When phase-shifting digital holography with a continuous fringe-scanning scheme is implemented using a PC-based measurement system without any synchronous circuit, nonuniform phase-shifted interference fringes are captured because of the fluctuation in the image-capturing interval. To cope with the nonuniform phase shifts, a statistical generalized phase-shifting approach is employed. Because the algorithm is designed to use an arbitrary phase shift, the nonuniform phase shifts do not obstruct object-wave retrieval. Moreover, multiple interference fringes can be obtained in a short time owing to the continuous fringe-scanning scheme. However, the wavefront calculation method is not designed for sequentially recorded interference fringes. To use multiple interference fringes appropriately, we develop a least-squares wavefront calculation method combined with corrections for the initial phase and the direction of phase rotation. We verify the proposed method by numerical simulations and optical experiments. The results show that the object wave with the same initial phase can be correctly reconstructed by using both phase correction methods simultaneously.
We propose integrated phase-shifting digital holography using statistical approach. In the integrated phase-shifting
scheme, the phase shifts are generated by a reference mirror moving with a uniform velocity, and sequential phaseshifted
holograms are captured. Therefore, there is no wait time for stabilization, which offers some advantages such as
short measurement time, high phase stability and high noise tolerance. The proposed method does not require precise
control and calibration of the phase shifter and synchronization between the phase shifter and the digital image sensor.
Therefore, the practical digital holography system with high accuracy can be implemented at low cost.
We propose a phase unwrapping method for processing two phase distributions simultaneously based on a deterministic
phase unwrapping method using a composite complex function in which the real and imaginary parts are assigned by two
separate phase distributions. Hardly any crosstalk between the real and imaginary parts was observed in the actual
numerical computation. We developed a Fourier transform-based 3D measurement method that primarily consists of a
fast Fourier transform (FFT) algorithm. Since the proposed method is employed in the frequency domain, the 3D
retrieval process can be performed effectively even if the deformed grating pattern uses a high-resolution image format.
To accelerate the FFT computation, we implemented the proposed method using a graphics processing unit. The
experimental results showed that 3D measurement could be performed in real time using a deformed grating pattern of
We propose robust three-dimensional (3D) object recognition method using a complex amplitude based on the Fourier transform profilometry (FTP) and the numerical holographic multiplexing. In the proposed method, a reference data for correlation operation is produced by multiplexing of the complex amplitude derived from several rotated objects, taking into account that the complex amplitude derived from rotated objects is mutually uncorrelated with respect to the rotation angle. Due to the use of the multiplex reference data, the correlation between each reference data to be multiplexed and a target object is performed with single operation. Therefore, the proposed method has tolerance to rotation in addition to translation due to the shift-invariant property of the FTP-based correlator. The spatial position and the orientation of the 3D object can be also evaluated by the proposed method. Experimental results show that the proposed method successfully recognizes the rotated 3D object.