Patent Description:
Smoke detectors play an important role in identifying smoke, ideally alarming as early as possible in the course of fire. Smoke detectors can use one or more sources of light as the source of the smoke detection scheme, and can use multiple wavelengths of light to help improve detection performance. For example, dual wavelengths of light, one being infrared and the other being visible, can be used in a smoke detector. A chamberless detector can provide improved sensing performance over designs that utilize a chamber, therefore resulting in the popularity of the chamberless design in high-performance applications. A chamberless detector can be referred to as a next-generation point sensor, because of its advanced design and its use in detecting smoke at a particular point of installation. A chamberless detector can also be referred to as a chamberless point sensor.

A commercial aircraft is a non-limiting example of a high-performance application where a chamberless point sensor utilizing multiple wavelengths of light can be used. There are many factors that contribute to the need for a high-performance chamberless detector, with non-limiting examples including the desire to discern between steam or dust and the smoke particles from a fire, the desire to avoid nuisance alarms from food preparation, and the desire to detect smoke particles that can be produced from smoldering synthetic materials, often resulting in particle sizes smaller than <NUM> (microns) in diameter. Additionally, chamberless detectors utilizing multiple wavelengths of light can be used to monitor indoor air quality, where the presence of fine particles (particle sizes ≤ <NUM>) and coarse particles (particle sizes ≤ <NUM>) can be important.

A protective cover can be positioned on a chamberless detector to overcome some of the problems that have been associated with chamberless detectors, for example, there not being a well-protected volume that is free from interference or tampering. Typical examples of a protective cover can include a clear or opaque cover, which can also include apertures. While a protective cover can be helpful in reducing interference from ambient light sources emanating from the surrounding environment, there can still be problems with the transmission, reflection, and/or absorption of light by a protective cover.

<CIT>, <CIT> and <CIT> relate to scattered light detectors.

According to a first aspect of the present invention, there is provided a covered chamberless particulate detector as claimed in claim <NUM>.

According to a second aspect of the present invention, there is provided a method of using a covered chamberless particulate detector as claimed in claim <NUM>.

The present disclosure provides an optically enhanced protective cover for a chamberless point sensor. A chamberless point sensor can also be referred to as a next generation chamberless point sensor, a chamberless point sensor and monitor, a covered chamberless particulate detector, or a chamberless detector for short. As used in this disclosure, "particulate" will be used to describe all airborne particles that are detectable, which includes smoke. Moreover, the descriptions provided herein refer to the detection of airborne particulates by the interaction of light and the scattering of light to the optical detection circuitry of the chamberless detector.

During operation of a chamberless detector, one or more sources of light having one or more wavelengths illuminate one or more volumes in the vicinity of the chamberless detector. Airborne particulates in an illuminated volume can scatter light and/or fluoresce, which can be detected by the chamberless detector. The operation of a chamberless detector can be referred to as monitoring, whereby the chamberless detector monitors for sensing events. A sensing event is when an electrical response occurs within the detection circuitry as a result of a photo interaction. During the monitoring process, particulate levels can simply be displayed or recorded for later use by a user. Additional responses can also occur if various threshold criteria are met. Non-limiting examples of additional responses can include activating an alarm, triggering other system responses, and initiating protective actions.

Generally speaking, particulates, including smoke and other airborne particles, can vary in size depending on several factors including without limitation the materials that are smoldering, burning, or combusting, the temperature of the process, the stage of the process, and the concentration of oxygen and other gasses at the point of the process. The process can be combustion, pre-combustion, or any other process that produces airborne particulates. Moreover, processes other than combustion can cause airborne particulates. For example, chemical reactions can evolve airborne particulates. Particulates can generally range in size from <NUM> - <NUM> in diameter, however they can be smaller in size than <NUM> in diameter, or larger in size than <NUM> in diameter. Some particulates can be up to <NUM> in diameter. In some embodiments, covered point sensor <NUM> can monitor for indoor air quality, while being able to discriminate between fine particles (particle sizes ≤ <NUM>) and coarse particles (particle sizes ≤ <NUM>). Moreover, some particulates can be airborne biological agents. Airborne biological agents can also be referred to as "biologics". As used in this disclosure, "particulates" and "airborne particulates" refer to particulate matter from any source that exists in the void space in and around the covered point sensor, without limiting to a presence in air. For example, the covered point sensor of the present disclosure can detect particulates that exist in air, rarefied air, a vacuum, or within any other fluid whether liquid or gaseous.

