心理物理学方法在汉字视标选择中的应用  

Selection of Chinese characters for visual acuity charts using psychophysical methods

作　　者：王晨晓[1] 吕帆[1] 

机构地区：[1]温州医学院眼视光学院,325027

出　　处：《中华眼科杂志》2011年第7期618-622,共5页Chinese Journal of Ophthalmology

基　　金：浙江省自然科学基金（Y2080831）

摘　　要：目的在傅里叶频谱分析的基础上，采用心理物理学方法确定汉字视标的可视性，获得视标物理刺激均等与心理反应均等的异同，确定心理物理学方法在汉字视标选择中的重要作用。方法28位志愿者，裸眼视力或最佳矫正视力为-0．11±0．06（LogMAR值）。分别从汉字图像傅里叶频谱分析所得到的50个各空间频率的频谱能量均值相似的少笔画汉字和40个中笔画汉字中筛选出尽可能包含横、竖、撇、捺结构的中性少笔画和中笔画汉字17个和20个作为备选视标。分别将以上少笔画汉字和中笔画汉字的平均视敏度阈值作为参考值，每个汉字制作成6种字体大小的汉字图片。取所有被试对每个汉字图片在不同字体大小时的辨认准确率的平均值，并用韦伯函数（Weibullfunction）进行拟合，得到字体大小——辨认准确率曲线，并获取每个汉字的阈值大小（tb值）和斜率（B值）。结果17个少笔画汉字的阈值大小为6．16±0．54（单位：分），斜率为5．91±2．18；20个中笔画汉字的阈值大小为8．20±0．71（分），斜率为11．18±3．55。以阈值大小最接近且斜率尽可能接近为筛选指标，最终确定可视性相似的10个少笔画汉字和10个中笔画汉字。选做少笔画汉字视力表视标的汉字为“斤、长、文、尺、万、月、又、不、才、卫”（tb值为5．84±0．36，B值是4．72±0．85），选做中笔画汉字视力表视标的汉字为“孩、郑、怪、构、肾、择、染、秋、软、祝”（tb值为8．38±0．24，B值是10．47±3．9）。结论傅里叶频谱分析方法可以非常客观地从众多汉字中选择出物理刺激相等的汉字，由于汉字视标之间相似的可视性同时表现为视标的物理刺激相似和心理反应的一致性，因此汉字视标的最终选择还需要进行心理物理学的测试。Objective This study investigated the legibility in use of psycho-physical methods to select Chinese characters for visual acuity charts. Methods Twenty-eight subjects with the raw visual acuity or best corrected visual acuity of - 0. 11 ± 0. 06 （LogMAR） were recruited for this study. Ninety Chinese characters with similar Fourier frequency spectrum were used as candidates for the selection of visual targets. Thirty-seven Chinese characters with each consisted of horizontal, vertical and oblique strokes were selected from these candidates. Six different-sized BMP images for each selected Chinese character were made based on the average visual acuity threshold of all the selected characters. The accuracy rate for all subjects to read each size of the BMP images was averaged. Graphs correlating the font sizes with the accuracy rates were formed using Weibull function imitation, which provided a visual acuity （VA） threshold and slope for each Chinese character selected. Results Among the 37 Chinese characters selected, 17 had a VA threshold 6. 16 ±0. 54 （unit： arc） and 20 had a VA theshold of 8.20 ±0.71. The slope for characters with low stroke number and medium stroke number was 5. 91 ± 2. 18 and 11.18 ± 3.55, respectively. Based on the similarity in VA thresholds and slopes, 10 Chinese characters （斤、长、文、尺、万、月、又、不、才、卫） were finally determined as the visual targets for a lower stroke-number Chinese visual acuity chart （tb： 5.84 ± 0. 36, 13 ： 4.72 ± 0. 85 ）. Another 10 characters ＂孩、郑、怪、构、肾、择、染、秋、软、祝＂ （ tb ： 8.38 ± 0. 24, 13 ： 10. 47 ± 3.9） were determined as the visual targets for a medium stroke- number Chinese visual chart. Conclusion Analysis using Fourier frequency spectrum provides an objective method in the selection of Chinese characters for Chinese visual acuity charts. A psychological test for this selection would further confirm the legibility of the method used in this study.

关 键 词：模式识别 视觉 视力测定法 心理物理学 

分 类 号：B841[哲学宗教—基础心理学]