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
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
  • G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/02—Investigating particle size or size distribution
  • G01N15/0205—Investigating particle size or size distribution by optical means

Definitions

• the present invention is directed to a system and method for detecting airborne allergen particles and for providing an alarm or operating a filtering system if the detected amount of allergen particles is above a predetermined level .
• an allergen particle detection system which comprises a light source for directing a light beam through a sample of environmental air, a beam blocking assembly positioned in the light path on the opposite side of the air sample for blocking transmission of all light except the portion of light scattered in a predetermined angular range corresponding to a predetermined allergen particle size range of 0.5 micron to 500 microns, a focusing lens positioned in front of the light source for focusing the light beam onto the beam blocking device, a detector positioned to receive light transmitted through the beam blocking assembly, and a control circuit connected to the detector for generating an alarm output signal if the detector output is above a predetermined level.
• the alarm output signal may be used to activate an audible or visual alarm device, or to turn on a filtration and ventilation system including HEPA or allergen particle filters.
• the filtration system may be turned off as soon as the detected allergen particles have returned to a safe level.
• the apparatus may be relatively small, and may be conveniently designed for wall mounting.
• the beam blocking assembly preferably comprises a disc of light blocking material centered on the optical axis and of predetermined diameter to block all unscattered light and light scattered at angles below a predetermined minimum angle which is scattered by particles larger than the largest allergen particle size, and an annular ring of light blocking material having an inner diameter corresponding to the predetermined maximum scattering angle, such that light scattered at angles larger than the maximum scattering angle is blocked.
• the focusing lens is arranged to focus the light beam onto the central, beam blocking disc.
• the light source is a light emitting diode (LED) .
• LED light emitting diode
• the focusing lens and beam blocker arrangement allow an inexpensive LED to be used as the light source, without requiring any complex collimator arrangement.
• the diameter of the beam blocker disc is sufficient to block all unscattered light from the LED. In other words, it has a diameter slightly larger than the focused spot diameter of the focusing lens. If no allergen-size particles are present, all light will be blocked by the beam blocker.
• the dimensions of the blocking assembly were arranged to block all light except that scattered by particles in the size range of 5 microns to 50 microns, although a size range of up to 0.5 to 500 microns may alternatively be used.
• a two-part beam blocking assembly comprising a first beam blocking device having a circle of light blocking material of predetermined diameter for blocking at least the unscattered portion of the light transmitted through the air sample, and a second beam blocking device having at least one pinhole for transmitting light in the predetermined angular range.
• the blocking circle in the first device is dimensioned to block unscattered light and light scattered at angles below the minimum angle in the predetermined range.
• the second device preferably has one aperture centered on the optical axis with a diameter such that light scattered at angles above the maximum angle in the range is blocked.
• the control circuit for generating the alarm output signal includes a pulse counter for counting the number of allergen particles detected in a certain time period.
• the pulse generator is arranged to trigger an alarm indicator if the number of counts in the selected time period is above a predetermined trigger value.
• the trigger level is adjustable, so that the user may select the sensitivity level.
• a method of detecting allergen particles in the air comprises the steps of directing a light beam through a sample of environmental air so that light will be scattered by any particles in the air, focusing the light beam onto a blocking member on the opposite side of the air sample which has a size greater than of the focused light beam, blocking light scattered outside a predetermined angle range on the opposite side of the air sample, transmitting only scattered light within the predetermined range of scattering angle, detecting the transmitted light and producing a first output signal at a level proportional to the amount of light transmitted, and generating an alarm output signal if the first output signal is above a predetermined level.
• This system and method readily discriminates between allergen-size particles in the 5 to 50 micron range and larger, non-allergenic particles so as to produce an accurate indication of the allergen particle levels in a room or enclosed area.
• the level at which the alarm signal is produced is adjustable.
• the apparatus can be readily connected to turn on auxiliary air cleaning appliances or filters such as HEPA filters.
• Figure 1 is a block diagram of an allergen particle detector apparatus according to a first embodiment of the invention
• Figure 2 is a block diagram illustrating a modified output control circuit
