JPS6321130B2 - - Google Patents
Info
- Publication number
- JPS6321130B2 JPS6321130B2 JP54083987A JP8398779A JPS6321130B2 JP S6321130 B2 JPS6321130 B2 JP S6321130B2 JP 54083987 A JP54083987 A JP 54083987A JP 8398779 A JP8398779 A JP 8398779A JP S6321130 B2 JPS6321130 B2 JP S6321130B2
- Authority
- JP
- Japan
- Prior art keywords
- photoacoustic
- light source
- light
- signal
- electric
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000523 sample Substances 0.000 claims description 35
- 238000010895 photoacoustic effect Methods 0.000 claims description 24
- 238000005259 measurement Methods 0.000 claims description 23
- 239000004065 semiconductor Substances 0.000 claims description 18
- 230000010355 oscillation Effects 0.000 claims description 14
- 230000003287 optical effect Effects 0.000 claims description 8
- 239000013074 reference sample Substances 0.000 claims description 8
- 230000001360 synchronised effect Effects 0.000 claims description 5
- 238000010521 absorption reaction Methods 0.000 claims description 4
- 230000003595 spectral effect Effects 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims 1
- 238000004867 photoacoustic spectroscopy Methods 0.000 claims 1
- 238000001514 detection method Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000001834 photoacoustic spectrum Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- AEEAZFQPYUMBPY-UHFFFAOYSA-N [I].[W] Chemical compound [I].[W] AEEAZFQPYUMBPY-UHFFFAOYSA-N 0.000 description 1
- 230000005534 acoustic noise Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000000295 emission spectrum Methods 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000002235 transmission spectroscopy Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
Description
【発明の詳細な説明】
本発明は、光音響効果（Photoacoustic
Effect）を利用して、試料の光音響スペクトルを
検出する分析装置に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention provides photoacoustic effects.
The present invention relates to an analyzer that detects the photoacoustic spectrum of a sample using the photoacoustic spectrum.
光音響効果は1881年チンダル（Tyndall）、ベ
ル（Bell）、レントゲン（Ro¨ntogen）らによつて
発見され、試料に音響周波数で強度変調した光を
照射すると、試料から光の変調周波数に応じた音
声波が発生する現象である。この音声波を検出す
ることによつて光透過型分光分析では測定困難な
微弱な光吸収特性を測定することも可能となる。
また、測定試料が気体の場合、鋭い吸収線をもつ
ので、照射光の波長を気体の吸収線と一致させて
おけば、選択的に気体の分析を行うこともでき
る。 The photoacoustic effect was discovered in 1881 by Tyndall, Bell, and Roentgen. When a sample is irradiated with light whose intensity is modulated at an acoustic frequency, the photoacoustic effect emitted from the sample responds to the modulated frequency of the light. This is a phenomenon in which sound waves are generated. By detecting this audio wave, it is also possible to measure weak light absorption characteristics that are difficult to measure with light transmission spectrometry.
Furthermore, when the measurement sample is a gas, it has a sharp absorption line, so if the wavelength of the irradiation light is made to match the absorption line of the gas, it is possible to selectively analyze the gas.
この光音響効果を利用した分析装置は、通常の
分析装置と同様に、光源、試料室およびデータ処
理系から構成されている。光源としては、従来は
Xe−アークランプ、沃素タングステンランプ、
グローバーランプなどがモノクロメータを組合せ
て使用している。その基本構成をブロツク図に示
すと第１図のごとくなる。図において、１はXe
ランプ、１0はランプへの供給電力源、２は集光
レンズ、３はモノクロメータ、４は音声周波数で
光源から放射された光を断続するメカニカルチヨ
ツパ、５は集光レンズ、６は光音響セル、７はプ
リ・アンプリフアイヤ（Pfeamplifier）、８はロ
ツク・インアンプリフアイヤ（Loc in
Amplifier）、９は記録計である。上記の光音響
セルには第２図に示すように光透過用窓１０0を
有し、空間１１内には気体と共に試料Ｓ及びマイ
クロホン１３を気密に封入する。セル内の試料が
チヨツパ周波数で変調された光を吸収すると、チ
ヨツパ周波数に応じた熱が発生し、セル内の気体
を伝送媒体として圧力波が伝達されるのでこれを
マイクロホン（音響電気変換器）で検出し、その
電気信号をプリ・アンプリフアイヤ７で増巾、さ
らにその電気出力をロツク・イン・アンプリフア
イヤで位相検波を行いチヨツパ周波数と同期した
電気信号を出力して記録計に入れ、試料の光音響
スペクトルを観測する。 Analyzers that utilize this photoacoustic effect are comprised of a light source, a sample chamber, and a data processing system, similar to ordinary analyzers. Conventionally, as a light source,
Xe-arc lamp, iodine tungsten lamp,
Grover lamps are used in combination with a monochromator. The basic configuration is shown in a block diagram as shown in FIG. In the figure, 1 is Xe
lamp, 1 0 is a power supply source to the lamp, 2 is a condenser lens, 3 is a monochromator, 4 is a mechanical chopper that cuts off the light emitted from the light source at the audio frequency, 5 is a condenser lens, 6 is a Photoacoustic cell, 7 is a pre-amplifier, 8 is a lock-in amplifier.