<FIG> is a side view of a chamberless particulate detector with a protective cover, or covered point sensor. Shown in <FIG> are covered point sensor <NUM>, chamberless detector <NUM>, first optical emitter <NUM>, second optical emitter <NUM>, first optical detector <NUM>, second optical detector <NUM>, inside region <NUM>, protective cover <NUM>, outside region <NUM>, second emitting cone <NUM>, second emitter axis E2, second emitter cone half angle θE2, first receiving cone <NUM>, first receiving cone axis R1, first receiving cone half angle θR1, and first sensing volume <NUM>.

As will be described later, first optical emitter <NUM> also has a first emitting cone (not shown), and second optical detector <NUM> also has an associated second receiving cone (not shown). Accordingly, multiple combinations involving first optical emitter <NUM>, second optical emitter <NUM>, first optical detector <NUM>, and second optical detector <NUM> can be illustrated to depict the operation of covered point sensor <NUM>. For clarity of illustration, <FIG> each depict a single combination.

In the illustrated embodiment, covered point sensor <NUM> has a substantially hemispherical geometry, being comprised of chamberless detector <NUM> and protective cover <NUM>. Chamberless detector <NUM> has a substantially flat profile as illustrated in the side view of <FIG>. In the illustrated embodiment, chamberless detector <NUM> has a circular or disk-like shape viewed from the top or in perspective (not shown). In other embodiments, chamberless detector <NUM> can have other geometries.

In the illustrated embodiment, chamberless detector <NUM> includes first optical emitter <NUM> and second optical emitter <NUM>. First optical emitter <NUM> and second optical emitter <NUM> produce and emit light having a wavelength or wavelengths that are employed by chamberless detector <NUM>. In the illustrated embodiment, first optical emitter <NUM> and second optical emitter <NUM> each produce a peak wavelength of light. In an embodiment, first optical emitter <NUM> can produce an infrared light and second optical emitter <NUM> can produce a blue light. The infrared light can have a peak wavelength between <NUM> - <NUM>, but in some embodiments may be outside of this range. The blue light can have a peak wavelength between <NUM> - <NUM>, but in some embodiments may be outside of this range. In some embodiments, first optical emitter <NUM> and second optical emitter <NUM> can produce wavelengths of light in the infrared, visible, and ultraviolet bands of light. In these other embodiments, first optical emitter <NUM> and second optical emitter <NUM> can produce a wide range of wavelengths of light. For example, in an embodiment, first optical emitter <NUM> and/or second optical emitter <NUM> can produce violet or ultraviolet light having a wavelength shorter than <NUM>. In another embodiment, first optical emitter <NUM> and/or second optical emitter <NUM> can produce visible light having a wavelength between <NUM> - <NUM>. In yet other embodiments, first optical emitter <NUM> and/or second optical emitter <NUM> can produce infrared light having a wavelength greater than <NUM>. In some embodiments, first optical emitter <NUM> and second optical emitter <NUM> can produce the same wavelength of light. In some embodiments, only first optical emitter <NUM> can be used. In these other embodiments, first optical emitter <NUM> can be configured to emit multiple wavelengths of light. In yet other embodiments, a third optical emitter (not shown) can be used.

In the illustrated embodiment, first optical emitter <NUM> and second optical emitter <NUM> are light emitting diodes (LEDs). In other embodiments, first optical emitter <NUM> and/or second optical emitter <NUM> can produce light by any suitable means. For example, in those other embodiments, first optical emitter <NUM> and/or second optical emitter <NUM> can be a laser diode. In some embodiments, first optical emitter <NUM> and second optical emitter <NUM> can be combined in the same device.

Referring again to <FIG>, chamberless detector <NUM> includes first optical detector <NUM> and second optical detector <NUM>. In the illustrated embodiment, photoelectric indication of light is provided by photo diodes. In other embodiments, first optical detector <NUM> and/or second optical detector <NUM> can be any suitable device that produces a photoelectric indication of light. As used in this disclosure, a photoelectric indication of light is a response to a sensing event, whereby a photon or photons of light at a particular wavelength or within a particular wavelength band, excite an optical detector, thereby producing an electrical signal as an output. In other embodiments, only first optical sensor <NUM> can be used. In other embodiments, more than two detectors (not shown) can be used. In some embodiments, first optical detector <NUM> and second optical detector <NUM> can be the same style of photo detector. In other embodiments, first optical detector <NUM> and second optical detector <NUM> can be different styles of photo detectors. In some embodiments, first optical detector <NUM> and second optical detector <NUM> can be combined in the same device.

