Modifying the output of a laser to achieve a flat top in the laser's gaussian beam intensity profile

A method for generating a flat top intensity profile for light illuminating moving particles in a particle analyzer, comprising the steps of:

• (a) directing light from a source toward a scanner;
• (b) scanning the light from the source that is incident on the scanner, to produce scanned light, the scanner being driven to scan a beam of the light at a desired frequency and with a desired amplitude;
• and
• (c) focusing the scanned light onto a portion of the particle analyzer through which a particle is disposed, such that a particle in the portion of the particle analyzer is illuminated, wherein the desired frequency is selected so that the particle is illuminated with at least one cycle of the scanned light, and the desired amplitude for the scanning is selected to be less than a cross-sectional dimension of the beam, both the desired amplitude and the cross-sectional dimension of the beam being measured at a point where the beam is incident on the particle, and so that the beam remains incident on the particle as the particle is scanned by the beam within the portion of the particle analyzer, the desired frequency, the desired amplitude for the scanning, and an intensity profile of the source of the light cooperating to generate a flat top intensity profile for the scanned light that is focused on the particle.

Apparatus for producing light having an effective flat top intensity profile for illuminating a sample disposed within a particle analyzer, comprising:

• (a) a source of light;
• (b) a deflecting component that is mounted to receive incident light from the source and to deflect the incident light in a periodic manner, to produce a beam of scanned light that is directed toward a sample volume of the particle analyzer, the deflecting component being driven to scan the beam at a frequency selected so as to illuminate a sample in the sample volume of the particle analyzer with at least one cycle of the scanned light and with an amplitude selected to be less than a cross-sectional dimension of the beam of the scanned light as measured at a point where the beam is incident on the sample and so that the sample is fully illuminated with the scanned light while the sample is in the sample volume of the particle analyzer;
• and
• (c) one or more lenses that focus the scanned light onto a sample in the sample volume of the particle analyzer, a peak of an intensity profile of the light produced by the source being of a lower magnitude than a peak of the effective flat topped intensity profile of the scanned light that illuminates the sample volume, due to an increased intensity of the scanned light caused by focusing the scanned light with the one or more lenses and the flat topped intensity profile of the scanned and focused light being caused by scanning the light with the deflecting component at the frequency and amplitude.