JPH03144897A - Optical smoke detector and operation thereof - Google Patents

Abstract

PURPOSE: To prevent the generation of an erroneous alarm due to the contamination of a chamber by directly measuring light scattered on the inner wall surface of the chamber. CONSTITUTION: The luminous flux 21 of a transmitter 10 crosses with the visual field 22 of a receiver 11 and the receiver 11 ideally receives only scattered light due to smoke intruding inside the chamber 35. In the meantime, the visual field 23 of the receiver 12 is arrayed so as to face an area 36 to be irradiated by the transmitter 10, the intensity of reflected light is detected and the output signals indicate the overall noise light quantity and background light quantity inside the chamber 35. Then, when the output signals for indicating the background light quantity reach a predetermined value, a threshold value for originating alarm signals is raised and the sensitivity of the threshold value when the smoke intrudes inside the chamber 35 is maintained almost fixed. Thus, the generation of a false alarm due to the contamination of the chamber 35 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of an optical smoke detector and its method of operation.

BACKGROUND OF THE INVENTION Optical smoke detectors include at least one light source, such as an infrared light emitting diode, and at least one light detector, such as a photoelement. The emitted light from the light source and the field of view of the photodetector are focused. The elements are arranged so that the emitted light from the light source does not directly enter the photodetector. This type of smoke detector is based on the principle that aerosols entering the detector chamber reflect some radiation. As a result, the emitted light is scattered and
The light is received by a photodetector. When the amount of scattered radiation reaches a predetermined intensity, a photodetector is activated and issues a warning signal.

The detector chamber must, of course, have at least one opening to allow smoke to enter the chamber. However, if the chamber is provided with an opening, light may also enter through this opening.

Therefore, consideration has been given to blocking light from entering the chamber as much as possible. Light entering from the surrounding environment is reflected and scattered many times by the walls of the chamber. A light source located within the chamber also produces scattered radiation.

In other words, the ambient light and the light source produce a combined scattered light,
The amount of composite scattered light changes depending on the degree of dirt on the chamber wall of the detector. Contamination cannot be avoided since smoke openings are provided. As the degree of contamination increases, the amount of scattered light also increases. As a result, the amount of scattered light reaches a level exceeding the threshold of the photodetector. That is,
This will result in a false alarm being issued, and this is a situation that must be avoided in a fire prevention system.

The amount of light received by the photodetector when smoke is in the chamber is at most 1% of the amount of light emitted from the light source. This clearly shows how the background light, or noise light, increased by contamination, has a significant impact on the detection system. As background light increases, smoke detectors become more sensitive. In other words, a small amount of smoke that is not yet dangerous will trigger an alarm. Therefore, a false alarm may be issued even if the amount of noise light has not yet sufficiently reached the threshold of the photodetector.

[Problems to be Solved by the Invention] An operating method is known in which a light source is lit in pulses and a photodetector functions only while the pulses are being transmitted. By using this operating method, it is possible to considerably suppress the influence of ambient light. However, this method cannot suppress the influence of the noise light described above. The prior art has shown numerous methods for canceling the effects of noise light.

The smoke detector according to DE 2754139 uses a pair of photodetectors. The first photodetector is placed in a normal position relative to the light source, while the second photodetector is placed near the light source and parallel to the first photodetector.

Both photodetectors also require surface elements on the chamber walls.

To correct for the effects of noise light, the output signals of both photodetectors are subtracted. However, this type of smoke detector does not take into account that the photodetector receives background light from all areas of the chamber. The diameter of the region that emits useful scattered light when the smoke enters the chamber is significantly larger than the diameter of the light beam of the light source, so that the second photodetector also receives useful scattered light. . In other words, this method cannot compensate for the effects of noise light when smoke enters. Furthermore, the amount of light reflected from the chamber walls is so small that it is practically impossible to detect the amount of background light caused by contamination of the chamber.

