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Comparison:
Main advantage of using this cane is expected to cost about one-half as much as a dog guide.
Portable devices are etas.
Wearable assistive aid for visually impaired
Abstract
This review is not meant as an exhaustive list, but focuses instead on providing a brief historical context of each technology while emphasizing those devices that are commercially available or part of an active research program.
1 INTRODUCTION:
The functional limitation or the severe reduction in the vision of the eye which cannot be corrected by regular means like standard glasses or contact lenses is what we refer as visual impairment. Visual impairment among people has grown in numbers through years and has touched every existing age group. The statistics of WHO suggest that the visual disability has not restricted itself to elderly population but those below the age of 15 years are equally prone to visual obstructions. The estimated number of people who are visually impaired in the world is 285 million, of which 39 million are blind and 246 million are having low visions(). The commonest causes include diabetic retinopathy, age related macular degeneration, formation of cataracts and raised pressure within the eyes leading to glaucoma ().
For humans, safe and efficient navigation requires knowledge of environment layout, path planning ,obstacle avoidance and determining one’s position and orientation with respect to world. Area of interest, for the sake of those with disability of vision, which is gaining popularity includes devices that provide hands-free interaction , or at least minimizing the use of hands when using the device. Mobility and independent navigation are the main constraints faced by visually challenged people . Mobility means possibility of liberal moving ,without support of any supplementary person, at home and unfamiliar scenarios.
2. Non Technical aids:
The time when this area was not touched by the technological revolution followed practices like white canes and Guide dogs. White cane is one of the earliest and successful and widely used travel aid for the blind. White cane, a purely mechanical device, is used to detect obstacles on the ground, uneven surfaces, holes, steps, and other hazards. Being the most successful, it is not the safest as it is not suited for detecting potentially dangerous obstacles at head level and the users must be trained in its use for more than 100 hours, since the user should have the ability to scan unfamiliar areas ahead of him or her(). Guide dogs are very intelligent guides for the blind, but they require extensive training, and they are only useful for about five years. Furthermore many visually impaired people are elderly and find it difficult to care appropriately for another living being.
3. ETA
An Electronic Travel Aid (ETA), as the name suggests, arrived with the purpose of helping the ones in need by using the wonders of electronics. Existing ETAs can detect objects in the range of up to 15 feet away from the user and require continuous scanning of the environment in the desired direction (with the exception of the Binaural Sonic Aid and the Path sounder, which depend on head or torso movements)(). Obstacle detection technologies which make use of cheap and affordable sensors are contributing as fair-to-use products. One can use a wide range of available sensors to implement an obstacle detecting circuit and they may include infrared, ultrasonic, bump, Mowat sensors and many more. Using ETAs based on these objects are not much costly but they are generally limited to providing low-resolution information about the nearby environment and are prone to errors in unfavorable condition. Another class of devices attempts to convey more detailed environmental information over a wider range of distances. These ETAs are called environmental imagers as they serve as vision substitution devices. They use the concept of critical image processing and is a popular area of research. Having said about the techniques following few lines give some brief description about the existing ETAs.
3.1 Sonic Torch
It is the first commercial available electronic aid for blind and visually impaired people. It is basically hand held device and uses the concept of ultrasonic echolocation for detection of obstacles and result in producing a sound that user can navigate by. It follows the principle of transmitting the ultrasound in forward direction and receiving reflected sound beam from the nearest object(s). 5,6
3.2 Mowat Sensor
The Mowat Sensor is an example of a pocket-sized device containing an ultrasonic air sonar system. It detects nearby object by sending high frequency ultrasound and also receiving the reflected beam. When it detects an obstacle, the device vibrates, thereby signaling the user .In this sensor the frequency of the vibrations is inversely proportional to the distance between the sensor and the object.
