JPH034143A - Variation noise removing system for laser in particulate detector - Google Patents
Variation noise removing system for laser in particulate detectorInfo
- Publication number
- JPH034143A JPH034143A JP1139995A JP13999589A JPH034143A JP H034143 A JPH034143 A JP H034143A JP 1139995 A JP1139995 A JP 1139995A JP 13999589 A JP13999589 A JP 13999589A JP H034143 A JPH034143 A JP H034143A
- Authority
- JP
- Japan
- Prior art keywords
- scattered light
- laser
- laser beam
- external mirror
- receiving system
- 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.)
- Granted
Links
- 239000002245 particle Substances 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 7
- 230000010355 oscillation Effects 0.000 claims description 5
- 238000001514 detection method Methods 0.000 abstract description 14
- 239000010419 fine particle Substances 0.000 description 8
- 239000007789 gas Substances 0.000 description 6
- 230000008030 elimination Effects 0.000 description 3
- 238000003379 elimination reaction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
Landscapes
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
この発明は、微粒ｒ検出器におけるレーザの変動ノイズ
排除方式に関し、詳しくは外部ミラー型レーザ発娠器に
よる微粒子検出器において、サンプルエアにより発生す
るレーザビーム強度の変動ノイズを排除し、微粒子散乱
光のみを検出する力式に関するものである。[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for eliminating laser fluctuation noise in a particle r detector, and more specifically, in a particle detector using an external mirror type laser generator, noise generated by sample air is eliminated. This relates to a force formula that eliminates fluctuation noise in the laser beam intensity and detects only light scattered by particles.
［従来の技術］
半導体ＩＣの製造上場においてはＩＣのパターンサイズ
の微細化に伴って、クリーンルーｌ、の顯埃微粒子に対
する管理はますます厳格となり、これに対して微粒？−
Ｍ出器の検出性能をさらに向１・。[Conventional technology] In the manufacturing and listing of semiconductor ICs, with the miniaturization of IC pattern sizes, control over dust and fine particles under clean rules has become increasingly strict. −
Further improved the detection performance of the M detector.
することが７認とされている。It is said that there are 7 approvals to do so.
微粒′ｒ−検出器はレーザビームに塵埃などの微粒ｒを
含むサンプルエアを直交させ、微粒−ｒの散乱光を検出
するものであるが、散乱光の強度はレーザビームのそれ
に比例するので、直径の小さい微粒子を検出するために
はできる限り強度の大きいレーザビームを使用すること
が望ましい。レーザ光源としは通常、ガスレーザ管が使
用されており、その構成方法には内部ミラー型と外部ミ
ラー型とがある。前者においては発振したレーザビーム
強度の数％程度を利用するに対して、後者は発振強度そ
のものを利用して強度を飛躍的に大きくできるので有利
である。The particulate 'r-detector detects the scattered light of the particulates by making the sample air containing particulates such as dust orthogonal to the laser beam, but since the intensity of the scattered light is proportional to that of the laser beam, In order to detect fine particles with a small diameter, it is desirable to use a laser beam with as high an intensity as possible. A gas laser tube is usually used as a laser light source, and there are two types of construction methods: an internal mirror type and an external mirror type. In the former case, only a few percent of the oscillated laser beam intensity is used, whereas in the latter case, the oscillation intensity itself can be used to dramatically increase the intensity, which is advantageous.
