JPH08122253A - Sample analyzer - Google Patents

Abstract

PURPOSE: To provide a highly reliable analyzer which is compact and has no movable part by modulating the intensity of sample cell passing light by using a modulator composed of a thick film liquid crystal cell where ferroelectric liquid crystal is sealed between opposing transparent electrodes. CONSTITUTION: Infrared rays having the absorbing band wave length of a measuring object component after passing through a filter 12, receive absorption according to an object component quantity of a sample in a sample cell 14, and are detected by an infrared ray detector 15. In order to distinguish this detecting signal from a stray light component, the infrared rays passing through the sample cell 14 are modulated by a modulator 13. The modulator 13 is composed of two silicon boards 131 and 132, spacers 134 to hold the problem of both constant and ferroelectric liquid crystal 133 sealed between the boards 131 and 132. The board 131 is connected to a gland, and the board 132 is connected to a voltage impressing circuit 137, and polarity reversing rectangular pulse voltage is impressed on the liquid crystal 133. The duty ratio of this pulse voltage is adjusted to a value on which a degree of modulation becomes maximum between 55 to 90%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a method for measuring the absorption of light (mainly in the infrared range, but also in the case of visible light) that passes through a sample such as liquid or gas. The present invention relates to a sample analyzer that measures the concentration of a component in a sample.
The sample to be measured by the sample analyzer of the present invention includes, for example, food (concentration measurement of fat and protein components), oil (concentration measurement of antioxidants and oxides), gas (CO ₂ , SO _{2 2} , concentration measurement of NO, CH, CO, etc.) and the like.

[0002]

2. Description of the Related Art The structure of a conventional sample analyzer is shown in FIG. 11 by taking a single cell type as an example. In the single-cell type, only one cylindrical sample cell 64 is used, one end of which is provided with a light source 61 via an interference filter 62, and the other end of which is provided with a photodetector (or infrared detector). ) 65 is provided. The principle of the measuring method of the sample concentration by this analyzer is as follows.
First, a liquid or gas sample is placed in the sample cell 64. Then, by the interference filter 62, only the light of the wavelength absorbed by the measurement target component in the sample out of the light from the light source 61 (for example, when measuring oxides in oil, infrared rays of wavelength 5 to 6 μm, CO in gas) _When measuring ₂ , the wavelength is 4.2 μm
(Infrared) is put in the sample cell 64. This specific wavelength infrared ray is absorbed by the measurement target component in the sample according to the concentration of the component, and is detected by the detector 65. After measuring the intensity of the specific wavelength infrared rays for the sample in this manner, the reference sample (non-oxidized oil,
Dry N ₂ gas or the like) is put in the sample cell 64, and the intensity of infrared rays having a specific wavelength is similarly measured. By comparing these two intensity measurements, the concentration of the component of interest in the sample can be determined.

However, with such a simple structure, highly sensitive analysis cannot be performed for the following reasons. That is, an infrared sample analyzer that uses infrared rays as the measurement light uses an infrared detector 65 with high sensitivity, but this detector 65 also detects thermal infrared rays generated from the surrounding substances. Therefore, when the amount of the component is very small, the infrared absorption amount of the component to be measured becomes small, and the signal is buried in the stray light component.

Therefore, in the infrared sample analyzer, generally,
A rotary chopper plate 66 is provided in front of the detector 65 (the light source 61
May be provided between the sample cell 64 and the sample cell 64), and the stray light component continuously incident on the detector 65 is distinguished by intermittently (or intensity-modulating) the light passing through the sample cell 64 at a predetermined frequency. I am trying. The intermittent signal and the continuous noise are distinguished by a signal processing circuit (not shown) that electrically processes the output signal of the infrared detector 65.

[0005]

As shown in FIG. 12, the above-mentioned conventional chopper plate 66 doubles the total cross-sectional area of the sample cell 64 in order to interrupt infrared rays passing through the entire cross-section of the sample cell 64. The above area is required. Moreover, since such a large chopper plate 66 also has to be put in the closed space 67, the entire device has to be very large. Further, since the chopper plate 66 is mechanically driven, noise and vibration are generated, and there is a problem that reliability for long-term use is low and life is short.

