LT3848B - Method and device for measuring of a materials agsorbing coefficient - Google Patents

Abstract

Invention applies to optics and may be used for registering the material adsorption coefficient dependence on the wave length, temperature and other parameters. The invention aims to increase the precision of measurement of the material adsorption. The aim is achieved by the fact, that due to the proposed measurement method and the equipment all three quantities (l0 - light intensity directed onto the researched material, lτ - intensity of light passed through the researched material, lR - intensity of light reflected by the researched material) are measured together, and if the desired parameter changes an adsorption coefficient dependency on this parameter is set. The equipment itself consists of a monochromatic light source, an optical commutation device with the first mirror put in the way of the light source ray, in a way both outgoing rays form the above mentioned commutation device, and there are placed measuring chambers and a detector of light. In order to reverse the rays there are reflection prisms installed in each measuring chamber in the way of both rays. In the way of the ray between the reflection prisms, which directs the reflected ray form a sample to the detector, and the sample, the second mirror is placed.

Description

The invention relates to the field of optics and can be applied to measure the spectral characteristics of the absorption coefficient of materials, especially those of very complex spectra.

A known method of measuring the absorption coefficient of substances, consisting of measuring the luminous intensity lo falling into the substance, measuring the luminous intensity It passed, reflecting the luminous intensity Ir, and, knowing the thickness of the substance d, calculating the absorption coefficient K using the equation:

K = i Inkilu d Where lo - the intensity of the incident light

And - the intensity of the reflected light,

It is the intensity of transmitted light, d is the thickness of the material.

Known device for measuring the absorption coefficient of materials, consisting of a monochromatic light source, a measuring chamber and a light detector (Spectrophotometer CO-46 - technical description and operating instructions, Leningrad, LOMO, 1982).

The main disadvantage of this absorption coefficient measurement method and device is that the difficulty of maintaining the same conditions, such as temperature, wavelength, etc., when measuring separately the three values - incident light intensity I _o , reflected light intensity and transmitted light intensity It.

The closest known method of measuring the absorption coefficient of materials, consisting of periodically directing a beam of light in two optically equivalent but different paths, is to direct the sample to one of the two path beams at a single point for recording intensity (IK-Spectrophotometry) SPECORD M80 / 85. Kombinat VEB Carl

Zeiss JENA, DDR, 1984, pp. 9-122). The direction of propagation of one of the beams shall be varied such that periodic beams of light reflected from the sample and incident on the test substance are introduced into the detector. The ratio of the following signals is proportional to the reflectance R. The absorption coefficient K is calculated using the equation:

K ^ lln. ¹ - ^R , d

where d is the thickness of the sample,

R is the reflectance of the light,

T - light transmission coefficient.

The closest known apparatus for measuring the absorption coefficient of materials consists of a monochromatic light source, a beam-mounted commutator with a first slide mirror, a measuring chamber, an output switch with a second slide mirror, and a light detector (Instructions for use IK-Spectrophotometry SPECORD M80 / 85. Zeiss JENA, DDR, 1984,9-122).

The main disadvantage of this absorption coefficient measurement method and device is the separate measurement of the light reflectance R and the light transmission coefficient T. This disadvantage is particularly significant for the measurement of the absorption coefficient of segmented electric superconductors in phase transitions where there is a strong temperature dependence of , which small variations in individual measurements result in large differences in the measured values.

The object of the invention is to increase the accuracy of measuring the absorption coefficient of materials.

This objective is achieved by measuring the absorption coefficient of the substances, consisting of a monochromatic light-beam commutation frequency ω in two different paths, by detecting the light and calculating the absorption coefficient of the substances by applying the formula. The rays coming in different paths are reversed in the measuring chamber. At the intersection of the beams, a sample and beams are coupled to the detector at a frequency ω, but in the accelerating phase of 1/3 T, where T 3 is a period, and the absorption coefficient of the materials is given by:

K = i ln d V where d is the thickness of the sample,

Io - intensity of incident light,

I _R is the intensity of reflected light,

It is the intensity of transmitted light.

