JP6859858B2 - Relative reflectance measuring device using an integrating sphere and its calibration method - Google Patents

Description

The present invention relates to a relative reflectance measuring device for obtaining the relative reflectance of a measurement sample with respect to a reference sample using an integrating sphere.

The integrating sphere is a hollow sphere, and the inner wall surface of the sphere is composed of a white diffuse reflection surface coated with a white paint such as barium sulfate or titanium oxide. It is an optical component for taking in all the transmitted light or reflected light from a sample, which multi-reflects the light flux incident on the sphere, spatially integrates it, and measures the light uniformly.
A relative reflectance measuring device using such an integrating sphere has a reference sample (RS) and a measurement sample (D) outside the sample window (Wb) facing the light source window (Wr) of the integrating sphere (I). ) Are alternately set, the amount of reflected light is measured from the measured light taken out from the light measuring window (Wm), and the relative reflectance is obtained from the ratio of the amount of reflected light of the measurement sample (D) to the amount of reflected light of the reference sample (RS). (See, for example, FIG. 2 of Patent Document 1, Non-Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 61-225620

"Integrating sphere", UV TALK LETTER vol.5 (2010), Shimadzu Corporation, [online], [Search on May 15, 2017], Internet <URL: http://www.an.shimadzu.co .jp / uv / support / lib / uvtalk / uvtalk5 / basic.htm ＞ "Measurement of reflection of solid samples", UV TALK LETTER vol.12 (2013), Shimadzu Corporation, [online], [Search on May 15, 2017], Internet <URL: http: //www.an. shimadzu.co.jp/uv/support/lib/uvtalk/uvtalk12/basic.htm ＞

In the configuration of the relative reflectance measuring device using the conventional integrating sphere, if dust or dirt adheres to the reference sample set on the outside of the sample window, the measurement accuracy of the reference light deteriorates, so the reference light is used as a reference. The measurement accuracy of the relative reflectance obtained is reduced. Especially when it is used in the field, it becomes a big problem because dust and dirt easily adhere to the reference sample.

Therefore, in view of the above-mentioned situation, the present invention tries to solve the problem by increasing the measurement accuracy of the relative reflectance for a long period of time without deteriorating the measurement accuracy of the reference light due to the adhesion of dust and dirt to the reference sample. The point is to provide a relative reflectance measuring device using an integrating sphere and a calibration method thereof, which can be maintained and is particularly easy to use in the field.

The relative reflectance measuring device using the integrating sphere according to the present invention is a relative reflectance measuring device for obtaining the relative reflectance of the measurement sample with respect to the reference sample using the integrating sphere in order to solve the above-mentioned problem.
It has a shield body located outside the integrating sphere and has a shield body.
The integrating sphere is
Located in one plane passing through the center of the integrating sphere, a first window, provided with three windows of the second window and the third window,
The shield body, through the center, the integrating sphere is supported rotatably around the rotation axis is an axis perpendicular to the one plane,
By rotating the integrating sphere around the rotation axis by a predetermined angle with respect to the shield body, it is possible to switch between the measurement position of the integrating sphere and the calibration position of the integrating sphere.
At the measurement position
The first window is the sample window, the second window is a window for photometric, the third window is a window for the light source,
With the measurement sample set outside the sample window, light is incident into the integrating sphere from the light source window to irradiate the measurement sample, and the light is reflected from the photometric window to the outside of the integrating sphere. Take out the light,
At the calibration position
The first window becomes the photometric window , the second window becomes the light source window, and the third window is closed by the shield body.
Light is incident into the integrating sphere from the light source window to irradiate the inner wall surface of the integrating sphere, and reference light is taken out from the photometric window to the outside of the integrating sphere using the inner wall surface as the reference sample.
The relative reflectance of the measurement sample is obtained from the reflected light and the reference light (claim 1).
Further, the relative reflectance measuring device using the integrating sphere according to the present invention is a relative reflectance measuring device for obtaining the relative reflectance of the measurement sample with respect to the reference sample using the integrating sphere in order to solve the above-mentioned problem.
It has a shield body located outside the integrating sphere and has a shield body.
The integrating sphere is
It has three windows, a first window, a second window, and a third window, located in one plane passing through the center of the integrating sphere.
The shield body rotatably supports the integrating sphere around a rotation axis that passes through the center and is an axis along the one plane in which the second window and the third window are line-symmetrical.
By rotating the integrating sphere 180 ° around the rotation axis with respect to the shield body, it is possible to switch between the measurement position of the integrating sphere and the calibration position of the integrating sphere.
At the measurement position
The first window is a sample window, the second window is a photometric window, and the third window is a light source window .
With the measurement sample set outside the sample window, light is incident into the integrating sphere from the light source window to irradiate the measurement sample, and the light is reflected from the photometric window to the outside of the integrating sphere. Take out the light,
At the calibration position
The third window becomes the photometric window, the second window becomes the light source window, and the first window is closed by the shield body.
Light is incident into the integrating sphere from the light source window to irradiate the inner wall surface of the integrating sphere, and reference light is taken out from the photometric window to the outside of the integrating sphere using the inner wall surface as the reference sample.
The relative reflectance of the measurement sample is obtained from the reflected light and the reference light (claim 2).

