單雙眼遮蔽線索對立體視覺中影像回復的影響

The Effect of Monocular and Binocular Occlusion Cues on Stereoscopic Image Recovery

Shimojo與Nakayama（1990）指出遮蔽關係限制了環境中的影像回復，由近的平面遮蔽遠方產生僅單眼可見區域是促使立體知覺形成的要件。此外Nakayama、Shimojo及Silverman（1909）也表示在立體視覺中，由單眼可見遮蔽線索與雙眼像差組成的遮蔽關係是影響影像回復的重要因素。實驗一以袁之琦（1986）的實驗典範，檢驗Nakayama等人（1989）提到的遮蔽關係對於立體視覺情境中錯覺輪廓（illusory contour, IC ）的生成以及物體深度判斷的影響。由於實驗一結果顯示單雙眼深度線索皆為影響立體影像回復的因素，故實驗二進一步檢驗融合單雙眼線索的遮蔽合理性是否為影響圖形深度判斷的重要因素。此外也操弄不同遮蔽物與背景類型，以驗證Bacon與Mamassian（2002）認為即使在圖形中目標位置無法形成雙眼配對，只要具有合理遮蔽關係依然不影響深度回復的看法。由受試者在不同的遮蔽物或背景對類型有不同的凹反應率，實驗二反映出雙眼配對元素對影像深度的穩定是重要的。雖然合理遮蔽對影像還原的影響未達顯著，但具有合理遮蔽的情況仍能促使凹反應與圖形設計更加吻合。在本研究的實驗中除了看到單眼遮蔽線索與雙眼像差本身對影像回復的影響，也看到兩種線索之間對作業表現具有加成效果。此結果支持單雙眼深度視覺管道可能具有一定互動關係，兩者同時對立體視覺中影像的回復具有影響，這也符合視覺系統在視覺訊息愈豐富之下，影像回復的品質愈佳的特性。

Shimojo and Nakayama (1990) pointed that for real world scenes there are opto-geometrical constraints which determine whether particular combinations of relative depth and right-eye-only or left-eye-only stimuli are ecologically valid or invalid. Moreover, Nakayama, Shimojo, and Silverman (1989) suggested that occlusion relation composing of monocular occlusion cue and binocular disparity is important to image recovery. Experiment 1 examined the importance of occlusion relation in illusory contour (IC) formation and depth discrimination task which were designed for different binocular and monocular occlusion conditions. The exp1 result showed that both binocular disparity and monocular occlusion cue are essential to stereoscopic IC recovery. The absence of either cue or conflict of each other reduced the task performance of participants, while the congruence condition generated the best. Experiment 2 used similar condition of Bacon and Mamassian (2002), but manipulated three kinds of background and occluder to test the influence of occlusion relation, and the suggestion Bacon and Mamassian showed that amodal completion allows visual system to assign stereoscopic depth in the absence of binocular correspondence. Although the main effect of occlusion relation in exp2 wasn't significant, there was a trend that legal occlusion relation improved the possibility of task performance corresponding to the true experimental condition. On the basis of different concave-response rate in different kinds of background and occluder, we may take Bacon and Mamassian's study as a special case and suggest that the more binocular correspondence unit be, the more stable depth we will capture. Our results supported that both monocular and binocular occlusion cues play important roles in stereoscopic image recovery, and the interaction between these two cues might indicate the integration of two processing channels.