This object is a device for measuring the absorption coefficient of a substance consisting of a monochromatic light source, an optical switch with a first mirror positioned on its path, a measuring chamber and a light detector located on the path of both outgoing radiators and a second mirror. In the measuring chamber, the path of both beams follows a prism of reflection that alternates between beams. In the path of the beam, a second mirror is placed between the reflection prism that directs the beam reflected from the sample to the detector and the sample.

Due to the proposed method and device for measuring the material absorption coefficient, all three measured values (incident light intensity Io, transmitted light intensity It and reflected light intensity Ir) are measured together and by changing the desired parameter (wavelength, temperature, etc.) dependence of the absorption coefficient on this parameter.

The invention is illustrated in the drawings, in which FIGS. 1 is a block diagram of the device, FIG. 2 - Time diagrams of the sliding amplitudes of the first and second mirrors.

The method of measuring the absorption coefficient of materials consists of a monochromatic beam of light switching at a frequency ω of two different paths into a measuring chamber in which the said paths are alternately displaced by different paths. At the intersection of these beams, the sample and the beams are commutated, detected at the frequency ω, but in the accelerating phase 1/3 T (where T is the period), and the absorbance K of the materials is calculated from the light intensities obtained by equation (1):

K = Ilnkrlg ^ d Where d is the thickness of the sample, lo is the intensity of the incident light,

And - the intensity of the reflected light,

I _T - intensity of transmitted light.

The proposed device comprises a monochromatic light source 1, a light beam commutator 2 guiding the beam in two different paths, a first sliding mirror 3, two reflection prisms 5 and 6 in the measuring chamber 4 alternating beam paths, a second sliding mirror 7, a light detector 8 ( Figure 1). The test sample 9 is placed at the intersection of the two beams.

The method of measuring the absorption coefficient of the materials is realized as follows: the ray of monochromatic light emitted from the light source 1 enters the light beam commutator 2 having a first mirror sliding at frequency ω, which periodically guides the beam into one or another propagation path 4 In the measuring chamber, two reflection prisms 5 and 6, located on each of the two possible paths of light propagation, are reversed and the second mirror 7 sliding at the same frequency ω as the first mirror 3 but with different initial phases, to the light detector

8. The test sample 9 is placed in the measuring chamber 4 at the intersection of the beams.

At a time point ti, mirror 3 is in the path of beam propagation and mirror 6 is not. Then the beam from the light source 1 to the detector 8 passes through the test sample 9 and its intensity It (Fig. 2).

At time t _{2, the} mirror 3 is pulled out of the beam path, and the mirror 6 is in the beam path. The intensity of the light beam entering the detector 8 is then Iq.

At time t3, mirrors 3 and 6 are pulled out of the beam path. The light beam from the light source 1 to the detector 8 is reflected by the sample 9 and its intensity Ir.

Based on the detected intensities It, Io, Ir and, estimate the absorption coefficients by using equation (1).

In this way, due to the proposed measurement method and device, all three measured quantities (luminous intensity incident to the test substance - luminous intensity passed through the test substance - It and reflected light from the test substance - Ir) are measured together, thus eliminating the error resulting from different conditions. and increases the measurement accuracy of the absorption coefficient.

Claims (2)

A method for measuring the absorption coefficient of substances consisting of 5 monochromatic light beam commutation frequency ω in two different paths, the light detection and material absorption coefficient calculated using the formula, in which the different paths are rotated in the measuring chamber, the specimen at the intersection of the beam and rays at a frequency of 1/3 T , where T is the period, 10 switches to the detector and calculates the absorption coefficient of the substances according to the formula: K = i ln ItU-Lb, d Where d is the thickness of the sample, Io - intensity of incident light, And - the intensity of the reflected light, It is the intensity of transmitted light. 2. A device for measuring the absorption coefficient of a material, consisting of a monochromatic light source, an optical commutator mounted on its beam path and a first mirror, both measuring cameras located on the path of the outgoing beam of said switch, and 20 a detector and a second mirror, wherein the measuring chamber includes a reflector alternating beams along the path of both beams, in the beam path between the reflection prism that guides the beam reflected from the sample to the detector and a second mirror housed in the sample.