JPH0442641B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens comprising preferably multiple gradient index lens portions formed within a transparent substrate.

Lens assemblies are used to take stereoscopic photographs, as lenses for copying machines, and as lenses for optical memory. Recently, lens assemblies have also been used as a means to focus beams emitted by minute light sources arranged in a matrix or array. It is used.

As an example of such a lens assembly, a unit lens system is a converging optical transmitter having a refractive index distribution that decreases in proportion to the square of the distance from the central axis in a cross section perpendicular to the central axis. There is a structure in which the lenses are bundled together (Special Publication No. 47-12820 ``Compound Lens Containing a Focusing Light Transmitter'').

However, although this structure is superior in that it does not require a spherical processing process to form individual lens elements, it is also possible to bundle a large number of lenses with the necessary precision so that their axes are aligned, and to form this bundle. There are problems such as the need for a large number of steps to maintain the same state.

Furthermore, when a semiconductor laser array or the like is used as a light source, the radiation angle of the beam emitted from the semiconductor is different in a direction perpendicular to the cleavage plane and in a direction parallel to the cleavage plane, and usually has an elliptical radiation angle. As an optical lens system for converging such a beam, one having a point-symmetric refractive index distribution is not necessarily optimal.

The present invention was invented to solve the above-mentioned problems, and it is possible to use the photolithography technology used in the IC manufacturing process. Even if a lens body with a 3-dimensional structure is required, there is no need for the process of bundling individual lenses as in the prior art disclosed in the aforementioned Japanese Patent Publication No. 47-12820. The object of the present invention is to provide a gradient index lens body that can also be used in a light source system having an elliptical radiation angle on its surface.

Embodiments of the present invention will be described below with reference to the drawings.

First, the principle of the gradient index lens body and the manufacturing method thereof according to the present invention will be explained with reference to FIGS. 1 and 2. In FIG. 1, a transparent substrate 1 made of a dielectric material such as glass or synthetic resin is A mask layer 2 is formed to block the transmission of the diffusion source.
A slit-shaped opening 3 is formed in the mask layer 2 so as to extend over the entire width of the transparent substrate 1.
When the diffusion source is diffused into the transparent substrate 1 through this slit-like opening 3, as shown in FIG. The lens body 5 contained therein is created. FIG. 2B shows the refractive index distribution in the zy plane including the center line 6 of the lens portion 4. As is clear from Figure 2B,
This refractive index distribution decreases or increases continuously from the transparent substrate surface 1a toward the thickness direction of the substrate, and becomes the same refractive index as the original transparent substrate 1 at a depth h from the transparent substrate surface 1a. This h coincides with the radius of the semi-cylindrical shape, and the refractive index distribution described above also holds true for all surfaces including the center line 6 of the lens 4. Note that the refractive index does not change in the y-axis direction.

The following two methods can be considered for diffusing a diffusion source into the transparent substrate 1 to obtain a predetermined refractive index distribution. One method is to provide a transparent substrate 1 made of a glass plate containing first ions constituting a glass modification oxide, which contributes to a change (i.e., increase or decrease) in the refractive index of this glass plate. This second ion may be replaced with the first ion by exchange diffusion of a second ion which may constitute the glass-modified oxide to a greater degree than the first ion, or the second ion may be replaced by the first ion. This is a method of diffusing ions while applying heat. Another method is to diffuse a monomer that changes (increases or decreases) the refractive index by copolymerizing with the polymer into a transparent substrate 1 made of a synthetic resin made of a transparent polymer. This is a method in which the above-mentioned copolymerization is carried out.

The above two methods are methods of diffusing the diffusion source into the transparent substrate, but another method for obtaining a predetermined refractive index distribution in the transparent substrate 1 is to diffuse the diffusion source into the transparent substrate ₁ .
By using a laser or the like, a concave part having a semi-cylindrical shape, which is a cylinder divided into two by a plane including its center line, is formed on the surface of a transparent substrate made of a glass plate, etc. In the case of a quartz-based optical fiber, etc. A non-isothermal plasma CVD method, which is used in In this method, the transparent substrate is coated so as to be buried, and then the coated transparent substrate is cut from the coating layer side so that the coated transparent substrate is reduced to the original thickness or a thickness smaller than the original thickness.

