Particle detection sensor and particle detection apparatus

[Object] To provide a particle detection sensor that is compact-and-flat designed and manufacturable at low cost.[Solution] A particle detection sensor (1) includes light transmissive resin (5) that encapsulates a light emitting element (3) and a light receiving element (6), and a reflective surface (7) that is arranged on the light transmissive resin (5) and reflects output light (8) radiated from the light emitting element (3) toward an incident light field area (10).

TECHNICAL FIELD

The present invention relates to a particle detection sensor and a particle detection apparatus detecting particles, such as dirt in air and cigarette smoke.

BACKGROUND ART

Particle detection sensors detect the presence or absence of particles by radiating output light (irradiation beam) from a light emitting element toward an incident light field area (detection region) of a light receiving element and by detecting with the light receiving unit scattered light caused when the output light impinges on the particles within the incident light field area. More in detail, the particle detection sensor detects the density of particles (uncleanness) or the type of particles with reference to an amount of scattered light (luminance) or detection frequency of the scattered light.

The particle detection sensors of related art employ detection methods that are generally divided into two types, namely, average density method and particle count method. In the average density method, a light emitting element is lit in a pulse, and an amount of particles is detected by detecting an amount of scattered light that is caused when light from the light emitting element impinges on particles within an incident light field area of a light receiving unit during a time period throughout which the light emitting element is lit. On the other hand, in the particle count method, a light emitting element is continuously lit, and an intensity and a frequency of occurrence of scattered light caused when particles pass across a beam of concentrated output light. A type and density of the particles are then detected.

The particle detection sensor based on the average density method is disclosed in Patent Literature 1. The particle detection sensor based on the particle count method is disclosed in Patent Literature 2.

These particle detection sensors involve detecting the scattered light that is caused when the output light impinges on the particles within the incident light field area of the light receiving unit and thus need to radiate the output light from the light emitting element to the incident light field area of the light receiving unit. For this reason, as disclosed in Patent Literature 3, the particle detection sensor of related art includes a housing separate from the light emitting element in order to guide the output light from the light emitting element to the incident light field area.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

As the use of particle detection sensors has become widespread, requests have arisen to detect a particle density at a variety of locations. In response to such a request, a compact design is desired of the particle detection sensor. The related art configuration including a housing is not advantageous in achieving the compact and flat design in the particle detection sensor. When the particle detection sensor is manufactured, a housing member needs to be used, leading to involving a mounting operation as an additional work step. This is not appropriate in view of low-cost design.

The present invention has been developed in view of the above-described problem and it is an object to provide a compact and flat designed particle detection sensor that is manufacturable at low cost.

Solution to Problem

(1) The present invention in an aspect relates to a particle detection sensor that includes a light emitting element that outputs light, a light receiving element that detects scattered light when a particle within an incident light field area is irradiated with the output light, a light transmissive resin that encapsulates the light emitting element and the light receiving element, and a reflective surface that is formed on the light transmissive resin and reflects the output light radiated from the light emitting element toward to the incident light field area.
(2) The present invention in another aspect relates to the particle detection sensor according to the aspect (1), wherein a beam diameter of the output light radiated toward the incident light field area is equal to or smaller than a formation width of the formed reflective surface.
(3) The present invention relates in another aspect to the particle detection sensor according to the aspect (2), wherein the reflective surface reflects the output light toward the incident light field area while converging the beam diameter of the output light.
(4) The present invention relates in another aspect to the particle detection sensor according to one of the aspects (1) through (3), wherein an angle between a field direction of the incident light field area and an optical axis direction of the output light reflected from the reflective surface is approximately 90 degrees.
(5) The present invention relates in another aspect to the particle detection sensor according to one of the aspects (1) through (4), wherein a ratio of a full width at half a maximum of an intensity distribution of the output light reflected from the reflective surface to a width at an intensity of 1/e2is larger than a ratio in a Gaussian distribution.
(6) The present invention relates in another aspect to the particle detection sensor according to one of the aspects (1) through (5), wherein the output light is infrared light, the light receiving element is sensitive an infrared wave region, and the light transmissive resin does not transmit visible light but transmits the infrared light.
(7) The present invention relates in another aspect to the particle detection sensor according to one of the aspects (1) through (6), wherein the light emitting element is VCSEL (Vertical Cavity Surface Emitting Laser).
(8) The present invention relates in another aspect to the particle detection sensor according to the aspect (7), wherein the reflective surface is plane.
(9) The present invention relates in another aspect to the particle detection sensor according to the aspect (8), wherein the light emitting element has a plurality of light emitting points that radiate the output light.
(10) The present invention relates in another aspect to the particle detection sensor according to one of the aspects (1) through (9), wherein metallic thin film is vapor-deposited on the reflective surface.
(11) The present invention relates in another aspect to the particle detection sensor according to one of the aspects (1) through (10), wherein a light receiving lens is mounted on the light transmissive resin within the incident light field area.
(12) The present invention relates in another aspect to the particle detection sensor according to one of the aspects (1) through (11), wherein the light emitting element and the light receiving element are respectively encapsulated in resins separated from each other.
(13) The present invention relates in another aspect to the particle detection sensor according to one of the aspects (1) through (12), wherein light shielding resin is applied in a portion excluding the incident light field area.
(14) The present invention relates in another aspect to the particle detection sensor according to one of the aspects (1) through (12), wherein a metal shield is arranged in a portion excluding the incident light field area.
(15) The present invention relates to a particle detection apparatus including the particle detection sensor according to one of the aspects (1) through (14), and a housing in which the particle detection sensor is arranged, wherein a fan that takes in the particle is arranged within the housing.

