A Portable Device for Optical Recognition of Braille Iain Murray Curtin University of Technology

Introduction Purpose of the device A brief introduction to the Braille system Scanner operation The Prototype Image capture & processing Proposed improvements Conclusion

Why? Primarily for non Braille users –Education –Workplace Reproduction of worn or old Braille Electronic storage of Braille texts

The Braille System Tactile medium consisting of 6 dots Context sensitive –people = p –wh = : or which or : (colon) –Includes many rules for use Similar to shorthand May be printed both sides - interpoint

Scanner Operation Hand held portable unit Camera assembly is moved over the Braille line Operates in real time Results of the scan are displayed on the host computer

The Prototype Block Diagram

Image Capture

The Lens

CCD Operation 10ms integration time Pixels clocked out in 2.6ms 100 µs per sample Allows 7ms per slice processing time –(context switching and overheads considered)

CCD Operation SI pulses at 10ms intervals Pixels clocked out at 50KHz

Linear Motion Detection Slotted disk and IR detector/emitter Gear system to produce pulses at 200DPI Each pulse sends an interrupt to the DSP

Linear Motion Detection Codewheel Gears Illumination Array Lens Housing Selfoc Lens Array

Prototype Development Platform TMS320C50 DSP by Texas Instruments –Low cost –10K words of data/program memory –Incorporates Analog Interface Circuit (AIC) TLC32040 Programmable Include anti-aliasing bandpass filter –Emulates serial (RS232) communications

Captured Image

Cell Element Detection Are dots present? 25 samples at 100u second intervals Reference levels are averaged Samples are compared to reference level Results are written to scan word

Cell Compilation Scan words are captured at 200 dots/inch Stored as a single word, position oriented –10 = bright –01 = shadow –00 = reference level –11 = status dots are 1mm diameter => 8 scans per dot

Cell Compilation 50 samples kept (scan word) in the image buffer. Cells assembled from this image –Image buffer is compared to each possible ideal cell (63 combinations)

Cell Compilation When a cell is matched: –Send binary Braille code Determined from a lookup table –Clear the image buffer –Host processor expands grade 2 code Text is now available for display or storage

Grade 2 Decomposition Algorithm by Paul Blenkhorn A simple state machine Allows for exceptions Uses look up tables and therefore allows : –Foreign language support –Special purpose codes e.g. Music Math Implemented in C

Proposed Improvements Quadrature motion detector will allow: –Reversal of scan direction –Decreased resolution Implement Fuzzy dot detection Use the SI pulse for triggering illumination Improve ergonomics

Conclusion Achieved –Image capture of a tactile medium –Dot recognition (position) –Grade 2 Braille decode –OCR of embossed Braille

Conclusion (continued) Further development should yield a useful device that overcomes the communication barrier between Braille users and the mainstream community.

The Prototype (and the development environment)