In the illustrated embodiment, first optical detector <NUM> is responsive to a first wavelength of light, and second optical detector <NUM> is responsive to a second wavelength of light. The first wavelength of light can define a first wavelength band, and the second wavelength can define a second wavelength band. In the illustrated embodiment, the first and second wavelengths are different from each other. In other embodiments, the first and second wavelengths can be the same.

Referring again to <FIG>, covered point sensor <NUM> includes protective cover <NUM>. Protective cover <NUM> defines inside region <NUM> and outside region <NUM>. In the illustrated embodiment, protective cover <NUM> has a semi-circular shape as viewed from the side. Protective cover <NUM> can be referred to as an envelope, defining an inside region and an outside region of protective cover <NUM>. In the illustrated embodiment, protective cover <NUM> has a diameter of about <NUM> (<NUM> inches) in the region near where protective cover <NUM> attaches to chamberless detector <NUM>. In other embodiments, protective cover <NUM> can have a diameter between <NUM> - <NUM> (<NUM> - <NUM> inches). In yet other embodiments, protective cover <NUM> can have a diameter of less than <NUM> (<NUM> inches), or greater than <NUM> (<NUM> inches). In the illustrated embodiment, protective cover <NUM> has a generally hemispherical shape, in which the height of protective cover <NUM> is approximately half the diameter. In other embodiments, the geometry of protective cover <NUM> can be substantially different from hemispherical. For example, in an embodiment, protective cover <NUM> can be squat in its geometry, with a height less than approximately half the diameter. In another embodiment, the height of protective cover <NUM> can be significantly less than approximately half the diameter. Alternatively, in yet other embodiments, protective cover <NUM> can have a bulbous geometry, in which the height of protective cover <NUM> is greater than approximately half the diameter. In other embodiments, the cover can be cylindrical, square, or rectangular in shape, with these being non-limiting examples of possible geometries of protective cover <NUM>. It will be appreciated that covered point sensor <NUM> can provide additional benefits including but not limited to reduction of transport time for particles to reach the particle detecting elements to enable faster alerting, alarm, and response by users and systems; improved sensitivity; improved manufacturability; negligible directionality; ease of maintenance; and enhanced aesthetic appearance.

In the illustrated embodiment, protective cover <NUM> is a continuous surface and covered point sensor <NUM> includes apertures (not shown) which can allow fluid communication between inside region <NUM> and outside region <NUM>. As will be discussed later, covered point sensor can detect airborne particulates that are within inside region <NUM>, outside region <NUM>, or both. Generally, airborne particulates are generated or introduced in the environment exterior to covered point sensor <NUM>. Therefore, airborne particulates first occur in outside region <NUM>. Accordingly, fluid communication between inside region <NUM> an outside region <NUM> can allow airborne particulates to migrate from outside region <NUM> to inside region <NUM>. In other embodiments, covered point sensor <NUM> can include vents, ports, or other mechanisms that permit fluid communication between inside region <NUM> and outside region <NUM>. As used in this disclosure, protective cover <NUM> is assumed to be a continuous surface which possesses optical properties thereof. Any reference to the transmission of light through protective cover <NUM> therefore refers to the transmission of light through the material from which protective cover <NUM> is made.

As noted earlier, in the embodiment depicted in <FIG>, only second emitter cone <NUM> is shown for ease of illustration but it is to be appreciated that first optical emitter <NUM> also has an associated first emitter cone. Similarly, only first receiving cone <NUM> is shown for ease of illustration but it is to be appreciated that second optical detector <NUM> also has an associated second receiving cone. During operation of covered point sensor <NUM>, second optical emitter <NUM> emits light in second emitter cone <NUM> having second emitter axis E2. In a particular embodiment, second emitter axis azimuthal angle φE2 (not shown) can be measured relative to a datum on chamberless detector <NUM>. Second emitter cone half angle θE2 refers to the half-angle width of the expanding three-dimensional second emitter cone <NUM> that is emitted from second optical emitter <NUM>. Second emitter cone half angle θE2 is measured at the half-intensity point of optical energy being radiated from second optical emitter <NUM>. This can also be referred to as the full width half-maximum (FWHM).