Amplifier), 9 is a recorder. The photoacoustic cell described above has a light transmission window 100 as shown in FIG. 2, and a sample S and a microphone 13 are hermetically sealed in the space 11 together with a gas. When the sample in the cell absorbs light modulated at the chipper frequency, heat corresponding to the chipper frequency is generated, and pressure waves are transmitted using the gas in the cell as a transmission medium, which is transmitted through a microphone (acoustoelectric transducer). The electrical signal is amplified by the pre-amplifier 7, and the electrical output is phase-detected by the lock-in amplifier, and an electrical signal synchronized with the chopper frequency is output and input into the recorder. , observe the photoacoustic spectrum of the sample.
上記の装置においては、検出感度をよくするた
め光源として数百〜1KW程度のXeランプなどを
使用するので、装置が大型となる上、冷却フアン
を使用する必要があるため、その音響雑音が影響
しSN比が低下せざるを得ず、電力の消費量も多
い。また、照射光を一定の周波数で変調するため
メカニカル・チヨツパを必要とする。その結果、
メカニカル・チヨツパの振動による雑音のため
SN比を向上させることが困難である。 In the above equipment, a Xe lamp of several hundred to 1KW is used as a light source to improve detection sensitivity, which makes the equipment large and requires the use of a cooling fan, which has an impact on acoustic noise. However, the signal-to-noise ratio inevitably decreases, and power consumption also increases. Additionally, a mechanical chopper is required to modulate the irradiated light at a constant frequency. the result,
Due to noise caused by mechanical vibration
It is difficult to improve the S/N ratio.
さらに、照射光を単色化するためモノクロメー
タが必要となる。 Furthermore, a monochromator is required to make the irradiation light monochromatic.
また、SN比を向上させるため、光音響セルの
構造を音響的共鳴効果を有せしめることも行われ
ている（以下、この構造の光音響セルを共鳴型光
音響セルという）。これは、セルの長さを入射光
の変調周波数に共鳴させるようにしたものであ
る。つまり、セル内に発生した圧力波が定在波を
作るように選ぶことにより感度を非常に上げるこ
とができる。すなわち、セルの長さをｌとする
と、
ｌ＝λ／２＝ｃ／2
ここにλは圧力波の波長、ｃは気体内の圧力波
の速度、は変調周波数（Hz）である。 Furthermore, in order to improve the SN ratio, the structure of a photoacoustic cell has been made to have an acoustic resonance effect (hereinafter, a photoacoustic cell with this structure is referred to as a resonant photoacoustic cell). This is made so that the length of the cell resonates with the modulation frequency of the incident light. In other words, sensitivity can be greatly increased by selecting the pressure waves generated within the cell to form standing waves. That is, if the length of the cell is l, then l = λ/2 = c/2 where λ is the wavelength of the pressure wave, c is the speed of the pressure wave in the gas, and is the modulation frequency (Hz).
その一例を第３図に示す。第３図において、１
０0は光透過用窓、１１は試料収納室、１２はマ
イクロホン収納室（容積V1）、１３はマイクロホ
ンである。試料収納室１１（容積V2）とマイク
ロホン収納室１２とは管１４（半径Ｄ、長さＬ）
で連結され、セルの容積はさほど大きくない。こ
のセルは、下記の周波数0で共鳴する。 An example is shown in FIG. In Figure 3, 1
0 0 is a light transmission window, 11 is a sample storage chamber, 12 is a microphone storage chamber (volume V 1 ), and 13 is a microphone. The sample storage chamber 11 (volume V 2 ) and the microphone storage chamber 12 are connected to a tube 14 (radius D, length L).
The cell volume is not very large. This cell resonates at frequency 0 below.
ここで、ｃはセル内気体空間の音速である。し
たがつて、入射光の変調周波数（チヨツパ周波
数）nを0に一致させると、発生する光音響信号
は共鳴効果によりＱ（共振のＱ値）倍強調されSN
比を向上させることができる。第３図のセルで
は、試料台１５を上下させるとV2が可変にでき
るので、共鳴周波数を任意に変化させることがで
きる。しかし、上記の共鳴型セルも、セルの温度
変化や、試料形状の違いにより共鳴周波数が変動
するので安定な動作が得難い欠点がある。 Here, c is the speed of sound in the gas space within the cell. Therefore, when the modulation frequency (chopper frequency) n of the incident light is made equal to 0 , the generated photoacoustic signal is enhanced by a factor of Q (the Q value of resonance) due to the resonance effect, and the SN
The ratio can be improved. In the cell shown in FIG. 3, V2 can be varied by moving the sample stage 15 up and down, so the resonance frequency can be changed arbitrarily. However, the above-mentioned resonant cell also has the drawback that stable operation is difficult to obtain because the resonant frequency fluctuates due to changes in the temperature of the cell or differences in sample shape.
なお、この種の技術として関連するものには例
えば特開昭50−71388号、特開昭53−47886号、特
開昭54−36778号、特開昭54−59188号等が挙げら
れる。 Incidentally, related techniques of this type include, for example, JP-A-50-71388, JP-A-53-47886, JP-A-54-36778, and JP-A-54-59188.
