(a) Optically trapped particle (circled particle). As the sample stage is moved (b) vertically and then (c) horizontally, the optically trapped particle appears to remain at the same spot within the image captured by the camera, whereas the background particles sedimented on the coverslip appear defocused when the sample is moved vertically in (b) and displaced when it is moved horizontally in (c).
Fig. 8.13 — Optically trapped particle