Knowledge Of Camera Research Articles

Understanding of indoor scenes based on projection of spatial rectangles

Understanding of indoor scenes has considerable value in mission planning and monitoring in robots. This has become one of the biggest challenges in computer vision because of the diversity and changeability of 3D indoor scenes. Indoor scenes can be considered compositions of many planes in which most common external surfaces are rectangles, such as doors, windows, walls, tables. These spatial rectangles are projected into 2D projections with special geometric configurations, which may enable us to estimate their original orientation and position in 3D scenes. In this paper, the study presents a method to efficiently reconstruct 3D indoor scene without any knowledge of camera’s internal calibration. The approach first found quadrangles composed of lines. Through the projection of spatial rectangles, our method not only can estimate room layout of scene, but also can reconstruct excellent details of scene. Due to simple geometric inferences, our method can cope with clutter without prior training, making it practical and efficient for a navigating robot. We compare the room layout estimated by our algorithm against room box ground truth, measuring the percentage of pixels that were classified correctly. Furthermore, we evaluate our ability to fit the indoor scene by comparing against the details that were reconstructed correctly in scene. The experiments showed that our method is capable of reconstructing various structures of indoor environments and that the accuracy and speed of this method meet the requirements a of indoor robot navigation.

Performance analysis for automated gait extraction and recognition in multi-camera surveillance

Many studies have confirmed that gait analysis can be used as a new biometrics. In this research, gait analysis is deployed for people identification in multi-camera surveillance scenarios. We present a new method for viewpoint independent markerless gait analysis that does not require camera calibration and works with a wide range of walking directions. These properties make the proposed method particularly suitable for gait identification in real surveillance scenarios where people and their behaviour need to be tracked across a set of cameras. Tests on 300 synthetic and real video sequences, with subjects walking freely along different walking directions, have been performed. Since the choice of the cameras’ characteristics is a key-point for the development of a smart surveillance system, the performance of the proposed approach is measured with respect to different video properties: spatial resolution, frame-rate, data compression and image quality. The obtained results show that markerless gait analysis can be achieved without any knowledge of camera’s position and subject’s pose. The extracted gait parameters allow recognition of people walking from different views with a mean recognition rate of 92.2% and confirm that gait can be effectively used for subjects’ identification in a multi-camera surveillance scenario.

Use of multiple difference-of-Gaussian filters to verify geometric models

Experiments are reported with a program which recognizes London buses in busy street scenes. The program uses a 3D model of a bus. together with knowledge of camera and scene parameters, to compute the visual appearance of possible target events. In earlier work this took the form of 2D templates, which identify locations within the image where abrupt discontinuities of grey-value are expected. Each template corresponds to an hypothesis which is verified by measuring the agreement between the predicted features and the response of a Sobel filter to the image data. This paper reports an extension to the program which offers improved selectivity, and a more general-purpose method of linking predicted features to detected imageattributes. Multiple difference-of-Gaussian filters perform an initial object-independent analysis of the image to provide an intermediate domain in which object-dependent features, predicted by hypothesized instances of the model, are tested.

Flexible Transparency Technique

The 2 x 2 transparency has long been recognized as an indispensable teaching aid to the science teacher in presenting new material. Now with this flexible transparency technique the slide takes on a more specialized meaning. With the camera at his side the alert teacher can focus in on his students at work and within an hour, if desired, the picture can be used for testing and review. When one remembers the time it takes to set up lab quizzes, with the confusion of moving pins and dried organs, the ease of projecting the previously snapped transparency is greatly appreciated. The science curriculum is much more flexible when plants plentiful in spring can be studied in the fall, and lab experiments performed in October can be reviewed in May before the yearly finals. If the flexible transparency technique could only be used in testing and reviewing, camera knowledge and its use in these directions would be well worth the effort; but there are many other exciting possibilities. Pictures in magazines and books that cannot be shown to a class without the use of a heavy opaque projector can easily be copied. (Be sure to check with the publisher for permission.) This practice enables the teacher to study with more interest, animals and plants that the student would not see naturally. Microscopic pictures can be flashed on the screen

Nature Photography 1

THE object of Mr. Bedford's book is to encourage the pursuit of photography among those who cannot afford either the time or expense to undertake very advanced work in this direction. The author rightly points out that there are great advantages in this method of studying over the older method of collecting, and that the study of natural history by means of photography may be taken up by those whose time and means are strictly limited. The first part of the book deals with the apparatus required. A detailed description is left to text-books on photography; some knowledge of cameras and photographic methods is assumed, and the author confines himself to suggestions and to an account of the particular kinds of apparatus which he himself has found serviceable. On the whole, this part of the book should be valuable to a beginner taking up the subject for the first time, but one feels that in some parts space is wasted in describing processes of which a sufficient account is given in every book on photography, and other parts might with advantage be made more full, for in places the reader is left with no clear idea of the nature of the instrument or process recommended. Rough estimates of cost might also have been included; several times we are told that the choice must be decided by the possible outlay, but no actual estimates of expense are given.