Range-selective digital holography for three-dimensional imaging of a complex object

Frequency-modulated continuous-wave (FMCW) range-selective digital holography (RSDH) achieved by frequency shifting the reference local oscillator beam has previously been used to selectively image two objects within the depth of field of the imaging system at short ranges. In this paper, we present a three-dimensional (3D) imaging demonstration using FMCW RSDH. This technique was used to image and reconstruct a 3D object, improving on past methods by reducing the need for fast frame rate sensor arrays and reducing the total sensor integration time. This allows the data for a 3D reconstruction to be recorded an order of magnitude faster than the traditional time-domain Fourier transform FMCW digital holography method and only requires holographic stability for less than 1 ms at a time. A 3D object consisting of square-shaped columns of multiple heights was imaged at a range of 8.4 m. A 16.0 GHz chirp bandwidth resulted in an imaging range resolution of 1 cm, much less than the optical system's depth of field of 33 cm. The relative heights of the columns and total depth of 11 cm were calculated with a 0.01 cm root-mean-square error.