Particle detection system implemented with a mirrored optical system

In a particle detection system for detecting sample particles entrained in a fluid stream, the particle detection system having a view volume that has an effective center and in which a light beam propagating along a light propagation path along an optical axis transversely intersects the fluid stream such that entrained particles upon which the light beam is incident scatter first and second correlated light components, the first light components scattered in first directions for propagation through a light collection lens system having a collection system axis and for incidence on a detector that produces signals representing the intensities of the first light components, and the second light components scattered in second directions that are different from the first directions, comprising:

• a light reflector positioned relative to the effective center of the view volume to receive the second light components, the light reflector having light directing properties that cause reflections of the second light components in the form of corresponding inverted second light components that propagate through the view volume and the light collection lens system;
• an array of first and second detector elements corresponding to spatial locations in the view volume of the entrained particles causing scattering of the first and second light components, the first detector elements being members of a first set of detector elements in the array and receiving the first light components and the second detector elements being members of a second set of detector elements in the array and receiving the corresponding inverted second light components, each of multiple different pairs of the first and second detector elements in the respective first and second sets representing an opposing pair of detector elements that are positioned at equal distances from the collection system axis to view a common spatial location of the view volume by receiving concurrently the first and second light components propagating through the common spatial location and each of the different pairs producing detector pulse output signals representing the intensities of the first light component and its corresponding inverted second light component the pair received;
• and
• a signal processing system that responds to the detector pulse output signals by combining them to increase a detection system signal-to-noise ratio and thereby enhancing the detectability of the first and second light components to record presences of their corresponding particles entrained in the fluid stream.