JPS63187137A - Photoacoustic measuring apparatus - Google Patents

Abstract

PURPOSE:To perform photoacoustic measurement within a short time, by mounting a continuous laser beam generating means and a means for sweeping a laser beam irradiation point along a specimen. CONSTITUTION:A motor 3 is continuously rotated to determine the sweep speed of a reflecting member 2, a voltage mu-factor 9, the data collection time of an A/D converter 10, and the information continuity length at a measuring part, and the data specimen is dripped on a plate 5c to perform initial setting. Laser beam is reflected by the reflecting member 2 and detected by a detector 6a and the A/D converter 10 takes in data at a set interval. When the laser beam impinges against the specimen on the plate 5c, sound is generated to be converted to a photoacoustic signal by a converter 8 and said signal is amplified by an amplifier 9 and converted to a digital signal by the A/D converter 10 to be stored in a measuring part 11. The transmitted beam of the plate 5c is detected by a detector 6b and the sweep speed at that time is recorded and displayed to finish the first data collection. This operation is repeated nine times and data are integrated and smoothed by the measuring part 11 to display a graph on a display counter 7. By this constitution, since data can be inputted to the measuring part 11 at a high speed, a measuring time is shortened and an unstable specimen can be rapidly measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photoacoustic measurement device, and more particularly, to a photoacoustic measurement device using high-speed optical sweep that can shorten measurement time.

[Prior Art] A densitometer (micrometer photometer) is known as a device for quantitatively analyzing a sample spread or migrated on a moving gel plate.

There are several types of densitometers with different measurement methods. Among them, densitometers that use photoacoustic spectroscopy (PAS) are extremely useful devices for physical, chemical, and biological applications because they are not affected by the surface condition of the sample. It is used in various fields such as science, engineering, and biotechnology.

Photoacoustic spectroscopy measures the process by which photons absorbed by the sample are converted into heat by shining intermittent or modulated light onto a sample held inside or on the surface of a solid, or a sample adsorbed on these. It is something. For details, see, for example, JP-A-57-8436 and JP-A-60-23634.
It is detailed in No. 1.

Densitometer using conventional photoacoustic spectroscopy (hereinafter referred to as
As shown in Figure 3, the photoacoustic measuring device (referred to as a photoacoustic measurement device) is a light source! , Chitappa! 3. Photoacoustic cell 5.4%!
fF #Rent A Manocloa 4 Pano q Mon-H No 1 No Amp! 5, a recording section 16, and other devices.

In addition, the lock-in amplifier 15 includes a low-pass filter 15.
Contains a. This low-pass filter 15a is for converting the photoacoustic signal supplied from the microphone 8 into a DC signal.

In this case, since the photoacoustic signal supplied from the microphone 8 usually has a low frequency (5 to I 00 II z ), the time constant of the low-pass filter 15a is set to 0.3 to IOg.
cc.

[Problems to be Solved by the Invention] By the way, conventional photoacoustic measurement devices can perform highly sensitive measurements, but on the other hand, they have the problem of taking a long measurement time. It was not applicable to cases such as measuring signals from unstable samples.

The reason for this is that, as described above, the measurement system is provided with the low-pass filter 15a having a large time constant. That is, it was not possible to measure the sample in a time shorter than the time constant of the low-pass filter I5λ.

The present invention was made against this background, and its purpose is to provide a photoacoustic measurement device using high-speed optical sweep that can shorten measurement time.

[Means for Solving the Problems] According to the present invention, a sample, which is an object to be measured, is irradiated with light to detect the sound generated from the sample, and the components of the sample are analyzed based on this acoustic signal. A photoacoustic measuring device comprising a light beam generating means for generating a continuous light beam, and a light beam sweeping means for sweeping the irradiation point of the continuous light beam onto the sample along the sample. Features.

[Operation] According to the above configuration, the light beam continuously generated from the light beam generating means is swept as a continuous light without interruption or modulation, and the irradiation point is swept along the sample by the light beam sweeping means. .

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a photoacoustic measurement device that is an embodiment of the present invention.

In the figure! is a light source that uses a helium-neon laser. Reference numeral 2 denotes a plate-shaped reflective member having a reflective surface coated with aluminum, and one end of which is attached to the rotating shaft of the motor 3 via a connecting member CL. In this case, the light source! The laser light emitted from the photoacoustic cell 5 is reflected by the reflecting member 2 and enters the photoacoustic cell 5 .

