Legibility of digitally printed Braille

Gorazd Golob, Marica Starešinič, Bojan Rotar, Nevenka Jereb, Igor Majnarić

Abstract

Braille text is a basic means of communication for many blind and visually impaired people. Basic Braille 64 bit set-up is in use since 19th century. There are many implementations adapted to different languages, scope, media, requirements of blind and visually impaired people associations, legislation and printing process. Braille used for the pharmaceutical packaging is prescribed according to EU Directive 2004/27/EC, in other fields there are only recommendations and specifications in force.
Multilayer digital ink-jet printing allowed us to prepare samples according to different specifications, including modulation of Braille sign dimension, dot height and shape. Measurements of dot height using different image analysis methods based on microscopic images, dedicated equipment for pharmaceutical industry (Pixel-proof) and probe tip contact mechanical profilometer were. Legibility test has been carried out at the "Zavod za slepo in slabovidno mladino Ljubljana" (Centre to help blind and partially sighted persons) and with a help of other blind people of all ages and Braille skills. It is evident from the results that the successful reading of the blind is greatly dependent on the height of the dots of Braille. A survey on their answers and their comments gave us important information and directions for further research.

Keywords: Braille, legibility, blind and weak-sighted, embossing, raised printing

1 Introduction

Braille is a system strongly associated with the blind, which enables reading by touching raised dots. The system consists of a combination of six dots for every letter of the alphabet, punctuation marks and usual groups of letters (words). Being blind implies that sight is insufficient for reading and Braille gives those people literacy and equality to other people.
Taking the varying definitions of blindness into account, it is estimated that 30 million Europeans are blind or partially sighted of whom 1/8 or 3.75 million Europeans are blind. More than 1 million Americans are registered as legally blind. In the UK, there are some two million people having difficulty seeing, and around one million of these have sufficient sight problems that they could officially register as blind or partially sighted, according to the Royal National Institute of the Blind (RNIB). Somewhere between 10,000 and 20,000 of them use Braille. In Germany there are about 155 000 blind people of whom 15 to 20 % read Braille. In Croatia there are 17,665 people with visual impairments, from them 3393 people are totally blind (2011) [Škes, 2012]. There are 3995 members (2008) of Blind and Weak Sighted Association in Slovenia, however the total estimated number of people with visual impairment in Slovenia is around 10,000 [Kačič et al., 2010]. The number of Braille users is officially unknown but comparable to other countries.
EC Directive 2004/27 requires labeling and information for the partially sighted and the blind to be provided with medicinal products. The first implementation of Braille on food, drinks and pharmaceutical packaging and labels began in 1997 in Europe and USA, so it is not something very new on the market. In September 1997 Universal Braille Dots Inc. submitted a proposal to the Food and Drug Administration in the United States for Braille and large print on all drug labels in USA. We expect that all developed countries will follow the content of EU Directive in their national legislation in near future and that Braille will become widely accepted by food and beverage industry too. Dimensions of Braille printed on pharmaceutical packaging are specified in the Standard EN 15823, however for general use there are only recommendations and specifications available. Standardization process is still in progress. [EBU guidelines, 2009]
The main goal of our work was legibility testing of Braille, printed on pharmaceutical packaging according to EC Directive, and testing of Braille legibility of short text with a help of blind people who have contributed to the successfully completed work.

2 Background

a Braille, developed to its full extent in 1825 by young Frenchman Louis Braille, basically consists of a base set-up of 2 dots horizontally and 3 dots vertically. This gives a total 26 dot combinations, 64 in all. As one of the 64 combinations is all zeros - all dots not present - this is considered as the space rather than a real Braille character (Figure 1).
Dimensions:
a = 2.5 mm
b = 2.5 mm
c = 6.0 mm between two letters of one word
d = 10.0 mm +0.0 mm / -0.1 mm line spacing
e = 1.3-1.6 mm is dot diameter

Figure 1: Typical layout of Braille according to the Marbach Medium standard.

