BACKGROUND

Refreshable Braille displays are used by people with visual impairments to access information on a computer in real-time.  Refreshable Braille displays consist of a row of Braille cells with movable pins that raise and lower to represent the characters being displayed in each cell.  Currently, except for a few products in final development, refreshable Braille displays are only able to display a single line of Braille consisting of 20 – 80 Braille characters, 80 characters being the average number across a word processing screen. This small amount of information results in extreme difficulty in scanning large documents and the inability to display tables, graphs or graphics. Added to the limited output is the high cost of these devices (1).
 
Because of these shortcomings, people with visual impairments, especially people in America where assistive technology is usually not government subsidized, often use voice synthesis devices as their main mode of access to computer data. While voice synthesis does allow access to information that may not be available in print, such as web pages, it does not allow documents to be easily edited or reviewed.  People who are hearing impaired also cannot use voice synthesis.  Therefore, this technology does not always meet the requirements of existing disability laws because it does not allow equal access to materials needed for equal education and employment.  Refreshable Braille displays should be made attainable to a broader range of people with visual impairments; however, this action will not occur until the displays cost less with increased function.  This can only happen if new technology that is outlined later in this paper is further funded. Increased funding will make the development of multi-line or even full-page refreshable Braille displays possible (2). 

PRACTICE REPORT OBJECTIVE

The objective of this paper is to report the latest technological developments in multiple line refreshable Braille displays.

CURRENT TECHNOLOGY IN USE

Various features have influenced the design and development of refreshable Braille devices.  The technical aspects of size, weight, power, reliability and cost are critical to the manufacturers while the secondary characteristics of speed, navigation, compatability with software, usability, and noise drive consumer choice.  The result of these desired features is that current refreshable Braille devices are: portable; lightweight; battery powered; have multiple cursor controls and indicators; somewhat resistant to dust and finger grime; refresh at a quick rate, and quiet.  Cost is still an issue as current technology leads to an average production cost of $25 - $30 a cell, resulting in units in price from $1200 for the most basic units to $10,000 plus for the most advanced (2). Current manufacturers include Alva Access Group, American Thermoform corporation, Brailletec, Freedom Scientific, HumanWare Group, Pulse Data and Sighted Electronics (3). 

The products available to the public today all use the same basic technology in that the device is fabricated of one row of “soft” cells made up of 6-to-8 metal or nylon pins. These pins are controlled electronically to raise or lower as the characters appear on the display of a computer or Braille notetaker. The pins are either solenoids or piezoelectric outputs. The display can also have router controls to position the cursor over the desired letter of the text.  Each one of these pins is controlled by a macroscopic actuator; therefore, a 40-cell, 8-dot unit requires 3200 actuators. This leads to a very complex device subject to power and reliability problems (1).

Solenoid electromagnetic technology was very popular in the 1980s and 1990s.  One problem with solenoid technology is that it is power intensive.  Locking mechanisms are required so all of the actuators do not continuously receive power as this would overload an average home’s circuitry, let alone a portable battery. Locking mechanisms can be used to insure the dots maintain a uniform height; however, these mechanisms also lead to an increased number of components in the machine and, thus, increased fallibility.  Solenoids are also prone to failure from dirt and use, increasing reliability issues. If a full page Braille display is developed using this technology, 6000 solenoids would have to be regularly cleaned and maintained.  Decreased reliability can greatly affect comprehension in Braille, especially grade II Braille because of the multiple uses of same dot combinations. A reliability rate of 99% for every dot on a one-line, 80-cell display with 480 dots will have no errors only once in 125 displays (2).  

Displays that use piezoelectric bimorph pins prevail in today’s market. Metec in Germany and KGS of Japan are the major suppliers of this technology (4). Five features contribute to this dominance.  First, the power requirement is low enough that all dots can be raised simultaneously, thus eliminating the need for locking mechanisms and allowing the devices to be run by portable battery.  Second, the devices are much less susceptible to dirt and wear because they have few moving parts, just the bender and the shaft. In addition, there is no friction because of locking.  Also, because they do not require the locking mechanisms, the devices can quickly refresh. Next, this technology is quiet so it does not disturb office or schoolmates.  Lastly, because there are few parts, the dots can be closely packed so they resemble standard paper Braille (2).

One might ask why this technology is not sufficient for future as well as current use?  Cost is the answer.  At $25 per dot, a full-page refreshable Braille display would cost in the range of $100,000. 

CURRENT TECHNOLOGY IN DEVELOPMENT

In order to increase the ability to read information directly from the computer and interpret graphics, individuals with visual impairments have expressed much interest in the development of multi-line and full-page refreshable Braille displays. As of this date, no company is currently manufacturing a refreshable Braille display that contains more than one line; however, many organizations are in the development phase. The information below outlines what products are currently being developed and each product’s features based on what manufacturers and consumers have deemed important for optimal function.

