In recent years, real-time video communication over the internet has been widely utilized for applications like video
conferencing. Streaming live video over heterogeneous IP networks, including wireless networks, requires video coding
algorithms that can support various levels of quality in order to adapt to the network end-to-end bandwidth and
transmitter/receiver resources. In this work, a scalable video coding and compression algorithm based on the Contourlet
Transform is proposed. The algorithm allows for multiple levels of detail, without re-encoding the video frames, by just
dropping the encoded information referring to higher resolution than needed. Compression is achieved by means of lossy
and lossless methods, as well as variable bit rate encoding schemes. Furthermore, due to the transformation utilized, it
does not suffer from blocking artifacts that occur with many widely adopted compression algorithms. Another highly
advantageous characteristic of the algorithm is the suppression of noise induced by low-quality sensors usually
encountered in web-cameras, due to the manipulation of the transform coefficients at the compression stage. The
proposed algorithm is designed to introduce minimal coding delay, thus achieving real-time performance. Performance is
enhanced by utilizing the vast computational capabilities of modern GPUs, providing satisfactory encoding and decoding
times at relatively low cost. These characteristics make this method suitable for applications like video-conferencing that
demand real-time performance, along with the highest visual quality possible for each user. Through the presented
performance and quality evaluation of the algorithm, experimental results show that the proposed algorithm achieves
better or comparable visual quality relative to other compression and encoding methods tested, while maintaining a
satisfactory compression ratio. Especially at low bitrates, it provides more human-eye friendly images compared to
algorithms utilizing block-based coding, like the MPEG family, as it introduces fuzziness and blurring instead of
artificial block artifacts.
A miniaturized laser-scanning endoscope is presented that makes use of a composite laser beam for color imaging. A novel approach is followed in the device, which is based on scanning the target tissue with the laser beam using two miniaturized MEMS (microelectromechanical systems) micromirrors and employs specific collection, detection, and postprocessing of the scattered light for reconstructing a color image of the tissue. A resolution of the order of 16 line pairs/mm is achieved for a working distance of 50 mm while the focal depth is larger than 5 mm. Key considerations of the system design are presented, along with results on the operation of the micromirrors, an analysis of the optical design of the endoscope head, and remarks on the assessment of image quality.
One of the most promising techniques for visualizing three-dimensional objects is Integral Photography (IP). Two common methods used in synthetic IP generation involve the development of simplified raytracing algorithms for elementary 3D objects or the realization of pinhole arrays. We present a technique utilizing POVRAY’s raytracing capabilities to generate synthetic, high-quality and photorealistic integral images, by accurately modeling an actual microlens array along with the necessary optics. Our work constitutes a straightforward approach for translating a computer generated 3D model to an IP image and a robust method to develop modules that can be easily integrated in existing raytracers. The proposed technique simulates the procedure of a single stage IP capture, for producing a real orthoscopic IP image. Full control is provided over geometry selection, size and refractive index of the elementary microlenses. Specifically our efforts have been focused on the development of arrays with different geometries (square or hexagonal) in order to demonstrate the parameterization capabilities of the proposed IP setup. Moreover detailed benchmarking is provided over a variety of sizes and geometries of microlens arrays.
A miniaturized laser scanning endoscope is presented which makes use of three lasers to illuminate a sample with a red, a green and a blue wavelength simultaneously. Scattered light from the sample is descanned and chromatically separated into the three channels for detection and postprocessing to compose a color image. The scanning subsystem consists of two micro-electro-mechanical mirrors suitable for mass production. The endoscope head can be assembled fast and at low cost. A resolution of the order of 16 lines per mm is achieved for a working distance common in endoscopy. Considerations of the system design include the operation of the mico mirrors, the filtering of reflected light by using polarization effects and a strategy to cope with color metamery. An expert system based on a neural network was found able to analyze endoscopic images to identify suspicious lesions.
Contemporary methods for minimally invasive interventions are gaining wide acceptance in various everyday operations, offering extremely localized treatment, reduced suffering and practically no risk for the patient as well as great benefits to diagnostic examinations and surgeries that require continuous monitoring. Many established endoscope systems offer the aforementioned advantages without the risks and restrictions of the computer-aided tomography techniques but with limitations in the resolution and chromatic representation provided. A microscanning specific-endoscope device has been developed aiming to provide superior resolution and chromatic representation in comparison with the above endoscopes. The key technology employed in the design of this endoscope relies on the use of tiny microelectro-mechanical silicon mirrors for the scanning of three laser beams over the target tissue area. The so-developed microscanning endoscope system provides color imaging with high resolution at near video rates targeting at macroendoscopy applications. The optical design and implementation of this endoscope system will be presented in this communication together with a brief description of the overall endoscope device developed. In addition results are given from the study of the metamery effect that is utilized in the realized endoscope, together with a presentation of the procedure followed for the objective evaluation of its optical performance and first results from system operation.