JP2935765B2 - Manufacturing method of dichroic mirror - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a dichroic mirror which reflects only light in a specific wavelength region and transmits light in the remaining wavelength region by utilizing light interference by a thin film.

[0002]

2. Description of the Related Art Conventionally, a dichroic method has been used in which, by utilizing thin-film interference of a multilayer film deposited on a glass surface, only light in a specific wavelength region of light incident on the glass surface is reflected and the rest is transmitted. Mirrors are known.

The multilayer film is formed by alternately laminating a high-refractive-index substance and a low-refractive-index substance with a predetermined thickness, and the wavelength for switching between reflection and transmission can be controlled by the type of the laminated substance and its thickness. Are known.

[0004]

When performing spectral measurement of an object using such a dichroic mirror, one of reflected light and transmitted light is incident on a spectroradiometer and emitted from the object. Measure the spectral emissivity of the light and make the other incident on the camera to get the contour of the object,
Finally, a method of combining these two pieces of information is known.

However, in such a spectroscopic measurement of an object, there are many demands to measure the spectral emissivity of the light emitted from the object with as much light as possible over the entire wavelength range. In many cases, it is only necessary to obtain information on the contour of the object, so that the amount of light incident on the camera may be small to some extent.

For example, of the light from an object that emits heat rays, only light in a specific infrared wavelength region is incident on an infrared camera to photograph the outline of the object, and the remaining light is incident on a spectroradiometer. In the case where the spectral emissivity of the heat ray is obtained by performing the measurement, the sensitivity of the infrared camera is set to, for example, 3000 to 5000 nm.
3,000 to 5 with a dichroic mirror
Only a part of the light in the wavelength range of 000 nm is transmitted and made incident on the infrared camera, and the entire remaining light is reflected by the dichroic mirror and made incident on the spectroradiometer. It is desirable to perform spectrometry using the amount of light. When a part of light in a predetermined wavelength region is transmitted as described above, the transmittance needs to be adjusted according to the purpose and application. Therefore, it is important to facilitate the adjustment. . However, a dichroic mirror provided with a multilayer film functions to switch between substantially total reflection and substantially total transmission before and after a predetermined wavelength, and generally increases or decreases the transmittance of light in a predetermined wavelength region by increasing or decreasing the number of laminated thin layers. It was considered difficult to increase or decrease the number.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has been developed to manufacture a dichroic mirror that functions as a half mirror for light in a predetermined wavelength region and as a total reflection mirror for light in the remaining wavelength region. It is intended to provide a method.

In the method for manufacturing a dichroic mirror according to the present invention, a step of preparing a transparent substrate and a step of alternately stacking a thin layer made of a first substance and a thin layer made of a second substance on the transparent substrate are performed. Forming a basic multilayer film for substantially totally reflecting light in a wavelength region equal to or less than a predetermined value, and transmitting light in a wavelength region larger than the predetermined value at a rate equal to or higher than a high transmittance point; and Controlling the film thickness so that light in a wavelength region larger than the predetermined value as a surface layer is transmitted at a rate smaller than the high transmittance point with respect to the time of incidence of the basic multilayer film; The thin layer and the second
Forming a thin layer made of the above-mentioned substance one by one.

The "high transmittance point" means that the transmittance of light in a wavelength region larger than a predetermined value does not become lower than this point only by the basic multilayer film, and the surface layer film is provided. Indicates for the first time a reference point of the transmittance that is smaller than this point, and is set to a high transmittance value of, for example, 90%.

[0010]

According to the above construction, first, a basic multilayer film formed by alternately laminating thin layers made of a first substance and thin layers made of a second substance on a transparent substrate is provided.
Light in a wavelength region equal to or less than a predetermined value is substantially totally reflected, and light in a wavelength region larger than the predetermined value is transmitted at a rate higher than the high transmittance point.

A so-called general dichroic mirror consisting only of such a basic multilayer film functions to switch between substantially total reflection and substantially total transmission before and after a predetermined wavelength.
It has been considered that it is difficult to greatly increase or decrease the transmittance of light in a predetermined wavelength region by increasing or decreasing the number of laminated thin layers.

[0012] In fact, according to the experiments of the present applicant, for example, 20
Up to the layer, the relationship between the increase and decrease in the number of laminated thin layers and the increase or decrease in the transmittance is not recognized so much, and the transmittance is, for example,
It could not be less than 90%.

[0013] However, the present applicant has provided one thin layer of the first material and one thin layer of the second material on the basic multilayer film, and adjusted only the thickness of these thin layers. It has been found that the transmittance can be set to, for example, 70% or 50%.

The method of manufacturing a dichroic mirror according to the present invention is based on such a fact. As a result, a half mirror having a desired transmittance with respect to light in a predetermined wavelength region is formed. Light can be manufactured to function as a normal total reflection mirror, and the manufacturing process can be made extremely simple.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the method for manufacturing a dichroic mirror according to the embodiment of the present invention, a step of preparing a transparent substrate and alternately laminating a thin layer made of the first material and a thin layer made of the second material on the transparent substrate. Forming a basic multilayer film that substantially totally reflects light in a wavelength region equal to or less than a predetermined value and transmits light in a wavelength region larger than the predetermined value at a rate equal to or higher than a high transmittance point; Controlling the film thickness so that light in a wavelength region greater than the predetermined value as a surface layer is transmitted at a rate smaller than the high transmittance point with respect to the time when the basic multilayer film is incident; And forming a thin layer made of the second substance one by one.