Advantageous Effects of Invention

According to the present invention, the particle detection sensor that implements a compact and flat design and is manufacturable at low cost is provided.

DESCRIPTION OF EMBODIMENTS

First Embodiment

Embodiments of the present invention are described in detail with reference to the drawings.

(Configuration Example of Particle Detection Sensor1)

FIG. 1is a schematic cross-sectional view of a basic configuration of a particle detection sensor1of a first embodiment.FIG. 2is a schematic view illustrating a top surface of the basic configuration of the particle detection sensor1illustrated inFIG. 1.FIG. 3is a schematic perspective view illustrating the basic configuration of the particle detection sensor1inFIG. 1.

In the particle detection sensor1, a light emitting element3and a light receiving element6are die-bonded onto the same substrate2and are electrically connected to the substrate2via wire bonding. The light receiving element6and a light emitting element3are encapsulated in a single light transmissive resin5. A reflective surface7is formed on an outer surface of the light transmissive resin5and faces in a direction in which output light8is radiated from the light emitting element3. The reflective surface7reflects the output light8toward an incident light field area (detection region)10of the light receiving element6.

The reflective surface7serves as the outer surface of the light transmissive resin5and has desirably a curved surface as illustrated inFIG. 3such that the output light8is converged at a beam convergence location12. Referring toFIG. 1, the output light8of the light emitting element3is reflected from the reflective surface7and converged in beam diameter within the incident light field area10of the light receiving element6. When a particle11passes across the beam, scattered light13from the particle11enters the light receiving element6and a particle detection sensor1outputs a detection signal responsive to the scattered light13. The operation of the particle detection sensor1is described later.

In this configuration, the output light8from the light emitting element3is guided to the incident light field area10in a manner free from the separate arrangement of a housing and a lens as in the related art. When the light emitting element3and the light receiving element6are resin-encapsulated in the light transmissive resin5, an optical structure is defined at the same time.

Since this arrangement is free from the housing that is needed in the particle detection sensor of the related art, the compact and flat design is incorporated in the particle detection sensor1. Since this arrangement is also free from the mounting of the housing, materials are reduced and a mounting operation to mount the materials is eliminated. For this reason, a lower-cost particle detection sensor1is thus implemented.

In the configuration, the output light8from the light emitting element3is reflected from the reflective surface7and the output light8that is converged in beam diameter is radiated onto the incident light field area10of the light receiving element6. At this phase, the width of the output light8radiated onto the incident light field area10is desirably not in excess of a formation width of the reflective surface7. This eliminates the need for the output light8to detect the particle11in a space above the particle detection sensor1(namely, above the top surface of the light transmissive resin5). For this reason, a flat design is incorporated in the particle detection sensor1.

