JPH0650261B2 - Spectrophotometer using integrating sphere - Google Patents

Description

TECHNICAL FIELD The present invention relates to a two-beam spectrophotometer capable of measuring transmitted light and reflected light of a sample by using an integrating sphere.

(B) Prior art When measuring the transmitted light of a transparent sample or the reflected light of an arbitrary sample by using an integrating sphere device with a spectrophotometer, the integrating sphere device is expensive, and therefore the transmitted light is also measured by one integrating sphere. It is desirable to be able to measure reflected light as well.

Therefore, an integrating sphere as shown in FIG. 4 has been conventionally used. In this figure, I is an integrating sphere, R is a reference light beam of the two-beam spectrophotometer, and S is a sample light beam. The integrating sphere I has a reference light incident window Wr, a sample light incident window Ws, and a reflected light measurement. The window Wd for setting the sample, the window Wb for setting the standard reflection plate, and the measurement light extraction window Wm are provided. In the case of reflected light measurement, the sample to be measured is set in the window Wd, and the reflection standard plate RS such as BaSO4 is set in the window Wb. In the case of transmitted light measurement, the sample L is set outside the window Ws, and the two windows Wd and Wb are both covered by the reflection standard plate RS. Wb is useful not only for the standard reflector set in the case of reflected light measurement, but also in making the sample light and the reference light optically identical conditions in the case of transmitted light measurement.

When the transmitted light is measured using such an integrating sphere, the sample light is measured without placing the sample to obtain the measurement output of 100% transmittance, and then the sample is placed to measure the sample transmitted light. I do. Here, when the sample is like a plane parallel plate, the sample light beam goes straight through the sample and enters the reflection standard plate set in the window Wd, so the condition of the sample light in the integrating sphere is The same as when measuring 100% transmittance, and no error occurs. In the case where the transmittance of the sample L such as a lens is measured as shown in the figure, the luminous flux of the sample directly enters only the reflection standard plate set in the window Wd of the integrating sphere when measuring the transmittance of 100%. Since the sample transmitted light flux converges once and then diverges as shown in the figure, part of the sample transmitted light is incident on the reflection standard plate set in the window Wd in the integrating sphere, and part of the light is transmitted to the edge of the window Wd. It is reflected and the rest is incident on the inner wall surface of the integrating sphere. Since the reflectance differs between the inner wall surface of the integrating sphere and the reflection standard plate set in the window Wd, a part of the light transmitted through the sample is incident on the inner wall surface of the integrating sphere. For example, when the inner wall surface of the integrating sphere has a lower reflectance than the reflection standard plate, the transmittance of the sample is apparently lower than the transmittance of 100%. This difference in reflectance is about 0.5 to 2.5%, which changes over time. Further, the reflection standard plate set in the window Wd does not become a tangential plane of the inner wall surface of the integrating sphere, and there is a step at the edge of the window Wd, and the sample transmitted light incident on the stepped portion receives the reflection standard plate and the integrating sphere. The reflection is very different from the reflection on the inner wall surface, which also causes an error. The above-mentioned phenomenon is not limited to the case where the sample is a lens, but also occurs in a sample having a light-scattering property, a prismatic shape, a distorted shape, or the like in which a light beam spreads or is deflected.

The above-mentioned problem is to prepare two integrating sphere devices, one for measuring reflected light and one for measuring transmitted light.
It is sufficient to omit d and Wb, but this would be very expensive to prepare for the measurement using the integrating sphere.

(C) Problems to be Solved by the Invention The present invention is intended to eliminate the above-mentioned error causes when the integrating sphere device is commonly used for transmitted light measurement and reflected light measurement.

D. Means for solving the problem As shown in FIG. 1, the window Wd of the integrating sphere in FIG. 4 is eliminated, and the reference light signal and the sample light signal can be exchanged in the photometric circuit. That is, the photometric signal for the light flux R is the reference light signal and the photometric signal for the light flux S is the sample light signal, or the photometric signal for the light flux R is the sample light signal and the light flux S
It is possible to switch whether to use the photometric signal for the reference light signal.

(E) When measuring transmitted light, the sample L is placed in the sample light beam S as shown in FIG. Since the side of the integrating sphere I opposite to the sample light incident window Ws is the inner wall surface of the integrating sphere, the sample light incident on the integrating sphere is also shown in the drawing in which the sample is placed and the luminous flux is expanded even at the time of 100% transmittance measurement. The conditions for the internal reflection of the integrating sphere are the same, and the above-mentioned error cause no longer exists. Next, in the case of the reflected light measurement, the sample D may be set in the window Wb as shown in FIG. 2, and the signal processing may be performed using the light beam R as the sample light and S as the reference light.

