RU81320U1 - SPECTROMETER - Google Patents

Abstract

The utility model relates to analytical instrumentation, namely to spectral instruments, and can be used, for example, to create a small-sized, highly sensitive, and broadband multichannel spectrometer.

A multi-channel spectrometer is disclosed, comprising a housing with an input window, inside which an optical system is installed, at the output of which a multi-element photodetector is connected, connected to an electronic unit for its control and processing of output signals.

What is new is that the housing is sealed, and the multi-element photodetector installed in it is housing-free, while the housing of the spectrometer is evacuated or filled with an inert gas.

Description

The utility model relates to analytical instrumentation, namely to spectral instruments, and can be used, for example, to create a small-sized, highly sensitive, and broadband multichannel spectrometer.

Spectral devices decompose the electromagnetic radiation of the optical range into monochromatic components for a qualitative and quantitative study of the spectral composition of the light emitted, absorbed, reflected or scattered by the substance. Studies using spectral instruments make it possible to judge the chemical composition of matter and the nature of the physical processes associated with the emission or interaction of light with matter. When conducting research in the conditions of mobile laboratories, it is necessary that the spectral device meets the following requirements:

- It was compact, due to the limited volume of the mobile laboratory, which can be located on the basis of a car;

- had a wide working spectral range for solving various problems associated with the detection of a wide range of substances;

- had high speed to obtain measurement results in real time;

- It had high reliability and durability, which ensures high performance with a long service life;

- had low detection limits, allowing quantitative analysis of samples with high accuracy.

A known spectral device containing a housing with an input window, inside which an optical system is installed, the output of which is connected to a recording device based on photographic plates, which allows simultaneously registering a wide spectral range (see Tarasov IK Spectral devices. - L.: "Mechanical Engineering" , 1968. - S. 161-162.).

The main disadvantage of the known device is the impossibility of its operation in real time due to the long and complex process of manifestation of photographic plates.

A known spectral device containing a housing with an input window, inside which an optical system is installed, the output of which is connected to a recording device based on photoelectronic multipliers (PMT), which allows measurements

with high sensitivity and speed (see Tarasov KI Spectral Instruments. Publishing House "Engineering", Leningrad, 1968, pp. 300-301).

The main disadvantage of the known device is the limited number of simultaneously recorded spectral lines, equal to the number of PMTs used.

Closest to the claimed device (prototype) is an Ocean Optics spectrometer (see the Ocean Optics product catalog for 2007 http://www.oceanoptics.com/catalog.asp, p.13, 20-25) . The spectrometer consists of a housing with an input window, inside of which there is an optical system and a recording system, which is used as a linear multi-element photodetector. The spectrometer allows measurements to be taken simultaneously in a wide spectral range in real time and has small dimensions.

The main disadvantage of the known spectrometer is that it does not have sufficiently low detection limits due to the presence of a high level of background radiation due to the use of a multi-element detector protected from the environment by a special case with a glass entrance window on which parasitic reflections occur inside it, and between it and a multi-element detector (the level of scattered radiation is 0.1%).

The objective of the claimed utility model is to eliminate this drawback, namely, reducing the detection limits of the desired substances by reducing the level of background radiation.

The indicated problem in a spectrometer containing a case with an input window, inside which an optical system of the spectrometer is installed, at the output of which there is a multi-element photo detector connected to an electronic unit for its control and processing of output signals, it is solved by the fact that the body is sealed and the multi-element photo detector installed in it - in caseless design, while the spectrometer housing is evacuated or filled with an inert gas under excess pressure.

To reduce the background radiation level in the spectrometer, a multi-element photodetector in a housingless design is used, which eliminates spurious reflections both inside the glass entrance window and between it and the multi-element photo detector. Sealed housing allows you to protect the elements of the optical system located in it from environmental influences. Since the working spectral range of the claimed spectrometer lies from the vacuum ultraviolet (UV) to the near infrared region, when the spectrometer is operating inside the case, UV radiation is present. It is known that the interaction of UV radiation with air forms

ozone molecules, which are an active oxidizing agent, rapidly destroying the surfaces of elements of the optical system (surface of mirrors, diffraction grating, multi-element photodetector and others). To exclude this interaction, the spectrometer housing is evacuated and / or filled with an inert gas.