According to these configurations, the integrating sphere is provided with three windows, the first window, the second window, and the third window, which are located in one plane passing through the center of the integrating sphere, and from the measurement position of the integrating sphere. At the calibration position of the integrating sphere in which the integrating sphere is rotated by a predetermined angle, two of the three windows become a metering window and a light source window, and the remaining one window is closed by a shield body. become. Thereby, at the calibration position of the integrating sphere, the reference light can be taken out from the photometric window to the outside of the integrating sphere using the inner wall surface of the integrating sphere as a reference sample.
Therefore, unlike the configuration of a conventional relative reflectance measuring device using an integrating sphere that obtains reference light with the reference sample set outside the sample window, dust and dirt do not adhere to the reference sample. The measurement accuracy of the reference light does not decrease.
Therefore, maintenance such as cleaning of the reference sample and storage and management of the reference sample are not required, and the measurement accuracy of the relative reflectance can be maintained high for a long period of time, so that the usability in the field can be significantly improved.

In addition, workability can be improved because it is possible to save the trouble of setting the reference sample on the outside of the sample window.
Furthermore, only dark current data can be obtained by simply turning off the light source at the calibration position of the integrating sphere.
Therefore, the dark-corrected reference light can be obtained only by subtracting the data with the light source turned off from the data with the light source turned on at the calibration position of the integrating sphere, so that the dark correction of the reference light becomes easy.
Further , according to the invention of claim 1 , since the calibration position and the measurement position of the integrating sphere can be switched only by rotating the integrating sphere by, for example, about 90 °, the relative reflectance measuring device becomes more compact. ..

Further, it is a more preferable embodiment that the calibration component is embedded in the shield body outside one of the three windows, which is closed by the shield body at the calibration position of the integrating sphere. (Claim 3 ).

According to such a configuration, since a calibration component coated with a white paint such as barium sulfate or titanium oxide is embedded in the outside of the window blocked by the shield body at the calibration position of the integrating sphere, the shield body is formed. Light entering the window blocked by is reflected by the calibration component.
Therefore, since the reference light is not affected by the shield body, a better reference light can be obtained.

Furthermore, it is an even more preferable embodiment to include a rotation operation stick that rotates integrally with the integrating sphere and rotates the integrating sphere around the rotation axis from the outside of the shield body (a further preferable embodiment). Claim 4 ).

According to such a configuration, the calibration position and the measurement position of the integrating sphere can be easily switched by the operation of rotating the rotation operation stick, so that the operability can be improved.

As a method for calibrating the relative reflectance measuring device using the integrating sphere according to the present invention, the relative reflectance measuring device using the integrating sphere according to any one of claims 1 to 4 is used.
With the reference light taken out from the photometric window to the outside of the integrating sphere using the inner wall surface of the integrating sphere as the reference sample at the calibration position of the integrating sphere, the integrating sphere is used from the photometric window at the measurement position of the integrating sphere. It is characterized in that the reflected light taken out of the above is calibrated (claim 5 ).

According to such a configuration, the integrating sphere is used by the reference light taken out from the photometric window from the photometric window using the inner wall surface of the integrating sphere as a reference sample at the calibration position of the integrating sphere using the relative reflectance measuring device. Since the reflected light taken out from the light measuring window to the outside of the integrating sphere is calibrated at the measurement position of, the same effect as that of the relative reflectance measuring device is obtained.

