用于眼轴长度测量的弱光信号检测系统设计

Design of weak optical signal detection system for measuring eye axial length

在眼内入射光安全的前提下,由于眼轴长度测量时角膜表面与视网膜色素上皮层2个反射面的反射率相差较大,反射的光信号强度属于微弱信号范畴。为了能够去除噪声,快速提取该信号的峰值用于眼轴长度起止点计算,采用PIN光电二极管接收微弱光信号并配合I-V转换电路、自动增益控制电路及后级处理电路搭建了一套弱光信号检测系统。实验采用ZIESS模拟眼进行测试,结果表明设计的检测系统最小能探测到0.77 nW左右的微弱光信号,最大光电转换能力可达4.5×10^8 V/W,信噪比达到9 dB以上,测得眼轴长度结果与实际值最大存在0.05%的误差。系统具有低噪声、高增益、大动态范围等优点,为实现眼轴长度精准测量提供了一种有效方案。

Since the reflectivity of two reflective surfaces of the corneal surface and the retinal pigment cortex is greatly different when measuring the axial length of eye,the intensity of the reflected optical signal belonges to the weak signal category under the premise of the incident light safety in the eye.In order to remove the noise and quickly extract the peak value of the signal for the calculation of the starting and ending point of the eye axial length,a weak optical signal detection system was designed.This system used PIN photodiode to receive weak optical signal and a weak light signal detection system was built coordinated with the I-V conversion circuit,automatic gain control circuit as well as the post-processing circuit.The experiment used ZIESS simulation eye to test.The results show that the designed detection system can detect the weak optical signal of about 0.77 nW at least,the maximum photoelectric conversion capacity can reach 4.5×10^8 V/W,the signal-to-noise ratio is more than 9 dB,and the maximum error between the measured eye length and the actual value can reach 0.05%.This system is characterized by low noise,high gain and large dynamic range,which provides an effective solution for accurate measurement of the eye axial length.