Deceptive Iridescence

虹彩是自然界中广泛存在的材料的一种特性，并且在一系列工业中越来越多地使用。我们的目标是确定它是否可以作为一种欺骗性的伪装，如果可以，如何发挥作用。了解拥有这种颜色的成本和收益不仅有助于解释它们在自然界中的广泛存在，还有助于指导它们在商业、安全和国防应用中的有效使用。颜色是自然界不可或缺的、引人注目的特征，在植物和动物王国中都有不同的功能——从增强植物光合能力的色素到鸟类鲜艳的羽毛。然而，有一种颜色——虹彩——的功能还没有被完全理解。彩虹色被称为“结构”色，因为反射光的色调是由于材料的结构而不是化学性质。虹彩的定义特征是物体的颜色随着观察角度的变化而变化。动物和植物都有多种产生和改变虹彩的方式，这些方式有不同的视觉效果。这些生物机制中的许多已经被描述出来，并且可以被合成地复制，这些产生颜色的方法越来越多地应用于各种行业，从汽车涂料（它们的作用是创造一种引人注目的视觉冲击）到银行纸币的生产（复杂的颜色变化很难伪造）。圣诞包装纸和孔雀尾巴上的彩虹色显然是为了吸引眼球而设计的，但并不是所有的彩虹色都可以这样解释。彩虹的一个基本特性是，当物体或观察者移动时，它会改变颜色。这意味着它可以通过几种机制作为有效的伪装——变化的阴影可以破坏物体的轮廓，通过分散视觉系统对其他识别特征的注意力，和/或作为一个动态的“炫目色彩”来迷惑观众。PI收集的试点数据表明，这些可能性中至少有一种是有效的，因为彩虹色使蜜蜂很难区分物体的形状。我们提出的研究旨在测试这些可能性。我们将重点关注陆地动物的虹彩。我们将研究它对识别、区分和跟踪物体的能力的影响，使用三种具有非常不同视觉系统的模型动物——蜜蜂、鸟类和人类。标准的彩虹“目标”材料，或不同类型，将与商业公司合作生产。它们的颜色将通过一个能够记录从紫外线到红外线的特定波长的专用摄像机来表征，该摄像机连接在机器人手臂上，可以将摄像机和光源移动到任何相对角度。光谱信息将与蜜蜂、鸟类和人类的视觉知识相结合，以模拟我们每个模型物种所看到的颜色和形状。接下来将进行一系列行为实验，以确定虹彩对物体检测、物体识别以及对物体速度和轨迹的准确评估的影响。最终，我们的目标是回答这个问题——彩虹是否能够干扰视觉系统，以至于它可以作为一种迄今为止未被怀疑的、但极其广泛的伪装形式发挥作用？除了了解自然界彩虹的功能和多样性外，这项研究还可能产生重要的社会影响。对目标识别的干扰在军事和安全（防止文件欺诈）应用中都是相关的。虹彩也越来越多地应用于许多行业，但没有清楚地认识到有益的视觉影响（在某些视角下的显著性，吸引注意力）是如何被成本（干扰识别和定位）所抵消的。了解进化是如何“解决”这些权衡的，将有助于我们更有策略地使用彩虹色。

Iridescence is a property of materials both widespread in nature and of growing use in a range of industries. We aim to determine whether it can function as a form of deceptive camouflage and, if so, how. Understanding the costs and benefits of having such colours will not only help explain their widespread occurrence in nature, but also help direct their efficient use in commercial, security and defence applications.Colour is an integral, and striking, feature of the natural world and has diverse functions in both plant and animal kingdoms - from pigments that enhance the photosynthetic capacity of plants to the vivid plumage of birds. However, the function of one sort of colour, iridescence, is not yet fully understood. Iridescence is termed a "structural" colour because the hue of the reflected light is due to the structural rather than chemical properties of a material. The defining feature of iridescence is that the colour of the object changes with changing angle of viewing.In both animals and plants there are multiple ways of producing and modifying iridescence, and these have different visual effects. Many of these biological mechanisms have been characterised and can be reproduced synthetically, and these methods of producing colour are increasingly used in various industries, from car paints where their role is to create a striking visual impact, to the production of bank notes, where the complex colour variation is hard to forge. The iridescent colours of Christmas wrapping paper and peacocks' trains are clearly designed to attract attention, but not all iridescence can be explained this way. A fundamental property of iridescence is that it changes colour when either the object or observer moves. This means it could act as effective camouflage through several mechanisms - the shifting shades could disrupt object outline, by distracting the visual system from other identifying features, and/or by acting as a dynamic 'dazzle coloration' to confuse the viewer. Pilot data collected by the PI suggests at least one of these possibilities is effective, as iridescence makes it hard for bees to discriminate between the shapes of objects. Our proposed research aims to test these possibilities. We will focus on iridescence in land animals. We will investigate its impact on the ability to identify, discriminate and track objects using three model animals with very different visual systems - bee, bird and human. Standard iridescent 'target' materials, or different types, will be generated in collaboration with commercial companies. Their colours will be characterised using a specialised camera able to record specific wavelengths from the ultraviolet to the infra-red, attached to robot arms that can move the camera and light source to any relative angle. The spectral information will be combined with knowledge of bee, bird and human vision to model the colours and shapes as seen by each of our model species. This will be followed by a series of behavioural experiments to determine the impact of iridescence on object detection, object identification, and accurate evaluation of object speed and trajectory. Ultimately, we aim to answer the question - can iridescence interfere with visual systems to the extent that it could function as a hitherto unsuspected, but extremely widespread, form of camouflage? As well as understanding the function and diversity of iridescence in nature, this research could also have important societal impacts. Interference with object identification is relevant in both military and security (document fraud prevention) applications. Iridescence is also increasingly being used in many industries without a clear understanding of how the beneficial visual impact (conspicuousness at some viewing angles, attraction of attention) are offset by costs (interference with recognition and localisation). Understanding how evolution has 'solved' these trade-offs will help us use iridescence more strategically.