第２図（ａ）、（ｂ）は外部ミラー型レーザ発振器によ
る微粒子・検出器の要部を示すもので、図（ａ）におい
て、レーザ発振′Ｊ！Ａｌはヘリウム・ネオンなどのレ
ーザガスを充填したガスレーザ管１ａの一端に内部ミラ
ー１ｂを固定し、他端にブリュースター窓ＩＣを取り付
けて、これを検出セル２の内部に挿入して固定する。検
出セル２にはブリュースター窓ＩＣに対応した位置に外
部ミラー１ｄを設け、これと内部ミラー１ｂとの間にレ
ーザビームＬが発振する。これに対して、中心ノズル３
ａよリサンプルエアＡを噴射して直交させる。なお、サ
ンプルエアＡを層流とするために外層ノズル３ｂにより
クリーンなシースエアＢを噴射することも行われ、シー
スエアＢはサンプルエアＡとともに排出ノズル４より外
部に排出される。図（ｂ）は微粒子の散乱光に対する散
乱光受光系５を示すもので、受光し／ズ５ａ、スリット
板５ｂおよび光電変換器５ｃにより構成され、スリット
板５ｂのスリットＳ′により、サンプルエアＡとレーザ
ビーｌ、Ｌの直交箇所の視野を限定して検出領域Ｓとし
、Ｓ以外の箇所からの迷光を排除してＳ／Ｎ比が向１−
されるものである。FIGS. 2(a) and 2(b) show the main part of a particle detector using an external mirror type laser oscillator. In FIG. 2(a), the laser oscillation 'J! An internal mirror 1b is fixed to one end of a gas laser tube 1a filled with a laser gas such as helium or neon, and a Brewster window IC is attached to the other end, which is inserted into the detection cell 2 and fixed. The detection cell 2 is provided with an external mirror 1d at a position corresponding to the Brewster window IC, and a laser beam L is oscillated between this and the internal mirror 1b. On the other hand, the center nozzle 3
Inject resample air A to cross a. Incidentally, in order to make the sample air A into a laminar flow, clean sheath air B is also injected by the outer layer nozzle 3b, and the sheath air B is discharged to the outside from the discharge nozzle 4 together with the sample air A. Figure (b) shows a scattered light receiving system 5 for the scattered light of particles, which is composed of a light receiving lens 5a, a slit plate 5b, and a photoelectric converter 5c. The field of view at the orthogonal location of laser beams L and L is limited to the detection area S, and stray light from locations other than S is eliminated to increase the S/N ratio to 1-1.
It is something that will be done.
［解決しようとする課！Ｉｆｆ］
−・般に微粒子＠出器の検出性能を向上するためには、
］−記の外部ミラー型反射器を使用してレーザビームの
強度を増強するほか、受光系の集光範囲または感度を増
加する方法などが行われるが、サンプルエアの空気分子
は密度分布がランダムであり、Ｅ記の外部ミラー型のレ
ーザ発振器においては、空気分子がレーザビームをラン
ダムに遮断して乱反射するために発振強度が変動し、こ
の変動がノイズとなって散乱光受光系の受光信号のＳ／
Ｎ比が低ドする問題がある。[Try to solve the problem! In general, in order to improve the detection performance of particulate @ extractors,
] - In addition to increasing the intensity of the laser beam using an external mirror reflector, methods such as increasing the focusing range or sensitivity of the light receiving system are used, but the density distribution of air molecules in the sample air is random. In the external mirror type laser oscillator described in E, the oscillation intensity fluctuates because the air molecules randomly block the laser beam and diffusely reflect it, and this fluctuation becomes noise and causes the light reception signal of the scattered light reception system to vary. S/
There is a problem that the N ratio is low.
この発明は以りの問題を解決するためになされたもので
、外部ミラー型のレーザ発振器により構成された微粒子
検出ムにおいて、サンプルエアによるレーザビームの変
動ノイズを排除し、微粒子の散乱光のみを検出する方式
を提供することを［１的さするものである。This invention was made in order to solve the above problems, and in a particulate detection system configured with an external mirror type laser oscillator, it eliminates the fluctuation noise of the laser beam caused by the sample air and detects only the scattered light of the particulates. The first purpose is to provide a detection method.