There are different Braille systems for different European and other languages where the same symbols sometimes have different meaning. For more complex messages the combination of two signs is in use. Capitals, numbers and special characters have initial character first. Variations of Braille including upgrades to 8 bit inscriptions with 8 dots per cell and alternatives similar to Braille are still interesting subject of research and investigation [Cryer et al., 2008].
The ability to read Braille by sense of touch and transfer of the information through the fingers to create understanding, recollection or simple factual recognition requires that the Braille is fully legible, that the user masters the Braille characters and the tactile sense of the blind user is intact.
Braille is typically applied to packaging through embossing on the press, die-cutter or even folder-gluer, which is the common process for pharmaceuticals, or with the addition of ink-jet or screen-printed label. Labels tend to be more robust than embossing, which can be flattened during transport, or fail to achieve sufficient dot height because the board is too thick or fragile.
There are small differences in symbol dimensions between national Braille systems. To avoid problems the Marbach Medium standard Braille is strongly recommended for pharmaceutical packaging by EC Directive. The height of the dots is not specified for Marbach Medium standard. It is recommended by EC Directive to use the proposal of The National Council for the Blind of Ireland for the height of the dot at 0.5 mm +/- 5 %. However in Standard EN 15823:2008 dot height is specified at 0.20 mm. Braille dot height in national standards and recommendations (not for packaging) vary from 0.25 mm in Sweden up to 1.0 mm in France. International standard Braille dot height for buildings (i.e. elevators) is from 0.6 to 0.9 mm. [Tiresias]
Legibility study on pharmaceutical packaging, concluded in 2008 by the University of Birmingham and RNIB in cooperation with other European institutions, where dot height in the range of 0.06 to 0.23 mm was studied, found the acceptable height of raised Braille dots to be 0.18 mm (67 % of participants definitely recognize text, 27 % probably), but cracking of a board surface was present at this height [Douglas, 2008].
Another difficulty is the measurement method of the height of Braille dots. The use of standard thickness gauge is not suitable because of soft, sensitive dots, the more sophisticated methods, like PixelProof device, are expensive and final evaluation of the results is not always reliable. [Golob, 2007; Golob et al., 2011]

3 Experimental

Evaluation of legibility was performed through two sets of experiments, using InkJet Roland DG LEC-330 UV digital large format printer, applying different modulation of Braille dots. Dot height on printed samples of pharmaceutical packaging boxes was measured using thickness gauge and LM1 laser profile-meter (handheld device using visual measurement option). Dot height at the second set of experiments was measured using mechanical profilometer MarSurf PCV/CD 120 with probe tip CP 350-M7.
Eight persons with different Braille skills and competences from the School at Blind and Weak-sight Institute from Ljubljana made a short verbal description of the quality of printed Braille using different shape and height modulation of each sample of pharmaceutical packaging, which was recorded and transformed for evaluation into the numbers from 5 (best, perfect legible), 3 (good), to 1 (not legible at all, wrong reading).
For the second experiment twelve persons in ages from 12 to 75 assessed short article printed by different specifications.
3.1 Evaluation of Braille using different shapes of dots
A set of samples were prepared for further investigations, using ink-jet Roland DG LEC‑330 UV digital large format printer, applying different modulation of Braille dots (Figure 2). Dot shapes were modulated using 3 or 5 layers of UV varnish, printed on a substrate or on a basic varnish layer, to achieve proper height. As an option, 3 additional layers have been added for rendering the top surface of a Braille dot. Cracked Braille dot was simulated using printed incision and rough surface with a microdot at the surface of the dot peak.

 

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Figure 2: SEM images of ink-jet printed Braille dots: 3 layers on substrate (top left), 5 layers on UV varnish layer (top right), 5 + 3 layers with incision (bottom left) and 5 + 3 layers with microdot on the top (bottom right).

Results of personal evaluation are presented in Table 1. Achieved dot height is highly dependent on substrate preparation. It is clearly visible from Figure 2 that first layer of UV varnish mainly penetrate into substrate.

Table 1: Evaluation results of the samples, printed on ink-jet Roland DG LEC-330 UV digital printer.


Sample

Persons

Dot height (mm)

 

M.A.

I.T.

I.M.

M.B.

B.Š.

M.S.

A.P.L.

M.M.

Average

 

3 layers

5

5

3

3

3

3

3

3

3.50

0.250

5 layers

3

3

5

5

5

5

5

5

4.50

0.420

5 layers + incision

5

3

3

3

3

5

3

3

3.50

0.350

5 layers    + top dot

5

5

5

3

5

3

3

3

4.00

0.350

Average

4.50

4.00

4.00

3.50

4.00

4.00

3.50

3.50

 

 

3.2 Evaluation of Braille printed according different specifications

Second set of samples was prepared for the study of text legibility, at the same ink-jet Roland DG LEC‑330 UV digital large format printer, using three different specifications (Table 2). We applied 3 layers of varnish to achieve required dot height corresponding Small English specification, 6 layers for ECMA Euro Braille and 10 layers for English Giant Dot.

