JP2011203889A - Smoke detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a smoke detector having a wide monitoring range and allowing reliable detection of a fire while providing a smoke detection space outside a casing.SOLUTION: The smoke detector, which determines the fire by emitting light into the smoke detection space outside the casing and receiving the light obtained by scattering the emitted light by a scattering body, includes: a light emitting element 7; a first light receiving element 9; a second light receiving element 11; and a polarizing filter 13 which polarizes the light emitted from the light emitting element 7 and the light received by the first light receiving element 9. The light emitting element 7, the first light receiving element 9 and the second light receiving element 11 are disposed so that the angles formed by their optical axes are 30 degrees or less. A fire determination part 15 for determining the fire inputs a light receiving signal of the first light receiving element 9 entered through the polarizing filter 13 and a light receiving signal of the second light receiving element 11 entered without the polarizing filter 13 and determines the fire based on an output ratio of the light receiving signal of the first light receiving element 9 and the light receiving signal of the second light receiving element 11.

Description

  The present invention relates to a smoke detector that detects smoke by detecting scattered light from smoke.

Scattered light smoke detectors generally introduce smoke from outside into a smoke detection space formed in the sensor body, irradiate the smoke detection space with light from a light emitting element, and receive the scattered light of the smoke. A fire is detected by receiving light at the element.
However, in the case where the smoke detection space is formed in such a detector body, the smoke detector protrudes from the ceiling surface or the like in the installed state, which is not preferable in terms of design, and smoke is not allowed in the smoke detection space. There is a problem that a time delay occurs in the detection of smoke due to the structure that introduces the.

  Therefore, in order to solve the problem caused by providing such a smoke detection space inside the sensor body, instead of providing a smoke detection space inside the sensor body, a smoke detection space is provided outside the sensor body. There has been proposed a scattered light type smoke detector provided (see Patent Document 1).

  The scattering smoke detector described in Patent Document 1 is “attached to the sensor body, the light emitting opening and the light receiving opening provided on the outer surface of the sensor body, and the outer surface of the sensor body. A transparent cover that covers the light emitting opening and the light receiving opening, and a light emitting means, a light receiving means, and a fire determining means built in the sensor body, wherein the light emitting means is an open-shaped member located outside the transparent cover. Light is emitted to the smoke detection point set in the smoke detection space through the light emitting opening, and the light receiving means transmits scattered light to the light emitted to the smoke detection point through the light receiving opening. And receiving a light reception signal corresponding to the received light amount of the received scattered light, and the fire determining means is configured to generate a fire based on the light reception amount specified by the light reception signal output from the light receiving means. It is characterized by judging the presence or absence That. "(Patent Document 1 [0011] Referring) is intended.

  The scattered light type smoke detector disclosed in Patent Document 1 outputs a light reception signal corresponding to the amount of scattered light received, and determines the presence or absence of a fire based on the light reception signal. And as a concrete means of fire judgment, judgment is made based on the amount of received light and its differential value.

Japanese Patent No. 4347296

The most important point to note when a smoke detection space is provided outside the housing is that there is dust other than smoke in the smoke detection space outside the housing. It is to discriminate accurately whether the light is scattered light by other particles.
In this regard, in Patent Document 1, based on the light reception signal from the light receiving element and its differential value, each signal is compared with a predetermined threshold value to determine whether the light is scattered light due to fire smoke. I am doing so.

However, since the discrimination of Patent Document 1 is basically discrimination based on the particle size of the scatterer, there is a problem that it is difficult to distinguish fine dust close to smoke particles from smoke particles.
For this reason, in patent document 1, it arrange | positions so that the optical axis of a light receiving element and a light emitting element may face each other diagonally downward, and let the cross | intersection part be a smoke detection point. This is because in Patent Document 1 where it is difficult to distinguish between smoke particles and dust, for example, when light is irradiated directly below, the smoke detection point becomes far away, so that scattered light generated by scatterers other than smoke is easily received. This is because malfunctions increase. Further, when the smoke detection point is far from the smoke detector, the intensity of each scattered light is weakened, the amount of scattered light received is reduced, and it becomes more difficult to distinguish between smoke particles and dust.
As described above, in Patent Document 1, in order to reduce the existence probability of scatterers other than smoke and to increase the amount of received light as much as possible, the smoke detection point that is the intersection of the light axis of the light emitting element and the light receiving element is set to the smoke detector body. It was not possible to leave a large distance from the outer surface, and thus the monitoring range in the front direction of the scattered light smoke detector could not be widened. Incidentally, in Patent Document 1, the smoke detection point is set to a height of about 5 mm from the outer surface of the smoke detector body (see paragraph [0191] of Patent Document 1).
However, smoke generated during the initial fire passes through a position 15 to 500 mm away from the ceiling surface along the ceiling surface, so that smoke with a narrow monitoring range such as that described in Patent Document 1 is emitted. Cannot be detected. In particular, when a smoke detector is embedded in the ceiling surface, it cannot be detected at all.