In order to solve these problems, it is conceivable to use a liquid crystal plate to intermittently or intensity-modulate light.
As described later, it is desirable that the modulation frequency is about 100 Hz or higher, but for such high speed modulation,
Ferroelectric liquid crystal, which has a fast response to electric field changes, is suitable. Liquid crystal plates using a ferroelectric liquid crystal are roughly classified into a thin film type and a thick film type.

The thin film type is also called a refraction type and is a type in which polarizing plates having different polarization directions are arranged in parallel with each other with a gap of about several μm, and liquid crystal is sealed between both polarizing plates. When no voltage is applied to the liquid crystal, the polarized light (including infrared rays) that has passed through one polarizing plate goes toward the other polarizing plate as it is, but because the polarizing directions of both polarizing plates are different, it is blocked by the other polarizing plate. , Cannot pass through the liquid crystal plate. But,
By applying a voltage to the liquid crystal, the liquid crystal becomes birefringent, and the polarization direction of the polarized light is rotated while passing through the liquid crystal. Therefore, by appropriately setting the applied voltage and the thickness of the liquid crystal layer, the direction of the polarized light transmitted through one polarizing plate is made parallel to the polarizing direction of the other polarizing plate so that light can pass through the liquid crystal plate. You can

However, the thin film type has a drawback that the light transmittance is necessarily 50% or less due to the transmission loss due to the polarizing plate. In addition, the longer the wavelength, the weaker the birefringence of the liquid crystal, and the longer distance is required to rotate the direction of polarization. Therefore, the liquid crystal plate must be thicker, which also reduces the light transmittance. To do. When the measurement is carried out by a sample analyzer, a decrease in light intensity passing through the analysis target sample or the reference sample also results in a decrease in detection sensitivity.

On the other hand, the thick film type is also called a scattering type and utilizes the scattering of light due to the disorder of the alignment of the liquid crystal that occurs when the polarity of the applied electric field is reversed. In a thick film type liquid crystal plate, the gap is 50 to several 1 in order to sufficiently scatter light.
It is necessary to make the thickness as thick as about 00 μm, but since a polarizing plate is not required, a large light transmittance can be obtained, and
There is an advantage that it can be manufactured at low cost.

Therefore, the thick film type ferroelectric liquid crystal plate is suitable as the infrared modulator of the infrared sample analyzer. However, in the conventional thick film type ferroelectric liquid crystal plate, it was difficult to increase the modulation frequency to several tens Hz or more. The reason is as follows. When the thick film type ferroelectric liquid crystal plate is used for light modulation, a constant voltage may be applied to the liquid crystal plate when transmitting light. At this time, the liquid crystal molecules are aligned in one direction to allow light to pass through without being scattered. On the other hand, when blocking the light, the positive and negative polarities of the voltage applied to the liquid crystal plate are reversed, but as described above, the blocking of the light utilizes a transient phenomenon of disorder of the liquid crystal alignment at the time of the polarity reversal. Therefore, the polarity reversal must be repeated throughout the interruption of the light. Therefore, when transmitting and blocking light, the applied voltage is changed as shown in FIG.

The problem here is that the liquid crystal has a low response speed when it shifts from a scattering state for blocking light to an aligned state for transmitting light, and takes several tens to several hundreds msec. Therefore, if the frequency of modulation is increased, it is necessary to move from the scattering state to the next scattering state before the scattering state is completely aligned, and the transmission state cannot be obtained. Usually, the so-called 1 / f noise peculiar to the semiconductor detector used in the infrared region gradually decreases as the frequency becomes higher as shown in FIG. 4, but exists up to about 100 Hz. Therefore, it is desirable to modulate at a frequency of about 100 Hz or higher in order to clearly distinguish the signal due to the infrared light that has passed through the sample from noise, but in the conventional thick film type ferroelectric liquid crystal plate, such a response is obtained. It was difficult to get.

