JP2003329817A - Prism and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small glass prism capable of corresponding to having high precision and high strength and capable of corresponding to large-capacity optical recording and high-speed optical communication and a method for producing a prism with high production efficiency. <P>SOLUTION: This prism is made of transparent glass, surfaces of corner parts 1d, 1e and 1f linking with incident light surfaces 1a, 1b and 1c are a fire-working surface, and a compressed stress layer 2 having a stress value of 0.1 to 10 MPa is formed on the surfaces of the corner parts 1d, 1e and 1f. In this method for producing the prism, a glass preform material having a predetermined size ratio, wherein the Ra value of a surface that serves as a light incidence surface after forming is less than the value corresponding to #170, is gripped by a feed means and fed into a furnace, where the glass preform material is heated to a temperature such that the lowest viscosity is not less than 10<SP>4</SP>Pa.s but less than 10<SP>6</SP>Pa.s, the lower portion being stretch- formed by a stretch means and cut into long bodies having a desired size and an incident light surface whose surface Ra value is not more than 1/4 of incident light wavelength, and the long bodies are then cut into pieces of desired length. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass prism and a method for manufacturing the prism.

[0002]

2. Description of the Related Art In recent years, due to the development of optical recording and optical communication technologies, optical heads for optical disk devices, optical switches for optical communication, etc., are transparent, have a low expansion coefficient, and are required to process optical signals.
Many types of small prisms are used, which have advantages such as mass productivity and appropriate polishability.

The prism is one that totally reflects the light incident from the first surface on the second surface and then emits it from the third surface, or a prism that totally reflects the light incident from the first surface on the second surface and then on the third surface. There is one that is totally reflected and emitted from the first surface. In order to accurately exhibit the function of operating such an optical signal, the mutual angles of the light-receiving surfaces on which the light signals such as the first surface to the third surface hit are accurately formed, and The surface needs to be a mirror surface having high surface accuracy.

Generally, in order to meet the above requirements, a glass prism is prepared by preparing a roughly prism-shaped glass processed material that is roughly formed with a machining allowance, and precisely illuminates each light receiving surface one by one. It is manufactured by polishing after grinding and then finishing it into a mirror surface with a required high degree of mutual angle accuracy and high surface accuracy.

Further, as in Patent Document 1, it has been proposed to manufacture a glass prism by press molding.

[0006]

[Patent Document 1] Japanese Unexamined Patent Publication No. 10-1321 (No. 3-4)
Page, Fig. 1-5)

[0007]

In recent years, the demand for optical heads for optical disc devices and optical switches for optical communications for such applications has been great due to the progress of increasing the capacity of optical recording and increasing the speed of optical communication. It has become to. For this reason, inexpensive resin prisms are often used, but resin prisms may not be used in terms of reliability such as temperature dependence of optical characteristics and moisture resistance.

When the desired glass prism is manufactured by the conventional manufacturing method as described above, the light-receiving surfaces are precisely ground one by one and then polished, and the respective light-receiving surfaces are required to have a high angle accuracy. Since it is necessary to finish the surface roughness and the flatness, there is a problem that the number of processing steps is large and complicated, the yield rate is not increased, and the cost is increased.

Further, the area of the cross section orthogonal to each light-illuminating surface is 1
Letting D be the circumscribed circle diameter of the cross section orthogonal to each light-incident surface and a small prism of 00 mm ² or less, and L be the length dimension parallel to the light-incident surface, the relation of L ≧ 1.5D / 2 ^0.5 When manufacturing a prism having an elongated shape such that
It is difficult to handle glass processing materials, it is damaged during work such as polishing, the illuminated surfaces of each other cannot be finished with the required high angular accuracy, and the illuminated surfaces are finished as mirror surfaces with uniform surface precision. Not only is it difficult to do, but the finished light surface may be damaged during processing and the subsequent cleaning process, and the corners connected to the light surface may be damaged during the polishing process. If cracks occur, the bending strength decreases, and especially when handling elongated prisms, the processed material often breaks, yield decreases, and there is also the problem that production efficiency decreases and it is not suitable for mass production. .