［課題を解決するためのｆ段］
この発明は、一端に内部ミラーを有するガスレーザ管の
外方に外部ミラーを設けて外部ミラー型レーザ発振器を
構成し、この発振器のレーザビームに対してサンプルエ
アを直交させ、これに含まれている微粒子−による散乱
光を散乱光受光系により受光する微粒子検出器における
レーザの変動ノイズの排除方式であって、サンプルエア
によす発振強ばか変動して変動ノイズを発生したレーザ
ビームを、外部ミラーより漏洩させる。この＠残光に対
する漏洩光受光系を設け、に記の散乱光受光系の出力信
号より漏洩光受光系の出力する変動ノイズ信号を減算し
て微粒子の散乱光のみを検出するものである。[F stage for solving the problem] This invention configures an external mirror type laser oscillator by providing an external mirror on the outside of a gas laser tube having an internal mirror at one end. This is a method for eliminating laser fluctuation noise in a particle detector in which the scattered light from the fine particles contained therein is received by the scattered light receiving system, and the oscillation intensity due to the sample air fluctuates. The laser beam that generates noise is leaked from an external mirror. A leakage light receiving system is provided for this afterglow, and a fluctuating noise signal outputted from the leaking light receiving system is subtracted from the output signal of the scattered light receiving system described above to detect only the scattered light of the particles.
Ｃ作用コ
前記したように外部ミラー型レーザ発振器においては、
サンプルエアの空気分子密度のランダム性によりレーザ
ビームに変動ノイズが発生し、これが散乱光受光系より
微粒子散乱光の信号とともに出力される。外部ミラーに
は反射率が９９．９８％程度のものを用い、残りの０．
０２％が透過して背面より漏洩し、Ａｉ洩光受光系より
変動ノイズ信号が出力される。両者の変動ノイズ信号は
相似形、かつ同相であるので、各受光系の出力信号の差
をとることにより変動ノイズは消去されて微粒ｒ−の散
乱光成分のみが検出されるものである。C Effect: As mentioned above, in the external mirror type laser oscillator,
Fluctuation noise is generated in the laser beam due to the randomness of the air molecule density in the sample air, and this is output from the scattered light receiving system together with the particle scattered light signal. For the external mirror, use one with a reflectance of about 99.98%, and the remaining 0.98%.
02% is transmitted and leaks from the back surface, and a fluctuating noise signal is output from the Ai leakage light receiving system. Since both fluctuating noise signals are similar and in phase, by taking the difference between the output signals of each light receiving system, the fluctuating noise is eliminated and only the scattered light component of the fine particles r- is detected.
［実施例］
第１図（ａ）、（ｂ）はこの発明によるレーザの変動ノ
イズ排除方式の実施例の要部に対するブロック構成と各
出力信号の波形を示すもので、図（ａ）にオイテ、前記
の第２図（ａ）と同様に、ガスレーザ管１ａ＋内部ミラ
ー１ｂ、ブリュースターＸｌｃおよび外部ミラー１ｄに
より外部ミラー型レーザ発娠器ｌが構成され、外部ミラ
ー１ｄと内部ミラー１ｂとの間にレーザが発振する。レ
ーザビームＬに直交してサンプルエアＡとシースエアＢ
が噴射され、微粒子により散乱光が散乱する。散乱光受
光系５もまた第２図（ａ）、（ｂ）で説明したと同様に
構成され、検出領域Ｓにおける微粒子の散乱光、サンプ
ルエアの空気分子によるレーり散乱光ｎ （レーザビー
ムの強度変動による変動ノイズ）とがともに散乱光受光
系５に受光されて信号ｅｓが出力される。これに対して
、外部ミラー１ｄの背面に漏洩光受光″Ｉ！Ａ６を設け
てレーザビームＬの漏洩光Ｌ′に対する変動ノイズ信号
ｎが出力される。増幅器７ａ、７ｂにより、各変動ノイ
ズ信号ｎを同一のレベルに調整してコンパレータ８に人
力し、図（ｂ）に示すように両者の波形の差分信号（ｅ
ｓ −ｎ）をとって微粒子の散乱光に対する検出信号ｅ
ｐがえられる。この場合、信号ｅｓにおける微粒ｒ・の
検出波形１）ｌ ｅ ｐ２ 、ｐ３などは変動ノイズｎ
に爪管してピーク値が」ニドし、なかにはｐ２のように
波形がマスクされるものもあるが、差分信号ｅｐでは変
動ノイズｎが排除されてＳ／Ｎ比が向１−シ、いずれの
ピーク、値をも正しく検出することができる。なお、信
号ｅｐは信号処理部９に人力して個々の微粒子の粒径が
検出される。[Example] Figures 1(a) and 1(b) show the block configuration and waveforms of each output signal for the main parts of an embodiment of the laser fluctuation noise elimination method according to the present invention. , as in FIG. 2(a) above, an external mirror type laser generator 1 is constituted by the gas laser tube 1a + internal mirror 1b, Brewster Xlc and external mirror 1d, and between the external mirror 1d and internal mirror 1b. The laser oscillates. Sample air A and sheath air B are perpendicular to the laser beam L.