German Patent Publication No. 2754139 also shows how a single photodetector can be pivoted by suitable means to a position that either crosses the beam of the light source or bypasses the beam of the light source. . Smoke detectors should not use mechanical drive means to pivot the optics. Furthermore, the ability of this method to accurately detect contamination is insufficient.

The smoke detector according to European Patent Publication No. 0079010 uses a second photodetector that directly receives light from a light source. This second photodetector measures the radiation intensity of the light source and controls the sensitivity to smoke when the light source itself becomes contaminated. However, this method cannot compensate for background light due to contamination of the smoke detector chamber.

Further, a smoke detector is also shown in West German Patent Publication No. 3334545, but this publication does not disclose a method of compensating for noise light.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical An object of the present invention is to provide a method for operating a smoke detector.

According to the present invention, chamber contamination, such as dust particles adhering to the chamber walls of a smoke detector, is directly measured.

According to a first embodiment of the invention, the smoke detector chamber is provided with a second photodetector directed towards the inner wall of the chamber which is illuminated by a light source. Also, in the second embodiment, a pair of light sources is provided, one of which illuminates the inner wall surface of the chamber within the field of view of the photodetector.

By doing so, the light scattered on the inner wall surface of the chamber can be directly measured. It will be appreciated that the intensity of the background light is initially very low when the walls are in darkness, and increases over time as dust enters the chamber.

The smoke detector of the present invention produces a relatively high level signal indicative of a contamination condition. The stronger this signal becomes, the more the amount of noise light increases.

When this signal level reaches a predetermined value, a service signal may be generated indicating that the smoke detector requires cleaning. Furthermore, using this service signal,
The sensitivity of the photodetector provided to receive the useful scattered light may be varied.

In the smoke detector according to the invention, the photodetector is connected to a threshold stage. When the output signal of the photodetector indicative of the amount of background light reaches a predetermined value, a control signal is applied to the stage's control and roll inputs to raise the threshold level. That is, when the contamination within the chamber reaches a predetermined state, the threshold for issuing an alarm signal is raised. Therefore, the threshold sensitivity when smoke enters the chamber can be maintained approximately constant. Otherwise, the sensitivity of the threshold increases as the degree of contamination increases, and even smaller and smaller amounts of smoke will trigger an alarm.

A particularly great advantage of the invention is evident from the fact that compensation for background light can be made even when smoke has penetrated into the chamber. As long as the amount of smoke in the chamber is below the alarm threshold, the smoke will result in a relatively small amount of reflected light from the illuminated area entering the background light photodetector during the check cycle. However, the background light is mostly replaced by reflections from smoke particles that are in the light beam. Therefore, the intensity of the background light incident on the photodetector when the amount of smoke is relatively small remains approximately constant when the contamination state is constant.

According to the present invention, not only a separate photodetector but also a separate light source may be used to measure the amount of light reflected from the inner wall surface of the chamber of the smoke detector. Of course, this method is more expensive than using only one additional light source or photodetector. Moreover, with this method care must be taken that the radiation for the additional photodetector does not enter the useful scattered light photodetector. Also, care must be taken to avoid entering useful scattered light photodetectors. Also, care must be taken to ensure that useful scattered light photodetectors do not receive any noise light emitted from the additionally illuminated inner walls of the chamber. In the case of pulse control to selectively operate both measuring elements, the two last-mentioned requirements are spread over t.

[Examples] The present invention will be described in more detail below based on examples shown in the drawings.

FIG. 1 is a front view of the optical system of a smoke detector according to the invention.

FIG. 2 is a cross-sectional elevational view of the smoke detector taken along line 2-2 of FIG.

FIG. 3 is a front view of the optical system of a smoke detector according to a second embodiment of the invention.

FIG. 4 is an elevational view of the smoke detector taken along line 4--4 of FIG.

FIG. 5 is a block diagram of the smoke detector circuitry.

Figure 6 shows the second implementation! This is a block diagram of the circuit mechanism of a smoke detector according to three different designs.

FIG. 7 is a graph showing the relationship between signals and pulses that occur when operating a smoke detector according to the invention.