3.3 Sonic Pathfinder
It is a head mounted device which is based on the principle of pulse echo system controlled by a microphone. It detects an object by receiving the ultrasound that is transmitted by the head mounted device. An audio signal of varying notes is produced and a familiar tonal progression is achieved as the user approaches an object. The tones are fed to the user through the earphones and hence, he is able to guess an object in front of him
(paper=Discrete Distance and Water Pit Indicator using AVR ATmega8 in Electronic Travel Aid for Blind)
3.4 C5 Laser Cane
This device is the best known ETA which is based on optical triangulation. Optical triangulation is a method of measuring distance to object without touching them with an accuracy from a few microns to a few millimeters, over a range of a few millimeters to tens of meters. The device has three transmitters and three photodiodes as receivers. An “up” channel detects obstacles at head-height, and a “forward” channel detects obstacles from the tip of the cane (in the range of 1.5-3.5m) , and a “down” channel detects drop-offs in front of the user.
3.5 Path sounder
Russell Pathsounder is an ultrasonic travel aid with two ultrasonic transducers mounted on a board that user wears around the neck , at chest height. Although , the device do not require manual scanning, their effective coverage of the surroundings depends on the orientation of head and torso.
3.6 Binaural Sonic Aid
Also known as sonic guide, the device comes in the form of a pair of spectacle frames, with one ultrasonic wide-beam transmitter mounted between the spectacle lenses and one receiver on each side of the transmitter. Signals from the receivers are shifted and fed separately to the left and the right ear. The technology is primarily based on physical acoustics, psychoacoustics, and auditory neurophysiology ().
3 Disadvantages of present devices
Sonic torch produce a sound by which user can navigate but it can interfere user sense of hearing at very crowded places it is not working there.
Head mounted device like sonic pathfinder has problem to keep head of user totally erect. On the other hand produces audio signal of different frequencies but not designed to detect any hanging object
High tech aids
Researchers from the Center for Research and Advanced Studies (CINVESTAV) in Mexico have developed a pair of glasses that use a combination of ultrasound, GPS, stereoscopic vision and artificial intelligence to help the visually impaired to navigate their environment.
Over the past years several devices for visually impaired are made ranging from wrist-mounted sonars to guide vests with helmet mounted cameras. A s today electronics become smaller in size, faster and take v. less power these devices can provide better guidance to their users, while becoming less intrusive and more affordable.
Most advanced system in this field is the device consists of a pair of glasses with two cameras mounted on the frame, for effective stereoscopic vision. The glasses work in tandem with a tablet device that processes the data and then provides audible directions to the user.
The ultrasound technology embedded in the glasses can detect nearby static and moving objects, including translucent objects like glass. The device can also use AI to recognize locations, read signs, and identify objects such as various banknote denominations and color of clothing. Finally, included GPS can provide audible directions.
Comparison with the existing systems:
Another option that provides the best travel aid for the visually impaired people is the guide dogs. Based on the symbiosis between the disabled owner and his dog, the training and the relationship to the animal are the keys to success. The dog is able to detect and analyze complex situations: cross walks, stairs, potential danger, know paths and more. Most of the information is pass through tactile feedback by the handle fixed on the animal. The user is able to feel the attitude of his dog, analyze the situation and also give him appropriate orders. But guide dogs are still far from being affordable, around the price of a nice car, and their average working time is limited,
Approach:
Low Tech aids
Eta
High tech aids: indoor outdoor systems-hybrid aids
Gadgets
References
FACTORS AFFECTING VISUALLY IMPAIRED NAVIGATION
Biggest challenges to independence for visually impaired individuals are difficulties in accessing printed materials and the stressors associated with safe and efficient navigation . Access to printed documents has been greatly improved by the development and proliferation of adaptive technologies such as screen-reading programs, optical character recognition software, text-to-speech engines, and electronic Braille displays. Braille was first developed in the late 1820's by a young Frenchman named Louis Braille. He created Braille by modifying a system of night writing which was intended for military use.Braille is a system consists of reading and writing by touch used by the visually challenged. It consists of arrangements of dots which make up letters of the alphabet, numbers, and punctuation marks. The basic Braille symbol, called the Braille cell, consists of six dots arranged in the formation of a rectangle, three dots high and two across. Other symbols consist of only some of these six dots. In Braille 1 is number sign a; 2 is number sign b; 10 is number sign a-j and 193 is number sign a-i-c. These signs must be memorized, but most Braille readers and writers find them convenient, rather than a problem. Braille is written on heavy paper, and the raised dots prevent the pages from lying smoothly together as they would in a print book. Therefore, Braille books are quite bulky.
