We present simultaneous three-dimensional (3D) trajectories of a mother colony and a daughter colony of a Volvox
moving in water by a parallel phase-shifting digital holographic microscope. The mother colony was detected as a circle
in the reconstructed phase image of the Volvox. While a daughter colony was detected as a circle in the reconstructed
amplitude image of the Volvox. The lateral position of each colony was determined as the center of each circle. The depth
position of each colony was determined as the position that provided the sharpest reconstructed amplitude image of the
edge of each colony during the refocusing of the reconstructed image of the Volvox. We successfully trajected each
colony dynamically moving in an area of 0.8 mm × 0.8 mm × 1 mm.
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.
KEYWORDS: Digital holography, 3D image reconstruction, Microscopes, Holograms, Holography, Phase shifts, 3D metrology, 3D image processing, Microorganisms, Polarization
We report the three-dimensional (3D) trajectory of a Volvox moving in water was recorded by parallel phase-shifting digital holographic microscope providing 10X magnification. The recording frame rate, the shutter speed, and the total recording time were 1000 fps, 0.25 ms, and 2.1 s, respectively. In the reconstructed phase image of the Volvox, the shape of the Volvox is regarded as a circle. The lateral coordinates of the Volvox were determined as the center of the circle. The depth coordinates of the Volvox were determined as the propagation distance where the edge of the Volvox in the reconstructed amplitude image was clearest while the propagation distance was varied. We successfully demonstrated the 3D tracking of curvedly moving Volvox.
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