As described above, the relative reflectance measuring device using the integrating sphere and the calibration method thereof according to the present invention mainly exhibit the following effects.
(1) At the calibration position of the integrating sphere, the reference light can be taken out from the photometric window to the outside of the integrating sphere using the inner wall surface of the integrating sphere as the reference sample, so the reference sample is set outside the sample window. Since dust and dirt do not adhere to the reference sample as in the configuration of the relative reflectance measuring device using the conventional integrating sphere that obtains the reference light in the above, the measurement accuracy of the reference light does not deteriorate.
(2) Since maintenance such as cleaning of the reference sample and storage and management of the reference sample are not required, the measurement accuracy of the relative reflectance can be maintained high for a long period of time, so that the usability in the field can be greatly improved.
(3) Workability can be improved because it is possible to save the trouble of setting the reference sample on the outside of the sample window.
(4) Since only dark current data can be obtained by simply turning off the light source at the calibration position of the integrating sphere, simply subtracting the data with the light source turned off from the data with the light source turned on at the calibration position of the integrating sphere. Since the dark-corrected reference light can be obtained, the dark-corrected reference light can be easily dark-corrected.

It is a perspective view of the relative reflectance measuring apparatus which concerns on embodiment of this invention. It is also a rear view. It is a partial cross-sectional perspective view seen from the lower diagonal rear view. It is a partial vertical sectional front view which shows the measurement position of the integrating sphere. It is a partial vertical sectional front view which shows the calibration position of the integrating sphere. It is a partial vertical sectional front view which shows the example which embeds the calibration component in the shield body outside the window which is closed by the shield body at the calibration position of the integrating sphere. It is a vertical cross-sectional front view which shows the arrangement of three windows of a 1st window, a 2nd window and a 3rd window located in one plane passing through the center of an integrating sphere. It is a vertical cross-sectional front view which shows the modification of the rotation axis of the integrating sphere, (a) shows the measurement position of the integrating sphere, and (b) shows the calibration position of the integrating sphere.

Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

<Relative reflectance measuring device using an integrating sphere>
As shown in the perspective view of FIG. 1, the rear view of FIG. 2, the partial cross-sectional perspective view of FIG. 3, and the partial vertical cross-sectional front view of FIG. 4, the relative using the integrating sphere IS according to the embodiment of the present invention is used. The reflectance measuring device A obtains the relative reflectance of the measured sample MS with respect to the reference sample by using the integrating sphere IS.
In addition to the integrating sphere IS, the relative reflectance measuring device A includes a light source 4, a condensing lens 5 that collects light from the light source 4, a spectroscope 6, and the like.

<Integrating sphere>
In the integrating sphere IS, the spherical inner wall surface IW is composed of a white diffuse reflecting surface coated with a white paint such as barium sulfate or titanium oxide, and is located in one plane passing through the center of the integrating sphere IS. It is provided with three windows, W1, a second window W2, and a third window W3. That is, the centers of the first window W1, the second window W2, and the third window W3 are located in one plane passing through the center of the integrating sphere IS.
Here, the angle formed by the line segment connecting the center of the integrating sphere IS and the center of the first window W1 and the line segment connecting the center of the integrating sphere IS and the center of the second window W2 is 90 °, and the center of the integrating sphere IS. The angle formed by the line segment connecting the center of the second window W2 and the center of the integrating sphere IS and the line segment connecting the center of the third window W3 is 90 °.
The integrating sphere IS is rotatably supported by the outer shield body S around the rotation axis AR1 passing through the center of the integrating sphere IS, which is orthogonal to the one plane.

<Measurement position of integrating sphere>
In the measurement position MP of the integrating sphere IS shown in the front view of the partial vertical cross section of FIG. 4, the first window W1 is the sample window 1, the first window W2 is the photometric window 2, and the third window W3 is the light source window 3. With the measurement sample MS set outside the sample window 1, light is incident into the integrating sphere IS from the light source window 3 to irradiate the measurement sample MS, and from the light measuring window 2 to the outside of the integrating sphere IS. Take out the reflected light.
In the configuration in which the light collected by the condenser lens 5 is directly irradiated to the measurement sample MS at the measurement position MP of the integrating sphere IS, the light reflected by the measurement sample MS and entering the integrating sphere IS has a lot of information. Therefore, it is a more preferable embodiment.
Further, since the glass G is mounted on the support member 9 on the outside of the sample window 1, the inside of the integrating sphere IS is sealed from the outside even at the measurement position MP of the integrating sphere IS.

