Scattered light smoke detector having a wavelength selective polarizer and suitable uses of such a polarizer

Abstract

The invention relates to a scattered light smoke detector, which has a bicolor LED (1) for emitting light of a first and a second wavelength λ1, λ2, a photoelectric sensor (2) and a control unit (3). The control unit is connected to the bicolor LED and the photoelectric sensor and is configured to control the bicolor LED to emit light of the first or second wavelength, detect the photoelectric sensor signal, determine the first and second scattered radiation intensities Iλ1, Iλ2 assigned to the first and second wavelengths λ1, λ2 and take the first and second scattered radiation intensities into account together when a fire alarm (AL) is sounded. The scattered light smoke detector characteristically has a polarizer (Pλ) which is optically connected upstream of the photoelectric sensor or downstream of the bicolor LED. The polarizer has such optical properties that light passing through the polarizer is polarized to different degrees depending on its respective wavelength. The invention further relates to the suitable use of such a polarizer in optical scattered light smoke detection according to the bicolor principle.

Description

Technical Field

[0001] The present invention relates to a scattered light smoke detector, which has a bicolor LED for emitting light of a first and a second wavelength λ1, λ2, a photoelectric sensor spectrally coordinated therewith, and a control unit. The bicolor LED and the photoelectric sensor here constitute a so-called scattered light device as part of the scattered light smoke detector according to the present invention. Preferably, the bicolor LED is designed to emit only monochromatic light of the first and second wavelengths λ1, λ2. The control unit is connected to the bicolor LED and to the photoelectric sensor in terms of signal technology and is configured to control the bicolor LED to emit light of the first and / or second wavelength λ1, λ2. The control unit is further configured to detect a photoelectric sensor signal output by the photoelectric sensor. Finally, the control unit is configured to determine the first and second scattered radiation intensities I assigned (in time) to the first and second wavelengths λ1, λ2 based on the photoelectric sensor signal. λ1 ,I λ2 , and in the case of a fire alarm the first and second scattered radiation intensities I are considered together λ1 ,I λ2 . Background Art

[0002] By comparing the first and second scattered radiation intensities I received by the photosensor λ1 ,I λ2 It is possible to carry out an appropriate evaluation in terms of the particle characteristics or particle properties of the detected smoke particles, such as particle size, for example by using two scattered radiation intensities I λ1 ,I λ2 By appropriately evaluating the determined particle size or a size comparable thereto, it is then possible to differentiate, to a certain extent, for example, between smoke, dust and water vapor.

[0003] Typically, the bicolor LED is configured to emit light of a first wavelength λ1 in the range of 380 nm to 570 nm, in particular 470 nm ± 30 nm. In addition, the bicolor LED is configured to emit light of a second wavelength λ2 in the range of 750 nm to 1100 nm, in particular 940 nm ± 30 nm. Such a bicolor LED is driven in particular in a pulsed manner. The bicolor LED can be driven by means of an electronic control unit to emit pulsed light of the first wavelength λ1, the second wavelength λ2 or to emit light of the first and second wavelengths λ1, λ2 simultaneously.

[0004] In WO 2018 / 138004 A1 of the applicant, a device for optical smoke detection according to the two-color principle is described. The two-color light-emitting diode there comprises an LED chip for emitting light in a first wavelength range and a light converter for converting part of the emitted light into light in a second wavelength range. The second wavelength range has a spectral half-value width of a maximum of 100 nm. Such a two-color light-emitting diode is claimed as part of the scattered light smoke detector according to the invention described below.

[0005] In the academic field of optical smoke detection, optical smoke detectors that work according to the two-color principle are also synonymously called blue / red detectors, corresponding to a more or less "blue" first wavelength range and a more or less "red" second wavelength range. In this case, the color "blue" also includes the adjacent shorter-wave near-ultraviolet (NUV), and the color "red" also includes the adjacent longer-wave near-infrared (NIR).

[0006] The use of bicolor LEDs, i.e. bicolor light-emitting diodes, for optical smoke detection according to the so-called bicolor principle is known, for example, from EP 3 029 646 A1 and EP 2 908 298 A1 of the applicant. The described bicolor LED comprises a chip carrier on which two LED chips are arranged adjacent to one another, one of which emits light of a first "blue" wavelength λ1 and the other of which emits light of a second "red" wavelength λ2. The scattered light device there, which has a bicolor LED and a photoelectric sensor as components, allows, depending on the scattering angle between the bicolor LED and the photoelectric sensor, reliable identification of the test fire TF2 (thermal smoldering fire) specified according to standard EN54-7:2018 as well as the test fires TF4 (plastic open fire) and TF5 (liquid fire, n-heptane). The device also allows water vapor to be detected as a possible interfering variable.

[0007] To illustrate, the following Figure 5 About Business Q 02 The plotted distribution of the test fire shows this. The quotient is the scattered radiation intensity I of the first "blue" wavelength of the respective photoelectric sensor signal λ1 The intensity of the scattered radiation with the second “red” wavelength λ2 is I λ2 The scattering angle between the two-color LED and the photoelectric sensor is here, by way of example, at a typical angle value of 120°. However, it is not possible to reliably distinguish between the open flames, to which the test fires TF4 and TF5 also belong, and the test fire TF3 (smoldering cotton).

[0008] It is also known from the prior art to use polarized IR light for optical smoke detection. A corresponding scattered light device has an IR light emitting diode and two photoelectric sensors, which are arranged at the same scattering angle relative to the IR light emitting diode. A linear polarization filter is connected upstream of only one of the photoelectric sensors. Such a device allows reliable detection of the test fire TF2 (hot smoldering fire) specified in accordance with standard EN54-7:2018 as well as the test fires TF3 (smoldering cotton), TF4 (plastic flames) and TF5 (liquid fire with n-heptane).

[0009] However, it is not possible to reliably distinguish between the test fire TF2 and the interfering variable water vapor or water mist. Figure 5 About Business Q 01s The plotted distribution of the test fires shows this. 01s is the ratio of the scattered radiation intensity of vertically polarized IR light to the scattered radiation intensity of unpolarized IR light at a scattering angle of 90°. In this case, the polarization plane of the polarizer extends perpendicularly to the scattering plane.

[0010] A smoke detector is known from European patent application EP 0 926 646 A1, in which visible blue and red light are used for scattered light detection. Two measuring channels are provided, one of which is constructed in a conventional manner and comprises an infrared transmitting diode and a receiving diode, while the other comprises a colored LED and / or a polarization filter. Preferably, two transmitting diodes and one receiving diode are provided, or one transmitting diode and two receiving diodes, wherein in the latter case a polarization filter can be connected upstream of the second receiving diode, or the second receiving diode can be designed as a backscatterer, which may have a polarization filter connected upstream. The polarization filter can also be arranged between the transmitting diode and the measuring chamber of the optical smoke detector.

[0011] A fire alarm system is known from the German publication DE 44 15 063 A1, which has a first light emitting element, a first polarization filter, a first light receiving element, a second light emitting element, a second polarization filter and a second light receiving element. With the aid of such a device, the value of the component polarized parallel to the scattering plane and the value of the component polarized perpendicular to the scattering plane are determined. The ratio between these values ​​of light is related to the type of smoke. The calculation section calculates the ratio from the output signal of the light receiving element. The decision section compares the ratio with a previously determined reference value corresponding to the type of smoke to be identified, wherein the decision as to whether it is a fire depends on the type of smoke. Therefore, taking into account the type of smoke, a fire can be identified based on the light scattered by the smoke.

[0012] From the German publication DE 10 2015 117 361 A1, a device for identifying aerosols is known, wherein the device measures light scattered at the aerosol by means of at least one light detection device in a specific angular configuration. The device calculates a polarization measure from the detection signal of the at least one light detection device by means of a measuring and computing device, and in a specific embodiment, calculates the degree of depolarization. Based on the value of the polarization measure, small water droplets can be clearly distinguished from aerosols that arise due to fire. Based on the value of the degree of depolarization, dust particles can be clearly distinguished from aerosols that arise due to fire. The scattered light measurement is performed at an angle of 35° (corresponding to a backscattering angle of 145°), or at two angles (5°, 95°).

[0013] In the scientific publication by M. Loepfe et al.: "Optical Properties of Fire and Non-fire Aerosols" (which appeared in "Fire Safety Journal, 29 (1997) 185-194"), the polarization of test fires and interfering parameters such as water in the angular range of 0° to 180° was investigated. From the described light scattering experiments related to angle and polarization, the aerosols of the EN54 test fire can be divided into three groups based on the polarization of their scattered light: TF1, TF4 and TF5 form relatively small particles that have weak scattering in the visible and near infrared ranges, but have a high polarization degree P = 0.9 measured at a wavelength of 690 nm and at an angle of 90°. TF3 produces an aerosol composed of medium-sized particles with a polarization degree P = 0.3 at 90°. TF2 produces an aerosol of large particles with a polarization degree P = -0.1 at 90°. Water vapor, ie, interfering non-fire aerosol, is distinguished from the above-mentioned fire aerosol by a characteristic angular dependence of the degree of polarization, in particular in an angular range of approximately 150°. Summary of the invention

[0014] Based on the prior art mentioned at the outset, it is the object of the present invention to specify an improved scattered-light smoke detector having (only) one bicolor LED and having (only) one photoelectric sensor.

[0015] A further object of the present invention is to specify a suitable use of a polarizer for optical scattered-light smoke detection according to the two-color principle.