本発明は、光音響分光分析装置における上記の
問題点を解決することを目的とするものである。
上記目的を達成するため本発明では、光源および
光源を駆動する電力源と、該電力源の電力を所要
の周波数で変調する信号を発する変調用周波数発
振器と、上記光源の変調光を受光し所定の測定試
料を封入する光音響セルと、この光音響セル内の
測定試料に発生した光音響効果を検出する音響電
気変換器と、この音響電気変換器で発生した電気
信号を同期検波して前記変調用周波数発振器の発
振出力信号との位相差を検出し、この位相差の電
気信号を出力として発生する電気手段と、当該出
力を受け前記光音響セル内に生じた光音響効果を
記録する記録手段とを有する光音響分光分析装置
において、光音響セルを音響的に共鳴構造を有せ
しめたものを使用し、この共鳴型光音響セル内の
測定試料に生じた光音響効果を音響電気変換手段
で電気信号とし、当該電気信号を二分し、第１の
電気回路において光源駆動電力源の変調用周波数
と当該電気信号との間の位相差を検出し、両者の
位相差を直流電圧として前記変調用周波数発振器
に負帰還し、当該変調用周波数発振器の発振周波
数を上記共鳴型光音響セルの共鳴周波数に整合せ
しめ、第２の電気回路においては、上記音響電気
変換器の電気信号をロツク・イン・アンプリフア
イヤに入力し、上記変調用周波数発振器の発振周
波数と同期した電気信号を出力させて記録計に導
入し、測定試料に生じた光音響効果を記録するよ
うにして、共鳴型光音響セルにおける共鳴周波数
の変動の影響を除去し安定な測定を行いうるよう
にしたものである。 An object of the present invention is to solve the above-mentioned problems in a photoacoustic spectrometer.
In order to achieve the above object, the present invention includes a light source, a power source for driving the light source, a modulation frequency oscillator for emitting a signal for modulating the power of the power source at a predetermined frequency, and a modulation frequency oscillator for receiving modulated light from the light source and providing a predetermined frequency. a photoacoustic cell enclosing a measurement sample; an acoustoelectric transducer for detecting the photoacoustic effect generated on the measurement sample within the photoacoustic cell; and synchronous detection of the electrical signal generated by the acoustoelectric transducer to detect the An electric means for detecting a phase difference with an oscillation output signal of a modulation frequency oscillator and generating an electric signal of this phase difference as an output, and a record for recording a photoacoustic effect generated in the photoacoustic cell upon receiving the output. In the photoacoustic spectrometer, a photoacoustic cell having an acoustically resonant structure is used. The electric signal is divided into two, the phase difference between the modulation frequency of the light source driving power source and the electric signal is detected in a first electric circuit, and the phase difference between the two is converted into a DC voltage and the electric signal is divided into two. Negative feedback is applied to the modulation frequency oscillator to match the oscillation frequency of the modulation frequency oscillator to the resonant frequency of the resonant photoacoustic cell, and the second electric circuit locks in the electrical signal of the acoustoelectric transducer.・Resonant photoacoustic This eliminates the influence of fluctuations in the resonant frequency of the cell, allowing stable measurements.
また、本発明では、上記目的を達成するため、
上記した前提要件を備えた光音響分光分析装置に
おいて、光源の発光波長を制御する発光波長制御
手段と、光源から放射された変調光の一部を光ビ
ーム・スプリツタを介して分離し、その分離光路
中に、当該変調光を受光し平坦な分光特性を有す
る基準試料を収納した光音響セルと、基準試料に
生じた光音響効果を検出する音響電気変換器と、
該音響電変換器に生じた電気信号を同期検波して
前記変調用周波数発振器の発振出力信号との位相
差を電気信号として出力する電気的手段と、該電
気的手段の出力の振巾を基準の振巾と比較し、両
者の差に比例した電気信号を出力する電気手段
と、この電気信号を光源駆動電力源に入れ駆動電
力の変調度を調整するようにしたものである。 Moreover, in the present invention, in order to achieve the above object,
In a photoacoustic spectrometer equipped with the above-mentioned prerequisites, there is provided an emission wavelength control means for controlling the emission wavelength of the light source, and a part of the modulated light emitted from the light source is separated via a light beam splitter. a photoacoustic cell that receives the modulated light and houses a reference sample having flat spectral characteristics in an optical path; an acoustoelectric transducer that detects a photoacoustic effect generated on the reference sample;
an electric means for synchronously detecting the electric signal generated in the acoustoelectric transducer and outputting the phase difference with the oscillation output signal of the modulation frequency oscillator as an electric signal; and a reference for the amplitude of the output of the electric means. The electric means outputs an electric signal proportional to the difference between the two amplitudes, and this electric signal is input to the light source driving power source to adjust the modulation degree of the driving power.
また、本発明の光音響効果は、音響周波数の領
域のみならず、もつと高い周波数の周波数領域に
も利用できる。 Further, the photoacoustic effect of the present invention can be utilized not only in the acoustic frequency range but also in the higher frequency range.
以下、実施例について説明する。 Examples will be described below.
