RU1805353C - Multichannel photometer - Google Patents

Abstract

The invention relates to a photometric technique for measuring light transmission in predetermined sections of the spectrum of the light range of substances placed in the cells of microtiter plates, and can be used in practical and scientific research in medicine, biophysics, chemistry, biotechnology, agriculture, environmental protection and in other areas of the national economy. The purpose of the invention is to improve the accuracy of measurements. The photometer is additionally equipped with a disk connected to the motor shaft with holes in which interference filters and introduced neutral filters are arranged in pairs in order to increase their light transmission, and with hole position markers relative to the optical axis on the disk periphery, a hole position sensor located opposite the markers and connected together with the engine with a computing device through an additional interface, the reference channel, consisting of -. which consists of a prism, a photodetector, and an amplifier, a current amplifier, while the photodetector of the reference channel is located against the output face of the prism mounted between the collimator lenses in such a way that its reflecting face is inclined at an angle of 45 to the horizontal optical axis and at a distance of I from the optical axis to the upper edge of the prism, as defined by the expression b / 2 I (D / 2-a), where D is the light diameter of the collimator lens, a is the size of the input face of the prism, b is the size of the long row of the matrix of positive lenses L Д1 (к + 1 ) + d, where Al is the distance between the centers of positive lenses, k is the number of lenses (cells) in the row, d is the diameter of the positive lenses in the matrix. 2 ill. ate 00 o ate CJ ate

Description

The invention relates to a photometric technique for measuring light transmission in predetermined sections of the spectrum of the light range of substances placed in the cells of microtiter plates and can be used in practical and scientific research in medicine, biophysics, chemistry, biotechnology, agriculture, protection environment and in other areas of the national economy.

The aim of the invention is to improve the accuracy of measurements.

Functional block diagram of this multi-channel photometer is presented in figure 1,

In FIG. Figure 2 shows a reference channel with elements of an optical circuit that explains the location of the prism of the reference channel in the optical circuit.

. The multi-channel photometer (Fig. 1) contains a light source 1 located on the horizontal optical axis, a condenser 2, interference light filters 3 and neutral light filters 4 mounted in the holes of the rotating disk 5, a luminous expander 6, a two-lens collimator 7. Vertical optics of the axis in the multi-channel photometer are a matrix of positive lenses 8, a removable microtiter tablet on the slide device 9, a matrix of photodetectors 10. A landing pin is provided on the slide device 9 of the tablet you, in which, when using a microtiter plate with a U-trimmed bottom, a negative lens array 11 is inserted above the plate. The diaphragm array 12 is located under the tablet. In addition, behind the collimator 7, a rotating mirror 13 is located at an angle of 45 ° to the horizontal and vertical optical axes. The multi-channel photometer also contains a reference channel, consisting of a prism 14, a photodetector 15 and an amplifier 16, while the photodetector 15 is located opposite the output the edges of the prism 14, and the prism is fixed between the lenses of the collimator 7 so that its reflecting face, t, is inclined at an angle of 45 ° to the horizontal optical axis and the distance I from the optical axis to the upper edge of the prism is determined by the expression

". (-

where D is the diameter of the collimator lens;

a is the size of the input face of the prism;

b is the size of the long row of the lens matrix defined by the expression b Al (k- - 1) + d, D is the distance between the centers of the positive lenses (cells), k is the number of lenses (cells), d is the diameter of the positive lenses in the matrix .

The focal length of the negative lenses is such that the image of the filament of light source 1 is at infinity.

Positive lenses 8 of the matrix, negative lenses 11 of the matrix, the centers of the cells of the tablet on the slide device 9, the centers of the diaphragms 12 of the matrix and the centers of the photodetectors 10 of the matrix are aligned.

At the periphery of the disk 5, markers 17 are provided for the position of the pairs of filters 3 and 4 relative to the horizontal optical axis.