[0016] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0017] It is assumed below that the light of the two wavelengths λ1, λ2 emitted by the bicolor LED is unpolarized, i.e. has a degree of polarization of 0 or approximately 0 (<0.05). The degree of polarization or polarization measure is defined as the quotient of the difference between two radiation intensities and the sum of the two radiation intensities. By definition, the difference between two radiation intensities refers to the value of the difference. In addition, the degree of polarization or polarization measure is dependent on the respective wavelength of the light.

[0018] For the following considerations, the following definitions are given:

[0019] The scattering plane (also scattered light plane) is a plane spanned by the optical axes of at least one light emitting diode (LED) or a two-color LED and at least one photosensor.

[0020] -The polarizer plane is the plane of the flat plate or film-like polarizer.

[0021] The polarization plane is a plane determined by the propagation direction in time and the oscillation direction of the light. If a polarizer includes such a polarization plane, this means that, for light incident perpendicularly on the polarizer plane, only the polarization component parallel to the included polarization plane passes through the polarizer. The polarization plane included by the polarizer is therefore orthogonal to the polarizer plane.

[0022] The polarization direction always lies in the polarizer plane and is either parallel or perpendicular to the scattering plane.

[0023] If the polarizer is optically connected downstream of the bicolor LED, the polarizer plane of the polarizer is oriented at an angle of 90°+ / -5° relative to the optical axis of the bicolor LED, preferably normal (orthogonal) to the optical axis of the bicolor LED. If the polarizer is optically connected upstream of the photosensor, the polarizer plane of the polarizer is oriented at an angle of 90°+ / -5° relative to the optical axis of the photosensor, preferably normal (orthogonal) to the optical axis of the photosensor.

[0024] The bicolor LED is an integrated or one-piece optoelectronic device, in other words a structural unit. Such a bicolor LED is preferably a light-emitting diode with a transparent (standard) housing, the housing having a diameter of 3 mm or 5 mm. Such 3 mm or 5 mm light-emitting diodes are known to be sold "off the shelf" as a large number of consumer products. Alternatively, the bicolor LED can also be implemented as an SMD component for surface mounting. Preferably, the bicolor LED is configured to emit only light of the first and / or second wavelength λ1, λ2 as monochromatic light of the first and / or second wavelength λ1, λ2.

[0025] According to the invention, the scattered light smoke detector has a polarizer, which is optically connected upstream of the photoelectric sensor or optically connected downstream of the two-color LED. The polarizer has such optical properties that the light passing through the polarizer is polarized or can be polarized differently strongly depending on its respective wavelength λ1, λ2. Such a polarizer is also called a polarization filter or polarization filter. The polarizer is preferably a linear polarizer. The light passing through the polarizer here either comes directly from the two-color LED or the light is scattered light of the particles to be detected in the scattered light volume, which is illuminated or irradiated by the two-color LED. The scattered light volume is geometrically or constructively defined as the intersection volume of the emitted light beam of the two-color LED and the optical receiving sector of the respective photoelectric sensor.

[0026] The core of the invention is to combine the principle of two-color scattered light with polarization-dependent scattering of light at the particles. This combination leads in a particularly advantageous manner to a reliable distinction between open flames, smoldering fires and water for suitable scattering angles. Here, for suitable scattering angles, the two-color principle, which enables a reliable separation between open flames and water, and the polarization-dependent scattering, which enables a reliable separation between open flames and smoldering fires, complement each other.

[0027] The possible differentiation criteria of the invention include not only the wavelength dependence of the light scattering at the particles (aerosols) to be detected according to the two-color principle but also the polarization effects caused by the scattering at the aerosols. By appropriately selecting the polarization direction for the first wavelength λ1, the ability to distinguish different aerosol classes by the two wavelengths λ1, λ2 can be increased.

[0028] According to the invention, this is achieved by a very simple scattered light device as part of a scattered light smoke detector, wherein the scattered light device comprises (only) one bicolor LED and one (1-channel) photoelectric sensor as well as a polarizer, which acts in a wavelength-selective manner with respect to the light of the bicolor LED. In this case, for a suitable scattering angle, the wavelength-selective polarization results in two scattered radiation intensities I λ1 ,I λ2 The ratio of the blue / red or red / blue ratio, i.e. a change or shift in the blue / red or red / blue ratio, is also caused in such a way that a reliable separation of the open fire from the smoldering fire (TF2) is possible (see in this regard the exemplary case of a scattering angle of 90°). Figure 5 The ratio Q1s in the equation is

[0029] This allows the alarm times for open fires and TF2 smoldering fires to be better adapted to the respective fire severity.

[0030] exist Figure 5In the example of FIG. 1 , the first quotient Q1s is the scattered radiation intensity I of the linearly polarized first “blue” wavelength of the respective photosensor signal at the same scattering angle of 90°. λ1 The intensity of the scattered radiation I with the unpolarized second “red” wavelength λ2 λ2 In this example, the polarization plane of the polarizer runs perpendicular to the scattering plane. The latter is determined by the optical axes of the bicolor LED and the photosensor.

[0031] Due to the wavelength-selective effect of the polarizer, two separate single-color LEDs (light-emitting diodes) are not required for the first and second wavelengths, as is the case in the case of the scattered light device according to German publication DE 10 2015 117 361 A1. Since according to the invention, two LED chips with mutually different wavelengths are now used in a single LED housing, the number of components is advantageously reduced. The wavelength-selective polarizer is then optically connected downstream of the LED housing or optically connected upstream of the photoelectric sensor. In addition to saving components, residual errors are also advantageously reduced after calibrating the light path in the detection unit. Typically, when installing two separate light-emitting diodes, greater relative deviations from each other in terms of orientation and placement are obtained compared to the case of a two-color LED.

[0032] In addition to the lower installation effort associated therewith, a further advantage lies in particular in the significantly reduced alignment effort of the beam path in the case of the scattered light device according to the invention.

[0033] Another great advantage is that by using a two-color LED, almost the same scattered light volume and thus also almost the same particles to be detected are illuminated along essentially the same light path. Therefore, geometrically the scattered light volume is determined only by the two-color LED and the receiver, which is advantageously much more accurate than two overlapping scattered light volumes defined by a single monochromatic LED and a single receiver. The measurement errors caused by the deviated optical axis, as is the case in DE 10 2015 117 361 A1 when using two separate adjacent LEDs, do not occur here or are negligible.

[0034] According to one embodiment, the polarizer has such optical properties that light of a first wavelength λ1 passing through the polarizer is at least partially polarized, while light of a second wavelength λ2 passing through is substantially unpolarized. Thus, depending on the scattering angle, a particularly effective separation of an open flame from a smoldering fire is possible.

[0035] In particular, the polarizer has such optical properties that light of the second wavelength λ2 passing through the polarizer or light of the second wavelength λ2 passing through the polarizer with unpolarized incidence has a polarization degree of maximum 0.05. This value of 0.05 for the degree of polarization means here that the light of the second wavelength λ2 passing through is polarized by maximum 5% and the polarizer is more or less transparent for the light of the second "red" wavelength λ2. In other words, the polarizer is more or less transparent regardless of the polarization state of the light.

[0036] Therefore, the polarizer acts as a polarizer only for one of the two wavelengths λ1, while the other wavelength λ2 is transmitted without selecting the polarization direction.

[0037] According to another embodiment, the polarizer comprises a polarization plane, i.e., the polarizer forms a polarization plane. The polarizer further has such optical properties that at least 50%, in particular at least 80%, of the light of the first wavelength λ1 polarized parallel to the polarization plane of the polarizer passes through the polarizer. However, only at most 5%, in particular at most 1%, of the light of the first wavelength λ1 polarized perpendicularly to the polarization plane of the polarizer passes through the polarizer. In other words, the polarizer is more or less transparent to the light portion of the first "blue" wavelength λ1 polarized parallel to the polarization plane of the polarizer, and more or less opaque to the "blue" light portion perpendicular thereto.

[0038] According to a particularly advantageous embodiment, the polarizer is a wavelength-selective linear polarizer.

[0039] The polarizer is preferably a polarizer made of a polymer film, in particular a polyvinyl alcohol film (PVA) with, for example, permeable iodine. The polarizer can be, for example, a mechanically stretched polyvinyl alcohol film for orienting the polymer chains with embedded, in particular thermally stable pigments. Such a PVA film is preferably protected on both sides by a triacetylcellulose layer.

[0040] Such linear polarizers are known from the field of LCD display technology, even if for completely different purposes. They are spectrally designed according to the sensitivity of the human eye in the wavelength range of approximately 400 to 700 nm. Well-known manufacturers of such polarizers are, for example, Bolder Vision Optik Inc. with the polarizer type "BVO244", Edmund Optics GmbH with the polarizer type "TECHSPEC High Conrast Plastic Linear Polarizer" (Art. #86-187), Nitto Deutschland GmbH with the polarizer type "SEG1425DU" or Polatechno Co. Ltd with the polarizer type "EHC-125U".

[0041] Polarizers available from the above-mentioned companies are available as plastic films (e.g. 100 mm×100 mm) with a typical thickness of less than 1 mm. This film can be cut in a simple manner, for example, into polarizers according to the invention having dimensions of 5 mm×5 mm to 10 mm×10 mm. The cut films can be circular, rectangular or square.

[0042] Alternatively, wire grid polarizers or so-called dye-type polarizers can also be used as wavelength-selective linear polarizers.

[0043] Alternatively to the aforementioned wavelength-selective linear polarizer, the following polarizer can also be used: the polarizer comprises: a linear polarizer of planar construction that polarizes approximately equally strongly for the two emitted wavelengths λ1, λ2 of the bicolor LED and an optical delay plate adjacent thereto in a planar manner. The delay plate comprises an outer surface opposite to the surface adjacent to the linear polarizer. The outer surface of the delay plate as part of the polarizer is oriented to the common scattered light volume. The polarizer is optically connected upstream of the photosensor or optically connected downstream of the bicolor LED.