実施例 １
第４図は半導体光源を用いた光音響分光分析装
置の第１の実施例を示す。図において、１は半導
体光源、１0は光源の駆動電力源、５は集光レン
ズ６は共鳴型光音響セル、７はプリ・アンプリフ
アイヤ、８はロツク・イン・アンプリフアイヤ、
１７は増巾器、１８はローパス・フイルタ、１９
は位相検波器、１６は駆動電力源変調用周波数発
振器、９は光音響効果記録計である。第４図は光
源として、発光ダイオード（たとえばGaAs）、
半導体レーザ、ダイオード（可変波長半導体レー
ザ・ダイオードも含む。）を使用したものについ
て説明する。光源から放射する光の強度変調は、
半導体光源に対する駆動電圧を、変調用周波数発
振器１６からの発振周波数nに同期して変調する
ことによつて行う。光源１から放射された変調光
は集光レンズ５によつて光音響セル６に照射され
る。光音響セル内には測定試料を収納しておく。
しかも、この光音響セルは一定の周波数0に音響
共鳴効果をもつ構造のものとする。今、このよう
な共鳴型光音響セル内の試料に変調周波数nの光
が照射されると、試料はこの照射光を吸収し、熱
を生じるので、セル内の気体に照射光の変調周波
数に応じた圧力波を発生させる。この圧力波をセ
ル内に設置した音響電気変換器（たとえばマイク
ロホン）で検出し、その電気信号をプリ・アンプ
リフアイヤ７で増巾し、その出力を二つの回路に
分離し、第１の電気回路においては、位相検波器
１９はセルの電気信号と変調周波数発振器から発
振される電気信号との間の位相差を検知して出力
させ、その出力はプリ・アンプリフアイヤで増巾
した後、低域フイルタ１８で直流信号に変換して
変調用周波数発振器１６に負帰還し、その発振周
波数nを0と常に一致するようにコントロールす
る。この変調用周波数発振器の出力電圧は光源の
駆動電力源１0で増巾され、周波数発振器の出力
電圧の周波数に対応した変調電力を発生し、半導
体光源１の発光強度を変調する。他方、第２の電
気回路においては、音響電気変換器の電気信号を
ロツク・イン・アンプリフアイヤ８で同期検波し
て変調用周波数発振器１６の発振出力信号との位
相差を電気信号として出力させて記録計９に導
き、試料に生じた光音響効果を記録する。Example 1 FIG. 4 shows a first example of a photoacoustic spectrometer using a semiconductor light source. In the figure, 1 is a semiconductor light source, 10 is a power source for driving the light source, 5 is a condensing lens 6 is a resonant photoacoustic cell, 7 is a pre-amplifier, 8 is a lock-in amplifier,
17 is an amplifier, 18 is a low-pass filter, 19
1 is a phase detector, 16 is a frequency oscillator for modulating the driving power source, and 9 is a photoacoustic effect recorder. Figure 4 shows a light emitting diode (e.g. GaAs) as a light source,
A device using a semiconductor laser and a diode (including a variable wavelength semiconductor laser diode) will be explained. The intensity modulation of light emitted from a light source is
This is done by modulating the drive voltage for the semiconductor light source in synchronization with the oscillation frequency n from the modulation frequency oscillator 16. Modulated light emitted from the light source 1 is irradiated onto the photoacoustic cell 6 by the condenser lens 5 . A measurement sample is stored in the photoacoustic cell.
Moreover, this photoacoustic cell has a structure that has an acoustic resonance effect at a certain frequency of 0 . Now, when a sample in such a resonant photoacoustic cell is irradiated with light of modulation frequency n , the sample absorbs this irradiation light and generates heat, which causes the gas in the cell to adjust to the modulation frequency of the irradiation light. Generates corresponding pressure waves. This pressure wave is detected by an acoustoelectric transducer (for example, a microphone) installed in the cell, and the electrical signal is amplified by a preamplifier 7, and its output is separated into two circuits. In the circuit, a phase detector 19 detects and outputs the phase difference between the electrical signal of the cell and the electrical signal oscillated from the modulation frequency oscillator, and the output is amplified by a pre-amplifier, and then The low-pass filter 18 converts the signal into a DC signal, which is negatively fed back to the modulation frequency oscillator 16, and controls its oscillation frequency n to always match 0 . The output voltage of this frequency oscillator for modulation is amplified by the drive power source 1 0 of the light source to generate modulation power corresponding to the frequency of the output voltage of the frequency oscillator, thereby modulating the emission intensity of the semiconductor light source 1. On the other hand, in the second electric circuit, the lock-in amplifier 8 synchronously detects the electric signal of the acoustoelectric transducer and outputs the phase difference with the oscillation output signal of the modulation frequency oscillator 16 as an electric signal. and the photoacoustic effect produced on the sample is recorded.
この実施例では、従来装置のようにメカニカ
ル・チヨツパや、Xeランプを使用していないの
で、雑音の発生がなく、また冷却フアンを使用す
る必要もない故、装置を小型化でき、SN比を向
上させることができる。 This embodiment does not use a mechanical chopper or a Xe lamp unlike conventional equipment, so there is no noise generation, and there is no need to use a cooling fan, so the equipment can be made smaller and the SN ratio can be improved. can be improved.
その上、この装置によると、さらに安定にSN
比を向上させることができる。 Moreover, this device provides even more stable SN
The ratio can be improved.
実施例 ２
第５図に本発明の第２の実施例を示す。図にお
いて、１は可変波長半導体レーザ・ダイオード
（Pb1-xSnxTe、０＜Ｘ＜１）、１0は光源の駆動電
力源、５は集光レンズ、２１は光ビーム・スプリ
ツタ、６は測定試料を収納した光音響セル、６′
は平坦な分光特性を有する基準試料を収納した光
音響セル、８および８′はロツク・イン・アンプ
リフアイヤ、９は記録計、２２は光源の放射光の
波長域を制御する発光波長制御装置、２３は比較
回路である。Embodiment 2 FIG. 5 shows a second embodiment of the present invention. In the figure, 1 is a tunable wavelength semiconductor laser diode (Pb 1-x Sn x Te, 0<X<1), 10 is a driving power source for the light source, 5 is a condenser lens, 21 is a light beam splitter, 6 is the photoacoustic cell containing the measurement sample, 6'
8 and 8' are lock-in amplifiers; 9 is a recorder; and 22 is an emission wavelength control device that controls the wavelength range of the emitted light from the light source. , 23 is a comparison circuit.