During operation of covered point sensor <NUM>, first optical detector <NUM> senses light in first receiving cone <NUM> having first receiving cone axis R1. First receiving cone axis R1 has first receiving cone axis azimuthal angle φR1 (not shown) and first receiving cone half angle θR1. In a particular embodiment, first receiving cone axis azimuthal angle φR1 can be measured relative to a datum on chamberless detector <NUM>. First receiving cone half angle θR1 refers to the half angle width of the expanding three-dimensional cone of visibility that is detectible by first optical detector <NUM>. First receiving cone half angle θR1 is measured at the half-intensity point of optical energy being detected by first optical detector <NUM>. This can also be referred to as FWHM.

In the illustrated embodiment of <FIG>, protective cover <NUM> is optically transparent to some or all wavelengths of light that are produced by second optical emitter <NUM> and received by first optical detector <NUM>. In one embodiment, protective cover <NUM> is comprised of transparent acrylic. In other embodiments, protective cover <NUM> can be any material that is transparent or substantially transparent to ambient light such as glass or resin. Accordingly, in the embodiment shown in <FIG>, second emitting cone <NUM> is projected through inside region <NUM> and through protective cover <NUM> to outside region <NUM>, and first receiving cone <NUM> extends through inside region <NUM> and through protective cover <NUM> to outside region <NUM>. First sensing volume <NUM> is defined by the spatial overlap of second emitter cone <NUM> and first receiving cone <NUM>. Accordingly, first sensing volume <NUM> is defined both within inside region <NUM> and within outside region <NUM>. As can be seen in <FIG>, the first sensing volume <NUM> is dependent on second emitter axis E2, second emitter cone half angle θE2, first receiving cone axis R1, and first receiving cone half angle θR1.

<FIG> is a side view of a second mode of covered point sensor <NUM>. Shown in <FIG> are covered point sensor <NUM>, chamberless detector <NUM>, first optical emitter <NUM>, second optical emitter <NUM>, first optical detector <NUM>, second optical detector <NUM>, inside region <NUM>, protective cover <NUM>, outside region <NUM>, first emitting cone <NUM>, first emitter axis E1, first emitter cone half angle θE1, first receiving cone <NUM>, first receiving cone axis R1, first receiving cone half angle θR1, and second sensing volume <NUM>. The description of covered point sensor <NUM> is similar to as in <FIG>, with the difference in <FIG> being that first emitting cone <NUM> being radiated from first optical emitter <NUM> is illustrated, and is defined by first emitter axis E1. First emitter axis E1 has first emitter axis azimuthal angle φE1 (not shown) and first emitter cone half angle θE1. In a particular embodiment, first emitter axis E1 has first emitter axis azimuthal angle φE1 that can be measured relative to a datum on chamberless detector <NUM>. In the illustrated embodiment, protective cover <NUM> is optically transparent to some or all wavelengths of light that are produced by first optical emitter <NUM> and received by first optical detector <NUM>. Accordingly, second emitting cone <NUM> is projected through inside region <NUM> and through protective cover <NUM> to outside region <NUM>, and first receiving cone <NUM> extends through inside region <NUM> and through protective cover <NUM> to outside region <NUM>. Second sensing volume <NUM> is defined by the spatial overlap of first emitter cone <NUM> and first receiving cone <NUM>. In the illustrated embodiment, second sensing volume <NUM> is defined entirely within inside region <NUM>. As can be seen in <FIG>, the definition of second sensing volume <NUM> is dependent on first emitter axis E1, first emitter cone half angle θE1, first receiving cone axis R1, and first receiving cone half angle θR1.

