Patent ID: 7715006

Claim:
An optical system for a particle analyzer, comprising: a light source for irradiating a particle passing through a flow cell with light; a photodetector for receiving light from the particle; a detecting lens, which is disposed between the flow cell and the photodetector, for directing the light from the particle toward the photodetector; a light shielding member, which is disposed between the detecting lens and the photodetector, wherein the light shielding member is configured for blocking direct light from the light source entering into the photodetector; and an irradiation optical system, which is disposed between the light source and the flow cell, for forming a first focus on the flow cell through which the particles pass, and forming a second focus on the light shielding members; wherein the irradiation optical system: forms the first focus that converges in a parallel direction relative to a direction of passage of the particle and extends in a perpendicular direction relative to the direction of passage of the particle; forms a third focus that converges in the perpendicular direction relative to the direction of passage of the particle and extends in the parallel direction relative to the direction of passage of the particle at a position between the flow cell and the light source; and forms the second focus by imaging the third focus with the detection lens.