本実施例では、光源１に可変波長半導体レー
ザ・ダイオードとして、Pb1-xSnxTe（ただし、０
＜Ｘ＜１）を使用する。そして、この光源を周波
数nの周波数で発振する変調用周波数発振器の信
号で変調した駆動電源で励起する。さらに、光源
は、発光波長制御装置２２により、その発光波長
を所要の発光スペクトルを放射するようにする。
放射されたレーザ光は集光レンズ５で集束の後、
光ビーム・スプリツタ２１により第１の光ビーム
と第２の光ビームに分離する。第１の光ビーム路
には、カーボンのごとく広波長域に亘つて平坦な
吸収特性をもつ試料を基準試料として収納した光
音響セル６′を配置しておき、基準試料が変調レ
ーザ光を吸収して生じる光音響効果は、セル内に
設置した音響電気変換器（マイクロホン）で検出
し、得られる電気信号はロツク・イン・アンプリ
フアイヤ８′で同期検波して変調用周波数発振器
１６の発振周波数nとの間の位相検出を行い、n
と同期する電気信号を出力させて比較回路２３に
導き、基準の振巾との差に比例する直流電圧を出
力させて駆動電源１0に入れ、光源の発光波長の
違いによる光強度の振巾の違いを駆動電源の変調
度を調節して補償するようにする。他方、第２の
光ビーム路中には測定試料を収納した光音響セル
６を配置し、変調されたレーザ光を吸収して測定
試料中に生じる光音響効果をセル内の音響電気変
換器で検出し、得られる電気信号はロツク・イ
ン・アンプリフアイヤ８に導き、変調用周波数発
振器１６の発振する周波数nとの間の位相検波を
行い、nと同期する電気信号を出力させて記録計
９に導き、測定試料に生じた光音響効果を記録す
るものである。 In this example, the light source 1 uses Pb 1-x Sn x Te (however, 0
<X<1). Then, this light source is excited with a drive power modulated by a signal from a modulation frequency oscillator that oscillates at a frequency n . Furthermore, the light source is controlled by the emission wavelength control device 22 to control the emission wavelength to emit a desired emission spectrum.
After the emitted laser light is focused by a condenser lens 5,
A light beam splitter 21 separates the light beam into a first light beam and a second light beam. In the first optical beam path, a photoacoustic cell 6' containing a sample, such as carbon, which has flat absorption characteristics over a wide wavelength range, is arranged as a reference sample, and the reference sample absorbs the modulated laser beam. The resulting photoacoustic effect is detected by an acoustoelectric transducer (microphone) installed in the cell, and the resulting electrical signal is synchronously detected by a lock-in amplifier 8' and oscillated by a modulating frequency oscillator 16. Perform phase detection between frequency n and n
An electric signal synchronized with the amplitude is outputted and guided to the comparator circuit 23, and a DC voltage proportional to the difference from the reference amplitude is outputted and the drive power source 10 is turned on to calculate the amplitude of the light intensity due to the difference in the emission wavelength of the light source. This difference is compensated for by adjusting the modulation degree of the drive power source. On the other hand, a photoacoustic cell 6 containing a measurement sample is arranged in the second optical beam path, and the photoacoustic effect produced in the measurement sample by absorbing the modulated laser beam is transmitted by an acoustoelectric transducer in the cell. The electrical signal obtained by the detection is guided to the lock-in amplifier 8, where phase detection is performed between it and the frequency n oscillated by the modulation frequency oscillator 16, and an electrical signal synchronized with n is outputted to the recorder. 9 and record the photoacoustic effect produced in the measurement sample.
本実施例の装置によると、半導体レーザの発光
波長の違いのため生じる放射光の振巾変化が測定
試料の光音響効果の測定に及ぼす影響を除去する
ことができるのみならず、従来の光音響分光分析
装置に必要とされていたモノクロ・メータも不要
となるなど装置の小型化及び簡便化を図ることが
できる。 According to the apparatus of this embodiment, it is possible not only to eliminate the influence of the amplitude change of the emitted light caused by the difference in the emission wavelength of the semiconductor laser on the measurement of the photoacoustic effect of the measurement sample, but also to eliminate the influence of the conventional photoacoustic The monochrome meter required in a spectroscopic analyzer is no longer necessary, and the device can be made smaller and simpler.