In order to address the above problems, for example, in Patent Document 1, a glass rod is stretched to obtain a rod-shaped glass material, and the glass material is reheated and press-molded to form a polyhedral elongated molded body. After that, it has been proposed to take a large number of prisms of a predetermined length. However, there is a problem that it is difficult to control the molding die that determines the quality of the illuminated surface, and if the molding die has a short life, the cost does not decrease so much.

The present invention solves the above-mentioned problems, and a small glass prism having high precision and high strength, which can be used for large-capacity optical recording and high-speed large-capacity optical communication applications, and mass production with high production efficiency. It is an object of the present invention to provide a method for manufacturing a prism suitable for.

[0012]

The prism according to the present invention is made of transparent glass, and the surface of the corner portion connected to the light-exposed surface on which light is applied is a fire-making surface, and stress is applied to the surface of the corner portion. A compression stress layer having a value of 0.1 to 10 MPa is formed.

In the present invention, the corner portion connected to the light receiving surface on which light such as an optical signal strikes means a line-shaped corner portion where the surface through which the incident light transmits and the surface through which the incident light reflects are connected. Therefore, the prism of the present invention is preferably heated and stretched so that the cross section of the corner portion is substantially R-shaped, and the surface thereof is a fire-polished surface or the like formed by hot working. It is made up of faces. The fired surface composed of such a free surface has substantially no defects such as surface cracks, and has a high strength close to the original strength of glass.

When the stress value of the compressive stress layer formed on the surface of the corner portion is less than 0.1 MPa, the corner portion is not sufficiently strengthened and the strength is low. On the other hand, when the stress value of the compressive stress layer exceeds 10 MPa, not only the optical characteristics such as the refractive index are adversely affected, but also when broken during handling, the glass pieces scatter and adversely affect the surroundings. It is important that the compressive stress layer formed on the surface of the corner has a stress value of 0.1 to 10 MPa.

Further, the prism of the present invention is characterized in that the area of a cross section orthogonal to each light incident surface is 100 mm ² or less.

The area of the cross section orthogonal to each light-illuminating surface is 100 m.
The is m ² or less, in the case of right-angle prism is a right triangle, 100 mm area of the cross section of such an isosceles right triangle ²
It means a small prism as follows.

Further, in the prism of the present invention, when a circumscribed circle diameter of a cross section orthogonal to each light incident surface is D and a length dimension parallel to the light incident surface is L, L ≧ 1.5D / 2 ^0.5 Characterized by satisfying a relationship.

The circumscribed circle diameter D means the diameter of the circumscribed circle circumscribing the cross section of a right-angled triangle, a right-angled isosceles triangle, or the like in the case of a right-angled prism, and L ≧ 1.5D / 2.
^Satisfying the relationship of ^0.5 means a long prism whose length dimension L is 1.06 times or more the circumscribed circle diameter D.

Further, the prism of the present invention is characterized in that an optical film is formed on the light receiving surface.

As the optical film formed on the light-incident surface, a filter film, a polarizing film such as a beam splitter, an antireflection film, a density filter film, a metal mirror film, or a composite film combining these can be used.

The method for producing a prism according to the present invention is applied to a prism which is made of transparent glass and has a surface roughness Ra of less than # 170 and which is obtained after the molding. A glass base material having a dimensional ratio in a predetermined range is produced, the glass base material is held by a holding part of a feeding means, and the glass base material is fed into a heating furnace so that the minimum viscosity of the glass base material is 10 ⁴ Pa. 10 ⁶ Pa for s or more
The glass base material is heated to a predetermined temperature of less than s, the lower part of the glass base material is stretch-formed by a tensile means, and cut into a predetermined length to obtain a size and surface roughness in a desired range in a shape substantially similar to the glass base material. The present invention is characterized in that a long body having an equivalent surface whose Ra value is ¼ or less of the wavelength of incident light is obtained, and the long body is cut into a desired length.

