Fig. 2.
Response of 1.7-µm bead induced by 20-Hz harmonic modulation of Frad. (a) M-mode OCT image. Scale bar: 200 µm (vertical) and 1 s (horizontal). (b) Raw φOCT at pixel depths corresponding to the surface of the petri dish bottom and the 1.7-µm bead (top), and the resulting ΔOPL response at the bead depth after the phase registration (bottom), as a function of t. (c) Frequency-domain representation of the amplitude of ΔOPL. Green dashed line indicates the 20-Hz modulation frequency. Black dashed line indicates the noise amplitude, δA, at 20 Hz. Inset shows zoom-in view of the time-domain ΔOPL response in (b). (d) Amplitude (blue) and phase shift (red) w.r.t. the PF drive waveform, h̃(t), of filtered ΔOPL as a function of t. Black dashed lines and gray dotted lines indicate the median values and standard deviations over the time, respectively. Inset graphically illustrates amplitude (blue arrow) and phase shift (red arrow), where a delay in the bead response corresponds to a negative-valued phase shift.