Since the output light8is guided to be close to the receiving surface of the light receiving element6within the incident light field area10of the light receiving element6, the intensity of the scattered light13incident on the light receiving element6is increased. The particle detection sensor1capable of detecting a more stable signal is thus implemented.

In accordance with the configuration, the scattered light13is appropriately caused within the incident light field area10of the light receiving element6by making to be approximately 90 degrees an angle between the field direction of the incident light field area10of the light receiving element6and the optical axis of the output light8reflected from the reflective surface7. Even if any housing to guide the scattered light13is not included, the scattered light13is appropriately detected and a lower-cost the particle detection sensor1is thus implemented.

Since the light emitting element3is outside the incident light field area10of the light receiving element6, the output light8from the light emitting element3is stopped from directly entering the light receiving element6. This eliminates shot noise that may be caused by the output light8that directly enters the light receiving element6. In this configuration, the detection of the particle11may be stabler at an increased S/N ratio.

If the wavelength of the light emitting element3is in the visible light region, the light transmissive resin5is desirably transparent. However, in this case, there is a possibility of an erratic detection if illumination light or disturbance light in the visible light region of the sunlight enters the incident light field area10of the light receiving element6. For this reason, the wavelength of the light emitting element3is set to be in the infrared region and the light transmissive resin5is of a type that does not transmit visible light but transmit infrared light. This attenuates in the incident light level the indoor illumination light or disturbance light in the visible light region of the sunlight entering the light receiving element6. The particle detection sensor1being free from the effect of the disturbance light and providing stable output and is thus implemented.

(Basic Operation of the Particle Detection Sensor1)

Described below are the circuit configuration of the particle detection sensor1, the operation of the particle detection sensor1of the average density method, and the operation of the particle detection sensor1of the particle count method.

FIG. 4is a circuit diagram of the particle detection sensor1. The light emitting element3is connected to the light emitting element driving circuit27and emits light in response to a current generated by the light emitting element driving circuit27. The output light8of the light emitting element3is guided to the detection field region of the light receiving element6. If the particles11is present there, the scattered light13enters the light receiving element6.

The scattered light13having entered the light receiving element6becomes a signal current23. The signal current23is converted into a voltage by the current-to-voltage converter circuit25connected to the light receiving element6, and the voltage is amplified through an amplifier circuit unit26, coupling capacitor28, and amplifier circuit unit26connected as subsequent stages. The amplified voltage is then input to an arithmetic processor29.

In the arithmetic processor29, the scattered light13in the form of voltage is A/D converted by a A/D converter circuit30, the A/D converted signal is arithmetically processed by the arithmetic processing circuit32, the processed signal is then converted into a serial signal by a serial output circuit31, and the serial signal is output as an output of the particle detection sensor1.

(Operation of the Particle Detection Sensor1of the Average Density Method)

FIG. 5illustrates an operation example of an average density method of the particle detection sensor1. Illustrated in the top portion ofFIG. 5is the time-series change of a driving current of the light emitting element3. Illustrated in the bottom ofFIG. 6is an example of an output voltage of an amplifier circuit unit.

Referring to the top portion ofFIG. 5, the light emitting element3is pulse-driven in the average density method. The scattered light13from the particle11is incident on the light receiving element6only during a time period throughout which the light emitting element3emits light. The voltage responsive to the scattered light13is amplified through the amplifier circuit unit26, resulting in the waveform illustrated in the bottom portion ofFIG. 5.

The output voltage of the amplifier circuit unit26is proportional to the scattered light13. Specifically, the output voltage varies in proportion to the density of the particles11. The output voltage of the amplifier circuit unit26is A/D converted by the A/D converter circuit30in the arithmetic processor29at a timing in synchronization with a drive timing of the light emitting element3, the A/D converted voltage is arithmetically processed, and the resulting signal is output as the serial signal.

In the average density method, the scattered light13is received at the light emission timing of the light emitting element3. In this case, if the abundance ratio of the particles11in a space is lower, the particle count varies depending on the light emission timing and the output voltage varies. The output may thus possibly be unstable. To reduce the variations, the output light8of the light emitting element3is desirably radiated in a wider area within the incident light field area10of the light receiving element6such that the scattered light13receives more particles11.

