Abstract: A device (10) is provided for measuring at least one characteristic (12) related to presence of particles. The device (10) includes a light source unit (16) for emitting light into a region (18) containing particles (20), with the light source being configured to emit light from a plurality of locations in a manner so that the emitted light follows a desired intensity distribution (22), the desired intensity distribution (22) being desired for the measurement of the at least one characteristic (12). In preferred embodiments the intensity distribution is Lambertian.

Abstract: A device (10) is provided for measuring at least one characteristic (12) related to presence of particles. The device (10) includes a light source unit (16) for emitting light into a region (18) containing particles (20), with the light source being configured to emit light from a plurality of locations in a manner so that the emitted light follows a desired intensity distribution (22), the desired intensity distribution (22) being desired for the measurement of the at least one characteristic (12). In preferred embodiments the intensity distribution is Lambertian.

Abstract: A semi-circular LED array that is comprised of independent high intensity LED components and which in combination, will emit a focused single wavelength of highly accurate and precise frequency, in accordance with the Lambertian principle. The resultant combined light source can then be used in combination with an integrating nephelometer, for purposes of precise ambient air quality monitoring. The entire LED array and housing chamber can be easily interchanged to facilitate separate and different wavelength light sources, as required. The user can, when desired, easily remove the entire LED array, and replace with another LED array of different total wavelength capability.