Table 2: Basic characteristics of three different Braille types [Tiresias].


Specification name

Horiz. dot to dot
(mm)

Vert. dot to dot
(mm)

Cell to cell
(mm)

Line to line
(mm)

Dot base diam.
(mm)

Dot height
(mm)

 

a

b

c

d

e

f

Small English

2.03

2.03

5.38

8.46

1.4 - 1.5

0.33

ECMA Euro Braille

2.50

2.50

6.00

10.00

1.30

0.50

English Giant Dot

3.25

3.25

9.78

17.02

1.90

0.81

The profiles of the printed samples were measured using MarSurf PCV/CD 120 with probe tip CP 350-M7 to obtain profile of dot shape, height and diameter for the dots printed according to all three specifications (Figure 3). Results are presented in Table 3.

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Figure 3: Profilometer MarSurf PCV/CD 120 at the measurement process (left) and obtained ECMA Euro Braille dot shape profile with results (right).

Table 3: Braille dot dimensions obtained using MarSurf PCV/CD 120 profilometer.


Specification name

Dot height (mm)

Dot diameter (mm)

Small English

0.25

1.88

ECMA Euro Braille

0.36

1.81

English Giant Dot

0.54

2.19

Results of legibility evaluation show as the most appropriate text, printed according to ECMA Euro Braille specification. Reading time for this Braille specification was less than a minute in all cases, for Small English 4 from 12 readers needs more than one minute, for English Giant Dot one reader needed more than a minute. For two most experienced readers reading time was less than 30 seconds regardless of the specification.
All of the 12 blind people evaluated text printed in ECMA Euro Braille as most legible, the worse was Small English for 6 of them. English Giant Dot was evaluated as Braille with excessive cell dimensions for accurate reading.

4 Conclusions

The number of samples of both experiments and involved blind persons with Braille literacy was not high enough to get optimal statistically valid answers and confirmations. It is evident that even blind persons that are not perfect Braille users can use good UV printed Braille text.
Improvements of ink-jet printed Braille text are in progress. Further improvements in our research work on Braille legibility are expected by optimizing the shape of digital printed dots, optimized for blind readers with lower reading skill. It is interesting that conventional shape of Braille dots printed using ink-jet printing technique were legible very well, however Braille dots with additional features, simulating cracking with incision or roughness of the embossed dots with small dot on the basic dot were confusing even for the experienced blind readers.
Measurement of dot height and control of the dot shape using mechanical profilometer gave us acceptable results, however the improvement of the method and study of alternative methods should give us more reliable results.

Acknowledgement

Authors acknowledge the Grec d.o.o. Grafično ekološki center and Poclain Hydraulics d.o.o. for technical support and the School at Blind and Weak-sight Institute from Ljubljana for cooperation and support.
5 References
Cryer, H. et al.: Identifying areas for research into an alternative tactile reading code, RNIB Centre for Accessible Information, Birmingham, 2008.
Douglas, G et al.: Braille dot height research: Investigation of Braille Dot Elevation on Pharmaceutical Products, Final Report, University of Birmingham, 2008.
EBU Guidelines on Braille Labelling of Medicinal Products, March 2009, http://www.euroblind.org/press-and-publications/publications/nr/46.
Golob, G., Rotar, B.: Braille legibility on the pharmaceutical packaging, Seminar in Graphic Arts, Pardubice, 2007.
Golob, G., Rotar, B., Šulc, D.: Braille dot height impact on the functionality and legibility of the pharmaceutical packaging, Advances in Print and Media Technology, IARIGAI, Budapest, 2011.
Kačič, M. et. al.: Celovita rehabilitacija slepih in slabovidnih, Univerzitetni klinični center, očesna klinika and Zveza društev slepih in slabovidnih Slovenije, Ljubljana, 2010.
RNIB, http://www.rnib.org.uk/aboutus/Research/statistics/Pages/statistics.aspx
Škes, M.: Međunarodni dan bijelog štapa, 15. listopada 2012, http://www.stampar.hr/MedunarodniDanBijelogStapa2012.
The EU Directive relating to pharmaceutical labelling, http://www.rnib.org.uk/xpedio/groups/public/documents/publicwebsite/public_B2B_pharmaFAQ.hcsp.
Tiresias - Scientific & technological reports: Braille Cell Dimensions: http://www.tiresias.org/research/reports/braille_cell.htm.

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