Optics: measuring and testing – By particle light scattering – With photocell detection
Reexamination Certificate
1998-01-29
2002-02-12
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
By particle light scattering
With photocell detection
C356S338000
Reexamination Certificate
active
06346983
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to air, gas and liquid quality and, more particularly, to devices, apparatus and instruments for airborne (gas) particle and/or liquid contamination quantity counting and particle size measuring by light (laser) beam.
BACKGROUND OF THE INVENTION
The methods and devices for determining quantity and size of the particles and/or liquid (water) contaminations are now well known, and it is also well known that powerful light or laser and detecting system can be, and have been used to achieve particle size and particle quantity measurements. Such devices, mostly using or computers, are well known and described, for example, in the articles: R. G. Knollenberg, B. Schuster—“Detection and Sizing of Small Particles in Open Cavity Gas Laser,” Applied Optics, Vo. 11, No. 7, November 1972, pp. 1515-1520; R. G. Knollenberg—“An Active Scattering Aerosol Spectrometer,” Atmospheric Technology, No. 2, June 1973, pp. 80-81; Schehl, Ergun, Headrick—“Size Spectrometry of Aerosols Using Light Scattering from the Cavity of a Gas Laser,” Review of Scientific Instruments, Vol. 44, No. 9, September 1973; R. G. Knollenberg—“Active Scattering Aerosol Spectrometry,” National Bureau of Standards Special Publication, No. 412, October 1974, pp. 57-64; R. G. Knollenberg, R. E. Luehr—“Open Cavity Laser Active Scattering Particle Spectrometry from 0.05 to 5.0 Microns,” Fine Particles, Aerosol Generation Measurement, Sampling and Analysis, Academic Press, May 1975, pp. 669-696; R. G. Knollenberg—“Three New Instruments for Cloud Physics Measurements: The 2-D Spectrometer, the Forward Scattering Spectrometer Probe, and the Active Scattering Aerosol Spectrometer,” American Meteorological Society, International Conference on Cloud Physics, July 1976, pp. 554-561; R. G. Knollenberg—“The Use of Low Power Laser in Particle Size Spectrometry”, Proceeding of the Society of Photo-Optical Instrumentation Engineers, Practical Applications of Low Power Lasers, Vo. 92, August 1976, pp. 137-152; Elterman—“Brewster Angle Light Trap,” Applied Optics, Vol. 16, No. 9, September 1977; Marple—“The Aerodynamics Size Calibration of Optical Particle Counters by Inertial Impactors,” Aerosol Measurement, 1979; Diehl, Smith, Sydor—“Analysis by Suspended Solids by Single-Particle Scattering,” Applied Optics, Vol. 18, No. 10, May 1979; K. Suda—Review of Scientific Instruments, Vol. 51, No. 8, August 1980, pp. 1049-1058; R. G. Knollenberg—“The Measurement of Particle Sizes Below 0.1 Micrometers”, Journal of Environment Science, January-February, 1985, pp. 64-67; Peters—“20 Good Reasons to Use In Situ Particle Monitors”, Semiconductor International, Nov. 1992, pp. 52-57 and Busselman et al.—“In Situ Particle Monitoring in a Single Wafer Poly Silicon and Silicon Nitride Etch System”, IEEE/SEMI Int'l Semiconductor Manufacturing Science Symposium, 1993, pp. 20-26.
The reference in these articles is made to the devices and methods of particle measurement, utilizing an open cavity laser for particle detection.
The known devices, having the particle detecting means are based on the scattered light collection, as it is mentioned, for example, in U.S. Pat. No. 4,140,395, U.S. Pat. No. 4,798,465, U.S. Pat. No. 5,467,189 and in 5,515,164 of the prior art.
For example, in U.S. Pat. No. 4,140,395 and in U.S. Pat. No. 4,798,465 of the prior art are used the imaging systems, which are based on lenses.
Yet in other prior art (for example, such as U.S. Pat. No. 5,467,189 and U.S. Pat. No. 5,515,164) we can find the devices (sensors) with ellipsoidal mirrors instead of the lens systems or non-divergent quadric mirrors.
All these devices, mentioned in the prior art above, use light scattering focalizing methods. Such methods are based on the collection of the scattered light. A light scattering occurs at the first focal point (focus) by intersecting. Considering stochastic processes of the light scattering, the devices, mentioned in the above prior art, use mirrors or optics. This is necessary for scattered light, collecting and focalizing at the second focal point (focus), where a light detector is placed and intended for scattered light detection.
Further the devices, based on scattered light collection and some other detection methods (for example, by light splitting), use a different variations of the comparison method for the particle size measuring. Such method can be illustrated (see FIG.
1
), for example, by U.S. Pat. No. 4,798,465. On
FIG. 1
is shown the particle size detection device, using one of the particle measuring comparison method variations. The signal from detectors
1
via the amplifiers
61
follow to the comparators
62
, which is connected to the reference voltage means
63
. The amplified detected signals are compared with the predetermined reference voltages for the particle size qualifying.
Such methods cannot provide light the sufficiently light the sensitivity related to the increasing requirements to the particle counting and measuring devices, because of the analog (amplitude) method of comparison.
Another and also important deficiency of all known particle analyzing devices is the use of the wire leads (cable) for the particle detecting means connection to the data processing means.
The devices, using the wire (cable) connection of the particle detecting, means to the data processing and control system, are presented by two styles of their configuration: a portable configuration of the particle analyzing device, which is an entire unit comprising particle detecting means (sensor) connected by short wires (short cable) to the microprocessor means, or a remote sensor configuration of the particle analyzing device, wherein, for example, the sensor and the data processing means are represented by two separated and remote of each other units connected by long wires (long cable).
On
FIG. 2
is shown, for example, a device (see U.S. Pat. No. 5,524,129) with the wire (cable) connection
20
of the sensor
22
with the microprocessor (CPU)
24
(
12
).
It is known, that all wire (cable) connections in electronic apparatus are a source of the electromagnetic noise, which can create a distortion of the signals. Also the portable devices require local operation with them and exactly in the place of the airborne particle or liquid (water) contaminations assaying. The devices with long cable connection between the remote sensor and the data processing means have a limited mobility, because of cable.
Other known devices by U.S. Pat. Nos. 4,160,246 and 5,751,424 intended for the smoke detection and liquid mixture, gas or solid medium analysis respectively. The smoke detector by U.S. Pat. No. 4,160,246 does not provide the counting and measuring of the particles in the specimen and uses the analog processing of the signals. The probe by U.S. Pat. No. 5,751,424 does not provide the analysis of the airborne particle. Also these devices use one-way wireless communication for the data transmission only and do not provide the wireless transmission of the control commands/signals (automatic modes of turn-on/turn-off, switching of the particle size counting scale, etc.), requiring the handle control of the remote unit.
For example, it is known, that integrated circuits (chips) and semiconductors have been produced in “clean rooms”. The air in such “clean rooms” should be very well cleaned. The continuing tendencies of improvement in circuit integration and degree of microminiaturization require corresponding improvements of the environment in “clean rooms” and efficiency and sensitivity of the measuring devices. And now, as it is known, the sensitivity of the counting and measuring devices should be at least as small as 0.1 &mgr;m (Micron). Such rate requires minimum distortions in the data processing signals. Also the measurements should be done in the different places of the semiconductor production areas of “clean rooms” and sometimes in the areas, which could be difficult to approach. The same is regarding the pharmaceutical and biological industries, where is required the well condition of the
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