The illustrated optical system includes an optical transmitter 10;
A first optical receiver 11 and a second optical receiver 12 are included. The transformer main cover 10 includes a light emitting diode 13 (LED) and a condensing lens 14. Receiver 11 includes an optical element 15 and a condenser lens 16. The second receiver 12 is connected to an optical element 17 and a condenser lens 18. Transmissor 10 and receiver 11
, 12 are concealed within a channel such as bore 19,20 which houses the transmissor 10 and receiver 11. The main transformer tube 10 emits a parallel light beam 21 through a lens 14. The optical element 15 is provided with a lens 16.
It has a field of view 22.

Receiver 12 has a field of view 23. The optical system is housed in a cylindrical casing 30.

The top cover of the casing 30 is not shown in FIG.

Additionally, the optical system includes electrical circuitry and fixtures for securing the smoke detector to the ceiling of a room, for example. A circular gap or slot 31 is provided near the bottom of the casing 30, and a side slope portion 32 extends inward from the slot 31.
and 33 are extended. The angled portions 32 , 33 prevent excessive ambient light from entering the smoke detector chamber 35 within the casing 30 . All parts within the chamber, especially its walls, are black in color to maximize light absorption.

As shown in FIG. 2, the axis of the transmitter 10 and the receiver 11 is
1 intersects the field of view 22 of the receiver 11 and is arranged so as not to directly enter the lens 16. Therefore,
The receiver 11 ideally receives only the scattered light caused by the smoke that has entered the chamber 35. The amount of light received is luminous flux 2
1 and the field of view 22 intersect with each other. Optical systems of this type have already been disclosed in the prior art.

The light beam 21 of the transducer 10 is incident on the inwardly extending portion 32 of the wall at substantially an angle of 90 degrees. The radiating area of portion 32 is labeled with the reference number "36".

The field of view 22 of the receiver 12 is oriented such that it views the area 36 illuminated by the transmissor 10, ie, at a 90 degree angle to the portion 32. Therefore,
Receiver 12 receives a portion of the reflected light from the radiation area.

Since the entire inner surface of the chamber 35 is black,
While the smoke detector is new, the amount of reflected light is almost zero. However, the situation changes when dust particles accumulate on the inner surface of the chamber 35. The more dust particles accumulate in region 36, the more light from Transmink-10 will be reflected. The receiver 12 detects the intensity of the reflected light and generates an output signal according to the intensity. Thus, the output signal from the receiver 12 represents the contamination state of the chamber due to infiltration of dust particles, ie, the overall amount of noise light and backlight within the chamber 35. It is not possible to prevent ambient light from entering the chamber through the slot. In addition, the main transformer
The ten radiation beams 21 generate noise light within the chamber 35. Both of these amounts of background light are low at receiver 1 even in the absence of scattered light due to smoke infiltration.
It can rise to the level where it can activate 1. Even if the amount of background light does not reach the threshold value, the amount of scattered light will still be erroneously recognized.

3rd r! ! The optical system according to the embodiment of FIG. The transmissor includes light emitting diodes 65 and 66 and condensing lenses 67 and 6, respectively.
Contains 8. Receiver 50 includes an optical element 70 and a condenser lens 71. The transformer mains 51, 52 and receiver 50 are concealed in channels or bores within the casing 30 as indicated by reference numerals 72 and 73 for the transmitter 51 and receiver 50. The transmitter 51 transmits a parallel light beam 7 through a lens 67.
6, and the optical elements 70 are arranged by a lens 71 so as to have a field of view 77. The emitted light from the transmitter 52 is collimated by a lens 68 and becomes a parallel beam 78. As is particularly apparent from FIG. 4, the axes of the optical transmitter 51 and the receiver 50 are such that the emitted light beam 76 intersects the field of view 77 of the receiver 50 and therefore the emitted light beam 76
are arranged so that they do not enter the lens 71. Therefore, the receiver 50 ideally receives only the light scattered by the smoke that has entered the chamber 35 in the area where the radiation beam 76 and the field of view 77 intersect with each other. Optical systems of this type for smoke detection are also known.

