JP2014182008A - Particle detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a particle detector capable of acquiring a size signal indicating a size of a floating particle and a shape signal indicating a shape of the floating particle on the basis of scattered light from the floating particle light-received from a light receiving optical system of one system.SOLUTION: A particle detector 10 for detecting pollen on the basis of characteristics of scattered light La radiated from a floating particle Pf irradiated with linear polarized light L includes a scattered light receiving part 120 including a single optical system for converging the scattered light on the scattered light receiving part. The scattered light receiving part 120 includes a polarized light receiving part for detecting a degree of a change in a polarization direction between the polarized light and the scattered light and a normal light receiving part for detecting intensity of the scattered light and is configured so that convergence spots obtained by converging the scattered light La by the optical system are formed on a light receiving area of the polarized light receiving part and a light receiving area of the normal light receiving part.

Description

  The present invention relates to a particle detector, and more particularly to a particle detector used for detecting pollen particles floating in the atmosphere that cause hay fever.

  In general, the amount of pollen floating in the atmosphere is measured by exposing the glass plate to the atmosphere, dyeing the pollen adhering to the glass plate, and using a microscope to visually count the number of pollen. Has been done by.

  However, this method requires a lot of time for the time-consuming pretreatment of dyeing, and requires a high level of skill for those who perform visual counting. Further, since the glass plate must be exposed to the atmosphere for a certain period of time, the amount of pollen scattering cannot be detected in real time, and furthermore, the measurement result cannot be obtained at the place to be measured.

  Therefore, a particle detector has already been developed as a device for detecting the amount of pollen scattered in real time at the measurement location.

  FIG. 9 is a diagram for explaining a conventional particle detector, and shows a basic configuration of the particle detector.

  The particle detector 200 receives a polarized light source 210 that irradiates floating particles with linearly polarized light L polarized in a predetermined direction, and receives the scattered light La from the suspended particles Pf to receive the shape of the suspended particles Pf (depolarized scattered light). Depolarization degree measuring unit 220a that outputs a shape signal (output signal) S2a representing the degree), and a size signal that represents the particle diameter (intensity of the scattered light) of the suspended particle Pf by receiving the scattered light Lb from the suspended particle Pf. Based on the scattered light intensity measurement unit 220b that outputs the output signal S2b, the shape signal S2a that represents the shape of the suspended particle Pf, and the size signal S2b that represents the particle diameter of the suspended particle Pf, the particle diameter is within a predetermined range. And a determination unit 230 that detects floating particles having a degree of depolarization larger than a predetermined value as pollen particles.

  Here, the polarized light source unit 210 includes a laser diode 211 that outputs linearly polarized light L, a drive unit 200a that drives the laser diode 211 with a drive signal S1, and linearly polarized light L output from the laser diode 211. When the suspended particle Pf at the focal position Fps of the condenser lens 212 is irradiated with the linearly polarized light L, Mie scattering occurs in the suspended particle Pf. It is like that. The scattered light La and Lb are due to Mie scattering caused by the incidence of incident light (linearly polarized light) L on the floating particle Pf, and the scattered light La is relative to the traveling direction (0 degree) of the incident light L. Light scattered at a scattering angle θa within a range of 30 degrees to 60 degrees, and the scattered light Lb is scattered at a scattering angle θb within a range of −30 degrees to −60 degrees with respect to the traveling direction of the incident light L. Light.

  The depolarization degree measuring unit 220a includes a light receiving side condensing lens 221a that condenses one scattered light La from the suspended particle Pf irradiated with the linearly polarized light L at the focal position Fps of the light emitting side condensing lens 212, and this The light receiving element 223a disposed at the focal position of the light receiving side condensing lens 221a and the same polarized light as the linearly polarized light L output from the laser diode 211 and disposed between the light receiving element 223a and the light emitting side condensing lens 221a. A polarization element (polarization filter) 222a that transmits only the direction component, and the output signal S2a corresponding to the intensity of the component in the same polarization direction as the linearly polarized light L in the scattered light La represents the shape of the suspended particle Pf It is configured to output as a signal.

  The scattered light intensity measurement unit 220b includes a light receiving side condensing lens 221b that condenses the other scattered light Lb from the suspended particles Pf irradiated with the linearly polarized light L at the focal position Fps of the light emitting side condensing lens 212, and this A light receiving element 223b disposed at the focal position of the light receiving side condensing lens 221b, and outputs an output signal S2b corresponding to the intensity of the scattered light Lb as a size signal representing the size (size) of the suspended particles Pf. It is configured as follows.

  In such a particle detector 200, the polarized light source unit 210, the depolarization measuring unit 220a, the scattered light intensity measuring unit 220b, and the determining unit 230 are provided in a casing (not shown). Ambient air can be introduced into the housing so as to pass through the focal position Fps of the light-emitting side focus lens 212, and pollen particles floating in the atmosphere can be detected based on the following principle.

  That is, in such a particle detector 200, first, the scattered light intensity, that is, the intensity of the scattered light generated by Mie scattering from the suspended particles irradiated with the output light from the laser diode 211 is determined by the particle size of the suspended particles. Based on the output signal S2b of the scattered light intensity measurement unit 220b that receives the scattered light Lb from the suspended particles Pf, the suspended particles having the same particle diameter as the pollen are detected using the fact that the larger the diameter is, the higher the diameter is. Yes.

