Application of digital holography in micro­fluidic measurements

Fengmin Xiao1,Minhao Zhou1,Jiangtao Chen1, Rui Luo2,Shi Liu1*

1Department of Thermal Power Engineering, North China Electric Power University, Chang ping District, Beijing 102206, China

2Department of Thermal Engineering, Tsinghua University, Beijing 100084, People’s Republic of China

*e­mail: liushi_ncepu@yahoo.com.cn

ABSTRACT

Digital holography is a powerful tool in 3D diagnostics of flow fileds. In order to increase the resolution of the depthwise position measurement, an in­line holographic microscopy experiment of a fixed single particle with different defocus distances was carried out. The recorded holograms of the particle were reconstructed at various reconstruction distances by using the fast Fourier transform. The best numerically focused reconstruction was determined by a gray level gradient method. The defocus distances of the particle were estimated from the best reconstruction distances and were compared with those measured by the microscope focusing system.

Keywords holography; reconstruction; gray level gradient; Fourier transform;