  The present invention has been made to solve such a problem, and provides a smoke detector capable of reliably detecting a fire by widening a monitoring range while providing a smoke detection space outside the housing. It is an object.

(1) A smoke detector according to the present invention includes a housing, a light emitting unit that is disposed inside the housing and emits irradiation light toward a smoke detecting unit outside the housing, A light receiving unit that is disposed inside, receives light scattered by a scatterer present in the smoke detector, and outputs a light reception signal based on the amount of scattered light received, and the light receiving unit In a smoke detector comprising a fire determination unit that determines the presence or absence of a fire based on the received light signal output by
The light emitting unit and the light receiving unit are arranged so that an angle formed by the optical axis of the light emitting unit and the optical axis of the light receiving unit is 30 degrees or less, and the light emitting unit transmits polarized light to the smoke detecting unit. The light receiving unit is configured by a first light receiving unit that receives scattered light polarized in the same direction as the light emitting unit, and a second light receiving unit that receives the scattered light as it is,
The fire determination unit inputs a light reception signal of the first light receiving unit and a light reception signal of the second light receiving unit, and sets an output ratio between the light reception signal of the first light receiving unit and the light reception signal of the second light receiving unit. The presence or absence of a fire is judged based on this.

(2) In addition, a smoke detector according to the present invention includes a housing, a light emitting unit that is disposed inside the housing and emits irradiation light toward a smoke detecting unit outside the housing, and the housing. A light receiving unit that is disposed inside the body, receives scattered light generated by a scatterer present in the smoke detecting unit, and outputs a light reception signal based on the amount of scattered light received; In a smoke detector including a fire determination unit that determines the presence or absence of a fire based on a light reception signal output by the light receiving unit, an angle formed by the optical axis of the light emitting unit and the optical axis of the light receiving unit is 30 degrees or less. As described above, the light emitting unit and the light receiving unit are arranged, and the light emitting unit emits light polarized by a polarizing filter toward the smoke detecting unit, and the light receiving unit has the same direction as the light emitting unit. Receives either polarized or unpolarized scattered light The fire determination unit, the control unit configured to switch whether the light receiving unit receives scattered light polarized in the same direction as the light emitting unit or received non-polarized scattered light. Is characterized in that the presence or absence of a fire is determined based on the output ratio of the light receiving signal that passes through the polarizing filter and the light receiving signal that does not pass through the polarizing filter.

  In the present invention, the light emitting unit and the light receiving unit are arranged so that an angle formed by the optical axis of the light emitting unit and the optical axis of the light receiving unit is 30 degrees or less, and the light emitting unit is polarized light. The light receiving unit is configured to emit light toward the smoke detecting unit, and the light receiving unit receives a scattered light polarized in the same direction as the light emitting unit, and a second light receiving unit receives the scattered light as it is. The fire determination unit inputs the light reception signal of the first light receiving unit and the light reception signal of the second light receiving unit, and receives the light reception signal of the first light receiving unit and the light reception signal of the second light receiving unit. Since the presence / absence of a fire is determined based on the output ratio, the monitoring range can be widened and the presence / absence of a fire can be reliably determined.

It is sectional drawing of the smoke detector which concerns on one embodiment of this invention, and is sectional drawing which follows the arrow AA line of FIG. It is a side view of the smoke detector which concerns on one embodiment of this invention. It is a front (lower surface in an installation state) figure of the smoke detector which concerns on one embodiment of this invention. It is a perspective view of the smoke detector which concerns on one embodiment of this invention. It is a figure of the state which removed the front cover of the smoke detector which concerns on one embodiment of this invention. It is a circuit block diagram of the smoke detector which concerns on one embodiment of this invention. It is operation | movement explanatory drawing of the smoke detector which concerns on one embodiment of this invention, FIG.7 (b) is a front view, FIG.7 (a) is sectional drawing which follows the arrow AA line of FIG.7 (b). It is. It is explanatory drawing of the other aspect of the smoke detector which concerns on one embodiment of this invention. It is explanatory drawing of the other aspect of the smoke detector which concerns on one embodiment of this invention.

