JPH04126201U - Multilayer dielectric film wavelength filter - Google Patents

Abstract

(57) [Summary] [Purpose] To vary the wavelength characteristics depending on the position of the filter. [Structure] Dielectric films 15a, 15 on glass substrate 11
b, 15c are stacked, and dielectric films 15a, 15b, 15
Each film thickness at the left end of c is the same, and each optical film thickness at the right end is the same, but it is thicker than the left end, and the optical film thickness gradually changes between the left end and the right end. .

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This idea consists of multiple dielectric films stacked on top of each other, allowing light of a specific wavelength to be selectively passed through. A bandpass filter that passes light below a certain wavelength, a lowpass filter that passes light below a certain wavelength, and a A multilayer dielectric film used in high-pass filters, etc. that passes light with wavelengths longer than Concerning long filters.

0002

[Conventional technology]

FIG. 2 shows a conventional multilayer dielectric film wavelength filter. On a transparent substrate 11 such as glass A plurality of dielectric films 12a, 12b, and 12c are sequentially laminated. each dielectric The body membranes 12a, 12b, 12c have the same thickness and are uniform in each part. It was selected to be 1/4 of the heart's wavelength. High refractive index as dielectric films 12a, 12b, 12c The combination of superposition of a refractive index material (H) and a low refractive index material (L), and the refractive index of each layer. Band pass filter, high pass filter, low pass filter etc. is configured. The selection of each layer and the refractive index of each layer are already known. There is. Usually, a considerable number of dielectric films are stacked, for example, 10 layers.

0003 The filter shown in Figure 2A is a bandpass filter that selectively transmits light with a wavelength of 700 Å, for example. Conventionally, each part of the dielectric film filter has a wavelength of 700 Å. Allow light to pass through.

0004

[Problem that the idea aims to solve]

Conventionally, in cases where a wavelength deviated from the center wavelength determined by the thickness of the dielectric film is required, In this case, it was necessary to prepare another dielectric film wavelength filter. Also, in the past, for example For example, diffraction gratings have been used to separate incident light, but diffraction gratings have large losses, making them difficult to select. The power of the selected light is significantly reduced. Also, light with a wavelength other than the selected wavelength Although the selected light is in a different direction, it goes to the side that receives the selected light, so this is reflected internally. This could cause stray light.

[0005]

[Means to solve the problem]

According to this idea, each dielectric film is The film thickness increases uniformly.

[0006]

【Example】

FIG. 1A shows an embodiment of this invention. A dielectric film is formed on a transparent substrate 11 such as a glass plate. 13a, 13b, and 13c are stacked. In this example, these dielectric films 13a~ This is a case where a refractive index of 13c is selected to form a bandpass wavelength filter. With this idea The thickness of each of the dielectric films 13a to 13c is determined in a certain direction within the plane formed by the transparent substrate 11. 1A, it increases uniformly and monotonically from left to right. In other words, this At the left end of the filter 14, the thickness of each dielectric film 13a to 13c is the same, and The film thickness of each dielectric film 13a to 13c is the same even at the right end, but it is thicker at the right end than at the left end. The film thickness of each dielectric film 13a to 13c is made large.

[0007] Since the center of the transmission wavelength is four times the thickness of each of the dielectric films 13a to 13c, FIG. In the dielectric film filter 14 shown in FIG. The transmission wavelength at the right end is larger than the length, and the transmission wavelength gradually decreases between these parts. It's changing. For example, the left end and right end of the filter 14 in FIG. Looking at the four positions 15a to 15d from the left at approximately equal intervals, these positions The wavelengths transmitted through the filter 14 at the positions 15a, 15b, 15c, and 15d are shown in FIG. As shown in B, the thicknesses are 500 Å, 600 Å, 700 Å, and 800 Å.

[0008] If such a wavelength bandpass type dielectric film filter 14 is used, the incident light beam can be is incident on this filter 14 at right angles, and the thickness of the dielectric film of the filter 14 changes. Measure the power of the transmitted light at each position while changing the direction of the If so, the wavelength characteristics of the incident light beam can be measured. In this case, the diffraction grating The transmission loss is lower than that of the second one, and unnecessary light is reflected by the filter, making it difficult to receive light. It does not arrive at the element side as stray light. In such a case, use a filter as shown in Figure 1C. 14 is disk-shaped, a disk-shaped dielectric film is formed in multiple layers, and from one radius 16, an example is obtained. For example, the thickness of each dielectric film increases in the direction of the arrow clockwise, A light beam is incident on a point eccentric from the center of this disc-shaped filter 14, and the filter 1 4 can be rotated around its center.

[0009] In the above, this idea was applied to a band-pass type wavelength filter, but it is also applicable to a low-pass type wavelength filter. This invention can also be applied to filters, high-pass filters, etc.

0010

[Effect of the idea]

As described above, according to this invention, the film thickness of each dielectric material in a multilayer dielectric film is kept constant. By gradually increasing the wavelength characteristics in each part of the filter, By moving or rotating the filter, the center selection wavelength, etc. There is no need to prepare separate filters for each of these. .