Writing Braille with a slate and stylus compares to writing print with a pen or pencil. The stylus is used to push dots down through the paper, while the slate serves as a guide. The Braille slate can be made of metal or plastic and is hinged so that there is a guide under the paper as well as on top of it. A person writing Braille with the slate and stylus begins at the right side of the paper and ends the line on the left, since the dots are being produced on the underside of the paper. Of course, the Braille reader reads from left to right, for the dots are then on the top side of the paper. Although this may seem a bit confusing, it need not be at all troublesome, since both reading and writing progress through words and sentences from beginning to end in the same manner. The speed of writing Braille with the slate and stylus is about the same as the speed of writing print with pen or pencil.
Today there are three methods of writing Braille, just as there are two methods of writing print. A Braille writing machine (comparable to a typewriter) has a keyboard of only six keys and a space bar, instead of one key for each letter of the alphabet. These keys can be pushed separately or altogether. If they are all pushed at the same time, they will cause six dots to be raised on the paper in the formation of a Braille cell. Pushing various combinations of the keys on the Braille writer produces different letters of the alphabet and other Braille symbols .
By contrast, difficulty accessing room numbers, street signs, store names, bus numbers, maps, and other printed information related to navigation remains a major challenge for visually impaired people travel. Imagine trying to find room n257 in a large university building without being able to read the room numbers or access the “you are here” map at the building’s entrance. Use of Braille signage certainly helps in identifying a room. In addition, only a modest fraction of the more than 3 million visually impaired people in the United States read Braille signs. Braille signs indicating room numbers are installed by law in all newly constructed, or renovated, commercial buildings . However, many older buildings do not have accessible signage, and even if they do, room numbers represent only a small portion of useful printed information in the environment. For instance, a visually impaired navigator walking into a mall is unable to access the directory of stores or in an airport the electronic displays of departure and arrival times. When traveling without vision in an unfamiliar outdoor setting, accessing the names of the shops being passed, the name of the street being crossed, or the state of the traffic signal at a busy intersection can also be challenging. Although speech-enabled GPS-based systems can be used to obtain access to street names and nearby stores and audible traffic signals can provide cues about when it is safe to cross the street, these technologies are not widely available to visually impaired navigators. Where an environment can be made accessible for somebody in a wheelchair by removing physical barriers, such as installing a ramp, there is no simple solution for providing access to environmental information for a visually impaired people traveler . As our interest is in visually impaired navigation and environmental access, most of the navigational technologies discussed in this chapter collect and display environmental information rather than require structural modifications. Limitation with these these are not used in parking and traffic zones.
INDOOR LOCALIZATION AIDS FOR THE VISUALLY IMPAIRED
Magnetic maps By developing magnetic maps of buildings can educate the general public, employees, and even maintenance workers about the levels of magnetic flux in the surroundings. Once understood, these maps can help in development of a building by providing a set structure or layout.
The number of landmarks and their separating distances can then be implemented throughout the building to provide easy analysis when integrating the building with indoor navigation. Magnetic fields in general are caused by electrical Utilizing the magnetic field information inside buildings for localization and navigation purposes is an interesting aspect to be studied. Some work has been done for indoor robot localization using magnetic fields. However, this kind of information has not been exploited in the design of an indoor navigation system for humans. Some work has been done on navigating the visually
impaired, an area in which our techniques can be applied also help with indoor navigation for the visually impaired by applying an accelerometer to measure distance and a gyroscope and a magnetometer to approximate the direction. With today’s mobile phones enriched with accelerometers,
cameras, magnetometers, and microphone sensors, numerous applications are feasible. This system targets on un tapping the magnetic field information for localization and navigational purposes. We present a novel mobile phone-based magnetic field data collection technique that aids in finding landmarks and guideposts and distinguishing rooms and corridors inside a building using their magnetic profiles. The only infra structure in this system is a mobile phone, the availability and convenience
factor of which overwhelms that of utilizing external sensors. This method involves collecting and analyzing extensive measurements of the magnetic fields at numerous places inside buildings using the built-in magnetometer.