• Figure 3 is a block diagram of an allergen particle detector according to a second embodiment of the invention.
• Figure 4 is a block diagram similar to Figure 3 illustrating a modification.
• FIG. 1 of the drawings illustrates an allergen particle detector apparatus according to a first embodiment of the present invention.
• the apparatus will be enclosed in a suitable outer housing shaped to provide a passageway or air gap 10 for exposure to environmental air in order to test an air sample for allergen-size particles, as in our co-pending Application Serial No. 08/771,641 referred to above, the contents of which are incorporated herein by reference.
• a laser beam is directed from laser diode or LED 12 across the air sample 10 towards a beam blocking device 14 on the opposite side of the air gap.
• the device 14 comprises a transparent circular flat glass plate 15 with an opaque portion or disc 16 at the center of the plate. Portion 16 may be produced by black paint, or a black plastic or metal insert at the center of the plate.
• a focusing lens 18 in front of LED 12 is arranged to focus the laser output beam onto the beam blocking disc 16.
• the actual dimensions of the opaque blocking portion will be dependent on the cross-sectional shape and dimensions of the focused output beam of laser diode 12, and the particle size range to be detected by the apparatus.
• the LED may emit infrared light (0.8-1.0 micron) or visible light. In one embodiment of the invention an LED emitting at the wavelength of 670 nm. was used.
• the majority of allergen particles to which individuals may be sensitive are in the size range of 5 to 50 microns, although a small quantity of allergen particles may be found at sizes from 0.5 to 5 microns and from 50 to 500 microns. Thus, substantially all allergen particles will be found in the size range of 0.5 to 500 microns, with the maximum number being in the range of 5 to 50 microns. Therefore, the apparatus is preferably designed to detect particles in the size range of 0.5 to 500 microns, although it may alternatively be designed to detect particles in the range of 5 to 50 microns, since the majority of allergens will be in this size range.
• the angle at which light is scattered by a particle will be dependent on the wavelength of the light and the size of the particle. Airborne particles of different sizes have quite different light scattering properties. Larger particles will scatter light at smaller angles. For a red to infrared light source in the wavelength range of 0.6 micron to 1.0 micron, the smallest scattering angle for a particle size range of 0.5 to 50 microns is about 4° to 5° (see Electromagnetic Scattering, R.L. Rowell and R.S. Stein, ed., p. 140, Gordon and Breach 1965).
• the radius of the central blocking portion should be L * tan (5°), in order to block light scattered at angles less than 5°, i.e. light scattered by particles larger than 50 microns.
• the blocking device can therefore be arranged to block all light scattered by particles of size greater than 50 microns.
• Lens 20 is positioned behind blocking device 14 in order to focus light transmitted by the device 14 onto a detector 22.
• the output of detector 22 is connected via amplifier 24 to a threshold and timer circuit 26. If the output of detector 22 is above a predetermined threshold, relay switch 28 is closed to connect power supply 30 to the air filter 32, which may be any suitable HEPA filter.
• the power supply is also connected via adapter 34 to the laser diode .
• the beam blocking device 14 also includes an annular ring 42 of light blocking material is placed in front of disc 15. Alternatively, the disc itself may be painted black around a corresponding annular area.
• An annular ring through which light will be transmitted is defined between beam blocking disc 16 and annular ring 42.
• the light transmitting annular ring will have a predetermined inner diameter dl corresponding to the diameter of the center disc 16, and a predetermined outer diameter d2 corresponding to the inner diameter of ring 42.
• the dimensions dl and d2 will be determined based on the particle size range to be detected.
• the majority of allergen particles are in the size range of 0.5 to 50 microns. These will scatter light in the range of around 5° to 27°, as described above in connection with the first embodiment .
• the diameter dl is therefore determined from the relationship L * tan (5°) .
• the diameter d2 is determined from L * tan (27°), where L is the distance of the discriminator 118 from the sensitive region or air sample.
• L is the distance of the discriminator 118 from the sensitive region or air sample.
• FIG. 2 illustrates a modified output circuit for the allergen detector system, which provides greater sensitivity in situations where the actual number of allergens present in the air is low. Apart from the modified output circuit, the detector apparatus is otherwise identical to that of Figure 1, and like reference numerals are used for like parts as appropriate.
• the sample area or air gap 10 is of relatively small volume, of the order of a few cubic centimeters.
• the detector will register counts only in a discrete manner.
• signal pulses from detector 22 are connected to amplifier 24.
• the amplified pulse output is connected to comparator 50 to make a regulated pulse.
• the pulse output of comparator 50 is counted by pulse counter 52.
• a timing circuit 54 resets the pulse counter at predetermined intervals, for example every 30 seconds. Whenever there is an allergen particle in air gap 10, the scattered light will trigger the photodetector and subsequently the amplifier and comparator will produce an output pulse. This pulse represents detection of a single allergen particle.