  Secondly, the depolarization action of scattered light by pollen particles in the atmosphere, that is, the Mie scattering from floating particles irradiated with the linearly polarized light L with respect to the intensity of the linearly polarized light L that is the output light from the laser diode 211 The depolarization effect of the scattered light generated by other suspended particles having the same particle diameter as the pollen particles is a function of reducing the component in the same polarization direction as the linearly polarized light. The depolarization degree measuring unit 220a that receives the scattered light La from the suspended particles Pf through the polarization filter 222a that transmits only the component in the same polarization direction as the linearly polarized light L output from the laser diode 211 is utilized. The pollen and other suspended particles are discriminated based on the output signal S2a.

  Next, the operation will be described.

  First, a gas flow is introduced by a fan or a heater to introduce the atmosphere around the casing to the focal position Fps of the light emitting side focus lens 212 in the casing, and the linearly polarized light L output from the laser diode 211 is focused. Irradiate the suspended particles Pf passing through the position Fps.

  When the linearly polarized light L from the laser diode 211 is irradiated to the floating particle Pf, the floating particle Pf absorbs the linearly polarized light once and then emits scattered light in the traveling direction of the linearly polarized light L. On the other hand, the scattered light La is scattered at a scattering angle θa within a range of 30 ° to 60 °, and the scattered light Lb is scattered at a scattering angle θb within a range of −30 ° to −60 ° with respect to the traveling direction of the incident light L. Scattered.

  At this time, the scattered light La is condensed by the light receiving side focus lens 221a and enters the polarizing element 222a. In this polarizing element 222a, only a component of the scattered light La having a polarization direction equal to the polarization direction of the linearly polarized light L passes, and the light receiving element 223a receives the component of the scattered light that has passed through the polarizing element 222a, and the light. The output signal S2a corresponding to the intensity is output to the determination unit 230 as a shape signal indicating the shape of the floating element.

  On the other hand, the scattered light Lb scattered at the scattering angle θb within the range of −30 degrees to −60 degrees with respect to the traveling direction of the incident light L is condensed by the light receiving side condensing lens 221b and enters the light receiving element 223b. . The light receiving element 223b outputs an output signal S2b corresponding to the light intensity of the received scattered light Lb to the determination unit 230 as a size signal indicating the size of the floating element.

  In this determination unit 230, as shown in FIG. 10, with respect to the size signal S2b, the range of signal level A (PD2) for detecting suspended particles having a size of about pollen based on the average particle diameter of pollen. Rse is set. Further, regarding the ratio of the shape signal S2a to the size signal S2b (A (PD1) / A (PD2)), the range Rsp for determining that the suspended particles to be detected having the same particle diameter as the pollen is pollen. Is set. For this reason, in this determination part 230, it is determined based on the said size signal S2b and the shape signal S2a that the floating particle Pf which passed the said focus position (detection position) Fps is large pollen Fpa1, for example. Here, the reciprocal of the ratio (A (PD1) / A (PD2)) corresponds to the degree of depolarization indicating how much the linearly polarized light L from the laser diode 211 has changed by passing through the polarizing filter. The particle Fpa2 is small pollen, the particle Fpa3 is dust having the same size as the large pollen, and the particle Fpa4 is dust having the same size as the small pollen.

  Patent Document 1 discloses a pollen detector similar to the conventional particle detector shown in FIG.

Japanese Patent Laid-Open No. 5-240768

  However, in the conventional particle detector 200, as a light receiving optical system for receiving the scattered light La and Lb from the suspended particles Pf, a polarizing optical system for receiving the scattered light La via the polarizing element 222a (depolarization) Optical system of the degree measurement unit 220a) and a non-polarization optical system (optical system of the scattered light intensity measurement unit 220b) for receiving the scattered light Lb from the suspended particles Pf without changing the polarization direction. A light receiving optical system is necessary, and the apparatus becomes large, resulting in an increase in cost.

  The present invention has been made to solve such problems, and based on scattered light from suspended particles received by a single light receiving optical system, a size signal indicating the size of suspended particles and a floating signal are provided. The shape signal indicating the shape of the particle can be acquired, and thus the amount of pollen scattering can be measured in real time at the place where measurement is desired, and the particle can be reduced in size and can be reduced in cost. The purpose is to obtain a detector.

  The particle detector according to the present invention includes a polarized light irradiation unit that irradiates polarized light on airborne particles and a scattered light receiving unit that receives scattered light from the suspended particles, and the received scattered light. A particle detector for detecting pollen based on the characteristics of the optical system, comprising a single optical system that collects the scattered light, wherein the scattered light receiving unit is between the polarized light and the scattered light. A first light detection unit that detects the degree of change in the polarization direction; and a second light detection unit that detects the intensity of the scattered light, the light receiving region of the first light detection unit, and the second light detection unit. On the light receiving area of the light detection section, a condensing spot obtained by condensing the scattered light by the optical system is formed, whereby the above object is achieved.

  According to the present invention, in the particle detector, the polarized light is linearly polarized light, and the first light detection unit is configured to detect light of a component having the same polarization direction as the polarization direction of the linearly polarized light in the scattered light. It is preferably configured to detect the intensity.