[0044] The retardation plate causes a phase shift between the two polarization components of the light passing through the plate. The phase shift depends on the birefringence ∆n of the material of the retardation plate and on its thickness d. The resulting optical retardation R is therefore ∆n*d. The optical retardation R of the retardation plate is coordinated with the second wavelength λ2 of the emitted LED light, for example with a wavelength of 940 nm, so that the retardation plate acts as a λ / 4 plate for the second wavelength λ2. The LED light that strikes the smoke particles to be detected is polarized by these smoke particles. The retardation plate acts on this scattered polarized light as follows: By scattering at the scattering particles, the linearly polarized light is polarized in a circular manner after passing through the retardation plate. Only one of the two polarization components of the circularly polarized light is able to pass through the subsequent linear polarizer. If the scattering at the scattering particles does not polarize the light, the retardation plate has no effect. Even in this case, only one of the two polarization components of the non-polarized light can pass through the linear polarizer. All in all, the arrangement consisting of the retardation plate and the subsequent polarizer acts as if the non-polarized light would strike the photosensor, but with a signal loss of 50%. For example 470nm = • For light of a first wavelength λ1 of 940 nm, the retardation plate acts, for example, as a λ / 2 plate, which rotates the polarization direction by 90°. Compared to the previous embodiment with a wavelength-selective linear polarizer, the polarization plane of the wavelength-independent polarizer is rotated by 90° here.

[0045] According to one embodiment, the bicolor LED is arranged at a first scattering angle of 45° to 135°, in particular 60° to 120° and preferably 90°±5° relative to the photosensor. The bicolor LED and the photosensor are oriented to a common scattered light volume. The polarizer is a linear polarizer. The polarizer is optically connected either upstream of the photosensor or downstream of the bicolor LED. Typically, the polarizer optically connected upstream of the photosensor or the polarizer optically connected downstream of the bicolor LED is arranged orthogonal to the optical axis of the photosensor or the bicolor LED. The polarizer is preferably oriented so that its polarization plane encloses an angle of 90°±5° with the scattering plane spanned by the optical axes of the bicolor LED and the photosensor. Therefore, with respect to the scattering plane, the polarizer is a <<vertical>> polarizer. When the scattering angle between the bicolor LED and the photosensor is at 90° and when the polarization plane of the polarizer extends perpendicular to the scattering plane, a particularly reliable measurement result is obtained.

[0046] According to an advantageous embodiment of this, the control unit is designed to generate a scattering angle of 90°±5° between the two-color LED and the photosensor from the two scattered radiation intensities I λ1 ,I λ2 The first quotient Q1s is determined in the control unit. The control unit is configured to output a fire alarm or a smoldering fire alarm if the first quotient Q1s is within the first or second quotient range. The first quotient range is coordinated with the test fire TF2 (smoldering fire, pyrolytic smoldering fire), while the second quotient range is coordinated with the test fire TF3 (smoldering fire, smoldering cotton). Since large smoke may be expected, by outputting a specific smoldering fire alarm, it is possible to facilitate preparatory measures for extinguishing the fire. It is therefore advantageously possible to distinguish between an open flame and a smoldering fire.

[0047] Alternatively, the control unit can be set up to output a fire alarm or a fire alarm for an open fire if the first quotient Q1s is within a third quotient range. The third quotient range is coordinated with a test fire for an open fire. Since in this case, with a few exceptions (test fire TF8, decalin fire), high temperatures can be expected on site, preparatory measures for extinguishing the fire can be advantageously taken by outputting a specific fire alarm for an open fire.

[0048] According to another embodiment, the control unit can be configured to obtain the following information from two scattered radiation intensities I λ1 ,I λ2 The first quotient Q1s is determined in the fourth quotient range, and can be set up to prevent the output of a fire alarm and / or output a warning message for the detected "water" in the scattered light volume if the first quotient Q1s is within a fourth quotient range. The fourth quotient range is coordinated with the presence of water vapor or water mist or indicates the presence of water vapor or water mist. The output of possible false alarms can be prevented thereby.

[0049] In particular, the following generally applies to the respective value ranges of the previously mentioned quotient ranges: quotient of the fourth quotient range "water vapor" < quotient of the first quotient range "pyrolytic smoldering fire" < quotient of the second quotient range "smoldering cotton fire" < quotient of the third quotient range "open flame". This means qualitatively that the larger the quotient value, the smaller the detected particles.

[0050] For according to Figure 5 In the example of, the first quotient range includes values ​​of 1.4±0.2, in particular 1.4±0.15 for the first quotient Q1s. The second quotient range includes values ​​of 3±0.5, in particular 3±0.4, for the first quotient Q1s. The third quotient range includes values ​​of 5±1.3, in particular 5±1.25, for the first quotient Q1s. The fourth quotient range includes values ​​of 0.5±0.15, in particular 0.5±0.1, for the first quotient Q1s. The values ​​of the respective quotient ranges depend on the scattering angle and on the orientation of the polarization plane of the polarizer.

[0051] According to updated measurement technology studies, the first quotient range includes values ​​of 1.35±0.2 for the first quotient Q1s. The second quotient range includes values ​​of 2±0.5. The third quotient range includes values ​​of 5±1.6. The fourth quotient range includes values ​​of 0.6±0.2. Here, the values ​​of the respective quotient ranges are again dependent on the scattering angle and on the orientation of the polarization plane of the polarizer.

[0052] Note that instead of the previous quotient range, the respective reciprocal can also be determined. In this case, the respective values ​​for the quotient range have the reciprocal. In addition, the comparison operators (such as less than or greater than) are also opposite.

[0053] It should also be noted that the previously mentioned quotient ranges are determined in terms of measurement technology at a scattering angle of 90° and a perpendicular polarization plane. In general, as the scattering angle value decreases, the quotients Q1s of the test fires TF2, TF3 and water vapor H2O move towards each other, wherein the distance between them decreases. As the scattering angle value increases, the quotients Q1s of the test fire TF2 and water vapor H2O on the one hand and the quotients Q1s of the test fire TF3 and the open flame OF on the other hand come very close.

[0054] According to another embodiment, the scattering angle between the two-color LED and the photosensor is 90°±5°. The polarization plane of the polarizer extends parallel to the scattering plane. The latter is determined by the optical axes of the two-color LED and the photosensor. The control unit is configured to obtain the scattered radiation intensities I λ1 ,I λ2The second quotient Q2p is determined in the control unit. The control unit is configured to output a fire alarm if the second quotient Q2p is within another first quotient range or another second quotient range. Here, another first quotient range is coordinated with an open flame OF, and another second quotient range is coordinated with test fires TF2 and TF3 (smoldering fire, pyrolytic smoldering fire). If the second quotient Q2p is within another first quotient range, the control unit may alternatively or additionally be configured to output a specific open flame. Alternatively or additionally, if the second quotient Q2p is within another second quotient range, the control unit may be configured to output a specific smoldering fire alarm.

[0055] In the present case, however, a distinction between an open flame OF and water vapor is not possible, since in the presence of water vapor or water mist the second quotient Q2p approximately includes values ​​of the other first quotient range.

[0056] According to another embodiment, the scattering angle between the two-color LED and the photosensor, i.e. the second scattering angle, is 142°±5°, preferably 142°±1°. Light scattered at water vapor or mist in this angle range is strongly polarized, as in the case of a rainbow. The polarization plane of the polarizer extends parallel to the scattering plane. The polarizer is therefore a <<parallel>> polarizer with respect to the scattering plane. The latter is determined by the optical axes of the two-color LED and the photosensor. The control unit is set up to generate a polarization signal from the two scattered radiation intensities I λ1 ,I λ2 The third quotient Q3p is determined in the control unit. The control unit is configured to output a fire alarm if the third quotient Q3p is within a further second quotient range. Here, the further first quotient range is coordinated with the presence of water vapor H2O, and the further second quotient range is coordinated with the test fires TF2 and TF3 (smoldering fire, pyrolytic smoldering fire) and the open flame OF. In the present case, it is possible to reliably detect fire. At the same time, it is possible to reliably distinguish between the presence of fire and water vapor. In other words, it is possible to reliably identify water vapor and thereby suppress interference.

[0057] According to another embodiment, the bicolor LED is arranged at a second scattering angle of 142°±5°, preferably 142°±1°, relative to the photosensor. The second scattering angle can also be referred to as a backscattering angle because it is significantly greater than 90°. The bicolor LED and the photosensor are oriented to a common scattered light volume. The polarizer is a linear (wavelength selective) polarizer. The polarizer is optically connected either upstream of the photosensor or downstream of the bicolor LED. The polarizer is oriented so that its polarization plane encloses an angle of 0°±5°, preferably 0° with the scattering plane spanned by the optical axes of the bicolor LED and the photosensor. In other words, the polarization plane extends parallel to the spanned scattering plane.

[0058] Light scattered at the second scattering angle at water vapor or water mist is strongly polarized, as in the case of a rainbow. Therefore, in the case of such water phenomena, the third quotient Q3p is shifted more strongly into the interference variable range, i.e. towards "large particles" such as dust, compared to scattered light devices without polarization filters.

[0059] According to one embodiment, the control unit is configured to extract from the two scattered radiation intensities I λ1 ,I λ2 The control unit is further configured to prevent the output of a fire alarm and / or a warning message for the detected water vapor or water mist in the scattered light volume if the third quotient Q3p is within a further first quotient range. The further first quotient range can be determined, for example, by measurement technology.