In the lens body according to the present invention, it is preferable to arrange a large number of gradient index lens parts in an array, an example of which is shown in FIG. In FIG. 3, each semi-cylindrical lens portion 4 has a second
It has substantially the same configuration as the semi-cylindrical lens portion shown in FIG. A, and these semi-cylindrical lens portions 4 are formed in a common transparent substrate 1 so as to be parallel to each other. In the case of the above-described lens assembly 5 shown in FIG. 3, the interval between the semi-cylindrical lens portions 4 can be set arbitrarily and can be selected with high precision.

As shown in FIG. 4, when the pair of lens assemblies shown in FIG. This has substantially the same function as if a normal convex lens were present at each intersection of the two, so that it is possible, for example, to focus parallel light into a large number of minute spots. Also, when a matrix of minute light sources corresponding to the above-mentioned intersections is arranged, it is possible to obtain a matrix of minute spots in the same way as in the case described above. Furthermore, the numerical aperture NA of the semi-cylindrical lens portions 4 and 4' shown in FIG.
By setting them to different values, it is possible to focus the light rays from a light source with an elliptical radiation angle, such as the semiconductor laser mentioned above, into approximately circular parallel light, etc.
It has superior features compared to a structure in which unit lens systems are bundled as in the case of the previously mentioned Japanese Patent Publication No. 47-12820.

The example shown in FIG. 4 consists of two transparent substrates 1 and 1'.
In this case, the semi-cylindrical lens parts 4, 4' are separately made and overlapped, but as shown in FIG. It is also possible to form lens portions 4', respectively, and to configure these lens portions 4, 4' to be orthogonal to each other.

Next, a specific example of a gradient index lens body and a method for manufacturing the same according to the present invention will be described.

Specific example 1 Optical glass commonly known as BK7 (SiO ₂ 68.9% by weight, B ₂ O ₃ 10.1% by weight, Na ₂ O 8.8% by weight, K ₂
50mm
A glass flat plate having a size of 50 mm x 5 mm and polished on both sides was prepared as a transparent substrate.

Next, as shown in FIG. 6, a Ti film with a thickness of 1 μm is formed on the entire surface of one side of the glass substrate 1 by sputtering, and then a slit-shaped opening with a width of 100 μm and a length of 45 mm is formed using photolithography technology. Section 3 was formed with a pitch of 1.5 mm. Then Tl ₂ SO ₄ 30
Mol%, _ZnSO4 40% Mol%. A treatment is carried out in which a mixed salt containing 30 mol% of K ₂ SO ₄ is heated and dissolved at 600°C, the transparent substrate is immersed in the molten salt, and ions in the molten salt and ions in the glass are exchanged through the opening.
I went there for 40 hours. Next, this transparent substrate is taken out from the molten salt, slowly cooled to room temperature, and then its surface is polished to remove the mask 2, thereby producing a gradient index lens assembly as shown in FIG. I got it. In FIG. 6, w1 indicates the width of the opening, which is 100 μm as described above. _w2 and h indicate the width and depth of the semi-cylindrical lens formed by the infiltration of Tl ions, w2 is approximately 500 μm,
The result was that h was approximately 450 μm.

When a helium-neon laser beam was made incident from the front surface of the lens assembly manufactured as described above as a parallel beam of 30 mmφ using a beam expander, the incident beam was separated at an interval of 1.5 mm at the focal point (focal length approximately 10 mm). It was possible to focus the light into a slit shape with a width of 10 μm and a width of 10 μm.

Specific example 2 Consisting of 64% by weight of SiO ₂ , 9% by weight of B ₂ O _{3 ,} 11.4% by weight of Na ₂ , 4.2% by weight of K ₂ O , 4.2% by weight of Al ₂ O ₃ , and 7.1% by weight of MgO and 50 mm × 50 mm A glass flat plate having a size of 5 mm was prepared as a transparent substrate.

The same molten salt heated to 550°C was subjected to the same masking treatment as in Example 1 described above, and ions were heated for 6 hours while applying a DC electric field, with the Ti film side as the anode and the opposite side as the cathode. After performing diffusion treatment and slow cooling treatment, the Ti film was removed.

The two substrates of the semi-cylindrical lens assembly produced in this manner were stacked on top of each other with their optical axes perpendicular to each other as shown in FIG. When a helium-neon laser beam was incident on the front surface as a parallel beam of 30 mm diameter using a beam expander, the incident beam could be focused into a spot with an interval of 1.5 mm and a diameter of 10 μm at the focal position.

Specific example 3 Allyl diglyte coal carbonate (commonly known as CR-39) to which 3% benzoyl peroxide was added was heated at 80°C.
By heating for 35 minutes at
A transparent substrate with dimensions of mm x 50 mm x 3 mm was obtained. the above
The refractive index of CR-30 was 1.504.

