Phase-Shifting Method with Unknown Intervals in Phase-Shifting Digital Holography

2006 ◽  
Vol 3-4 ◽  
pp. 211-216
Author(s):  
T. Kita ◽  
Yoshiharu Morimoto ◽  
Motoharu Fujigaki ◽  
Toru Matui
Keyword(s):  
Phase Shift ◽  
Intensity Distribution ◽  
Digital Holography ◽  
Phase Distribution ◽  
Reference Beam ◽  
Spherical Wave ◽  
High Accuracy ◽  
Displacement Measurement ◽  
Phase Shifting ◽  
Phase Shifting Method

Displacement measurement can be performed with high accuracy using phase-shifting method. In phase-shifting method, it is often used four steps of phase-shifting for one cycle. In conventional method, to measure the displacement of an object by an interferometer, the phase of a reference beam should be shifted by every π/2 in the four-step phase-shifting. In this paper, a phase-shifting method with unknown intervals is proposed. This method does not need to shift a phase by every π/2. It can detect an intensity distribution and a phase distribution from five fringe images with equal intervals even if the phase-shift amount is unknown. Using this method, we propose a displacement measurement of phase-shifting digital holographic interferometry using spherical wave as reference wave.

Determination of Phase Shift by Digital Holography

2019 ◽  
Vol 888 ◽  
pp. 43-46
Author(s):  
Yoshitaka Takahashi ◽  
Masatoshi Saito ◽  
Toru Nakajima ◽  
Masakazu Shingu
Keyword(s):  
Phase Shift ◽  
Noise Reduction ◽  
Digital Holography ◽  
High Accuracy ◽  
Measured Data ◽  
Phase Shifting ◽  
Surface Shape ◽  
Shape Measurement ◽  
Phase Shifting Interferometry

In phase shifting interferometry phase shift is applied by various ways, but applying it with high accuracy, especially by LD current modulation, is not easy. In order to determine the accurate phase shift a new method has been proposed that the value of LD current corresponding to π/2 phase shift can be determined by phase shifting digital holography. The measured data of standard in surface shape measurement were used for calibration, and the obtained value was confirmed to cause noise reduction and improvement of holographic reconstructed images in digital holography.

Phase-shifting digital holography with an unknown reference beam

2021 ◽  
Author(s):  
Roghayeh Yazdani ◽  
Hamidreza Fallah
Keyword(s):  
Digital Holography ◽  
Phase Retrieval ◽  
Reference Beam ◽  
Phase Shifting ◽  
Retrieval Algorithm ◽  
Reference Field ◽  
Digital Holograms ◽  
Noisy Conditions ◽  
Phase Retrieval Algorithm

In digital holography, errors of the reference field degrade the quality of the reconstructed object field. In this paper, we propose an effective method in phase-shifting digital holography in which the reference field does not need to be known and perfect. The unknown complex amplitudes of both reference and object fields are derived simultaneously. The method employs only five digital holograms and a single execution of a phase retrieval algorithm. So, the required measurements and algorithm executions in this method are fewer than those in other methods; it suggests a simpler and faster method. The effectiveness of the suggested method is indicated by simulation, under noise-free and noisy conditions. Moreover, the capability of the method to extract full information about the phase singularities in both fields is demonstrated.

Effect of Phase Error in Phase-Shifting Interferometer

2019 ◽  
Vol 888 ◽  
pp. 11-16 ◽  
Author(s):  
Yoshitaka Takahashi
Keyword(s):  
Phase Shift ◽  
Measurement Errors ◽  
Phase Error ◽  
Optical Path Length ◽  
High Accuracy ◽  
Optical Path ◽  
Phase Shifting ◽  
Optical Source ◽  
Phase Shifting Interferometry ◽  
Phase Shift Error

Phase-shifting interferometry is widely used because it can measure phase with high accuracy. Changing optical path length with a PZT transducer and changing frequency of the optical source with a laser diode (LD) are two common methods to apply the desired phase shift between the arms in the interferometer. In any case, however, it is not easy to apply the desired shift accurately, and if not, measurement errors occur. In order to reduce the errors, the effect of the phase shift error has been analyzed numerically especially in the case with LD.

A method of hard X-ray phase-shifting digital holography

2016 ◽  
Vol 23 (4) ◽  
pp. 1024-1029
Author(s):  
So Yeong Park ◽  
Chung Ki Hong ◽  
Jun Lim
Keyword(s):  
Phase Shift ◽  
Digital Holography ◽  
Relative Phase ◽  
Test Pattern ◽  
Fresnel Lens ◽  
Phase Shifting ◽  
New Method ◽  
Phase Plate ◽  
X Ray ◽  
Line Type

A new method of phase-shifting digital holography is demonstrated in the hard X-ray region. An in-line-type phase-shifting holography setup was installed in a 6.80 keV hard X-ray synchrotron beamline. By placing a phase plate consisting of a hole and a band at the focusing point of a Fresnel lens, the relative phase of the reference and objective beams could be successfully shifted for use with a three-step phase-shift algorithm. The system was verified by measuring the shape of a gold test pattern and a silica sphere.

Development of Phase Shifting Device Using the Deflection of a Cantilever for Digital Holography

2006 ◽  
Vol 326-328 ◽  
pp. 19-22
Author(s):  
Hitomi Matsukawa ◽  
Motoharu Fujigaki ◽  
Toru Matui ◽  
Yoshiharu Morimoto
Keyword(s):  
Strain Gauge ◽  
Research Group ◽  
Digital Holography ◽  
Displacement Measurement ◽  
Phase Shifting ◽  
Measurement Equipment

Phase-shifting digital holography can be used for displacement measurement instead of strain gauge. Our research group is developing the measurement equipment for phase-shifting digital holography. Generally, in the measurement equipment, piezo stages are used as phaseshifting devices. But the piezo stage is expensive. Cheaper and smaller phase-shifting device is required in order to put the measurement equipment into practical use. In this paper, we, therefore, propose a phase-shifting device using the deflection of a cantilever and we verify whether this phase-shifting device can be usedfor digital holography.

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