[0060] According to an advantageous embodiment, the scattered light smoke detector has a first and a second photoelectric sensor, instead of just one photoelectric sensor, which have a first and a second polarizer optically connected upstream, which polarize the respective light passing through differently strongly according to its respective wavelength λ1, λ2. The bicolor LED is arranged at a first scattering angle of 45° to 135°, in particular 60° to 120° and preferably 90°±5° relative to the first photoelectric sensor. The bicolor LED is also arranged at a second scattering angle of 142°±5°, preferably 142°±1°, relative to the second photoelectric sensor. The bicolor LED and the two photoelectric sensors are oriented to a common scattered light volume. The control unit is especially connected to the bicolor LED and the two photoelectric sensors in terms of signal and / or data technology, and is configured to control the bicolor LED to emit light of the first or second wavelength λ1, λ2. The control unit is also configured to detect a photoelectric sensor signal of each of the two photoelectric sensors, and to determine the first and second scattered radiation intensities I for the first and second wavelengths λ1, λ2 based on the respective photoelectric sensor signals. λ11 ,I λ12 ;I λ21 ,I λ22 And in the case of a fire alarm, the respective first and second scattered radiation intensities I are taken into account together λ11 ,I λ12 ;I λ21 ,I λ22 .

[0061] The scattered light volume is geometrically or constructively defined as the intersection volume of the emitted light beam of the bicolor LED and the optical receiving sector of the respective photosensor.

[0062] According to an alternative embodiment to the previous embodiment, the scattered light smoke detector has a first and a second photoelectric sensor instead of one photoelectric sensor. The bicolor LED is arranged at a first scattering angle of 45° to 135°, in particular 60° to 120° and preferably 90°±5° relative to the first photoelectric sensor. In addition, the bicolor LED is arranged at a second scattering angle of 142°±5°, preferably 142°±1°, relative to the second photoelectric sensor. The bicolor LED and the two photoelectric sensors are oriented to a common scattered light volume. A polarizer is optically connected downstream of the bicolor LED, which polarizes the light emitted by the bicolor LED that passes through each light differently according to its respective wavelength λ1, λ2. The control unit is connected to the bicolor LED and the two photoelectric sensors, in particular in terms of signal and / or data technology, and is set up or programmed to control the bicolor LED to emit light of the first or second wavelength λ1, λ2, detect a photoelectric sensor signal of each of the two photoelectric sensors, and determine the first and second scattered radiation intensities I for the first and second wavelengths λ1, λ2 based on the respective photoelectric sensor signals. λ11 ,I λ12 ;I λ21 ,I λ22 And in the case of a fire alarm, the respective first and second scattered radiation intensities I are taken into account together λ11 ,I λ12 ;I λ21 ,I λ22 .

[0063] Compared to the previous embodiments, here advantageously only a single wavelength-selective polarizer is required instead of two wavelength-selective polarizers. In addition, the distance between the open flame and the smoldering fire is increased. Furthermore, the construction is simplified.

[0064] Instead of the two previous embodiments, the scattered light detector can have a first and a second bicolor LED, instead of only one bicolor LED, the first and second bicolor LEDs having a first and a second polarizer optically connected downstream, the first and second polarizers polarize the light passing through each according to its respective wavelength λ1, λ2 differently and strongly. Relative to the previous embodiment, the scattered light device can be regarded as a double scattered light device. The photoelectric sensor is arranged at a first scattering angle in the range of 45° to 135°, especially from 60° to 120° and preferably from 90°±5° relative to the first bicolor LED. In addition, the photoelectric sensor is arranged at a second scattering angle of 142°±5°, preferably 142°±1° relative to the second bicolor LED. The photoelectric sensor and the two bicolor LEDs are oriented to a common scattered light volume. The control unit is connected to the photoelectric sensor and the two bicolor LEDs, especially in terms of signal and / or data technology. The control unit is further configured to control the two bicolor LEDs to emit light of the first or second wavelength λ1, λ2, respectively, to detect a photosensor signal of the photosensor, and to determine a first and a second scattered radiation intensity I for the first and second wavelength λ1, λ2, respectively, based on the bicolor LEDs respectively controlled. λ11 ,I λ12 ;I λ21 ,I λ22 And in the case of a fire alarm, the respective first and second scattered radiation intensities I are taken into account together λ11 ,I λ12 ;I λ21 ,I λ22 .

[0065] According to another embodiment that replaces the previous embodiment, the scattered light smoke detector according to the present invention has a first and a second bicolor LED instead of one bicolor LED. The photoelectric sensor is arranged at a first scattering angle in the range of 45° to 135°, in particular from 60° to 120° and preferably 90°±5° relative to the first bicolor LED. In addition, the photoelectric sensor is arranged at a second scattering angle of 142°±5°, preferably 142°±1° relative to the second bicolor LED. The photoelectric sensor and the two bicolor LEDs are oriented to a common scattered light volume. A polarizer is optically connected upstream of the photoelectric sensor, and the polarizer polarizes the light passing through each according to its respective wavelength λ1, λ2 with different intensity. The control unit is connected to the photoelectric sensor and the two bicolor LEDs, in particular in terms of signal and / or data technology. The control unit is set up or programmed to control the two bicolor LEDs to emit light of the first or second wavelength λ1, λ2, respectively, detect the photoelectric sensor signal of the photoelectric sensor, and determine the first and second scattered radiation intensities I for the first and second wavelengths λ1, λ2, respectively, based on the bicolor LEDs respectively controlled. λ11 ,I λ12 ;Iλ21 ,I λ22 And in the case of a fire alarm, the respective first and second scattered radiation intensities I are taken into account together λ11 ,I λ12 ;I λ21 ,I λ22 .

[0066] Compared to the previous embodiments, here too, only a single wavelength-selective polarizer is advantageously required instead of two wavelength-selective polarizers. In addition, the distance between the open flame and the smoldering fire is increased. This simplifies the design.

[0067] The four aforementioned embodiments allow a combined evaluation in the context of a multi-criteria smoke detector, in particular with regard to water vapor or water mist as a disturbance variable when detecting fire, with a higher degree of safety against false alarms.

[0068] According to another embodiment, in the two previous embodiments with two polarizers, the first and second polarizers are linear (wavelength selective) polarizers. The first polarizer is oriented so that its polarization plane encloses an angle of 90°±5° with the scattering plane spanned by the optical axes of the (one or more) bicolor LEDs and the multiple photosensors or one photosensor. The second polarizer is oriented so that its polarization plane encloses an angle of 0°±5° with this plane.

[0069] In the case of a diffuse light arrangement with a single bicolor LED and with two photosensors, a first "perpendicular" polarizer is optically connected upstream of the photosensor, which are arranged at an angle of 90°±5° relative to the bicolor LED. Correspondingly, a second "parallel" polarizer is connected upstream of the remaining photosensor (see Fig. 9 ). In the other "double" case, a first "perpendicular" polarizer is optically connected downstream of the bicolor LED arranged at an angle of 90°±5° relative to the single photosensor. Correspondingly, a second "parallel" polarizer is connected downstream of the remaining bicolor LED (see Fig.11 ).

[0070] According to another embodiment, in the two previous embodiments with a single polarizer, the polarizer is a linear (wavelength selective) polarizer. The latter is oriented such that its polarization plane encloses an angle of 0°±5° with the scattering plane spanned by the optical axis of the bicolor LED or photosensor.

[0071] According to another embodiment, namely at a first scattering angle (90°±5°) and with the polarization plane of the respective polarizer oriented perpendicularly to the scattering plane, the control unit is preferably configured to generate a first scattered radiation intensity I assigned to the first scattering angle from the second scattered radiation intensity I λ1 ,I λ2The first quotient Q1s is determined from the first and second scattered radiation intensities I assigned to the second scattering angle λ1 ,I λ2 The third quotient Q3p is determined in the control unit. The control unit is further configured to output a fire alarm and / or a smoldering fire alarm if the first quotient Q1s is within the first or second quotient range, or to output a fire alarm and / or a fire alarm for an open flame if the first quotient Q1s is within the third quotient range. In addition, the control unit is configured to prevent the output of a fire alarm and / or a warning message for the detected water vapor or water mist in the scattered light volume if the first quotient Q1s is within the fourth quotient range and / or the third quotient Q3p is within another first quotient range. In particular, the control unit is configured to prevent the output of a fire alarm and / or a warning message for the detected water vapor or water mist in the scattered light volume if the first quotient Q1s is within the fourth quotient range and at the same time the third quotient Q3p is within another first quotient range. This advantageously improves false alarm safety.

[0072] According to another embodiment, namely at a first scattering angle (90°±5°) and with the polarization plane of the respective polarizer oriented parallel to the scattering plane, the control unit is preferably configured to generate a first scattered radiation intensity I assigned to the first scattering angle from the second scattered radiation intensity I λ1 ,I λ2 The second quotient Q2p is determined from the first and second scattered radiation intensities I assigned to the second scattering angle λ1 ,I λ2 The third quotient Q3p is determined in the scattered light volume. The control unit is further configured to output a fire alarm and / or a smoldering fire alarm if the second quotient Q2p is within another second quotient range, or to output a fire alarm if the third quotient Q3p is within another second quotient range. In addition, the control unit is configured to prevent the output of a fire alarm and / or a warning message for the detected water vapor or water mist in the scattered light volume if the second quotient Q2p is within another first quotient range and / or the third quotient Q3p is within another first quotient range. In particular, the control unit is configured to prevent the output of a fire alarm and / or a warning message for the detected water vapor or water mist in the scattered light volume if the second quotient Q2p is within another first quotient range and at the same time the third quotient Q3p is within another first quotient range. This advantageously improves false alarm safety.

