JPH11100233A - Optical element, optical element blank and their production and apparatus for production therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain optical elements in the atm. without using metal molds by melting a glass material of the same quality as the quality of the glass of a glass substrate worked to an optical mirror finished surface or the quality different therefrom, dropping the melt thereon onto the glass substrate and fusing the drops and imparting an optical function to the molten liquid drops. SOLUTION: The optical elements are formed by fusing the liquid drop glass 3 of the same quality as the quality of the glass substrate or the quality different therefrom onto the glass substrate worked to the optical mirror finished surface and are provided in plural pieces at a prescribed pitch. The apparatus for production has the following constitution: A heating plate 34 embedded with heaters 33 via a heat insulating plate 32 is disposed on a table 31 which may be positioned with a slide within an X-Y plane and a processing section 35 integrated therewith is disposed. A crucible 37 arranged in the central part of the heating furnace 36 held at the prescribed temp. is disposed above the processing section 35, by which the fused glass 38 is obtd. A liquid dropping section 41 adapted to allow the dropping of the liquid drops 40 of the molten glass from a nozzle 39 disposed at the bottom end of the crucible 37 is disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element used in an illumination optical system of a projector using a halogen lamp, a metal halide lamp or the like as a light source. In particular, in an illumination optical system, a microlens array is used as an optical element aiming at further improvement of light use efficiency and illumination uniformity (brightness, color unevenness). The present invention relates to an optical element represented by a microlens array, an optical element material, a method for manufacturing them, and an apparatus for manufacturing them.

[0002]

2. Description of the Related Art Conventionally, the following two methods are typical for producing the above-described optical element.

(1) A direct press method in which a molten glass lump is directly supplied into a mold and pressed. (2) A method of reheating a glass preform at a relatively low temperature using a mold having a predetermined optical function surface.

[0004] Each of them requires a molding die having an optical function surface, and is characterized in that the shape of the die function surface is transferred to a glass material.

However, the method (1) has an advantage that the number of mold surfaces to be used can be minimized and molding can be performed in the atmosphere, but also has a drawback that the glass to be supplied has a high temperature. That is, since the shrinkage caused by the temperature difference between the time when the molten glass is formed and the room temperature is reached is too large, it is difficult to transfer the mold shape precisely.

[0006] For this reason, the molded article has sinks, and it is complicated to perform secondary processing such as polishing to avoid the sinks. Also, if the mold is not opened at a relatively high temperature, there is a problem of mold releasability, such as cracking or a molded product not coming off the mold.

Accordingly, molding can be performed by necessarily shortening the cycle time. In addition, since the mold itself is exposed to high temperatures, the oxidation proceeds, and it is necessary to perform the mold maintenance on a regular basis. Therefore, as the number of the mold maintenance is increased, the shape of the optical functional surface may be gradually deteriorated. have.

On the other hand, in the method (2), press molding is generally performed in a chamber filled with an inert gas in order to protect an expensive molding die and stabilize mold release from glass. is there. Near the sag point of glass (within sag point + 100 ° C)
Can be formed at a relatively low temperature, and because of the low temperature, the mold releasability between the mold and the glass is good (the wettability of the glass is poor). And precise transferability can be obtained.

On the other hand, it has disadvantages such as the need for a large number of dies to shorten the cycle from the molding temperature to the normal temperature, and the restriction on the shape of the optical element material to be supplied.

FIG. 6 shows a molding method which can be considered with reference to the conventional method (2). The optical element material is placed inside a molding die composed of a lower mold 51, an upper mold 52 and a body mold 53. 54
And the entire molding die is heated, and when the optical element material reaches a deformable temperature above the yield point, molding is performed with pressure P.

In the upper and lower molds, a desired plurality of flat and concave shapes of the optical function surface are precisely processed on the surface in contact with the optical element material. In this case, the shape of the optical element material is advantageously flat because it is most easily obtained and inexpensive.

However, when gas is trapped in a plurality of enclosed spaces 55 formed by the concave surface of the lower mold and the plane of the optical element material, the untransferred portion is formed on the convex side of the molded optical element. Will not fulfill the function as the remaining optical element. Therefore, the current technology mainly uses the method (1), but has many problems as described above.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional method. First, an object is to obtain an optical element completely different from the conventional method, that is, without using a molding die. Alternatively, an optical element material can be obtained. The above optical element and optical element material can be manufactured in the atmosphere. Desirable shapes of desired optical elements and optical element materials can be selected. Further, if the above-mentioned optical element material is used in the conventional method (2), it is possible to solve problems such as improvement of transferability of molding. Further, an apparatus for manufacturing the optical element and the optical element material described above is provided to solve the problem.