<Calibration position of integrating sphere>
At the calibration position CP of the integrating sphere IS shown in the front view of the partial vertical cross section of FIG. 5, in which the integrating sphere IS is rotated 90 ° around the rotation axis AR1 from the measurement position MP of the integrating sphere IS, the first window W1 is photometric. The window 2 is formed, the second window W2 becomes the window 3 for the light source, and the third window W3 is closed by the shield body S.
At the calibration position CP of the integrating sphere IS, light is incident into the integrating sphere IS from the light source window 3 to irradiate the inner wall surface IW of the integrating sphere IS, and the inner wall surface IW is used as the reference sample RS to irradiate the integrating sphere from the photometric window 2. Extract the reference light to the outside of the IS.

<Calibration method of relative reflectance measuring device using integrating sphere>
At the calibration position CP of the integrating sphere IS shown in FIG. 5, the inner wall surface IW of the integrating sphere IS is used as the reference sample RS, and the reference light taken out from the photometric window 2 to the outside of the integrating sphere IS is used to measure the integrating sphere IS shown in FIG. At the position MP, the reflected light taken out from the photometric window 2 to the outside of the integrating sphere IS is calibrated, and the relative reflectance of the measurement sample MS is obtained.

<Operation to rotate the integrating sphere>
As shown in FIGS. 1 to 3, a rotation operation stick 7 that rotates integrally with the integrating sphere IS and rotates the integrating sphere IS around the rotation axis AR1 from the outside of the shield body S is provided.
The stop piece 8 is connected to the rotation operation stick 7, and the stop piece 8 is rotated as shown by the arrow in FIG. 2 from the angle (FIGS. 2 and 3) at which the stop piece 8 is in contact with the first limit switch LS1. The rotation operation piece 7 can be rotated with respect to the angle at which the stop piece 8 is hit by the second limit switch LS2 by rotating the motion operation stick 7.

At the angle (FIGS. 2 and 3) where the stop piece 8 is in contact with the first limit switch LS1, the measurement position MP (FIG. 4) of the integrating sphere IS is set, and the stop piece 8 is set to the second limit switch LS2. At the stopped angle, it becomes the calibration position CP (FIG. 5) of the integrating sphere IS.
By rotating the rotation operation stick 7 in this way, the calibration position CP and the measurement position MP of the integrating sphere IS can be easily switched, so that the operability can be improved.
When the stop piece 8 is hit by the first limit switch LS1, the first limit switch LS1 is turned on, and when the stop piece 8 is hit by the second limit switch LS2, the second limit switch LS2 is turned on. Since it is turned on, by combining the signals of the limit switches LS1 and LS2 on both sides, the measurement position MP of the integrating sphere IS, the calibration position CP of the integrating sphere IS, and their intermediate positions can be discriminated.

<Example of embedding a calibration component to shield body>
As shown in the front view of the partial vertical cross section of FIG. 6, the calibration component 10 may be embedded in the shield body S outside the third window W3 which is closed by the shield body S at the calibration position CP of the integrating sphere IS. This is a preferred embodiment. The calibration component 10 is coated with a white paint such as barium sulfate or titanium oxide, similarly to the inner wall surface IW of the integrating sphere IS.
By embedding the calibration component 10 in the shield body S, the light entering the window (third window W3 in the present embodiment) blocked by the shield body S at the calibration position CP of the integrating sphere IS is reflected by the calibration component 10. Therefore, since the reference light is not affected by the shield body S, a better reference light can be obtained.

<Arrangement of three windows>
In the vertical cross-sectional front view of FIG. 7 showing the integrating sphere IS of the partial vertical cross-sectional front view of FIGS. 4 to 6, the line segment connecting the center of the integrating sphere IS and the center of the first window W1 and the center of the integrating sphere IS. Let α be the angle formed by the line segment connecting the center of the second window W2 and the center of the second window W2, and connect the center of the integrating sphere IS and the center of the third window W3 with the line segment connecting the center of the integrating sphere IS and the center of the second window W2. Let β be the angle formed by the line segment.
In the description of FIGS. 4 to 6, an example in the case of α = β = 90 ° is shown.

