Fire Detection Using The Scattered Light Principle With A Staggered Activation Of A Further LED Unit For Radiating In Further Light Pulses With Different Wavelengths And Scattered Light Angles

A scattered light smoke detector comprising:

• a detection unit functioning according to the scattered light principle;
• a first and second LED unit for radiating light pulses into a scattered light volume;
• and
• a photosensor spectrally sensitive to the first and second LED unit;
• wherein the first LED unit is arranged with the photosensor at a forward scatter angle;
• the second LED unit is arranged with the photosensor at a backward scatter angle;
• the first and second LED unit each output light pulses of both a first and second wavelength λ1, λ2;
• the second wavelength λ2 is greater than the first wavelength λ1;
• a processor-supported control unit connected to the first and second LED unit and to the photosensor;
• output means a fire alarm;
• and
• an electronic memory store storing a computer program comprises instructions executable by the processor-supported control unit, wherein the instructions when executed by the processor-supported control unit configure the processor to:
• radiate light pulses of a first wavelength λ1 into a scattered light volume and measuring a first scattered radiation intensity generated by forward scattering in the scattered light volume;
• radiate light pulses of a second wavelength λ2 into the scattered light volume and measuring a second scattered radiation intensity generated by forward scattering in the scattered light volume, wherein the second wavelength λ2 is greater than the first wavelength λ1;
• determine a first quotient from the first and second scattered radiation intensity and comparing the first quotient with a first and second comparison value, wherein the first comparison value is greater than the second comparison value;
• and
• if the first quotient lies between the first and the second comparison value:
• measure a third scattered radiation intensity generated by backward scattering of the second wavelength in the scattered light volume;
• determine a second quotient from the first and third scattered radiation intensity and comparing the second quotient with a third comparison value;
• and
• generate a fire alarm if the second quotient exceeds the third comparison value.

A scattered light smoke detector comprising:

• a detection unit functioning according to the scattered light principle;
• an LED unit for radiating light pulses into scattered light volume;
• a first photosensor and a second photosensor both spectrally sensitive to the LED unit;
• wherein the first photosensor is arranged in relation to the LED unit at a forward scatter angle;
• the second photosensor is arranged in relation to the LED unit at a backward scatter angle;
• the LED unit outputs light pulses of a first and second wavelength λ1, λ2, wherein the second wavelength λ2 is greater than the first wavelength λ1;
• a processor-supported control unit connected to the LED unit and to the first and second photosensor;
• output means for a fire alarm;
• and
• an electronic memory store storing a computer program, wherein the computer program comprises instructions executable by the processor-supported control unit, wherein the instructions when executed by the processor-supported control unit configure the processor to:
• radiate light pulses of a first wavelength λ1 into a scattered light volume and measuring a first scattered radiation intensity generated by forward scattering in the scattered light volume;
• radiate light pulses of a second wavelength λ2 into the scattered light volume and measuring a second scattered radiation intensity generated by forward scattering in the scattered light volume, wherein the second wavelength λ2 is greater than the first wavelength λ1;
• determine a first quotient from the first and second scattered radiation intensity and comparing the first quotient with a first and second comparison value, wherein the first comparison value is greater than the second comparison value;
• and
• if the first quotient lies between the first and the second comparison value:
• measure a third scattered radiation intensity generated by backward scattering of the second wavelength in the scattered light volume;
• determine a second quotient from the first and third scattered radiation intensity and comparing the second quotient with a third comparison value;
• and
• generate a fire alarm if the second quotient exceeds the third comparison value.