To control the tightness of the spectrometer case, the inert gas pressure inside the case exceeds atmospheric pressure by 0.1-2 atm. and is measured, for example, by a manometer. The presence of excess pressure indicates the tightness of the housing.

Also, to control the tightness of the spectrometer case, a vacuum with a level of not more than 0.5 atm., Measured by a pressure sensor, for example, a manometer, can be used. The presence of excess pressure above the specified limit indicates a violation of the tightness of the housing.

To reduce the detection limits of the spectrometer by reducing the intrinsic noise of the photodetector by reducing and stabilizing its dark current, the photodetector is mounted on the cooled surface of a Peltier thermoelectric refrigerator, the heated surface of which is installed in thermal contact with the spectrometer case.

To ensure the tightness of the housing, the inlet window is made in the form of a plate made of a vacuum-dense material transparent, for example, fused silica, which is sealed around the perimeter in a transparent spectral range.

Also, to ensure the tightness of the housing, the electrical contacts of the multi-element photodetector are connected to the control unit and process the output signals through a connecting cable and a vacuum tight connector installed in the wall of the housing.

Thus, the use of a sealed enclosure and a frameless photodetector mounted on a Peltier thermoelectric refrigerator allows one to significantly reduce the level of background illumination inside the spectrometer and to reduce the photodetector's own noise, thereby significantly lowering the detection limits of the spectrometer, which has no analogues among technical solutions used in modern spectrometers , the claimed solution meets the criterion of "inventive step".

Figure 1 presents an embodiment of the inventive spectrometer based on an optical Ebert-Fasti circuit and a multi-element photodetector.

Figure 2 presents the spectral lines of mercury recorded by a prototype of the inventive spectrometer and similar in design to the layout of the spectrometer, which differs from the claimed one in that the multi-element photodetector is made body with a cover glass.

The spectrometer shown in Fig. 1 contains a housing 1, an input window 2, an optical system 3, a photodetector 4, a Peltier thermoelectric refrigerator 5, a pressure sensor 6, a vacuum tight connector 7, an electronic control unit for registering signals from a multi-element photodetector 8, computer 9, analyzed input radiation 10.

Presented in figure 2, the spectral line of mercury Hg 435.8337 nm, registered: 11 - the claimed spectrometer; 12 - the layout of the spectrometer, which differs from the claimed one in that the multi-element photodetector is made body with a cover glass; low intensity mercury spectral line 13.

The spectrometer (figure 1) works as follows. The analyzed radiation 10 directed to the spectrometer passes through the input window 2, then is expanded into the spectrum by the optical system 3 (input slit, a collimating mirror, a flat diffraction grating, a focusing mirror), the spectrum is recorded on a photodetector 4, which is thermally stabilized by a Peltier thermoelectric refrigerator 5. Pressure in the housing is controlled by a pressure sensor 6. The electronic unit 8 is connected to a multi-element photodetector 4 through a vacuum tight connector 7. The registered output signal from the transfer unit 8 is transferred to computer 9, where it is analyzed using the Atom software package. Moreover, in the spectrometer case there are no reflections on the coverslip and between it and the photodetector, leading to an increase in the background radiation near the intense line. It can be noted that due to a decrease in the background radiation level in the inventive spectrometer, the limits of its detection have substantially decreased and it has become possible to register a new spectral line (13) located near line 11.

On figa presents the spectral line of mercury Hg 435.8337 nm 12 recorded by the layout of the spectrometer with a coverslip. The same spectral line 11 is recorded by the claimed device with a higher resolution, which allows you to additionally resolve a low-intensity line 13 (see figb).

Implementation examples.

