Figure 1.

Processes of locating cellular size objects at high spatial and temporal resolution. (A) Overview of the localizing method. The recorded videos were first analyzed to identify target cells. The position of the cell in each frame was determined by cross-correlation between the cell image in each frame and the reference image. (B) Schematic representation of the four types of swimming paths. (Red solid lines) The possible swimming paths of Chlamydomonas cells: (a) swimming within and parallel to the in-focus zone, (b) swimming perpendicular or oblique to the XY plane, (c) swimming outside of the in-focus zone, and (d) wiggling within the trajectory or stationary. Cells that swim parallel to the glass slide and that have an in-focus image were selected for further analysis. (C) The definition of the score S_i,j. The image of cell i in frame j was transformed into frequency space, and the values at the horizontal axis were sampled to produce a power spectrum. The amplitude of the frequency component at 32/3 pixel ≈ 6 μm gives S_i,j.