Incoherent color digital holography with computational coherent superposition for fluorescence imaging [Invited].

We present color fluorescence imaging using an incoherent digital holographic technique in which holographic multiplexing of multiple wavelengths is exploited. Self-interference incoherent digital holography with a single-path in-line configuration and the computational coherent superposition scheme are adopted to obtain color holographic three-dimensional information of self-luminous objects with a monochrome image sensor and no mechanical scanning. We perform not only simultaneous color three-dimensional sensing of multiple self-luminous objects but also color fluorescence imaging of stained biological samples.

Two-step phase-shifting interferometry for self-interference digital holography.

We propose a phase-shifting interferometry technique using only two in-line phase-shifted self-interference holograms. There is no requirement for additional recording or estimation in the measurement. The proposed technique adopts a mathematical model for self-interference digital holography.

Multiwavelength three-dimensional microscopy with spatially incoherent light, based on computational coherent superposition.

In this Letter, we propose spatially incoherent multiwavelength three-dimensional (3D) microscopy that exploits holographic multiplexing and is based on computational coherent superposition (CCS). The proposed microscopy generates spatially incoherent wavelength-multiplexed self-interference holograms with a multiband-pass filter and spatially and temporally incoherent light diffracted from specimens. Selective extractions of 3D spatial information at multiple wavelengths from the holograms are realized using the CCS scheme.

Multiwavelength-multiplexed phase-shifting incoherent color digital holography.

We propose multiwavelength-multiplexed phase-shifting incoherent color digital holography. In this technique, a monochrome image sensor records wavelength-multiplexed, phase-shifted, and incoherent holograms, and a phase-shifting interferometry technique selectively extracts object waves at multiple wavelengths from the several recorded holograms. Spatially incoherent light that contains multiple wavelengths illuminates objects, and multiwavelength-incoherent object waves are simultaneously obtained without using any wavelength filters.

Reconstruction of a three-dimensional color-video of a point-cloud object using the projection-type holographic display with a holographic optical element.

Here, we managed to reconstruct a three-dimensional color video of a point-cloud object using a projection-type holographic display with a holographic optical element as an optical screen. The holographic optical element has the function of an off-axis concave mirror and has been created by the wavefront printer digitally. We defined and implemented an algorithm to reconstruct a three-dimensional image at a chosen position considering the specification of the holographic optical element designed digitally.

Homography based identification for automatic and robust calibration of projection integral imaging displays.

Recent advances in the creation of microlens arrays as holographic optical elements allow the creation of projector-based see-through light field displays suitable for augmented reality. These systems require an accurate calibration of the projector with relation to the microlens array, as any small misalignment causes the 3D reconstruction to fail. The methods reported so far require precise placement of the calibration camera w.

Digitally designed holographic optical element for light field displays.

Concave micro-mirror arrays fabricated as holographic optical elements are used in projector-based light field displays due to their see-through characteristics. The optical axes of each micro-mirror in the array are usually made parallel to each other, which simplifies the fabrication, integral image rendering, and calibration process. However, this demands that the beam from the projector be collimated and made parallel to the optical axis of each elemental micro-mirror.

Copying of holograms by spot scanning approach.

To replicate holograms, contact copying has conventionally been used. In this approach, a photosensitive material is fixed together with a master hologram and illuminated with a coherent beam. This method is simple and enables high-quality copies; however, it requires a large optical setup for large-area holograms.

Real-time colour hologram generation based on ray-sampling plane with multi-GPU acceleration.

Although electro-holography can reconstruct three-dimensional (3D) motion pictures, its computational cost is too heavy to allow for real-time reconstruction of 3D motion pictures. This study explores accelerating colour hologram generation using light-ray information on a ray-sampling (RS) plane with a graphics processing unit (GPU) to realise a real-time holographic display system. We refer to an image corresponding to light-ray information as an RS image.

Projection-type see-through holographic three-dimensional display.

Owing to the limited spatio-temporal resolution of display devices, dynamic holographic three-dimensional displays suffer from a critical trade-off between the display size and the visual angle. Here we show a projection-type holographic three-dimensional display, in which a digitally designed holographic optical element and a digital holographic projection technique are combined to increase both factors at the same time. In the experiment, the enlarged holographic image, which is twice as large as the original display device, projected on the screen of the digitally designed holographic optical element was concentrated at the target observation area so as to increase the visual angle, which is six times as large as that for a general holographic display.

Large size three-dimensional video by electronic holography using multiple spatial light modulators.

In this paper, we propose a new method of using multiple spatial light modulators (SLMs) to increase the size of three-dimensional (3D) images that are displayed using electronic holography. The scalability of images produced by the previous method had an upper limit that was derived from the path length of the image-readout part. We were able to produce larger colour electronic holographic images with a newly devised space-saving image-readout optical system for multiple reflection-type SLMs.