実施例 ３
第６図に本発明の第３の実施例を示す。図にお
いて、１は可変波長半導体レーザ・ダイオード
（例えばPb1-xSnxTe、０≦ｘ≦１）、５は集光レ
ンズ、２１は光ビームスプリツタ、６は測定試料
を収納した共鳴型光音響セル、６′は基準試料収
納光音響セル、７はプリ・アンプリフアイヤ、８
はロツク・イン・アンプリフアイヤ、９は記録
計、１８はローパスフイルタ、１９は位相検波
器、２２は可変波長半導体レーザ・ダイオードの
発光波長走査装置、２３は比較回路である。実施
例２（第５図の光音響分光分析装置）の装置との
差異は、第６図に示す第２の光ビーム路中に配置
した光音響セル６として共鳴型光音響セルを使用
したことにある。この結果、光音響セルの変動し
た共鳴周波数0′と周波数発振器１６の変調周波
数nとの差が、共鳴周波数0′の信号とnの発振
器出力信号との間の位相差に対応し、それを位相
検波器１９で検出した後、ローパスフイルタ１８
を介して周波数発振器１６に負帰還し、0′−n
に相当する周波数の喰い違い分の周波数を変調用
周波数発振器から発振せしめる。Embodiment 3 FIG. 6 shows a third embodiment of the present invention. In the figure, 1 is a tunable wavelength semiconductor laser diode (for example, Pb 1-x Sn x Te, 0≦x≦1), 5 is a condenser lens, 21 is a light beam splitter, and 6 is a resonant type that houses the measurement sample. Photoacoustic cell, 6' is a reference sample storage photoacoustic cell, 7 is a pre-amplifier, 8
9 is a lock-in amplifier, 9 is a recorder, 18 is a low-pass filter, 19 is a phase detector, 22 is an emission wavelength scanning device of a variable wavelength semiconductor laser diode, and 23 is a comparison circuit. The difference from the device of Example 2 (photoacoustic spectrometer shown in FIG. 5) is that a resonant photoacoustic cell was used as the photoacoustic cell 6 placed in the second optical beam path shown in FIG. It is in. As a result, the difference between the varied resonance frequency 0 ' of the photoacoustic cell and the modulation frequency n of the frequency oscillator 16 corresponds to the phase difference between the signal at resonance frequency 0 ' and the oscillator output signal at n , which After detection by the phase detector 19, the low pass filter 18
negative feedback to the frequency oscillator 16 via 0 ′− n
The modulation frequency oscillator oscillates a frequency corresponding to the difference in frequency.
以上記載した本発明の光音響分光分析装置は従
来の光音響分光分析装置と比較して次の利点があ
る。 The photoacoustic spectrometer of the present invention described above has the following advantages over conventional photoacoustic spectrometers.
(1) 半導体光源を使用するので装置を小型化でき
る。(1) Since a semiconductor light source is used, the device can be made smaller.
(2) 光源への駆動電力を変調して放射光を変調す
る方式をとつているから、メカニカル・チヨツ
パーのような雑音の影響を除去することができ
る。(2) Since the method uses a method of modulating the driving power to the light source to modulate the emitted light, it is possible to eliminate the effects of noise such as mechanical choppers.
(3) 特に可変波長半導体レーザ・ダイオードを使
用する場合は、モノクロメータが不要となる。(3) Especially when using a tunable semiconductor laser diode, a monochromator is not required.
(4) 光源の変調周波数を光音響セルの共鳴周波数
と常に整合するようにコントロールする（負帰
還する）ので、安定した測定ができる。(4) The modulation frequency of the light source is controlled to always match the resonance frequency of the photoacoustic cell (negative feedback), allowing stable measurements.
第１図は、従来の光音響分光分析装置の基本構
成を示すブロツク図、第２図は光音響セルの縦断
面図、第３図は共鳴型光音響セルの縦断面図、第
４図は本発明の光音響分光分析装置の一実施例の
構成を示すブロツク図、第５図は本発明の光音響
分光分析装置の他の実施例の構成を示すブロツク
図、第６図は本発明の光音響分光分析装置の第３
の実施例の構成を示すブロツク図である。
第１図から第６図において、１……光源、１0
……光源駆動電力源、６，６′……光音響セル、
７……プリ・アンプリフアイヤ、８，８′……ロ
ツク・イン・アンプリフアイヤ、９……記録計、
１６……駆動電力変調用周波数発振器、１９……
位相検波器、２１……光ビーム・スプリツタ、２
２……光源の発光波長制御装置、２３……比較回
路である。
Figure 1 is a block diagram showing the basic configuration of a conventional photoacoustic spectrometer, Figure 2 is a vertical cross-sectional view of a photoacoustic cell, Figure 3 is a vertical cross-sectional view of a resonant photoacoustic cell, and Figure 4 is a vertical cross-sectional view of a resonant photoacoustic cell. FIG. 5 is a block diagram showing the configuration of another embodiment of the photoacoustic spectrometer of the present invention. FIG. 6 is a block diagram showing the configuration of another embodiment of the photoacoustic spectrometer of the present invention. The third part of the photoacoustic spectrometer
FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention. In Figures 1 to 6, 1... light source, 1 0
...Light source driving power source, 6,6'...Photoacoustic cell,
7...Pre-amplifier, 8,8'...Lock-in amplifier, 9...Recorder,
16... Frequency oscillator for drive power modulation, 19...
Phase detector, 21... Optical beam splitter, 2
2... Light emission wavelength control device of the light source, 23... Comparison circuit.