The photometer also contains a position sensor 18 of the holes with pairs of filters 3 and 4, which is located against the markers 17, the engine 19, the shaft of which is connected to the disk 5. In addition, the photometer contains a computing device 20 with 4 interfaces 21, 22, 23, 24, the switch 25, the recorder 26, the control unit 27 and the display unit 28. The outputs of the photodetectors 10 of the matrix are connected through an amplifier 29 to the signal inputs of the switch 25, the output

0 of the reference channel receiver 15 is also connected to the signal input of the switch 25 through the current amplifier 16. The output of the switch 25 is connected to the signal input of the analog-to-digital converter 30,

5, the digital signal outputs of which are connected to the data input of the computing device of the microcomputer 20. The interface 21 is connected to the control inputs of the switch 25 and the analog-to-digital converter 30. The interface 22 is connected to the control unit 27 and the display 28, the third interface 23 connects the computing device 20 and recorder 26, and interface 24 computing device 20 with an engine

5 19 by an i-position sensor 18.

The photometer works as follows,

The operator through the control unit 27, which is connected via an interface

0 22 with computing device 20, brings the computing device to its original state, i.e. in the computing device. RAM is being cleaned, and

5, its central processor (CPU) is ready to start executing instructions according to the device operation algorithm implemented in the form of a program stored in its read-only memory (ROM). Job

0 of the instrument begins with a disc number identification routine, i.e. determining the wavelengths of the transmission of radiation by interference filters. To do this, through the interface 24, the computing device starts the engine 19, which rotates the disk 5 with the pairs of filters 3 and 4. The position sensor 18 and the markers 17 generate a code for matching the pair of filters with a given wavelength at

0 optical axis. This code is supplied via an interface 24 to a computing device. When this pair of filters is located on the optical axis, according to the adopted code, the computing device immediately stops the engine 19 through the interface 24. Further, the computing device through the interface 21 through the switch 25 connects the ADC 30 to the reference channel circuit. Part of the radiation from the light source 1 through the capacitor 2, a pair of filters

3 and 4, expander b, the first lens of the collimator 7 reflected by prism 14 is incident on the photodetector 15. The latter converts the radiation into an electrical signal proportional to the transmission of a pair of filters 3 and 4, which is fed to the ADC 30 through the current amplifier 16 and switch 25 . The ADC converts this signal into a digital code stored in RAM of computing device 20.

Further, the computing device, according to the above-described algorithm, starts to rotate the disk, stops it when the next pair of filters is located on the optical axis, remembers the signal size, etc., until the values of the signals from all the pairs of filters located on a particular disk are stored in RAM. After that, the computing device analyzes the data stored in RAM and data on the location of the filters on the disk, located in the ROM. If there is an increase in their light transmission, a well-defined disk with known transmission wavelengths of the filters is uniquely identified. The absence of an increase in light transmission is perceived by the computing device as the presence in the photometer of another disk with other known transmission wavelengths, i.e. at least two interchangeable disks are allowed in the photometer. At the same time, information about the placement of filters on the 2nd disk is also located in the ROM of the computing device.

Next, processing of the light transmittance measurement program begins. For this, the computing device feeds the digital code stored in the ROM to the interface 24. According to this code, the disk 5 rotates until the code from the position sensor 18 and from the computing device on the interface 24 become the same. The codes on the interface in this case correspond to the position of the disk at which the light flux is blocked and the signals at the output of the photodetectors are proportional to the currents from the background spurious illumination, dark currents of the photodiodes, zero bias of the current amplifiers 29. Next, the computing device alternately, starting from the reference channel, connects the ADC to measuring the magnitude of the background currents to each channel, the ADC 30 generates digital equivalents of the magnitude of the background currents that are stored in the RAM of the computing device, POP and f - the magnitude of the backgrounds currents in the reference and 1st working channel.