  The present invention provides the particle detector, wherein the first light detection unit includes a first photoelectric conversion element formed on a semiconductor substrate constituting a semiconductor chip, and the first photoelectric conversion element includes: It has a polarization function of transmitting only light having the same polarization direction as that of linearly polarized light, and photoelectrically converts light having the same polarization direction as that of the linearly polarized light in the scattered light from the suspended particles, It is configured to output a shape signal indicating the shape of the suspended particles, and the second light detection unit includes a second photoelectric conversion element formed on the semiconductor substrate, and is scattered from the suspended particles. It is preferable that the light is photoelectrically converted by the second photoelectric conversion element and an intensity signal indicating the intensity of the scattered light is output.

  According to the present invention, in the particle detector, the first photoelectric conversion element that outputs the shape signal and the second photoelectric conversion element that outputs the intensity signal are alternately arranged on the semiconductor chip. It is preferable.

  According to the present invention, in the particle detector, the first photoelectric conversion element having the polarization function has a structure in which a striped light reflection layer is formed on a semiconductor region constituting the first photoelectric conversion element. Preferably it is.

  According to the present invention, in the particle detector, the photoelectric conversion element is preferably a PIN photodiode.

  According to the present invention, in the particle detector, in addition to the first photoelectric conversion element and the second photoelectric conversion element, the semiconductor chip includes the shape signal and the intensity signal output from these photoelectric conversion elements. It is preferable to have an analog signal processing circuit for processing.

  According to the present invention, in the particle detector, the analog signal processing circuit has a predetermined particle size of the suspended particles indicated by the intensity signal and a predetermined degree of change in the polarization direction indicated by the shape signal. It is preferable to have a discrimination unit that discriminates floating particles larger than the value as pollen particles.

  In the particle detector according to the aspect of the invention, it is preferable that the semiconductor chip includes a digital signal processing circuit that outputs a determination result of the determination unit as a digital signal.

  In the particle detector according to the aspect of the invention, it is preferable that the polarized light irradiation unit includes a laser diode that outputs linearly polarized light as the polarized light.

  The present invention provides the particle detector, wherein the polarized light irradiation unit includes a light emitting diode and a polarizing element that polarizes output light output from the light emitting diode, and the linearly polarized light transmitted through the polarizing element is It is preferable to irradiate suspended particles.

  As described above, according to the present invention, the size signal indicating the size of the suspended particle and the shape signal indicating the shape of the suspended particle are generated based on the scattered light from the suspended particle received by the one light receiving optical system. Thus, it is possible to measure the amount of pollen scattering in real time at a place where measurement is desired, and to obtain a particle detector having a small and compact structure that can be reduced in cost.

1A and 1B are diagrams for explaining a particle detector according to Embodiment 1 of the present invention. FIG. 1A shows the appearance of the particle detector, and FIG. 1B shows the inside of the particle detector. The structure is shown. FIG. 2 is a plan view for explaining the particle detector according to the first embodiment of the present invention, and shows the configuration of a particle detection IC chip used in the particle detector. FIG. 3 is a cross-sectional view illustrating the particle detector according to Embodiment 1 of the present invention. FIG. 3A schematically shows a cross-sectional structure taken along the line AA ′ in FIG. FIG. 3B is an enlarged view of the portion X in FIG. FIG. 4 is a diagram for explaining the basic configuration and operation principle of the particle detector according to the first embodiment of the present invention. FIG. 4 (a) is a diagram of the polarized light irradiation unit and the scattered light reception unit in FIG. 1 (b). An optical system is schematically shown, and FIG. 4B shows a pollen determination method. FIG. 5 is a diagram for explaining the operation principle of the particle detector according to the first embodiment of the present invention. FIGS. 5A and 5B show the direction of the slit of the polarizing element and the polarizing element. The relationship with the polarization direction of linearly polarized light is shown. FIG. 6 is a diagram for explaining suspended particles to be determined by the particle detector according to the first embodiment of the present invention. FIG. 6A schematically shows the shape of cedar pollen by a micrograph, and FIG. (B) has shown typically the shape of the dust by a microscope picture. FIG. 7 is a diagram for explaining the operation of the particle detector according to the first embodiment of the present invention. The scattering state of the laser beam for detection and the output level of the shape signal and the size signal are floated at the detection position of the suspended particles. When there are no particles (FIG. 7A), when there are floating particles smaller than pollen at the detection position of floating particles (FIG. 7B), there are floating particles other than pollen at the detection position of floating particles. In the case (FIG. 7C), the case where pollen is present at the detection position of suspended particles (FIG. 7D) is shown. FIG. 8 is a diagram for explaining a particle detector according to a modification of the first embodiment of the present invention. FIG. 8A shows the appearance of the particle detector, and FIG. 8B shows the particle detector. The internal structure of the vessel is shown. FIG. 9 is a diagram for explaining a conventional particle detector, and shows a basic configuration of the particle detector. FIG. 10 is a diagram for explaining the operation principle of a conventional particle detector, and shows a method for detecting pollen separately from other suspended particles.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
1A and 1B are diagrams for explaining a particle detector according to Embodiment 1 of the present invention. FIG. 1A shows the appearance of the particle detector, and FIG. 1B shows the inside of the particle detector. The structure is shown.