[0073] According to one embodiment, the bicolor LED is designed to emit light at a first wavelength λ1 in the range of 380 nm to 570 nm, in particular 470 nm±30 nm, and to emit light at a second wavelength λ2 in the range of 750 nm to 1100 nm, in particular 940 nm±30 nm.

[0074] The photosensor is in particular a semiconductor photodiode, in particular a silicon PIN photodiode. Preferably, the photosensor is a silicon PIN photodiode with improved blue sensitivity in the first wavelength range. Alternatively, the photosensor can also be a phototransistor.

[0075] According to another embodiment, the control unit is configured to control the two-color LED for emitting pulsed light of the first wavelength λ1 or the second wavelength λ2. Typically, the light pulses of the first or second wavelength λ1, λ2 are repeatedly, in particular periodically, irradiated into the scattered light volume by controlling the light pulses by means of the control unit, for example with a repetition frequency in the range of 0.1 to 5 Hz. The pulse duration is preferably in the range of 20 μs to 1 ms.

[0076] Preferably, as long as the associated scattered radiation intensity I λ1 To keep below a minimum scattered light level, only light pulses of the first wavelength λ1 are repeatedly, in particular periodically, irradiated into the scattered light volume. This minimum scattered light level is only exceeded when a sufficient concentration of smoke particles, dust or steam enters the scattered light volume. Then, light pulses of the second wavelength λ2 are additionally irradiated into the scattered light volume, so that the particle size or a size comparable to the particle size can be determined by means of the control unit based on the two-color principle for determining the type of particles in the scattered light volume. In this case, light pulses of the first and second wavelengths λ1, λ2 are alternately irradiated into the scattered light volume by means of appropriate pulsed control of the two-color LED by the control unit.

[0077] This advantageously results in a particularly energy-saving operating mode of the smoke detector, since, averaged over the operating time, only infrequent further light pulses of the second wavelength λ2 have to be radiated into the scattered light volume.

[0078] According to a further embodiment, the control unit is configured to normalize the first and second scattered radiation intensities I assigned to the first scattering angle as follows: λ1 ,I λ2 , so that for scattering particles introduced into the scattered light volume with a predetermined average diameter in the range of 0.5 to 1.5 μm, the first quotient Q1s and / or the second quotient Q2p has a quotient value in the range of 1 to 3, in particular a quotient value of 2. Alternatively or additionally, the control unit is configured to normalize the first and second scattered radiation intensities I assigned to the second scattering angle as follows λ1 ,I λ2 , so that for scattering particles introduced into the scattered light volume with a predetermined average diameter in the range of 0.5 to 1.5 μm, the third quotient Q3p has a quotient value in the range of 1 to 3, in particular a quotient value of 2.

[0079] According to the invention, in the case of optical scattered light smoke detection according to the two-color principle, a (wavelength-selective) polarizer can be used particularly advantageously. In this case, the two-color, in particular monochromatic, light emitted for optical smoke detection at the first and second wavelengths λ1, λ2 is polarized to different degrees by means of the polarizer.

[0080] The polarizer has such optical properties that the light passing through it is polarized differently strongly depending on its respective wavelength λ1, λ2. Preferably, the polarizer is a linear polarizer having such optical properties that the light of the second wavelength λ2 passing through it, i.e. the light of the second wavelength λ2 incident unpolarized, passing through the linear polarizer has a polarization degree of maximum 0.05. This means that the polarizer is more or less transparent for the light of the second "red" wavelength λ2. In other words, the linear polarizer is more or less transparent regardless of the polarization state of the light.

[0081] The polarizer acts as a polarizer essentially only for one of the two wavelengths λ1. The other wavelength λ2 is passed without selecting the polarization direction. The polarizer has such optical properties that at least 50%, in particular at least 80%, of the light of the first wavelength λ1 polarized parallel to the polarization plane of the polarizer passes through the polarizer. However, only at most 5%, in particular at most 1%, of the light of the first wavelength λ1 polarized perpendicularly to the polarization plane of the polarizer passes through the polarizer. Therefore, the polarizer is more or less transparent to the light portion of the first wavelength λ1 parallel to the polarization plane of the polarizer, and more or less opaque to the light portion perpendicular thereto.

[0082] The scattered light smoke detector according to the invention has in particular a processor-assisted control unit, which is connected to at least one of the two bicolor LEDs and to at least one of the two photoelectric sensors. In addition, the control unit has at least an output device for a fire alarm or a warning message. The control unit also has an electronic memory, which can be loaded with a computer program. Here, the computer program includes appropriate instructions for optical fire detection that can be executed by the processor-assisted control unit. The processor-assisted control unit is preferably a microcontroller. Such a microcontroller typically has a series of integrated hardware functional units, such as an analog / digital converter, a digital / analog converter, a timer, a digital input / output unit and a bus interface, in particular as an output device for a fire alarm or a warning message.

[0083] Such a scattered light smoke detector usually has a detector housing with at least one smoke inlet opening. Such a scattered light smoke detector preferably comprises an optical measuring chamber which is shielded from ambient light but is transparent to the smoke to be detected. The optical measuring chamber comprises at least one two-color LED and at least one photoelectric sensor for use in a scattered light device for optical smoke detection according to the invention. The optical measuring chamber usually has a large number of sheets shielding from ambient light and is therefore also referred to as a labyrinth.

[0084] Alternatively, the scattered light smoke detector can be a so-called open scattered light smoke detector. In this case, the scattered light smoke detector does not have a labyrinth. Rather, the respective bicolor LED and the respective photoelectric sensor are then arranged in the detector housing. The bicolor LED and the photoelectric sensor are also arranged in a scattered light arrangement with a scattered light volume outside the detector housing and thus with a scattered light volume outside the entire scattered light smoke detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The present invention and its advantageous implementation are explained by way of example in the following figures.

[0086] Figure 1 A diffuse light device with a two-color LED and a photoelectric sensor according to the prior art is shown.

[0087] Figure 2 A further scattered light device according to the prior art is shown, which has two monochromatic LEDs, has a polarizer connected downstream of one of the two LEDs, and has a photosensor,

[0088] Figure 3 An exemplary scattered light device according to the invention having a bicolor LED, having a photosensor and having a wavelength selective polarizer connected upstream of the photosensor is shown,

[0089] Figure 4 An example of a bicolor LED is shown, which has two LED chips arranged adjacent to each other on a chip carrier of the bicolor LED,

[0090] Figure 5 Shows the quotient Q of vertically polarized infrared light and unpolarized infrared light 01 , About the quotient of unpolarized blue light and unpolarized infrared light 02 and exemplary distributions of test fires, open flames and interference parameters plotted according to the first quotient Q1s of vertically polarized blue light and non-polarized infrared light, according to the second quotient Q2p of parallel polarized blue light and non-polarized infrared light at a scattering angle of 90°, and according to the third quotient Q3p of parallel polarized blue light and non-polarized infrared light at a polarization angle of 142°,

[0091] Figure 6 An exemplary scattered light device according to the invention having a bicolor LED, having a photosensor and having a wavelength selective polarizer connected downstream of the bicolor LED is shown,

[0092] Figure 7 An exemplary backscattered light device consisting of a bicolor LED, a photosensor, and a wavelength selective polarizer connected downstream of the bicolor LED according to the present invention is shown,

[0093] Figure 8 An exemplary backscattered light device according to the present invention consisting of a bicolor LED, a photosensor, and a wavelength selective polarizer connected upstream of the photosensor is shown,

[0094] Fig. 9 An exemplary combined scattered light device according to the invention is shown, consisting of a common two-color LED, a first photosensor and a second photosensor, each with an upstream wavelength-selective polarizer,

[0095] Fig.10 It is shown that according to the present invention Fig. 9 Embodiments of alternative embodiments,

[0096] Fig.11 shows an exemplary combined scattered light device according to the invention consisting of a common photosensor, a first bicolor LED and a second bicolor LED, each with a wavelength-selective polarizer connected downstream,

[0097] Fig.12 It is shown that according to the present invention Fig.11 Embodiments of the invention In alternative embodiments,

[0098] Fig.13 An example of an electronic control unit for a diffuse light smoke detector according to the invention for connection to (only) one bi-color LED and two photoelectric sensors is shown, and

[0099] Fig.14 An example of another electronic control unit for connection to a photoelectric sensor and a bi-color LED is shown for a scattered light smoke detector according to the present invention. DETAILED DESCRIPTION

[0100] Figure 1A known scattered light device is shown with a bicolor LED 1 and a photosensor 2. The bicolor LED 1 is arranged at a scattering angle α1 of 60°. A denotes the connection contacts of the bicolor LED 1, BL denotes the "blue" light beam with a first wavelength λ1 emitted by the bicolor LED 1, and RL denotes the "red" light beam with a second wavelength λ2. The two light beams BL, RL intersect the optical detection area EB of the photosensor 2 with a scattered light volume SV or measurement volume. Z denotes the scattered light center within the scattered light volume SV, which results from the intersection of the optical emission axis SA of the bicolor LED 1 and the optical reception axis EA of the photosensor 2.

[0101] like Figure 1 As shown, the scattered light volume SV consists of two incompletely overlapping "blue" and "red" partial scattered light volumes. The small spatial difference is caused by the adjacent "diagonal" arrangement of two LED chips on a chip carrier of a bicolor LED for emitting blue and red light beams.

