基于CCD探测器的全视场层析成像方法研究

Full-field optical coherence tomography based on CCD detector

由正弦信号驱动PZT调制参考镜以实现参考光相位调制,CCD光探测器的曝光时间为正弦驱动信号的四分之一周期,利用频率-同步探测技术,在一个参考光调制周期共提取四帧全视场参考光与样品反射和散射光干涉图像。为了获得最优的参考光信号调制参数,一种基于PID控制器的闭环控制技术与数字移相相结合的方法用于调制系统,采用50Hz的理想正弦曲线的数字离散量来控制PZT的调制幅度,数字移相电路调整PZT的振动相位来保证最优调制参数的获得。CCD(频率f=200Hz)由软件驱动,采用积分算法,实现了由CCD探测器提取微弱全视场层析信号的方法。

The reference wave phase was modulated with a sinusoidal vibrating mirror attached to a Piezoelectric Transducer （PZT）, the integration was performed by a CCD, and the charge storage period of the CCD image sensor was one-quarter period of the sinusoidal phase modulation. With the frequency-synchronous detection technique, four images （four frames of interference pattern） were recorded during one period of the phase modulation, In order to obtain the optimum modulation parameter, the values of amplitude and phase of the sinusoidal phase modulation were determined by considering the measurement error caused by the additive noise contained in the detected values. The PZT oscillation was controlled by a closed loop control system based on PID controller. An ideal discrete digital sine function at 50Hz with adjustable amplitude was used to adjust the vibrating of PZT, and a digital phase shift techniques was used to adjust vibrating phase of PZT so that the phase of the modulation could reach their optimum values. The CCD detector was triggered with software at 200Hz. Based on work above, a small coherent signal masked by the preponderant incoherent background with a CCD detector was obtained.