WO2013073359A1

WO2013073359A1 - Filter for reducing higher-order light and stray light, and spectral device using filter

Info

Publication number: WO2013073359A1
Application number: PCT/JP2012/077832
Authority: WO
Inventors: 泰之古川; 正章北脇
Original assignee: 株式会社島津製作所
Priority date: 2011-11-18
Filing date: 2012-10-29
Publication date: 2013-05-23
Also published as: TW201321803A; TWI503583B

Abstract

A cut filter covering the sensor surface of a sensor array is provided with two filter regions. A multilayer film filter is formed in each of the filter regions. Formed in one of the filter regions is a multilayer film filter acting as a short-pass filter which allows transmission of light on the short-wavelength side and blocks light on the long-wavelength side; and formed in the other filter region is a multilayer film filter acting as a long-pass filter which allows transmission of light on the long-wavelength side and blocks light on the short-wavelength side.

Description

Filter for reducing higher-order light and stray light and spectroscopic device using the filter

The present invention relates to a cut filter arranged on the incident side of a photodetector for detecting the intensity of light in each wavelength region dispersed by a spectrometer and a spectroscopic device using the cut filter.

Fig. 10 shows the characteristics of the diffracted light of the diffraction grating. In principle, the diffraction grating has a phenomenon in which adjacent order spectra partially overlap when light in a wide wavelength range is incident. For this reason, in a spectroscopic device that splits measurement light by a diffraction grating and guides it to a photodetector (sensor array), light in different wavelength ranges is incident on a channel where light in a certain wavelength range is incident, There was a problem that the measured value of light was measured higher than the actual value.

Therefore, in order to remove light in a wavelength range different from the wavelength range that should be incident, overlapping wavelengths are removed using a colored glass filter or the like. For example, when the primary light incident on a certain area of the sensor array is light having a wavelength range of 600 to 800 nm and the secondary light is light having a wavelength range of 300 to 400 nm, the secondary light is shielded. A filter that cuts off a wavelength of 400 nm or less is used.

FIG. 11A shows a configuration example of such a polychromator spectrometer. The polychromator can simultaneously measure multi-wavelength light separated by the diffraction grating 26 by using the sensor array 22 as a photodetector. In order to cut the high-order light generated from the diffraction grating, the colored glass filter 24 is disposed in front of the long-wavelength side channel on the sensor surface of the sensor array 22 affected by the high-order light, and the short-wavelength side channel is not provided with the colored glass filter. It is common.

Also, stray light (causing noise to other channels) caused by multiple reflections on the front and back of the cover glass that protects the sensor array is also a problem. In order to solve this problem, as shown in FIG. 11B, a cover glass 25 that protects the sensor surface of the sensor array 22 is composed of a transmission part and a light shielding part, and stray light due to multiple reflections in the transmission part is shielded. It has been proposed to prevent the light from being incident on other channels by blocking the light (see Patent Document 1).

JP-A-5-332834

In the polychromator spectrometer of FIG. 11A, high-order light is not generated on the short wavelength region side of the sensor array 22 and there is no overlapping of the orders of diffracted light, and therefore, a colored glass filter is disposed only on the long wavelength region side. However, it is impossible to prevent scattered light from the diffraction grating or the surface of the spectroscope casing or stray light generated by multiple reflection in the cover glass from entering the channel on the short wavelength region side, and there is a limit to reducing the noise of the spectrum. It was.

In addition, when the cover glass 25 is provided with a transmission part and a light shielding part as shown in FIG. 11B, channels covered by the light shielding part among the channels of the sensor array 22 cannot be used for measurement. There was a problem of fewer.

Therefore, an object of the present invention is to reduce spectrum noise and improve measurement sensitivity without reducing the channels that can be used on the sensor surface of the photodetector.

The filter of the present invention is arranged so as to cover the entire sensor surface of the photodetector having a sensor surface in which a plurality of channels for detecting light dispersed by the spectrometer is arranged. The filter surface is composed of a plurality of filter regions having different transmission wavelength characteristics, and these filter regions are arranged in the channel arrangement direction of the sensor surface of the photodetector, and are on the long wavelength side which is a wavelength range of a predetermined wavelength or more. A filter film covering the channel portion for detecting light is formed with a multilayer filter that does not transmit light on the short wavelength side, which is shorter than a predetermined wavelength, and covers the channel portion for detecting light on the short wavelength side. A multilayer filter that does not transmit light on the long wavelength side is formed in the filter region.

A spectroscopic device according to the present invention divides measurement light using a spectroscope and detects the spectroscopic light guided to a photodetector having a sensor surface having a plurality of channels. The filter of the present invention is arranged so as to cover the surface.