F. Embodiment An embodiment of the present invention is shown in FIGS. I is an integrating sphere, and the figure shows a horizontal section. A window Wb for setting the sample is provided on the opposite side of the two light incident windows Ws and Wr and Wr, and the measurement light extraction is performed on the upper surface of the integrating sphere as shown by the dotted line. Window Wm
Is provided, and the light receiving element P (see FIG. 3) is arranged to receive the light emitted from this Wm. In FIG. 3, M is a monochromator, and the light flux emitted from the monochromator is split into two light fluxes R and S by a beam splitter BS and made incident on an integrating sphere I. Sw is a switch that performs a switching operation in synchronization with the rotation of the beam splitter BS, and contacts the contact 1 side at the timing when the light flux R is incident on the integrating sphere, and contacts 2 at the timing when the light flux S is incident on the integrating sphere. To come into contact with. SC is a manual switching switch, and a connection shown by a solid line arrow and a connection shown by a dotted line can be switched and selected. And in the case of the connection of the solid line arrow, the luminous flux R
The photometric output of is input to the comparator C from the switch Sw through the contact 1, is compared with the reference level by the comparator C, and the difference between the two is input to the high voltage generation circuit H, and the high output voltage of H is received by the light receiving element P (photoelectron multiplication). The sensitivity of the light receiving element P is controlled so that the photometric signal of the light flux R becomes constant by being fed back to the tube dynode). On the other hand, the photometric output of the luminous flux S is input to the signal processing circuit N from the switch Sw via the contact 2. Further, when the switch SC is switched to the connection state shown by the dotted line, the sensitivity control of the light receiving element P is performed so that the photometric output of the luminous flux S becomes constant, and the photometric output of the luminous flux R is input to the signal processing circuit N. It will be.

Transmittance Measurement When performing the transmittance measurement with the above-described apparatus, the sample L is placed in front of the window Ws of the integrating sphere as shown in FIG. At this time, the reflection standard plate RS is provided on the window Wb.
To set. Further, the switch SC is switched to the connection shown by the solid arrow in FIG. In this case, the light flux R acts as the reference light flux to control the sensitivity of the light receiving element P as described above, and the photometric output of the light flux S is input to the data processing circuit N. In order to obtain the transmittance, first, the sample L is not placed, the light beam S is directly incident on the integrating sphere I, and the photometric output of the light beam S at that time is set to 100% transmittance To, and then the sample L is placed. Letting Ts be the photometric output of the luminous flux S of, the transmittance is given by Ts / To × 100%.

Reflected Light Measurement In this case, the switch SC is switched to the connection shown by the dotted line in FIG. 3, and the reflection standard plate RS and the sample D are alternately set in the window Wb. As described above, when the switch SC is switched to the connection shown by the dotted line, the light flux S acts as a reference light flux and acts on the sensitivity control of the light receiving element P, and the light flux R acts as a sample light flux and enters from the window Wr of the integrating sphere I. Reflection standard plate RS set in window Wb
Alternatively, the sample D is irradiated.

According to the present invention, as described above, it is economical to use one integrating sphere for both transmitted light measurement and reflected light measurement, and it is economical, and the opposite side of the sample light incident window in the case of transmitted light measurement in the integrating sphere. Since there is no window like the conventional example, there is no error cause, and the light beam after passing through the sample diverges, and even if it is a sample of any shape that deviates or deflects, or a light scattering sample is transmitted with high accuracy. Can measure light.

Although the window Wr is provided so that the light flux R is obliquely incident on the surface of the window Wb of the integrating sphere I in the above-described embodiment, it goes without saying that it may be vertically incident. .

[Brief description of drawings]

FIG. 1 is a horizontal section in a transmitted light measurement mode of an integrating sphere in one embodiment of the present invention, FIG. 2 is a horizontal section in a reflected light measurement mode, and FIG. 3 is a block diagram showing the entire structure of the same. FIG. 6 is a horizontal sectional view of an integrating sphere in a conventional example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G01N 21/59 Z 7370-2J

Claims (1)

[Claims] 1. A two-beam spectrophotometer, wherein two light-incident windows are provided on an integrating sphere so that the respective light beams are incident on the integrating sphere in correspondence with the two light-beams of the spectrophotometer, and these two light-incident windows. A window for setting the sample for reflection measurement at a position where the light flux incident from one side hits, and a window for extracting light to the light receiving element at another position are provided.
The integrating sphere is configured so that the part where the light beam incident from the other light incident window hits is the inner wall surface of the integrating sphere, and the photometric circuit uses the photometric signals of the two light beams as the reference light signal and which is the sample light. A spectrophotometer using an integrating sphere, which is provided with a switching means for switching to a signal.