The Maxwellian-view display can provide visual information to people with low vision because retinal images can be formed independently of the refractive power of an eye by using rays converging on ...its pupil. This study presents the holographic Maxwellian-view display, which generates a wavefront converging on the pupil and forming images on the retina. The beam convergent point can be moved electrically in accordance with the pupil movement, and the beam width in the pupil can be changed electrically to control the depth of field of the eye. A compact optical system configuration for the holographic Maxwellian-view display is also proposed. The prototype system was constructed and experimentally tested. Because this holographic technique allows the phase modulation in the pupil, eye aberrations can be corrected; thus, retinal images can be formed for eyes with astigmatism.
A new super multi-view (SMV) display system that enables the number of views to be increased is proposed. All three-dimensional (3D) images generated by multiple multi-view flat-panel displays are ...superimposed on a common screen using a multi-projection system. The viewing zones of the flat-panel 3D display are produced in the pupils of the projection lenses and then imaged to the observation space by a screen lens. Sixteen flat-panel 3D displays having 16 views were used to construct a SMV display having 256 views. The 3D resolution was 256 x 192. The screen size was 10.3 inches. The horizontal interval of the viewing zones was 1.3 mm.
The problems of conventional holographic display techniques, which are the requirements of a sub-micron pixel pitch and ultra-high resolution for spatial light modulators (SLMs) to enlarge the ...viewing zone and screen size, can be addressed using microelectromechanical systems (MEMS) SLMs combined with spatial scanning systems. Various scanning systems have been efficiently combined with high-speed image generation of MEMS SLMs based on the time-multiplexing technique. The horizontal scanning system enlarged the viewing zone and screen size, the circular scanning system provided 360° three-dimensional (3D) images, and the RGB scanning system generated color 3D images. The screen size can be increased scalably using a multichannel system based on the space-multiplexing technique. The use of a short laser pulse illumination system eliminates the mechanical scanning system and greatly simplifies the display system. The measurements of the accommodation responses of human eyes showed that 3D images generated by the screen scanning holographic display have a possibility to solve the visual fatigue issue caused by the vergence–accommodation conflict, which prevents the long-time usage of conventional 3D displays.
Fraunhofer diffraction based computer generated holograms (CGH) adopts a Fourier transform lens that reconstructs the image on the Fourier plane. Fresnel diffraction based CGH directly reconstruct ...the image on the near field, however, the reconstructed image is much farther, which brings difficulty of application. In this paper, a Fresnel transform with the utilization of a Fourier transform lens and a gradient descent based algorithm is proposed to generate holograms of 3D images.
A table screen 360-degree holographic display is proposed, with an increased screen size, having an expanded viewing zone over all horizontal directions around the table screen. It consists of a ...microelectromechanical systems spatial light modulator (MEMS SLM), a magnifying imaging system, and a rotating screen. The MEMS SLM generates hologram patterns at a high frame rate, the magnifying imaging system increases the screen of the MEMS SLM, and the reduced viewing zones are scanned circularly by the rotating screen. The viewing zones are localized to practically realize wavefront reconstruction. An experimental system has been constructed. The generation of 360-degree three-dimensional (3D) images was achieved by scanning 800 reduced and localized viewing zones circularly. The table screen had a diameter of 100 mm, and the frame rate of 3D image generation was 28.4 Hz.
Speckle generation is an inherent problem of holography. A speckle-reduction technique employing a time-multiplexing method is proposed. Object points constituting a reconstructed image are divided ...into multiple object point groups consisting of sparse object points, and the object point groups are displayed time sequentially. The sparseness and temporal summation enable the suppression of speckle generation. The object point group is decomposed into multiple bit planes to represent the grayscale of object points, and binary holograms are generated from the bit plane patterns by using a half-zone plate technique. The binary holograms are displayed by a high-speed spatial light modulator.
•A MEMS SLM enlarges the screen size and the viewing zone of holographic displays.•Speckles can be eliminated from holographic reconstructed images using a MEMS SLM.•MEMS SLMs increase the viewpoints ...and resolution of super multi-view displays.•Multi-view display modules using MEMS projectors enable a large-screen SMV display.
Holographic displays and super multi-view (SMV) displays have been developed to solve the accommodation–vergence conflict that is responsible for visual fatigue caused by the 3D images that are generated by conventional three-dimensional (3D) displays upon which the eye cannot focus. However, holographic and SMV displays provide 3D images upon which the eye can readily focus so that the accommodation–vergence conflict does not occur. Because these two display techniques require the generation of a very large amount of image data, the high data bandwidth of microelectromechanical (MEMS) devices is effectively utilized. The present article describes the holographic display system that employs a MEMS spatial light modulator (SLM), which increases the screen size and viewing zone angle. Two SMV displays are also described, where one employs MEMS SLMs and the other an array of MEMS projectors. The resolution and the number of viewpoints of the SMV displays have increased. Moreover, the technique using a MEMS SLM to eliminate speckles from holographic reconstructed images is also described.
A one-micron pixel pitch is believed to be required for spatial light modulators (SLMs) to realize holographic displays possessing a wide viewing zone. This study proposes the use of a ...microelectromechanical systems (MEMS) SLM for not only displaying holographic patterns but also scanning laser beam. During the rotation of MEMS mirrors in the MEMS SLM, the timing of laser pulses illuminating the MEMS SLM is controlled to change the reflection direction of light modulated by the MEMS SLM in order to enlarge the viewing zone. In this technique, the width of the viewing zone depends on the rotation angle of MEMS mirrors, and not on the pitch of pixels (MEMS mirrors). We experimentally demonstrated the enlargement of the viewing zone angle to ∼40° using the MEMS SLM with a pixel pitch of 13.68 µm.
We introduce digital holographic techniques and recent progress in multidimensional sensing. Digital holography can be used to perform multidimensional imaging of three-dimensional structure, ...dynamics, quantitative phase, multiple wavelengths, and polarization state of light and sensing of a holographic image of nonlinear light and a three-dimensional image of incoherent light.
Abstract
In this review, we introduce digital holographic techniques and recent progress in multidimensional sensing by using digital holography. Digital holography is an interferometric imaging technique that does not require an imaging lens and can be used to perform simultaneous imaging of multidimensional information, such as three-dimensional structure, dynamics, quantitative phase, multiple wavelengths and polarization state of light. The technique can also obtain a holographic image of nonlinear light and a three-dimensional image of incoherent light with a single-shot exposure. The holographic recording ability of this technique has enabled a variety of applications.
Horizontally scanning holography using a spatial light modulator based on microelectromechanical system, which we previously proposed for enlarging both the screen size and the viewing zone, utilized ...a screen scanning system with elementary holograms being scanned horizontally on the screen. In this study, to enlarge the screen size and the viewing zone, we propose a viewing-zone scanning system with enlarged hologram screen and horizontally scanned reduced viewing zone. The reduced viewing zone is localized using converging light emitted from the screen, and the entire screen can be viewed from the localized viewing zone. An experimental system was constructed, and we demonstrated the generation of reconstructed images with a screen size of 2.0 in, a viewing zone width of 437 mm at a distance of 600 mm from the screen, and a frame rate of 60 Hz.
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