Image size scalable full-parallax coloured three-dimensional video by electronic holography.

In electronic holography, various methods have been considered for using multiple spatial light modulators (SLM) to increase the image size. In a previous work, we used a monochrome light source for a method that located an optical system containing lens arrays and other components in front of multiple SLMs. This paper proposes a colourization technique for that system based on time division multiplexing using laser light sources of three colours (red, green, and blue).

Band-limited double-step Fresnel diffraction and its application to computer-generated holograms.

Double-step Fresnel diffraction (DSF) is an efficient diffraction calculation in terms of the amount of usage memory and calculation time. This paper describes band-limited DSF, which will be useful for large computer-generated holograms (CGHs) and gigapixel digital holography, mitigating the aliasing noise of the DSF. As the application, we demonstrate a CGH generation with nearly 8K × 4K pixels from texture and depth maps of a three-dimensional scene captured by a depth camera.

Real-time capture and reconstruction system with multiple GPUs for a 3D live scene by a generation from 4K IP images to 8K holograms.

We developed a real-time capture and reconstruction system for three-dimensional (3D) live scenes. In previous research, we used integral photography (IP) to capture 3D images and then generated holograms from the IP images to implement a real-time reconstruction system. In this paper, we use a 4K (3,840 × 2,160) camera to capture IP images and 8K (7,680 × 4,320) liquid crystal display (LCD) panels for the reconstruction of holograms.

3D objects enlargement technique using an optical system and multiple SLMs for electronic holography.

One problem in electronic holography, which is caused by the display performance of spatial light modulators (SLM), is that the size of reconstructed 3D objects is small. Although methods for increasing the size using multiple SLMs have been considered, they typically had the problem that some parts of 3D objects were missing as a result of the gap between adjacent SLMs or 3D objects lost the vertical parallax. This paper proposes a method of resolving this problem by locating an optical system containing a lens array and other components in front of multiple SLMs.

Calculating the Fresnel diffraction of light from a shifted and tilted plane.

We propose a technique for calculating the diffraction of light in the Fresnel region from a plane that is the light source (source plane) to a plane at which the diffracted light is to be calculated (destination plane). When the wavefield of the source plane is described by a group of points on a grid, this technique can be used to calculate the wavefield of the group of points on a grid on the destination plane. The positions of both planes may be shifted, and the plane normal vectors of both planes may have different directions.

Simplified homography matrix for a large-scale camera array system.

We want to use a large-scale camera array system in which each camera is placed at the desired position to photograph a subject and later render images of the subject viewed from various directions or render images for a three-dimensional display. The homography matrix for each camera should be calculated in advance to correct the captured images. In the case that each camera is physically facing toward the subject as precisely as possible but the captured image still includes geometrical distortion, if the expected error in the deviations from the ideal directions is assumed to be the zero vector, the homography matrix of each camera can be easily obtained.

Fast calculation of computer-generated-hologram on AMD HD5000 series GPU and OpenCL.

In this paper, we report fast calculation of a computer-generated-hologram using a new architecture of the HD5000 series GPU (RV870) made by AMD and its new software development environment, OpenCL. Using a RV870 GPU and OpenCL, we can calculate 1,920 x 1,024 resolution of a CGH from a 3D object consisting of 1,024 points in 30 milli-seconds. The calculation speed realizes a speed approximately two times faster than that of a GPU made by NVIDIA.

One-unit system to reconstruct a 3-D movie at a video-rate via electroholography.

We have developed a one-unit system, including creating and displaying a hologram for real-time reproduction of a three-dimensional image via electroholography. We have constructed this one-unit system by connecting a special-purpose computer for holography and a special display board with a reflective liquid crystal display as a spatial light modulator. Using this one-unit system, we succeeded in reproducing a three-dimensional image composed of 10,000 points at a speed of 30 frames per second, which is the video rate in NTSC format.

Simplified electroholographic color reconstruction system using graphics processing unit and liquid crystal display projector.

We have constructed a simple color electroholography system that has excellent cost performance. It uses a graphics processing unit (GPU) and a liquid crystal display (LCD) projector. The structure of the GPU is suitable for calculating computer-generated holograms (CGHs).

HORN-6 special-purpose clustered computing system for electroholography.

We developed the HORN-6 special-purpose computer for holography. We designed and constructed the HORN-6 board to handle an object image composed of one million points and constructed a cluster system composed of 16 HORN-6 boards. Using this HORN-6 cluster system, we succeeded in creating a computer-generated hologram of a three-dimensional image composed of 1,000,000 points at a rate of 1 frame per second, and a computer-generated hologram of an image composed of 100,000 points at a rate of 10 frames per second, which is near video rate, when the size of a computer-generated hologram is 1,920 x 1,080.