Showing papers by "Yoichi Miyake published in 2006"

Evaluation of Image Corrected by Retinex Method Based on S-CIELAB and Gazing Information

Abstract: The purpose of this research is to propose an effective color metric which can predict the perceptual image quality for Retinex method. In this paper, we first give a brief introduction of three kinds of typical single Retinex methods to improve the color reproduction. And then, we state the process for obtaining the observer rating value from the subjective evaluation experiment performed under the sRGB illumination condition. Next, we introduce the S-CIELAB metric and propose a new metric on the basis of S-CIELAB metric that considers the gazing information. The average S-CIELAB color differences with and without the consideration of gazing information were calculated as the objective image quality measures. The correlations between the observer rating values and the objective image quality measures were calculated. The result shows that all of the average S-CIELAB color differences based on the gazing information are better correlated to the observer rating value than the average S-CIELAB color difference over the whole area. The average S-CIELAB color difference weighted by the gazing frequency over the gazing area shows the strong correlation with the observer rating value.

Spectral Based Color Correction Technique Compatible with Standard RGB System

Abstract: A spectral turn method is presented as a spectral based color correction method compatible with the standard RGB system by applying the idea of a multi-spectral method. The multi-spectral based color reproduction technique has been proposed for providing independent color of device and viewing conditions. However, it is difficult to replace the RGB devices with high cost multi-spectral devices since the latter have advanced only to the laboratory level. In the proposed method, the standard RGB values are converted into spectral information, then returned to RGB values for different viewing conditions. This process provides more accurate reproduction than the conventional forward process of the color reproduction. An experiment of psychophysical color matching was performed to evaluate the technique. The mixed chromatic adaptation model was applied to the method in the experiment, and the results showed the effectiveness of the proposed method.

Super Resolution Method Using Texton Substitution

Abstract: The resolution of a texture image in computer graphics is determined by the camera system used to take the image. Zooming in on the object beyond the optical resolution results in a loss of edges and details. We developed a “super resolution” method that uses a database of textures and texton substitution to create plausible high-frequency detail in enlarged texture images. Conventional example-based super-resolution techniques involve a high computational cost and users must provide the optimal parameters for the input image. Using texton in the wavelet space and a pixel-based (not a patch-based) substitution reduces the computational cost.

Real-time deformations of organ based on structural mechanics for surgical simulators

Abstract: This research proposes the deformation model of organs for the development of the medical training system using Virtual Reality (VR) technology. First, the proposed model calculates the strains of coordinate axis. Secondly, the deformation is obtained by mapping the coordinate of the object to the strained coordinate. We assume the beams in the coordinate space to calculate the strain of the coordinate axis. The forces acting on the object are converted to the forces applied to the beams. The bend and the twist of the beams are calculated based on the theory of structural mechanics. The bend is derived by the finite element method. We propose two deformation methods which differ in the position of the beams in the coordinate space. One method locates the beams along the three orthogonal axes (x, y, z). Another method locates the beam in the area where the deformation is large. In addition, the strain of the coordinate axis is attenuated in proportion to the distance from the point of action to consider the attenuation of the stress which is a viscoelastic feature of the organs. The proposed model needs less computational cost compared to the conventional deformation method since our model does not need to divide the object into the elasticity element. The proposed model was implemented in the laparoscopic surgery training system, and a real-time deformation can be realized.

Rigid core particle: stabilization technique in large time step fluid simulation

Abstract: One of the most serious bottle-necks in fluid simulation occurs because the time step must be set to a small value to avoid numerical instability. To overcome this problem, this paper introduces a rigid core for the particles to maintain stability in particle-based fluid simulations. The fluid dynamics is calculated using the particle-based method with smoothed particle hydrodynamics (SPH) [Muller et al. 2003]. By using continuous collision detection (CCD) [Redon et al. 2001] among the rigid cores, unnatural compression and expansion can be prevented in large time step simulations. The calculation cost of CCD is negligible compared to that of small time step simulations, since CCD can be accelerated by a physics processing unit (PPU). Furthermore, this paper proposes a new real-time surface visualization technique that can also be assisted by a PPU. This technique generates large-scale high-resolution meshes compared to those generated by conventional lattice-based methods.