In the present invention, by rotating the integrating sphere IS around the rotation axis AR1 between the measurement position MP of the integrating sphere IS and the calibration position CP of the integrating sphere IS, the measurement position MP of the integrating sphere IS has three. The windows W1, W2 and W3 become the sample window 1, the light measuring window 2 and the light source window 3, and at the calibration position CP of the integrating sphere IS, the two windows W1 and W2 become the light measuring window 2 and the light source window 3. Therefore, the remaining one window W3 may be in a state of being blocked by the shield body S.
Therefore, the arrangement of the three windows W1, W2, W3 in the present invention needs to be α = β, but is not limited to α = β = 90 °.

When α = β = 120 °, the third window W3 returns to the original position of the first window W1 when the integrating sphere IS is rotated by 120 ° around the rotation axis AR1 from the measurement position MP of the integrating sphere IS. Since it will come, the third window W3 will not be blocked by the shield body S.
Therefore, the case of α = β = 120 ° is excluded from the present invention.
In the present invention, when the integrating sphere IS is rotated by an angle α (β) around the rotation axis AR1 from the measurement position MP of the integrating sphere IS at α = β <120 °, the third window W3 is the shield body S. It should be in a state of being blocked by.

<Modification example of rotating shaft>
The vertical sectional front views of FIGS. 8A and 8B are explanatory views showing the integrating sphere IS taken out, and show a modified example in which the rotation axis AR2 different from the integrating sphere IS of FIGS. 1 to 7 is adopted. ing.
The centers of the first window W1, the second window W2, and the third window W3 are located in one plane passing through the center of the integrating sphere IS, and the rotation axis AR2 is a line of the second window W2 and the third window W3. It is an axis along the one plane that becomes symmetrical.

In the measurement position MP of the integrating sphere IS shown in FIG. 8A, the first window W1 is the sample window 1, the second window W2 is the photometric window 2, and the third window W3 is the light source window 3.
In the calibration position CP of the integrating sphere IS shown in FIG. 8B in which the integrating sphere IS is rotated 180 ° around the rotation axis AR2 from the measurement position MP of the integrating sphere IS, the third window W3 becomes the photometric window 2. As a result, the second window W2 becomes the light source window 3, and the first window W1 is closed by the shield body S.

According to the relative reflectance measuring device A using the integrating sphere IS as described above, the first window W1, the second window W2, and the third window W3 located in one plane passing through the center of the integrating sphere IS. In the calibration position CP of the integrating sphere IS in which three windows are provided in the integrating sphere IS and the integrating sphere IS is rotated by a predetermined angle from the measurement position MP of the integrating sphere IS, two of the three windows W1 to W3 (times). In the case of the moving axis AR1, W1 and W2, in the case of the rotating axis AR2, W3 and W2) become the metering window 2 and the light source window 3, and the remaining one window (W3 in the case of the rotating axis AR1). In the case of the rotating shaft AR2, W1) is closed by the shield body S. Thereby, at the calibration position MP of the integrating sphere IS, the reference light can be taken out from the photometric window 2 to the outside of the integrating sphere IS using the inner wall surface IW of the integrating sphere IS as the reference sample RS.
Therefore, unlike the configuration of the relative reflectance measuring device using the conventional integrating sphere that obtains the reference light with the reference sample RS set on the outside of the sample window 1, dust and dirt do not adhere to the reference sample RS. Therefore, the measurement accuracy of the reference light does not decrease.
Therefore, maintenance such as cleaning of the reference sample RS and storage and management of the reference sample RS are not required, and the measurement accuracy of the relative reflectance can be maintained high for a long period of time, so that the usability in the field can be greatly improved. ..

In addition, workability can be improved because it is possible to save the trouble of setting the reference sample RS on the outside of the sample window 1.
Furthermore, only dark current data can be obtained by simply turning off the light source at the calibration position CP of the integrating sphere IS.
Therefore, the dark-corrected reference light can be obtained only by subtracting the data with the light source turned off from the data with the light source turned on at the calibration position CP of the integrating sphere IS, so that the dark correction of the reference light becomes easy.
Further, in the configuration in which the integrating sphere IS is rotated around the rotation axis AR1, the calibration position CP and the measurement position MP of the integrating sphere IS can be switched by simply rotating the integrating sphere IS by, for example, about 90 °. The relative reflectance measuring device A becomes more compact.