• the pulse counter 52 registers all pulses in a certain period of time, determined by timing circuit 54. The total number of pulses registered is displayed on light emitting diode display unit 56. After each measurement period, say 30 seconds, the counter is reset to zero counts and begins to accumulate counts again.
• the counter trigger level is preferably adjustable by the user, so that different sensitivity levels can be detected as desired by the user. This arrangement permits measurement of allergen density in a low range, and is particularly useful with a stand-alone allergen detector unit, where no additional air moving apparatus is used. With such an arrangement, allergen particles will drift randomly into the air gap, and there may be periods during which no allergen particles are detected when the allergen density in the air is low. By accumulating particle counts over an extended period of time, lower allergen particle density levels may be detected. Any standard, off-the-shelf pulse counter may be used, such as a 7492 counter.
• Figure 3 of the drawings illustrates a modified allergen detector apparatus according to a second embodiment of the invention.
• the apparatus will be enclosed in a suitable housing (not illustrated) shaped to provide a passageway or air gap 60 for exposure to environmental air, in order to test an air sample within air gap 60 to detect the presence of allergen-size particles 62, as described in Application No. 08/771,641 referred to above.
• a laser beam 64 is directed from laser diode 66 through the air sample in gap 60.
• a reflecting concave mirror 68 with a central opening 70 of predetermined dimensions is positioned on the opposite side of air gap 60.
• a lens 18 (not illustrated) may be positioned between diode 66 and air gap 60 as in the previous embodiment in order to focus the laser output beam onto central opening 70 in the concave mirror, which acts in the same way as the beam blocking disc of the previous embodiment .
• the actual dimensions of the central opening 70 will be dependent on the cross -sectional shape and dimensions of the focused laser beam and the particle size range to be detected by the apparatus, as in the previous embodiment.
• Figure 4 illustrates a modification which is similar to the embodiment of Figure 3 with the exception that the central opening 70 in concave mirror 68 is replaced by a black beam blocker 72 which may be provided by black paint or a black disc applied to the mirror. All other parts of the embodiment of Figure 4 are identical to that of Figure 3, and like reference numerals have been used for like parts, as appropriate.
• the unscattered light beam 74 is eliminated, either by leaking through the central opening 70 in the mirror in Figure 3 to a beam dump 71, or by blocking it with beam blocker 72 at the center of the mirror, as in Figure 4.
• allergen particles in the air gap 60 will scatter the light beam, and the scattered light beam 75 will be reflected from the mirror 68 onto a photodetector 76 placed alongside the laser diode.
• the size of the central opening or beam blocker is preferably sufficient to block or receive unscattered portions of the light beam and portions scattered at angles below a predetermined minimum angle as described above in connection with the preceding embodiments, while the outer diameter of the mirror may be selected such that light scattered above a predetermined maximum angle passes the mirror without reflection.
• the light path is doubled back, shortening the overall length of the apparatus.
• the allergen particle detector of this invention detects only allergen-size particles and eliminates light scattered by particles of sizes outside the allergen size range of 0.5 to 50 microns.
• the light source is a simple and inexpensive laser light emitting diode, used with a focusing lens to focus the unscattered beam onto a beam blocking disc .
• the allergen detection level may be readily adjusted by the user.
• the apparatus is easy and inexpensive to manufacture, and simple to operate. It provides real time, accurate detection of excessive levels of allergen particles in the air, providing a warning to sensitive individuals who may need medication and also allowing allergen filtering equipment to be activated under such conditions to clean the air.

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• Chemical & Material Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Dispersion Chemistry (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Medicines Containing Antibodies Or Antigens For Use As Internal Diagnostic Agents (AREA)
• Investigating Or Analysing Biological Materials (AREA)

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• 1998
  • 1998-07-02 CN CN98806632A patent/CN1128352C/zh not_active Expired - Fee Related
  • 1998-07-02 JP JP50740699A patent/JP2002512698A/ja active Pending
  • 1998-07-02 EP EP98933119A patent/EP1000343B1/en not_active Expired - Lifetime
  • 1998-07-02 WO PCT/US1998/013837 patent/WO1999001748A1/en not_active Ceased
  • 1998-07-02 AU AU82856/98A patent/AU8285698A/en not_active Abandoned
  • 1998-07-02 DE DE69818480T patent/DE69818480T2/de not_active Expired - Lifetime
  • 1998-07-02 AT AT98933119T patent/ATE250757T1/de not_active IP Right Cessation
  • 1998-08-11 TW TW087110791A patent/TW494231B/zh not_active IP Right Cessation

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