A smoke detector according to an embodiment of the present invention will be described with reference to FIGS.
The smoke detector 1 of the present embodiment includes a cylindrical casing 5 having an optical bench 3 inside and a flat outer shape, and a smoke detector 50 (see FIG. 7), and a first light receiving element 9 which is installed on the optical bench 3 and receives scattered light generated by particles existing in the smoke detecting unit 50. And the second light receiving element 11, the polarization filter 13 that polarizes the light emitted from the light emitting element 7 and the light incident on the first light receiving element 9, and the light receiving signal received by the first light receiving element 9 and the second light receiving element 11. And a PC board 17 on which a fire determination unit 15 and the like for determining the presence or absence of a fire are mounted.
Since the light emitting element 7 emits light polarized toward the smoke detecting section through the polarizing filter 13, the light emitting element 7 and the polarizing filter 13 constitute the light emitting section of the present invention.
Moreover, since the 1st light receiving element 9 receives the light polarized through the polarizing filter 13, the 1st light receiving element 9 and the polarizing filter 13 comprise the 1st light-receiving part of this invention.
Moreover, since the 2nd light receiving element 11 receives scattered light as it is, it comprises the 2nd light-receiving part of this invention.
Each configuration will be described in more detail.

<Case>
The casing 5 has a cylindrical shape with a flat outer shape, and a circular front cover 19 is provided on a portion that becomes a lower surface in the installed state. As shown in FIGS. 3 and 4, three circular openings are formed in the center of the front cover 19. The three openings are a light emitting opening 21 provided at the center of the front cover 19, a first light receiving opening 23 provided at a symmetrical position across the light emitting opening 21, and a second light receiving opening. Opening 25.
An optical bench 3 is provided inside the housing 5, and optical parts such as a light emitting element 7, a first light receiving element 9, and a second light receiving element 11 are installed on the optical bench 3.

<Light emitting element>
The light emitting element 7 is composed of an infrared LED, and one light emitting element 7 is arranged at the approximate center of the optical bench 3 and emits infrared light to the smoke detector 50 in a pulsed manner. The light emitting part of the light emitting element 7 is disposed opposite to the light emitting opening 21 provided in the center of the front cover 19.
The light emitting element 7 is arranged so that the optical axis thereof is directed directly downward when the smoke detector 1 is installed on a ceiling surface or the like.

<Light receiving element>
The light receiving element includes two light receiving elements, a first light receiving element 9 and a second light receiving element 11. The first light receiving element 9 and the second light receiving element 11 are arranged at symmetrical positions with the light emitting element 7 interposed therebetween. The first light receiving element 9 and the second light receiving element 11 are arranged at symmetrical positions because the light irradiated by the light emitting element 7 is an optical path of the scattered light scattered by the scatterer 33 (see FIG. 7) floating in the smoke detection space. This is because the first light receiving element 9 and the second light receiving element 11 are equal. Therefore, as long as the optical paths are the same, the above-described configuration may not be symmetrical.

The light receiving part of the first light receiving element 9 is disposed opposite to the first light receiving opening 23 provided in the front cover 19, and the light receiving part of the second light receiving element 11 is provided for the second light receiving provided in the front cover 19. Opposed to the opening 25.
The first light receiving element 9 and the second light receiving element 11 are arranged such that the optical axis thereof is directed downward when the smoke detector 1 is installed on a ceiling surface or the like.

Since the light emitting element 7, the first light receiving element 9 and the second light receiving element 11 are adjacent to each other and their optical axes are arranged to face directly below in the installed state, the light emitting element 7 and the first light receiving element 9 are arranged. And the optical axis of the 2nd light receiving element 11 is substantially parallel. That is, in the present embodiment, the angle formed by the optical axis of the light emitting unit and the light receiving unit is approximately 0 degrees. With such an arrangement, the smoke detector 50 (monitoring range) can be widened downward from the smoke detector 1, and even fire smoke away from the smoke detector 1 can be reliably detected.
Further, by arranging the optical axes of the light emitting element 7, the first light receiving element 9 and the second light receiving element 11 substantially in parallel, these elements can be concentrated in the central portion, and the smoke detector 1 can be downsized. There is also an effect that can be done.