National Federation of the Blind (NFP)

The National Federation of the Blind (NFB), funded by the National Institute of Standards and Technology (NIST), has developed a prototype for a refreshable Braille device that uses rotating wheel technology to reduce the number of actuators needed for a single-line, 80-character display to 3-to-4 actuators. If successful this will reduce cost by a factor of 10 and improve reliability of the displays because the number of parts needed will be greatly reduced (5).

IACTIV

Orbital Research, Inc. has licensed its refreshable Braille display technology to IACTIV corp. They have developed a refreshable Braille display with full-page capability and a flexible surface using Micro-Electro-Mechanical Systems (MEMS) technology for their actuators. According to Orbital research, this display consists of:

In one embodiment, the present invention is a refreshable Braille display system or a module from such a system comprising a) a plurality of microelectromechanical valves having a top surface and a bottom surface, each microelectromechancial valves having an opening or positioned in line with an opening, each of which represents a Braille dot and each opening arranged in a pattern of Braille cells with the Braille cells forming a Braille display; and b) an elastomeric polymer having a upper and a lower surface, the lower surface of the elastomeric polymer being sealed about each openings which represent the Braille dots; wherein during operation of the display system the upper surface of the elastomeric polymer forms a plurality of Braille dots which are extended and retracted based upon the operation of each of the electromechanical valves (6).

This display will reduce the cost of the system as well as improve reliability and can also be used with graphics displays (D.Shaw, personal communication, November, 8, 2007)).

North Carolina State University

Peichun Yang is a Post Doctoral Fellow at North Carolina State University who is working along with Dr. Franzon on the development of multiline and full page refreshalble Braille displays based on PVDF polymer technology.  His project is supported through a NIDRR through a grant "Field Initiated Projects" in the Department of Education.  The following is the abstract of the project:

This project develops a low-cost, portable Braille display utilizing polyvinylidene floride (PVDF), an electro-active polymer, to create a novel, low-power, low-voltage bistable actuator. The dots in this display are produced with more force and easier to read. By using PVDF and silicon micromachining techniques, there is the potential for each Braille cell to cost $5 or less. This display should use less power, be cheaper to make, require a lower actuation voltage (thus reducing the size and cost of the control electronics), and be easier to scale to more letters than other current prototypes. The key technology of the project is the mechanism of Bistable Latching and Mechanical Amplification, which enables the fabrication of the actuator that can provide large displacement (0.5 mm), large supporting force for Braille dot(over 20 grams), and very short response times (20ms) simultaneously. Meanwhile, the Braille cell is very compact and has low power consumption. (P. Yang, personal communication, November 15, 2007).

Smart Technology Ltd.

Smart Technology Limited, a United Kingdom based company that manufacturers and develops Electrorheological (ER) fluids and electronics for ER fluid control, has been involved in an EC funded project to develop a full-page refreshable Braille display. ER fluids thicken when an electric field is applied to them, allowing hydraulic actuators to be constructed. These actuators replace the traditional piezoelectric technology. This transition is very quick and employs less power than piezoelectric actuators and is also reported to be cost efficient (7).

Tactile Display Corporation

Tactile Display Corporation (TDC) is currently developing a multiple line refreshable Braille display that will eventually emerge into a full-page display.  TDC states that it will introduce “three innovations that will simplify the manufacture and repair of Braille cells and refreshable Braille display products based on them.” They do this by proposing to: replace the current pin with a segmented compressible pin; replace individual actuators with a single sweep bar that moves under the cells, and, replace the design of displays from individual Braille cells to Braille dot modules.  These innovations will reduce the amount of components needed in the construction of the display, increase the reliability of the refresh cycle, make repair much easier, and, greatly reduce the cost of the device. The anticipated cost per Braille pin is expected to be approximately 20-to-25 cents. This is made possible because the multiple pin actuators formerly needed are replaced by a single actuator, a scan bar that resets entire rows of pins at a time (P. Durant, personal communication, December 2, 2007.). 

DISCUSSION

Only 30% of the working age population with severe visual impairment is currently employed in the United States.  Inadequate technology is a large reason for this small rate of employment. Only 3% of the population that is deemed functionally blind or less use refreshable Braille displays. One reason for this is the displays do not allow sufficient access to information accessible by computer.  A larger reason is the cost of the devices.  Five organizations are currently addressing these issues of ample display area and price through various modes of technology.  Grants and funding resources must be made available to these organizations.  While initial outlay costs may seem high, the end products will result not only in the benefit of those in need, people with visual impairments, but also in increased employment opportunities for these people. A higher employment rate will eventually reduce the need for public assistance funded by taxpayers. Finally, without these innovations, the blind community will continue to lack adequate technology that was deemed mandatory under existing disability law.