Emitted light from the transmissor 52 is incident on the angled portion 32 of the wall at an angle of approximately 90 degrees.

The radiating area of portion 32 is designated by reference numeral 80 in the drawings. The field of view of the receiver 50 is that of the transmitter 5.
The radiation area 80 from 2 is also about 9 for the portion 32.
Oriented as desired at a 0 degree angle. Therefore,
A portion of the light reflected from the irradiation area 80 is transmitted to the receiver 50.
incident on . Since the entire chamber 35 is black, the amount of reflected light is almost zero while the smoke detector is new. However, the situation changes when dust particles accumulate within the chamber 35. The more dust accumulates in region 80, the more radiation from transmitter 52 will be reflected. The receiver 50 detects the intensity of the reflected light,
Generates an output signal according to the intensity. In other words, this output signal represents the contamination state of the chamber due to the infiltration of dust particles, that is, the amount of scattered light within the chamber 35. The fact that the transformer mains 51, 52 are activated alternately and therefore the noise light caused by contamination of the chamber is detected only during activation of the light source 52 is pointed out and explained below.

FIG. 5 shows a circuit arrangement for operating the optical system of the smoke detector according to FIGS. 1 and 2. FIG.

Receivers 11 and 12 are increased by electronic switch 40.
controller and control circuit 41. The circuit 41 is connected to a service detector 43 by an AND gate 42. Furthermore, the circuit 41 is also connected to a transmitter 10 which emits, for example, infrared light. The other circuit 41 is also connected to a decade counter 44 which is connected to the output of the control circuit 41. counter 44
The output of is connected to the input of AND gate 45, and AN
The other input of D-gate 45 is connected to the output of circuit 41. The output of AND gate 45 is connected to switch 40. The output of the counter 44 is connected to the input of a NAND gate 46, and the output of the NAND gate 46 is connected to the input of another AND gate 47. A
The other input of ND gate 47 is connected to the output of circuit 41. The output of the AND gate 47 is sent to the alarm circuit 48
It is connected to the. This circuit arrangement works as follows.

The transformer 10 is controlled by an amplifier and control circuit 41 to generate optical pulses. Simultaneously with the activation of the optical transmission pulse, the receiver 11 is activated, i.e. the receiver 11
becomes ready to receive light.

When the optical indicators are normal, there is no scattered light in the optical transmission path 21 of Transminc-10, and therefore, when the transmission pulse ends, the receiver 11 is inactivated. However, if the receiver generates a significant output signal during the optical transmission pulse, the amplifier and control circuit 41 generates a pulse that causes the decade counter 44 to stop.

No matter how many more transmission pulses are emitted from the circuit 41, the count value of the counter can no longer be changed.

If a smoke signal is detected during a subsequent n11M transmission pulse, the second output of circuit 41 is activated and AND gate 4
7 into an AND state. In this way, the alarm circuit 48 is activated. The other AND state of AND gate 47 is provided by the output of NAND gate 46 when counter 44 does not provide a corresponding output signal. The number of transmission pulses is counted by a counter 44, and after a predetermined number, for example, m transmission pulses have been generated, the counter 44
emits an output signal. This output signal indicates that the other side of the AND gate 45 is A due to the generation of the transmission cycle.
When the signal is in the ND state, it is supplied to the switch 40 via the AND gate. Switch 40 then connects second receiver 12 to amplifier and control circuit 41 and initiates a check cycle. If the amount of light reflected from the chamber walls (see Figures 1 and 2) is less than a predetermined level, the switch returns to its original smoke detection cycle position.

It should also be disclosed that the smoke detection function is inhibited during the check cycle.

