JPS61201202A - Reflection mirror - Google Patents

Abstract

PURPOSE:To obtain a low-cost reflection mirror which does not require polishing by subjecting a heat-resistant high-polymer film to reflection coating on the laser light exit side and non-reflection coating on the opposite side and maintaining the state of exerting tension to this film. CONSTITUTION:The film 4 is fixed by a jig 5 which holds the film 4 in the state of exerting tension thereto in order to subject the film to coating. A reflective dielectric material 2 is coated from a target 6 to the film 4, then the jig 5 is turned upside down and similarly a non-reflective dielectric material 3 is coated on the film. The reflection mirror is obtd. if a frame 7 is fixed to the material 3 side by an adhesive agent 8 while the film 4 is kept tensed by the jig 5 upon completion of coating on both sides of the film 4. The heat resistant temp. of the film 4 is 400 deg.C and withstands satisfactorily 300-350 deg.C temp. during coating. The low-cost reflection mirror which does not require polishing is obtd. by using the film 4 having the excellent heat resistance and surface smoothness.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a reflecting mirror that reflects laser light.

BACKGROUND OF THE INVENTION In recent years, reflective mirrors have been widely used for optical measurements and inspections.

As a conventional technique, for example, the following document 2 basso (Toshiharu Tako et al. "Optical Measurement Handbook".

There is a reflecting mirror using the principle shown in ``Kyokusho Shoten, July 1981, pages 4 to 7''.

An example of the conventional reflecting mirror mentioned above will be described below with reference to all the drawings. FIG. 6 is a sectional view showing the structure of a conventional reflective ε-ray.

In Fig. 6, 1 is quartz glass (hereinafter simply referred to as glass), and 2 is a reflective dielectric material (hereinafter simply referred to as dielectric material) coated on glass 1 by vapor deposition or sputtering (hereinafter simply referred to as coating). It is 2. Similarly, 3 is a non-reflection dielectric material (hereinafter simply referred to as dielectric material).

FIG. 6 shows the reflection principle in the case of a single layer coating.

In FIG. 6, glass 1 and dielectric material 2 have the same structure as in FIG. θ is the incident angle of light entering a substance with a refractive index n1, θ2 is the refraction angle in the dielectric substance 2 with a refractive index n2 when incident light A enters at an angle θ1, θ
3 is the transmission angle through the glass 1 having a refractive index n3 of light refracted at an angle θ2. r is the reflection coefficient of light reflected at an angle of θ1, t is a transmission coefficient of light transmitted at an angle of θ3, and e is the dielectric coating thickness.

Note that hatching is omitted in FIG. 6.

FIG. 7 shows the optical film thickness and reflectance expressed as the product of the refractive index n2 of the dielectric material 2 and the coating film thickness e in a single layer coating of the dielectric material 2.

The operation of the reflecting mirror configured as described above-1- will be described below.

The reflectance R of the surface of the glass 1 with respect to superimposed incident light when the glass 1 is not coated is given by equation (1) from Snell's law and Fresnel's equation.

Here, n3 is the refractive index of the glass. It can be seen from equation (1) that the reflectance R increases as the refractive index of the glass increases. However, the refractive index of glass is about 1.4 to 1.6, so a highly reflective mirror cannot be expected. Therefore, by coating the dielectric material 2 with a dielectric material 2 having a refractive index higher than that of glass, a highly reflective mirror can be obtained.

The principle will be explained based on FIG. refractive index n1
A part of the incident light A that enters from the air layer at an angle of 01 becomes reflected light r1, and a part of the incident light A is guided to the dielectric material 2 having a refractive index of n2 at an angle θ2. Similarly, a part of the light is reflected and becomes reflected light r2, and a part of the light is guided at an angle θ to a glass having a refractive index n and becomes transmitted light t1. Since reflection is repeated on both sides of the coating film thickness e of the dielectric material 2, the overall Fresnel reflection coefficient r and transmission coefficient t change depending on the optical film thickness n2×e due to the interference effect. . From Fresnel's equation, the reflection coefficient r12 for a light wave incident on the dielectric material 2 with a refractive index n2 from an air layer with a refractive index n1 is expressed by equation (2).