[0102] Figure 2 Another known scattered light device is shown with two monochromatic LEDs 101, 102, with a polarizer P connected downstream of one of the LEDs 102, and with a photosensor 2. The two LEDs 101, 102 emit light beams B1, B2, respectively. The optical emission axes SA of the light beams are inclined to one another and intersect together with the optical reception axis EA of the photosensor 2 in the scattered light center Z. In the present example, the angular offset of the two emission axes SA is approximately 25° due to their adjacent arrangement and the polarizer P connected downstream. With SA m αm represents the central optical emission axis for the two LEDs 101, 102, which forms a central scattering angle αm of approximately 90° with the receiving axis EA of the photosensor 2. In the example shown, the polarizer P is a conventional polarizer. Its polarization plane is perpendicular to the scattering plane spanned by the optical axes SA, EA, i.e. perpendicular to the local Figure 2 The image plane stretches.

[0103] Figure 3 An exemplary scattered-light device according to the invention for a scattered-light smoke detector is shown, which has a two-color LED 1 , has a photosensor 2 and has a wavelength-selective polarizer Pλ optically connected upstream of the photosensor.

[0104] The wavelength selective linear polarizer Pλ has such optical properties that the light passing through the wavelength selective linear polarizer is polarized with different intensities according to its respective wavelength λ1, λ2. In particular, this means that the light of the first "blue" wavelength λ1 passing through the polarizer Pλ, i.e. the first "blue" wavelength λ1 incident through the polarizer with non-polarized incidence, is at least partially polarized, while the light of the second "red" wavelength λ2 passing through, i.e. the second "red" wavelength λ2 incident through the polarizer with non-polarized incidence, is substantially not polarized, that is to say a maximum of 5% is polarized. As is known, a linear polarizer comprises a polarization plane, i.e. the linear polarizer constructs the polarization plane. In combination with the wavelength selectivity of the polarizer Pλ according to the invention, this means that at least 50%, in particular at least 80%, of the light of the first wavelength λ1 polarized parallel to the polarization plane of the polarizer passes through the polarizer. And at most 5%, in particular at most 1%, of the light of the first wavelength λ1 polarized perpendicular to the polarization plane of the polarizer Pλ passes through the polarizer Pλ.

[0105] The bicolor LED 1 is designed to emit light with a first wavelength λ1 in the range of 380 nm to 570 nm, in particular 470 nm ± 30 nm, and / or a second wavelength λ2 in the range of 750 nm to 1100 nm, in particular 940 nm ± 30 nm. The bicolor LED 1 can have a standard housing with a diameter of 3 mm or 5 mm, and can also be implemented in SMD technology. The photosensor 2 is in particular a photodiode, in particular a silicon photodiode, and preferably a silicon PIN photodiode. It is spectrally coordinated with at least the first and second wavelengths λ1, λ2.

[0106] The bicolor LED 1, the photoelectric sensor 2 and the wavelength-selective polarizer Pλ are typically arranged on a circuit carrier of the scattered light smoke detector according to the invention. An electronic control unit, in particular a microcontroller, is preferably also arranged on the circuit carrier. The control unit is electrically connected to the bicolor LED and the photoelectric sensor for pulsed control of the bicolor LED and for measuring the temporally distributed photoelectric sensor signals and for evaluating the respective photoelectric sensor signals according to fire characteristic variables. In the case of a detected fire, the control unit is configured to output a fire alarm optically and / or acoustically at the scattered light smoke detector and / or to a higher-level fire alarm center, for example via a wired alarm bus or via radio.

[0107] In the present example, the wavelength-selective linear polarizer Pλ according to the invention is connected optically upstream of the photosensor 2. The bicolor LED 1 and the photosensor 2 are arranged at a scattering angle α1 of 90°, which has proven to be particularly advantageous in terms of measurement technology.

[0108] In addition, according to Figure 3, the polarization plane of the wavelength selective polarizer Pλ extends perpendicularly to the plane spanned by the two optical axes SA, EA of the two-color LED 1 and the photosensor 2. The polarizer Pλ can therefore also be referred to as a vertical polarizer Pλs. In addition, the polarizer plane of the polarizer Pλs (i.e. parallel to the plane of the disk-shaped or plate-shaped polarizer) is arranged and oriented approximately perpendicularly to the receiving axis EA of the photosensor 2. It should be noted in this context that the two optical axes SA, EA do not necessarily have to intersect. It is sufficient if the two optical axes SA, EA are oriented to a common scattered light volume SV to be defined in the construction. In this case, the polarization plane of the polarizer is oriented approximately perpendicularly to the central scattering plane of the light from the two-color LED, which reaches the receiver after scattering at the aerosol.

[0109] The arrangement shown with a "vertical" polarizer Pλs has proven to be particularly advantageous in terms of measurement technology. Compared to a scattered light arrangement without polarization filter, the wavelength-selective polarization results in: the quotient ranges that otherwise overlap (see Figure 5 The scattered radiation intensity I λ1 ,I λ2 Q 02 TF3 and OF) are now spaced apart from each other, so that it is advantageously possible to reliably distinguish between an open fire and a smoldering fire while at the same time distinguishing between water vapor or water mist (see Figure 5 TF3 and OF of the quotient Q1s in the equation).

[0110] Figure 4 Along the Figure 3 The viewing direction IV drawn in shows an example of a bicolor LED 1 with two LED chips R, B arranged adjacent to each other on a chip carrier of the bicolor LED 1. The bicolor LED 1 shown has a standard housing known per se, for example with a diameter of 5 mm.

[0111] Figure 5 Shows the relationship between the three different quotients Q 01s , Q 02 , Q1s, Q2p and Q3p plotted test fires TF2, TF3, open flame OF and the distribution of interference variables H2O, such as water vapor or water mist, determined in a measurement series. The two test fires TF2, TF3 are specified in the standard EN54-7:2018.

[0112] Figure 5 The upper part of the graph shows the quotient Q of the scattered light intensity of vertically polarized infrared light having a wavelength of 940 nm and a scattering angle of 90° and the scattered light intensity of non-polarized infrared light. 01s Such diffuse light devices have been known for a long time, for example from the previous Figure 4 Known in.

[0113] Figure 5 The part below it shows the quotient Q of the scattered light intensity of the first wavelength λ1 of the non-polarized "blue" scattered light at a scattering angle of 90° at 470nm and the scattered light intensity of the second wavelength λ2 of the non-polarized infrared scattered light at 940nm. 02 Such diffuse light devices have also been known for a long time.

[0114] Figure 5 The middle part shows the Figure 3 and Figure 6 An example of a first quotient Q1s of the scattered light intensity of vertically polarized "blue" scattered light of a first wavelength λ1 at 470 nm at a scattering angle of 90° and the scattered light intensity of unpolarized infrared scattered light of a second wavelength λ2 at 940 nm.

[0115] Figure 5 The following part shows that according to Figure 3 and Figure 6 The example of the second quotient Q2p of the scattered light intensity of the parallel polarized "blue" scattered light of the first wavelength λ1 at 470nm and the scattered light intensity of the non-polarized infrared scattered light of the second wavelength λ2 at 940nm at a scattering angle of 90°, respectively. In this example, another first quotient range has a value for the second quotient Q2p in the range of 0.5±0.1, and another second quotient range has a value in the range of 1.65±0.4.

[0116] According to updated measurement technology studies, another first quotient range includes values ​​for the second quotient Q2p in the range of 0.4 to 0.8. Another second quotient range includes values ​​in the range of 1.2 to 2.3. The values ​​of the respective quotient ranges are again dependent on the scattering angle and the orientation of the polarization plane of the polarizer.

[0117] at last, Figure 5 The following part shows the Figure 7 and Figure 8 The third quotient Q3p of the scattered light intensity of the parallel polarized "blue" scattered light of the first wavelength λ1 at 470 nm and the scattered light intensity of the non-polarized infrared scattered light of the second wavelength λ2 at 940 nm at a scattering angle of 142° is shown in the example. In this example, the further first quotient range has a value for the third quotient Q3p in the range of 0.3±0.1, and the further second quotient range has a value in the range of 1.5 to 3.5.

[0118] According to updated measurement research, a further first quotient range includes values ​​for the third quotient Q3p in the range of 0.25 to 0.55 and a further second quotient range includes values ​​in the range of 1.4 to 3.7. The values ​​of the respective quotient ranges are again dependent on the scattering angle and the orientation of the polarization plane of the polarizer.

[0119] Figure 6 FIG. 4 shows an exemplary scattered light device according to the present invention having a bicolor LED 1, having a photosensor 2 and having a wavelength selective polarizer Pλ connected downstream of the bicolor LED 1. Figure 3 The scattered light devices in and differ only in the positioning of the wavelength selective polarizer Pλ. In terms of measurement technology, the two scattered light devices are equivalent to one another.

[0120] Figure 7 An exemplary backscattered light device according to the invention consisting of a bicolor LED 1 , a photosensor 2 and a wavelength selective polarizer Pλ connected downstream of the bicolor LED 1 is shown.

[0121] In this example, the wavelength selective linear polarizer Pλ according to the invention is optically connected downstream of the bicolor LED 1. The bicolor LED 1 and the photosensor 2 are arranged at a scattering angle α2 of 142°. Figure 7 , the polarization plane of the wavelength selective polarizer Pλ extends parallel to the plane spanned by the two optical axes SA, EA of the bicolor LED 1 and the photosensor 2. The polarizer Pλ can therefore also be referred to as a parallel polarizer Pλp. In addition, the polarization plane of the polarizer Pλp is arranged and oriented perpendicularly to the receiving axis EA of the photosensor 2.

[0122] The arrangement shown has proven to be particularly advantageous in terms of measurement technology. Due to the dipole effect of water molecules, the strong polarization effect of water vapor or water mist on the LED light of the first wavelength λ1 has a particularly significant effect on the scattered light signal assigned to the first wavelength λ1. As a result, water vapor and water mist can be detected as one of the main interference variables in the case of optical smoke detection, and possible false alarms can be advantageously avoided.