(Operation of the Particle Detection Sensor1in the Particle Count Method)

FIG. 6illustrates an operation example of the particle count method of the particle detection sensor1. Illustrated in the top portion ofFIG. 6is the time-series change of a driving current of the light emitting element3. Illustrated in the bottom ofFIG. 6is an example of the output voltage of the amplifier circuit unit26.

Referring to the top portion ofFIG. 6, the light emitting element3is continuously lit in the particle count method. The scattered light13is incident on the light receiving element6when the particles11pass across the beam of the output light8of the scattered light13. The voltage responsive to the scattered light13is amplified through the amplifier circuit unit26, leading to the waveform illustrated in the bottom portion ofFIG. 6.

The output voltage of the amplifier circuit unit26is periodically A/D converted by the A/D converter circuit30connected as a later stage. When the A/D converted signal above a predetermined threshold voltage comes in, it is determined that the particles11have passed. The arithmetic processor29counts the number of particles per unit time and outputs results as a count or density. It is also possible that the size of the particle11having passed is detected by referring to the magnitude of the peak of the output voltage (peak value) of the amplifier circuit unit26.

Referring toFIG. 6, the peak of the output voltage increases when a larger particle has passed across and the peak of the output voltage decreases when a smaller particle has passed across. The density of particles is found on a per particle size basis in accordance with these pieces of information and has thus a higher accuracy level.

In the particle count method, the scattered light13of a single particles11passing across the output light8of the light emitting element3is detected. The output light8of the light emitting element3is desirably converged to a smaller diameter beam within the incident light field area10of the receiving element6such that the scattered light13is enlarged and stably detected and such that miscounting of particles that may occur with multiple particles11having passed across the beam of the output light8of the light emitting element3is reduced. Since this arrangement increases an intensity per unit volume of the particle11, simultaneous detection of multiple particles11is controlled.

In this configuration, the beam intensity distribution may be optimized in the particle count method when a light beam is formed by reflecting the output light8. Specifically, means is used to derive a beam of an intensity distribution having a central constant intensity portion (a region of a flat beam intensity) with narrower skirt portions on both sides of the central constant intensity portion from an intensity distribution of a typical Gaussian distribution having broad skirt portions (the means is hereinafter referred to as beam intensity distribution flattening means).

The means is implemented by optically optimizing the shape of the reflective surface7. The advantage achieved by flattening the beam intensity distribution is described with reference toFIGS. 7 and 8.

FIG. 7illustrates an operation example when the intensity distribution of the beam of the light emitting element3is a typical Gaussian distribution.FIG. 8illustrates an operation example when the beam of the light emitting element3is formed through a beam intensity distribution flattening function of the configuration.

FIG. 7(a)andFIG. 8(a)illustrate the beam intensity distributions,FIG. 7(b)andFIG. 8(b)illustrate how particles A, B, and C pass across the beam, andFIG. 7(c)andFIG. 8(c)illustrate output waveforms that are generated in the output of the amplifier circuit when the particles pass across the beam.

FIG. 7(a)illustrates the typical Gaussian distribution. The Gaussian distribution has a shape having a peak intensity and skirt portions with intensity decreasing on both sides of the peak intensity. If a full width at half the maximum of the distribution is compared with a width at 1/e2intensity, the width at 1/e2intensity is larger. In other words, the ratio of the full width at half the maximum to the width at 1/e2intensity is smaller.

When the particles A, B, and C sequentially pass across the beam as illustrated inFIG. 7(b), a signal inFIG. 7(c)is generated in the output of the amplifier circuit unit.

When the particles A, B, and C sequentially pass across the beam having the typical intensity distribution, the resulting signal varies in magnitude in accordance with the passage location of the particle even though the particles of the same size pass across the beam. For example, if a threshold voltage is set up as illustrated inFIG. 7(c), the pass of the particle B is not counted. If the intensity distribution of the beam is deviated, such a problem is created.