The transmission coefficient t12 is expressed by equation (3).The reflection coefficient r23° for the light wave incident from the dielectric material 2 with the refractive index n2 to the glass 11 with the refractive index n3.The transmission coefficient t25 is also the same, so the equation is omitted. . At this time, the reflection coefficient r
can be expressed by equation (4), and the transmission coefficient t can be expressed by equation (6).

Here λ - wavelength of human radiation It is expressed with pride. Therefore, the reflectance R1 and the transmittance TK R-1-T-1... (8) 6 pence becomes.

When the thickness of the film is 300 nm, R becomes zero if the relationship n1·n6-n2' (10) holds. This is called the no-reflection condition. If such a coating film is applied, the reflectance becomes zero, so it is called an antireflection film. FIG. 7 shows the results of calculating equation (6) by setting nl to 1, which is the refractive index of the air.

Figure 7 shows the above optical film thickness on the horizontal axis and the reflectance on the vertical axis, assuming that the refractive index n2 of dielectric material 2 is smaller than the refractive index n3 of glass 1, compared to the case without coating. decreases. It becomes a coating film, and it becomes the same state as 1 without the coating film.

1. When the refractive index n2 of the dielectric material 2 is greater than the refractive index n3 of the glass 1, the reflectance increases if the coating thickness is made an odd multiple of 1. In order to obtain a high reflectance, a multilayer coating of a dielectric material having a high refractive index and a dielectric material having a low refractive index may be applied alternately. The dielectric materials used here are titanium oxide (Tie) and silicon oxide (SiO).
Then, 3 to 4 layers were coated. The incident wavelength λ is 830
It is nm. It's a good idea to cocoon the metal [7]
It's okay. In this case, the reflectance is the reflectance of the metal itself.

Problems to be Solved by the Invention However, with the above configuration, it is necessary to polish the surface of the glass 1 of the one-reflection mirror. Therefore, after cutting the glass art material into the desired shape of the glass 1, rough polishing, medium polishing, and final polishing must be performed, which takes a lot of man-hours, and there is no possibility of resetting the surface condition of the glass 10 by polishing.

Therefore, there is a problem in that the defective rate increases and the price becomes high, and mass production cannot be expected.Therefore, it is desirable to develop a reflective mirror that does not require polishing.

In view of the above problems, the present invention provides a low-cost reflective mirror e that does not require polishing.

Means for Solving the Problems In order to solve the above problems, the reflective mirror of the present invention has a reflective coating A on the laser beam output side.
The opposite side from II is composed of a heat-resistant polymer film coated with an anti-reflection coating and a frame that maintains the heat-resistant polymer film under tension.

Function The present invention eliminates the need for polishing time due to the above-described configuration. Therefore, a low-cost reflecting mirror suitable for mass production can be obtained.

EXAMPLE Hereinafter, a reflecting mirror according to an example of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing the configuration of a reflecting mirror in an embodiment (C) of the present invention.

9., -7 In FIG. 1, 4 is a heat-resistant polymer film (hereinafter simply referred to as film), and the material name is polyimide. This film 4 is coated with reflective and non-reflective coaching as in the conventional film. FIG. 2 shows the smoothness (also referred to as straddling surface accuracy) of the film 4. 3 to 4 illustrate a mirror construction method using the film 4. FIG.

FIG. 3 shows a film 4 coated with a reflective dielectric material 2 and a non-reflective dielectric material 3 by sputtering or vapor deposition, and reference numeral 6 denotes a sputtering and vapor deposition jig (hereinafter referred to as (simply referred to as a jig). 6 is a target for sputtering and vapor deposition. 4(A) is a sectional view showing the frame 7 that maintains the tension of the film 4 and the state of the adhesive 8 applied to the frame 7, and FIG. 4(B) is a sectional view showing the state of the frame 7 on the jig 6.
[Layout diagram showing a state in which the held film 4 is placed,
FIG. 4(C) is an enlarged sectional view of the arc Y in FIG. 4(B). In each figure, the same parts are given the same numbers.

