JPH079385B2 - Bandpass filter inspection method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for inspecting a change in spectral transmission characteristic of a bandpass filter.

[Prior Art] Conventionally, various filters have been used in optical devices such as light irradiation processing, but they are a type of interference filter and have a band-pass filter (hereinafter referred to as BP) having a spectral transmission characteristic in a specific wavelength region.
F) is used to transmit light of a wavelength in a desired region,
It is being used. This BPF is mainly provided in an optical system that requires monochromaticity or wavelength selectivity, and can be used for various properties in industrial fields, such as analyzing and using a specific wavelength to investigate the properties of a substance, or using it in an exposure apparatus. It is applied.

FIG. 2 is a cross-sectional view showing a schematic configuration of the BPF, 3 is the BPF, and the light entrance surface and the light exit surface side are sandwiched by the silica glass 3a, 3c
It has a hollow hollow space 3b from the atmosphere, and the interface between the two silica glass plates 3a and 3c on the side of the hollow 3b is provided with vapor deposition films 3d and 3d 'made of a metal or a dielectric. The vapor deposition films 3d and 3d 'allow only light of a specific wavelength to pass through. That is, the light incident on the quartz glass 3a is
The reflected light and the transmitted light interfere with each other at d and 3d ', and only the light of a specific narrow band wavelength is transmitted from the quartz glass 3c.

The spectral transmission characteristics of this BPF3 also change depending on the humidity and the ambient temperature during use, even after long-term use. That is, the center wavelength in the spectral transmission characteristic changes.

Fig. 3 is a graph showing the spectral transmittance of BPF3 with respect to the wavelength of the irradiation light. The solid line shows the initial spectral transmittance characteristic curve of BPF, and the dotted line shows the influence of humidity and temperature after long-term use. It shows a state in which the center wavelength of the spectral transmission characteristic has changed.

As described above, as a method of inspecting the displacement direction and the displacement amount regarding the transition of the BPF characteristics, a BPF using a spectrophotometer is used.
The spectral transmittance of is investigated for various wavelengths of light.

[Problems to be Solved by the Invention] As a method of inspecting the shift of the spectral transmission characteristics of the conventional BPF as described above, there is a method of using a spectrophotometer. It is a very expensive thing to be used for the purpose, and it is wasteful in terms of equipment, time, etc. to bring the inspection method by the spectrophotometer to the production line to carry out a large-scale inspection. There is a problem that it is not necessarily a good idea to use a spectrophotometer capable of measuring a wider wavelength range for the inspection of the BPF transition that measures only the wavelength.

The present invention has been made to solve such conventional problems, and an object of the present invention is to provide a BPF inspection method capable of inspecting a BPF transition on a manufacturing line with a simple and inexpensive device.

[Means for Solving Problems] In order to achieve the above-mentioned object, the present invention has
Irradiating continuous spectrum light containing light in the wavelength range of the initial spectral transmission characteristics of this BPF, the passing light of the BPF is received by a plurality of light receiving systems having different spectral sensitivity characteristics, and from the plurality of light receiving systems. A method of inspecting a shift from the initial spectral transmission characteristic of the BPF is performed by each signal.

[Operation] By performing the method described above, it is possible to inspect how much the spectral transmittance of the BPF has changed by using an apparatus having an inexpensive and simple configuration without using an expensive spectrophotometer.

[Embodiment] FIG. 1 is a view for explaining a BPF inspection method which is an embodiment of the present invention, in which 1 is a light source including a halogen lamp, and 2a
Is a condenser lens, 2b is a collimator lens, 3 is BP
F, 4,5 are light receivers having mutually different spectral sensitivity characteristics, 6 and 7 are preamplifiers for amplifying electric signals from these light receivers 4,5, 8 is a comparison of signals from these preamplifiers 6, 7,
It is an operational amplifier for calculation. And this light source 1
The light from is a continuous spectrum light at least in the wavelength range in which BPF3 is expected to shift, and its emission spectral characteristics are preferably flat. Further, in the present embodiment, assuming that the BPF 3 has the initial spectral transmission characteristic, the outputs of the photo detectors 4 and 5 cancel each other and the operational amplifier 8
Output is set to 0, and the spectral sensitivity characteristics of the photodetectors are set to have the same sensitivity characteristics in the central wavelength region of the BPF spectral transmission characteristics and have symmetrical spectral sensitivity characteristics. deep.

