JPS63266321A - Spectral measurement method and fourier transform type spectrophotometer - Google Patents

Abstract

PURPOSE:To eliminate the need for mechanical driving parts and to facilitate handling such in assurance of measurement accuracy by passing incident light successively through a polarizer, a substrate made of an electrooptic material with electrodes, an analyzer and a condenser lens. CONSTITUTION:The voltage to be impressed to the electrodes 11 is controlled by an optical shutter control circuit 9 to control the quantity of the light transmitted through the optical shutter 12. A condenser lens 5 is placed on the side of the optical shutter 12 opposite to the face where incident light 1 is received. The light condensed after transmitting the optical shutter 12 is converted to an electric signal by a light quantity detector 6. This electric signal is inputted via an A/D converter 7 to a Fourier transform computing device 8, by which the spectrum of the Fourier-transformed incident light is obtd. together with the voltage value impressed to the optical shutter 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a measuring instrument for spectroscopic analysis, and more particularly to a spectrum measuring method using Fourier transform and a Fourier transform type spectrophotometer.

[Conventional technology]

Spectrum measurement method using Fourier transform was published in Japanese Patent Application Laid-open No. 6
It is known from Japanese Patent Application Laid-open No. 1-31930, Japanese Patent Application Laid-Open No. 61-65122, Japanese Patent Application Laid-open No. 149832-1983, etc.

Fourier spectroscopy has the advantage of higher energy utilization efficiency than spectroscopic measurements using dispersive elements.

However, it is necessary to use a Michelson interferometer, and all of the above prior art techniques used this interferometer.

[Problem that the invention seeks to solve]

To use a Michelson interferometer, it is necessary to ensure the accuracy of the optical path length because it has a mechanically driven part.

Therefore, if a laser measuring device or the like is used, the system becomes complicated. Furthermore, since the interferometer is a mechanical device, there is a limit to the number of measurements per unit time, and it takes time to ensure the mechanical accuracy of the measurement system each time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spectrum measuring method and a Fourier transform spectrophotometer that do not require mechanically driven parts and are therefore easy to handle and ensure measurement accuracy.

[Means for solving problems]

The above object is achieved by transmitting light through an electro-optic material substrate provided with electrodes.

The first invention of the present application is a spectral measurement method in which incident light is sequentially passed through a polarizer, a substrate made of electro-optic material with electrodes, an analyzer, and a condensing lens. It is characterized in that it performs a Fourier transform calculation based on the total transmitted light intensity from the optical lens and outputs the transmitted light intensity of a predetermined wave number corresponding to the voltage applied to the substrate.

The second invention of the present application is a Fourier transform spectrophotometer, which includes an optical shutter using an electro-optic effect, a circuit for controlling the amount of transmitted light of the shutter, and a received light amount detection device for detecting the transmitted light of the shutter. The apparatus is characterized in that it includes an arithmetic unit that performs Fourier transform on the output of this apparatus, and that the optical shutter is formed of an electro-optic material substrate with electrodes.

It is convenient to arrange the electrodes on the electro-optical material substrate by using a combination of +knee comb teeth, and as long as it does not adversely affect the measurement error of the transmitted light intensity, it is better to keep the electrode spacing uniform and as narrow as possible to provide a larger electric field. It's advantageous. Further, the electrode may be disposed on the surface of the electro-optical material substrate, or may be partially or entirely buried in the thickness direction of the electrode.

[Effect]

The transmitted light intensity of the optical shutter using the electro-optic effect is
The voltage V applied to the shutter has the following form.

I(V)=/Ih-5in"(k-gV")dk
-a) is the wave number of transmitted light, which is the reciprocal of the wavelength. Also I
h is the intensity of transmitted light at the wave number, and g is a constant determined by the shape, material, etc. of the optical shutter.

- n is 1 when using the next electro-optic effect, that is, the Pockels effect, and n is 2 when using the Kerr effect, which is the second-order electro-optic effect.