Claims (1)
源の電力を所要の周波数で変調する信号を発する
変調用周波数発振器と、上記光源の変調光を受光
し所定の測定試料を封入する光音響セルと、この
光音響セル内の測定試料に発生した光音響効果を
検出する音響電気変換器と、この音響電気変換器
で発生した電気信号を同期検波して前記変調用周
波数発振器の発振出力信号との位相差を検出し、
この位相差の電気信号を出力として発生する電気
手段と、当該出力を受け前記光音響セル内に生じ
た光音響効果を記録する記録手段とを有する光音
響分光分析装置において、光音響セルを音響的に
共鳴構造を有せしめたものを使用し、この共鳴型
光音響セル内の測定試料に生じた光音響効果を音
響電気変換手段で電気信号とし、当該電気信号を
二分し、第１の電気回路において光源駆動電力源
の変調用周波数と当該電気信号との間の位相差を
検出し、両者の位相差を直流電圧として前記変調
用周波数発振器に負帰還し、当該変調用周波数発
振器の発振周波数を上記共鳴型光音響セルの共鳴
周波数に整合せしめ、第２の電気回路において
は、上記音響電気変換器の電気信号をロツク・イ
ン・アンプリフアイヤに入力し、上記変調用周波
数発振器の発振周波数と同期した電気信号を出力
させて記録計に導入し、測定試料に生じた光音響
効果を記録することを特徴とする光音響分光分析
装置。 ２ 特許請求の範囲第１項の光音響分光分析装置
において、光源に発光半導体ダイオード又は半導
体レーザ・ダイオードを使用した光音響分光分析
装置。 ３ 光源および光源を駆動する電力源と、該光源
駆動電力源を所要の周波数で変調する信号を発す
る変調用周波数発振器と、光源からの変調光を受
光し測定試料を収納した光音響セルと、当該測定
試料に生じた光音響効果を検出する音響電気変換
器と、当該音響電気変換器の電気信号を同期検波
して前記変調用周波数発振器の発振出力信号との
位相差を電気信号として出力する電気手段と、該
電気手段からの電気出力により前記測定試料に生
じた光音響効果を記録する装置とから成る光音響
分光分析装置において、光源の発光波長を制御す
る発光波長制御手段と、光源から放射された変調
光の一部を光ビーム・スプリツタを介して分離
し、その分離光路中に、当該変調光を受光し平坦
な分光特性を有する基準試料を収納した光音響セ
ルと、基準試料に生じた光音響効果を検出する音
響電気変換器と、該音響電変換器に生じた電気信
号を同期検波して前記変調用周波数発振器の発振
出力信号との位相差を電気信号として出力する電
気的手段と、該電気的手段の出力の振巾を基準の
振巾と比較し、両者の差に比例した電気信号を出
力する電気手段と、この電気信号を光源駆動電力
源に入れ駆動電力の変調度を調整することを特徴
とする光音響分光分析装置。 ４ 特許請求の範囲第３項の光音響分光分析装置
において、光源に発光半導体ダイオード又は半導
体レーザ・ダイオードを使用した光音響分光分析
装置。 ５ 光源および光源駆動電力源と、該光源駆動電
力源を所要の周波数で変調する信号を発する変調
用周波数発振器と、光源の放射光の発光波長を制
御する発光波長制御手段と、光源から放射された
光を第１および第２の光ビームに分離する光ビー
ム・スプリツト手段と、第１の光ビーム路中に配
置した変調光を受光し平坦な吸収特性を有する基
準の試料を収納した光音響セルと、基準試料に生
じた光音響効果を検出する音響電気変換器と、該
音響電気変換器に生じた電気信号を同期検波して
前記変調用周波数発振器の発振出力信号との位相
差を電気信号として出力せしめる電気手段と、該
電気手段の出力を入力し基準の振巾と両者の振巾
の差に比例した電気出力を出力し光源駆動電力源
の変調度を調節せしめる電気手段と、さらに第２
の光ビーム路中に配置し、測定試料を収納した光
音響セルと、該測定試料に生じた光音響効果を検
出する音響電気変換器と、該音響電気変換器に生
じた電気信号と前記変調用周波数発振器の発振出
力信号との位相差を検出し、位相変化に比例した
電気信号を出力する電気手段と、該電気手段の出
力により測定試料に生じた光音響効果を記録する
装置とから成る光音響分光分析装置において、第
２の光ビーム路中に配置した光音響セルに共鳴型
光音響セルを使用し、音響電気変換器の電気信号
の一部を分離し、当該電気信号を同期検波して前
記変調用周波数発振器の発振出力信号との位相差
を検出し、該位相差に対応した電気信号を変調用
周波数発振器に負帰還せしめ、変調用周波数発振
器に、上記位相差に相当する周波数変化を行わし
め、前記共鳴型光音響セルの共鳴周波数と整合し
た光変調光を放射せしめるようにした光音響分光
分析装置。 ６ 特許請求の範囲第５項の光音響分光分析装置
において、光源に発光半導体ダイオード又は半導
体レーザ・ダイオードを使用した光音響分光分析
装置。[Scope of Claims] 1. A light source, a power source for driving the light source, a modulation frequency oscillator that emits a signal that modulates the power of the power source at a desired frequency, and a frequency oscillator for receiving the modulated light from the light source and transmitting a predetermined measurement sample. a photoacoustic cell that encapsulates a photoacoustic cell, an acoustoelectric transducer that detects the photoacoustic effect generated on a measurement sample within the photoacoustic cell, and an acoustoelectric transducer that synchronously detects the electrical signal generated by the acoustoelectric transducer to detect the modulation frequency. Detects the phase difference with the oscillation output signal of the oscillator,
In a photoacoustic spectrometer having an electric means for generating an electric signal of this phase difference as an output, and a recording means for receiving the output and recording a photoacoustic effect generated in the photoacoustic cell, the photoacoustic cell is The photoacoustic effect produced on the measurement sample in this resonant photoacoustic cell is converted into an electric signal by an acoustoelectric conversion means, the electric signal is divided into two, and the first electric The circuit detects the phase difference between the modulation frequency of the light source driving power source and the electrical signal, and feeds the phase difference between the two as a direct current voltage to the modulation frequency oscillator, thereby adjusting the oscillation frequency of the modulation frequency oscillator. is matched to the resonant frequency of the resonant photoacoustic cell, and in the second electric circuit, the electric signal of the acoustoelectric transducer is inputted to a lock-in amplifier, and the oscillation frequency of the modulation frequency oscillator is adjusted. A photoacoustic spectrometer characterized in that it outputs an electrical signal synchronized with and introduces it into a recorder to record a photoacoustic effect occurring in a measurement sample. 2. A photoacoustic spectrometer according to claim 1, which uses a light-emitting semiconductor diode or a semiconductor laser diode as a light source. 3. a light source, a power source that drives the light source, a modulation frequency oscillator that emits a signal that modulates the light source driving power source at a required frequency, a photoacoustic cell that receives modulated light from the light source and stores a measurement sample; An acoustoelectric transducer that detects the photoacoustic effect produced in the measurement sample, and synchronously detecting the electrical signal of the acoustoelectric transducer and outputting the phase difference between the oscillation output signal of the modulation frequency oscillator as an electrical signal. In a photoacoustic spectrometer comprising an electric means and a device for recording the photoacoustic effect produced on the measurement sample by the electric output from the electric means, an emission wavelength control means for controlling the emission wavelength of the light source; A part of the emitted modulated light is separated through a light