  The particle detector 10 according to the first embodiment includes a housing 10a such as a metal case or a plastic case, and polarized light that is provided in the housing 10a and irradiates the suspended particles Pf with incident light L polarized in a predetermined direction. The light irradiation part 110 and the scattered light light-receiving part 120 which receives the scattered light La by the floating particle Pf are provided. Here, the polarized light irradiation unit 110 and the scattered light receiving unit 120 are provided to face both upper corners of the housing 10a, and the optical axis Ax1 of the irradiation optical system of the polarized light irradiation unit 110 and the scattering The optical axis Ax2 of the light receiving optical system of the light receiving unit 120 is positioned so as to intersect at the detection position Fps of suspended particles. Specifically, the optical axis Ax2 of the light receiving optical system is set to make an angle of 30 degrees to 60 degrees with respect to the optical axis Ax1 of the irradiation optical system (that is, the traveling direction of the incident light L).

  Further, the casing 10a is configured such that when outside air around the casing 10a is taken into the casing 10a, the outside air passes through the outside air discharge region 10c centered on the detection position Fps. An outside air discharge port 10b for discharging the taken outside air is formed on the side surface of 10a. Further, a plurality of shields are provided in the housing 10 a so that light reflected by the inner wall surface of the housing 10 a and the outer wall surfaces of the polarized light irradiation unit 110 and the scattered light receiving unit 120 does not enter the scattered light receiving unit 120. The plates 11a to 11d are provided so as not to block the optical paths of the irradiation optical system and the light receiving optical system.

  The polarized light irradiation unit 110 is configured as a unit that forms an irradiation optical system that condenses incident light (linearly polarized light) L linearly polarized in a predetermined direction at a detection position Fps of suspended particles. Case member 110a, laser diode 111 attached to the inner wall surface of case member 110a, drive unit 111a attached to case member 110a for driving laser diode 111, attached to case member 110a, and laser diode And an irradiation side condensing lens 112 that condenses the light emitted from the light source 111. The irradiation side condensing lens 112 condenses the laser light L so that a condensing spot having the same size as the particle diameter (30 μm to several tens μm) to be measured is formed at the focal position Fps. It is configured to shine. The focal position Fps of the irradiation side condensing lens 112 is a position at which laser particles are irradiated to floating particles floating in the air that is particles to be measured.

  The scattered light receiving unit 120 is also configured as a unit that forms a light receiving optical system that receives scattered light from suspended particles irradiated with laser light. For example, a rectangular parallelepiped case member 120a and the case member 120a A particle detection IC chip 100 attached to the inner wall surface of the light receiving side, and a light receiving side condensing lens 121 attached to the side wall of the case member 120a so as to face the light receiving chip 100 and condensing scattered light La from the suspended particles. Have. The light receiving side condensing lens 121 condenses the scattered light La to form a condensing spot Bsp having a diameter of about 300 μm at the focal position.

  FIG. 2 is a plan view showing the configuration of the particle detection IC chip used in the particle detector of the first embodiment, and FIG. 3A schematically shows a cross-sectional structure taken along the line AA ′ in FIG. FIG. 3 (b) shows an enlarged view of the structure of the X portion in FIG. 3 (a). Further, FIG. 4 is a diagram for explaining the basic configuration and operation principle of the particle detector according to the first embodiment of the present invention. FIG. 4A is a diagram illustrating a polarized light irradiation unit and scattered light reception in FIG. The optical system in a part is typically shown, and FIG.4 (b) has shown the method of pollen determination.

  The particle detection IC chip 100 includes a P-type semiconductor region 102 formed on a semiconductor substrate (for example, a silicon substrate) 101, and N-type semiconductor regions 130 and 140 formed on the P-type semiconductor region 102. ing. Here, the P-type semiconductor region 102 is a diffusion region obtained by diffusion of P-type impurities into the semiconductor substrate 101, and the N-type semiconductor regions 130 and 140 are obtained by diffusion of N-type impurities into the P-type semiconductor region 102. N-type diffusion region. The N-type semiconductor region 130 and the P-type semiconductor region 102 constitute a PIN photodiode as the light receiving element P2a, and the N-type semiconductor region 140 and the P-type semiconductor region 102 constitute a PIN photodiode as the light receiving element P1a. Yes. The light receiving elements P2b and P1b are also formed as PIN photodiodes in the surface region of the semiconductor substrate 101, like the light receiving elements P2a and P1a.

  Further, the particle detection IC chip 100 has circuit elements that are formed on the semiconductor substrate 101 and constitute the signal processing unit Rc.

  Here, the N-type semiconductor regions 130 and 140 constituting each light receiving element have a square shape as a planar shape, and the light receiving elements P1a, P1b, P2a, and P2b are arranged in a matrix of 2 rows and 2 columns. Thus, a light receiving region Rpd having a substantially square shape is formed. The length of the diagonal line of the light receiving region Rpd is approximately the same as the diameter of the condensed spot Bsp of the scattered light collected by the light receiving side condensing lens 121. The light receiving elements P1a and P1b are PIN photodiodes (polarized PIN photodiodes) configured to receive the scattered light La from the floating particles Pf via the polarizing elements, and the light receiving elements P2a and P2b are the floating particles Pf. PIN photodiodes (usually photodiodes) that directly receive the scattered light L from the light, and as shown in FIG. 2, these photodiodes are polarized PIN photodiodes in the row direction or column direction, and usually PIN photodiodes. They are arranged alternately so that they are not adjacent to each other.

