JPH10160571A - Spectrophotometer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve measurement accuracy by an integrating sphere. SOLUTION: An integrating sphere 10 is provided with an entrance window 11, a reflection window 12, and a light detection window 13 for a sample measurement light beam LS, and diffusely reflected light is detected by a sample-side photodetector 23. On the other hand, the reference beam L
R is detected by a reference-side photodetector 24 provided outside the integrating sphere 10. Then, after adding the two detection signals by the addition amplifier 27, an arithmetic processing is performed to calculate the reflectance and the like. Thereby, the aperture ratio of the integrating sphere can be reduced, so that the efficiency of collecting the diffused light is improved, and the design of the integrating sphere is facilitated because the number of windows is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spectrophotometer,
In particular, it relates to a double beam type spectrophotometer using an integrating sphere measuring unit.

[0002]

2. Description of the Related Art FIG. 2 is a diagram showing a configuration of an integrating sphere measuring section in a conventional spectrophotometer. A sample measurement light beam LS and a reference light beam LR, which are obtained by splitting light emitted from the same light source into two, are introduced into this measuring unit in a nearly parallel manner. Each light beam LS,
LR is reflected by the reflecting mirrors 21 and 22, respectively, and guided to the inside of the integrating sphere 30 through the sample measurement light beam entrance window 31 and the reference light beam entrance window. The integrating sphere 30 has an inner surface with good reflectivity, and the introduced light beams LS and LR reach the openings of the sample measurement light beam reflection window 32 and the reference light beam reflection window 35, respectively. For example, an unknown sample and a standard white plate are respectively disposed at the measurement sample mounting position a and the reference sample mounting position b near the outside of the reflection windows 32 and 35, and the light specularly reflected by the unknown sample and the standard white plate is integrated by the integrating sphere 30. The inside proceeds as shown in FIG. 2 and is taken out of the integrating sphere 30 through the mirror light removal window 36.

On the other hand, light diffusely reflected by the unknown sample and the standard white plate travels in various directions, and is repeatedly reflected on the inner surface of the integrating sphere 30. A light detection window 33 is opened at an appropriate position of the integrating sphere 30, and most of the diffuse reflected light exits from the light detection window 33 and reaches a light receiving surface of the light detector 23 disposed close to the outside. The photodetector 23 outputs a detection signal corresponding to the intensity of the received light, and the signal is amplified by the amplifier 25 and then input to the arithmetic processing unit 28.

The double-beam integrating sphere measuring section having the above-described configuration measures the diffuse reflectance (or transmittance) of a sample as follows. First, a standard white plate having 100% diffuse reflection is placed at each of the measurement sample mounting position a and the reference sample mounting position b. Since the sample measurement light beam LS and the reference light beam LR are alternately irradiated, the photodetector 23 sets the 10
1% for the detection signal S (100) of the 0% diffused light and the reference light beam LR.
The detection signal R of the 00% diffused light is output alternately. Based on this signal, the arithmetic processing unit 28 determines the ratio D (100) of the two detection signals.
= S (100) / R is calculated. Next, the measurement sample mounting position a
An unknown sample to be measured is placed in the detector, and the detection signal S of the diffused light of the unknown sample with respect to the sample measurement light beam LS is detected by the photodetector 23.
(S) and a detection signal R of 100% diffused light for the reference light beam LR
And get Based on this signal, the arithmetic processing unit 28 calculates the ratio D (S) = S (S) / R between the two detection signals, and further calculates D (100) and D (100).
The reflectance is calculated by calculating the ratio of (S) T = D (S) / D (100) = S (S) / S (100).

[0005]

In the above configuration, since the purpose of the integrating sphere 30 is to collect the diffused light efficiently in the light detection window 33, the shape closer to the sphere is more ideal, and the aperture ratio (the The smaller the ratio of the opening area to the area, the better. However, as described above, in the conventional integrating sphere measuring section, many windows must be opened in the integrating sphere 30, so that the aperture ratio increases and the efficiency of collecting diffused light deteriorates.