<Polarizing filter>
The polarizing filter 13 is a filter having a property of transmitting only a component in one direction among the vibration directions of light. The polarizing filter 13 is installed inside the front cover 19 as shown in FIG. Then, as shown in FIG. 5, the light emitted from the light emitting element 7 and the light received by the first light receiving element 9 are transmitted. That is, in the present embodiment, the light emitted from the light emitting element 7 to the smoke detector 50 and the light incident on the first light receiving element 9 are configured to pass through one polarizing filter 13. Therefore, there is no individual difference between the polarization filters 13 as compared with the case where the light emitting element 7 and the first light receiving element 9 are provided with different polarization filters 13, respectively. Is possible.
Note that the case where separate polarizing filters 13 are provided for the light emitting element 7 and the first light receiving element 9 is not excluded. However, when the first polarizing filter 13 is provided on the front surface of the light emitting element 7 and the second polarizing filter (not shown) is provided on the front surface of the first light receiving element 9, the polarization directions of the first polarizing filter 13 are the same.

<PC board>
As shown in the circuit block diagram of FIG. 6, the PC board 17 includes a light emission control unit 27 that drives the light emitting element 7, and an amplification circuit 29 that amplifies the light reception signals of the first light receiving element 9 and the second light receiving element 11. And a control unit 31 that performs various controls. The control part 31 implement | achieves various functions, for example, the fire determination part 15, when CPU runs a predetermined program.
The fire determination unit 15 calculates the degree of depolarization by A / D converting the detection signals obtained by amplifying the light reception signals of the first light receiving element 9 and the second light receiving element 11 to obtain the ratio of each detection level. Whether or not there is a fire is determined based on whether the degree of depolarization is within a predetermined range.
When the fire determination unit 15 determines that a fire has occurred, the control unit 31 outputs a fire signal to a fire receiver (not shown).

  Here, the degree of depolarization will be described. If the light transmitted from the light emitting element 7 through the polarizing filter 13 and applied to the smoke detector 50 is scattered by particles (scatterer 33) existing in the smoke detector 50, the scatterer 33 is spherical. Although the polarization direction of the irradiation light of the light emitting element 7 that has passed through the polarizing filter 13 and the scattered light generated by the scatterer 33 does not change, when the scatterer 33 is aspherical, the polarization direction changes variously. The rate at which the polarization changes by the scatterer 33 is called the degree of depolarization. That is, when the degree of depolarization is small or absent, it means that the scatterer 33 is spherical like smoke particles, and when the degree of depolarization is large, the scatterer 33 is like dust or the like. It means non-spherical.

For example, in the case of smoke, the degree of depolarization is about 10%, and dust such as cedar pollen is about 30%. Taking this case as a specific example, a simplified description is as follows. If the scatterer is smoke particles, if the degree of depolarization is 10%, the intensity of light incident on the second light receiving element 9 is 90 if the intensity of light incident on the second light receiving element 11 is 100. Thus, the output ratio of the respective light receiving signals of the first light receiving element 9 and the second light receiving element 11 is 0.9.
On the other hand, when the scatterer is dust, assuming that the intensity of light incident on the second light receiving element 11 is 100, the intensity of light incident on the first light receiving element 9 is 70, and these first light receiving elements The output ratio of each light reception signal between 9 and the second light receiving element 11 is 0.7. Therefore, for example, the threshold value is set to about 0.8 to 0.85, and the fire determination unit 15 determines that a fire has occurred when the output ratio of the received light signal exceeds this threshold value. If it is determined that it is not a fire, it is possible to determine whether it is a fire reliably or simply.