Polyethylene masks with a thickness of 1 mm, a width of 1 mm, and a length of 50 mm were attached in parallel to the surface of the transparent substrate at intervals of 3 mm, and then the masks were placed in vinyl benzoate (VB) monomer with a refractive index of 1.5775 and a temperature of 80°C. A transparent substrate was immersed, and the monomer was diffused into the transparent substrate from the surface other than the mask for 60 minutes to cause copolymerization. Next, this transparent substrate was heat-treated at 80° C. for several hours and its surface was polished to obtain a lens assembly as shown in FIG.

In addition, in the above-mentioned specific examples 1 to 3, a mask similar to the above-mentioned mask may be formed on the entire side edge and the entire back surface of the transparent substrate, if necessary, prior to the exchange diffusion or diffusion movement process.

Specific example 4 Prepare a 30mm x 30mm x 1mm quartz glass substrate,
Using a CO ₂ laser, a recess with a semicircular cross-section (50 μm radius) and a length of 30 mm is created on the surface of the glass substrate.
They were formed in parallel at 150 μm intervals.

Next, the above substrate was placed in a reaction tube installed in an electric furnace. The electric furnace had a structure in which a microwave resonator could reciprocate along the reaction tube. Add _SiH4 into the reaction tube
NH ₃ was gradually increased from 0 to 30 sccm, and NO ₂ was introduced at a rate of 10 sccm (standard cubic centimeter per minute).
A glassy layer was gradually decreased from 50 sccm to 0 sccm to deposit a glassy layer on the substrate so as to fill the recesses. During this period, the substrate was kept at about 300° C., and a frequency of 2.45 _GHZ was sent to the microwave resonator to generate plasma in the reaction tube. The vitreous layer of Si ₃ N ₄ and SiO ₂ formed on the quartz substrate is removed from the reaction vessel, and the deposited vitreous layer is polished to the thickness of the original quartz substrate. A lens assembly as shown in Figure 3 was obtained.

Although the present invention has been described above with reference to embodiments and specific examples, the present invention is not limited to these embodiments and specific examples, and various changes can be made based on the technical idea of the present invention.

For example, the slit-shaped opening 3 formed on the mask 2 has a shape that continues over the entire width from one edge of the transparent substrate 1 to the other edge, as shown in FIG. Alternatively, as shown in FIG. 7, it may have a window-like shape surrounded by a mask layer 2 on its entire circumference. Even in this case, the window-like opening 3
A gradient index lens assembly is created correspondingly.

Since the present invention has the above-described configuration, it can be mass-produced through a relatively simple manufacturing process, and it can also be used to focus light in a slit shape or in a matrix shape depending on the application. It can be focused and vice versa and is also suitable for use in light source systems with an elliptical emission angle in a plane perpendicular to the central axis of the beam.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a lens body in the middle of manufacture for explaining the method of manufacturing a gradient index lens body according to the present invention, and FIG. 2A is a perspective view of a lens body manufactured by the method shown in FIG. 1. Figure 2B is a graph showing the refractive index distribution of the lens body shown in Figure 2A.
The figure is a perspective view showing another example of the gradient index lens body according to the present invention, and FIG. 4 is a perspective view of a lens body showing an example of use in which two gradient index lens bodies shown in FIG. 3 are combined. FIG. 5 is a perspective view showing yet another example of the gradient index lens body, FIG. 6 is a sectional view of the lens body in the middle of manufacturing, showing the manufacturing process of the gradient index lens body shown in FIG. FIG. 7 is a perspective view of a lens body showing another example of masking in the method for manufacturing a lens body according to the present invention. In addition, in the symbols used in the drawings, 1,
1'... Transparent substrate, 2... Mask layer, 3... Opening, 4, 4'... Semi-cylindrical lens portion, 5, 5'...
...a lens body.

Claims (1)

[Claims] 1 A substantially semi-cylindrical gradient index lens portion extending substantially orthogonally to the thickness direction of the transparent substrate is provided in the transparent substrate, and a rectangular flat surface of the semi-cylindrical portion is located on the surface of the transparent substrate. The gradient index lens portion gradually changes as it moves away from the axis of a virtual cylinder of which the semi-cylindrical portion is one half in a direction orthogonal to this axis, and A gradient index lens body characterized by having a refractive index distribution that does not substantially change in a direction parallel to .