Piotr Garbat

Wide angle holographic display system with spatiotemporal multiplexing.

This paper presents a wide angle holographic display system with extended viewing angle in both horizontal and vertical directions. The display is constructed from six spatial light modulators (SLM) arranged on a circle and an additional SLM used for spatiotemporal multiplexing and a viewing angle extension in two perpendicular directions. The additional SLM, that is synchronized with the SLMs on the circle is placed in the image space. This method increases effective space bandwidth product of display system data from 12.4 to 50 megapixels. The software solution based on three Nvidia graphic cards is developed and implemented in order to achieve fast and synchronized displaying. The experiments presented for both synthetic and real 3D data prove the possibility to view binocularly having good quality images reconstructed in full FoV of the display.

Multiwavefront digital holographic television.

This paper presents the full technology chain supporting wide angle digital holographic television from holographic capture of real world objects/scenes to holographic display with an extended viewing angle. The data are captured with multiple CCD cameras located around an object. The display system is based on multiple tilted spatial light modulators (SLMs) arranged in a circular configuration. The capture-display system is linked by a holographic data processing module, which allows for significant decoupling of the capture and display systems. The presented experimental results, based on the reconstruction of real world, variable in time scenes, illustrates imaging dynamics, viewing angle and quality.

3D visualization of true variable in time objects based on data from optical measurement system

The biggest challenges in multimedia technologies are connecting with createing fully interactive virtual reality (VR) systems. This requires generating numerically or even better gathering real data about static or dynamic 3D objects and scenes and delivering them to virtual reality environment. Application of the structure light measurement system based on digital light projection supported by special data coding and processing technology allow to record 3D data with significantly higher accuracy of reconstructed shape and simplified data manipulation process. In the paper the general concept of virtual reality system supported by data gathered by means of structure light projection is presented. The methodology of conversion of cloud of measurement points (x,y,z,R,G,B) into virtual reality environment is described. The methodology of real time visualization of variable in time 3D object based on its coding by means of specially formed contours and their B-spline approximation is presented. The applicability of the methodology has been shown at the case of real object monitoring. The total processing path was successfully tested.

Wide angle digital holographic interferometry with real-time optical reconstruction

The paper presents the way that colour can serve solving the problem of calibration points indexing in a camera geometrical calibration process. We propose a technique in which indexes of calibration points in a black-and-white chessboard are represented as sets of colour regions in the neighbourhood of calibration points. We provide some general rules for designing a colour calibration chessboard and provide a method of calibration image analysis. We show that this approach leads to obtaining better results than in the case of widely used methods employing information about already indexed points to compute indexes. We also report constraints concerning the technique. Nowadays we are witnessing an increasing need for camera geometrical calibration systems. They are vital for such applications as 3D modelling, 3D reconstruction, assembly control systems, etc. Wherever possible, calibration objects placed in the scene are used in a camera geometrical calibration process. This approach significantly increases accuracy of calibration results and makes the calibration data extraction process easier and universal. There are many geometrical camera calibration techniques for a known calibration scene [1]. A great number of them use as an input calibration points which are localised and indexed in the scene. In this paper we propose the technique of calibration points indexing which uses a colour chessboard. The presented technique was developed by solving problems we encountered during experiments with our earlier methods of camera calibration scene analysis [2]-[3]. In particular, the proposed technique increases the number of indexed points points in case of local lack of calibration points detection. At the beginning of the paper we present a way of designing a chessboard pattern. Then we describe a calibration point indexing method, and finally we show experimental results. A black-and-white chessboard is widely used in order to obtain sub-pixel accuracy of calibration points localisation [1]. Calibration points are defined as corners of chessboard squares. Assuming the availability of rough localisation of these points, the points can be indexed. Noting that differences in distances between neighbouring points in calibration scene images differ slightly, one of the local searching methods can be employed (e.g. [2]). Methods of this type search for a calibration point to be indexed, using a window of a certain size. The position of the window is determined by a vector representing the distance between two previously indexed points in the same row or column. However, experiments show that this approach has its disadvantages, as described below. * E-mail: A.Nowakowski@ire.pw.edu.pl Firstly, there is a danger of omitting some points during indexing in case of local lack of calibration points detection in a neighbourhood (e.g. caused by the presence of non-homogeneous light in the calibration scene). A particularly unfavourable situation is when the local lack of detection effects in the appearance of separated regions of detected calibration points. It is worth saying that such situations are likely to happen for calibration points situated near image borders. Such points are very important for the analysis of optical nonlinearities, and a lack of them can significantly influence the accuracy of distortion modelling. Secondly, such methods may give wrong results in the case of optical distortion with strong nonlinearities when getting information about the neighbouring index is not an easy task. Beside this, the methods are very sensitive to a single false localisation of a calibration point. Such a single false localisation can even result in false indexing of a big set of calibration points. To avoid the above-mentioned problems, we propose using a black-and-white chessboard which contains the coded index of a calibration point in the form of colour squares situated in the nearest neighbourhood of each point. The index of a certain calibration point is determined by colours of four nearest neighbouring squares (Fig.1). An order of squares in such foursome is important. Because the size of a colour square is determined only by the possibility of correct colour detection, the size of a colour square can be smaller than the size of a black or white square. The larger size of a black or white square is determined by the requirements of the exact localisation step which follows the indexing of calibration points [3]. In this step, edge information is extracted from a blackand-white chessboard. This edge information needs larger Artur Nowakowski, Wladyslaw Skarbek Institute of Radioelectronics, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warszawa, A.Nowakowski@ire.pw.edu.pl Received February 10, 2009; accepted March 27, 2009; published March 31, 2009 http://www.photonics.pl/PLP