is injected, and the scattered light is scattered by the fine particles. The scattered light receiving system 5 is also configured in the same manner as explained in FIGS. 2(a) and 2(b), and it detects the scattered light of particles in the detection area S, the laser scattered light n (of the laser beam) caused by the air molecules of the sample air. (fluctuation noise due to intensity fluctuations) are both received by the scattered light receiving system 5, and a signal es is output. On the other hand, a leakage light receiver "I!A6" is provided on the back surface of the external mirror 1d, and a fluctuation noise signal n corresponding to the leakage light L' of the laser beam L is outputted.Amplifiers 7a and 7b generate each fluctuation noise signal n are adjusted to the same level and input to the comparator 8, and the difference signal (e
s − n) to obtain the detection signal e for the scattered light of the particles.
You can get p. In this case, the detection waveform 1) of the fine particles r in the signal es, e p2, p3, etc., is the fluctuation noise n
However, in the difference signal ep, the fluctuating noise n is eliminated, and the S/N ratio is 1 to 1. Peaks and values can also be detected correctly. Note that the signal ep is manually input to the signal processing section 9 to detect the particle size of each fine particle.
［発明の効果］
以りの説明より明らかなように、この発明にょるレーザ
の変動ノイズ排除方式によれば、散乱光受光系の出力信
号に含まれているレーザビームの変動ノイズは、−残光
受光系の出方信号を差し引くことにより排除されて微粒
子の散乱光のみが検出されるもので、外部ミラー型のレ
ーザ発振器により構成された微粒子・検出器の検出性能
を向上する効果には大きいものがある。[Effects of the Invention] As is clear from the explanation below, according to the laser fluctuation noise elimination method according to the present invention, the laser beam fluctuation noise contained in the output signal of the scattered light receiving system is reduced to -residual noise. By subtracting the output signal of the light receiving system, only the scattered light of the particles is detected, and it is highly effective in improving the detection performance of particle detectors configured with external mirror type laser oscillators. There is something.
第１図（ａ）および（ｂ）は、この発明による微粒子検
出器におけるレーザの変動ノイズ排除方式の実施例のブ
ロック構成図と各出力信号の波形図、第２図（ａ）およ
び（ｂ）は、外部ミラー型レーザ発振器により構成され
た微粒ｒ−検出器の要部の断面図と散乱光受光系の斜視
図である。
ｌ・・・外部ミラーをレーザ発振器、
１ａ・・・ガスレーザ管、 ｌｂ・・・内部ミラーＩ
Ｃ・・・ブリュースター窓、ｌｄ・・・外部ミラー２・
・・検出セル、 ３・・・噴射ノズル、３ａ・
・・中心ノズル、
４・・・排出ノズル、
５ａ・・・受光レンズ、
５ｃ・・・充電変換器、
７ａ、７ｂ−・・増幅器、
９・・・信号処理部。
３ｂ・・・外層ノズル、
５・・・散乱光受光系、
５ｂ・・・スリット板、
８・・・漏洩光受光器、
８・・・コンパレータ、
第２図
（ａ）FIGS. 1(a) and (b) are block diagrams and waveform diagrams of each output signal of an embodiment of the laser fluctuation noise elimination method in a particle detector according to the present invention, and FIGS. 2(a) and (b) are 2 is a cross-sectional view of a main part of a fine particle r-detector configured with an external mirror type laser oscillator, and a perspective view of a scattered light receiving system. l...External mirror as laser oscillator, 1a...Gas laser tube, lb...Internal mirror I
C...Brewster window, ld...exterior mirror 2.