After that, the transmission wavelengths of the filters located on the disk installed in the photometer are displayed on the display unit 28. The operator, by means of the control unit 27, requests the necessary wavelength for photometry 5. By this command, from the control unit 27, the computing device sets a digital code on the interface 24. The code is selected from the ROM and corresponds to the transmission wavelength of the desired filter. Therefore

0 to the code, the disk 5 rotates until the code from the position sensor 18 and the set code of the computing device match. The meaning of the digital codes corresponds to the position of the disc at which the center

5, an interference filter with a desired transmission wavelength coincides with the horizontal optical axis. After stopping the engine 19, the computing device through the display unit 28 prompts the operator about the need. installing the tablet on a sliding device 9. In this case, the tablet may be empty or with a blank sample in order to measure the true light transmission of the substance under study5. The tablet may not fit if light transmission is detected relative to air. After setting the tablet, the operator confirms via the control unit 27

0 setting the tablet, and the computing device begins to connect the ADC 30 in turn to all working channels. Digital equivalents corresponding to the intensity of the incident light flux are stored in the RAM of the computing device. In this case, after each measurement in the working channel, the intensity of the light flux in the reference channel 1

0 digital equivalents are also stored in the RAM of the computing device. Thus, the intensity drift of the light source 1 is taken into account by the reference channel, for which the computational

5, the device normalizes the values of 1Pad to the values of 1pedog1, while taking into account the background currents in the working and reference channels 1FOP and 1f, in accordance with the expression

0Cad (1pad - 1phU (1lad ° P - 1ph ° P). (1)

and stores in RAM the values of Cpad1. the corresponding intensities of incident light fluxes, corrected by the magnitude of the drift of the radiation source and the magnitude of the background currents.

After that, the computing device by means of the indicating unit requires the installation of a tablet with the test substance on the slide device 9 and setting it to the photometric position. After that

as the tablet by means of the slide device 9 is set to the photometric position, the operator, by means of the control unit 27, starts a subroutine for recording the intensities of the light flux passing through the studied substance Inp 1, and after each measurement in the working channel, the radiation intensity is measured in the reference channel lnponl . After the implementation of this subroutine, the values of the background currents in the working and reference channels are again taken. The correction for the drift of the radiation source and background currents is carried out by a computing device calculated by the formula

Kpr1 (1pr1-1f) / (1prOP | -1f ° P) .. (2)

After storing the CR values in RAM, the computing device proceeds to calculate the light transmission values of the test substances by the formula

x 100%.

(3)

to

tg 1chpad

The light transmission values of substances in each channel m are stored in RAM. Subsequently, the operator, by means of the control unit 27, requires the output of photometric results. t on indicator 28 or recorder 26.

If the operator needs to express the results of photometric measurements in units of optical density, then the computing device does an additional calculation according to the formula

Di lg G | ,

where D is the optical density in the ith channel. This calculated result can also be displayed using a computing device on the display unit 28 or recorder 26.

Only the light flux passing through the sediment and

limited by the rays, which are determined by the diameter of the diaphragm - D. Beams that do not pass through the sediment are shielded by the diaphragm D.

To obtain adequate information, it is necessary to ensure that only those rays that have passed through the button are incident on the photodetector. This condition (for the prototype) is met only if the meniscus is located symmetrically and subject to a certain relationship between the meniscus curvature radius — RH, the light flux convergence angle — and its cross-section diameter (at the point where the light flux falls on the liquid under investigation) —d . Constant R reach

impossible due to differences in the viscosity of the test fluids and differences in the wettability of the tablets used. The - d parameter also undergoes changes from cell to cell depending on the volume of the test fluid. With an asymmetric meniscus, two effects are observed:

1. the luminous flux, passing the precipitate, enters the photodetector and the signal from the photodetector increases,

2. The luminous flux (in the absence of precipitate) is cut off at the edge of the photodetector area of the photodetector. FP - the signal from the photodetector decreases.

Both the first and second effects lead to a decrease in measurement accuracy.