Embodiment 1. A small-sized spectrometer was manufactured according to the Ebert-Fasti optical scheme. The spectrometer had a sealed housing filled with an inert gas with an overpressure of 1.2 atm, which was controlled by a manometer. The optical scheme of the spectrometer included an entrance slit 15 μm wide. Two mirrors with the same radius of curvature of 200 mm were used as input and output mirrors. A lens was mounted in front of the spectrometer's input window to focus the analyzed radiation on the input slit. BLPP-369 photodiode line (number of photodiodes

2580, placement pitch 12.5 and height 1000 μm, dynamic range 10 ⁴ ) was used in the case-free design. The temperature of the line is stabilized using a serial Peltier thermoelectric module of the K1-127-1 / 1.3 brand and a temperature sensor (KT397A-2 brand transistorless transistor, one pn junction of which is used as a diode), which is in thermal contact with the crystal of the line. The photosensitive surface of the ruler is installed in the region of the best focusing of the spectrum with the help of special screws that allow you to align the photo detector in the registration plane. As an electronic unit, we used the electronic registration unit of a multi-channel atomic emission spectrum analyzer (MAES), which is a means of measuring the intensity of spectral lines (registered in the State Register of Measuring Instruments of the Russian Federation under No. 21013-01) and manufactured by LLC VMK-Optoelectronics, g. Novosibirsk The electronic unit was connected to the line of photodiodes through a vacuum tight connector of the 2RMG series. Data from the electronic unit was transferred to the computer via an Ethernet cable. Mathematical processing of the output signal, its visualization, etc. were carried out using the Atom program (certificate of registration No. 2004611127). The spectrometer had the following technical characteristics: operating spectral range - 390-860 nm; inverse linear dispersion - 0.19 nm / diode; focal length - 100 mm; relative aperture - 1: 6; minimum exposure time - 10 ms; maximum exposure time - not limited; dimensions - 150x200x80 mm3; weight - 3 kg.

Embodiment 2. The design of the spectrometer, the optical circuit, and its main elements were performed similarly to Embodiment 1, but the spectrometer housing was evacuated with a pressure inside of 100 Pa (≈0.001 atm). A 13VT003 thermistor pressure gauge was used as a pressure sensor. The technical characteristics of the spectrometer are similar to embodiment 1.

Embodiment 3. The design of the spectrometer, the optical circuit, and its main elements were performed similarly to Embodiment 1, but the spectrometer housing was evacuated with a pressure inside 100 Pa and filled with an inert gas with a pressure of 0.9 atm. A pressure gauge was used as a pressure sensor. The technical characteristics of the spectrometer are similar to embodiment 1.

Thus, the claimed device allows to reduce the detection limit of radiation by reducing the level of background radiation.

Claims (6)

1. A spectrometer comprising a housing with an input window, inside which an optical system is installed, at the output of which there is a multi-element photodetector connected to an electronic unit for its control and processing of output signals, characterized in that the housing is sealed and the multi-element photo detector is installed in it case-free design, while the spectrometer housing is evacuated or filled with an inert gas. 2. The spectrometer according to claim 1, characterized in that the inert gas pressure inside the body exceeds atmospheric by 0.1-2 atm, and a pressure sensor, for example, a pressure gauge, is installed for its control. 3. The spectrometer according to claim 1, characterized in that the vacuum level is not more than 0.5 atm., And for its control a pressure sensor is installed, for example a manometer. 4. The spectrometer according to claim 1, characterized in that the multi-element photodetector is mounted on the cooled surface of the Peltier thermoelectric refrigerator, the heated surface of which is installed in thermal contact with the spectrometer case. 5. The spectrometer according to claim 1, characterized in that the input window is made in the form of a plate of material transparent in the working spectral range and sealed around the perimeter. 6. The spectrometer according to claim 1, characterized in that the electrical contacts of the multi-element photodetector through a connecting cable and a vacuum tight connector mounted in the wall of the housing are connected to the control unit and the processing of output signals.