<FIG> is a side view of a third mode of covered point sensor <NUM>. Shown in <FIG> are covered point sensor <NUM>, chamberless detector <NUM>, first optical emitter <NUM>, second optical emitter <NUM>, first optical detector <NUM>, second optical detector <NUM>, inside region <NUM>, protective cover <NUM>, outside region <NUM>, first emitting cone <NUM>, first emitter axis E1, first emitter cone half angle θE1, second receiving cone <NUM>, second receiving cone axis R2, second receiving cone half angle θR2, and third sensing volume <NUM>. First emitter axis E1 has first emitter axis azimuthal angle φE1 (not shown) and first emitter cone half angle θE1, as described in <FIG>. Second receiving cone axis R2 has second receiving cone axis azimuthal angle φR2 (not shown) and second receiving cone half angle θR2. In a particular embodiment, second receiving cone axis azimuthal angle φR2 can be measured relative to a datum on chamberless detector <NUM>. Second receiving cone half angle θR2 refers to the half angle width of the expanding three-dimensional cone of visibility that is detectible by second optical detector <NUM>. Second receiving cone half angle θR2 is measured at the half-intensity point of optical energy being detected by second optical detector <NUM>. This can also be referred to as the FWHM.

The description of covered point sensor <NUM> is similar to as in <FIG> and <FIG>. In the illustrated embodiment, protective cover <NUM> is optically transparent to the wavelength of light that is produced by first optical emitter <NUM> and received by second optical detector <NUM>. Accordingly, first emitting cone <NUM> is projected through inside region <NUM> to outside region <NUM>, and second receiving cone <NUM> extends through inside region <NUM> to outside region <NUM>. Third sensing volume <NUM> is defined by the spatial overlap of first emitter cone <NUM> and second receiving cone <NUM>. In the illustrated embodiment, third sensing volume <NUM> is defined entirely within outside region <NUM>. As can be seen in <FIG>, the definition of third sensing volume <NUM> is dependent on first emitter axis E1, first emitter cone half angle θE1, second receiving cone axis R2, and second receiving cone half angle θR2.

<FIG> is a side view of covered point sensor <NUM> in an arrangement not forming part of the present invention. Shown in <FIG> are covered point sensor <NUM>, chamberless detector <NUM>, first optical emitter <NUM>, second optical emitter <NUM>, first optical detector <NUM>, second optical detector <NUM>, inside region <NUM>, protective cover <NUM>, outside region <NUM>, second emitting cone <NUM>, second emitter axis E2, second emitter cone half angle θE2, first receiving cone <NUM>, first receiving cone axis R1, first receiving cone half angle θR1, and fourth sensing volume <NUM>. The description of covered point sensor <NUM> is similar to as in <FIG>. In the illustrated arrangement, protective cover <NUM> is optically absorptive to one or more of the wavelengths of light produced by second optical emitter <NUM> and received by first optical detector <NUM>. Accordingly, second emitting cone <NUM> is projected within inside region <NUM>, but does not pass through protective cover <NUM> to outside region <NUM>. Similarly, first receiving cone <NUM> is created within inside region <NUM>, but does not extend to outside region <NUM>. In the illustrated arrangement, the protective cover <NUM> is a homogeneous material that is optically absorptive. In other arrangements, protective cover <NUM> can be non- homogeneous. In yet other arrangements, protective cover <NUM> can have an optically absorptive coating.

Fourth sensing volume <NUM> is defined by the spatial overlap of second emitter cone <NUM> and first receiving cone <NUM>, and is therefore truncated by protective cover <NUM>. In the illustrated arrangement, truncating fourth sensing volume <NUM> by protective cover <NUM> can be beneficial in reducing the occurrences of false alarms that could otherwise occur from fourth sensing volume <NUM> extending into outside region <NUM> where external interference may exist. This can improve the operational robustness of covered point sensor <NUM>. As can be seen in <FIG>, the definition of fourth sensing volume <NUM> is dependent on second emitter axis E2, second emitter cone half angle θE2, first receiving cone axis R1, and first receiving cone half angle θR1. In another arrangement, fourth sensing volume <NUM> can be made larger than is illustrated in <FIG> by the selection of second emitter axis E2, second emitter cone half angle θE2, first receiving cone axis R1, and/or first receiving cone half angle θR1 to provide a greater volume of spatial overlap between second emitting cone <NUM> and first receiving cone <NUM>.