3D Shape measurement system based on structure light and polarization analysis

The problem of 3D shape acquisition has received increasing attention in recent years. Recently the structure light measurements system based on digital light projection supported by processing allow to rapid acquisition of data about 3D real objects. Obtaining 3D shape of objects in optically scattering media presents a challenging set of problems. Many applications for 3D imaging through fog, dust, mist, rain and turbid water require improving the quality of data obtained in scattered media. Presented 3D shape measurement system is supported by polarization image analysis. Enhancement of image quality is realized using the detector unit with special liquid crystal filter.

Real time visualization of 3D variable in time object based on cloud of points data gathered by coloured structure light projection system

The problem of virtual view creation has received increasing attention in recent years. Major current approaches are based on modified stereo vision systems. Recently the structure light measurement system based on digital light projection supported by special data coding and processing allow to rapid 3D shape acquisition. Application of this technology to record 3D data has increased significantly the accuracy of reconstructed shape and simplified data manipulation process. In the paper the general concept of virtual reality system supported by data gathered by means of structure light projection is presented. The methodology of conversion of cloud of measurement points (x,y,z,R,G,B) into virtual reality environment is described. It is supported by implementation of a virtual camera concept, as the mean for interactive object visualization. The methodology of real time 3D object visualization based on its coding by means of specially formed contours and their B-spline approximation is presented. The applicability of the methodology has been shown on numerically generated data which simulate performance of the measurement system. The total processing path was successfully tested.

Optonumerical system supporting visualization of true 3D variable in time objects in virtual reality environment

Fulfilling the recent needs of visualization of variable in time 3D objects in virtual reality environment requires development of new approach towards combining rapid 3D shape measurement with data filtering, coding and streaming. These operations have to enable performing real-time transmission and visualization of 3D data in virtual reality. In the paper the novel system based on digital structure light projection applied to gather 3D data representing variable in time objects and extended numerical procedures coupled with virtual camera concept for interactive object visualization is presented. The proposed measurement and data processing methodology has been verified successfully at computer generated models of moving and morphing 3D objects. Both types of data have been visualized with the average frequency of 10 frames per second in virtual reality environment.

Review of terahertz image enhancement techniques

In recent years we have seen significant progress in the terahertz imaging technology. The improvement of imaging quality is significant an imaging system. It is still a big challenge to find effective image filtration methods. In this paper, we study methods from three different groups: time-dependent methods, spatial-dependent methods and spatiotemporal methods.

Products recognition on shop-racks from local scale-invariant features

This paper presents a system designed for the multi-object detection purposes and adjusted for the application of product search on the market shelves. System uses well known binary keypoint detection algorithms for finding characteristic points in the image. One of the main idea is object recognition based on Implicit Shape Model method. Authors of the article proposed many improvements of the algorithm. Originally fiducial points are matched with a very simple function. This leads to the limitations in the number of objects parts being success- fully separated, while various methods of classification may be validated in order to achieve higher performance. Such an extension implies research on training procedure able to deal with many objects categories. Proposed solution opens a new possibilities for many algorithms demanding fast and robust multi-object recognition.

Multi-object Tracking System

The article describes the multi-object tracking system based on new approach to object management after preprocessing and background modeling. Object manager determine correlation between objects in previous and current frame by matching features. For matching features algorithm use color histogram with a small number of bins. Each moving object extracted from the scene is assigned to an individual and independent Kalman filter. System stores information about real position of the objects extracted directly from image processing and keep information about centroids predicted by Kalman filter.