We develop magnetic maps using data collected. The daily walking patterns of people were imitated, such as walking through a building entrance, down the hall and into a classroom, or entering into a laboratory and walking to a station. These patterns can help us focus on parts of the building that are heavily traveled for location identification.
GPS BASED DEVICES
The first accessible GPS-based navigation system developed by Jack Loomis and his colleagues at the University of California, Santa Barbara, was initially envisaged in 1985 and became operational by 1993.
The global positioning system (GPS) is a network of 24 satellites, maintained by the US military forces, that provides information about a person’s location almost anywhere in the world when navigating outdoors. GPS-based navigation systems are a true orientation aid, as the satellites provide constantly updated position information whether or not the pedestrian is moving. When in motion, the software uses the sequence of GPS signals to also provide heading information. Because of the relatively low precision of the GPS signal, providing positional information on the order of one to 10 m accuracy, these devices are meant to be used in conjunction with a mobility aid such as a white cane or a guide dog.
This personal guidance system (PGS) employs GPS tracking and a GIS database and has been investigated using several output modalities, including a haptic interface using a handheld vibratory device, synthetic speech descriptions using spatial language, and a virtual acoustic display using spatialized sound (see the PGS Website for more information [49]). The use of spatialized sound is especially novel, as it allows a user to hear the distance and direction of object locations in 3D space. Thus, the names of objects are heard as if coming from their physical location in the environment. Use of this system has proved effective in guiding people along routes and finding landmarks in campus and neighborhood environments [50–52].
Although there are many commercially available GPS-based devices employing visual displays (and some that even provide coarse speech output for in-car route navigation), these are not fully accessible to blind navigators. The first commercially available accessible GPS-based system was GPS-Talk, developed by Mike May and Sendero Group in 2000. This system ran on a laptop computer and incorporated a GPS receiver and a GIS database that included maps of most US addresses and street names. It was designed with a talking user interface that constantly updated the wayfinder’s position and gave real-time verbal descriptions of the streets, landmarks, or route
information at their current location. A strength of this system was that it was highly customizable; for instance, verbal directions could be presented in terms of right left, front back, clock face, compass, or 360◦ headings. A person could get information about the length of each block, the heading and distance to a defined waypoint or destination, predefined and programmable points of interest, or a description of each intersection. There was also a route-planning facility that allowed creation of routes from a current position to any other known position on the map. Another advantage of this system was that it could be used in virtual mode, such as using the keyboard to simulate navigation of the digital map. This allowed a person to learn and explore an environment prior to physically going there. Research on a similar European GPS initiative, MoBIC, demonstrated the benefits of this pre-journey planning for blind wayfinders [53].
Sendero’s most current version, the BrailleNote GPS, works on the popular BrailleNote accessible PDA and is now one of three commercially available GPS-based navigation systems for the blind (see Ref. 54 for a review). Many of the core features between the three systems are similar but while Sendero’s BrailleNote GPS and Freedom Scientific’s PAC Mate GPS work on specialized hardware, Trekker, distributed by Humanware, runs on a modified mass-market PDA. Trekker is a Braille input and speech output device, where the other two systems have configurations for Braille or QWERTY keyboard input and speech or Braille output.
Whether this GPS technology is used as a pre-journey tool to explore a route or during physical navigation, the information provided is expected to greatly improve blind orientation performance and increase user confidence in promoting safe and independent travel. No other technology can provide the range of orientation information that GPS-based systems make available. As we discussed in Section 25.2, effective orientation can be particularly difficult for blind navigators. Thus, these devices have great potential to resolve the orientation problem that has been largely unmet by other navigational technologies.
The other major shortcoming of GPS is that it does not work inside buildings.