[0123] In this context it is again noted that the two optical axes SA, EA do not necessarily have to intersect. It is sufficient if the two optical axes SA, EA are oriented toward a common scattered light volume SV to be defined constructively.

[0124] Figure 8 FIG. 4 shows an exemplary backscattering light device according to the present invention, which consists of a bicolor LED 1, a photosensor 2 and a wavelength selective polarizer Pλ connected upstream of the photosensor 2. Figure 7 The scattered light devices in Λ / λ differ only in the positioning of the wavelength selective polarizer Pλ. In terms of measurement technology, the two scattered light devices are equivalent to each other.

[0125] Fig. 9An exemplary combined scattered light device according to the invention is shown, which consists of a common two-color LED 1, a first photosensor 21 and a second photosensor 22, each with an upstream wavelength selective polarizer Pλs, Pλp. Figure 3 The scattered light device and Figure 8 The combination of the scattering light means in the embodiment results. The bicolor LED 1 is again arranged with a first scattering angle α1 of 90° relative to the first photosensor 21 and a second scattering angle α2 of 142° relative to the second photosensor 22. The orientation of the two wavelength selective polarizers Pλs, Pλp with respect to their polarization planes also corresponds to Figure 3 or Figure 8 The respective polarizers shown in .

[0126] Fig. 9 The scattered light device for a scattered light smoke detector according to the present invention shown in FIG. Figure 3 and Figure 8 Two advantages of the scattered light device are the good distinction between an open flame and a test fire TF3 (smoldering cotton) and the very good interference variable suppression of water vapor and water mist.

[0127] Fig.10 Another combined exemplary scattered light device consisting of a common bicolor LED 1, a first photosensor 21 and a second photosensor 22 is shown. Compared to the previous embodiment, the wavelength selective polarizer Pλs, Pλp optically connected upstream of the two photosensors 21, 22 is missing. Instead, according to the invention, such a polarizer Pλp is optically connected downstream of the common bicolor LED 1. Fig.10 As shown in , the polarization plane of the wavelength selective polarizer Pλp preferably extends parallel to the plane bounded by the optical axis SA of the two-color LED 1 and the two optical axes EA1, EA1 of the photosensors 21, 22. The polarizer Pλ can therefore also be referred to as a parallel polarizer Pλp. In addition, the polarizer plane of the parallel polarizer Pλp is arranged and oriented perpendicular to the emission axis SA of the two-color LED 1.

[0128] Fig.11 An exemplary combined scattered light device according to the invention is shown, which consists of a common photosensor 2, a first bicolor LED 11 and a second bicolor LED 12, each with a downstream wavelength selective polarizer Pλs, Pλp. Figure 6 The scattered light device and Figure 7The combination of the scattered light means in the photoelectric sensor 2 again results in a first scattering angle α1 of 90° relative to the first bicolor LED 11 and a second scattering angle α2 of 142° relative to the second bicolor LED 12. The orientation of the two wavelength selective polarizers Pλs, Pλp with respect to their polarization planes also corresponds to Figure 6 or Figure 7 The respective polarizers shown in .

[0129] Fig.12 Another combined exemplary scattered light device consisting of a common photosensor 2, a first bicolor LED 11 and a second bicolor LED 12 is shown. Compared to the previous embodiment, two wavelength selective polarizers Pλs, Pλp optically connected downstream of the bicolor LEDs 11, 12 are missing. Instead, such a wavelength selective polarizer Pλp is optically connected upstream of the common photosensor 2. The polarization plane of the wavelength selective polarizer Pλp is preferably as follows: Fig.12 As shown in FIG. 1 , the polarizer Pλ extends parallel to the plane bounded by the two optical axes SA1, SA2 of the two bicolor LEDs 11, 12 and the optical axis EA of the common photosensor 2. The polarizer Pλ can therefore also be referred to as a parallel polarizer Pλp. In addition, the polarizer plane of the parallel polarizer Pλp is arranged and oriented perpendicular to the receiving axis EA of the photosensor 2.

[0130] In terms of measurement technology, on the one hand, Fig. 9 and Fig.11 The combined light scattering device shown and on the other hand according to Fig.10 and Fig.12 The combined scattered light devices shown in the drawings are equivalent to each other. Therefore, the same advantages as mentioned above are obtained.

[0131] Fig.13An example of an electronic control unit 3 for a scattered light smoke detector according to the invention is shown, which is intended to be connected to (only) one bicolor LED 1 and, for example, two photosensors 21, 22. B denotes a first LED chip of the bicolor LED 1 for emitting light of a first wavelength λ1 and R denotes a second LED chip for emitting light of a second wavelength λ2. The processor-assisted control unit 3 shown is a microcontroller which already has two integrated A / D converters 41, 42 for converting the analog photosensor signals of the respective photosensors 21, 22 into corresponding digital values. PRG denotes a software program which can be executed on the microcontroller 3 and has suitable program steps for driving the two LED chips B, R in a pulsed manner, detecting the correspondingly time-distributed digitized photosensor signals and taking them into account together in the case of a fire alarm AL. The microcontroller 3 has a corresponding signal output for the alarm. The software program PRG can also have suitable program steps for outputting a fire alarm for an open fire AL-OF, a fire alarm for a smoldering fire AL-SB instead of or in addition to outputting a fire alarm AL. Furthermore, the software program PRG can have suitable program steps for outputting a warning message W-H20 for water vapor or water mist as a disturbance variable.

[0132] at last, Fig.14 An example of a further electronic control unit 3 for a scattered-light smoke detector according to the invention is shown, which is intended to be connected to (only) one photosensor 2 and (only) one bicolor LED 1. Reference numeral 4 again denotes an A / D converter 4 for converting analog photosensor signals into corresponding digital values.

[0133] Reference numerals list

[0134] 1, 11, 12 Dual-color LED, Dual LED

[0135] 2, 21, 22 Photoelectric sensors, photodiodes, silicon PIN photodiodes

[0136] 3 Control unit, microcontroller, microcomputer

[0137] 4, 41, 42 Analog / digital converter

[0138] 101, 102 monochrome light emitting diode, monochrome LED

[0139] α1 Scattering angle

[0140] α2 Backscatter angle

[0141] αm Central scattering angle

[0142] A Connection, connection contacts

[0143] AL Alarm message, fire alarm, fire alarm

[0144] AL-SB Fire alarm message for smoldering fires

[0145] AL-OF Fire alarm message for open fire

[0146] B Blue LED, LED chip

[0147] BL, B1, B2 Blue beam, blue light

[0148] EA, EA1, EA2 Receiving axis, optical axis of photoelectric sensor

[0149] EB optical receiving area

[0150] F TF2 First commercial range for testing Fire 2

[0151] F TF3 Second commercial range for test fire 3

[0152] F OF Third-party range for open flames

[0153] F H2O The fourth commercial range for steam

[0154] H2O Water vapor

[0155] OF Open flame

[0156] P Wavelength-independent polarizer

[0157] Pλ, Pλs, Pλp wavelength selective polarizers

[0158] PRG Computer Program

[0159] R Infrared LED, LED chip

[0160] RL, R1, R2 infrared beam, red light

[0161] SA, SA1, SA2 emission axis, optical axis of bicolor LED

[0162] SAm Central Emission Axis

[0163] SV scattered light volume, scattering center, measurement volume

[0164] TF2 Test Fire 2

[0165] TF3 Test Fire 3

[0166] TR Chip Carrier

[0167] W-H20 Warning message, warning message for detected water vapor

[0168] Z optical center.

Claims

1. A scattered light smoke detector, comprising a bicolor LED (1) for emitting light of a first wavelength λ1 and a second wavelength λ2, a photoelectric sensor (2) spectrally coordinated therewith, and a control unit (3), wherein the control unit (3) is connected to the bicolor LED (1) and to the photoelectric sensor (2), and is configured to control the bicolor LED (1) to emit light of the first wavelength λ1 or the second wavelength λ2, detect a photoelectric sensor signal of the photoelectric sensor (2), and determine a first scattered radiation intensity I assigned to the first wavelength λ1 and the second wavelength λ2 based on the photoelectric sensor signal. λ1 and the second scattered radiation intensity I λ2 , and based on the first scattered radiation intensity I λ1 and the second scattered radiation intensity I λ2 Execute Fire Alarm (AL), It is characterized in that The scattered light smoke detector has a polarizer (Pλ) which is optically connected upstream of the photoelectric sensor (2) or downstream of the two-color LED (1), wherein the polarizer (Pλ) has such optical properties that the light passing through the polarizer (Pλ) is polarized to different degrees depending on its respective wavelength λ1, λ2.

2. The scattered light smoke detector according to claim 1, wherein the polarizer (Pλ) has such optical properties that light of a first wavelength λ1 passing through the polarizer (Pλ) is at least partially polarized, while light of a second wavelength λ2 passing through is not polarized.

3. The scattered light smoke detector according to claim 1, wherein the polarizer (Pλ) has such optical properties that the light of the second wavelength λ2 passing through the polarizer (Pλ) has a polarization degree of at most 0.

05.

4. The scattered light smoke detector according to claim 1, wherein the polarizer (Pλ) comprises a polarization plane and has such optical properties that at least 50% of the light of the first wavelength λ1 polarized parallel to the polarization plane of the polarizer (Pλ) passes through the polarizer (Pλ), while at most 5% of the light of the first wavelength λ1 polarized perpendicular to the polarization plane of the polarizer passes through the polarizer (Pλ). 5 . The scattered-light smoke detector according to claim 4 , wherein at least 80% of the light of the first wavelength λ1 polarized parallel to the polarization plane of the polarizer (Pλ) passes through the polarizer (Pλ). 6 . The scattered-light smoke detector according to claim 4 , wherein a fraction of at most 1% of the light of the first wavelength λ1 polarized perpendicularly to the polarization plane of the polarizer passes through the polarizer (Pλ).

