Perceived Transparency in Optical See-Through Augmented Reality

Optical see-through (OST) displays overlay rendered images to the real-world background creating augmented reality (AR). But the blending between the rendering and the real-world background introduces perceived transparency. The increased luminance on the rendering decreases the background contrast, and reduces the perceived transparency, which is not incorporated in existing color appearance models or display color management pipelines. We studied the perceived transparency in AR focusing on the interaction between the rendering and the patterned background in various luminance, contrast, and wave forms. In addition to AR contrast, we also examined simulated contrast modulation by changing the luminance amplitude. Two psychophysical experiments were conducted to quantify the perceived transparency. The first experiment measured a perceived transparency scale using direct scaling, and the second experiment evaluated the transparency equivalency between two methods of contrast modulation. The result showed that the two methods evoke different transparency perceptions. The background contrast affects the perceived AR transparency significantly, while the background luminance and wave form do not. We proposed a model predicting the perceived transparency based on the first experiment result from AR luminance and background contrast. The model was verified with the second experiment and showed good prediction. Our model presented a new perceptual dimension in OST AR and can possibly be incorporated into color management pipeline to improve AR image quality.