1. Field of the Invention
This invention relates to a tracking aid for hand held optical scanners, and more particularly to a tracking aid for hand held optical scanners used for input to a character recognizing and voice synthesizing reading machine to enable manual scanning by the blind or by the print handicapped for the purpose of converting substantially any printed text into synthesized human voice.
2. Description of the Prior Art
An existing reading machine for the blind requires that the visually impaired person take the printed material, such as a book, to a reading machine and place it opened face down on a fixed platen, one page at a time, so that the printed text thereon may be scanned, converted into video or digitized data, converted to ascii representation, and then converted to sound by a voice synthesizing system. The user must lift a bound volume or printed material after each page has been scanned, the page must be turned, and the next page in the bound volume realigned on the platen. Such manipulation of bound volumes of printed material is cumbersome for a visually impaired person, and the task of scanning the pages would be simpler if the bound volume could remain stationary and only the pages turned after they were scanned by a small, compact hand held scanner.
Copending U.S. application Ser. No. 104,741, filed Oct. 5, 1987, to Sussman et al., entitled "Hand Held Optical Scanner for Omni-Font Character Recognition" discloses a small hand held scanner connected by a flexible cable to a portable character recognizer and voice synthesizer. This scanner contains components for scanning swaths of printed text from single sheets or bound pages of bound volumes. The components are housed in an elongated dust-tight carriage. A broad roller is rotatably mounted on one edge of the carrier and a split roller is rotatably mounted on the opposite edge. The roller axes are coplanar and parallel with each other, so that when the carriage is manually moved across the page to be scanned, a window in the carriage floor is maintained a predetermined distance therefrom and the rollers guide the carriage in a substantially straight line without need of guide rails. A strobed LED array provides the illumination for a 423 element per inch CCD array via a Selfoc.RTM. lens. A rotary encoder is belt coupled to the split roller to provide speed and scanning direction signals. Circuitry is provided for processing the CCD array output signals in accordance with the rotary encoder signals.
U.S. Pat. No. 3,918,179 to Mauch et al. discloses an apparatus for teaching the blind to scan a single document of printed matter placed on a flat surface of a transparent substrate. The printed matter is scanned with a manually moved optical probe by using a structure capable of releasably holding the upper edge of the document on the releasably held substrate while a manually applied tracking aid relesably holds another portion of the document. The tracking aid is manually adjusted after each line of printed matter is scanned. The next and succeeding lines of printed matter to be scanned requires that the tracking aid be manually repositioned.
U.S. Pat. No. 3,700,809 to Nadon discloses a tubular hand positionable cursor for taking position signals from a flat grid. The cursor includes a coil in a cylindrical recess adjacent one end thereof. Energization of the coil produces a field or flux so that inductive coupling eliminates the need for physical contact between the cursor and the grid. The cursor end containing the coil is configured so that the effects of changes in orientation of the cursor parallel to the plane of the grid are eliminated and the effects of orientation changes normal to the plane of the grid are minimized.
U.S. Pat. No. 4,518,919 to Ishida discloses a detecting device for detecting a magnetic strip embedded in a sheet, such as, for example, a currency note. The detecting device comprise a magnet and magnetic resistance element located within the magnetic field generated by the magnet. When the magnetic strip in the note passes through the magnetic field generated by the magnet, the change in field is detected by circuitry. This circuitry detects the change in resistance of the magnetic resistance element. By sensing the change in resistance of the resistance element and comparing it with a predetermined value, the existence or non-existence of the magnetic strip can be determined.
Most of the prior art hand held optical scanners for use by the blind or print handicapped provided mechanical guides for the optical scanner. Those without any tracking assistance encountered a skewing motion that impeded the conversion of printed information to ascii code for all but the most experienced user.