Thus, the error in the measurement on the tablet with a U-shaped bottom in the proposed device is much less.

than the prototype. FIG. 2 illustrates the optimal arrangement of the reference channel prism in the optical circuit in accordance with the expression:

 I (D Z1

2-1 $ (2 a) b Al (k-1) + d,

where D is the light diameter of the lens of the collimator 7,

a is the size of the input face of the prism 14, I is the distance from the horizontal optical axis to the upper edge of the prism 14,. b is the size of the long row of the lens matrix 8,

D | - the distance between the centers of the positive lenses,

k is the number of lenses in the row, d is the diameter of the positive lenses in the matrix.

Size I must not be less than b / 2, because otherwise, the prism will cut off the optical flux incident on the lens matrix. At the same time, I must not exceed the value of I

(at a), since otherwise will

overlapping of the luminous flux from the light source 1 by the frame of the collimator 7. When I

full overlap of the light flux with the collimator rim is possible - the light does not enter the reference channel,

The disk 5 is made of metal with holes for interference filters 3, neutral filters 4 and

markers 17. Neutral filters 4 are made of glass brand НС. Markers 17 are made in the form of 6 radial slots on the periphery of the disk. 4-gaps are position markers of pairs of neutral interference filters. N that

the slit is a marker of the position of the disk when the luminous flux is blocked when measuring background currents. The sixth slit is a marker of the initial position of the disc.

The position sensor of the holes 18 with pairs of light filters is made in the form of two pairs of LEDs - a photodiode, the luminous flux between which is opened by six markers. The first pair records the passage

5 markers, second pair passage

6th marker during disk rotation.

Experimental studies of a multichannel photometer for photometry of liquid substances and microtiter tablets with cells with a flat and U-shaped bottom showed that, compared with a device of a similar purpose (prototype), this photometer provides a reduction in absolute error of up to 1% on a photometric scale .

Claims (1)

SUMMARY OF THE INVENTION A multi-channel photometer comprising a radiation source located along the optical axis of a capacitor, a system for generating a working wavelength, means for expanding a radiation flux, a two-lens collimator and a vertical optical axis optically coupled to a collimator. microtiter tablet with a matrix of positive lenses, mounted with the ability to move parallel to the plane of location of the matrix of positive lenses and the matrix of photodetectors, a current amplifier unit, a switch, a computing device with three interfaces, an analog-to-digital converter, a control unit, an indication unit and a recorder, with the outputs of the photodetectors through current amplifiers are connected to the signal inputs of the switch, the output of which is connected to the input of the analog-to-digital converter , Digital outputs are connected to the data input of the calculation unit, control outputs of the computing device through a first interface associated with the control inputs of the switch and the input of an analog-digital converter, the blocks control and indication are connected to the computing device via the second interface, the recorder through the third interface. characterized in that, in order to increase the accuracy of measurements, the photometer further comprises a reference channel, arrays of negative lenses and apertures. optically coupled respectively to an array of positive lenses and photodetectors, wherein the system for generating the working wavelength comprises a disk with holes and reference points located on the periphery of the disk, interference and neutral filters, a sensor of the position of the disk holes, a motor and an additional interface, while the motor shaft is connected to the disk, the position sensor is optically connected to the benchmarks of the disk and electrically to the additional interface, which is connected to the calculation In particular, the reference channel contains a prism, an additional photodetector and an additional current amplifier, the additional photodetector optically connected to the output face of the prism and electrically connected to an additional current amplifier, the output of which is connected to the input of the switch, the prism is installed between the collimator lenses in this way that its reflecting face is inclined at an angle of 45 to its optical axis and the distance I from the optical axis of the collimator to the upper edge of the prism defined in expression ( D -and) 2 v 2 where D is the light diameter of the collimator lens;  a is the size of the input face of the prism; b is the size of the long row of the matrix of positive lenses, b AJ (k-1) + d, where Al is the distance between the centers of the positive lenses: K is the number of lenses in a long row of the matrix; d is the diameter of the positive lens. 27 28 2