[Submission date] June 3, 1992

[Procedural amendment 1]

[Name of document to be amended] Specification

[Name of item to be corrected] Detailed explanation of the invention

[Correction method] Change

[Correction details] [Detailed explanation of the idea]

0001

[Industrial application field]

This idea consists of multiple dielectric films stacked on top of each other, allowing light of a specific wavelength to be selectively passed through. A bandpass filter that passes light below a certain wavelength, a lowpass filter that passes light below a certain wavelength, and a A multilayer dielectric film used in high-pass filters, etc. that passes light with wavelengths longer than Concerning long filters.

0002

[Conventional technology]

FIG. 2 shows a conventional multilayer dielectric film wavelength filter. A plurality of dielectric films 12a, 12b, and 12c are sequentially laminated on a transparent substrate 11 made of glass or the like. The optical thickness of each dielectric film 12a, 12b, and 12c was the same and uniform in each part, and was selected to be 1/4 of the center wavelength. The combination of overlapping dielectric films 12a, 12b, and 12c with a high refractive index (H) and a low refractive index (L) and the refractive index of each layer are selected, and a bandpass filter, a high A pass filter, a low pass filter, etc. are configured. The selection of each layer and the refractive index of each layer are already known. Normally, a considerable number of dielectric films, such as 10 layers, are stacked.

0003 The filter shown in Figure 2A is a bandpass filter that selectively transmits light with a wavelength of 700 Å, for example. Conventionally, each part of the dielectric film filter has a wavelength of 700 Å. Allow light to pass through.

0004

[Problem that the idea aims to solve]

Conventionally, if a wavelength deviated from the center wavelength determined by the optical thickness of the dielectric film was required, it was necessary to prepare another dielectric film wavelength filter. Furthermore, in the past, for example, a diffraction grating was used to separate incident light into spectra, but the diffraction grating has a large loss and the power of the selected light is significantly reduced. In addition, since light with a wavelength other than the selected wavelength travels in a different direction toward the side that receives the selected light, there is a risk that this light will be reflected internally and become stray light.

[0005]

[Means to solve the problem]

According to this idea, each dielectric film is optical The film thickness increases uniformly.

[0006]

【Example】

FIG. 1A shows an embodiment of this invention. Dielectric films 13a, 13b, and 13c are laminated on a transparent substrate 11 such as a glass plate. In this example, the refractive index of these dielectric films 13a to 13c is selected to form a band-pass type wavelength filter. In this invention, each optical thickness of the dielectric films 13a to 13c increases uniformly and monotonically in a certain direction within the plane formed by the transparent substrate 11, that is, in the direction from left to right in FIG. 1A. In other words, at the left end of this filter 14, the optical thicknesses of the dielectric films 13a to 13c are the same, and at the right end, the optical thicknesses of the dielectric films 13a to 13c are the same, but the right end is thicker than the left end. However, each of the dielectric films 13a to 13c has a large optical thickness.

Since the center of the transmission wavelength is four times the optical thickness of each of the dielectric films 13a to 13c, in the dielectric film filter 14 shown in FIG. 1A, the center of the transmission wavelength at the left end of the filter 14 is The transmission wavelength becomes large in the region, and the transmission wavelength gradually changes between these regions. For example, when looking at four positions 15a to 15d from the left at approximately equal intervals between the left end and right end of the filter 14 in FIG. 1A, the wavelengths transmitted through the filter 14 at each of these positions 15a, 15b, 15c, and 15d are As shown in FIG. 1B, the thicknesses are 500 Å, 600 Å, 700 Å, and 800 Å.

[0008] If such a wavelength band-pass type dielectric film filter 14 is used, the incident light beam is made incident on the filter 14 at right angles, and the filter 14 is directed in the direction in which the film thickness of the dielectric film changes. By measuring the power of the transmitted light at each position while changing the wavelength characteristics of the incident light beam, it is possible to measure the wavelength characteristics of the incident light beam. In this case, transmission loss is smaller than that of a diffraction grating, and unnecessary light is reflected by the filter and does not reach the light receiving element as stray light. In such a case, as shown in FIG. 1C, the filter 14 is formed into a disk shape, and the disk-shaped dielectric films are formed in multiple layers, and the optical direction of each dielectric film is adjusted clockwise from one radius 16 in the direction of the arrow. A light beam may be incident on a point eccentric from the center of the disc-shaped filter 14, and the filter 14 may be rotated about the center.

[0009] In the above, this idea was applied to a band-pass type wavelength filter, but it is also applicable to a low-pass type wavelength filter. This invention can also be applied to filters, high-pass filters, etc.

0010

[Effect of the idea]

As described above, according to this invention, by gradually increasing the thickness of each dielectric of the multilayer dielectric film in a certain direction, the wavelength characteristics differ in each part of the filter, and the filter can be moved or rotated. This makes it possible to change the center wavelength , etc., and there is no need to prepare separate filters in response to these changes.

[Brief explanation of drawings]

FIG. 1A is a sectional view showing an embodiment of this invention, B is a transmission characteristic diagram of each part of the filter, and C is a plan view showing another example of this invention.

FIG. 2 is a cross-sectional view showing a conventional multilayer dielectric film wavelength filter.

Claims (1)

[Scope of utility model registration request] 1. A multilayer dielectric film wavelength filter in which a plurality of dielectric films are stacked one on top of the other, characterized in that the thickness of each dielectric film increases uniformly in a certain direction within a plane formed by the filter. Multilayer dielectric film wavelength filter.