<FIG> is a cross sectional side view of protective cover <NUM>. Shown in <FIG> are covered point sensor <NUM>, chamberless detector <NUM>, first optical emitter <NUM>, second optical emitter <NUM>, first optical detector <NUM>, second optical detector <NUM>, inside region <NUM>, protective cover <NUM>, outside region <NUM>, cover substrate <NUM>, inside coating <NUM>, and outside coating <NUM>. The description of chamberless detector <NUM> is similar to that of <FIG>. Protective cover <NUM> comprises cover substrate <NUM>, inside coating <NUM>, and outside coating <NUM>. In the illustrated embodiment, cover substrate <NUM> can be any material that provides form and structure for protective cover <NUM> including, with non-limiting examples including acrylic, glass, resin, fiberglass, and metal. Inside coating <NUM> and outside coating <NUM> is each an optical coating. Inside coating <NUM> covers the surface of protective cover <NUM> that faces inside region <NUM>, and outside coating <NUM> covers the surface of protective cover <NUM> that faces outside region <NUM>. In some embodiments, inside coating <NUM> or outside coating <NUM> can be omitted from protective cover <NUM>. In other embodiments, both inside coating <NUM> and outside coating <NUM> can be omitted from protective cover <NUM>. In these other embodiments, cover substrate can be a homogeneous or non-homogeneous material that is optically absorptive at the wavelength or wavelengths of light emitted from first optical emitter <NUM> and second optical emitter <NUM>. In some embodiments, inside coating <NUM> and/or outside coating <NUM> can be reflective at one or more wavelengths of light. In characterizing a material as reflective at a particular wavelength, the reflectivity at a particular wavelength is generally greater than <NUM>%. In other embodiments, inside coating <NUM> and/or outside coating <NUM> can be anti-reflective at one or more wavelengths of light. In characterizing a material as anti-reflective at a particular wavelength, the anti-reflectivity at a particular wavelength is generally less than <NUM>%. However, in some embodiments, inside coating <NUM> and/or outside coating <NUM> can be characterized as being anti-reflective with an anti-reflectivity that is greater than <NUM>%. Anti-reflective coatings are known to those who are skilled in the optical arts. For example, an anti-reflective coating can be a thin layer of material having an index of refraction that is between the indices of refraction of cover substrate <NUM> and the air medium surrounding protective cover <NUM>. Moreover, for example, an anti-reflective coating can be a thin layer of material having a thickness that is one-quarter wavelength of the light of concern.

In the embodiment depicted in <FIG>, inside coating <NUM> can comprise one or more layers, with each of the one or more layers being configured to provide a specific interaction with incident light. Similarly, outside coating <NUM> can comprise one or more layers, with each of the one or more layers being configured to provide a specific interaction with incident light. As with cover substrate <NUM>, inside coating <NUM> and outside coating <NUM> can each individually or together in any combination provide several specific interactions with incident light including transmission, absorption, and reflection, with each interaction occurring at a particular wavelength or across a particular wavelength band or bands. The transmission, absorption, and/or reflection of light by inside coating <NUM> and/or outside coating <NUM> can result from the intrinsic properties of inside coating <NUM> and/or outside coating <NUM>. In other embodiments, inside coating <NUM> and/or outside coating <NUM> can be comprised of diffraction gratings or other polarization materials. In some embodiments, the transmission, absorption, and/or reflection of light protective cover <NUM> can result from the mismatch between two or more indices of refraction. In the illustrated embodiment, the two or more indices of refraction can exist between inside coating <NUM>, cover substrate <NUM>, outside coating <NUM>, and/or the ambient environment. In some embodiments, the two or more indices of refraction can exist between two or more layers that comprise inside coating <NUM>, and/or between two or more layers that comprise outside coating <NUM>. In other embodiments, the two or more indices of refraction can exist between any combination of inside coating <NUM>, cover substrate <NUM>, and outside coating <NUM>.

It is to be appreciated that in some materials, the index of refraction is dependent on the wavelength of light incident on the material. Accordingly, a particular material can have a different index of refraction for each of the plurality of wavelengths being emitted from first optical emitter <NUM> and from second optical emitter <NUM>, as well as ambient light in the environment. Moreover, a particular material can have a different index of refraction for each of the plurality of wavelengths being scattered or fluoresced by particulates within first receiving cone <NUM> and/or second receiving cone <NUM>. Thus, the selection of materials for inside coating <NUM>, cover substrate <NUM>, and outside coating <NUM> can influence the transmission, absorption, and/or reflection of light by protective cover <NUM> over various wavelengths.