When the Ra value of the surface roughness of the glass base material surface which becomes the light receiving surface after molding becomes rougher than that corresponding to # 170, the Ra value of the surface roughness of the light receiving surface is 1/4 or less of the wavelength of the incident light. It becomes impossible to obtain a long body. The surface roughness of the surface which becomes the light-incident surface after molding of the glass base material used in the present invention includes:
It is important to be finer than 170. Also, # 1
The Ra value of the surface roughness of 70 is, for example, in the case of borosilicate optical glass, the Ra value of the surface roughness of # 170 is 1 μm to 3 μm, and is often about 2 μm. .

When the minimum viscosity of the glass base material in the heating furnace is less than 10 ⁴ Pa · s, the glass base material during the stretch forming bends and the long body of a predetermined size cannot be pulled straight and bends. I will end up. In addition, the shape of the elongated body obtained by stretch molding is greatly deformed by the surface tension, and an elongated body having a shape substantially similar to the glass base material cannot be obtained. On the other hand, the minimum viscosity is 10
^{At 6} Pa · s or more, due to the rheological behavior of the glass tube during stretch molding, an extremely large force is required for stretching when trying to increase the pulling speed, which not only makes it difficult to manufacture the corresponding molding equipment, The glass base material is often broken due to the tensile stress during stretch forming. That is, the minimum viscosity is 10
^{If it is 6} Pa · s or more, the tensile speed cannot be made higher than a certain value, and the molding speed becomes very slow.
In the present invention, the minimum viscosity of the glass base material in the heating furnace is 10 ⁴
It is important to be in the range of Pa · s or more and less than 10 ⁶ Pa · s.

Furthermore, if the Ra of the surface roughness of the light receiving surface exceeds 1/4 of the wavelength of the incident light, the light is diffusely reflected, so that large-capacity optical recording and high-speed large-capacity optical communication are performed. It becomes a prism that cannot be used for such purposes. It is important for the elongated body obtained by stretch molding in the present invention to have a light-applied surface having a Ra value of surface roughness of ¼ or less of the wavelength of incident light.

Further, the method for producing a prism of the present invention is characterized in that the light-incident surface of the elongated body obtained by stretch molding is polished.

The illuminated surface of the elongated body obtained by stretch molding may be finished by polishing. By polishing the light-illuminating surface of the elongated body obtained by stretch molding, the angle accuracy of higher accuracy, surface roughness, by just slightly polishing the light-illuminating surface of each other,
It becomes possible to finish to flatness.

[0027]

The prism of the present invention is made of transparent glass,
The surface of the corner portion connected to the light-exposed surface is a fired surface, and the surface of the corner portion has a stress value of 0.1 to 0.1.
Since a compressive stress layer of 10 MPa is formed, the corners where chipping is likely to occur are physically strengthened, glass prisms are less likely to break, and glass fragments are less likely to occur, so that the light receiving surface can be damaged. Less and easier to handle.

Further, since the prism of the present invention has an area of a cross section perpendicular to each light incident surface of 100 mm ² or less, it is possible to provide a small prism having a reinforced corner portion.

Further, in the prism of the present invention, when the circumscribed circle diameter of the cross section orthogonal to each light receiving surface is D and the length dimension parallel to the light receiving surface is L, L ≧ 1.5D / 2 ^0.5 Since the relationship is satisfied, it is possible to provide an elongated prism in which the corner portion is strengthened and is difficult to break.

Further, since the prism of the present invention is formed by forming an optical film on the light receiving surface, a filter film, a polarizing film such as a beam splitter, an antireflection film, a density filter film, a metal mirror film, or a combination thereof. By forming the composite film, it is possible to provide various prisms having a reinforced corner portion which can be used for high-capacity optical recording and high-speed high-capacity optical communication.