FIG. 8(a)illustrates the intensity distribution of the beam when the intensity distribution of the configuration is flattened. The distribution has a constant intensity portion at the peak of the distribution and narrower skirt portions on both sides. The difference between the full width at half the maximum and the width at 1/e2intensity becomes smaller and the ratio of the full width at half the maximum to the width at 1/e2intensity is larger than that in the Gaussian distribution.

FIG. 8(c)illustrates the output waveform. The output signals are uniform in intensity in comparison with the typical beam intensity distribution inFIG. 7and the pass of the particle B is thus properly counted.

The use of the beam intensity distribution flattening means in this configuration controls instability caused by the intensity distribution of the beam. The particle detection sensor1capable of stable detection is thus provided.

The embodiment described above provides the configuration appropriate for the particle count method. Specifically, the configuration is provided by converging the beam diameter to be as small as possible within the incident light field area10of the light receiving element6. The configuration appropriate for the average density method may be easily optimized by modifying the shape of the reflective surface7such that the output light8of the light emitting element3is radiated in a wider area within the incident light field area10of the light receiving element6.

FIG. 9schematically illustrates the configuration of a particle detection sensor1a(modification 1) when the reflective surface7sets the output light8ato be parallel such that the output light8of the light emitting element3is radiated widely within the incident light field area10of the light receiving element6.FIG. 10schematically illustrates the configuration of a particle detection sensor1b(modification 2) when the reflective surface7moderately widens the output light8bto within a detection region of the light receiving element6such that the output light8of the light emitting element3is radiated even more widely.

The modification provides the configuration in which the reflective surface7makes the output light8aparallel or the configuration in which the reflective surface7moderately widens the output light8bto within the detection region of the light receiving element6. The particle detection sensor1aor1balso appropriate for the average density method is easily implemented.

The light emitting element3may be LED (light emitting diode) or VCSEL. As described above with reference to the embodiment, the output light8output from the light emitting element3needs to be converged more in beam diameter and increased in intensity in order to optimize the configuration for the particle count method.

FIG. 11is a conceptual diagram of the configuration of a particle detection sensor1cwhen the light emitting element3ais VCSEL. For VCSEL, an output angle may be converged more. For this reason, the reflective surface7is free from converging the beam diameter of output light8cand is thus free a complex configuration such as a toroidal surface. A plane reflective surface7athat is an easily formed surface is simply arranged on the light transmissive resin5. The particle detection sensor1cis thus easily produced.

In comparison with LED, VCSEL has typically light emission power higher than LED and achieves a smaller output angle, thereby converging a beam to a smaller diameter. Since the output intensity per unit volume is increased in comparison with LED, the light emitting element3ais desirably VCSEL. The intensity of the scattered light13from the particles11is thus increased and the particle detection sensor1cproviding stable output is thus implemented.

FIG. 12is a conceptual diagram of the configuration in which a light emitting element3bas VCSEL has multiple light emitting points. Since VCSEL has a smaller output angle as described above, the reflective surface7amay be plane. If the light emitting element3bhaving multiple emitting points is used with the plane reflective surface7a, multiple beams of output light8dmay be easily radiated to the incident light field area10.

By using the multiple beams of the output light8dradiated to the incident light field area10, the output count of signal is increased. A particle detection sensor1dcapable of stabler detection is thus implemented.

The advantage of using the multiple beams of the output light8d(hereinafter also simply referred to as beam) is described below.FIG. 13illustrates an operation when a single beam is used, andFIG. 14illustrates an operation when two beams are used.FIG. 13(a)andFIG. 14(a)illustrate how the particles11passing across the beam andFIG. 13(b)andFIG. 14(b)illustrate output signals of the amplifier circuit unit26in respective operations.

A comparison ofFIG. 13(b)toFIG. 14(b)reveals that the use of multiple beams increases the number of output signals of the amplifier circuit unit26. In this way, the particle detection sensor1dcapable of stable detection is implemented.

A metallic thin film is vapor-deposited on the reflective surface7of the embodiment to form the vapor deposition surface15. Reflectance of the reflective surface7is thus increased. The intensity of the scattered light13of the particles11is also increased. A particle detection sensor1eproviding stable output is thus implemented.

