Three Dimensional Surface Shape Measurement of Big Objects by Pre-imaging Digital Holography
预成像数字全息测量大物体三维形貌

A pre-imaging method was proposed to enlarge the field-of-view of 3-D surface shape measurement by digital holography.A minified real image of the object was obtained by an imaging lens,then the real image was recorded by fresnel off axis digital holography.Tilting of the illumination wave produces phase difference between two reconstructed images from the holograms,the 3-D surface shape information was extracted from the phase difference after phase filtering and phase unwrapping.Experimental results prove that the measurement field-of-view is enlarged by one order of magnitude at least.The use of fresnel off axis digital holography makes the system less vulnerable to the instability of the environment.