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Xinyu Chai, Yao Chen, Yanyu Lu, Cong Dai, Qiushi Ren; Correction of Irregular Phosphenes Mapping for Chinese Character Recognition Based on Simulated Prosthetic Vision. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4971.
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© ARVO (1962-2015); The Authors (2016-present)
To correct irregular phosphenes mapping in visual prosthesis and improve the efficiency and accuracy of Chinese character recognition. In this study, three correction methods were put forward and their effects on alleviating the negative influence brought by distorted simulated phosphene arrays on Chinese character recognition were tested.
The system was consisted of a personal computer with a 17-inch CRT screen, a self-developed experimental software and a self-designed light shielding device. Twenty volunteers from 21 to 30 years old with normal or corrected to normal visual acuity of 20/20 were recruited in the study. The experimental materials were the most common 500 Modern Chinese characters, which were pixelized to 12 × 12 array. A two-dimension Gaussian distribution with zero mean and mutual independence was used to simulate the positional uncertainty of the phosphenes. The irregularity levels took 0.2,0.4,0.6,0.8 and 1.0 five values. Chinese character recognition tests were given to subjects under five degrees of array irregularity without correction. When the recognition accuracy dropped below 80%, two correction methods were applied and the effect on improving Chinese character recognition accuracy was investigated. The first correction method was to present phosphenes located in the region covered by shape-regulated characters. The second one was to present phosphenes closest to those in regular arrays. In order to reduce the effects of familiarity and adaptability, the testing sequence was in term of random.
With the increase of distortion levels, the recognition rate decreased obviously while the correction effects on the efficiency and accuracy of recognition increased considerably. Comparison between the two methods revealed that the former method afforded higher recognition accuracy and the latter only applied to phosphene map with serious irregularity.
The results indicated that correction of irregular phosphene mapping played an important role in the improvement of Chinese character recognition. A proper correction method would work effectively especially when phosphene arrays appeared seriously disordered.
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