FIG. 15schematically illustrates the cross-section of the basic configuration of the particle detection sensor1e. The particle detection sensor1eincludes a light receiving lens14that is on the light transmissive resin5within the incident light field area10of the light receiving element6and receives the scattered light13from the particle11.

The scattered light13from the particle11is efficiently collected by arranging the light receiving lens14. Since signal intensity thus increases, the particle detection sensor1eproviding stable output is implemented. Since a light receiving lens separate from the light receiving element6is not needed, the compact and flat designed particle detection sensor1eis implemented. Since the particle detection sensor1eis free from mounting the light receiving lens at the manufacturing phase, the particle detection sensor1eis manufactured at a lower cost.

When the light receiving element6and the light emitting element3are encapsulated, the light receiving element6and the light receiving element6may be encapsulated in separate light transmissive resins5.

FIG. 16schematically illustrates the cross-section of the basic configuration of a particle detection sensor1fthat includes light transmissive resin5aand light transmissive resin5bseparated from each other. Referring toFIG. 16, the particle detection sensor1freduces stray light16(seeFIG. 15) that may enter the light receiving element6from the light emitting element3after being reflected within the light transmissive resin5. The generation of a current caused by factors other than the scattered light13is reduced and shot noise caused in the light receiving element6in response to the entrance of the stray light16is reduced. S/N ratio is thus increased, and the particle detection sensor1fcapable of stabler detection is implemented.

In the modification 6, a light shielding resin18may be arranged, around the light transmissive resin5bencapsulating the light receiving element6, in an area that does not block the incident light field area10of the light receiving element6.

FIG. 17schematically illustrates the cross-section of the basic configuration of a particle detection sensor1gincluding the light shielding resin18. Referring toFIG. 17, the arrangement of the light shielding resin18further reduces the stray light16from the light emitting element3. The shot noise generated in the light receiving element6by the stray light16is further reduced. In this way, the particle detection sensor1gcapable of stabler detection is implemented.

Further in the modification 6, a metal shield19may be arranged, around the light transmissive resin5bencapsulating the light receiving element6, in an area that does not block the incident light field area10of the light receiving element6.

FIG. 18schematically illustrates the cross-section of the basic configuration of a particle detection sensor1hincluding the metal shield19. Referring toFIG. 18, the arrangement of the metal shield19not only reduces further the stray light16from the light emitting element3but also reduces external noise, such as electromagnetic noise entering the light receiving element6and the substrate2that the light receiving element6is connected. In this way, the particle detection sensor1hcapable of stabler detection is implemented.

Second Embodiment

A second embodiment of the present invention is described below. For convenience of explanation, elements identical to those described with reference to the first embodiment are designated with the same reference numerals and the discussion thereof is not repeated herein.

In accordance with the second, an apparatus50including the particle detection sensor1described with reference to the first embodiment is described blow. The apparatus50of the second embodiment desirably includes the particle detection sensor1and a fan mounted inside the apparatus50to take in the particles11. The apparatus50has a compact and flat design and is capable of stable detection.

(Configuration Example of the Apparatus50)

FIG. 19is a schematic diagram of the apparatus50of the second embodiment of the present invention.FIG. 20is a sectional view taken along line A-A′ in the schematic diagram inFIG. 19.

The apparatus50includes a housing51having an intake hole52and exhaust holes53. The particle detection sensor1is mounted in the housing51and a fan55is mounted in the vicinity of the exhaust holes53. The housing51includes a mounting space56. A variety of apparatuses including an air cleaner and an ion generator may be mounted in the mounting space56in accordance with the applications of the apparatus50.

The apparatus50takes in the particles11via the intake hole52with the fan55rotating and then discharges the particles11. The particle detection sensor1is mounted in a manner such the incident light field area10of the light receiving element6is aligned with a location where the particles11from the intake hole52pass. In this configuration, the particles11taken in via the intake hole52by the fan55are detected by the particle detection sensor1.

Since the beam diameter of the output light8of the light emitting element3is set to be smaller than the formation width of the reflective surface7in the particle detection sensor1, a detection location of the particles11is lowered. Also, since the particle detection sensor1is free from the mounting of the housing that guides the output light8, a compact apparatus50is implemented.