[0014]

In order to solve the above-mentioned problems, an optical element according to the present invention is provided by preparing a glass substrate having both sides in the form of a flat plate having an optical mirror surface, and melting a glass material having the same composition or another composition. An amount of a predetermined amount of liquid necessary for forming an optical function surface is dropped on the glass substrate, and both the glass substrate and the droplet glass are welded so as to have no optical defects to form an optical element. This is an optical element obtained by means using molten glass droplets for the optical function surface without the need for a mold not seen in the conventional example.

A method for manufacturing an optical element according to the present invention will be described as means for solving the problems of the optical element. A glass substrate for forming a part of an optical element is prepared by processing it into an optical mirror surface, a glass material is melted separately from the glass substrate, and a predetermined volume of molten glass is dropped on the glass substrate, and the entire glass substrate is melted. Is cooled and solidified to obtain an optical element. The temperature of the molten droplet and the relative temperature of the glass substrate are important. In the case of the present invention, at least a means for heating the glass substrate to a predetermined temperature is used to manufacture an optical element free from optical defects.

The optical element material according to the present invention is a conventional example (2).
The basic idea is the same as that of the above-described method for manufacturing an optical element. However, the difference is that the droplet is welded to the glass substrate and temporarily fixed by lowering the heating temperature of the glass substrate or by performing the heating at room temperature. The dropped glass is used as a means for solving the problem by obtaining a shape closer to a spherical shape. Therefore, this is a method for producing an optical element material without trapping gas during extrusion.

An apparatus for manufacturing an optical element and an optical element material according to the present invention comprises a processing section provided with a heating plate and capable of positioning with a slide, a crucible having a desired glass material charged above the processing section, and a glass material. A heater for heating the
A manufacturing apparatus is provided which includes a droplet portion capable of supplying a molten droplet from a lower end nozzle of the crucible, and makes a distance between the processing portion and the droplet portion variable.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) The optical element of the present invention is an optical element 1 having a lens array having a flat-convex shape as shown in the perspective view of FIG. A glass substrate made of barium borosilicate was cut into a size of 20 mm square, and both surfaces were mirror-polished using a conventional optical polishing method to produce a glass substrate 2 having a thickness of 2 mm.

Nine droplet glass pieces 3 having the same composition as the glass substrate are provided by a manufacturing method described later. The surface of the droplet glass was a free mirror surface. No defects, such as bubbles or cracks, that hinder the optical function were found at the interface between the glass substrate and the droplet glass. The shape of the droplet glass has a free-form surface, but the center of the droplet glass was evaluated with a Fizeau interferometer. The radius of curvature was 1.9 mm, and all nine particles showed a substantially constant shape. It was confirmed that it was sufficient for use. The shape formed by the droplet glass depends on an appropriate design, and may be designed to obtain an optimum focal length.

FIG. 2 illustrates the principle of an illumination optical system of a liquid crystal projector using the above-described optical element.
A parallel light beam emitted from the luminous body S of the lamp 21 having a light source of halogen, metal halide, or the like passes through the first lens 23 of the first lens array 22 and passes through the second lens array 24 of the second lens array 24.
The light is focused on the main plane of the lens 25 to form a real image of the luminous body S, that is, a luminous body image S ′. Thereafter, the light that has passed through the second lens array is uniformly applied to the liquid crystal panel P ′.

Therefore, the first lens array acts to form a real image of the illuminant by being condensed on the main plane of the second lens array, and the second lens array acts as a light beam entering the opening of the first lens array. Is enlarged in accordance with a predetermined magnification to form light for illuminating a liquid crystal panel which is an illuminated area.

Therefore, the characteristics of the present lens array are determined by the shape of each lens, that is, how to keep the focal length constant.

(Embodiment 2) A method for manufacturing an optical element and an optical element material according to the present invention will be described with reference to a manufacturing apparatus shown in FIG. A heater 33 is placed on a table 31 capable of sliding and positioning in an XY plane via a heat insulating plate 32.
Is provided, and a crucible 37 disposed at the center of a heating furnace 36 maintained at a predetermined temperature is provided above the processing portion 35. And a molten glass 38 is obtained. A drop portion 41 is provided at which a melted glass droplet 40 is allowed to fall from a nozzle 39 provided at the lower end of the crucible 37. The relative position (height) between the processing portion 35 and the drop portion is shown in FIG. This manufacturing apparatus has a configuration that can be arbitrarily set and fixed at + Z and -Z in the direction of the arrow.

