Digital Holographic Microscopy For3D Surface Texture Measurement

Along with the development of machinery industry, semiconductor industry andbiotechnology, ultra-precision processing, nano-technology, micro-electromechanical systemsand living-cells engineering are putting forward higher requests to the three-dimensionalmeasurement of micro-nano surface tomography. Precise instruments of three-dimensionalsurface tomography must have the characteristics of real-time dynamic observation, highvertical and lateral resolutions and wide measurement range.Digital holography is an imaging and measuring technology based on the principle ofdiffraction and interference principle of light, which can get the waves’ amplitude and phaseinformation at the same time. The three-dimensional topography of the object can be deducedfrom that. Digital holographic microcopy has the property of non-contact, real-time, big depthof field, high resolution and phase-contrast imaging, which can been widely used inmicro-nano surface measurement, micro-electromechanical analysis systems, particledetection, cell biology, etc.This paper is aimed at digital holographic microscopy of micro-nano surface texture. Itsmain work is as follows:Physical optical principle of the record and reconstruction process of digital holographyis analyzed, and the mathematic model of digital holography is established.According to the mathematical analysis of in-line and off-axis digital holography, thesoftware simulation of the record and reconstruction process is accomplished.By sampling theorem and spectrum separation requirements, the set conditions of theoptical path parameters in off-axis digital holography are separately given.Test experiments are demonstrated to verify the design parameters of off-axis digitalholographic optical path, and the design of optical path is improved.An off-axis digital holographic microscopic measurement system is established based onthe illumination of low-coherent plane wave.By using the Fresnel algorithm and angular spectrum algorithm， ideal results of digitalholographic reconstruction are acquired, and the reconstructed horizontal and verticalparameters are both in good accordance with their standard values.