The objects were six grey squares placed strategically throughout the volunteer's field of vision.

需要追踪的物体为六个灰色的正方形，它们被有规律的放置在志愿者的视野范围内。

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Abstract: According to the excessive error factors and difficult analysis of the binocular vision measurement systems, an error analysis method based on grey incidence technology was proposed.

摘要：针对双目视觉测量系统存在误差因素繁多、分析困难等问题，提出了一种基于灰色关联技术的误差分析方法。

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He is now employing a vision test used by the US Air Force which checks the ability to discriminate between white, black and grey - the lack of which is another symptom often seen in chronic ciguatera.

BBC: Fish food poisoning breakthrough