The present invention has been made in order to solve such a problem, and realizes an infrared modulator using a liquid crystal plate by using a thick film type ferroelectric liquid crystal plate with greatly improved modulation frequency characteristics. However, the present invention provides a highly reliable sample analyzer that is compact and has no moving parts.

[0013]

SUMMARY OF THE INVENTION A first invention made to solve the above-mentioned problems is to allow light to pass through a sample cell containing a sample, and to measure the degree of absorption of the sample to determine the purpose of measurement in the sample. In a sample analyzer that measures the concentration of a component, a light modulating means for intensity-modulating the light passing through the sample cell or the light passing through the sample cell at a predetermined frequency is a) strong between a pair of opposing transparent electrode plates. A liquid crystal plate having a thick film liquid crystal cell in which a dielectric liquid crystal is sealed, and b) voltage applying means for applying a polarity inversion rectangular pulse voltage having a duty ratio of 55 to 90% to both electrode plates is used. It is what

A DC voltage may be superimposed on the polarity inversion rectangular pulse voltage applied by the voltage applying means to bias the average value of the maximum and minimum voltages to be positive or negative.

A second invention is characterized in that, in the sample analyzer, the liquid crystal plate is divided into a plurality of regions, and an independent electrode is formed in each region. .

[0016]

The thick film liquid crystal cell is constructed by enclosing a ferroelectric liquid crystal between a pair of electrode plates which are transparent to light (including infrared rays). Each electrode plate can be formed by depositing an ITO (indium tin oxide) film electrode on a normal glass plate, or by a single crystal / polycrystalline silicon substrate or a germanium substrate doped with impurities. The pair of electrode plates are opposed to each other with a gap of 50 to 150 μm provided, and the periphery is sealed. In order to stably maintain the gap length, it is desirable to sandwich a spacer between both electrode plates.

Between the two electrode plates, a Schiff base type, an azo type, an azoxy type, a benzoate type, a biphenyl type,
Terphenyl type, cyclohexylcarboate type,
Ferroelectric liquid crystals such as phenylcyclohexane-based, pyrimidine-based and oxane-based liquid crystals and a multi-component liquid crystal that is a mixture thereof are enclosed. A specific liquid crystal compound has the following formula (Formula 1)
The structure shown in FIG. The representative materials for these materials are "Structure and Physical Properties of Ferroelectric Liquid Crystals" published by Corona, p.229-239 "Ferroelectric Liquid Crystal Materials and Orientation Control Method"
It is described in.

[0018]

Embedded image

A rectangular pulse voltage whose polarity is inverted between positive and negative is applied between both electrode plates of the thick film liquid crystal cell. The duty ratio of this pulse voltage (the ratio of the period in which the polarity is positive in one cycle, or negative) The ratio of the period is 55-90%
And In addition, it is more preferably set to 65 to 75%.

When a DC voltage (currently, this initial state is positive) is applied to the ferroelectric liquid crystal, the liquid crystal molecules are aligned in a single direction along the electric field. In this case, light (including infrared rays) passes through the liquid crystal without being scattered. Instantaneous polarity of applied voltage (It is sufficient if the rise time is sharper than several μsec which is the general response speed of ferroelectric liquid crystal)
When the liquid crystal molecules are inverted negatively, the liquid crystal molecules cannot follow the change in the electric field, and the orientation changes randomly. In this case, since the light is scattered by the liquid crystal molecules, the amount of light transmitted through the liquid crystal plate is greatly reduced.

Light is scattered even when the orientation of liquid crystal molecules is slightly changed. Therefore, if the polarity of the applied voltage is returned to the original positive state before the orientation of the liquid crystal molecules is largely randomized, the liquid crystal can quickly return to the original unidirectional alignment state.