In some embodiments, inside coating <NUM> and/or outside coating <NUM> can be electrically conductive to provide one or more benefits. For example, an electrically conductive inside coating <NUM> and/or outside coating <NUM> can provide shielding from electromagnetic interference (EMI). Also, for example, an electrically conductive inside coating <NUM> and/or outside coating <NUM> can dissipate a static electricity charge from protective cover <NUM>, thereby minimizing or preventing the static attraction of particulates on protective cover <NUM>.

Referring again to <FIG>, the optical properties of inside coating <NUM>, cover substrate <NUM>, and/or outside coating <NUM> can affect light produced from first optical emitter <NUM> and from second optical emitter <NUM>. Accordingly, the optical properties of inside coating <NUM>, cover substrate <NUM>, and/or outside coating <NUM> can define the boundaries of first emitting cone <NUM> and second emitting cone <NUM>. In the illustrated embodiment, the optical properties of inside coating <NUM>, cover substrate <NUM>, and/or outside coating <NUM> can be wavelength dependent and first optical emitter <NUM> can have a wavelength that is different from second optical emitter <NUM>. Accordingly, the boundaries of first emitting cone <NUM> and second emitting cone <NUM> can be different from each other, depending on the particular wavelengths and optical properties that are used. The optical properties of inside coating <NUM>, cover substrate <NUM>, and/or outside coating <NUM> can also affect light that is scattered and/or fluoresced from airborne particles (not shown) that can be within inside region <NUM> and/or outside region <NUM>.

In some embodiments it can be important to prevent or reduce the effect of light sources outside of covered point sensor <NUM> from interfering with first optical detector <NUM> and/or second optical detector <NUM>, which could otherwise adversely affect the operation of covered point sensor <NUM>. Sources of light from outside region <NUM> can include light from first optical emitter <NUM> and/or second optical emitter <NUM> that is scattered from particulates in outside region <NUM>, or from ambient light external to covered point sensor <NUM>. Non-limiting examples of ambient light can include light sources in the vicinity of covered point sensor such as office, room, and cargo bay lighting, or from direct or reflected light from other sources such as sunlight. These various sources of ambient light can be broad or narrow bands of light in the range of wavelengths from about <NUM> - <NUM>. Ambient light originating external to covered point sensor <NUM> can be referred to as ambient light. Accordingly, the optical properties of inside coating <NUM>, cover substrate <NUM>, and/or outside coating <NUM> can be configured to reduce or eliminate these external sources of light from affecting from first optical emitter <NUM> and/or second optical emitter <NUM>.

<FIG> is a graph of optical transmission vs. wavelength for an embodiment of protective cover <NUM> shown in <FIG>, with the axes of the graph being optical transmission (%) vs. wavelength (nm). Shown in <FIG> are first peak <NUM>, second peak <NUM>, and valley <NUM>. First peak <NUM> and second peak <NUM> are regions of high optical transmission by protective cover <NUM>. Optical transmission can also be referred to as optical transmissivity. In the illustrated embodiment, first peak <NUM> occurs at a wavelength between approximately <NUM> - <NUM>, and second peak <NUM> occurs at wavelengths above approximately <NUM> - <NUM>. These wavelength ranges can be referred to as the bandwidths. In some embodiments, second peak can extend to wavelengths that are greater than <NUM>. First peak <NUM> and/or second peak <NUM> can include wavelengths that are associated with first optical emitter <NUM> and/or second optical emitter <NUM>. Valley <NUM> includes the wavelengths that lie between first peak <NUM> and second peak <NUM>. Valley <NUM> is a region of wavelengths of low optical transmission by protective cover <NUM>, and can include wavelengths of light that are associated with interfering sources of light.

In other embodiments, first peak <NUM> and/or second peak <NUM> can occur between different wavelengths of light. Accordingly, in these other embodiments, valley <NUM> can include a different range of wavelengths of light. In some embodiments, there can be only one transmission peak. In yet other embodiments, there can be more than two transmission peaks. In some embodiments, there can be two or more valleys.

Referring back to <FIG>, the depicted embodiment disclosed protective cover <NUM> as being optically absorptive to one or more the wavelengths of light produced by second optical emitter <NUM> and received by first optical detector <NUM>. Accordingly, a graph of optical transmission vs. wavelength for the embodiment of protective cover <NUM> shown in <FIG> would be zero, or a relatively small value, at the bandwidths of interest.

