Patent ID: 8031340

Claim:
An optical system for a flow cytometer that includes a flow channel with an interrogation zone, and an illumination source that impinges the flow channel in the interrogation zone from a particular direction, the optical system comprising: a lens system including at least two lens surfaces located on opposite sides of the interrogation zone of the flow channel, wherein the two lens surfaces are aimed directly at, and are configured to collect and collimate light directly from, the interrogation zone; and a detection system configured to detect light from the lens system, including: first local filter that allows passage of a first wavelength of light and at least partially reflects a second wavelength of light; and a second local filter that at least partially reflects of the first wavelength of light and allows passage of the second wavelength of light; wherein the first and second filters are aligned such that light reflected from the first filter passes through the second filter, and light reflected from the second filter passes through the first filter.