The motor 3 moves the reflecting member 2 by its rotation. In this case, when the reflecting member 2 is rotated in the Y direction,
The irradiation point on the photoacoustic cell 5 is swept from right to left in the drawing.

The motor control W section 4 is for supplying a driving voltage to the motor 3, and the setting of the voltage value to be supplied to the motor 3 is performed by a variable resistor 4a provided in the motor control section 4. By changing the resistance value of this variable resistor 44a, the sweep speed of the laser beam can be changed within a range of 0 to 30 cm/see.

The photoacoustic cell 5 is a thin layer chromatography plate ζ-
117 Woo → 1 na n1-1 Table 1 n\out &/shelf carp cod 1 mouth ν, - Thin plate 5a formed in a mouth shape, and this thin plate 5
The thin plate 5a has a supporting member 5b in close contact with the right open end of the thin plate 5a, and the upper surface of the thin plate 5a is sealed with a window member made of quartz glass or the like. The thin layer chromatography plate 5c is inserted into the thin plate 5a, and then the support member 5b is brought into close contact with the thin plate 5a. Note that the thin layer chromatography plate 5c is removable, and the internal volume of the photoacoustic cell 5 is 6.5cm without the thin layer chromatography plate 5c inserted.
It is 3rrl.

The photodetectors 6a and 6b are photodetectors that each detect the laser beam reflected by the reflection member 2, and are respectively arranged at both ends of the photoacoustic cell 5 at a predetermined interval. A photodetection signal from the photodetector 6a is supplied to a display counter 7 and an analog/digital converter (hereinafter referred to as an A/D converter) 10. In this case, since the mower 3 is continuously rotating in the measurement state, the A/D converter 10 starts A/D conversion at the same time as the laser beam is incident on the photodetector Vs6a. Furthermore, phototransistors and the like are used for the photodetectors 6a and 6b.

Reference numeral 7 denotes a display counter for measuring the scanning speed of the laser beam, that is, the rotational speed of the motor 3, and displaying the speed. This display counter 7 has a laser beam detector 6a,
The sweep speed is measured by counting the time it takes to pass between 6b and 6b using a predetermined clock.

8 is a microphone placed on the left end portion of the photoacoustic cell 5. This microphone 8 converts into an electrical signal the sound generated when a laser beam hits a sample (for example, malachite green, carbon black, etc.) dropped or spread on the thin layer chromatography plate 5C. The photoacoustic signal output from this microphone 8 is supplied to a preamplifier 9. Further, as the microphone 8, an electret condenser microphone or the like is used.

The preamplifier 9 amplifies the photoacoustic signal supplied from the microphone 8 to a predetermined voltage value, and amplifies the photoacoustic signal by approximately 72 to 79 d13 in voltage ratio.

The output voltage of preamplifier 9 is supplied to A/D converter 510.

The A/D converter (2) 0 reads the output voltage (analog voltage) supplied from the preamplifier 9 at regular intervals and converts this analog value into an 8-bit digital value. Zumbling time of A/D converter IO is IO~l0
It is continuously variable within 00 μsec. Also, A/
D converter! The conversion start time of 0 starts from the time when the photodetection signal is supplied from the photodetector 6a. This A/D conversion it
The output voltage of O is the measurement part! Supplied to I.

The measurement unit 11 displays the sample densitogelium on a display based on voltage value data supplied from the A/D converter IO. This measurement part! 1 has a function of integrating and smoothing data obtained by repeatedly collecting the same sample. In addition, this measuring section 11
A microcomputer or the like is usually used.

Next, the operation of this circuit will be explained.

Here, initial settings before starting measurement are performed as follows.

■Rotate motor 3 continuously.

■The moving speed of the reflecting member 2, that is, the sweeping speed of the laser beam, is set to a desirable value depending on the sample to be analyzed and the S/N ratio, for example, 1.
It is set to 2.4 cm/sec.

(2) The voltage amplification factor of the preamplifier 9 is, for example, 78 dB.

■A/DA/D converter 10 data collection time is, for example, 500
Let μ5ec be constant.

(2) Let the data length accumulated by the measurement unit II be, for example, 1 kilobyte.

(2) Malachite green as a sample is dropped onto the thin layer chromatography plate 5C so that it spreads to a diameter of 2.3 mm.