7. The scattered light smoke detector according to any one of claims 1 to 3, wherein the polarizer (Pλ) is a wavelength selective linear polarizer.

8. The scattered light smoke detector according to any one of claims 1 to 3, wherein the polarizer (Pλ) is a polarizer made of a polymer film, a wire grid polarizer or a dye-type polarizer.

9. The scattered light smoke detector according to claim 8, wherein the polymer film is a polyvinyl alcohol film having permeable iodine.

10. A scattered light smoke detector according to any one of claims 1 to 3, wherein the bicolor LED (1) is arranged at a first scattering angle (α1) of 45° to 135° relative to the photoelectric sensor (2), wherein the bicolor LED (1) and the photoelectric sensor (2) are oriented to a common scattered light volume (SV), wherein the polarizer (Pλ) is a linear polarizer, wherein the polarizer (Pλ) is optically connected upstream of the photoelectric sensor (2) or downstream of the bicolor LED (1), and wherein the polarizer (Pλ) is oriented such that its polarization plane encloses an angle of 90°±5° with a plane spanned by optical axes (SA, EA) of the bicolor LED (1) and the photoelectric sensor (2).

11. The scattered light smoke detector according to claim 10, wherein the bi-color LED (1) is arranged at a first scattering angle (α1) of 60° to 120° relative to the photoelectric sensor (2).

12. The scattered light smoke detector according to claim 10, wherein the bi-color LED (1) is arranged at a first scattering angle (α1) of 90°±5° relative to the photoelectric sensor (2).

13. The scattered light smoke detector according to claim 10, wherein the control unit (3) is configured to - from the first scattered radiation intensity I λ1 and the second scattered radiation intensity I λ2 Determine the first quotient Q1s, - If the first quotient Q1s is within the first quotient range (F TF2 ) or the second quotient range (F TF3 ), the output is fire alarm (AL) or smoldering fire alarm (AL-SB), or - If the first quotient Q1s is within the third quotient range (F OF ), the fire alarm (AL) or the fire alarm for open flames (AL-OF) is output. The first commercial scope is coordinated with the test fire for smoldering fire and pyrolysis smoldering fire. The second commercial range is coordinated with the test fire for smoldering fire and smoldering cotton. The third range is coordinated with the test fire for open flames, and The fourth range is coordinated with the presence of water vapor or water mist.

14. The scattered light smoke detector according to claim 13, wherein the control unit (3) is configured to - from the first scattered radiation intensity I λ1 and the second scattered radiation intensity I λ2 The first quotient Q1s is determined in - If the first quotient Q1s is within the fourth quotient range (F H2O ), the output of a fire alarm (AL) and / or the output of a warning message (W-H2O) for the detected water vapor or water mist in the scattered light volume (SV) is prevented.

15. The scattered light smoke detector according to claim 14, wherein the H2O 、F TF2 、F TF3 、F OF )’s respective value ranges are: The fourth quotient range (F H2O ) < the first quotient range (F TF2 )< The second quotient range (F TF3 ) < the third quotient range (F OF )’s quotient value.

16. The scattered light smoke detector according to any one of claims 1 to 3, wherein the scattered light smoke detector comprises a first photoelectric sensor (21) and a second photoelectric sensor (22), wherein the bicolor LED (1) is arranged at a first scattering angle (α1) of 45° to 135° relative to the first photoelectric sensor (21), wherein the bicolor LED (1) is arranged at a second scattering angle (α2) of 142°±5° relative to the second photoelectric sensor (22), wherein the bicolor LED (1) and the first photoelectric sensor (21) and the second photoelectric sensor (22) are oriented toward a common scattered light volume (SV), wherein a polarizer (Pλ) is optically connected to the first photoelectric sensor (21). Downstream of the bicolor LED (1), the polarizer polarizes the respective light passing through and emitted by the bicolor LED (1) at different intensities according to their respective wavelengths λ1, λ2, wherein the control unit (3) is connected to the bicolor LED (1) and the first photosensor (21) and the second photosensor (22), and is configured to control the bicolor LED (1) to emit light of the first wavelength λ1 or the second wavelength λ2, detect a photosensor signal of each of the first photosensor (21) and the second photosensor (22), and determine a first scattered radiation intensity I for the first wavelength λ1 and the second wavelength λ2 based on the respective photosensor signals. λ11 ,I λ12 and the second scattered radiation intensity I λ21 ,I λ22 And based on the first scattered radiation intensity I λ11 ,I λ12 and the second scattered radiation intensity I λ21 ,I λ22 Execute Fire Alarm (AL).

17. The scattered light smoke detector according to claim 16, wherein the bi-color LED (1) is arranged at a first scattering angle (α1) of 60° to 120° relative to the first photosensor (21).

18. The scattered light smoke detector according to claim 16, wherein the bi-color LED (1) is arranged at a first scattering angle (α1) of 90°±5° relative to the first photosensor (21).

19. The scattered light smoke detector according to claim 16, wherein the bi-color LED (1) is arranged at a second scattering angle (α2) of 142°±1° relative to the second photosensor (22).

20. The scattered light smoke detector according to any one of claims 1 to 3, wherein the scattered light smoke detector comprises a first bicolor LED (11) and a second bicolor LED (12), wherein the photosensor (2) is arranged at a first scattering angle (α1) in the range of 45° to 135° relative to the first bicolor LED (11), wherein the photosensor (2) is arranged at a second scattering angle (α2) of 142°±5° relative to the second bicolor LED (12), wherein the photosensor (2) and the first bicolor LED (11) and the second bicolor LED (12) are oriented to a common scattered light volume (SV) , wherein a polarizer (Pλ) is optically connected upstream of the photosensor (2), the polarizer polarizing the light passing therethrough in different intensities according to the respective wavelengths λ1, λ2 thereof, wherein the control unit (3) is connected to the photosensor (2) and the two bicolor LEDs (11, 12), and is configured to control the two bicolor LEDs (11, 12) to respectively emit light of a first wavelength λ1 or a second wavelength λ2, detect a photosensor signal of the photosensor (2), and determine a first scattered radiation intensity I for the first wavelength λ1 and the second wavelength λ2, respectively, based on the two bicolor LEDs (11, 12) respectively controlled. λ11 ,I λ12 and the second scattered radiation intensity I λ21 ,I λ22 And based on the first scattered radiation intensity I λ11 ,I λ12 and the second scattered radiation intensity I λ21 ,I λ22 Execute Fire Alarm (AL).

21. The scattered light smoke detector according to claim 20, wherein the photoelectric sensor (2) is arranged at a first scattering angle (α1) in the range of 60° to 120° relative to the first dual-color LED (11).

22. The scattered light smoke detector according to claim 20, wherein the photoelectric sensor (2) is arranged at a first scattering angle (α1) within the range of 90°±5° relative to the first dual-color LED (11).

23. The scattered light smoke detector according to claim 20, wherein the photoelectric sensor (2) is arranged at a second scattering angle (α2) of 142°±1° relative to the second dual-color LED (12).

24. The scattered light smoke detector according to claim 5, wherein the polarizer (Pλ) is a linear polarizer and is oriented so that its polarization plane encloses an angle of 0°±5° with a plane spanned by the optical axes (SA, EA) of the bicolor LED (1) or the photosensor (2).

25. The scattered light smoke detector according to claim 16, wherein the control unit (3) is configured to - from the first scattered radiation intensity I assigned to the first scattering angle (α1) λ11 and the second scattered radiation intensity I λ12 Determine the second quotient Q2p, - from the first scattered radiation intensity I assigned to the second scattering angle (α2) λ21 and the second scattered radiation intensity I λ22 Determine the third quotient Q3p, - if the second quotient Q2p is within another second quotient range, a fire alarm (AL) and / or a smoldering fire alarm (AL-SB) is output, or - if the third quotient Q3p is within the range of the second quotient, a fire alarm (AL) is output, and If the second quotient Q2p is within a further first quotient range and / or the third quotient Q3p is within a further first quotient range, outputting a fire alarm (AL) and / or a warning message (W-H2O) for detected water vapor or water mist in the scattered light volume (SV) is prevented.

26. The scattered light smoke detector according to claim 25, wherein the control unit (3) is configured to normalize the first scattered radiation intensity I assigned to the first scattering angle (α1) as follows λ11 and the second scattered radiation intensity I λ12 , so that the first quotient Q1s and / or the second quotient Q2p of scattering particles having a predetermined average diameter in the range of 0.5 to 1.5 μm introduced into the scattered light volume (SV) have a quotient value in the range of 1 to 3, and / or wherein the control unit (3) is configured to normalize the first scattered radiation intensity I assigned to the second scattering angle (α2) as follows λ21 and the second scattered radiation intensity I λ22 , so that the third quotient Q3p has a quotient value in the range of 1 to 3 when scattering particles having a predetermined average diameter in the range of 0.5 to 1.5 μm are introduced into the scattered light volume (SV). 27 . The scattered light smoke detector according to claim 26 , wherein the first quotient Q1s and / or the second quotient Q2p has a quotient value of 2.

28. The scattered light smoke detector according to claim 26, wherein the third quotient Q3p has a quotient value of 2.

29. Use of a scattered-light smoke detector according to any one of claims 1 to 27, wherein the two-color light of a first wavelength λ1 and a second wavelength λ2 emitted during smoke detection is polarized to different degrees by means of a polarizer (Pλ).

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