For this purpose, a NAND gate 46 is provided, and NAND gate 46 is provided.
The output signal of AND gate 46 changes when the counter issues an output signal. Therefore, in this case, even if an alarm is issued, an alarm signal cannot be supplied to the alarm circuit 48 via the AND gate 47. However, if the amount of light reflected from the detector chamber and received by the receiver 12 exceeds a predetermined level, the receiver 12 will issue an output signal and the circuit 41 will again automatically send the stop signal 2 to the counter 44. supply to. The smoke detection lock is therefore maintained and the amplifier and control circuit 41 is further connected to the receiver 12. Amplifier and control circuit 41
No matter how many transmission pulses are emitted from then on, the count value on the counter will no longer change. If, during the presence of a light emission pulse, the receiver receives a sufficient amount of scattered light without interruption during the next n1VA transmission pulse, the second output of circuit 41 is asserted and AND gate 42 becomes an AND condition.

The output signal of AND gate 42 controls service circuit 43. For example, service circuit 43 indicates to the operator the degree of contamination within the detector chamber.

Furthermore, optical and/or audible indications may be provided. It is also conceivable to supply the corresponding output signal of the service circuit 43 to the amplifier and control circuit 41 to reduce the trigger sensitivity for smoke detection depending on the degree of contamination. As long as the level of contamination is within the range where smoke can be detected without malfunction.
The circuit described above continues to operate in known cycles.

However, if the contamination condition reaches a critical value, further smoke detection functions may be suppressed to avoid generating false alarms. Further, the service kit 43 may be configured to detect and give instructions on different degrees of contamination classified into ranks.

In the embodiment of FIG. 6, a transmitter 5 for smoke detection
1 and a single receiver 50 cooperating with the transformer mains 52 for determining the contamination status. receiver
50 and transmitter 51 cooperate in a manner similar to that of the corresponding optical system disclosed in FIG. Transmitter 52 emits light to illuminate an area of the detector chamber within the field of view of receiver 50. The transformer transformers 51 and 52 receive clock pulses from an amplifier and control circuit 53, which is connected to the input of the transformer main transformer 52 via an AND gate 54. On the other hand, an AND gate 55 is connected between the circuit 53 and the transmitter 51.

A clock pulse is also provided to a decade counter 56, the output of which is connected to a second input of an AND gate 54. Further, a NAND gate 57 is connected to the output of the counter 56, and a NAND gate 57 is connected to the output of the counter 56.
The output of gate 57 is connected to the second input of AND gate 55 and to the input of AND gate 5. Further, the output of the circuit 53 is connected to an AND gate 59, and the output of the circuit 53 is connected to an AND gate 59.
A second input of D-gate 58 is connected to the output of counter 56. Service kit 60 is AND gate 59
connected to the output of Alarm circuit 61 is connected to the output of AND gate 58.

During the smoke detection cycle, optical transmitter 51 is pulsed and ANDed by the output of NAND gate 67.
Gate 55 is in a second AND state. On the other hand, during the smoke detection cycle, the transformer 52 is inactive since the counter 56 does not emit a corresponding output signal, or when the output signal of the receiver 50 exceeds a predetermined level.
Obtaining an electronic lock state, via AND gate 58,
After counting a predetermined number of measurement pulses by controlling the AND gate 58 from the amplifier and control circuit 53,
To activate alarm circuit 61, counter 56 is immediately stopped by amplifier and control circuit 53, as explained above in connection with FIG. The output of NAND gate 57 provides a second AND condition. When a predetermined number of transmitted pulses are counted by the counter,
The counter issues a predetermined output signal, which causes AND gates 55 and 58 to
Locked via 7. At this time Transmink-52
emits light pulses while receiver 50 is operating in a synchronous manner. When the output signal of the receiver 50 exceeds a predetermined level, an electronic lock condition is provided to control the service circuit 60 via an AND gate 59, and the predetermined level is set for n measurement pulses. level is maintained. The second state for AND gate 59 is provided by the output signal of counter 56.