The method for producing a prism according to the present invention is applied to a prism which is made of transparent glass, has a surface roughness Ra value of less than # 170 and which is obtained as a light-incident surface after the molding. A glass base material having a dimensional ratio in a predetermined range is produced, the glass base material is held by a holding part of a feeding means, and the glass base material is fed into a heating furnace so that the minimum viscosity of the glass base material is 10 ⁴ Pa. 10 ⁶ Pa for s or more
The glass base material is heated to a predetermined temperature of less than s, the lower part of the glass base material is stretch-formed by a tensile means, and cut into a predetermined length to obtain a size and surface roughness in a desired range in a shape substantially similar to the glass base material. For obtaining large-capacity optical recording and high-speed large-capacity optical communication since a long body having an equivalent surface whose Ra value is ¼ or less of the wavelength of incident light is obtained and the long body is cut into a desired length. It is possible to efficiently manufacture a prism having a reinforced corner portion that is compatible with the above.

Further, in the method for producing a prism of the present invention, since the light-illuminating surface of the elongated body obtained by stretch molding is polished, the Ra values of the dimensions and surface roughness in the desired range obtained by stretch molding are large. By slightly polishing the light-receiving surface of a long body having a light-receiving surface that is 1/4 or less of the wavelength of the incident light, it is possible to achieve even higher accuracy in angle accuracy, surface roughness, and flatness. Become.
Since the light-illuminating surface of the elongated body is only slightly polished, the polishing work is short, and since the elongated body is polished, it can be highly efficiently polished when converted into one prism.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a prism of the present invention, in which 1 is a prism, 1a, 1b, 1c are light-incident surfaces on which light is incident, and 1d, 1e, 1f are corner portions. To
Reference numerals 2 respectively indicate compressive stress layers.

First, the prism of the present invention will be described.

As shown in FIG. 1, the prism 1 of the present invention is made of transparent optical glass, for example, BK-7, is a right-angled prism having a right-angled isosceles triangle shape, and is exposed to light such as an optical signal. The surfaces of the corner portions 1d, 1e, 1f having a substantially R-shaped cross section connecting the light surfaces 1a, 1b, 1c are fire-polished surfaces, the Ra value of the surface roughness is 30 nm, and the corner portions 1d, 1e are also formed. As shown in an enlarged view, a compressive stress layer 2 having a stress value of about 3 MPa is formed on the surface of 1f to be physically reinforced. Also, the light side 1
The Ra values of the surface roughness of a, 1b, and 1c are also 30 nm, the flatness is better than ¼ of the wavelength λ of the incident light, and the light can be transmitted or reflected without being scattered. The angle θ1 formed by the surface 1b and the light receiving surface 1c is 90 ° ± 1
5 ″, and an angle θ2 formed by the light receiving surface 1a and the light receiving surface 1b.
Is formed with a very high accuracy of 45 ° ± 15 ″.

Further, the prism 1 is a small prism having a side of 0.5 mm and a circumscribed circle diameter D of 0.7 mm, and a length L parallel to the light receiving surfaces 1a, 1b, 1c is 2 mm. It has an elongated shape that satisfies the relationship of L ≧ 1.5D / 2 ^0.5 .

When the three-point bending test of the prism 1 was evaluated, the bending stress value was 120 MPa, which was about 2.5 as compared with the conventional prism made by polishing having the same dimensions.
It was double the value.

A prism 3 according to another embodiment is shown in FIG.
As shown in (B), the wavelength is 1310 nm on the light receiving surface 3a.
The filter film 4 which transmits 95% or more of the above light and totally reflects the light of 1550 nm without being transmitted is used for an optical switch or the like.

Further, as shown in FIG. 1C, prisms 5 and 6 according to another embodiment are provided with opposing light-receiving surfaces 5a,
A polarizing film 7 having a beam splitter function for processing P-polarized light and S-polarized light is formed between 6a and is used as an optical system for an optical head of an optical disk device.

