Measurements of particle fields by in-line holography

In-line holography is introduced in this paper. It is one of the many methods that have been used for the precision metrology for objects in various fields of engineering. Holography is a modern powerful tool to measure and analyze particle fields. A 4-f optical system is applied in in-line holographic recording system. The information of a particle field not only is recorded on a holographic plate but also can be derived from the reconstructed images through a reconstruction system. In the parallel optical field, the analysis of a particle field can be done with different instruments and in different depth of field and different positions. This recording system makes every particle in different spatial positions in the particle field have a same amplification ratio. This will be benefit to the data processing and calibration of the particle field. The interferential patterns formed on recording plate and relationship of the particles and the noise of the background in the particle field are analyzed. Some experimental results of particle fields recorded by in-line holography are presented in this paper. The particle identification and the elimination of noise are discussed at the end of this paper.