The operation of the present embodiment configured as described above is based on FIG. 7 when the scatterer 33 present in the smoke detector 50 is smoke (in the case of fire) and dust (in the case of no fire). Will be described.
<When the scatterer is smoke>
Based on the control signal of the light emission control unit 27, the light emitting element 7 emits pulses. The light emitted from the light emitting element 7 is transmitted through the polarizing filter 13 and is polarized upon transmission. Polarized transmitted light is scattered by smoke, but in this case, the direction of polarization does not change because the smoke particles are substantially spherical. The scattered light whose polarization direction does not change passes through the polarizing filter 13 and enters the first light receiving element 9 and enters the second light receiving element 11 without passing through the polarizing filter 13. When entering the first light receiving element 9, it passes through the polarizing filter 13, but since the direction of polarization does not change due to scattering, the intensity of the light passing through the polarizing filter 13 and entering the first light receiving element 9 is The intensity of light incident on the two light receiving elements 11 is substantially the same. Therefore, in this case, the fire determination unit 15 calculates the ratio of the detection levels of the respective light reception signals, and determines that it is a fire because it exceeds the threshold value.

<When the scatterer is dust>
The light emitted from the light emitting element 7 is transmitted through the polarizing filter 13, and when the polarized transmitted light is scattered by dust, the direction of polarized light changes to various directions and the polarized light is eliminated. The scattered light whose polarization has been eliminated passes through the polarizing filter 13 and enters the first light receiving element 9, but can pass through the polarizing filter 13 and vibrates in the same direction as the polarization direction of the polarizing filter 13. Since it is only light, its intensity is weakened. On the other hand, since the intensity of the light incident on the second light receiving element 11 does not pass through the polarizing filter 13, the scattered light is incident as it is. Therefore, in this case, a difference occurs in the light receiving intensity between the first light receiving element 9 and the second light receiving element 11. And the fire judgment part 15 calculates ratio of the detection level of each received light signal, and judges that it is not a fire, if it is less than a threshold value.

As described above, according to the smoke detector 1 of the present embodiment, since the optical axes of the light emitting element 7, the first light receiving element 9, and the second light receiving element 11 are arranged substantially in parallel, the monitoring range is widened. Thus, it is possible to reliably detect the detection target, and it is possible to reliably distinguish dust and the like, which are the objects to be most distinguished, from smoke and accurately determine the presence or absence of a fire.
In the present embodiment, as described above, the light irradiated from the light emitting element 7 and the light incident on the first light receiving element 9 are transmitted through the common polarizing filter 13. There is no difference, and more accurate detection is possible.

  However, as indicated by the broken line arrow in FIG. 7, when the light emitting element 7 is an infrared LED, the light emitted from the light emitting element 7 is internally reflected by the polarizing filter 13 because it is not as straight as laser light. It is conceivable that the reflected light is incident on the first light receiving element 9. That is, the light incident on the first light receiving element 9 is the sum of the scattered light scattered by the scatterer 33 and the internally reflected light. Therefore, it is preferable to correct the amount of internally reflected light. For this purpose, the fire determination unit 15 may subtract the amount of light received by internal reflection from the amount of light received by the first light receiving element 9. The amount of light received by the internal reflection is obtained from the light reception signal of the first light receiving element 9 in which the scatterer 33 does not exist in the smoke detector (when no smoke is present). That is, the correction means may be provided in the fire determination unit 15.

<Arrangement of light emitting element, first light receiving element, and second light receiving element>
In the above embodiment, the light emitting element 7, the first light receiving element 9, and the second light receiving element 11 are arranged on both sides of the light emitting element 7 with the light emitting element 7 as the center, as shown in FIGS. The 1st light receiving element 9 and the 2nd light receiving element 11 were arrange | positioned in the symmetrical position with respect to the light emitting element 7, and the optical axis of each element became parallel.
With such an arrangement, as described above, the smoke detector (monitoring range) can be widened, and each element can be concentrated in the center of the smoke detector 1, so that the smoke detector 1 can be downsized. Is realized.
The reason why the smoke detection section (monitoring range) is widened and the size is reduced is that the optical axes of the light emitting element 7, the first light receiving element 9, and the second light receiving element 11 are parallel to each other. As another mode in that case, for example, as shown in FIG. 8, the smoke detector 1 may be installed on the ceiling surface or the like, and the optical axis of each element may not be directed downward.