FIG. 2 is a schematic diagram showing a layer structure of a dichroic mirror manufactured according to the first embodiment of the present invention. This dichroic mirror is made of germanium (Ge)
On a substrate 1, a basic multilayer film 2, a first surface layer 3 made of Ge (refractive index 4.00), and a second surface layer 4 made of ZnS (refractive index 2.10) are laminated in this order using an evaporation method. It is.

The basic multilayer film 2 is formed by laminating 23 layers of ZnS into odd-numbered thin layers and Ge thin-layers into even-numbered layers, so that the total film thickness is about 10 to 15 μm. Is formed.

The first surface layer 3 made of Ge is 4
nd = about 2400 nm, second surface layer 4 made of ZnS
Is formed to have a thickness of about 4nd = 2644 nm.

FIG. 1 shows the transmission characteristics of the dichroic mirror manufactured according to the first embodiment.

From the transmission characteristics shown in FIG. 1, this dichroic mirror is a total reflection mirror in a wavelength region (near infrared region) of about 1500 to 2700 nm, and a dichroic mirror in a wavelength region (middle and far infrared region) of about 2700 nm or more. Clearly function as a half mirror having a transmittance of about 50%.

On the other hand, FIG. 3 shows transmission characteristics of a dichroic mirror manufactured so that only the basic multilayer film 2 is provided on the glass substrate 1 in the layer structure shown in FIG.

From the comparison between FIG. 1 and FIG. 3, the provision of the first surface layer 3 and the second surface layer 4 as described above makes it possible to reduce the transmittance in the transmission region (region having a wavelength of about 2700 nm or more). did it.

The transmission characteristics shown in FIGS. 1 and 3 are based on values when the incident angle is set to 45 °.

Next, FIG. 4 is a schematic view showing a layer structure of a dichroic mirror manufactured according to a second embodiment of the present invention. This dichroic mirror is a glass substrate 11
A basic multilayer film 12, a first surface layer 13 made of TiO ₂ (refractive index 2.33) and SiO ₂ (refractive index 1.47) are formed thereon.
The second surface layer 14 is formed by depositing in this order using a vapor deposition method.

In the basic multilayer film, a thin layer made of TiO ₂ is used as an odd number layer, and a thin layer made of SiO ₂ is used as an even number layer.
It is formed by laminating layers and has a total thickness of about 10 to 15 μm.

The first surface layer 13 made of TiO _{2 is used.}
The second surface layer 14 made of SiO ₂ is formed to have a thickness of about 4nd = 2760 nm.

FIG. 5 shows the transmission characteristics of the dichroic mirror manufactured according to the second embodiment.

From the transmission characteristics shown in FIG. 5, this dichroic mirror is a total reflection mirror in a wavelength region smaller than about 740 nm (visible light region), and has a transmittance of 70% in a wavelength region above 740 nm (infrared region). It is clear that it functions as a half mirror.

On the other hand, FIG. 6 shows transmission characteristics of a dichroic mirror manufactured so that only the basic multilayer film 12 is provided on the glass substrate 11 in the layer structure shown in FIG.

From the comparison between FIG. 5 and FIG. 6, by providing the first surface layer 13 and the second surface layer 14 as described above, it is possible to reduce the transmittance in the transmission region (region having a wavelength of about 740 nm or more). did it.

The transmission characteristics shown in FIGS. 5 and 6 are based on values when the incident angle is set to 13 °.

As described above, in the above two embodiments, the first
By changing the thickness of the surface layers 3, 13 and the second surface layers 4, 14, the transmittance of the transmission region can be set to a desired value. The method for manufacturing the dichroic mirror of the present invention is not limited to the above-described embodiment, and the materials constituting the basic multilayer film, the first thin surface layer and the second thin surface layer to be formed. The thickness of each film can take various forms.

Also, for example, instead of ZnS as a material constituting the second surface layer 4 in the first embodiment, ZrO ₂ , TiO ₂ and Si having substantially the same refractive index as ZnS are used.
O or the like can also be used.

In the above embodiment, the incident angle is set to 13
Although the angles are set to 45 ° and 45 °, the same effect can be obtained even if the incident angle is set to any angle of 0 to 45 °. Furthermore, although the above-described embodiment describes the case of using as a half mirror, it is also possible to join a substrate on the surface layer film and use it as a half prism.

[Brief description of the drawings]

FIG. 1 is a graph showing transmission characteristics of a dichroic mirror manufactured according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a layer configuration of a dichroic mirror manufactured according to the first embodiment of the present invention.

FIG. 3 is a graph showing transmission characteristics when a surface layer is removed from a dichroic mirror manufactured according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram showing a layer configuration of a dichroic mirror manufactured according to a second embodiment of the present invention.

FIG. 5 is a graph showing transmission characteristics of a dichroic mirror manufactured according to the second embodiment of the present invention.

FIG. 6 is a graph showing transmission characteristics when a surface layer is removed from a dichroic mirror manufactured according to a second embodiment of the present invention.

[Explanation of symbols]

 1,11 Glass substrate 2,12 Basic multilayer film 3,13 First surface layer 4,14 Second surface layer

Claims (1)

(57) [Claims] 1. A step of preparing a transparent substrate, and forming a thin layer of a first substance and a second substance on the transparent substrate.
A thin layer made of the quality and brought alternately stacked, allowed substantially totally reflect light of a predetermined value or less in the wavelength region, foundation multilayer Ru allowed transmits light of wavelengths greater area than the predetermined value at a rate of more high transmission point forming a film, on the basis multilayer film, the light of greater wavelength region than the predetermined value as a surface layer, as allowed to transmitting a smaller proportion than the high transmittance points for time of incidence of the fundamental multilayer film Film thickness
Controlled and method of the dichroic mirror and the first thin layer of material characterized by comprising a second step of forming by each one layer of a thin layer made of a material.