Kyung-Ae Moon

A text watermarking algorithm based on word classification and inter-word space statistics

Text documents can be watermarked by patterning theinter-word spaces. This paper proposes a textwatermarking algorithm that exploits the novel conceptsof word classification and inter-word space statistics. Thewords are classified using some features. Severaladjacent words are grouped into a segment, and thesegments are also classified using the word classinformation. The same amount of information is insertedinto each of the segment classes. The information isencoded by modifying some statistics of inter-word spacesof the segments belonging to the same class. Severaladvantages over the conventional word-shift algorithmsare discussed.

Holographic display based on a spatial DMD array.

The image space of the reconstructed image from the hologram displayed on a digital micromirror device (DMD) is defined by the diffraction pattern induced by the 2D pixel pattern of the DMD, which works as a 2D blazed grating. Within this space, a reconstructed image of 100 mm × 20 mm is spatially multiplexed by a 2 × 5 DMD array that is aligned on a board, without using any extra optics. Each DMD chip reconstructs an image piece of the size 20 mm (width) × 10 mm (height). The reconstructed image looks somewhat noisy but regenerates the original object image faithfully.

An efficient extraction of character string positions using morphological operator

An efficient extraction of character string positions in a document is proposed by using a morphological operator. In regions of character strings, axial edge pixels and diagonal edge pixels are mingled together, but in other regions, they are distributed separately. Based on this difference in the directional edge pixel distribution between the character and the non-character regions, string positions are extracted directly from arbitrary blocks without any block analysis, in contrast to previous work which requires block analysis to extract string positions (F.M. Wahl et al., 1982; S. Imade et al., 1993). Experiments are conducted on the document images acquired through the scanner, and the proposed method can directly extract the character string positions from the plain text of character blocks, and even from the document containing tables and flow-charts, without any block analysis.

Segmentation of a text printed in Korean and English using structure information and character recognizers

The purpose of the research presented is to segment a text image printed in both Korean and English into character images, utilizing the structure information in Korean and English characters, and using a Korean, English and mixed language character recognizer. The image cannot be separated by only using the width and height of a character because those of an English character are not constant, contrary to those of a Korean character. Therefore we first classify the image into Korean or English using the structure information in Korean and English characters. If it is determined as a Korean character, we segment it with the average width of Korean characters in the text lines. If it is determined as an English character, we segment it using a classical method to segment touching alphanumeric characters. If it cannot be determined, we find possible cut points using a vertical histogram and use the mixed language recognizer to determine the right cut point. Since our method first classifies a block into Korean or English, it can be run faster than the traditional method that cannot identify the language. Each classified block can be segmented more accurately because more specific knowledge about Korean and English characters can be applied.

Measurement of depth representation using integral imaging for quality evaluation of computer-generated hologram

We demonstrate the depth measurement method of holographic images using integral imaging. The depth information of holographic images can be obtained with a single capture by conventional integral imaging pickup system composed of a micro lens array (MLA) and an image sensor. In order to verify the feasibility of our proposed method, an elemental image set of holographic images formed by a MLA was generated by a computer, and then refocused images at different planes were reconstructed numerically using computational integral imaging reconstruction (CIIR) technique for depth measurement. Note that we set the distance between MLA and image sensor as focal length of micro lens for large depth of focus. From the numerical results, we can measure the depth representation of holographic images successfully. However, refocused images from an optically captured elemental image set provide poor depth discrimination due to expected error in distance between MLA and image sensor. Only an object in a particular narrow depth range can be focused clearly when the image sensor is placed out of the MLA focal plane. The simulated results in this condition matched reasonably with the experiment result.

Holographic stereogram printing under the non-vibration environment

Printing the holographic stereogram (HS) is vulnerable to the vibration when the holographic film is exposed to the continuous wave laser beam compared to the pulsed laser. The continuous wave laser is required to be more longer exposed to the holographic film for forming the fringe pattern, hence the optical system is normally set up on the antivibration system such as optical table which could be a latent defect considering the commercially available printer. This paper covers the design of holographic stereogram printing system which is built upon the non-vibration environment where the ambient noises exist. In order to build a robust system under the common sources of vibration, we designed the optical system which can minimize the effects of ambient noise as well as reduce the optical vibrations. The main source of the noise comes from the stage that transfers the hologram plate hogel by hogel. In order to accelerate the film transportation, we devised and applied an anti-vibration algorithm which can reduce the vibration significantly and the open frame architecture as well. The holographic stereogram printing is conducted using the one-step full parallax stereograms which are generated by setting up the re-centered camera. The optical system features single signal beam converging module to minimize the optical components and tailored optical components. An open frame film stage is integrated into the HS system. For the experiments, the horizontal and full parallax 1mmx1mm, 50x50 and 100x100 hogels are printed to verify the proposed HS printing system.

Interactive rich media player based on MPEG-4 LASeR

This paper presents the interactive rich media player based on MPEG-4 LASeR. A Rich media service is dynamic, interactive collection of multimedia data such as audio, video, graphics and text. And LASeR tunes and optimizes each feature required by rich media services to effectively fulfill the need of an open standard. Throughout this paper, we will introduce the usage of interactive rich media service, a technical overview of MPEG-4 LASeR. And the implementation of the interactive rich media player and its capabilities are presented along with usage examples.

Analysis of effects of depth map compression on digital holograms

This paper presents an analysis of effects of depth map compression on digital holograms. The applicability of conventional depth coding tools such as depth down-sampling and view synthesis distortion in digital holograms is reviewed by analyzing of effects of depth map compression on quality of digital hologram.

Rate-distortion optimal motion estimation for depth map coding

This paper presents a rate-distortion (RD) optimal motion estimation for depth coding. The view synthesis distortion is widely used in 3D video coding since it is a good approach to reduce the depth bit-rate without degradation of rendering quality. However, view synthesis distortion method is only applied to a mode decision process until now. The proposed method applies the view synthesis distortion to motion estimation process and achieves 0.41% bit-rate saving for AVC-compatible 3D video coding.

Large-scale color holographic display capable of steering view window

We present optical fiber based large-scale color holographic three-dimensional display using a pupil tracking technique for wide viewing angle display applications. One of the limitations in implementing a large-scale holographic three-dimensional display is the restrictive space-bandwidth product of the spatial light modulator. In our proposed method, motor control system for steering optical fibers as a light guide and pupil tracking system are used to overcome the limitation of space-bandwidth product by steering the view window according to a position of the pupil of the observer. The proposed method employing the holographic stereogram in order to deliver two holographic patterns of different perspectives of a 3D scene to both eyes of the observer, which successfully provides both of the accommodation and binocular disparity.