From the above equation...(2) When v=O, I(0)=/Ihdk From the formula (2)...(3) Set x=2gV'' and perform Fourier transform on the second term on the right side of equation (3) Then, Ib is derived. Since Is= is proportional to the spectral intensity of the incident light on the optical shutter, change the applied voltage to the optical shutter, measure the applied voltage characteristics of the transmitted light intensity, and perform Fourier transformation on it. The spectrum of the incident light is obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

A polarizer 2 is placed on the maximum power side of the incident light 1, and an electro-optical material substrate 3 is placed behind it. Furthermore, there is an analyzer 4 behind it. Condensing lenses 5 are sequentially provided, and a light amount detector 6 is arranged on the output light side.

The polarizer 2 and the analyzer 4 are positioned so that their respective polarization directions are orthogonal. Further, the direction of the electric field applied to the electro-optical material substrate 3 is arranged at an angle of 45° with the polarization direction of the polarizer.

As shown in the figure, the optical axes from at least the polarizer 1 on the incident light side to the light receiving section of the light amount detector 6 should be in the same straight line.

The electro-optic material used for the electro-optic material substrate 3 is, for example, lithium tantalate (L i T a O δ), lithium niobate A (LiNbOa), so-called PLZT (Pbt-x
Lax(Zrt-yT'1y)t-x8Og).

The output side terminal of the light amount detector 6 and the A/D converter 7 are electrically connected, and the output side of the A/D converter 7 and the Fourier transform calculation device 8 are electrically connected, and the Fourier transform calculation device The output side of 8 is electrically connected to the optical shutter control circuit 9 . Another Fourier transform calculation unit! ! ! On the output side of 8, there is an output device M1 for the spectrum (Ih value) or various data using this.
Add 0.

Two lead wires are taken out from the optical shutter control circuit 9 and connected to the + and - electrodes 11 on the electro-optical material substrate 3.

Polarizer 2. Substrate made of electro-optic material with electrode 11 3. The analyzer 4 constitutes an optical shutter 12.

Note that reference numeral 13 indicates an optical axis.

The optical shutter control circuit 9 controls the voltage applied to the electrode 11 of the electro-optic material substrate 3 to control the amount of light transmitted through the optical shutter 12. In the optical shutter 12, a condensing lens 5 is placed on the side opposite to the surface that receives the incident light 1, and the light transmitted through the optical shutter 12 and condensed is converted into an electrical signal by a light amount detector 6. This electric signal is converted into a digital signal by the A/D converter 7, and then is processed by the Fourier transform calculation device ff.
8 and is Fourier-transformed together with the voltage value applied to the optical shutter 12 to obtain the spectrum of the incident light.

In the above procedure, the Fourier transform procedure is as described in the [Operation] section above.

In short, the Fourier transform calculation device records A/D converted transmitted light amount data, electrically controls the optical shutter control circuit 8, performs calculations such as Fourier transform, and performs output equipment! 10.

According to this embodiment, since the mechanical drive part of the spectrometer is eliminated, the arrangement is simple and the accuracy is improved.

〔Effect of the invention〕

According to the present invention, it is possible to eliminate mechanically driven parts in a Fourier transform spectrophotometer, so calibration is easy and there is no need to incorporate a calibration device, so the system can be made smaller and faster. spectroscopic measurements are possible.

[Brief explanation of drawings]

The drawing is a device layout diagram of a Fourier transform spectrophotometer according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Incident light, 2... Polarizer, 3... Electro-optical substance substrate, 4... Analyzer, 5... Condensing lens, 6...
. . . Light amount detector, 7 . . A/D converter, 8 . . Fourier transform calculation device, 9 . . . Optical shutter control circuit, 10
... Output device, 11... Electrode, 12... Optical shutter.

Claims (1)

[Scope of Claims] 1. The incident light is sequentially passed through a polarizer, a substrate made of electro-optic material with electrodes, an analyzer, and a condensing lens, and the voltage applied to the substrate is changed, and the total amount of light from the condensing lens is changed. A spectral measurement method comprising performing a Fourier transform calculation based on the intensity of transmitted light and outputting the intensity of transmitted light at a predetermined wave number corresponding to the voltage applied to the substrate. 2. Equipped with an optical shutter that utilizes an electro-optic effect, a circuit that controls the amount of light transmitted through the shutter, a received light amount detection device that detects the light transmitted through the shutter, and an arithmetic device that performs Fourier transform on the output of the device. . A Fourier transform spectrophotometer, wherein the optical shutter is formed of a substrate made of an electro-optic material with electrodes.