The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform

M J Yzuel - One of the best experts on this subject based on the ideXlab platform.

  • Time fluctuations of the phase Modulation in a liquid crystal on silicon display: characterization and effects in diffractive optics
    Optics Express, 2008
    Co-Authors: Angel Lizana, Alejandro Márquez, C Iemmi, E. Fernández, I Moreno, J Campos, M J Yzuel
    Abstract:

    In this paper we provide evidence of the temporal fluctuations of the phase Modulation Property of a liquid crystal on silicon (LCoS) display, and we analyze its effect when the device is used for displaying a diffractive optical element. We use a commercial twisted nematic LCoS display configured to produce a phase-only Modulation, and we provide time resolved measurements of the diffraction efficiency that show rapid fluctuations of the phase Modulation, in the millisecond order. We analyze how these fluctuations have to be considered in two typical methods for the characterization of the phase Modulation: two beam interference and diffraction from a binary grating. We finally provide experimental results on the use of this device for displaying a computer generated hologram. A reduction of the Modulation diffraction efficiency results from the phase Modulation fluctuation.

T. Kamiya - One of the best experts on this subject based on the ideXlab platform.

  • Extremely low-amplitude Modulation in a subharmonically hybrid mode-locked monolithic semiconductor laser
    IEEE Photonics Technology Letters, 1996
    Co-Authors: T. Hoshida, M. Tsuchiya, Y. Ogawa, T. Kamiya
    Abstract:

    Negligibly small amplitude Modulation and sufficiently low timing jitter are achieved simultaneously in a passively mode-locked monolithic semiconductor laser stabilized by applying an electrical signal at the second subharmonic of the pulse repetition frequency. Nearly transform-limited 33 GHz pulse trains with 0.56 ps timing jitter and -23 dBc amplitude Modulation are obtained with 23 dBm driving signals at 16.5 GHz. Detailed investigations are carried out on the dependence of the amplitude Modulation and timing jitter on RF driving power for the second- and third-order subharmonic cases. The excellent amplitude Modulation Property of the second subharmonic case with the specific laser used in this work is ascribed to the frequency response characteristics of the device.

Tomoki Toda - One of the best experts on this subject based on the ideXlab platform.

  • a Modulation Property of time frequency derivatives of filtered phase and its application to aperiodicity and fo estimation
    Conference of the International Speech Communication Association, 2017
    Co-Authors: Hideki Kawahara, Kenichi Sakakibara, Masanori Morise, Hideki Banno, Tomoki Toda
    Abstract:

    We introduce a simple and linear SNR (strictly speaking, periodic to random power ratio) estimator (0dB to 80dB without additional calibration/linearization) for providing reliable descriptions of aperiodicity in speech corpus. The main idea of this method is to estimate the background random noise level without directly extracting the background noise. The proposed method is applicable to a wide variety of time windowing functions with very low sidelobe levels. The estimate combines the frequency derivative and the time-frequency derivative of the mapping from filter center frequency to the output instantaneous frequency. This procedure can replace the periodicity detection and aperiodicity estimation subsystems of recently introduced open source vocoder, YANG vocoder. Source code of MATLAB implementation of this method will also be open sourced.

Angel Lizana - One of the best experts on this subject based on the ideXlab platform.

  • Time fluctuations of the phase Modulation in a liquid crystal on silicon display: characterization and effects in diffractive optics
    Optics Express, 2008
    Co-Authors: Angel Lizana, Alejandro Márquez, C Iemmi, E. Fernández, I Moreno, J Campos, M J Yzuel
    Abstract:

    In this paper we provide evidence of the temporal fluctuations of the phase Modulation Property of a liquid crystal on silicon (LCoS) display, and we analyze its effect when the device is used for displaying a diffractive optical element. We use a commercial twisted nematic LCoS display configured to produce a phase-only Modulation, and we provide time resolved measurements of the diffraction efficiency that show rapid fluctuations of the phase Modulation, in the millisecond order. We analyze how these fluctuations have to be considered in two typical methods for the characterization of the phase Modulation: two beam interference and diffraction from a binary grating. We finally provide experimental results on the use of this device for displaying a computer generated hologram. A reduction of the Modulation diffraction efficiency results from the phase Modulation fluctuation.

Seokhee Jeon - One of the best experts on this subject based on the ideXlab platform.

  • Real Stiffness Augmentation for Haptic Augmented Reality
    Presence, 2011
    Co-Authors: Seokhee Jeon
    Abstract:

    Haptic augmented reality (AR) mixes a real environment with computer-generated virtual haptic stimuli, enabling the system to modulate the haptic attributes of a real object to desired values. This paper reports our second study on this functionality, with stiffness as a goal Modulation Property. Our first study explored the potential of haptic AR by presenting an effective stiffness Modulation system for simple 1D interaction. This paper extends the system so that a user can interact with a real object in any 3D exploratory pattern while perceiving its augmented stiffness. We develop a complete set of algorithms for contact detection, deformation estimation, force rendering, and force control. The core part is the deformation estimation where the magnitude and direction of real object deformation are estimated using a contact dynamics model identified in a preprocessing step. All algorithms are designed in a way that maximizes the efficiency and usability of the system while maintaining convincing perceptual quality. In particular, the need for a large amount of preprocessing such as geometry modeling is avoided to improve the usability. The physical performance of each algorithm is thoroughly evaluated with real samples. Each algorithm is experimentally verified to satisfy the physical performance requirements that need to be satisfied to achieve convincing rendering quality. The final perceptual quality of stiffness rendering is assessed in a psychophysical experiment where the difference in the perceived stiffness between augmented and virtual objects is measured. The error is less than the human discriminability of stiffness, demonstrating that our system can provide accurate stiffness Modulation with perceptually insignificant errors. The limitations of our AR system are also discussed along with a plan for future work.

  • Stiffness Modulation for Haptic Augmented Reality: Extension to 3D interaction
    2010 IEEE Haptics Symposium, 2010
    Co-Authors: Seokhee Jeon, Seungmoon Choi
    Abstract:

    Haptic Augmented Reality (AR) allows a user to touch a real environment augmented with synthetic haptic stimuli. For example, medical students can palpate a virtual tumor inside a real mannequin using a haptic AR system to practice cancer detection. To realize such functionality, we need to alter the haptic attributes of a real object by means of virtual haptic feedback. Previously, we presented a haptic AR system with stiffness as a goal Modulation Property, and demonstrated its competent physical and perceptual performances for 1D interaction. In this paper, we extend the system so that a user can interact with a real object in any 3D exploratory pattern while perceiving its augmented stiffness. A series of algorithms are developed for contact detection, deformation estimation, force rendering, and force control. Their performances are thoroughly evaluated with real samples. A particular focus has been on minimizing the amount of preprocessing such as geometry modeling. Our haptic AR system can provide convincing stiffness Modulation for real objects of relatively homogeneous deformation properties. The limitations of our AR system are also discussed along with a plan for future work.