- 期刊
- OpenAccess
Dynamic Random-Dot Stereogram Made with IBM PC
IBM微電腦製作動態亂點立體圖
摘要
亂點立體圖的優點在於“空間上”完全不具有單眼線索。而動態亂點立體圖更擴展此一想法，當立體圖形以某一“時間頻率”反轉時，單眼完全不包含此一頻率的成分。 我們以IBM PC/AT微電腦及EGA彩色顯示器製作動態亂點立體圖。另以萬用介面卡產生同步信號引動視覺誘發電位記錄器。 對互補的二張西洋棋盤圖形，各別製作8張1/8濃度、320×200像點的亂點立體圖。每個像點的4個位元，兩張西洋棋盤圖形分用2個位元。第一組西洋棋盤圖形8張亂點立體圖，和螢幕同步，以60Hz的速度循一隨機順序出現，其次展示第二組8張西洋棋盤圖形，周而後始。每一西洋棋盤圖形若展示16次，則圖形以3.75(60/16)Hz的頻率反轉。而單眼所見，除了60Hz亂點翻動之外，絕不包含3.75Hz的成分。在視覺誘發電位波形中，抽取此一頻率的波形，可得到雙眼視覺專屬的誘發電位。 和其他人製作的動態亂點立體圖不同的是(1)我們採用西洋棋盤圖形而非單一方塊，(2)觀看兩組立體圖，雙眼的合散位置固定不變，亦即立體感保持固定，(3)我們在立體圖前景加入紅綠固定點，以利誘發電位的記錄。 此一客觀的立體感測試系對語前幼兒雙眼視覺的評估尤有價值。幼兒立體感發育的可塑期早在2歲之前，而目前臨床上使用的立體感測試在此年齡層均不適用。
關鍵字
無資料並列摘要
Random-dot stereogram (RDS) gets its advantage to isolate binocularity by the absence of monocular cue 'spatially'. Dynamic RDS extends this facility further that binocularly perceived patterns are reversed in certain 'temporal frequency' which is totally absent in the monocular perception. We developed the algorithm to generate dynamic RDS as visual stimulator on IBM PC/AT and EGA monitor. The trigger signals were also flexibly available. Eight random-dot stereograms for each pattern were displayed in random sequence in 60 Hz. Monocular perception got no pattern sensation besides random-dot flickering in 60 Hz. Binocular pattern reversal can be designed to be any multiple of 60 Hz. By isolating this temporal frequency on VEP, either by averaging of Fourier spectrum method, we could record binocular specific VEP. New features in our system included (1) we used checkerboards instead of square blocks, (2) vergence was kept constant for both checkerboards and (3) we added anaglyphical fixation point in foreground plane. This objective method will be invaluable in evaluating binocularity in preverbal children, since the plasticity period of binoucular development is below 2 years of age. No conventional clinical stereopsis test can be applied in these young children.
延伸閱讀
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