Min-Chul Park

Moiré reduction by a diffuser in a multiview 3‐D imaging system

— Diffusers with different characteristics were inserted between the viewing-zone forming optics and the image display panel of a contact-type multiview 3-D imaging system to examine their effects on moire and cross-talk in the system. The diffusers are effective in reducing the moire but induce an increase in cross-talk in most cases. However, a diffuser with the characteristics of a 200-μm-pitch lenticular diffuser or a scatter plate used in mobile phones can be used to reduce moire because it does not cause any noticeable increase in the cross-talk but still preserves the image properties without using a diffuser. This means that a diffuser can be used to reduce moire in a contact-type multiview 3-D imaging system without significantly sacrificing image quality.

Enhancement of PL intensity by photonic crystal fabricated on GaAs substrate using nanoporous alumina mask

We fabricated photonic crystal structure on GaAs substrate using nanoporous alumina mask. Uniform arrays of nano-sized pores produced in anodic alumina were transferred into GaAs substrate by inductively coupled plasma reactive ion etching (ICP-RIE). The photonic crystal structure, the nanohole array with uniform diameter of 60 nm and interpore distance of 105 nm, was formed on GaAs substrate as replica of the alumina mask. Its photoluminescence (PL) showed enhanced intensity compared with that from GaAs substrate without its structure. The ICP-RIE technique using nanoporous alumina mask can be used as a prospective method in the fabrication of nano-devices for nanotechnology.

Depth and width reproducibility of integral photography from multi-view stereoscopic image

Multi-view stereoscopic images were produced via the pick-up method with respect to the object set in the computer, and integral photography was generated from this multi-view stereoscopic image. When the multiview stereoscopic image was taken by pick-up, the optical axis of each camera of the array was aligned with one point in the front of the camera array. A calculation method was derived with respect to the depth position and width of the object displayed by integral photography generated using this method. Based on the derived calculation method, consideration was given to the distortion displayed and reproduced with respect to the depth position and width of the object in the prototyped integral photography.

Compressive sensing with a block-strategy for fast image acquisitions

Compressive sensing is a recent technique that was developed for the reconstruction of large signals from a small number of measurements. It relies on the assumption that the signal to recover is sparse, and the performance of the reconstruction is depending on the level of sparsity. However, in practical case the sparsity of the image to recover is unknown and it is then difficult to estimate the number of measurements necessary to reconstruct the image with a satisfying quality. In this study, we examined a strategy where the image is reconstructed by CS in two steps. A first step with a small number of measurements to estimate the number of points needed, and a second step for the final reconstruction. In addition, we investigated the benefits to create a partition of the image of interest to estimate locally the number of measurements needed for the reconstruction. We demonstrated that our strategy could be used to reconstruct images presenting a PSNR similar to the one obtained with the conventional method, but with fewer measurements.

Holographic and light field displays: What are the differences?

Holographic and light field displays are currently the most researched 3-D imaging technologies. It is considered that the two imaging provide continuous parallaxes so that they can create a natural viewing environment. The main difference of the two imaging lies in their light fields in front of the display panel. The light fields in holographic displays are formed by phase conjugated rays from each hologram point and the light field display by an ever expanding fan beam from each pixel.

Light fields from digital hologram displays

The optical mechanism of forming reconstructed images in a hologram loaded on a DMD is identified by measuring the light fields at different distances from a hologram. The light field images make possible to identify the process of forming the reconstructed image, astigmatism, restoring the missing pattern of the hologram, the focusing behavior of Fresnel zone pattern, and depth resolution.

Requirement for measurement of accommodation response based image blur due to the integral photography

In the first part of this paper, the principle and the development of IP display using computer software were described. Next, the measurement results of accommodation response for the developed IP display were described. As a result, the accommodation response was linearly changed as the depth position of the visual target moved in and out of the range of the depth of focus. On the other hand, the influences generated by the image blur for the accommodation response were investigated experimentally using stereoscopic images. The results showed that the accommodation response was coincident to the convergence point of stereoscopic images with less than 3 cpd spatial resolution. Based on these results, the considerations of the measurement results of the accommodation response for the development IP were examined. The requirements of the measurement condition of accommodation response for IP were also discussed.

Traffic Sign Area Detection System Based on Color Processing Mechanism of Human

The traffic sign on the road should be easy to distinguishable even from far, and should be recognized in a short time. As traffic sign is a very important object which provides important information for the drivers to enhance safety, it has to attract human`s attention among any other objects on the road. This paper proposes a new method of detecting the area of traffic sign, which uses attention module on the assumption that we attention our gaze on the traffic sign at first among other objects when we drive a car. In this paper, we analyze the previous studies of psycophysical and physiological results to get what kind of features are used in the process of human`s object recognition, especially color processing, and with these results we detected the area of traffic sign. Various kinds of traffic sign images were tested, and the results showed good quality(average 97.8% success).