The temperature control of the heating plate 34 and the heating furnace 36 is performed by using a normal thermocouple (not shown).
The adjustment of the relative distance between the liquid droplet 5 and the liquid drop portion 41 is performed by moving the entire table 31 (not shown) up or down, or by attaching the whole liquid drop portion to an arm that moves up and down.

A borosilicate glass material (glass transition point: 501 ° C., sag point: 5) having a relatively low melting point and both surfaces polished to an optical mirror surface on a heating plate 34 heated to 500 ° C.
(49 ° C.). The thickness of the substrate was 2 mm.

After mounting, the glass substrate is held for a period of time until the temperature of the glass substrate becomes substantially the same as the set temperature of the heating plate.
A 0 mg droplet 40 was dropped on the glass substrate 2 at a predetermined pitch. The drop timing was about 4 seconds.

The distance between the glass substrate 2 and the droplet 40 is 1
00 mm. In the present embodiment, the drop pitch of the droplets 40 is 7.5 mm. The optical element 1 obtained by completing the droplets and cooling is as shown in FIG.

In this embodiment, the temperature of the glass substrate is controlled to the glass transition point. The reason is, of course, that the higher the substrate temperature, the better the adhesion to droplets, but the more the shape of the entire glass substrate is not changed.
The drop distance is determined by the degree to which the droplet is cooled during the drop, and the shorter the droplet, the better the adhesion.

(Embodiment 3) The glass substrate 2 is placed with the set temperature of the heating plate 34 at room temperature, the same glass material as in Embodiment 1 is melted at 1250 ° C., and the droplet glass 3 is dropped. . Even if the glass substrate was welded to the droplet glass, or even if the glass substrate was welded, cracks occurred in the glass substrate and did not become an optical element. The difference between the thermal expansion of the two materials and the rapid thermal shrinkage of the glass droplet, which is a high temperature glass substrate, can be considered. In the present embodiment, the former is considered to be the reason. However, it is needless to say that matching the thermal expansions of the two is desirable for obtaining an optical element.

(Embodiment 4) Pyrex glass (softening point: 820) which is borosilicate glass as a material of the substrate 34
C., glass transition point: 560.degree. C., sag point: 653.degree. C.) and having a sagging point higher than that of the drop glass, and a glass substrate 2 was prepared by processing both surfaces of the substrate into optical mirror surfaces. Keep the temperature of the glass substrate at room temperature and sufficiently lower than the glass transition point.
0 ° C. The molten glass material is the same as in the first to third embodiments.

When the falling distance is 100 mm, about 60 mg
When the droplet 40 was dropped, the droplet glass 3 was welded in a substantially spherical shape with a radius of curvature of about 1.7 mm at both the normal temperature and 300 ° C. of the glass substrate 2.

No defects such as cracks and bubbles were observed at the interface between the glass substrate and the droplet glass. However, it is preferable to heat the glass substrate to some extent because the glass substrate is more excellent in welding force. .

However, it has been confirmed that the desired optical element, which cannot be directly used, is used as a molding material of the above-mentioned conventional example (2) as an optical element material described later. Therefore, the optical element material 54 shown in the cross-sectional view of FIG. 4 in which the glass substrate and the droplet glass were formed of different materials was obtained.

Embodiment 5 Pyrex glass, which is a borosilicate glass, was selected as a substrate material, and both surfaces of the substrate were processed into optical mirror surfaces to prepare a glass substrate 2. The molten glass material is the same as in the first to fourth embodiments.
Set the temperature of the glass substrate to 560 ° C and set the drop distance to 10
Assuming 0 mm, the molten glass at 1250 ° C. was dropped about 60 mg of the droplets 40, and they were welded to each other without defects at the interface and without generation of cracks on the substrate. Thus, the optical element 1 having a smaller central curvature than that of the optical element 2 and a larger central curvature than the third and fourth embodiments could be obtained.