Further, in this type of spectrophotometer, an integrating sphere having a diameter of about 60 to 200 mm is generally used, but it is quite difficult to design such an integrating sphere with a large number of windows at optimal positions as described above. It is. That is, when the incident angle of light on a sample or a standard white plate is large, the difference in diffuse reflectance depending on the polarization direction becomes large, and accurate measurement cannot be performed. Therefore, the incident angle is small (usually about 10 ° or less).
More preferred. Such incident angles of reflection and both light beams LS,
Under various constraints such as the interval of LR, the sample measurement beam entrance window 31, the reference beam entrance window 34, the sample measurement beam reflection window 32,
A reference beam reflection window 35 and a common mirror light removal window 36 must be provided.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to improve the measurement accuracy and sensitivity of an integrating sphere measuring section and to facilitate the design of an integrating sphere. It is to provide a spectrophotometer which can be used.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a double beam type spectrophotometer using a sample measuring light beam and a reference light beam. The light incident window, the light reflection window and the light detection window are appropriately illuminated so that the light is irradiated on the sample arranged near the outside of the light reflection window, and the diffuse reflection light from the sample is reflected on the inner surface and guided to the light detection window. B) first light detection means for detecting light taken out of the integrating sphere through the light detection window; and c) detecting a reference light beam outside the integrating sphere. And d) calculating means for calculating an index value indicating an optical characteristic of the sample based on the detection signals of the first and second light detecting means.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a spectrophotometer according to the present invention, only a sample measuring light beam is introduced into an integrating sphere through a light incident window, and reflects on a sample arranged near the outside of a light reflecting window. The diffusely reflected light travels in various directions, repeats reflection on the inner surface of the integrating sphere, and when it reaches the light detection window, exits the integrating sphere and is received by the first light detecting means. Therefore the first
The light detection means outputs a detection signal corresponding to the intensity of the diffuse reflection light from the sample. On the other hand, the second light detecting means disposed outside the integrating sphere receives a reference light beam passing through an optical path different from the sample measurement light beam, and outputs a detection signal corresponding to the intensity of the received light.

For example, the output signals of the first and second light detecting means are added in an analog manner using an adding amplifier or the like.
When the sample measurement light beam and the reference light beam are alternately irradiated, a detection signal corresponding to the diffuse reflection light from the sample and a detection signal corresponding to the reference light beam are alternately obtained at the output of the addition amplifier. Therefore, using these two detection signals, the calculating means calculates the reflectance and the transmittance as index values indicating the optical characteristics of the sample as in the related art. Of course, the arithmetic processing may be performed after, for example, converting the detection signals from the first and second light detection means into digital signals, respectively, without adding them in an analog manner.

When only the diffuse reflectance excluding the specular reflection light from the sample is calculated, a specular light removal window for extracting the specular reflection light from the sample to the outside of the integrating sphere is appropriately set. It may be provided at a location.

[0012]

According to the spectrophotometer according to the present invention, the integrating sphere is provided with only a light entrance window, a light reflection window, a light detection window and, if necessary, a maximum of four windows of a specular light removal window. Therefore, the aperture ratio can be reduced as compared with the conventional integrating sphere. For this reason, diffuse reflection light can be efficiently collected in the light detection window, and measurement accuracy is improved. In addition, the number of windows provided on the integrating sphere is reduced and restrictions on the position of the windows are relaxed, so that not only the design of the integrating sphere itself is facilitated, but also the degree of freedom in arranging external parts is increased, and a large integrating sphere is required. The measuring part can be miniaturized while using.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the spectrophotometer according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an integrating sphere measuring unit in the spectrophotometer of the present embodiment. Integrating sphere 1
At 0, an entrance window 11, a reflection window 12, a light detection window 13, and a specular light removal window 14 are respectively opened at predetermined positions. A sample-side photodetector 23 is arranged near the outside of the light detection window 13, while a reference-side photodetector 24 is arranged outside the integrating sphere 10. The detection signals of the two photodetectors 23 and 24 are amplified by a sample side amplifier 25 and a reference side amplifier 26, respectively, and then added in an analog manner by an addition amplifier 27. The output signal of the addition amplifier 27 is input to the arithmetic processing unit 28.

