BODY MOUNTED VISION SYSTEM FOR VISUALLY IMPAIRED OUTDOOR AND

Abstract: The most challenging issue of the navigation assistive systems for the visually impaired is the instantaneous and accurate spatial localization of the user. Most of the previous proposed systems based on GPS sensors have clearly insufficient accu

Conference & Workshop on Assistive Technologies for People with Vision & Hearing Impairments

Assistive Technology for All Ages

CVHI 2007, M.A. Hersh (ed.)

BODY MOUNTED VISION SYSTEM FOR VISUALLY IMPAIRED

OUTDOOR AND INDOOR WAYFINDING ASSISTANCE

Sylvie Treuillet, Eric Royer, Thierry Chateau, Michel Dhome, Jean-Marc Lavest

LASMEA – UMR 6602

Campus des Cézeaux, 63177 Aubière, France

Phone: 33 473 407 764, Email: Sylvie.treuillet@univ-bpclermont.fr

Abstract: The most challenging issue of the navigation assistive systems for the visually impaired is the instantaneous and accurate spatial localization of the user. Most of the previous proposed systems based on GPS sensors have clearly insufficient accuracy for pedestrian use and are confined to outdoor with severe failing in urban area. This paper presents an interesting alternative localization algorithm using a body mounted single camera. Instantaneous accurate localization and heading estimates of the person are computed from images as the trip progresses along a memorised path. A first portable prototype has been tested for outdoor as well as indoor pedestrian trips. Experimental results demonstrate the effectiveness of the vision based localization to keep the walker in a navigation corridor less than one meter width along the intended path. Future works will investigate multimodal adaptative interface taking account the psychological and ergonomic factors for the blind end-user to design a suitable guiding solution for the blind and visually impaired.

Keywords: personal localisation and heading system, navigation assistance, blind people

1. Introduction

A major political and technical challenge for a modern society is to find innovating solutions for an effective assistance to increase the security and mobility of the visually impaired persons travelling through city streets and buildings. For people who are blind, way finding is dependent on the ability to remain localized and oriented. Recent works on assistive technologies for human localization are mainly focused on GPS (Global Positioning System) [Brusnighan 1989, Makino 1997, Loomis 2001, Kowalik 2004]. But GPS sensor is indoor ineffective and fails to provide accurate spatial position in low cost version (ten meters - for the best - is clearly inadequate to keep a walker along the intented path). Furthermore, GPS suffers of masking areas especially as the blind inpidual moves while travelling along the walls. Some works have tested differential GPS which allows around one meter accuracy

[Helal 2001, Balachandran 2003], but it is a costly and cumbersome equipment which needs fixed ground stations and is only outdoor efficient. Alternative devices have also been designed for indoor human localization such as ultrasound [Ran 2004] or radio frequency identification transponder [Na, 2006], using robotic “dog-guide” [Kulyulin 2004] or instrumented white cane [Hesch 2007]. To sum up, the localization systems with sufficient accuracy for pedestrian application at this time are based on ground installation (DGPS), and Drishti [Ran 2004] is the only system which proposes a combined outdoor/indoor system. To trust in a large spread, the design of an inpidual localization system will be based on wearable, low cost and mobile technologies, free from collective equipment. In this way, we propose a new vision based solution derived from autonomous navigation of wheeled robot [Royer 2005] to assist visually impaired in their everyday travelling outdoor as well as indoor. This computer vision based system requires no environment instrumentation: instantaneous accurate localization and heading estimates of the user are computed only from images provided by a body mounted camera as

Abstract: The most challenging issue of the navigation assistive systems for the visually impaired is the instantaneous and accurate spatial localization of the user. Most of the previous proposed systems based on GPS sensors have clearly insufficient accu

the trip progresses along a memorized path. This real time localization is available provided that a video sequence has been previously recorded during a learning trip. For the time being, the vision system is only used to localize and guide the walker along the intended path, it does not substitute for the long white cane in obstacle avoidance. The following section describes our vision based positioning system. Some experimental results with a first wearable prototype are given in section 3. The conclusion and future works are discussed in the last section.

2. Vision Based Positioning

The localization system relies on two steps (Figure 1): a preliminary learning path and a real time localization for navigation assistance. During a learning trip, a video sequence is recorded by the on-board vision system and processed off-line to automatically build a large set of natural landmarks by applying structure from motion algorithm. This algorithm permits to jointly recover the motion of the camera and the geometry of a rigid surrounding scene by automatically recognizing some singular points through the image sequence (angular points on buildings, windows, doors, billboard, trees,…). The recorded reference consists in a set of selected key images corresponding to different camera positions along the learning path and a 3D map of the environnement. During navigation assistance, ego motion of the camera is computed as the trip progresses by matching the stored 3D landmarks with their projections e …… 此处隐藏：14983字，全部文档内容请下载后查看。喜欢就下载吧 ……