(Embodiment 6) This is a method of molding an optical element by the conventional method (2) using the optical element material obtained in Embodiment 4, which will be described with reference to FIG. The optical element material 54 is put into the lower mold 51, the upper mold 52, and the body mold 53. The optical surface of the upper mold has a flat surface, and the optical surface of the lower mold has nine concave shapes (radius of curvature of 13.5 mm) at a predetermined pitch. When the entire mold was heated to 580 ° C., that is, press-molding was performed under conditions that considered the thermal characteristics of the droplet glass, it was possible to obtain an optical element in which the mold shape was precisely transferred. The radius of curvature of the droplet glass of the optical element material is sufficiently smaller than the concave shape of the lower mold, that is, by leaving the amount of pressing deformation on the droplet glass, without forming a closed space as in the conventional example, the gas An optical element that achieved precise transferability was obtained because of the configuration in which no confinement occurs.

[0036]

As described above, the optical element of the present invention can be obtained without the need for a molding die, and can significantly reduce the lead time for producing the die. In addition, the optical element material can be obtained only by changing the manufacturing conditions for obtaining the optical element, and the conventional defects at the time of molding can be removed, and a molded article having good transferability can be realized. Further, according to the manufacturing method, it is possible to obtain an optical element having an arbitrary optical function according to a change in the temperature condition and the drop distance of the glass substrate and the droplet glass. Further, the manufacturing apparatus can be realized with a simple configuration, and has high industrial value.

[Brief description of the drawings]

FIG. 1 is a three-dimensional perspective view showing an optical element of the present invention.

FIG. 2 is a principle diagram illustrating an illumination optical system using an optical element according to the present invention.

FIG. 3 is a schematic sectional view illustrating a manufacturing method and a manufacturing apparatus of the present invention.

FIG. 4 is a sectional view of an optical element material obtained by the present invention.

FIG. 5 is a cross-sectional view illustrating a conventional molding method performed using the optical element material of the present invention.

FIG. 6 is a cross-sectional view illustrating a conventional molding method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical element 2 glass substrate 3 droplet glass 21 lamp 22 first lens array 24 second lens array 31 table 32 heat insulating plate 33 heater 34 heating plate 35 processing section 36 heating furnace 37 crucible 38 molten glass 39 nozzle 40 droplet 41 liquid Drop part 51 Lower mold 52 Upper mold 53 Body mold 54 Optical element material 55 Enclosed space S 'Light emitter image P' Liquid crystal panel surface

 ──────────────────────────────────────────────────の Continued from the front page (72) Inventor Masaaki Sunohara 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. A glass substrate processed into an optical mirror surface,
An optical element, characterized in that a glass material of the same or a different kind as the glass is melted and dropped to form a fusion, and the melted droplet has an optical function. 2. The optical element according to claim 1, wherein a portion corresponding to the molten droplet is shaped into a desired shape and has an optical function. 3. The optical element according to claim 1, wherein said molten liquid droplets are arranged in plural at a predetermined pitch on said glass substrate. 4. A step of preparing a glass substrate by processing it into an optical mirror surface, a step of heating the glass substrate to a predetermined temperature, and a step of melting a glass material of the same or different quality as the glass substrate and a predetermined amount on the glass substrate. An optical function, comprising: a step of dropping, and a step of cooling and solidifying the entire glass material, and optically welding the glass substrate and the dropped glass material to provide an optical function effect. Device manufacturing method. 5. The method for manufacturing an optical element according to claim 2, wherein the molten liquid droplets are arranged at a predetermined pitch on the glass substrate. 6. A step of preparing a glass substrate by processing it into an optical mirror surface, melting and dropping a homogeneous or dissimilar glass material for providing an optical function on the glass substrate, An optical element material for molding an optical element, wherein a droplet and a droplet are temporarily fixed. 7. The optical element material according to claim 6, wherein a plurality of the molten droplets are arranged at a predetermined pitch on the glass substrate. 8. A step of preparing a glass substrate by processing it into an optical mirror surface, wherein the same or different glass material for imparting an optical function effect is melted and dropped on the glass substrate, and the glass substrate and the molten droplet are melted. And a step of temporarily fixing the molten liquid droplets, wherein the molten liquid droplets have a shape with a pressing deformation amount remaining. 9. A processing section in which a heat insulating plate, a heating plate, and a glass substrate forming a part of an optical element can be mounted on a table so that the table can be slid and positioned in an XY plane. A crucible charged with a desired glass material above the processing portion, a heater for heating the glass material to a melting temperature, and a droplet portion configured to supply molten droplets from a lower end nozzle of the crucible. An apparatus for manufacturing an optical element and an optical element material, wherein a relative distance between the slide section and the liquid drop section is variable.