...Detection cell, 3...Injection nozzle, 3a.
... Center nozzle, 4... Discharge nozzle, 5a... Light receiving lens, 5c... Charging converter, 7a, 7b-... Amplifier, 9... Signal processing section. 3b... Outer layer nozzle, 5... Scattered light receiving system, 5b... Slit plate, 8... Leakage light receiver, 8... Comparator, Fig. 2(a)
Claims (1)
ラーを設けて外部ミラー型レーザ発振器を構成し、該発
振器のレーザビームに対してサンプルエアを直交させ、
該サンプルエアに含まれる微粒子の散乱光を散乱光受光
系により受光する微粒子検出器において、上記サンプル
エアにより発振強度が変動して変動ノイズを発生した上
記レーザビームを上記外部ミラーの背面より漏洩させ、
該漏洩光に対する漏洩光受光系を設け、上記散乱光受光
系の出力信号より、該漏洩光受光系の出力する変動ノイ
ズ信号を減算して上記微粒子の散乱光のみを検出するこ
とを特徴とする、微粒子検出器におけるレーザの変動ノ
イズ排除方式。An external mirror is provided outside a gas laser tube having an internal mirror at one end to constitute an external mirror type laser oscillator, and the sample air is orthogonal to the laser beam of the oscillator,
In a particulate detector that receives scattered light from particulates contained in the sample air using a scattered light receiving system, the laser beam whose oscillation intensity fluctuates due to the sample air and generates fluctuating noise leaks from the back surface of the external mirror. ,
A leakage light receiving system for the leaked light is provided, and a fluctuating noise signal output from the leaked light receiving system is subtracted from an output signal of the scattered light receiving system to detect only the scattered light of the particles. , Laser fluctuation noise rejection method in particle detectors.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1139995A JP2696561B2 (en) | 1989-06-01 | 1989-06-01 | Elimination method of fluctuation noise of laser in particle detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1139995A JP2696561B2 (en) | 1989-06-01 | 1989-06-01 | Elimination method of fluctuation noise of laser in particle detector |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH034143A true JPH034143A (en) | 1991-01-10 |
| JP2696561B2 JP2696561B2 (en) | 1998-01-14 |
Family
ID=15258483
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1139995A Expired - Lifetime JP2696561B2 (en) | 1989-06-01 | 1989-06-01 | Elimination method of fluctuation noise of laser in particle detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2696561B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006189337A (en) * | 2005-01-06 | 2006-07-20 | Fuji Electric Systems Co Ltd | Fine particle measuring instrument |
| GB2531788A (en) * | 2014-10-31 | 2016-05-04 | Pcme Ltd | Methods and apparatus relating to particulate monitors |
-
1989
- 1989-06-01 JP JP1139995A patent/JP2696561B2/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006189337A (en) * | 2005-01-06 | 2006-07-20 | Fuji Electric Systems Co Ltd | Fine particle measuring instrument |
| GB2531788A (en) * | 2014-10-31 | 2016-05-04 | Pcme Ltd | Methods and apparatus relating to particulate monitors |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2696561B2 (en) | 1998-01-14 |
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