beam splitter, and in the separated optical path, there is a photoacoustic cell containing a reference sample that receives the modulated light and has flat spectral characteristics, and a photoacoustic cell that receives the modulated light and has a flat spectral characteristic. an acoustoelectric transducer that detects the generated photoacoustic effect; and an electrical device that synchronously detects the electrical signal generated in the acoustoelectric transducer and outputs the phase difference between the oscillation output signal of the modulation frequency oscillator as an electrical signal. means for comparing the amplitude of the output of the electric means with a reference amplitude and outputting an electric signal proportional to the difference between the two; and modulating the driving power by inputting the electric signal to the light source driving power source. A photoacoustic spectrometer characterized by adjusting the intensity. 4. The photoacoustic spectrometer according to claim 3, which uses a light emitting semiconductor diode or a semiconductor laser diode as a light source. 5 a light source and a light source driving power source; a modulation frequency oscillator that emits a signal that modulates the light source driving power source at a required frequency; a light emission wavelength control means that controls the light emission wavelength of the light emitted from the light source; a photoacoustic device which receives the modulated light and houses a reference sample having flat absorption characteristics, which is disposed in the first light beam path; A cell, an acoustoelectric transducer that detects the photoacoustic effect produced in the reference sample, and synchronously detecting the electrical signal generated in the acoustoelectric transducer to electrically detect the phase difference between the oscillation output signal of the modulation frequency oscillator. an electric means for outputting the signal as a signal; an electric means for inputting the output of the electric means and outputting an electric output proportional to a reference amplitude and the difference between the two amplitudes to adjust the degree of modulation of the light source driving power source; Second
a photoacoustic cell disposed in the optical beam path of and containing a measurement sample; an acoustoelectric transducer for detecting the photoacoustic effect generated in the measurement sample; and an electric signal generated in the acoustoelectric transducer and the modulation. It consists of an electric means that detects the phase difference with the oscillation output signal of the frequency oscillator and outputs an electric signal proportional to the phase change, and a device that records the photoacoustic effect produced on the measurement sample by the output of the electric means. In a photoacoustic spectrometer, a resonant photoacoustic cell is used as the photoacoustic cell placed in the second optical beam path, a part of the electrical signal of the acoustoelectric transducer is separated, and the electrical signal is synchronously detected. to detect the phase difference with the oscillation output signal of the modulation frequency oscillator, and negative feedback of the electrical signal corresponding to the phase difference to the modulation frequency oscillator causes the modulation frequency oscillator to output a frequency corresponding to the phase difference. 1. A photoacoustic spectroscopy analyzer configured to change the wavelength of the resonant photoacoustic cell and emit modulated light that matches the resonant frequency of the resonant photoacoustic cell. 6. The photoacoustic spectrometer according to claim 5, which uses a light emitting semiconductor diode or a semiconductor laser diode as a light source.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8398779A JPS5610230A (en) | 1979-07-04 | 1979-07-04 | Optical sound spectroscopic analyzer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8398779A JPS5610230A (en) | 1979-07-04 | 1979-07-04 | Optical sound spectroscopic analyzer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5610230A JPS5610230A (en) | 1981-02-02 |
| JPS6321130B2 true JPS6321130B2 (en) | 1988-05-02 |
Family
ID=13817881
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8398779A Granted JPS5610230A (en) | 1979-07-04 | 1979-07-04 | Optical sound spectroscopic analyzer |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5610230A (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5071388A (en) * | 1973-06-15 | 1975-06-13 | ||
| JPS5436778A (en) * | 1977-08-26 | 1979-03-17 | Horiba Ltd | Photosound effect type analyzer |
| JPS5459188A (en) * | 1977-10-19 | 1979-05-12 | Nec Corp | Infrared spectrophotometer apparatus of gas chromatography |
-
1979
- 1979-07-04 JP JP8398779A patent/JPS5610230A/en active Granted
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5071388A (en) * | 1973-06-15 | 1975-06-13 | ||
| JPS5436778A (en) * | 1977-08-26 | 1979-03-17 | Horiba Ltd | Photosound effect type analyzer |
| JPS5459188A (en) * | 1977-10-19 | 1979-05-12 | Nec Corp | Infrared spectrophotometer apparatus of gas chromatography |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5610230A (en) | 1981-02-02 |
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