Next, a method of manufacturing the prism according to the present invention will be described.

2A and 2B are views for explaining the method of manufacturing a prism of the present invention. FIG. 2A is a glass base material, FIG. 2B is a drawing step, and FIG. It is explanatory drawing which obtains the prism 1.

As shown in FIG. 2A, the glass base material 11 is made of, for example, BK-7, which is a borosilicate optical glass having a minimum viscosity of 10 ⁴ Pa · s and a temperature of about 850 ° C. Surfaces 11a, 11b, 11c that become the light receiving surface after molding
Have. The cross section of the glass base material 11 is an isosceles right triangle whose base is the surface 11a.
Each side length of c is about 10 to 70 mm, and a glass base material 11 having an angle between the surfaces 11b and 11c of 90 ° ± 15 ″ is prepared. The surface roughness of the surfaces 11a, 11b, and 11c that correspond to # 600 is equal to or less than # 170, which corresponds to an Ra value of about 2 μm, and an Ra value of 0.3 μm to 0.5 μm.
m, for example, about 0.4 μm.

As shown in FIG. 2B, the apparatus for stretch-molding the glass base material 11 has, as a basic structural part, a feeding means 12 having a holding part 12a for holding the glass base material 11 and a glass base material. Material 11 has a minimum viscosity of 10 ⁴ Pa
a heating furnace 14 for heating to a predetermined temperature of s or more and less than 10 ⁶ Pa · s, and a pulling means 15 having a pair of rollers 15a and 15b for stretching and forming the lower part of the glass base material 11.
The elongated body 1 is composed of a cutting means 16 for cutting the drawn glass and has a size in a desired range which is substantially similar to the base material 11.
7 is to be molded.

The heating furnace 14 is, as shown in FIG.
A heater 14a for heating the glass base material 11 to a predetermined temperature at which the minimum viscosity is 10 ⁴ Pa · s or more and less than 10 ⁶ Pa · s, and a thermocouple 14b for measuring the furnace temperature.
And a power controller 14d for inputting an electric signal from the thermocouple 14b to the temperature controller 14c and outputting it when the temperature is lower than the target temperature. The power controller 14d stabilizes the glass base material 11 at a predetermined temperature at which the minimum viscosity is 10 ⁴ Pa · s or more and less than 10 ⁶ Pa · s.

An example of the method of molding a prism according to the present invention is performed from the glass base material 11 to the prism 1 by using the above molding apparatus.
The case of manufacturing is explained.

First, as shown in FIG. 2B, the glass base material 11 is held by the holding portion 12a of the feeding means 12 and fed into the heating furnace 14 at a constant speed. At this time, the feeding speed of the glass base material 11 at the time of stretch forming is measured, and a signal of the feeding speed is input to a controller (not shown) to operate the feeding means, so that the feeding speed of the glass base material 11 can be accurately adjusted. It can be controlled to be constant.

Next, in the heating furnace 14, the glass base material 11
About 8 which is the temperature at which the minimum viscosity is 10 ⁵ Pa · s.
Heat to 00 ° C. When the electric signal of the thermocouple 14b for measuring the temperature in the furnace is input to the temperature controller 14c and the temperature in the furnace measured by the thermocouple 14b is lower than the target of about 800 ° C, the power controller 14d operates. , Heater 14
The output of a is increased and the temperature in the heating furnace 14 is stabilized so that the minimum viscosity of the glass base material 11 is exactly 10 ⁵ Pa · s. On the other hand, when the furnace temperature measured by the thermocouple 14b is higher than the target temperature of about 800 ° C, the heater 14a
Is reduced to stabilize the temperature in the heating furnace 14 so that the minimum viscosity of the glass base material 11 is exactly 10 ⁵ Pa · s. When the temperature inside the heating furnace 4 is higher than the target temperature of about 800 ° C., the temperature inside the heating furnace 14 can be easily lowered by reducing the output of the heater 14a.

