SDAZ(Speed-dependent automatic zooming)的出現對於使用者在搜尋文章題目及圖形時有很大的助益,因為使用者只需要控制捲軸速度,SDAZ就會自動調整文章大小,但在搜尋關鍵字時卻可能因為捲動速度過快或字體過小而感覺眼睛不適,因此本研究以實驗探討螢幕捲動速度和縮放比例之組合對於受測者進行搜尋作業所產生的視覺績效和視覺疲勞之影響。 一般使用者在使用電腦螢幕閱讀資訊時,是依照本身的閱讀速度來控制螢幕捲動速度和縮放比例,因此本研究發現閱讀速度、螢幕捲動速度和縮放比例三者具有關係式存在。本研究將閱讀速度分為200wpm,300wpm和400wpm三種水準以及將縮放比例分為100%、150%和200%。螢幕捲動速度依三者關係式決定。視覺績效和視覺疲勞的指標分別為正確率、閃光融合閾值變化量和視力變化量。 由研究結果顯示閱讀速度對於視覺績效和視覺疲勞皆無顯著影響。但是在正確率的主因子均值表中可以看出閱讀速度300wpm是較合乎受測者本身的閱讀速度,所以平均正確率較其他閱讀速度來得高。因此在捲動式動態資訊設計應考慮到使用者本身的閱讀速度,以提高使用者的視覺績效。縮放比例對於視覺績效無顯著影響,但對於視覺疲勞有明顯的影響,其中以縮放比例為100%對視覺疲勞影響最高。所以本研究建議使用者在進行搜尋作業時應選擇較大的縮放比例來搜尋,以減少視覺疲勞的產生。
The newly proposed document browser tool SDAZ(Speed-dependent automatic zooming)provides a convenient help when users search text headings or pictures. With SDAZ, users only control scroll speed and SDAZ automatically adjusts the zoom level. However, users may feel uncomfortable on eyes for fast scroll speed or if words are too small when searching keywords. In this study, an experiment was carried out to investigate the effect of scroll speed and zoom level on users' visual performance and fatigue. People control scroll speed and zoom level according to reading speed when they use monitor to read information. Thus we found out the relationship of reading speed, scroll speed, and zoom level. Three levels of reading speed are 200, 300, and 400wpm. Zoom level is divided into 100%, 200%, and 200%. Scroll speed is decided by reading speed and zoom level. Visual performance and fatigue are measured by keyword search accuracy, critical flicker fusion frequency (CFF), and visual acuity. Reading speed had no significant effects on visual performance and fatigue. From the mean table of accuracy, suitable reading speed for users is 300 wpm, and the accuracy of 300 wpm is higher then the others. Thus in designing dynamic information scrolling, users reading speed should be considered for better visual performance. Zoom level had no significant effects on visual performance, but had significant effects on visual fatigue, especially when zoom level is 100%. This study suggests users should choose larger zoom level to reduce visual fatigue when search through the document.