate (refractive index of 1.457). In order to obtain the highest coupling efficiency as a collimator, considering the higher order terms up to the sixth order term,
R _D = 1.0619 mm
AD = −0.05665 mm ⁻³
AE = −0.0526 mm ^-5
Is appropriate. This aspherical shape is shown in FIG. 3 in comparison with a spherical surface (AD = AE = 0). FIG. 4 shows a necessary film thickness distribution in consideration of manufacturing a lens having a diameter of 0.4 mm in which the difference between the two curves corresponds to the film thickness adjusted by film formation from the spherical surface. It can be seen that a film of about 90 nm may be formed on the bottom of the spherical recess.

  Therefore, first, the quartz glass substrate was etched in the same manner as in Example 1 to form eight spherical recesses having a diameter of 0.4 mm to form a one-dimensional array. Next, this substrate is fixed to a substrate stage of a vacuum deposition apparatus. This substrate stage is tilted at an angle of 45 ° with respect to the direction in which the film forming particles are incident from the vapor deposition source, and is fixed to a rotation axis perpendicular to the surface thereof. As described above, the Au film is formed in units of a film formation time in which the film thickness is 10 nm on the surface where the film formation particles are perpendicularly incident, and the substrate is rotated by 30 ° for each unit film formation time and is performed 13 times. It was. Thereby, the film thickness distribution shown in FIG. 4 is obtained.

  Next, an aspheric lens was fabricated by molding using the aspheric recess formed as described above as a molding die. First, after applying a release agent to the concave portion of the mold, an ultraviolet curable resin having a refractive index after curing of 1.41 is filled. Next, a quartz glass substrate having a thickness of 1.0 mm is pressed from above the mold and irradiated with ultraviolet rays in that state. After the resin is cured, the quartz glass substrate is released from the mold. As described above, an aspherical lens array 55 in which the aspherical lens elements 50 having the aspherical shape described above are arranged on the quartz glass substrate 52 can be formed as shown in FIG.

  A collimator was constructed using the obtained aspheric lens array, and its characteristics were evaluated. A pair of collimators composed of a single-mode optical fiber and a fabricated aspheric lens were arranged so that the optical axes of the optical fibers coincided, and adjusted so that collimated light propagated between the two aspheric lenses. When the insertion loss between the optical fibers was evaluated in this state, a sufficiently small value of about 0.2 dB was obtained.

  If a spherical convex shape is prepared at the beginning, the process may be started. By performing film formation or etching having anisotropy on this convex shape, an aspherical convex portion is formed and transferred to form an aspherical concave portion. If this recess is a transfer mold, an aspherical lens can be formed.

  In addition, the above-described aspherical lens manufacturing methods all described the formation of a convex lens. However, it goes without saying that a concave lens can be formed in the same manner by using an aspherical convex portion as a transfer mold.

  According to the method of the present invention, the film thickness distribution of the film formed on the surface of the spherical concave portion or convex portion is determined by the substrate tilt angle, the film forming speed, the film forming time, the rotation angle increment or the rotation speed of the substrate at the time of film forming. As described above, the aspherical shape can be freely controlled by changing these parameters since it is determined by the relationship such as the directivity of the deposited particles.

It is also possible to form a film while rotating it to a predetermined film thickness at a certain incident angle, and after changing the incident angle, it is possible to form a film while rotating it again to a predetermined film thickness. An aspherical shape can be formed.
Therefore, the method of the present invention can easily correct a rotationally symmetric shape, and thus can be used when correcting a shape in processing that requires precise shape accuracy.

It is a cross-sectional schematic diagram of the board | substrate which has a spherical recessed part (a) or convex part (b) used for this invention. It is a figure which shows the principal part of the apparatus which manufactures the aspherical shaped object of this invention. It is a figure which shows an example of the curved surface of an aspherical lens. It is a figure which shows an example of film thickness distribution required in order to correct a spherical recessed part to the aspherical recessed part for lenses. It is a cross-sectional schematic diagram which shows an example of an aspherical lens array.

Explanation of symbols

10, 11 Substrate 12 Substrate stage 14 Rotating shaft 20 Spherical concave portion 21 Spherical convex portion 22 Flat portion 30 Film forming particle 50 Aspherical lens element 55 Aspherical lens array

Claims (7)

  A flat substrate provided with a plurality of spherical recesses and / or projections arranged on the surface is inclined with respect to the surface of the substrate while rotating around a rotation axis perpendicular to the surface in a vacuum. A manufacturing method of an aspherical shape product, characterized in that processing particles are adjusted so that the shape of the spherical concave portion or convex portion becomes a desired aspherical shape by causing the material particles to enter from the above-described direction.   The method of manufacturing an aspherical object according to claim 1, wherein the substance particles are incident and deposited on the surface of the substrate.   2. The method of manufacturing an aspherical object according to claim 1, wherein the substance particles are ions, and the ions are incident to etch the substrate.   4. The aspherical shape according to claim 1, wherein the spherical concave portion is formed by liquid phase etching through a mask having a plurality of circular openings provided on the surface of the substrate. Manufacturing method.   The spherical convex portion is filled with a fluid material in a spherical concave portion formed by liquid phase etching through a mask having a plurality of circular openings provided on the surface of the substrate, and then cured. 4. The method of manufacturing an aspherical object according to claim 1, wherein the spherical concave portion is transferred and formed by being peeled off from the substrate.   After filling the surface concave portion of the aspherical shape manufactured by the manufacturing method according to claim 1, 2 or 3 with a transparent material having fluidity and curing, the shape of the surface concave portion is transferred by peeling. An aspheric lens array characterized by that. The shape of the surface convex portion is transferred by peeling and peeling the surface convex portion of the aspherical shape manufactured by the manufacturing method according to claim 1, 2 or 3 with a material having fluidity. An aspherical lens array in which the shape of the aspherical concave portion is transferred by filling the aspherical concave portion with a transparent material having fluidity and curing, followed by peeling.

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