Pathogen and particle detector system and method

• US 8,218,144 B2
• Filed: 07/11/2008
• Issued: 07/10/2012
• Est. Priority Date: 07/30/2004
• Status: Expired due to Fees

• Current Assignee: BioVigilant Systems Incorporated (Azbil BioVigilant Incorporated)
• Original Assignee: Azbil BioVigilant Incorporated
• Inventors: Jiang, Jian-Ping, Babico, John, Morrell, Michael
• Primary Examiner(s): PHAM, HOA Q
• Application Number:
  US12/172,190
• Publication Number:
  US 20120147370A1
• Time in Patent Office: 1,460 Days
• Field of Search: 356335-343, 356244-246, 356/73, 340/507, 340/627, 340/628, 340/630
• US Class Current: 356/336
• CPC Class Codes: G01N 15/0205 by optical means
• CPC Class Codes: G01N 2015/019 Biological contaminants; Fouling
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/53 within a flowing fluid, e.g. smoke
• CPC Class Codes: G01N 21/6486 Measuring fluorescence of biological material, e.g. DNA, RNA, cells G01N21/6428 takes precedence
• CPC Class Codes: H03K 5/04 by increasing duration; by decreasing duration

Abstract

A particle detector has a sample area of cross section no in excess of about 2 mm for containing environmental fluid, a light source on one side of the sample area for directing a collimated or nearly collimated beam of light through the sample air or water so that part of the light beam will be scattered by any particles present in the air or water while the remainder remains unscattered, and a beam diverting device on the opposite side of the sample area for diverting or blocking at least the unscattered portion of the beam of light and directing at least part of the scattered light onto a detector. The detector produces output pulses in which each pulse has a height proportional to particle size and a pulse height discriminator obtains the size distribution of airborne particles detected in the air or water sample at a given time from the detector output. The detector may also include a device for discriminating between biological agents and inorganic particles.

Claims

1. An airborne particle detector system, comprising:

an outer housing having an air sample cell area of cross-section not in excess of about 2 mm;

a light source on one side of the air sample cell area for sending a focused beam of light through the sample air, whereby portions of the beam of light are scattered at various angles by particles of various sizes present in the sample area, and an unscattered portion of the beam of light remains unscattered;

a beam blocking device on the opposite side of the air sample cell area for blocking at least the portion of the unscattered portion of the beam of light;

a first detector with control circuitry positioned in the light path after the beam blocking device for detecting a portion of the scattered light, and producing an output including information on the number of particles in the light path within a predetermined size range, and

further comprising the following features;

(a) an alarm unit for providing a warning signal if the number of particles within a predetermined size range exceeds a predetermined normal level within that size range,

wherein the alarm unit produces an alarm signal if the number of particles detected within a size range of approximately 1 to 7 μ

m exceeds a predetermined level;

(b) a processing unit connected to the output of the pulse height discriminator for processing the particle size distribution at a given time, based on the height of each pulse, producing a histogram of the airborne particle size distribution, and displaying the histogram on an output device;

(c) a reflector positioned in front of the beam blocking device in the path of the unscattered portion of the light beam for reflecting at least part of the unscattered portion in a second light path, and a second photodetector positioned to detect light reflected from the reflector;

(d) a power monitor connected to the output of the second photodetector for detecting decrease in light source output power, and an alarm device connected to the power monitor for producing an alarm signal if the light source power falls below a predetermined level;

(e) a differential amplifier connected to the outputs of the two photodetectors for dividing the output of the first photodetector by the output of the second photodetector, the differential amplifier having an output connected to the pulse height discriminator;

(f) a transparent partition slide positioned between the sample area and the beam blocking device;

(g) wherein the light source comprises either a laser or an LED;

(h) wherein, if the light source is an LED, the light source includes optical lens for shaping light from said LED into near collimated light; and

(i) wherein said light source includes optical lens for shaping light or removing noise from said light beam.

2. A detector apparatus for detecting airborne particles in a size range of approximately 1 to 7 μ

m in environmental air, comprising;

a light source for directing a focused beam of light through a sample of environmental air in a sample cell of cross-section not in excess of about 2 mm, whereby a first portion of said light beam remains unscattered and a second portion of said light beam is scattered at various angles by particles of various sizes present in the air sample, the scattering angle and scattering cross-section being dependent on the particle size;

a beam separating device for separating a predetermined part of the light beam corresponding to light scattered by particles within a predetermined size range from the remainder of the light beam and directing the separated part of the light beam along a light path;

a first detector positioned in the light path for detecting said separated part of the light beam and producing a corresponding output signal including information on the number of particles in the light path within a predetermined size range, and further the following features;

(a) a control unit connected to the detector output for generating an alarm signal if the detected number of particles within a range of approximately 1 to 7 μ

m in size exceeds a predetermined value;

(b) a pulse height discriminator connected to the output of the detector for separating and counting output pulses from the detector based on pulse height, a processing unit connected to the output of the pulse discriminator for processing the particle size distribution at a give time, based on the height of each pulse, and producing an output comprising a histogram of the airborne particle size distribution, and a display device connected to the output of the processing unit for displaying the particle size distribution histogram;

(c) a reflector positioned in front on the beam separating device in the path of the unscattered portion of the light beam for reflecting at least part of the unscattered portion in a second light path, and a second photodetector positioned to detect light reflected from the reflector;

(d) a power monitor connected to the output of the second photodetector for detecting decrease in light source output power, and an alarm device connected to the power monitor for producing an alarm signal if the light source power falls below a predetermined level;

(e) a differential amplifier connected to the outputs of the two photodetectors for dividing the output of the first photodetector by the output of the second photodetector, the output of the differential amplifier having an output connected to the pulse height discriminator;

(f) a reflector positioned in front of the beam separating device in the path of a part of the scattered portion of the light beam for reflecting at least part of the scattered portion in a second light path, and a second photodetector positioned to detect light reflected from the reflector;

(g) a transparent partition slide positioned between the sample area and the beam separating device;

(h) wherein, the light source comprises either an LED or a laser, and

(i) wherein, if the light source comprises an LED, an optical lens for shaping light from said LED into near collimated light.

3. A method of detecting airborne particles, comprising the steps of:

directing a light beam through a sample of environmental air in a sample cell of cross-section not in excess of about 2 mm such that a first portion of the light beam is scattered by particles present in the sample and a second portion remains unscattered;

receiving both portions of the light beam which have passed through the air sample and directing the light beam portions onto a beam blocking device;

blocking at least the second portion of the light beam at the beam blocking device and directing at least part of the first portion of the light beam onto a first detector;

measuring the pulse height of electrical pulses output from the first detector;

counting the number of pulses of each pulse height in a predetermined time interval and converting the pulse heights to particle sizes, and further comprising the following features or steps;

(a) producing an alarm signal if the number of pulses detected within a range of 1 to 7 μ

m is exceeded;

(b) converting the data of number of pulses for each particle size into a histogram of the detected particle size distribution, displaying the histogram on an output display device, and repeating the conversion and displaying steps at predetermined intervals for new air samples;

(c) comparing the histogram to known bio-agent particle size distributions, and activating an alarm if the detected distribution matches any known bio-agent particle size distribution;

(d) blowing air through the sample area continuously to monitor changing conditions in a surrounding area;

(e) reflecting at least part of the second portion of the light beam onto a second detector, connecting the output of the second detector to a power monitor for detecting decrease in light source output power, and producing an alarm signal if the light source power falls below a predetermined level;

(f) placing a transparent partition slide between the sample area and beam blocking device to prevent dust from entering optical components.