The signals received by the service circuit 60 may be utilized in a manner similar to that disclosed in connection with FIG. The previously described check cycle is maintained for a predetermined number of transmission pulses, after which the counter 5S is reset. Therefore, as described above, smoke detection cycles and check cycles are operated alternately.

In FIG. 7, a time axis is expanded to represent the analog parameters that generally represent the conditions occurring in the detector chamber 35 according to FIGS. 1 and 2. In FIG. That is, on the time axis 100 in FIG. 7, analog parameters such as the smoke 101 shown with an increasing tendency, the amount of scattered light 104 due to pollution, the increasing amount of scattered light 104', and the corrected threshold signal 102' are shown. It is shown. Time axis 105 shows a number of light pulses 106 transmitted from transformer 10 of FIG. Furthermore, FIG. 7 shows a check light pulse 1 that is somewhat wider than the smoke detection light pulse 106.
07 is also shown. In the graph of FIG. 7, the light pulse 107 for chipping is generated after the four light pulses 106 are generated.
It is radiated from the transmitter 10 in FIG. Further, on the time axis 110, an output pulse 111 of the receiver 11 and an output pulse 108 of the receiver 12 are illustrated. These output pulses are responses to light pulses 106 or 107, respectively. When the detector chamber is not yet contaminated, the output signal of the receiver 12 corresponding to the amount of light pulse reflected from the inner surface of the detector chamber is relatively small; however, when the detector chamber is already contaminated, this output signal is It will be appreciated that the output signal can be greater than -11. As the amount of smoke in the detector chamber increases, the output pulses 111 of receiver 11 also increase. When the output pulse 111 reaches the threshold 102, the transmitter 10 is controlled by circuitry 41 to emit a series of light pulses at a high frequency.

This optical pulse train is indicated by rlQ$aJ in the drawing.

Correspondingly, the pulse train 111 is output from the receiver 11.
a occurs. Generating a train of measurement pulses at a high frequency for a predetermined period of time will ensure that smoke has indeed penetrated into the detector chamber.

As the contamination progresses (curve 104), the receiver 12 receives a very strong output pulse, as also shown in the graph. A service signal may be issued at stage 43 of FIG. 5 if the contamination condition exceeds a threshold value, designated rl12J in the analog system and rl13J in the individual output pulse representation. Also, instead of issuing a service signal, the threshold value 102 may be readjusted by the amplifier and control circuit. This readjustment is shown by a dashed line at step 114 on the time axis 100. This readjustment requires a higher output signal for receiver 11 to issue an alarm signal in circuit 41.

Although the threshold value may be adjusted by the circuit 41 as described above, it is also possible to reduce the radiation intensity of the transmitter 10.

By reducing the radiation intensity, the operating sensitivity is also reduced. However, in this case the threshold of pulse 108 representing a contamination condition must be lowered as indicated by rl13J.

[Brief explanation of the drawing]

FIG. 1 is a front view of the optical system of a smoke detector according to the present invention. FIG. 2 is a cross-sectional view of the smoke detector taken along line 2-2 of FIG. FIG. 3 is a front view of the optical system of a smoke detector according to a second embodiment of the invention. FIG. 4 is an elevational view of the smoke detector taken along line 4--4 of FIG. FIG. 5 is a block diagram of the circuitry of the smoke detector. 6th
The figure is a block diagram of the circuitry of a smoke detector according to a second embodiment. FIG. 7 is a graph showing the relationship between signals and pulses generated when operating a smoke detector according to the present invention. 10...Transmitters 11...Receiver 12...Receiver 13...Light emitting diode 14...Condensing lens 15... ...Optical element 16... Condensing lens 17... Optical element 1 day... Condensing lens Patent applicant Hartwieg Beyer 1st edition Figure 2 3rd edition 4th pre-contamination state smoke amount analog parameter 111α r8- Scattered light amount pollution amount

Claims (1)