In the filter of the present invention, the filter surface is composed of a plurality of filter regions having different transmission wavelength characteristics, and these filter regions are arranged in the channel arrangement direction of the sensor surface of the photodetector, and have a wavelength range of a predetermined wavelength or more. In the filter region that covers the channel portion for detecting the long-wavelength light, a multilayer filter that does not transmit the short-wavelength light having a wavelength less than the predetermined wavelength is formed to detect the short-wavelength light. In the filter region covering the channel portion, a multilayer filter that does not transmit light on the long wavelength side is formed. Therefore, the incidence of high-order light is reduced in the channel on the long wavelength side of the photodetector, and the channel on the short wavelength side Then, the incidence of long wavelength light and stray light due to scattering is reduced. By disposing this filter in front of the sensor surface of the photodetector, noise in the detection signal obtained by the photodetector can be reduced and measurement sensitivity can be improved. In addition, by configuring the filter region with a multilayer filter, each filter region can be designed to transmit or block light in an arbitrary wavelength range, so the degree of freedom in designing a spectroscopic device rather than a colored glass filter Will improve.

In the spectroscopic device of the present invention, since the filter of the present invention is arranged so as to cover the sensor surface of the photodetector, measurement is performed while reducing noise while performing measurement using all the channels of the photodetector. Sensitivity can be improved.

It is a block diagram which shows roughly one Example of a spectroscopic device. It is a figure which shows the example which covered the sensor surface of the sensor array with the cut filter as an example of a structure of the sensor array part of the Example. It is a figure which shows the example which covered the sensor surface of the sensor array through the cover glass as an example of a structure of the sensor array part of the Example. It is a figure which shows one Example of a cut filter, (A) is a top view, (B) is sectional drawing in a filter area | region array direction. It is a graph which shows an example of the light transmission characteristic of two filter area | regions of a cut filter. It is an example of the light-absorption spectrum of the short wavelength side in the case where it does not arrange | position with the case where a cut filter is arrange | positioned in front of a sensor array. It is a figure which shows the other Example of a cut filter, (A) is a top view, (B) is sectional drawing in a filter area | region array direction. It is a graph which shows an example of the light transmission characteristic of each filter area | region of the cut filter of the Example. It is data which shows an example of the film | membrane structure of the short pass filter and long pass filter currently formed in the filter area | region of a cut filter. It is data which shows an example of the film | membrane structure of the short band pass filter and long band pass filter currently formed in the filter area | region of a cut filter. It is a conceptual diagram for demonstrating the characteristic of the diffracted light from a diffraction grating. It is a figure which shows the example which uses a color glass filter as an example of a structure of the sensor array part of the conventional spectrometer. It is a figure which shows the example which processed the cover glass which protects the sensor surface of a sensor array as another example of a structure of the sensor array part of the conventional spectrometer.

In a preferred embodiment of the filter of the present invention, the filter surface covers one long wavelength side filter region covering the channel portion for detecting light on the long wavelength side and the channel portion for detecting light on the short wavelength side. It consists of one short wavelength side filter region, a long pass filter is formed in the long wavelength side filter region, and a short pass filter is formed in the short wavelength side filter region. If the filter surface is composed of two filter regions, the noise of the detection signal of the photodetector can be reduced without increasing the manufacturing cost of the filter.

Further, if each multilayer filter is a band pass filter, the light incident on the photodetector can be further limited, and the incidence of unnecessary wavelength components on the photodetector can be further reduced. Thereby, the amount of stray light is also reduced, and the S / N ratio can be further improved.

Hereinafter, an embodiment of a spectroscopic device will be described with reference to the drawings together with an embodiment of a filter for reducing higher-order light and stray light.
FIG. 1 is a block diagram schematically showing an embodiment of a spectroscopic device. This spectroscopic device splits the measurement light entering from the entrance slit 2 with a concave diffraction grating 4 as a spectroscope and guides it to a sensor array 6 as a photo detector, and detects the intensity of each constant wavelength component. A cut filter 8 for reducing scattered light and stray light is disposed in front of the sensor surface of the sensor array 6.

3A and 3B show an embodiment of the cut filter 8. FIG. 3A is a plan view and FIG. 3B is a cross-sectional view in the filter region arrangement direction.
The cut filter 8 includes

filter regions

12 a and 12 b that are arranged in a channel arrangement direction provided on the sensor surface of the sensor array 6. The cut filter 8 covers a portion where the short wavelength detection channels (for example, less than 540 nm) on the sensor surface of the sensor array 6 are arranged with the filter region 12a, and the long wavelength detection channel (on the sensor surface of the sensor array 6) (For example, 540 nm or more) is arranged so as to cover a portion where the filter region 12b is arranged. As shown in FIG. 2A, the cut filter 8 may also be directly fixed to the sensor surface as a cover glass that protects the sensor surface of the sensor array 6, or as shown in FIG. 2B. As shown, the sensor surface may be covered via the cover glass 7.