In FIG. 3, ZLI-1013 and 1011 manufactured by Merck Ltd. are used as the ferroelectric liquid crystal material, and ± 400 V,
500Hz polarity inversion rectangular pulse voltage (no bias)
Is the result of measuring the light transmittance when various duty ratios were applied. A He-Ne laser was used as a light source, and the transmitted light was detected by a photodiode (PD). (A) is a case where the duty ratio is 50%, and the light transmittance is low as a whole because the time for recovering the alignment of the liquid crystal molecules is insufficient in both positive and negative cycles.
By setting the duty ratio to 67% as in (b), the negative cycle (in the voltage waveform of FIG. 3, the upper part is represented as positive and the lower part is represented as negative. Note that the opposite is the same effect). The time will be shortened and the polarity will be reversed again to positive before the orientation of the liquid crystal molecules becomes sufficiently random. For this reason, the liquid crystal molecules are quickly returned to the normal alignment, and a sufficient alignment time is given in the positive cycle, so that a difference in transmittance appears. When the duty ratio is 75% as in (c), the difference becomes more remarkable. However, (d), (e),
When the duty ratio is further increased toward 100% as shown in (f), the polarity returns to the original state before the alignment of the liquid crystal molecules is disturbed, so that the opaque period is gradually shortened and finally disappears. Will end up.

From the above, the duty ratio is 5 when used as the light modulating means of the sample analyzer as in the present invention.
5 to 90% is suitable.

Since the optimum duty ratio within this range varies depending on the design condition of the thick film liquid crystal cell, the use condition, etc., it is practically made variable by incorporating a duty ratio adjusting circuit in the voltage applying means. It is desirable that the modulation degree (difference between the maximum value and the minimum value of the light transmittance) be maximized.

FIG. 4 shows frequency characteristics of the liquid crystal plate used in the present invention. The magnitude (amplitude) of the polarity reversal rectangular pulse voltage was measured at various values between ± 15V and ± 550V. Whereas when the duty ratio is 50% as in the conventional case, the degree of modulation decreases at about 50 Hz, the liquid crystal plate of the present invention has a frequency characteristic of 100 Hz or more regardless of the magnitude of the applied voltage. are doing. As described above, the 1 / f noise is extremely small at about 100 Hz or higher. Therefore, in the sample analyzer using the liquid crystal plate according to the present invention, the signal of light passing through the sample cell is clearly distinguished from the noise signal. Therefore, it becomes possible to perform highly sensitive sample analysis.

Although the absolute value of the maximum value (positive value) and the minimum value (negative value) of the polarity inversion rectangular pulse voltage may be equal, the maximum value (maximum value) can be obtained by superimposing a DC voltage. The average of the minimum values may be positively or negatively biased. The magnitude of the bias voltage is preferably about 20 to 50% of the amplitude (maximum value minus minimum value) of the rectangular pulse voltage. It is desirable that the bias voltage can be adjusted by incorporating a bias voltage adjusting circuit in the voltage applying means.

As in the second invention, by dividing the liquid crystal plate into a plurality of regions and forming an independent electrode in each region, the following usage can be achieved. First, in the case of a reference cell type sample analyzer in which a sample cell and a reference cell are arranged in parallel between a light source and a detector, an electrode is provided for each region corresponding to each cell, and polarities at different frequencies are provided to them. By applying the inverted rectangular pulse voltage, it becomes possible to distinguish the light signals that have passed through both cells. The same applies to the pseudo correlation spectroscopy type sample analyzer. Further, in the case of the single cell type sample analyzer, it becomes possible to simultaneously measure the concentrations of a plurality of components. That is, a plurality of electrodes and an interference filter are provided on the liquid crystal plate corresponding to each measurement target component (however, the interference filter may be provided separately from the liquid crystal plate), and each electrode has a polarity reversal of a different frequency. By applying the rectangular pulse voltage, the signals of the respective components can be distinguished.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the first invention will be described with reference to FIG. The infrared sample analyzer of the present embodiment is of the same single cell type as described in the section of the prior art, in which the sample to be measured and the reference sample are introduced into the sample cell 14 at different time zones, and the infrared rays are respectively detected. The transmittance is measured. Of the light from the light source 11, only the infrared rays having the absorption band wavelength of the measurement target component are allowed to pass by the interference filter 12. Interference filter 1
The infrared ray having the specific wavelength that has passed through 2 is absorbed by the infrared detector 15 in accordance with the amount of the target component contained in the sample introduced into the sample cell 14. In order to distinguish this detection signal from the stray light component generated by the background infrared light entering the detector 15, the sample cell 14
Infrared rays passing through are modulated by the modulator 13.