  Further, as shown in FIG. 3, a first insulating film (for example, silicon oxide film) 103 is formed on the surface of the P-type semiconductor region 102. Electrodes 131 and 141 are formed on the N-type semiconductor regions 130 and 140 in the P-type semiconductor region 102 through contact holes formed in the first insulating film 103. Electrodes 132 and 142 are formed through contact holes formed in the first insulating film 103 at portions adjacent to the N-type semiconductor regions 130 and 140. These electrodes are formed by patterning a first metal layer (eg, an aluminum layer) formed on the first insulating film 103.

  A second insulating film 105 is formed on the first insulating film 103 so as to cover these electrodes, and a second metal layer (for example, an aluminum layer) is formed on the second insulating film 105. ) 106 is formed. In this second metal layer 106, an opening (light receiving region of the second photodetecting portion) 106a is formed so as to be positioned on the N-type semiconductor region 130 of the light receiving elements (usually PIN photodiodes) P2a and P2b. A wire grid polarization portion (light receiving region of the first light detection portion) 106b is formed so as to be positioned on the N-type semiconductor region 140 of the light receiving elements (polarized PIN photodiodes) P1a and P1b. The opening 106 a and the wire grid polarization portion 106 b of the second metal layer 106 are each formed by patterning the second metal layer 106.

  Here, a 0.18 μm process is used to form the wire grid polarization unit 106b, and the wire grid polarization unit 106b is formed of the polarization PIN photodiodes P1a and P1b of the second metal layer (for example, an aluminum layer) 106. This is obtained by forming a plurality of strip-shaped openings 106b1 in a portion located on the N-type semiconductor region 140, and the interval Dg between adjacent strip-shaped light shielding portions (hereinafter also referred to as wire portions) 106b2 is shown in FIG. As shown in FIG. 3B, for example, it is 230 nm. However, when the incident light from the laser diode 111 is light with a wavelength of 960 nm (near infrared light), the interval Dg between the wire portions 106b2 is preferably about 480 nm to 192 nm, and the height Hg of the wire portion 106b2 is About 150 nm is preferable. That is, in the wire grid polarization unit 106b, it is desirable that the wire units 106b2 are arranged in stripes at intervals of 1/2 to 1/5 of the wavelength of incident light. The width of the wire portion 106b2 can be reduced to about 200 nm when a 0.18 μm process is used, and further can be reduced to about 50 nm when a process with high processing accuracy is used. . By thinning the wire part, it is possible to improve the separation performance between the transmitted light in the polarization direction and the other light, and further widen the frequency range of light used as incident light (laser diode output light). In addition, the amount of light incident on the light receiving region can be increased.

  Moreover, the material which comprises a wire part is not restricted to aluminum, Silver (Ag), copper (Cu), etc. which an electron can move freely may be sufficient. In this case, only the wire grid polarization part 106b may be formed of another metal layer made of a material different from that of the second metal layer (aluminum layer).

  Hereinafter, the function of the wire grid polarization unit (that is, the polarization element) will be briefly described.

  FIG. 5A and FIG. 5B show the relationship between the direction of the light transmission slit (band-shaped opening) of the polarizing element and the polarization direction of the linearly polarized light that passes through the polarizing element.

  In the following description, the wire grid polarization unit 106b in the particle detection IC chip will be described as the polarization element Ep.

  For example, when linearly polarized light Lv whose polarization direction is the vertical direction Dv is incident on the polarization element Ep (wire grid polarization unit 106b2) whose longitudinal direction is the vertical direction of the light transmission slit Ep1 (band-shaped opening 106b1) (FIG. 5). In (a)), the linearly polarized light Lv is reflected by the polarizing element Ep and does not pass through the polarizing element Ep. This is because the electrons e in the stripe-shaped reflection part Ep2 (wire part 106b2) are moved by incident light (that is, incident electromagnetic waves) and radiate electromagnetic waves so as to cancel the propagating electromagnetic waves (incident light). It is.

  On the other hand, when the linearly polarized light Lh whose polarization direction is the horizontal direction Dh is incident on the polarization element Ep (wire grid polarization unit 106b) whose longitudinal direction is the vertical direction of the light transmission slit Ep1 (band-like opening 106b1) (FIG. 5). In (b)), the linearly polarized light Lh passes through the polarizing element Ep without being reflected by the polarizing element Ep.

  In the particle detection IC chip 100, the light receiving elements (usually PIN photodiodes) P2a and P2b each have one normal light receiving unit (second light detecting unit) that outputs a size signal indicating the size of suspended particles from the scattered light. ) PD2 is configured, and the light receiving elements (polarized PIN photodiodes) P1a and P1b receive the scattered light via the polarization unit and output a shape signal indicating the shape of the suspended particle (whether or not it is spherical). Another polarized light receiving unit (first photodetecting unit) PD1 is configured.

  Further, the particle detection IC chip 100 has an analog circuit (AFE circuit) as the signal processing unit Rc, and the analog circuit has a size signal S2b from the normal light receiving unit PD2 and a shape signal S2a from the polarized light receiving unit PD1. And a determination unit 118 that determines whether or not the suspended particles are pollen based on the comparison result. Further, the signal processing unit Rc has a digital circuit (not shown) that converts the determination result for each suspended particle output from the determination unit 118 into a digital signal Sd and outputs the digital signal Sd. Therefore, based on the digital signal Sd, the external computer (PC) 50 performs a process of counting the determination results, and the amount of pollen scattering in the air is obtained.

