Detection system for droplet-based assays

A system for detection in droplet-based assays, comprising:

• a channel;
• an illumination assembly including a light source and a slit and configured to produce a beam of light that illuminates an examination region of the channel as droplets pass through such region;
• a detector configured to detect light received from the examination region;
• and
• a controller that collects data representing light detected by the detector,
• wherein light from the light source is shaped by the slit such that the beam of light is elongated in cross section where the beam intersects the channel;
• and
• wherein the beam of light at the examination region is narrower than the diameter of each droplet such that no more than a portion of the droplet is illuminated by the beam of light at any given time.