[Claims] 1. A method of operating an optical smoke detector, wherein at least one light detection receiver for smoke detection is provided in a detector chamber, the light detection receiver comprising: measuring the amount of useful scattered light emitted by a volume unit in the chamber in the region where the collimated field of view of the receiver intersects the collimated beam of the light source in the chamber; or detect the amount of reflected light emitted from the irradiated inner surface unit in the chamber, in which the second photodetector receiver detects the amount of reflected light from the inner surface unit of the chamber. A method of operating an optical smoke detector characterized by measuring. 2. A field of view of a detector chamber, a light source, and a pair of light detection receivers cooperating with the detector chamber intersects the emission path of the light source, and a field of view of a second light detection receiver; is directed onto an inner surface of the detector chamber, and the smoke detector further includes an alarm circuit that issues an alarm signal when the output signal of the first light detection receiver reaches a predetermined value. , comprising a control circuit that issues a control signal when the output signal of the second photodetection receiver reaches a predetermined value in response to a contamination condition of the detector chamber, Optical smoke detector according to claim 1, characterized in that said inner surface area of the detector chamber arranged within the field of view of the receiver (12) is illuminated with a light source (10). 3. comprising a detector chamber, a light source, and at least one light detection receiver cooperating with the detector chamber, the field of view of the light detection receiver intersects the emitted light beam of the light source; The detector includes an alarm circuit for issuing an alarm signal when the output signal of the photodetection receiver reaches a predetermined value, and for detecting fluctuations in the output signal of the photodetection receiver due to contamination of the detector chamber. a first photodetection receiver (
50) or a second light source (52) is provided for illuminating an inner surface area of the detector chamber which is located within the field of view of a further photodetecting receiver; The control circuit is provided to alternately operate one of the pair of light sources (51, 52), and the control circuit controls the light detection receiver (12) during the operation cycle of the second light source (52). 2. An optical smoke detector according to claim 1, wherein the optical smoke detector is adapted to issue a control signal when the output signal reaches a predetermined level. 4. A photodetection receiver (12) that receives scattered light is connected to a threshold stage for adjusting a threshold, and the second photodetection receiver (12) that receives background noise light is connected to a threshold stage for adjusting a threshold.
Optical smoke detection according to claim 2, wherein a control signal is transmitted to the control input of the threshold stage to raise the threshold level when the output signal of 2) reaches a predetermined level. vessel. 5. First and second photodetection receivers (11, 12)
Optical smoke detector according to claim 2, characterized in that it is connected to a control and alarm circuit (43, 48) by a switch (40), preferably of electronic type. 6. The second photodetection receiver (12) is connected to the switch (4).
0) to the service circuit (43, 60) or when the second light source (52) is activated, the alarm circuit is inoperative, respectively. optical smoke detector. 7. The optical smoke detector according to claim 5, wherein a control circuit is provided so that the alarm circuit is not activated when the second light source (52) is activated. 8. The control circuit (41) includes a clock oscillator, and a counter (44) connected to the clock is provided, and when the count value reaches a predetermined first count number, the counter Claim 2 or 3, wherein the second photodetection receiver is activated, and when the count value reaches a predetermined second count number, the first photodetection receiver is activated. The optical smoke detector according to item 3. 9. The control circuit (53) includes a clock, and an adjustable counter (56) connected to the clock is provided, and the counter starts counting when the count value reaches a predetermined first count number. activating a second light source (52);
Claim 2, wherein the first light source is activated when the count value reaches a predetermined second count number.
The optical smoke detector according to item 3 or item 3. 10. Optical smoke detector according to claim 6 or 7, wherein the switch (40) is controlled by the output signal of the counter (44). 11. A control signal is supplied to a service kit (43, 60) that emits a service signal, the service signal is supplied to a threshold stage, and the output signal of the threshold stage generates an alarm when the service signal reaches a predetermined value. Claims 2 to 10 that disable the operation of the circuit
Optical smoke detector as described in section. 12. The inner surface area of the detector chamber (35) located within the field of view of the first or second light detection receiver is about 9
Claim 2 which forms an angle of 0 degrees
Optical smoke detector according to items 1 to 11.