JPS6388411A - Integrating sphere apparatus - Google Patents

Abstract

PURPOSE:To obtain a stability against changes in the light source or the like even with a single flux type as done with a double flux type, by dividing a part of light flux incident into an integrating sphere by a light flux splitting means such as stationary half-mirror to receive light with a silicon photocell. CONSTITUTION:A sample X is st in contact with a window provided at a position where an incident light flux of an integrating sphere I hits it directly, a light flux emitted from a spectroscope M is made to come into the sphere I and a part thereof is to fall into a silicon photocell 3. An output of the cell 3 is converted 4 into a control signal and inputted into a negative high voltage generation circuit 5, and output voltage of which 5 is applied to a diode of a photoelectric multiplier tube P to control the sensitivity of the tube P. Thus, as only one light flux is made come into the sphere I, the construction of an optical system is very simple, while light incident into the sphere I is divided 2 and monitored before the incidence thereof I thereby enabling automatic compensation for the changes in the light source 1. In addition, as the light flux being incident into the sphere I is single, restriction or the like of the geometric size of the sample X can be minimized with a larger freedom of the position of the sphere I.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a photometric device using an integrating sphere for use in a spectrophotometer or the like.

Conventional technology When measuring the transmittance or reflectance of a C material, the sample does not scatter light and has a flat surface, and all the light transmitted or reflected by the sample enters the light receiving element and is received by the sample. If the incident position of the light beam on the light-receiving surface of the element, the cross-sectional shape of the incident light beam, and the light intensity distribution do not change even when the sample is moved or the sample is changed, the light transmitted or reflected from the sample can be made to directly enter the light-receiving element. However, samples with non-flat surfaces, light-diffusing samples,
etc., the light beam transmitted or reflected by the sample spreads out, making it impossible to make all of the light transmitted or reflected from the sample enter the photodetector, and when replacing the sample, the position and shape of the incident light beam on the photodetector may change. etc. change, so it is necessary to use an integrating sphere to eliminate errors caused by these factors.

However, since the integrating sphere photometer has a lot of loss of light energy,
A photoelectron intensifier tube is usually used as a photodetector, and in this case, a sample-control side illumination method as shown in FIG. 4 has conventionally been used. In Fig. 4, 1 is an integrating sphere, and the speed of light emitted from the spectrometer M is split into two beams S and R by a rotating mirror BS, which are made to enter the integrating sphere I alternately from two directions, and the light beams emitted from the integrating sphere are is received by one photomultiplier tube P. Of the two divided beams, R is a reference beam, and S is a sample beam, and the sample X is placed in the optical path of this sample beam.

The output of the photomultiplier tube P is differentiated into that for the reference light beam and that for the sample light beam, and the voltage applied to the photomultiplier tube is controlled so that the output for the reference light is constant.

Problems to be Solved by the Invention The above-mentioned conventional integrating sphere photometer using the one-sample comparison example sentence type method is a three-beam type, so its optical system configuration is more complex than that of a single-beam type photometer. Furthermore, since the positions and directions of the three beams of light incident on the integrating sphere are fixed, the integrating sphere cannot be moved freely. Even in optical measurements, there is a problem in that it is very difficult to measure samples where both surfaces are not parallel and the direction of transmitted light changes significantly, and there are significant restrictions on the applicable samples and measurement methods.

Since the present invention is a single-beam type, it has the same stability against light source fluctuations as a three-beam type, and because it is a single-beam type, there are fewer restrictions on applicable sample shapes, measurement methods, etc. This is what we are trying to provide.

20 Means for Solving Problems The light beam incident on the integrating sphere is split into parts by a light beam splitting means such as a static semi-transparent mirror, and the light is received by a silicon photocell, and the output is used to divide the light beam into the sample. The voltage applied to the photomultiplier tube, which receives the light emitted from the integrating sphere, is controlled by monitoring.

Ho0 effect Conventional three-beam integrating sphere photometers monitor the reference light by measuring it through an integrating sphere for sample measurement, which requires the use of the sentence method, which complicates the configuration of the optical system. However, in the present invention, the reference light does not pass through the integrating sphere for measuring the sample light, and is measured by a photometric element separate from the photomultiplier tube for measuring the sample light, so there is no need to use the sentence method. The configuration of the optical system is simplified, and the structure is almost the same as the single beam method.However, since the sample incident light is monitored, fluctuations in the light source are compensated for, and highly accurate measurements are possible. becomes.

Embodiment FIG. 1 shows an embodiment of the present invention. The figure shows the case of measuring the diffuse reflectance of a sample. 1 is a light source, M is a spectroscope, ■ is an integrating sphere, and P is a photomultiplier tube that receives light emitted from the integrating sphere. The sample X is placed in contact with a window provided at a position where the incident light beam of the integrating sphere I directly hits. The emitted light beam from the spectrometer M directly enters the integrating sphere (2), but a semi-transparent mirror 2 is inserted into the optical path of this incident light beam, and a part of the light emitted from the spectrometer is made to enter the silicon photocell 3. The output of the silicon photocell 3 is converted into a control signal for the negative high voltage generation circuit 5 through a suitable input/output conversion circuit 4, and is input to the negative high voltage generation circuit 5. The output voltage of the negative high voltage generating circuit 5 is applied to the dynode of the photomultiplier tube (2), and the sensitivity of the photomultiplier tube P is controlled.

