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Dichroic filter

A dichroic mirror and wavelength technology, applied in the field of dichroic mirrors, can solve problems such as difficult to avoid stray light transmission

Inactive Publication Date: 2009-03-18
NIKON CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0010] However, even if the technology disclosed in Patent Document 1 is applied, it is not easy to avoid the transmission of stray light incident at a large incident angle.

Method used

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Examples

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Embodiment Construction

[0033] Hereinafter, an example of an embodiment of the present invention will be described, but before that, the figure 1 To illustrate the principle of the present invention. figure 1 This is a diagram schematically showing the spectral transmission characteristics of a multilayer film filter formed by alternately laminating high-refractive materials and low-refractive materials. When this multilayer film filter is used, the central incident angle is set to 0°. The solid line indicates the spectral transmission characteristic when the incident angle is 0°, and the dotted line indicates the spectral transmission characteristic for obliquely incident light.

[0034] As shown in the figure, when the incident angle is not 0°, the curve representing the spectral transmission characteristic is shifted toward the low wavelength side. This offset increases as the angle of incidence becomes larger. In addition, as disclosed in Patent Document 1, the larger the ratio of the optica...

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Abstract

The invention provides a dichroic filter which transmits a significantly reduced percentage of stray light that impinges at large incident angles. A first multilayer film filter (2) is formed on one surface of a transparent substrate (1) such as glass, and a second multilayer film filter (3) is formed on the other surface. The multilayer film filter (2) serves as a low-pass filter and the multilayer film filter (3) serves as a high-pass filter. The multilayer film is designed such that the shift of spectral transmission characteristics due to a variation in incident angle becomes larger in the multilayer film filter (3) than in the multilayer film filter (2). Consequently, even if transmission takes place at a wavelength that should shade the light due to shift of spectral transmission characteristics in the multilayer film filter (2), transmission is interrupted at that wavelength due to shift of spectral transmission characteristics in the multilayer film filter (3). Consequently, a possibility for stray light entering at a large incident angle to pass through a dichroic filter lowers sharply.

Description

technical field [0001] The invention relates to a dichroic mirror. Background technique [0002] The purpose of the dichroic mirror is to transmit the light of the first wavelength and reflect the light of the second wavelength without being transmitted in the field of optical communication. For example, a dichroic mirror designed to transmit light with a wavelength of 1560nm and reflect light with a wavelength of 1310nm that cannot be transmitted is to make the light with a wavelength of 1560nm emitted from an optical fiber enter the dichroic mirror vertically and transmit it, and make the light from another The 1310nm light emitted by the light source is reflected by the same dichroic mirror and enters the above-mentioned optical fiber. [0003] In the above optical system, since the 1560nm light is transmitted through the dichroic mirror with a high transmittance due to the vertical incidence, the amount of stray light is small, and there is no need to consider it substa...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02B5/28
CPCG02B5/281G02B5/28G02B5/285
Inventor 岗本干夫
Owner NIKON CORP