The modulator 13 is composed of a liquid crystal plate. As shown in FIG. 2, the modulator 13 of this embodiment includes two silicon substrates 131 and 132 and both silicon substrates 131 and 13.
Spacer 13 that maintains a constant gap (gap) of 2
4 and a liquid crystal 133 enclosed between both silicon substrates 131 and 132. Silicon substrates 131, 132
May be either single crystal or polycrystal. Since both silicon substrates 131 and 132 themselves serve as electrodes, gold vapor deposition is performed on a part thereof to form a round for taking out lead wires. An antireflection coating for preventing surface reflection of infrared rays is applied to the outer surfaces of the silicon substrates 131 and 132, and a rubbing treatment is applied to the inner surfaces thereof. 100 μm
The spacer 134 is sandwiched (that is, the cell gap is 100 μm), and the both sides are sealed with an epoxy adhesive,
Fill with liquid crystal in between. As the liquid crystal 133, ZLI-1013, 1011 manufactured by Merck Co., which is a commercially available ferroelectric liquid crystal material, was used, and a smectic C phase was obtained by heating at 120 ° C. and then gradually cooling. As the spacer, for example, Lumirror (registered trademark) polyester sheet manufactured by Toray Industries, Inc. can be used.

A ground is connected to one silicon substrate 131, and a voltage application circuit 137 is connected to the other silicon substrate. From the voltage application circuit 137, the frequency f (normally 50
The polarity reversal rectangular pulse voltage of about 0 Hz) is applied to the liquid crystal layer 133.
Apply to. The duty ratio of this pulse voltage is 5
The degree of modulation is adjusted to a maximum value between 5 and 90%.

As described above, in the infrared sample analyzer of the present embodiment, the modulator can be made much smaller than the conventional device, and neither vibration nor sound is generated. Further, since infrared rays are modulated at a sufficiently high frequency, they are not easily affected by background noise, and highly sensitive concentration measurement can be performed.

FIG. 5 shows a reference cell type infrared sample analyzer according to the second embodiment of the present invention. In this apparatus, a sample cell 24a and a reference cell 24b are arranged in parallel between a light source 21 and a detector 25, and a new oil (oil before deterioration) is used in the reference cell 24b when oil analysis is performed, and a gas is also used. When performing analysis, enclose a sample that does not absorb infrared rays of a specific wavelength such as dry nitrogen gas. The specific wavelength infrared light that has passed through the interference filter 22 enters both cells 24a and 24b at the same time, and is absorbed in the sample cell 24a according to the amount of the measurement target component in the sample, and is not absorbed in the reference cell 24b. This makes it possible to compensate the intensity change of the light source 21 itself.

The infrared sample analyzer of this embodiment uses a liquid crystal plate modulator 23 as shown in FIGS. In the modulator 23 of FIG. 7A, the ITO films 235 and 236 are formed on the inner surfaces of the high resistance silicon substrates or the glass plates 231 and 232.
The vapor deposition of a and 236b is used. This is because independent pulse voltages are applied to the two regions. That is, one silicon substrate or glass plate 232 is used for each cell 2
4a and 24b are divided into two regions, and electrodes 236a and 236b are independently formed. In addition, a voltage application circuit 237 is separately provided for each of the electrodes 236a and 236b.
a and 237b are connected. The electrode 235 on the opposite side may be common as shown in FIG. 7, or each electrode 236.
Separate electrodes corresponding to a and 236b may be formed.
As a result, the infrared rays passing through the sample cell 24a and the infrared rays passing through the reference cell 24b can be modulated at different frequencies f1 and f2, and the signals corresponding to both infrared rays can be simultaneously and distinguished from the output of the detector 25. You will be able to take it out. In the modulator 23 of FIG. 7B, two independent low resistance regions 236 are formed on the high resistance silicon substrate 231.
The same effect is obtained by providing a and 236b. In the modulator 23, the other high resistance silicon substrate 232 also functions as an interference filter.

