JPS5853303B2 - Standard sample for light absorption analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a standard sample for a light absorption analyzer, and provides a standard sample that can relatively easily obtain stable desired optical characteristics and is easy to handle. It is.

A type of light absorption analyzer that is configured to measure the physical quantity of a substance to be measured based on its absorption spectrum.
There are infrared moisture meters that use infrared absorption spectra.

This moisture meter is used, for example, in a papermaking process to measure the moisture content and moisture content of paper as a control signal for a papermaking machine or as data for quality control.

FIG. 1 is a characteristic diagram showing an example of the relationship between moisture content and absorption spectrum in the paper described above, and the vertical axis is the transmittance T.
(@ is shown, and the horizontal axis shows the wavelength λ (μm).

In FIG. 1, A represents the absorption spectrum in a state where the water content is zero, and B-D represent changes in the absorption spectrum when the water content increases, respectively.

As is clear from these, the wavelength of water is approximately 1.95.
It has absorption characteristics for μm light depending on its concentration.

A moisture meter is configured to measure moisture content or moisture content based on such an absorption spectrum.

By the way, in such a moisture meter, in order to obtain a highly reliable measurement signal, calibration and checking operations are performed automatically or manually.

In this calibration/checking operation, a standard sample having predetermined optical characteristics corresponding to the substance to be measured is used.

FIG. 2 is a configuration explanatory diagram showing an example of a conventional standard sample, in which a is a cross-sectional view and b is a perspective view.

In the drawing, 1 is a circular metal frame, 2 is a standard paper containing a predetermined amount of moisture in the paper itself to be measured, 3,
4 is an infrared transmitting body made of glass, for example, and 5 is a pipe for gas venting or gas injection.

The paper 2 is fixed to the inner circumference of the metal frame 1.The infrared transmitting bodies 3 and 4 are fixed to the edges of both sides of the metal frame 1 with a non-hygroscopic adhesive, etc., with the paper 1 sandwiched between them.The pipe 5 is fixed to the inner circumference of the metal frame 1. It is arranged so as to communicate through a communication hole 11 into a container made up of a metal frame 1 and infrared transmitting bodies 3 and 4.

However, the standard sample configured in this manner has the following drawbacks.

(:) The water in the paper evaporates inside the container, resulting in poor temperature characteristics.

(11) Long-term stability is lacking because the container cannot be sealed airtight.

(11D) To prepare various standard samples with different moisture contents, standard papers with different moisture contents must be constructed as shown in Figure 2, which requires a considerable number of man-hours.

OX/) The uneven texture of the standard paper causes errors due to the position of the standard sample during calibration and checking operations.

In order to solve the shortcomings of these conventional standard samples, the present inventors focused on the absorption spectrum of the measurement substance, and found that the transmittance is minimal near the measurement wavelength that contains a single layer deposited film and is absorbed by the measurement substance. A simulated optical signal similar to that obtained using the standard sample shown in FIG. 2 was obtained by using an optical filter having spectral transmission characteristics such that the transmittance is maximum near the reference wavelength, which is shorter than the wavelength.

Hereinafter, it will be explained in detail using the drawings.

FIG. 3 is a configuration explanatory diagram showing an example of the configuration of a moisture meter using a standard sample according to the present invention, in which LP is a light source, FP is a filter plate, SPL is a sample, DT is a detector, Ll,
L2 is a lens.

The output light from the light source LP passes through the lens L1 to the filter plate FP.
is incident on the

The filter plate FP includes an interference filter RF having a predetermined transmission wavelength range (center wavelength 1.8 μm) for transmitting the reference light and a predetermined transmission wavelength range (center wavelength 1.8 μm) for transmitting the measurement light.
An interference filter MF having a center wavelength of 1.95 μm) is arranged.

This filter plate FP is rotated at a constant speed.

Therefore, light having different wavelengths is alternately sent out from this filter plate FP.

The light transmitted through the filter plate FP in this manner is incident on the sample SPL.

As this sample SPL, a standard sample according to the present invention is inserted during calibration and checking, and a measurement sample is inserted during measurement.

The light that has passed through the sample SPL is incident on the detector DT via the lens L2, and is converted into an electrical signal.

Then, predetermined arithmetic processing is performed based on the electrical signals sent from these detectors DT, and force, calibration/checking operations, or moisture content and moisture content are measured.

FIG. 4 is a structural explanatory diagram showing one embodiment of the present invention, and is a cross-sectional view thereof, and parts equivalent to those in FIG. 2 are given the same reference numerals.

In FIG. 4, reference numeral 6 denotes an optical interference filter element including an optical filter element made of a single-layer deposited film.

This optical interference filter element 6 uses silicon (
It is constructed using silicon oxide (Sin), germanium (Ge), zinc sulfide (ZnS), etc. as a single layer film material.

Note that 8 and 9 are spacers.

FIG. 5 is a side view of the spectral transmission characteristics of the standard sample shown in FIG. This shows the state in which the minimum value changes.

In the characteristic diagram a, 1), the thickness of the single layer film has a relationship of a < b.

In addition, in these characteristic diagrams, the characteristics E and E indicated by solid lines are
' is the temperature t.

The characteristics F and F shown by broken lines are at temperature t
1, and these temperatures t.

, tl is t. The relationship is <tl. As is clear from these characteristics, it is recognized that as the thickness of the single layer film increases, the wavelength at which the minimum value of transmittance occurs becomes longer.

In addition, in the characteristic diagram a, wavelength 1.0 exhibits the minimum value of transmittance.
Comparing the amount of change in transmittance due to temperature change at 95 μm and the amount of change in transmittance due to temperature change at wavelength 1.95 μm in the characteristic diagram, it is recognized that the latter amount of change is smaller.

In other words, by adjusting the thickness of the single layer film, the optical properties of the standard sample with the configuration shown in Figure 4 can be made into the desired characteristics, and the optical characteristics at the measurement wavelength in the apparatus shown in Figure 3 can be adjusted to the desired characteristics. It is possible to create a standard sample with stable optical properties, with little change in transmittance due to temperature changes.

In addition, in these examples, examples of standard samples used in so-called one-light path, two-wavelength, transmitted-light measurement type moisture meters have been described, but the present invention is not limited to this, and the two-light path, two-wavelength type,
Similar effects can be obtained with standard samples of various light absorption type analyzers such as reflected light measurement type.

As explained above, according to the present invention, a standard sample that can relatively easily obtain stable desired optical characteristics and is easy to handle can be realized, and is suitable as a standard sample for various light absorption analyzers. be.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing an example of the relationship between moisture content and absorption spectrum in paper, Fig. 2 is a configuration explanatory diagram showing an example of a conventional standard sample, and Fig. 3 is a characteristic diagram showing an example of the relationship between moisture content and absorption spectrum in paper. FIG. 4 is a configuration explanatory diagram showing one embodiment of the present invention, FIG. 5 is a configuration explanatory diagram showing another embodiment of the present invention, and FIG. FIG. 2 is a side view of the spectral characteristics of a standard sample. 1... Metal frame, 3, 4... Infrared transmitting body, 6... Optical interference filter element, 7, 8...
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Claims (1)

[Claims] 1. As a standard sample for a light absorption analyzer that measures the physical quantity of a substance to be measured based on its absorption spectrum,
Use an optical filter that includes a single-layer deposited film and has spectral transmission characteristics such that the transmittance is minimum near the measurement wavelength that is absorbed by the measurement substance, and the transmittance is maximum near the reference wavelength that is shorter than the measurement wavelength. A standard sample for a light absorption analyzer.