Principles of Operation

Fast imaging is required to obtain enough events for statistical significance. Traditional flash on the fly photography sacrifices sensitivity in order to image rapidly moving objects. Amnis employs a custom camera which is operated using a technique called time-delay-integration (TDI), a specialized detector readout mode that preserves sensitivity and image quality even with fast relative movement between the detector and the objects being imaged.

As with any CCD, image photons are converted to photocharges in an array of pixels. During TDI operation the photocharges are continuously shifted from pixel to pixel down the detector, parallel to the axis of flow. By synchronizing the photocharge shift rate with the velocity of the flowing cell, the effect is similar to physically panning a camera. With TDI, image streaking is avoided despite signal integration times that are orders of magnitude longer than those of conventional flow cytometry. Each pixel is digitized with 12 bits of intensity resolution, providing a minimum dynamic range of three decades per pixel.