The light emitted from the light source 1 by the method shown in FIG.
The case of transmitting F3 will be described with reference to FIG. When BPF3 having the initial spectral transmission characteristics shown by the solid line in FIG. 3 is changed to the spectral transmission characteristics shown by the dotted line, the BP
When the light transmitted through F3 is received by the photodetectors 4,5 having the spectral sensitivity characteristics shown by the solid lines in the figure, electric signals of different magnitudes are obtained from the photodetectors 4,5. Therefore, it is understood that the central wavelength of the spectral transmission characteristic of the BPF 3 is changed by comparing and calculating the electric signals of different magnitudes by the operational amplifier 8 and outputting the result as an output signal of the operational amplifier 8. Further, by comparing the positive / negative of the difference between the output signals of the photoreceiver 4 and the photoreceiver 5 or the ratio of the output signals, whether the center wavelength of the spectral transmission characteristics of the BPF 3 has shifted to the long wavelength side or the short wavelength side. Can be determined.

Further, the characteristics of the spectroscopes 4 and 5 described above have the same sensitivity characteristics in the central wavelength region of the spectral transmission characteristics of BPF3 and further have symmetrical spectral sensitivity. You don't have to. That is, as shown in FIG. 4, two optical receivers 4 and 5 having different spectral sensitivity characteristics with respect to the central wavelength of the initial spectral transmission characteristic of BPF3, such as REC1 and REC2 or REC3 and REC4, are provided. Even when used, each receiver in the spectral transmission characteristics after the transition of BPF3
It does not matter if the values of the output signals from 4,5 are clear with respect to the initial values. In that case, even if BPF3 has the initial spectral transmission characteristics, the difference between the output signals from the two photodetectors 4 and 5 will not be 0, but if the difference or ratio is known, BPF3 By comparing with the output signal from each photodetector in the state after the spectral transmission characteristics of
It is possible to determine the amount of change in the spectral transmission characteristics of F, the direction of change, and so on.

In this embodiment, the case where two photodetectors having different spectral sensitivity characteristics are used is shown. These photodetectors are composed of each photoelectric conversion element and an optical system such as a filter having a spectral sensitivity in a certain wavelength range. It is described as an example of the light receiving system configured, and any light receiving system having the above configuration and characteristics may be used. For example, if two photoelectric conversion elements having two different photoelectric conversion characteristics similar to the above different spectral sensitivity characteristics are used, the filter is unnecessary.

[Effects of the Invention] As described in detail above, the present invention can inspect the spectral transmission characteristics of BPF easily and inexpensively by using a simple configuration.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a BPF inspection method according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a schematic configuration of the BPF.
FIG. 3 is a graph showing the spectral transmittance of BPF3 and the spectral sensitivity characteristics of each light receiver, and FIG. 4 is a graph showing the spectral transmittance of BPF with respect to the wavelength of the irradiation light and the spectral sensitivity characteristics of each light receiver. is there. In the figure. 3: BPF 3a, 3c: Quartz glass 3b: Intermediate part 3d, 3d ′: Evaporated film

Claims (1)

[Claims] 1. A bandpass filter is irradiated with continuous spectrum light including light in a wavelength range of an initial spectral transmission characteristic of the bandpass filter, and light passing through the bandpass filter has different spectral sensitivity characteristics. A method for inspecting a bandpass filter, characterized in that light is received by a plurality of light receiving systems, and a change from an initial spectral transmission characteristic of the bandpass filter is inspected by respective signals from the plurality of light receiving systems.