In accordance with the configuration, the compact and flat designed device50is capable of detecting the particles11. In the configuration, the mounting location of the fan55is not limited to any particular location. As long as the configuration takes in the particles11via the intake hole52, the location of the fan55does not matter. As long as the particle detection sensor1is at the location where the particle11passes the incident light field10of the light receiving element6, the location of the particle detection sensor1does not matter. In the configuration, the particles11are taken in via the intake hole52. If the fan55is mounted in an opposite direction, the flow of the particles11may be reversed in direction. More specifically, the particles11are taken in via the exhaust holes53and discharged via the intake hole52. As long as the configuration allows the particles11to pass across the incident light field area10of the light receiving element6, the direction of the flow of the particles11does not matter.

Modifications

A particle detection apparatus50amay be constructed by mounting the particle detection sensor1and the fan55in a compact housing51awithout the mounting space56.FIG. 21illustrates the particle detection apparatus50aincluding the particle detection sensor1and the fan55.FIG. 22illustrates a cross-section of the particle detection apparatus50ataken along line A-A′.

The housing51aincludes the intake hole52and the exhaust holes53. The fan55is mounted inside the housing51a. With the fan55rotating, the particles11are taken in via the intake hole52and discharged via the exhaust holes53.

In the particle detection apparatus50aas well, the particle detection sensor1is mounted at the location where the particles11from the intake hole52pass. In this configuration, the particle detection sensor1may detect the particles11that the fan55have taken in via the intake hole52.

In accordance with the modification, the compact and flat designed particle detection apparatus50acapable of taking in the particles11from outside via the fan55may be implemented. The particle detection sensor1is thus easily mounted on the particle detection apparatus50aand the compact and flat designed particle detection apparatus50ais capable of detecting the particles11.

In the particle detection apparatus50a, as described above, the locations of the particle detection sensor1and the fan55and the direction of the particles11do not matter.

CONCLUSION

The particle detection sensor of a first aspect of the present invention includes a light emitting element that outputs light, a light receiving element that detects scattered light caused when a particle within an incident light field area is irradiated with the output light, a light transmissive resin that encapsulates the light emitting element and the light receiving element, and a reflective surface that is formed on the light transmissive resin and reflects the output light radiated from the light emitting element toward the incident light field area.

Since the reflective surface is formed on the light transmissive resin in this configuration, the output light from the light emitting element is guided to the light receiving field without separately arranging the housing or lens. The particle detection sensor that is compact and flat designed and manufacturable at lower cost is thus implemented.

In the particle detection sensor in a second aspect of the present invention in view of the first aspect, a beam diameter of the output light radiated toward the incident light field area is equal to or smaller than a formation width of the formed reflective surface.

Since the widening of the beam diameter of the output light radiated toward the incident light field area is controlled in this configuration, a flat design may be implemented in the particle detection sensor.

In the particle detection sensor in a third aspect of the present invention in view of the second aspect, the reflective surface reflects the output light toward the incident light field area while converging the beam diameter of the output light.

In this configuration described above, the convergence location of the output light is set to be closer to the light incident surface of the light receiving element, and the intensity of the scattered light from the particle entering the light receiving element is thus increased. Stabler detection of the particle is thus possible.

In the particle detection sensor in a fourth aspect of the present invention in view of the first aspect, an angle between a field direction of the incident light field area and an optical axis direction of the output light reflected from the reflective surface is approximately 90 degrees.

In the configuration described above, the light receiving element may appropriately receive the scattered light even without the housing. This configuration also controls stray light that results from the output light directly entering the light receiving element from the light emitting element. The shot noise caused by the stray light is eliminated. Stabler detection with increased S/N (signal noise ratio) is possible.

In the particle detection sensor in a fifth aspect of the present invention in view of the first aspect, a ratio of a full width at half a maximum of an intensity distribution of the output light reflected from the reflective surface to a width at an intensity of 1/e2is larger than a ratio in a Gaussian distribution.

In the configuration described above, the intensity distribution of the output light formed on the reflective surface has a constant beam intensity portion at a center area with narrow skirt portions on both sides of the intensity distribution and is different from the Gaussian distribution that has wider spread skirt portions. This configuration reduces in the signal intensity of the light receiving element variations that are generated depending on the location of the particle that passes across the beam convergence location of the output light. Stabler detection of the particle is thus possible.

