KEYWORDS: Microscopes, Digital holography, Phase shifts, 3D metrology, 3D image reconstruction, Holograms, Image processing, Cameras, 3D acquisition, Optical components
Significance: Parallel phase-shifting digital holographic microscope (PPSDHM) is powerful for three-dimensional (3D) measurements of dynamic specimens. However, the PPSDHM reported previously was directly fixed on the optical bench and imposed difficulties case, thus it is required to modify the specification of the microscope or transport the microscope to another location.
Aim: We present a modularized PPSDHM. We construct the proposed PPSDHM and demonstrate the 3D measurement capability of the PPSDHM.
Approach: The PPSDHM was designed as an inverted microscope to record transparent objects and modularized by integrating the optical elements of the PPSDHM on an optical breadboard. To demonstrate the effectiveness of the PPSDHM, we recorded a 3D motion-picture of moving Volvoxes at 1000 frames / s and carried out 3D tracking of the Volvoxes.
Results: The PPSDHM was practically realized and 3D images of objects were successfully reconstructed from holograms recorded with a single-shot exposure. The 3D trajectories of Volvoxes were obtained from the reconstructed images.
Conclusions: We established a modularized PPSDHM that is capable of 3D image acquisition by integrating the optical elements of the PPSDHM on an optical breadboard. The recording capability of 3D motion-pictures of dynamic specimens was experimentally demonstrated by the PPSDHM.
The authors review three-dimensional (3D) trajectory of minute object by parallel phase-shifting digital holography. Parallel phase-shifting digital holography is a technique capable of single-shot recording of a complex amplitude distribution of object wave from a dynamic object. The authors constructed an inverted microscope based on parallel phase-shifting digital holography. The microscope consisted of a continuous-wave laser, a Mach–Zehnder interferometer, a polarization imaging camera, and a magnification optical system. A high-speed polarization imaging camera was employed to record motion picture of holograms of the dynamic specimen. Motion picture of the holograms of a minute alum crystal sinking down in the solution of alum was recorded by the microscope at the rate of 60 frames per seconds (FPS). Refocused images of the crystal were successfully obtained for all of the sinking time. The 3D trajectory of the crystal was derived from the refocused images. Also, the authors constructed an inverted and vertical microscope based on parallel phase-shifting digital holography. A Volvox swimming in a water as a living microbe was recorded by the microscope at the rate of 1000 FPS. The 3D trajectory of the microbe curvedly moving in the area of 500 μm × 500 μm × 500 μm was successfully demonstrated from the reconstructed images of the microbe.
A parallel phase-shifting digital holographic microscope achieves motion-picture phase imaging of a dynamic minute specimen. However, much time and skill are required to construct the optical system of the microscope. The authors designed and constructed an optical system of a parallel phase-shifting digital holographic microscope in which the optical components of the microscope were integrated on a breadboard standing perpendicular to an optical table. The lateral and longitudinal magnifications of the microscope are 10 and 100, respectively. The authors experimentally demonstrated the motion-picture phase imaging of a dynamic minute specimen by the microscope. The holograms were recorded at 1,000 fps and the shutter speed was 0.5 ms.
We propose parallel phase-shifting radial shearing interferometry and apply this technique to single-shot wavefront measurement. This technique records a single interference image consisting of the combination of radially sheared two object waves. By applying parallel phase-shifting interferometry and a wavefront reconstruction algorithm to the recorded single interference image, the phase image of the measuring object wave is obtained. We numerically simulated single-shot wavefront measurement by using the proposed technique. It was assumed that the object was two particles. The amplitude and phase images of the particles were assumed as Gaussian distribution. The cross-correlation coefficient between the original phase image and the phase image reconstructed by using the proposed technique was 0.984.
We propose single-shot incoherent digital holography using parallel-phase shifting radial shearing interferometry. The object wave from an incoherently illuminated or self-luminous object is Fourier transformed, and enters a parallel phase-shifting radial shearing interferometer. Then, the radially sheared two object waves combines and the hologram whose phases are relatively shifted in every 2x2 pixels of the image sensor are generated. By applying parallel phaseshifting interferometry to the hologram, we obtain the amplitude and the phase of the complex spatial coherence function of the object wave. Then, the complex amplitude distribution of the object wave at arbitrary depth is calculated from the function. We applied the proposed technique to the three-dimensional imaging of two LEDs and experimentally demonstrated the proposed technique.
KEYWORDS: Digital holography, Phase shifts, 3D image reconstruction, Crystals, Stereoscopy, 3D image processing, Holograms, Digital imaging, Refractive index, Image sensors
Parallel phase-shifting digital holography is a powerful technique for recording motion picture of holograms with an image sensor and numerically reconstructing the motion picture of the high-quality three-dimensional (3-D) images of the object in a computer. This technique provides high-quality images of light intensity and phase of the object at a time instant at arbitrary depth position. Therefore, the technique achieves 3-D motion-picture imaging of a dynamic object. The technique provides not only large depth of field and high temporal resolution at the same time but also a motion picture of an invisible object. It is difficult for other 3-D imaging techniques to achieve these features of parallel phase-shifting digital holography. The authors review two experiments demonstrating the 3-D imaging by the technique and the features of the technique. One experiment demonstrated the motion-picture 3-D imaging of a minute crystal, sinking down in solution, by refocusing the amplitude images of the crystal. The result was obtained for the first time, to the best of our knowledge. The other demonstrated the motion-picture 3-D imaging of refractive indices of dynamic invisible gas flow by applying the Abel inversion to the phase images of the flow obtained by the technique.
Parallel phase-shifting digital holography is a technique capable of recording three-dimensional (3D) motion picture of dynamic object, quantitatively. This technique can record single hologram of an object with an image sensor having a phase-shift array device and reconstructs the instantaneous 3D image of the object with a computer. In this technique, a single hologram in which the multiple holograms required for phase-shifting digital holography are multiplexed by using space-division multiplexing technique pixel by pixel. We demonstrate 3D motion picture of dynamic and transparent gas flow recorded and reconstructed by the technique. A compressed air duster was used to generate the gas flow. A motion picture of the hologram of the gas flow was recorded at 180,000 frames/s by parallel phase-shifting digital holography. The phase motion picture of the gas flow was reconstructed from the motion picture of the hologram. The Abel inversion was applied to the phase motion picture and then the 3D motion picture of the gas flow was obtained.
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