In FIG. 5, the interference filter 22 is replaced by the modulator 2.
3 shows an example in which the modulator 23 is provided separately, but as shown in FIG. 7, one transparent electrode plate (glass plate) 231 of the liquid crystal plate constituting the modulator 23 is coated with a dielectric multilayer film coating 238.
By applying the above, an interference filter may be provided. As a result, the number of parts constituting the infrared sample analyzer can be reduced, the entire device can be made compact, and the cost can be reduced.

As another example of the second invention, a pseudo correlation spectroscopy type infrared sample analyzer is shown in FIG. In this device, a high-concentration measured sample cell 37 in which a sample containing a high-concentration measurement target component is placed between the light source 31 and one sample cell 34.
And a reference cell 38 in which a sample that does not absorb infrared rays of a specific wavelength such as new oil or dry nitrogen gas is placed. The specific wavelength infrared light that has passed through the interference filter 32 is
Almost 100% is absorbed in the high-concentration measured sample cell 37, while it is not absorbed in the reference cell 38. Therefore,
By passing both infrared rays through the sample cell 34 at the same time, the concentration of the component to be measured can be measured. In this device, when the sample cell 34 is contaminated by the contaminated component contained in the sample, both infrared rays have substantially the same influence, and the influences are canceled, so that highly accurate measurement can be performed.

In the infrared sample analyzer of this embodiment, the modulator shown in FIGS. 6 and 7 can be used as the modulator 33, and as shown in FIG. 9, a high concentration sample cell 43 to be measured.
7 and the reference cell 438 may be integrated into a unit 40. In the unit 40 of FIG. 9, 433
Is a liquid crystal plate for infrared modulation, and 432 is an interference filter with a dielectric multilayer coating.

Still another embodiment of the second invention (fourth embodiment)
As an example, the single cell type infrared sample analyzer shown in FIG. 1 using a liquid crystal plate having an electrode arrangement as shown in FIG. 10 as a modulator can be mentioned. This modulator 50
Then, one silicon substrate 51 sandwiching the liquid crystal layer is divided into a plurality of regions (six in the example of FIG. 10), and independently controllable electrodes 52a to 52f are provided in each region. These six electrodes 52a~52f each separate measurement target component (e.g. _{CH 3, CO 2, CO,} NO, NO 2, SO 2) corresponds to. Each electrode 52a to 52f of the silicon substrate 51
Further, on the back side of the region corresponding to, interference filters (dielectric multilayer film coatings) 53a to 53f that transmit only the absorption infrared rays of each measurement target component are formed.

The concentration measurement by this infrared sample analyzer is performed as follows. First, the reference sample is introduced into the sample cell 14, and the six electrodes 52a to 52f are supplied with the polarity reversal rectangular pulse voltages (the duty ratio is of course within the range of 55 to 90%) of different frequencies f1 to f6. The voltage is applied, and the infrared intensity is detected by the detector 15. By separating the detection signal at these modulation frequencies f1 to f6, it is possible to simultaneously measure the intensities of the infrared rays of specific wavelengths.
Next, the reference sample is discharged from the sample cell 14 and the analysis target sample is introduced. Similarly, by applying a polarity inversion rectangular pulse voltage of frequencies f1 to f6 to each of the electrodes 52a to 52f and separating the infrared detection signal at these modulation frequencies f1 to f6, the concentrations of a plurality of components of the sample are simultaneously measured. be able to.

[0039]

In the sample analyzer according to the present invention, a liquid crystal plate is used in order to modulate the intensity of light passing through the sample, instead of the conventional mechanical chopper plate. For this reason,
A compact and highly reliable sample analyzer without sound or vibration can be provided. In addition, a normal liquid crystal plate cannot perform high-speed modulation as required in a sample analyzer, but in the present invention, by setting the duty ratio of the polarity inversion rectangular pulse voltage to be applied to an appropriate range,
It enabled such high-speed modulation.