Next, the glass which extends below the glass base material 11 in the heating furnace 4 and has a substantially predetermined size and which is substantially solidified is sandwiched between the pair of rollers 15a and 15b and pressed so that a sufficient frictional force acts. In this state, the glass base material is stretched by pulling at a constant pulling speed of several hundred to several thousand times the feeding speed of the glass base material. Finally, the drawn glass is cut by the cutting means 16 to obtain a long body 17 having a shape substantially similar to the glass base material 11.

Next, as shown in FIG. 2 (C), the high-precision long body 17 is cut by a precision cutting device so that the total length L becomes 2 mm, and the prism 1 is manufactured.
At this time, if a plurality of elongated bodies 17 are aligned or three-dimensionally arranged and cut at the same time, the work efficiency becomes high.

As described above, according to the present invention, the elongated body 17 can be stably formed with high accuracy by heating the glass base material 11 made of optical glass and performing stretch forming with low viscosity. The prism 1 according to the present invention could be manufactured with a very small number of steps.

In the embodiment of the invention described above, the prism made of optical glass is shown, but it may be made of general industrial glass, and if heat resistance is required, transparent crystallized glass or the like is used. You may.

Further, in the embodiment of the present invention described above, the right angle prism is shown, but the present invention is not limited to this, and an acute angle, an obtuse angle triangular prism, a trapezoid, a quadrangular prism including a rhombus, other polygonal prisms, and some curved lines. It is also applicable to various prisms such as a prism having a special shape.

[0053]

EFFECTS OF THE INVENTION According to the prism of the present invention, the surface of the corner portion, which is made of transparent glass and is continuous with the light-incident surface on which the light strikes, is a fired surface, and the stress value on the surface of the corner portion is high. Since a compressive stress layer of 0.1 to 10 MPa is formed, the corners where chipping is likely to occur are physically strengthened, and it is easy to handle without damaging the illuminated surface with glass fragments, etc. It is possible to provide an inexpensive prism made of glass having high accuracy and high strength, which can be applied to optical recording and high-speed large-capacity optical communication applications.

Also, since the prism of the present invention has an area of a cross section perpendicular to each light-illuminating surface of 100 mm ² or less, it is possible to provide an inexpensive small prism having a reinforced corner portion.

Further, in the prism of the present invention, when the circumscribed circle diameter of the cross section orthogonal to each light incident surface is D and the length dimension parallel to the light incident surface is L, L ≧ 1.5D / 2 ^0.5 Since the relationship is satisfied, it is possible to provide an elongated prism having a corner portion that is hard to break and is suitable for an optical device or the like that uses an arrayed optical fiber to process optical signals in parallel.

Further, since the prism of the present invention is formed by forming an optical film on the light receiving surface, a filter film, a polarizing film such as a beam splitter, an antireflection film, a density filter film, a metal mirror film, or a combination thereof. By forming the composite film, it is possible to provide various prisms that can be used for large-capacity optical recording and high-speed large-capacity optical communication applications and can be suitable for various optical devices with reinforced corner portions.

According to the method of manufacturing a prism of the present invention, the surface roughness Ra value of the surface made of transparent glass, which becomes the illuminated surface after molding, is less than # 170, and the prism obtained after molding is On the other hand, a glass base material having a dimensional ratio in a predetermined range is produced, the glass base material is held by a holding part of a feeding means, and the glass base material is fed into a heating furnace, whereby the minimum viscosity of the glass base material is 10 ⁴ 1 above Pa · s
0 less than ⁶ Pa · s and heated to a predetermined temperature, the size of the desired range with a glass base material and shape similar by to stretch forming by pulling means to the lower of the glass preform is cut to a predetermined length and Since a Ra having a surface roughness Ra value of 1/4 or less of the wavelength of incident light is obtained and the elongated body is cut into a desired length, high-capacity optical recording and high-speed optical recording can be achieved. It is possible to efficiently manufacture a prism having a reinforced corner portion that can be used for capacitive optical communication applications, and it is possible to manufacture an optical device with high efficiency and at low cost.