Next, in FIG. 1, when a laser beam is irradiated from a light source I, the laser beam is reflected by a reflection member 2 and is detected by a photodetector 6a.
incident on . As a result, the photodetector 6a detects the laser beam. As a result, the photodetector 6a supplies a photodetection signal to the A/D converter 10, and 11/l'% rhtm'-
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First, the A/D converter! 0 reads the detection signal,
Data acquisition is started every 500 μsec.

The sweeping laser beam is a thin layer chromatography plate)
When it hits the malachite green spread out on 5c, a sound is generated from this malachite green. This sound is converted into an electrical photoacoustic signal by a microphone 8, and then supplied to a preamplifier 9, where it is amplified. The amplified photoacoustic signal is supplied to an A/D converter m10, where it is converted into a digital value. The photoacoustic signal converted into a digital value is supplied to the measuring section 11 and stored. Then, the laser beam is applied to the thin layer chromatography plate 5.
When the light passes through c and enters the photodetector i6b, a photodetection signal is supplied from the photodetector 6b to the display counter 7, and the sweep speed at that time is recorded.

This completes the first data collection.

Thereafter, this process is repeated nine times to collect data, and the data is stored in the measurement unit 11 each time. After integrating the data 10 times, the measurement unit 11 smoothes the data and displays Densitogerum on the display.

Fig. 2 shows malachite green 0.75 μ7 Densitogelum B. Furthermore, the waveform indicated by the dashed line is a simulation waveform of malachite green optical densitogelium.

From this result, the measurement time is approximately 0°5 seconds for one sweep.
This is approximately 1/10 compared to conventional photoacoustic measurement equipment.
It was shortened by 0.

As described above, by irradiating the sample with continuous light, there is no need to provide a low-pass filter or the like, and data is manually input to the measurement unit 11 at high speed. As a result, the measurement time is shortened, making it possible to measure samples that must be measured quickly or unstable samples.

In the embodiments of the present invention, a helium-neon laser is used as the light source l, but other lasers such as an argon laser, a dye laser, a semiconductor laser, or a carbon dioxide laser may also be used. In addition, the reflection member 2 was moved in order to sweep the laser light irradiated from the light source 1 to the photoacoustic cell 5.
A method of directly moving the light source 1 may also be used. For example, the following methods can be considered.

■A method of attaching light source I to a rack using a rack/binion machine tank and moving this light source I.

■A method of attaching the light source I to the worm using the worm gear groove and moving the light source I.

■A method of attaching the light source I to a rack or pin using a combination of racks and pins and moving the light source I.

■A method of moving the light source 1 using a horizontal movement reel mechanism.

In addition, in the method of each item mentioned above, the light source I was moved, but the reflection part! It can also be used to move /12.

Further, in the embodiment of the present invention, an 8-bit A/D converter 10 is used, but a 12-bit converter may be used instead. In addition, the number of times the measurement data was collected was set to 10, but this is optional, and the A/D
The data acquisition interval time of the converter 10 of 500 μsec is also arbitrary.

In addition, since the photoacoustic signal collected by the microphone 8 is amplified by the preamplifier 9 and then converted to a digital value,
Almost no signal deterioration occurs.

As a result, reproducibility and measurement accuracy are improved. Furthermore, since the measurement can be carried out in a short time, the laser beam can be swept over the same sample many times, making it possible to perform integrated smoothing of the data. This provides the advantage of further improving reproducibility.

[Effects of the Invention] As described above, according to the present invention, light is irradiated onto a sample as an object to be measured, sound generated from the sample is detected, and the components of the sample are determined based on this acoustic signal. The photoacoustic measuring device for analysis is equipped with a light beam generating means for generating a continuous light beam, and a light beam sweeping means for sweeping the irradiation point of the continuous light beam onto the sample along the sample. , measurement time can be shortened, reproducibility and measurement accuracy can be improved, and three-dimensional imaging of the material surface or subsurface layer can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.
Figure 2 is a waveform diagram for explaining the operation of the same embodiment;
The figure is a block diagram showing the configuration of a conventional photoacoustic measuring device. ! ......Light source (light beam generating means), 2...
...Reflector, 3...Motor, 4...
Motor control unit (2, 3, 4 are light beam sweeping means).

Claims (1)

[Claims] A light beam that generates a continuous light beam in a photoacoustic measurement device that irradiates light onto a sample, which is an object to be measured, detects the sound generated by the sample, and analyzes the components of the sample based on this acoustic signal. A photoacoustic measuring device comprising: a generating means; and a light beam sweeping means for sweeping a continuous irradiation point of the light beam onto the sample along the sample.