Further, as in the second invention, by dividing the liquid crystal plate into a plurality of regions and forming an independent electrode in each region, it becomes possible to perform modulation at a plurality of frequencies at the same time. It can also be applied to a reference cell type sample analyzer, a pseudo-correlation spectroscopy type sample analyzer, and the like. Furthermore,
It also becomes possible to simultaneously measure the concentrations of a plurality of components contained in the sample.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a single-cell infrared sample analyzer according to a first embodiment.

FIG. 2 is a sectional view of a liquid crystal plate which is an infrared modulator used in the first embodiment.

FIG. 3 is a graph showing changes in light transmittance when the duty ratio of the polarity inversion rectangular pulse voltage applied to the thick film type ferroelectric liquid crystal plate is variously changed.

FIG. 4 is a graph showing frequency characteristics of a liquid crystal plate of the present invention and a conventional liquid crystal plate, and frequency characteristics of background noise.

FIG. 5 is a schematic configuration diagram of a reference cell type infrared sample analyzer of the second embodiment.

FIG. 6 is a front view of a liquid crystal plate which is an infrared modulator used in the second embodiment.

FIG. 7 is a cross-sectional view of the liquid crystal plate incorporating an interference filter.

FIG. 8 is a schematic configuration diagram of a pseudo-correlation spectroscopy type sample analyzer of the third embodiment.

FIG. 9 is a cross-sectional view of an interference filter / sample cell integrated liquid crystal plate used in a third embodiment.

FIG. 10 is a front view of a liquid crystal plate which is an infrared modulator used in a fourth embodiment.

FIG. 11 is a schematic configuration diagram of a conventional single-cell infrared sample analyzer.

FIG. 12 is a front view (a) of a rotary chopper type infrared modulator used in a conventional sample analyzer and a graph showing its modulation degree.

FIG. 13 is a time chart showing a method of infrared modulation using a conventional liquid crystal plate.

[Explanation of symbols]

11, 21, 31, 61 ... Light source 12, 22, 32, 62 ... Interference filter 13, 23, 33 ... Liquid crystal plate infrared modulator 131, 132 ... Silicon substrate 133 ... Liquid crystal layer 134 ... Spacer 137 ... Voltage applying circuit 231, 232 ... Glass plate 235, 236a, 236b ... Electrode 237a ... Voltage application circuit 238 ... Dielectric multilayer film coating (interference filter) 40 ... Infrared modulator unit 432 ... Dielectric multilayer film coating (interference filter) 433 ... Liquid crystal plate 437 ... High-concentration measured sample cell 438 ... Reference cell 14, 24a, 34, 64 ... Sample cell 24b ... Reference cell 15, 25, 35, 65 ... Infrared detector 37 ... High-concentration measured sample cell 38 ... Reference cell 50 ... Infrared Modulator 51 ... Silicon substrate 52a-52f ... Electrode 53a-53f ... Dielectric multilayer film coat Ingu (interference filter) (back)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G02F 1/133 560 1/141

Claims (2)

[Claims] 1. Light is passed through a sample cell containing a sample,
In a sample analyzer that measures the concentration of a measurement target component in a sample by measuring its absorbance, a light modulating means that intensity-modulates light passing through the sample cell or passing through the sample cell at a predetermined frequency , A) a thick film liquid crystal cell in which a ferroelectric liquid crystal is sealed between a pair of opposing transparent electrode plates, and b) a polarity reversal rectangular pulse voltage with a duty ratio of 55 to 90%, or the polarity. A sample analyzer characterized by using a liquid crystal plate having a voltage applying means for applying a voltage obtained by superimposing a DC bias voltage on an inverted rectangular pulse voltage. 2. The sample analyzer according to claim 1, wherein the liquid crystal plate is divided into a plurality of regions, and an independent electrode is formed in each region.