If the relationship between the applied voltage V and the sensitivity (gain) A of the photomultiplier tube is A = f (V), then the sensitivity of the photomultiplier tube P can be kept constant regardless of changes in the output i of the silicon photocell. teeth,
The applied voltage V may be determined by the relationship V=f (α/i) (1). As the input-output conversion circuit 4, a function generation circuit whose input-output relationship is given by equation (1) may be used, and a logarithmic conversion circuit can be approximately used as such a function generation circuit.

The procedure for measuring the spectral diffuse reflectance of sample X using the configuration shown in FIG. 1 is as follows. First, a standard sample is placed in place of sample X in the figure, and the output 1o (λ) of the photomultiplier tube P is stored in memory along with the wavelength of the light emitted from the spectrometer M. Next, place the sample to be measured X at position X in the figure and do the same as above to output I
(λ) can be found using notes.

FIG. 2 shows a second embodiment of the invention. In this embodiment, the integrating sphere I is provided with a window W1 for placing the sample on the part directly hit by the incident light on the integrating sphere, and a compensation window W2 is provided at a position where the incident light does not enter and is symmetrical to Wl with respect to the photodetector. It is. W3 is a window for light emission, and a photomultiplier tube P is placed therein. The rest of the overall configuration is the same as the embodiment shown in FIG.

When measuring the diffuse reflectance in this example, the reflectance is 100
When measuring the % line Io (λ), a standard white board is placed in the window W1, and the window W2 is covered with the sample X to be measured. Next, when measuring the reflected light I(λ) of the sample to be measured, the sample to be measured X is placed in the window W1, and the compensation window W2 is covered with a standard white board. In the embodiment shown in Fig. 1, errors due to multiple reflections between the inner surface of the integrating sphere and the sample cannot be eliminated, but if this is done, IO(λ)
Since the inner surface of the integrating sphere is kept optically equivalent both during measurement and when (λ) is measured, the error that occurs in the embodiment shown in Fig. 1 is eliminated because the device is of a single beam type. More accurate measurements can be made than the embodiment shown in FIG.

FIG. 3 shows a third embodiment of the invention. This example shows a case for transmittance measurement. X is the sample placed in front of the light entrance window of integrating sphere I. The same reference numerals are given to the parts corresponding to those in the embodiment shown in Figure 1 of the envoy, and their explanation will be omitted.

Although the sample for transmittance measurement is not limited to a flat plate with both sides parallel to each other, in this example, the sample to be measured Even if the shape of the cross section of the light beam incident on the inner surface of the integrating sphere differs depending on the case where the sample X is placed, the error due to this is removed by the integrating sphere I. Even when the sample is in the shape of a prism or specular reflection measurement, and the directions of the incident light and the light emitted from the sample are significantly different, the integrating sphere can be rotated around the sample set position. It can be easily measured by keeping it as . Furthermore, if the distance from the sample to the integrating sphere can be changed, even large samples can be easily measured. In the conventional two-beam type device, the contrast light must be incident on the integrating sphere, so the position of the integrating sphere is constrained by the optical path of the contrast light, and the position of the integrating sphere is fixed. This is something that cannot be done.

G. Effect The integrating sphere device of the present invention has the above-described configuration, and since only one beam of light is incident on the integrating sphere, the configuration of the optical system is as simple as that of a single beam type device. Since the light incident on the integrating sphere is divided and monitored before it enters the integrating sphere, it can automatically compensate for variations in the light source, just like the three-beam type, and the light beam incident on the integrating sphere is only a single beam. Therefore, there is a large degree of freedom in the position of the integrating sphere, and there are fewer restrictions on the shape and size of the sample or on the measurement method (for example, measuring the reflectance by changing the incident angle).

[Brief explanation of the drawing]

Fig. 1 is a plan view of an embodiment of the present invention, Fig. 2 is a plan view of essential parts of a second embodiment of the invention, Fig. 3 is a plan view of a third embodiment of the invention, Fig. 4 is a plan view of a conventional example. I...integrating sphere, M...spectroscope, X...sample, 1.
...Light source, 2...Semi-transparent mirror, 3...Silicon photocell, 4...Input/output conversion circuit, 5...Negative high voltage generation circuit. Agent Patent Attorney Kosuke Agata s1 diagram

Claims (1)

[Claims] Photoelectron multiplication that splits a single beam of light incident on the integrating sphere by a static beam splitting means, makes the split beam enter a photometric element for monitoring, and receives the light emitted from the integrating sphere using the output of this photometric element. An integrating sphere device that controls the voltage applied to the tube.