1, 2, 3, 4, and 7 for the reflecting mirror configured as shown below.
The operation will be explained using the following example.

FIG. 1 shows the structure of the reflective mirror, and the reflective dielectric material 2 and the non-reflective dielectric material 3 other than the film 4 are the same as those of the conventional mirror. Therefore, the principle of coating for obtaining high reflectance is the same as the conventional example explained using FIG. 7.

However, a similar high reflectance can be obtained by simply depositing aluminum, gold, or nickel.

The surface of the film 4, which is important here, will be explained using FIG. 2. Figure 2 (A) shows the film surface; Figure 2 (A) shows the film surface;
B) shows the characteristics of the back side.

In FIG. 2(A), 03), the horizontal axis represents the measured length from the reference point, and the vertical axis represents the smoothness, and the smoothness of both the front and back surfaces of the film 4 is 370 to 4008.

Note that the measurement conditions are that the needle shape is spherical (r=12.7μηz) and the needle pressure is 251ii′.

When λ is a cutting wavelength of λ-830 nm, the smoothness is -2°, which is sufficient for use without polishing. By the way, most common glasses on the market have a diameter of 1 mm and a length of 2 mm.

To coat this film 4, fix it with a jig 6 that applies tension to the film 4 as shown in FIG. 3. Then, coat the reflective dielectric material 2 from the target 6 to the film 4 Next, coat the non-reflective dielectric material 3 on the back side with the jig 5 in the same way as shown in Figure 1. After completing the coating on both sides of the film 4, use the jig 5 to coat the film 4 with the non-reflective dielectric material 3. Tension is added -
In this state, as shown in FIG. 4, it can withstand temperatures of 300'' to 350'C when adhesive ink is applied to the non-reflective dielectric material 3 side.

As described above, according to this embodiment, by using the film 4 having heat resistance and excellent surface smoothness, an inexpensive reflective mirror that does not require polishing can be obtained. In this embodiment, a high-reflection beam splitter is used, but a beam splitter having the same reflectance and transmittance may be used.

Although polyimide is used as the electrically resistant polymer film material in this embodiment, similar effects can be obtained with other one-sided thermal polymer films.

Effects of the Invention As described above, the present invention uses a heat-resistant polymer film having heat resistance and excellent surface smoothness (thereby,
Since no polishing is required, the number of man-hours is reduced, the defective rate is reduced, and the cost is low. Therefore, mass production is possible.

Furthermore, the shape of the reflecting mirror can be freely determined depending on the shape of the frame. Even if the shape becomes dog-like, the frame does not need to be very thick, so the overall thickness can be made thinner.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a reflective mirror in a practical example of the present invention, Figure 2 (A) is a smoothness characteristic diagram of the film used in the present invention, and Figure 3 shows the state of coating on the film. Figure 4 (A) is a cross-sectional view showing the state of the frame and adhesive that fixes the coated film obtained in Figure 3, and Figure 4 (B) is the case where the film is placed on the jig. FIG. 4(C) is an enlarged cross-sectional view of the flat part, and FIG. 6 is a cross-section 13-' of a conventional reflecting mirror. Figure 6 is a cross-sectional view showing the principle of a high reflection mirror, Figure 7 is a top view.
The figure is a characteristic diagram showing the relationship between optical film thickness and reflectance. 1... Quartz glass, 2... Reflective dielectric material, 3
..... Dielectric material for non-reflection, 4..... Polymer film, 7..... Frame. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Diagram LQ. Ura of --- Irimurasho θ2 One layer of light θ3 --- Long cloudy 4 ``----''l'fta&Q 7th figure, 9th place, 41 77'

Claims (2)

[Claims] (1) A heat-resistant polymer film with a reflective coating on the laser beam emission side and a non-reflective coating on the side opposite to the laser beam emission side, and a frame that holds the heat-resistant polymer film under tension. A reflective mirror characterized by comprising: (2) The reflective mirror according to claim 1, wherein polyimide is used as the heat-resistant polymer film.