Further, in the method of manufacturing the prism of the present invention, since the light-emission surface of the elongated body is polished, the light-emission surface of each of them is finished with high accuracy of angle and surface which cannot be obtained by stretch molding. It is also possible to manufacture a prism that can be used for high-capacity optical recording and high-speed, high-capacity optical communication applications.

As described above, according to the prism and the method for manufacturing the prism of the present invention, a large number of prisms having high dimensional accuracy can be obtained from one glass base material, and the obtained prisms also have high strength. , A large number of highly reliable prisms can be manufactured in a short period of time and at low cost, which makes it possible to manufacture optical devices using prisms with high efficiency and at low cost. Is played.

[Brief description of drawings]

1A and 1B are explanatory views of a prism of the present invention, in which FIG. 1A is an explanatory view of a right-angled isosceles triangular right-angled prism, FIG. 1B is an explanatory view of a right-angled prism having a filter film formed thereon, and FIG. Explanatory drawing of the right-angled prism which opposes on both sides of the polarizing film which has a beam splitter function.

FIG. 2 is an explanatory view of the prism manufacturing method of the present invention,
(A) is an explanatory view of a glass base material, (B) is an explanatory view of a process of stretching a glass base material to obtain a long body, and (C) is an explanatory view of obtaining a plurality of prisms from the long body.

[Explanation of symbols]

1, 3, 5, 6 prism 1a, 1b, 1c, 3a, 5a, 6a Current surface 1d, 1e, 1f Corner part 2 Compressive stress layer 4 filter membrane 7 Polarizing film 11 Glass base material 11a, 11b, 11c Surface that becomes the light receiving surface 12 Delivery means 12a gripping part 14 heating furnace 14a heater 14b thermocouple 14c Temperature controller 14d Power controller 15 Pulling means 15a, 15b roller 16 cutting means 17 Long body

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsutaka Nakae             2-7-1, Harashira, Otsu City, Shiga Prefecture             Air Glass Co., Ltd. F-term (reference) 2H042 CA01 CA10 CA15

Claims (6)

[Claims] 1. A compressive stress layer, which is made of transparent glass, has a fired surface on the surface of a corner portion connected to the light-exposed surface, and has a stress value of 0.1 to 10 MPa on the surface of the corner portion. A prism characterized by being formed. 2. The area of a cross section orthogonal to each light incident surface is 100.
The prism according to claim 1, wherein the prism has a size of not more than mm ² . 3. When a circumscribed circle diameter of a cross section orthogonal to each light incident surface is D and a length dimension parallel to the light incident surface is L, L ≧
The prism according to claim 1 or 2, wherein the relationship of 1.5D / 2 ^0.5 is satisfied. 4. The prism according to claim 1, wherein an optical film is formed on the light surface. 5. A glass which is made of transparent glass and has a surface roughness Ra of less than # 170 on the surface which becomes a light-receiving surface after molding and has a dimensional ratio within a predetermined range with respect to a prism obtained after molding. The minimum viscosity of the glass base material is 10 ⁴ Pa by preparing the base material, holding the glass base material in the holding part of the feeding means, and feeding the glass base material into the heating furnace.
· Desired in a substantially similar shape to the glass base material by heating to a predetermined temperature of s or more and less than 10 ⁶ Pa · s, stretching the lower part of the glass base material with a tensioning means, and cutting to a predetermined length The size of the range and the Ra value of the surface roughness are 1 / wavelength of the incident light.
A method for producing a prism, comprising: obtaining a long body having an equivalent surface of 4 or less, and cutting the long body to a desired length. 6. The method for manufacturing a prism according to claim 5, wherein the light-incident surface of the elongated body is polished.