Multiple motion picture recording in light-in-flight recording by holography with an angular multiplexing technique.

Light-in-flight recording by holography (LIF holography) is an ultrafast imaging technique for recording light pulse propagation as a motion picture. In this study, we propose and demonstrate multiple motion picture recordings of light pulse propagation by use of LIF holography with angular multiplexing. We set incident angles of reference light pulses to remove the difficulty in adjusting the optical path length difference between an object light pulse and reference light pulses and the complexity of the optical system.

Ultrafast double motion-picture recording technique for propagating light pulses with an ultrashort time difference.

Ultrafast imaging techniques involving light propagation, which can record light-pulse propagation as a motion picture, are commonly applied in various fields. However, conventional ultrafast imaging techniques cannot obtain multiple motion- pictures with an ultrashort time difference. In this Letter, we propose an imaging technique to obtain double motion-pictures of propagating light pulses with an ultrashort time difference.

Simultaneous imaging of sound propagations and spatial distribution of acoustic frequencies.

We propose a simultaneous imaging technique of both sound propagations and spatial distribution of acoustic frequencies. We experimentally demonstrated the proposed technique for the acoustic waves of frequencies 39,500 and 40,500 Hz, which have close sound pressure. The sounds were recorded at the framerate of 100,000 fps by parallel phase-shifting digital holography.

Motion picture of magnified light pulse propagation with extending recordable time of digital light-in-flight holography.

We experimentally demonstrate a motion picture imaging technique that can record a magnified image of light pulse propagation with extending the recordable time of digital light-in-flight recording by holography. We constructed an optical system that achieves a recordable time extension and an observation of a magnified image of light pulse propagation. As a result, we experimentally succeeded in recording light pulse propagation with a 7.

Spatiotemporal observation of light propagation in a three-dimensional scattering medium.

Spatiotemporal information about light pulse propagation obtained with femtosecond temporal resolution plays an important role in understanding transient phenomena and light-matter interactions. Although ultrafast optical imaging techniques have been developed, it is still difficult to capture light pulse propagation spatiotemporally. Furthermore, imaging through a three-dimensional (3-D) scattering medium is a longstanding challenge due to the optical scattering caused by the interaction between light pulse and a 3-D scattering medium.

Influence of the lateral size of a hologram on the reconstructed image in digital light-in-flight recording by holography.

Digital light-in-flight recording by holography is a promising technique for observing a propagating ultrashort light pulse as a motion picture. A typical reconstruction process of digital light-in-flight recording by holography, we extract holograms without considering the relationship between the lateral size of the extracted hologram (sub-hologram) and the size of an area where the propagating ultrashort light pulse and an image sensor overlap. The area records the image of the ultrashort light pulse at a certain moment.

High-speed imaging of the sound field by parallel phase-shifting digital holography.

Sound field imaging techniques have been found very useful for acoustic designs. Building on this idea, innovative techniques are needed and presented in this paper, where we report on developed imaging of the sound field radiated from speakers by parallel phase-shifting digital holography. We adopted an ultrasonic wave radiated from a speaker for an object.

Modularized microscope based on parallel phase-shifting digital holography for imaging of living biospecimens.

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.

Motion-picture recording of ultrafast behavior of polarized light incident at Brewster's angle.

Observing light propagation plays an important role in clarifying ultrafast phenomena occurring on femtosecond to picosecond time scales. In particular, observing the ultrafast behavior of polarized light is useful for various fields. We have developed a technique based on Polarization Light-in-Flight Holography, which can record light propagation as a motion picture that can provide information about the polarization direction.

Extending recordable time of light-in-flight recording by holography with double reference light pulses.

Light-in-flight (LIF) recording by holography is a powerful technique for observing ultrashort light pulse propagation. However, the recordable time of the technique has been limited by the lateral length of the holographic plate. Then, to extend the recordable time of LIF recording by holography, we proposed a space-division multiplexing technique of holograms, which divides the holographic plate longitudinally and uses double reference light pulses.

Wavelength division multiplexer based on cavity-resonator-integrated guided-mode resonance filters for a compact multi-wavelength light source.

Cavity-resonator-integrated guided-mode resonance filters (CRIGF) consisting of a grating coupler in a waveguide resonator formed by two distributed Bragg reflectors of different reflectances can act as a wavelength-selective reflector and an input waveguide coupler for an incident free-space wave. Integration of CRIGFs in a waveguide is proposed to give an array of external mirrors and a wavelength division multiplexer for constructing a compact multi-wavelength light source. Four CRIGFs of 10-μm-size aperture with a wavelength spacing of 15 nm were designed and fabricated.

Three-dimensional imaging of distribution of refractive index by parallel phase-shifting digital holography using Abel inversion.

Although digital holography is a powerful technique obtaining a phase image of a transparent object, the image reconstructed by the technique merely expresses phase distribution of the light wave after transmitting through the object. Phase variation of inside of the object is difficult to be obtained. Then, we applied Abel inversion method to the high-speed phase image of a dynamic transparent object assumed axially symmetric.