  FIG. 6 is a diagram for explaining suspended particles to be determined by the particle detector according to the first embodiment. FIG. 6A schematically shows the shape of cedar pollen by a micrograph, and FIG. ) Schematically shows the shape of the dust in the micrograph.

  The shape of pollen Pa is substantially spherical as shown in FIG. 6 (a), whereas the shape of dust Pb in the atmosphere is non-spherical as shown in FIG. 6 (b). Does not have a fixed shape (substantially spherical).

  Thus, pollen Pa has a substantially spherical shape, so that the polarization direction of scattered light from pollen particles is a laser diode compared to other suspended particles having the same particle diameter as pollen particles. It has the characteristic that it changes greatly with respect to the polarization direction of the light (laser light) emitted from. Here, this characteristic is the ratio of the intensity of the light component in the same polarization direction as that of the laser light (incident light) incident on the suspended particles in the scattered light to the intensity of the scattered light, that is, the normal light receiving unit PD2. Is expressed by the ratio (A (PD1) / A (PD2)) of the output (A (PD1)) of the polarized light receiving unit PD1 to the output (A (PD2)) of (A (PD2)).

  The small output ratio (A (PD1) / A (PD2)) means that the change in polarization direction (degree of depolarization) between incident light and scattered light due to its Mie scattering is large. As shown in FIG. 4B, the floating particles have a spherical shape (pollen shape).

  On the other hand, a large output ratio (A (PD1) / A (PD2)) indicates a small change in polarization direction (degree of depolarization) between incident light and scattered light due to its Mie scattering, As shown in FIG.4 (b), it shows that the shape of a floating particle is non-spherical (shape of particles other than pollen).

  FIG. 4B shows the scattered light intensity (scattering intensity) corresponding to the range of the particle diameter of the pollen particles (30 μm to several tens of μm), that is, the output of the normal light receiving unit PD2 (A (PD2)). A range of is shown.

  Next, the operation will be described.

  For example, the operation of this particle detector will be described for the case where the particle detector 10 of Embodiment 1 is placed in a 100-leaf box (not shown) and the amount of pollen in the air is measured.

  In addition, the 100 boxes have a configuration in which outside air is always introduced into the 100 leaves box at a constant flow rate, and the particle detector 10 is installed in the 100 leaves box so that the outside air is introduced into the housing by the air flow in the 100 leaves box. To do.

  First, in the polarized light irradiation unit 110, when the drive unit 111a drives the laser diode 111 with the drive signal S1, the laser diode 111 emits linearly polarized light L. The linearly polarized light L is condensed by the irradiation side condensing lens 112 and irradiated to the suspended particles Pf located at the focal position Fps.

  When the linearly polarized light L from the laser diode 111 is irradiated to the floating particle Pf, the floating particle Pf absorbs the linearly polarized light once and then emits the scattered light to the traveling direction of the linearly polarized light L. On the other hand, the scattered light La is scattered at a scattering angle θa within a range of 30 ° to 60 °, and the scattered light Lb is scattered at a scattering angle θb within a range of −30 ° to −60 ° with respect to the traveling direction of the incident light L. Scatter (see FIG. 4). In FIG. 1, the scattered light Lb is not shown. The scattering angle θa of the scattered light La is determined by the wavelength of the laser light and the size of the particles irradiated with the laser light. For example, in the case of causing Mie scattering by irradiating floating particles having a particle diameter of about 30 μm, if the wavelength of the laser beam is set to 640 nm (red light), the above range of scattering angles (with respect to the traveling direction of incident light) The scattered light is emitted from the suspended particles in the range of 30 to 60 degrees and in the range of -30 to -60 degrees.

  At this time, the scattered light La is introduced into the light receiving region Rpd of the particle detection IC chip 100 of the scattered light receiving unit 120 by the light receiving optical system of the scattered light receiving unit 120. That is, the scattered light La is condensed by the light receiving side condensing lens 121 to form a condensing spot Bsp (FIG. 2) on the light receiving region Rpd of the particle detection IC chip 100.

  Thereby, the scattered light La is directly received by the light receiving elements P2a and P2b of the particle detection IC chip 100, and photoelectric conversion is performed. The photoelectric conversion signal of these light receiving elements is a normal light receiving unit PD2 including the light receiving elements P2a and P2b. Is output to the signal processing unit Rc as a floating particle size signal S2b.

  That is, the output signal S2b of the normal light receiving unit PD2 indicates the intensity of the scattered light from the suspended particles irradiated with the incident light from the laser diode 111. The intensity of the scattered light increases as the particle diameter of the suspended particles increases. Since it is large, the signal processing unit Rc compares the output signal threshold range corresponding to the particle diameter of the pollen with the output signal S2b of the normal light receiving unit PD2, so that the suspended particles irradiated with the incident light are pollen. It can be determined whether or not the particles have the same particle diameter.

