Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia.
Opt Lett. 2010 Aug 15;35(16):2780-2. doi: 10.1364/OL.35.002780.
We show that the transient response of acoustically modulated optical flux in a turbid medium irradiated by a pulsed point source of light is delayed in time relative to the light-alone flux obtained in the absence of acoustic modulation. The time delay is shown to result from an initial phase of flux reversal, as determined by the time point of the input pulse onset with reference to the ultrasound cycle. Both the time delay and amplitude of modulation are shown to be dependent on the effective attenuation coefficient of the medium. Application of a periodic train of excitation pulses spaced at equal intervals at, or in multiples of, the ultrasound period enables a time-locked detection of the modulated light, without the deleterious effects caused by speckle artifacts.
我们表明，在脉冲点光源辐照下的混浊介质中，声调制光通量的瞬态响应相对于在没有声调制的情况下获得的单独光通量存在时间延迟。延迟的结果是通量反转的初始相位，由输入脉冲与超声周期的起始时间点决定。延迟时间和调制幅度都被证明取决于介质的有效衰减系数。周期性激励脉冲序列的应用，在超声周期的整数倍或等于超声周期的时间间隔处激发，可实现调制光的时间锁定检测，而不会产生散斑伪影造成的有害影响。