Determination of cavity length of cavity-resonator-integrated guided-mode resonance filter.

A cavity-resonator-integrated guided-mode resonance filter is a kind of narrowband filters, which uses a resonance effect of a waveguide cavity. Two experimental methods for determining the cavity length were investigated in order to estimate the response time of the filter. SiO(2)-based filters for operation at 1540-nm wavelength were fabricated and their cavity lengths were determined from measured resonance wavelengths.

Parallel phase-shifting digital holography using spectral estimation technique.

We propose a parallel phase-shifting digital holography using a spectral estimation technique, which enables the instantaneous acquisition of spectral information and three-dimensional (3D) information of a moving object. In this technique, an interference fringe image that contains six holograms with two phase shifts for three laser lines, such as red, green, and blue, is recorded by a space-division multiplexing method with single-shot exposure. The 3D monochrome images of these three laser lines are numerically reconstructed by a computer and used to estimate the spectral reflectance distribution of object using a spectral estimation technique.

Single-shot digital holography using a spectral estimation technique.

We demonstrate a technique capable of obtaining spectral information and a three-dimensional (3D) profile of an object with a single-shot exposure. This technique is based on digital holography and the spectral estimation technique. In the demonstration of this technique, we simultaneously use three laser lines operating at 473, 532, and 633 nm to record the multiple complex amplitudes of the object corresponding to the wavelengths and obtain reconstructed monochrome images of each wavelength.

Single-shot dual-wavelength phase unwrapping in parallel phase-shifting digital holography.

We propose a single-shot phase-unwrapping method using two wavelengths in parallel phase-shifting digital holography (PPSDH). The proposed method enables one to solve the phase ambiguity problem in PPSDH. We conducted an experiment of the proposed method using two lasers whose wavelengths are 473 and 532 nm.

Reflection characteristics of guided-mode resonance filter combined with bottom mirror.

A new type of mirror, based on guided-mode resonance, was proposed and discussed to provide a mirror having high reflectance and large wavelength dependence of reflection phase variation. The proposed mirror consists of a surface grating integrated in a channel waveguide on a high-reflection layer. A SiO2-based device was fabricated for 0.

Space-bandwidth extension in parallel phase-shifting digital holography using a four-channel polarization-imaging camera.

We propose a method for extending the space bandwidth (SBW) available for recording an object wave in parallel phase-shifting digital holography using a four-channel polarization-imaging camera. A linear spatial carrier of the reference wave is introduced to an optical setup of parallel four-step phase-shifting interferometry using a commercially available polarization-imaging camera that has four polarization-detection channels. Then a hologram required for parallel two-step phase shifting, which is a technique capable of recording the widest SBW in parallel phase shifting, can be obtained.

Multiwavelength parallel phase-shifting digital holography using angular multiplexing.

We propose a single-shot digital holography for recording multiwavelength and complex amplitude information by using a single monochromatic image sensor. The zeroth-order wave and conjugate image in each wavelength are removed from a recorded single hologram by applying parallel phase-shifting interferometry. Angular multiplexing is utilized to record the complex amplitude of an object wave in each wavelength separately, and no color filter is required.

Image reconstruction algorithm for recovering high-frequency information in parallel phase-shifting digital holography [Invited].

We propose an image reconstruction algorithm for recovering high-frequency information in parallel phase-shifting digital holography. The proposed algorithm applies three kinds of interpolations and generates three different kinds of object waves. A Fourier transform is applied to each object wave, and the spatial-frequency domain is divided into 3×3 segments for each Fourier-transformed object wave.

Single-shot femtosecond-pulsed phase-shifting digital holography.

Parallel phase-shifting digital holography is capable of three-dimensional measurement of a dynamically moving object with a single-shot recording. In this letter, we demonstrated a parallel phase-shifting digital holography using a single femtosecond light pulse whose central wavelength and temporal duration were 800 nm and 96 fs, respectively. As an object, we set spark discharge in atmospheric pressure air induced by applying a high voltage to between two electrodes.

Algorithm for reconstructing wide space-bandwidth information in parallel two-step phase-shifting digital holography.

We propose an image-reconstruction algorithm of parallel phase-shifting digital holography (PPSDH) which is a technique of single-shot phase-shifting interferometry. In the conventional algorithms in PPSDH, the residual 0th-order diffraction wave and the conjugate images cannot be removed completely and a part of space-bandwidth information is discarded. The proposed algorithm can remove these residual images by modifying the calculation of phase-shifting interferometry and by using Fourier transform technique, respectively.

Single-shot dual-illumination phase unwrapping using a single wavelength.

We propose a single-shot phase unwrapping technique using a single wavelength. In the proposed technique, an object is illuminated by two laser beams, which are emitted from the same laser, whose illumination angles and polarizations are different. Then two types of the object waves generated by the two beams are separately and simultaneously recorded by a polarization imaging camera.