  Further, in the light receiving elements P1a and P1b of the particle detection IC chip 100, the scattered light La is received through the wire grid portion (polarizing element) 106b and subjected to photoelectric conversion. Here, the wire grid portion (polarizing element) 106 is configured to transmit only a component having the same polarization direction as the polarization direction of linearly polarized light output from the laser diode 111 of the polarized light irradiation unit 110. The photoelectric conversion signals of these light receiving elements P1a and P1b are output to the signal processing unit Rc as the floating particle shape signal S2a which is the output signal of the polarization light receiving unit PD1 including the light receiving elements P1a and P1b.

  That is, the output signal S2a of the polarized light receiving unit PD1 indicates how much the polarization direction of the linearly polarized light output from the laser diode 111 has changed due to Mie scattering, and the degree of change in this polarization direction is determined in advance. If it is equal to or greater than the threshold value, it can be determined that the suspended particles having the same particle diameter as pollen have a substantially spherical shape, that is, pollen.

  Hereinafter, a method for specifically determining the type of suspended particles will be described.

  FIG. 7 is a diagram for explaining the operation of the particle detector according to the first embodiment of the present invention. The scattering state of the laser beam for detection and the output level of the shape signal and the size signal are floated at the detection position of the suspended particles. When there are no particles (FIG. 7A), when there are floating particles smaller than pollen at the detection position of floating particles (FIG. 7B), there are floating particles other than pollen at the detection position of floating particles. In the case (FIG. 7C), the case where pollen is present at the detection position of suspended particles (FIG. 7D) is shown.

  For example, when there is no floating particle at the detection position of the floating particle (FIG. 7A), the emitted laser light L passes through the detection position Fps of the floating particle and goes straight as it is. Scattered light does not enter the system (light receiving optical system). For this reason, the output levels of the output signal S2b of the normal light receiving unit PD2 and the output signal S2a of the polarized light receiving unit PD1 are 0 level.

  In addition, when the suspended particle Pf smaller than pollen exists at the suspended particle detection position Fps (FIG. 7B), scattered light is radiated from the suspended particle Pf in all directions at the suspended particle detection position Fps. For this reason, the output levels of the output signal S2b of the normal light receiving unit PD2 and the output signal S2a of the polarized light receiving unit PD1 are both low.

  Further, when there are floating particles other than pollen having the same particle size as that of pollen (FIG. 7 (c)), the normal light receiving portion PD2 has a large particle size. The level of the output signal S2b becomes higher. Further, since the suspended particles other than pollen are non-spherical, the polarization direction of the scattered light from the suspended particles hardly changes with respect to the polarization direction of the linearly polarized outgoing laser beam. Therefore, the output level of the output signal S2a of the polarized light receiving part PD1 is also high.

  Furthermore, when pollen is present at the floating particle detection position Fps (FIG. 7D), the level of the output signal S2b of the normal light receiving unit PD2 becomes high because the particle diameter of the floating particle Pf is large. Further, the polarization direction of the scattered light from the suspended particles greatly changes with respect to the polarization direction of the output laser light that has been linearly polarized because the pollen has a spherical shape. Therefore, the output level of the output signal S2a of the polarized light receiving unit PD1 is low. Therefore, from the output signal S2b of the normal light receiving unit PD2 and the output signal S2a of the polarized light receiving unit PD1, the suspended particles have a large scattering intensity and a small output ratio (A (PD1) / A (PD2)). As a result, it is possible to determine that the suspended particles are pollen as shown in FIG.

  Thus, in the particle detector according to the first embodiment, in the particle detector 10 that detects pollen based on the characteristics of the scattered light La emitted from the suspended particles Pf irradiated with the linearly polarized light L, the scattered light is The scattered light receiving unit 120 includes a single optical system that focuses the scattered light on the scattered light receiving unit, and the scattered light receiving unit 120 changes the polarization direction between the polarized light and the scattered light. A light receiving region of the polarized light receiving unit PD1 includes a polarized light receiving unit (first light detecting unit) PD1 for detecting the degree and a normal light receiving unit (second light detecting unit) PD2 for detecting the intensity of the scattered light. In addition, since the condensing spot Bsp obtained by condensing the scattered light by the optical system is formed on the light receiving area of the normal light receiving unit PD2, light is received by one light receiving optical system. Based on the scattered light La from the suspended particles Pf, The size signal S2b indicating the size and the shape signal S2a indicating the shape of the suspended particles can be acquired, whereby the amount of pollen scattering can be measured in real time at the place where measurement is desired, and the cost can be reduced. It is possible to obtain a particle detector 10 having a small and compact structure capable of satisfying the requirements.

  In the first embodiment, the polarized light irradiation unit 110 uses a laser diode to generate linearly polarized light. However, the configuration for generating linearly polarized light is not limited to that of the first embodiment. Absent.

  FIG. 8 is a diagram for explaining a particle detector according to a modification of the first embodiment of the present invention.

  In the particle detector 20 according to the modification of the first embodiment, instead of the polarized light irradiation unit 110 in the particle detector of the first embodiment, a light emitting diode 151 and a polarizing element 153 that linearly polarizes light emitted from the light emitting diode 151. And a polarized light irradiation unit 150 including a condenser lens 112 that collects the irradiation light linearly polarized by the polarizing element 153 and a diaphragm member 154 disposed therebetween.

  In the particle detector 20 according to the modification of the first embodiment having such a configuration, in addition to the effects of the first embodiment, not only linearly polarized light but also polarized light such as elliptically polarized light can be generated in accordance with the characteristics of the polarizing element. In addition, when an inexpensive light emitting element having a low directivity of the emitted light is used as compared with the laser diode, the emitted light can be incident only on the outgoing side condensing lens by the diaphragm member.