<FIG> is a graph of optical reflection vs. wavelength for another embodiment of protective cover <NUM> shown in <FIG>, with the axes of the graph being optical reflection (%) vs. wavelength (nm). Shown in <FIG> are first peak <NUM>, second peak <NUM>, and valley <NUM>. First peak <NUM> and second peak <NUM> are regions of high optical reflection by protective cover <NUM>. Optical reflection can also be referred to as optical reflectivity. In the illustrated embodiment, first peak <NUM> occurs at a wavelength between approximately <NUM> - <NUM>, and second peak <NUM> occurs at a wavelength between approximately <NUM> - <NUM>, as measured at the FWHM. These wavelength ranges can be referred to as the bandwidths. In some embodiments, first peak <NUM> and/or second peak <NUM> can include wavelengths that are associated with first optical emitter <NUM> and/or second optical emitter <NUM>. In other embodiments, first peak <NUM> and/or second peak <NUM> can include wavelengths that are associated with interfering sources of light, for which it is desirable they be reflected. Valley <NUM> includes the wavelengths that lie between first peak <NUM> and second peak <NUM>. Valley <NUM> is a region of wavelengths of low optical reflection by protective cover <NUM>, and can include wavelengths of light that are associated with first optical emitter <NUM> and/or second optical emitter <NUM>. In some embodiments, valley <NUM> can include wavelengths of light that are associated with interfering sources of light. In some embodiments, it can be desirable to reject interfering wavelengths of light to improve the performance of covered point sensor <NUM>.

In other embodiments, first peak <NUM> and/or second peak <NUM> can occur between different wavelengths of light. Accordingly, in these other embodiments, valley <NUM> can include a different range of wavelengths of light. In some embodiments, there can be only first reflection peak <NUM>. In yet other embodiments, there can be three or more reflection peaks. In some embodiments, there can be two or more valleys.

In the illustrated embodiment, the properties of optical reflection and/or optical anti-reflection for protective cover <NUM> can be different between inside coating <NUM> and outside coating <NUM>, thereby affecting light in inside region <NUM> and outside region <NUM> differently. Therefore, in specifying optical reflection and/or anti-reflection, a distinction is made between inside coating <NUM> and outside coating <NUM>. In other embodiments, inside coating <NUM> and outside coating <NUM> can have similar optical properties of reflection.

It is to be understood that the optical properties of protective cover <NUM>, as shown in <FIG>, can be characterized by several different characteristics, including without limitation, transmission, reflection, and absorption. Moreover, the optical properties of inside coating <NUM> can be different from the optical properties of outside coating <NUM>. Protective cover <NUM> can have optical properties of absorption (not shown). The optical properties of absorption can be shown graphically on axes of optical absorption (%) vs. wavelength (nm), similar to the optical properties of transmission and reflection as shown in <FIG> and <FIG>, respectively. Therefore, several graphs of various optical properties vs. wavelength can be used to characterize the optical properties of protective cover <NUM> in various embodiments.

Claim 1:
A covered chamberless particulate detector comprising:
a chamberless detector (<NUM>) configured to produce a signal when particulate sensing events occur;
one or more optical emitters (<NUM>, <NUM>) disposed on the chamberless detector (<NUM>), configured to emit one or more emitting cones of light (<NUM>, <NUM>);
one or more optical sensors (<NUM>, <NUM>) disposed on the chamberless detector (<NUM>), defining one or more receiving cones (<NUM>, <NUM>);
a protective cover (<NUM>) defining an inside region (<NUM>) and an outside region (<NUM>), the protective cover (<NUM>) disposed on the chamberless detector (<NUM>); and one or more apertures through the protective cover;
wherein:
each of the one or more emitting cones of light is configured to spatially overlap with each of the one or more receiving cones, thereby creating one or more sensing volumes;
each of the one or more optical sensors (<NUM>, <NUM>) is configured to detect occurrence of particulate sensing events;
at least one of the one or more sensing volumes are located within the inside region;
at least one of the one or more sensing volumes are located within the outside region; and
the cover is transparent to some or all wavelengths of light produced by the one or more optical emitters and received by the one or more optical sensors.