In the above example, the optical axes of the light emitting element 7 and the first light receiving element 9 and the second light receiving element 11 are parallel. However, as shown in FIG. The first light receiving element 9 and the second light receiving element 11 are arranged symmetrically with respect to the light emitting element 7 on both sides thereof, and the directions of the optical axes of the first light receiving element 9 and the second light receiving element 11 are directly below. The directions may be crossed with each other.
However, in order to widen the monitoring range, the angle θ formed by the optical axes of the light emitting element 7, the first light receiving element 9, and the second light receiving element 11 is arranged to be 30 degrees or less. This is because the intersection of the optical axes can be separated from the smoke detector 1 by arranging the angle θ to be 30 degrees or less, and the monitoring range can be widened.

  In the above embodiment, an example in which one light emitting element is provided and two light receiving elements are provided is shown. However, the number of light emitting elements can be set to a plurality by increasing the number of light receiving elements and the number of light receiving elements. It is possible to accurately detect various detection objects existing in the monitored range.

  In the above embodiment, the two light receiving elements of the first light receiving element 9 and the second light receiving element 11 are used as the light receiving elements. However, the light receiving elements are single and incident on the light receiving portion of the light receiving element. The control unit 31 may intermittently switch between when the light to be transmitted is transmitted through the polarizing filter and when it is not transmitted. And the fire judgment part 15 judges the presence or absence of a fire with the output ratio of the light reception signal which permeate | transmits and transmits through a polarizing filter, and the light-receiving signal which does not permeate | transmit a polarizing filter. In this way, since not only the polarizing filter but also the light receiving element is shared, errors due to individual differences can be further reduced.

  Furthermore, in the above embodiment, an example in which the light emitting element 7 is an LED has been described. However, a laser light source such as a laser diode may be used instead of the LED. In this way, the laser light source itself emits light polarized in a single direction, so that the light-emitting element 7 does not require the polarizing filter 13.

DESCRIPTION OF SYMBOLS 1 Smoke detector 3 Optical stand 5 Case 7 Light emitting element 9 1st light receiving element 11 2nd light receiving element 13 Polarizing filter 15 Fire judgment part 17 PC board 19 Front cover 21 Light emission opening 23 1st light reception opening 25 1st 2 Opening for light reception 27 Light emission control part 29 Amplifying circuit 31 Control part 33 Scattering body 50 Smoke detection part

Claims (2)

A housing, a light emitting unit disposed inside the housing and emitting irradiation light toward a smoke detection unit outside the housing, and a light emitting unit disposed inside the housing and emitted from the light emitting unit Receives a scattered light generated by a scatterer existing in the smoke detector, and outputs a light reception signal based on the amount of scattered light received, and whether there is a fire based on the light reception signal output by the light reception unit In a smoke detector comprising a fire determination unit for determining
The light emitting unit and the light receiving unit are arranged so that an angle formed by the optical axis of the light emitting unit and the optical axis of the light receiving unit is 30 degrees or less, and the light emitting unit transmits polarized light to the smoke detecting unit. The light receiving unit is configured by a first light receiving unit that receives scattered light polarized in the same direction as the light emitting unit, and a second light receiving unit that receives the scattered light as it is,
The fire determination unit inputs a light reception signal of the first light receiving unit and a light reception signal of the second light receiving unit, and sets an output ratio between the light reception signal of the first light receiving unit and the light reception signal of the second light receiving unit. Smoke detector characterized by judging the presence or absence of fire based on. A housing, a light emitting unit disposed inside the housing and emitting irradiation light toward a smoke detection unit outside the housing, and a light emitting unit disposed inside the housing and emitted from the light emitting unit Receives a scattered light generated by a scatterer existing in the smoke detector, and outputs a light reception signal based on the amount of scattered light received, and whether there is a fire based on the light reception signal output by the light reception unit In a smoke detector comprising a fire determination unit for determining
The light emitting unit and the light receiving unit are arranged so that an angle formed by the optical axis of the light emitting unit and the optical axis of the light receiving unit is 30 degrees or less, and the light emitting unit receives light polarized by a polarizing filter. The light receiving section is configured to receive either one of scattered light polarized in the same direction as the light emitting section or scattered light not polarized, and emits light toward the smoke detecting section. Includes a control unit that switches between receiving scattered light polarized in the same direction as the light emitting unit or receiving unpolarized scattered light, and the fire determination unit transmits the received light signal and polarized light that pass through the polarizing filter. A smoke detector, wherein the presence or absence of a fire is determined based on an output ratio with a received light signal that does not pass through a filter.

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