  In the first embodiment, the side polarization measurement unit 28 is set to measure scattered light in a direction orthogonal to the incident optical axis so that the maximum degree of depolarization can be obtained. It is also possible to set to.

  In the first embodiment, the configuration for introducing the ambient air around the particle detector into the case of the particle detector is a heater for generating an updraft or flows in an arbitrary direction. A fan or the like that generates airflow can be used.

  Furthermore, when this particle detector is attached to an air purifier or an air conditioning / heating device, a mechanism for generating an air flow is not provided in the particle detector, but an air flow generated by these devices is used to Outside air may be introduced into the housing. Moreover, when the particle detector of the said Embodiment 1 is mounted in household appliances, such as an air cleaner and an air conditioning apparatus, the operation mode of these apparatuses can also be controlled according to the scattering state of pollen.

  Moreover, a filter may be provided in the passage of the airflow that flows into the particle detector to remove particles larger than the particle diameter of the pollen. In this case, since the particle diameter of the suspended particles to be determined is limited by the filter in advance, the measurement accuracy of the particle diameter of the suspended particles can be further increased.

  Moreover, although the said Embodiment 1 demonstrated the case where incident light was linearly polarized light, the polarization state by Mie scattering by pollen between the incident light which injects into pollen, and the scattered light radiated | emitted from pollen The incident light is not limited to linearly polarized light, and elliptically polarized light or the like can be used as described in the modification of the first embodiment.

  As mentioned above, although this invention has been illustrated using preferable embodiment of this invention, this invention should not be limited and limited to this embodiment. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments of the present invention. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  In the field of particle detectors, the present invention provides a size signal indicating the size of suspended particles and a shape signal indicating the shape of suspended particles based on scattered light from suspended particles received by a single light receiving optical system. Thus, it is possible to measure the amount of pollen scattering in real time at a place where measurement is desired, and to obtain a particle detector having a small and compact structure that can be reduced in cost.

DESCRIPTION OF SYMBOLS 10, 20 Particle detector 10a Case 10b Outside air discharge port 10c Outside air discharge area 11a-11d Shielding plate 100 Particle detection IC chip 101 Semiconductor substrate (silicon substrate)
102 P-type semiconductor region 103 First insulating film 105 Second insulating film 106 Second metal layer (for example, aluminum layer)
106a Opening (light receiving region of second light detection unit)
106b Wire grid polarization unit (light receiving region of first light detection unit)
106b1 Band-shaped opening 106b2 Band-shaped light shielding part (wire part)
110a Case member 111 Laser diode 112 Irradiation side condensing lens 110, 150 Polarized light irradiation part 120 Scattered light receiving part 121 Light receiving side condensing lens 130, 140 N-type semiconductor region 131, 132, 141, 142 Electrode 151 Light emitting diode 153 Polarization Element 154 Aperture member Ax1 Optical axis of irradiation optical system Ax2 Optical axis of light receiving optical system e Electron Ep Polarizing element Fps Detection position of suspended particles L Incident light La Scattered light P1a, P1b Light receiving element (polarized PIN photodiode)
P2a, P2b Light-receiving element (usually PIN photodiode)
Pa pollen Pb Dust PD1 Polarized light receiving part (first light detecting part)
PD2 Normal light receiving part (second light detecting part)
Pf Airborne particle Rc Signal processor Rpd Light receiving area

Claims (5)

It has a polarized light irradiating unit that irradiates polarized light to airborne suspended particles and a scattered light receiving unit that receives scattered light from the suspended particles, and detects pollen based on the characteristics of the received scattered light. A particle detector,
A single optical system for collecting the scattered light,
The scattered light receiver is
A first light detection unit that detects the degree of change in polarization direction between the polarized light and the scattered light; and a second light detection unit that detects the intensity of the scattered light, A condensing spot obtained by condensing the scattered light by the optical system is formed on the light receiving region of the first light detecting unit and the light receiving region of the second light detecting unit. , Particle detector. The polarized light is linearly polarized light,
The particle detector according to claim 1, wherein the first light detection unit is configured to detect light intensity of a component having the same polarization direction as the polarization direction of the linearly polarized light in the scattered light. The first light detection unit includes a first photoelectric conversion element formed on a semiconductor substrate constituting a semiconductor chip, and the first photoelectric conversion element has the same polarization direction as the polarization direction of the linearly polarized light. A shape signal indicating the shape of the suspended particles by photoelectrically converting light having the same polarization direction as that of the linearly polarized light in the scattered light from the suspended particles. Configured to output,
The second light detection unit includes a second photoelectric conversion element formed on the semiconductor substrate, and the scattered light from the floating particles is photoelectrically converted by the second photoelectric conversion element, and the scattered light is converted. The particle detector according to claim 2, wherein the particle detector is configured to output an intensity signal indicating the intensity of.   The particle detector according to claim 3, wherein the first photoelectric conversion element that outputs the shape signal and the second photoelectric conversion element that outputs the intensity signal are alternately arranged on the semiconductor chip. .   The first photoelectric conversion element having the polarization function has a structure in which a stripe-shaped light reflecting layer is formed on a semiconductor region constituting the first photoelectric conversion element. The described particle detector.

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