There are several notable limitations to GPS-based navigation systems. First, although the accessible software may not be very expensive, the underlying adaptive hardware on which it runs can be quite costly (e.g., up to $6000). The user must also periodically buy new maps and databases of commercial points of interest, as these change with some regularity.
In addition, GPS accuracy is not currently sufficient for precise localization unless the user has additional differential correction hardware, which is expensive and bulky. GPS technology is also unable to tell a user about the presence of drop-offs, obstacles, or moving objects in the environment, such as cars or other pedestrians. Thus, these systems are not a substitute for good mobility training. The base maps are also often incorrect, such that a street name may be wrong or the system may try to route the navigator down a nonexistent road or even worse, along a freeway or thoroughfare that is that is dangerous to pedestrian travel. As GPS signals are LOS, the signals are often disrupted when the user is navigating under dense foliage or between tall buildings and indoor usage is not possible. As orientation information is as important inside as it is out, this lack of coverage can be a significant challenge to blind wayfinders (see text below
RFID TAG TECHNOLOGY
This is another method for navigation for visually challenged people. we present an RFID based information grid system with a reader integrated into the user’s shoe ,which is connected to the user PDA or cell phone via a Bluetooth. Major advantage of this technology that people can navigate inward as well as outward.
INDOOR NAVIGATION AS UNDER: The low cost nature of passive RFID tags and the characteristics shows promise to meet our design criteria. A single Passive RFID tag represents a single grid point in the system .Carpet manufactures could integrate the RFID tags as part of the weaving process or the RF ID tags could be integrated into a thin layer material that is applied under the carpet or hard surface flooring. For rooms that have existing carpeting the floor could be easily upgraded by rolling up the carpet applying the RFID flooring material and then reinstalling the existing carpet (Figure 1-a). For tile floor that represent a larger cost to replace it may be possible to insert RFID tags by removing the grout at tile intersection points and then reapplying the grout. Hardwood floors represent a larger installation challenge because of the inability to do an installation without impacting the visible surface.
DIFFERENT GADGETS USING DIFFERENT SCINERIO by me
Different wearable and portable assistive technologies are used by visually impaired to support their lives. Main benefit by using these wearable devices to get very less usage of hand when device is wore by physically challenged people.
. A wearable obstacle avoidance electronics device designed to serve the navigation system of visually impaired person. Another system there is implementation of the voice-“seeing with sound” this system is designed with help of glasses with attached camera, portable computer and ear speakers. Main focus of system is to give importance to some features like free hands, free ears and easy to operate the system.
An indoor navigation system for visually impaired people is RFID unit .This system constantly tracks the user through an RFID unit and communicate the user to obtain desired destination safely via wireless connection and through a tactile compass “Blind audio Guidance system” is based on embedded
system, uses ultrasonic sensor for distance measurement, IR sensor for object detection and AVR sound system for audio instructions. The main functions of this system are environment recognition and path detection
Another system using the ultrasonic sensor based navigation for visually challenged people. Ultrasonic sensors receive visual information and this visual
information is transformed into auditory information This system based on microcontroller with synthetic speech output and portable device to guide the user about urban walking paths to point out what decisions to make. This device uses the principle of reflection of high frequency ultrasonic beam to detect obstacles in the path. By using vibro –tactile form in order to reduce navigation difficulties . ultrasonic sensor uses the reflection principle it will not helpful during occurrence of wall in the way which result in inefficient localization. Vibration and voice operated navigation system developedusing ultrasonic sensors to detect obstacles. Since visually impaired people are more sensitive in hearing and possesses strong perception than ordinary people. So this system gives alert through vibration and voiceSystem works in indoor as well as outdoor navigation and focus on continuously sensing surround obstacles andalerting through vibration and voice feedback.Another navigation system named as RGB-D sensor with range expansion used by visually challenged people System uses aconsumer RGB-D camera for range and visualinformation, which support range based floor
segmentation. Main advantage of using it that cheaper RGB sensor supports in object detection and color sensing. User interface is given through audio instructions and sound map information