In the

filter regions

12a and 12b, multilayer filters in which a plurality of dielectric layers are laminated on one side or both sides of the transparent substrate 10 made of, for example, quartz glass are formed. The multilayer filter formed in the filter region 12a is a short pass filter that transmits light on the short wavelength side and blocks light on the long wavelength side. The multilayer filter formed in the filter region 12b is a long pass filter that transmits light on the long wavelength side and blocks light on the short wavelength side.

FIG. 4 shows the light transmission characteristics of the two filter regions of the cut filter 8. As shown in this figure, the short-pass filter in the filter region 12a is formed so as to transmit light having a wavelength of 300 to 540 nm and shield light having a wavelength of 550 nm or more. The long pass filter is formed to transmit light having a wavelength of 540 to 800 nm and shield light having a wavelength of 520 nm or less.

By disposing the short-pass filter as described above in the portion where the short-wavelength detection channels of the sensor array 6 are arranged, the long-wavelength component is a short-wavelength detection channel due to scattered light or stray light from the long-wavelength side. It can suppress that it is incident on and detected.

FIG. 5 is an example of an absorbance spectrum on the short wavelength side when the cut filter 8 is arranged in front of the sensor array 6 and when the cut filter 8 is not arranged. By arranging a short pass filter in the short wavelength detection channel portion of the sensor array 6, the base (I ₀ ) of the detection signal of the sensor array 6 is reduced as compared with the case where no short pass filter is arranged, and the absorbance (= −log (I / I ₀ )) increases overall. That is, it can be seen that the measurement sensitivity is improved by arranging the cut filter 8.

An example of the filter film structure formed in the

filter regions

12a and 12b is shown in FIG. In FIG. 8, the layers are shown in the order of being stacked from the transparent substrate 10 side. In this embodiment, two filter regions are provided in the cut filter 8, but three or more filter regions may be provided to give different light transmission characteristics to each other. If more filter regions are provided in the cut filter 8 and the light transmission characteristics of each filter region are matched to the detection wavelength of each channel provided on the sensor surface of the sensor array 6, the extra incident light to each channel can be made more efficient. Therefore, the noise can be further reduced and the measurement sensitivity can be further improved.

FIG. 6 shows an example in which the cut filter 8 is provided with two band

pass filter regions

13a and 13b. A short band pass filter is formed in the filter region 13a, and a long band pass filter is formed in the filter region 13b. The light transmission characteristics of the short bandpass filter and the long bandpass filter are shown in FIG. The short bandpass filter of this example is formed so as to transmit light having a wavelength of 400 to 540 nm and shield light having a wavelength of less than 400 nm and light having a wavelength of 550 nm or more. The long bandpass filter is formed so as to transmit light having a wavelength of 540 to 680 nm and shield light having a wavelength of less than 540 nm and light having a wavelength of 690 nm or more. An example of the film configuration of the filter formed in the

filter regions

13a and 13b is shown in FIG. In FIG. 9, the layers are shown in the order of being laminated from the transparent substrate 10 side.

2 entrance slit 4 diffraction grating 6 sensor array 8 cut filter 10

transparent substrate

12a, 12b, 13a, 13b filter region

Claims

A filter arranged to cover the entire sensor surface of a photodetector having a sensor surface on which a plurality of channels for detecting light dispersed by the spectroscope is arranged;
The filter surface is composed of a plurality of filter regions having different transmission wavelength characteristics, and the filter regions are arranged in the channel array direction of the sensor surface of the photodetector, and are long wavelengths having a wavelength equal to or greater than a predetermined wavelength. In the filter area that covers the channel portion for detecting the light on the side, a multilayer film filter that does not transmit the light on the short wavelength side that is less than the predetermined wavelength is formed, and the channel portion for detecting the light on the short wavelength side The filter area | region which covers the filter in which the multilayer filter which does not permeate | transmit the light of the said long wavelength side is formed.
The filter surface has one long wavelength side filter region covering a channel portion for detecting the light on the long wavelength side and one short wavelength side filter region covering a channel portion for detecting the light on the short wavelength side. The filter according to claim 1, wherein a long pass filter is formed in the long wavelength filter region, and a short pass filter is formed in the short wavelength filter region.
The filter surface has one long wavelength side filter region covering a channel portion for detecting the light on the long wavelength side and one short wavelength side filter region covering a channel portion for detecting the light on the short wavelength side. The filter according to claim 1, wherein a long band pass filter is formed in the long wavelength side filter region, and a short band pass filter is formed in the short wavelength side filter region.
In a spectroscopic device that splits measurement light using a spectroscope and detects the split light by guiding it to a photodetector having a sensor surface having a plurality of channels.
The spectroscopic device, wherein the filter according to any one of claims 1 to 3 is disposed so as to cover the sensor surface of the photodetector.