Photometric HDR video for visual adaptation models

Abstract: time time time Input video Tone-mapping to input video Tone-mapping to PHDR video Figure 1: Photometric High Dynamic Range (PHDR) video sequences of an indoor and outdoor scene. Top row: An input video sequence captured by a digital video camera. Middle row: A reference result (a tone-mapped input sequence by using visual adaptation models). Bottom row: The result of our proposed method (a tone-mapped PHDR video sequence).

Spectral based color reproduction for print illuminated by image projector

Abstract: In this paper, we propose a new color matching method between a proof and a target print by using a projection display system based on the spectral color reproduction. In this method, a color of proof is corrected by synthesizing a projection image which is calculated to minimize the color difference between each print. The radiance of the proof and the target print are calculated by using the reflectance of the prints and the radiance from the projector, and we use the method based on the XYZ tristimulus values (colorimetric method) and the spectral values (spectral-based method). We compared the color difference between the colorimetric method and spectral-based method. The average color difference ΔE* 94 by using the colorimetric method was 4.00. On the other hand, the color difference used the spectralbased method was 2.13. From these results, we concluded that the spectral-based method is more effective than the colorimetric method to perform the accurate color reproduction by synthesizing the projection color and the proof.

Reconstruction of the Point-Spread Function of the Human Eye Using a New Phase-Retrieval Algorithm

Abstract: The double-pass method is thought to obtain the point spread function (PSF) in human eyes based on two techniques: the symmetric double-pass method using the same pupil size and the asymmetric double-pass method using a different pupil size. The symmetric double-pass method provides autocorrelation of the retinal PSF and, thus, the modulation transfer function. The asymmetric double-pass method provides low-frequency partial-phase information and the partial phase-retrieval algorithm is applied to obtain the complete-phase information, and to estimate the PSF. The partial phase-retrieval algorithm is based on the iteration method proposed by Fineup and Kowalczyk and requires a lengthy computation. In this study, we propose a new high-speed phase-retrieval algorithm based on the property that the real and imaginary parts of optical transfer functions (OTFs) continuously change in value.

Designing flat-bed scanning system for spectral and glossiness recording

Abstract: In this paper, we propose a flat-bed scanner system to record spectral and glossiness information for various sheets like objects. In the proposed system, five filters are used to acquire the multi-band images of the object. The spectral reflectance image can be estimated and be recorded from the multi-band images. The glossiness of the object is recorded as two images taken by the different geometries about illuminant which is from 45 degrees, and from 0+α degrees respectively when the averaged normal vector of the sheet like object is defined as 0 degree. We performed two types of computer simulation by using the two images to reproduce various appearance of recorded object. As the first simulation, the various appearances of image are reproduced through a weighted linear combination of the two images. As the second simulation, the normal vector distribution of the object is estimated from the image taken by 45 degree illuminant. By using this normal vector distribution, roughness of the object is estimated from the image taken by 0 + α degree illuminant. The normal vector and estimated roughness are used to reproduce the various appearance of the object under arbitrary illuminant.

An evaluation of sharpness in different image displays used for medical imaging

Abstract: X-ray film systems have been widely used for a diagnosis of various diseases since a long time ago. In recent years, many kinds of displays and recording systems for X-ray medical images have been used including inkjet printer, silver halide film, CRT and LCD, by the development of the digital X-ray image capturing systems. In this paper, image quality of X-ray images displayed onto high accurate monochrome CRT and LCD monitors are analyzed and compared. Images recorded on the exclusive film and coated paper by inkjet printer and the wet type and dry type photo printers using a silver halide material are also analyzed and compared. The modified Gan's method is introduced to calculate the MTF (Modulation Transfer Function) from the knife ESF (edge spread function). The results show that the MTFs of the inkjet image on the transparency and the wet type silver halide film image have fairly similar and good response in comparison with the inkjet image on the coated paper and the dry type silver halide film. It is also shown that the CRT has the worse response over the spatial frequency range. It was well correlated between the MTF and observer rating value. From here, we consider the proposed method is effective.