As in the conventional spectrophotometer of FIG. 2, the sample measurement light beam LS and the reference light beam LR obtained by splitting the light emitted from the same light source into two light beams are introduced in substantially parallel to the measuring section.
The sample measurement light beam LS is reflected by the reflecting mirror 21 and is incident on the entrance window 11.
Through the inside of the integrating sphere 10. This sample measurement light beam LS impinges on the sample placed at the measurement sample mounting position a closest to the outside of the reflection window 12, and the specular reflected light proceeds as shown in FIG. It is. The light diffusely reflected by the sample repeatedly reflects on the inner surface of the integrating sphere 10 and reaches the light detection window 13, where the light is detected by the sample-side light detector 23.
Is detected by On the other hand, the reference light beam LR is directly reflected by the reference mirror 24 after being reflected by the reflecting mirror 22. That is, in the configuration of the present embodiment, the reference light beam LR does not pass through the inside of the integrating sphere 10.

First, a standard white plate having 100% diffuse reflection is placed at the measurement sample mounting position a, and measurement is performed. As before, when the sample measurement light beam LS and the reference light beam LR are alternately irradiated,
The sample-side photodetector 23 outputs a detection signal S (100) of 100% diffused light with respect to the sample measurement light beam LS during a period during which the sample measurement light beam LS is irradiated, and outputs the detection signal S (100) during a period during which the reference light beam LR is irradiated. The output becomes zero (strictly speaking, minute noise corresponding to the dark current is output). On the other hand, the reference side photodetector 2
In 4, the detection signal R for the reference light beam LR is output during the irradiation of the reference light beam LR, and the output becomes zero during the irradiation of the sample measurement light beam LS. Summing amplifier 2
7, the detection signal is added to the detection signal S of the 100% diffused light with respect to the sample measurement light beam LS.
(100) and the detection signal R for the reference light beam LR appear alternately. Therefore, based on this output signal, the arithmetic processing unit 2
8 calculates the ratio D (100) = S (100) / R between the two detection signals.

Next, when an unknown sample to be measured is placed at the measurement sample mounting position a and the same measurement is performed, the output signal of the addition amplifier 27 shows a detection signal S () of diffused light of the unknown sample with respect to the sample measurement light beam LS. S) and the detection signal R for the reference light beam LR appear alternately. As a result, the arithmetic processing unit 28 calculates the ratio D (S) = S (S) / R between the two detection signals, and furthermore, the ratio T = D (S) / D (100) between D (100) and D (S). ) = S (S) / S (100) to calculate the reflectance.

As described above, in the spectrophotometer of the present embodiment, although the light path before the reference light beam LR reaches the photodetector does not include the integrating sphere, the reference light beam LR is calculated in the process of calculating the reflectance and the like. Is not affected by the detection signal R, the measurement accuracy is improved by an increase in the efficiency of collecting diffuse reflected light.
However, for example, when the ambient temperature is different between the measurement of the standard white plate and the measurement of the unknown sample, and the difference in the temperature dependency between the sample-side photodetector 23 and the reference-side photodetector 24 is large, the reflectivity is reduced. In the course of the calculation, the temperature fluctuation of the detection signal R on the side of the reference light beam LR influences and causes a decrease in accuracy. Therefore, it is preferable that the sample-side photodetector 23 and the reference-side photodetector 24 have characteristics as uniform as possible.

In the above-described embodiment, the two detection signals are added in an analog manner by the addition amplifier 27. However, the two detection signals are converted into digital signals by A / D converters, and thereafter are subjected to arithmetic processing to be added or equivalent. Processing may be performed.

The above embodiment is merely an example, and it is apparent that modifications and modifications can be made within the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an integrating sphere measuring unit in an embodiment of a spectrophotometer according to the present invention.

FIG. 2 is a configuration diagram of an integrating sphere measuring unit of a conventional spectrophotometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Integrating sphere 11 ... Incident window 12 ... Reflection window 13 ... Light detection window 23 ... Sample side photodetector 24 ... Reference side photodetector 27 ... Addition amplifier 28 ... Operation processing part

Claims (1)

[Claims] 1. A double beam type spectrophotometer using a sample measurement light beam and a reference light beam, comprising: a) irradiating a sample arranged in the vicinity of the outside of a light reflection window with a sample measurement light introduced from a light incident window; An integrating sphere in which a light incident window, a light reflecting window and a light detecting window are opened at appropriate positions so as to reflect the diffuse reflected light from the inner surface to the light detecting window, and b) an integrating sphere through the light detecting window. First light detecting means for detecting light taken out of the integrating sphere; c) second light detecting means for detecting a reference light beam outside the integrating sphere; and d) first and second light detecting means. And a calculating means for calculating an index value indicating an optical characteristic of the sample based on the detection signal of (1).