In the particle detection sensor in a sixth aspect of the present invention in view of the first through fifth aspects, the output light is infrared light, the light receiving element is sensitive in an infrared wave region, and the light transmissive resin does not transmit visible light but transmits the infrared light.

Since the configuration described above eliminates the effect of disturbance light, such as indoor light and sunlight, stabler detection of the particle is possible.

In the particle detection sensor in a seventh aspect of the present invention in view of the first through fifth aspects, the light emitting element is VCSEL (Vertical Cavity Surface Emitting LASER).

In the configuration described above, the beam diameter of the output light is converged to a smaller value. The intensity of the scattered light from the particle is thus increased. Stabler detection of the particle is possible and the output of the particle detection sensor is thus stabilized.

In the particle detection sensor in an eighth aspect of the present invention in view of the seventh aspect, the reflective surface is plane.

In the configuration described above, the light emitting element as VCSEL providing a narrow directional angle of the output light is thus free from forming a complicated reflective surface like a toroidal surface. The reflective surface may be formed of a simply formed plane and the particle detection sensor may be easily manufactured.

In the particle detection sensor in a ninth aspect of the present invention in view of the eight aspect, the light emitting element has multiple light emitting points that radiate the output light.

In the configuration described above, the reflective surface is plane. By arranging the light emitting element having multiple light emitting points, the multiple beams of the output light are appropriately radiated to the incident light field area of the light receiving element. Since the frequency of passes of particles that passes across the output light increases, stabler detection of the particle is possible.

In the particle detection sensor in a tenth aspect of the present invention in view of the first through fifth aspects, metallic thin film is vapor-deposited on the reflective surface.

In the configuration described above, the reflectance of the reflective surface increases and the intensity of the output light radiated toward the incident light field area is increased. The intensity of the scattered light from the particles increases, leading to stabler detection.

In the particle detection sensor in an eleventh aspect of the present invention in view of the first through fifth aspects, a light receiving lens is mounted on the light transmissive resin within the incident light field area.

In the configuration described above, the light collection efficiency of the scattered light is increased without separately arranging a lens and the intensity of the scattered light is increased. The particle detection sensor that is low-cost and compact designed is capable of stable detection.

In the particle detection sensor in a twelfth aspect of the present invention in view of the first through fifth aspects, the light emitting element and the light receiving element are respectively encapsulated in separated resins.

Since the configuration described above reduces the stray light that enters from the light emitting element to the light receiving element and that does not contribute to the detection of the particles by the light receiving element, the shot noise created by the stray light is reduced. The light receiving element detects the particles more stably, thereby stabilizing the output of the particle detection sensor.

In the particle detection sensor in a thirteenth aspect of the present invention in view of the twelfth aspect, light shielding resin is applied in a portion excluding the incident light field area.

In the configuration described above, the stray light that does not contribute to the detection of the particles by the light receiving element is further reduced. The output of the particle detection sensor is stabilized.

In the particle detection sensor in a fourteenth aspect of the present invention in view of the first through fifth aspects, a metal shield is arranged in a portion excluding the incident light field area.

The configuration described above reduces the stray light that enters from the light emitting element to the light receiving element and that does not contribute to the detection of the particles by the light receiving element and controls the inflow of electromagnetic noise from outside. This configuration controls abnormal detection in response to an external factor, thereby stabilizing the output of the particle detection sensor.

In the particle detection sensor in a fifteenth aspect of the present invention in view of the first through fifth aspects, a particle detection apparatus includes the particle detection sensor according to one of the first through fifth aspects, a housing in which the particle detection sensor is arranged, and a fan that takes in the particle is arranged within the housing.

In the configuration described above, the particle detection apparatus that is compact and flat designed and manufacturable at low cost is implemented.

The present invention is not limited to the embodiments described above and a variety of modifications may be implemented within the scope defined in the claims. An embodiment obtained by appropriately combining technical means disclosed in the different embodiments may fall within the technical scope of the present invention. A new technical feature may be provided by combining the technical means disclosed in the embodiments.

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