SU857732A1 - Spectral photometer - Google Patents

Description

(54) SPECTROPHOTOMETER

one

The invention relates to optical measurement techniques and can be used in colorimetric measurements and control of color characteristics of objects / for example, textile materials.

Spectrophotometers are known for monitoring the colorimetric characteristics of objects containing a monochromator and a photoelectric measuring path 1.

The disadvantage of this spectrophotometer is low productivity, because in order to obtain the spectral dependence of the reflection coefficient of an object, it is necessary to measure the optical characteristics of the object in each spectral range within the selected range.

The closest to the present invention is a spectrophotometer containing a source of light beams of different spectral composition modulated in amplitude with different frequencies, an optical circuit for measuring the characteristics of the sample and a photometric path, the source of light beams connected through an optical circuit to a photometric transducer of the photometric path through which Amp., and the frequency division link, connected to recorder 2.

This device allows measurements of the optical characteristics of an object at the same time in several spectral intervals.

A disadvantage of the known spectrometer of a photometer is the low measurement accuracy due to the temporary instability of the intensity of the light source and the gain of the photometric path.

15

The purpose of the invention is to increase the accuracy of measuring the optical characteristics of objects.

Claims (2)

The goal is achieved by the fact that, in a spectrophotometer containing a source of light beams of different spectral composition modulated in amplitude with different frequencies, an optical scheme for measuring the characteristics of a sample and a photometric path, photoelectric circuits for automatically stabilizing the intensity of the source radiation and the gain of the photometric path are introduced, having a common source reference signal, modulated by amplitude. The drawing shows a block diagram of a spectrophotometer. The spectrophotometer contains light sources 1 of light of different spectral composition, made on LEDs 2 connected to individual power generators 3 of different frequencies, LEDs 2 using LEDs 4 are connected to an optical circuit 5 measuring reflective characteristics of the sample. The output of the optical circuit 5 is also connected with a light guide by a photoconverter 7 of the photometric path 8. The photoconverter is connected to the input of amplifier 9, to the output of which synchronous detectors 10 are connected, which provide frequency separation of signals. The outputs of synchronous detectors 10 are connected to the recorder {not shown) To stabilize the overall sensitivity of the photometric path 8 and the intensity of the LED emitting light 2, the spectrophotometer has a circuit 11 for automatically stabilizing the radiation intensity of the LEDs 2 and a circuit 12 for automatically stabilizing the gain of the photometric path 8, both circuits having a common source 13 reference light signal connected to the generator 14 power. The amplitude-modulated radiation of the source 13 is supplied to the phototransducer 7 and the phototransducer 15 of the stabilization circuit 11. Photovoltage 15 also receives radiation from LEDs 2. Photoconverter 15 is connected to the input of amplifier 16, and synchronous detectors 17 and synchronous detector 18 are connected to the output of amplifier 16, which produce frequency separation of signals from LEDs 2 and source 13. The outputs of synchronous detectors 17 are connected to one of the inputs of the comparison circuit 19, and the output of the synchronous detector 18 to the digital inputs of the comparison circuit 19. The outputs of the comparison circuit 19 are connected to the control inputs of the 3 generators. The circuit 12 for automatically stabilizing the gain of the photo metric path 8 includes a synchronic detector 20, the input of which is connected to the output of amplifier 9, and the output is connected to one of the inputs of the comparison circuit 21, which compares the voltage from the output of the synchronous detector 20 to the specified voltage. by uq. The output of the comparison circuit is connected to the control input of amplifier 9. The light from the LEDs 2 enters the optical measuring circuit 5. The luminous flux reflected by the sample enters the photovoltaic converter 7. After amplification, it enters the inputs of the synchronous detectors 10, where the signals carrying information about the reflective characteristics of the sample in different spectral intervals are extracted. When reducing the total sensitivity of the photometric path 8 at a constant radiation power of the LEDs 2 and the source 13, the signal at the output of the synchronous detector 20 also decreases. This will cause the error signal to appear at the output of the comparison circuit 21, which will go to the control input of the amplifier 9 and change its gain factor. As the intensity of one or all of the LEDs 2 increases, for example, the signal at the output of the synchronous detector 18 also increases. At the outputs of the comparison circuits 19 in TC, the error signals that are fed to the control inputs of the power generator 3 and reduce the intensity of the emitting diodes. Changing the parameters of the source 13 of the reference light signal does not affect the operation of the spectrophotometer. Thus, as the radiation intensity of the source 13 increases, the gain of the photometric path 8 decreases, as well. the intensity of the radiation-g NIN LEDs 2 will increase. This circumstance allows reducing the time stability requirements of the reference light source without impairing the measurement accuracy of the optical characteristics of the samples. A spectrophotometer comprising a source of light beams of different spectral composition modulated in amplitude with different frequencies, an optical circuit for measuring the characteristics of a sample, and a photometric path made according to a conventional channel separation scheme, characterized in that, in order to improve accuracy, photoelectric circuits are introduced into the device automatic stabilization of the radiation intensity of the source and the gain of the photometric path, having a common source of reference lights amplitude modulated signal. Sources of information taken into account in the examination 1.G.A. Kundzich, M.T. Zaltsman, V.A. Ivanova Color measurement in the pulp and paper industry. M., VNIIPIEIlesprom, 1976, p. 17-20. 2. Authors certificate of the USSR I 86882, cl. G 01 J 3/08,.