1 Sample window 2 Photometric window 3 Light source window 4 Light source 5 Condensing lens 6 Spectrometer 7 Rotation operation rod 8 Stop piece 9 Support member 10 Calibration component A Relative reflectance measuring device AR1, AR2 Rotation axis CP calibration Position G Glass IS Integrating sphere IW Inner wall surface LS1 1st limit switch LS2 2nd limit switch MP Measurement position MS Measurement sample RS Reference sample S Shield body W1 1st window W2 2nd window W3 3rd window

Claims (5)

A relative reflectance measuring device that obtains the relative reflectance of a measurement sample with respect to a reference sample using an integrating sphere.
It has a shield body located outside the integrating sphere and has a shield body.
The integrating sphere is
Located in one plane passing through the center of the integrating sphere, a first window, provided with three windows of the second window and the third window,
The shield body, through the center, the integrating sphere is supported rotatably around the rotation axis is an axis perpendicular to the one plane,
By rotating the integrating sphere around the rotation axis by a predetermined angle with respect to the shield body, it is possible to switch between the measurement position of the integrating sphere and the calibration position of the integrating sphere.
At the measurement position
The first window is the sample window, the second window is a window for photometric, the third window is a window for the light source,
With the measurement sample set outside the sample window, light is incident into the integrating sphere from the light source window to irradiate the measurement sample, and the light is reflected from the photometric window to the outside of the integrating sphere. Take out the light,
At the calibration position
The first window becomes the photometric window , the second window becomes the light source window, and the third window is closed by the shield body.
Light is incident into the integrating sphere from the light source window to irradiate the inner wall surface of the integrating sphere, and reference light is taken out from the photometric window to the outside of the integrating sphere using the inner wall surface as the reference sample.
The relative reflectance of the measurement sample is obtained from the reflected light and the reference light.
Relative reflectance measuring device using an integrating sphere. A relative reflectance measuring device that obtains the relative reflectance of a measurement sample with respect to a reference sample using an integrating sphere.
It has a shield body located outside the integrating sphere and has a shield body.
The integrating sphere is
Located in one plane passing through the center of the integrating sphere, a first window, provided with three windows of the second window and the third window,
The shield body rotatably supports the integrating sphere around a rotation axis that passes through the center and is an axis along the one plane in which the second window and the third window are line-symmetrical.
By rotating the integrating sphere 180 ° around the rotation axis with respect to the shield body, it is possible to switch between the measurement position of the integrating sphere and the calibration position of the integrating sphere.
At the measurement position
The first window is the sample window, the second window is a window for photometric, the third window is a window for the light source,
With the measurement sample set outside the sample window, light is incident into the integrating sphere from the light source window to irradiate the measurement sample, and the light is reflected from the photometric window to the outside of the integrating sphere. Take out the light,
At the calibration position
The third window becomes the photometric window , the second window becomes the light source window, and the first window is closed by the shield body.
Light is incident into the integrating sphere from the light source window to irradiate the inner wall surface of the integrating sphere, and reference light is taken out from the photometric window to the outside of the integrating sphere using the inner wall surface as the reference sample.
The relative reflectance of the measurement sample is obtained from the reflected light and the reference light.
Relative reflectance measuring device using an integrating sphere. A calibration component is embedded in the shield body outside the third window or the first window, which is closed by the shield body at the calibration position of the integrating sphere.
The relative reflectance measuring device using the integrating sphere according to claim 1 or 2. It is provided with a rotation operation stick that rotates integrally with the integrating sphere and rotates the integrating sphere around the rotation axis from the outside of the shield body.
The relative reflectance measuring device using the integrating sphere according to any one of claims 1 to 3. Using the relative reflectance measuring device using the integrating sphere according to any one of claims 1 to 4, the relative reflectance measuring device is used.
With the reference light taken out from the photometric window to the outside of the integrating sphere using the inner wall surface of the integrating sphere as the reference sample at the calibration position of the integrating sphere, the integrating sphere is used from the photometric window at the measurement position of the integrating sphere. It is characterized by calibrating the reflected light taken out of the
A method of calibrating a relative reflectance measuring device using an integrating sphere.

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