1.1 本试验方法涵盖从飞机透明度的设计眼睛位置观察时，测量次图像与其各自主图像的角度分离。在20×20°视野内的49个点处测量角度分离。本程序适用于在实验室或现场对任何飞机进行透明测试。然而，该程序仅限于黑暗环境。实验室测量在黑暗的房间中进行，现场测量在夜间进行（最好在天文黄昏和天文黎明之间）。 1.2 单位- 以国际单位制表示的数值应视为标准值。国际单位制后括号中给出的值仅供参考，不被视为标准值。 1.3 本标准可能涉及危险材料、操作和设备。本标准并非旨在解决与其使用相关的所有安全问题。 本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 随着厚且角度大的飞机透明胶片的出现，飞行员越来越频繁地将多次成像作为一个光学问题。二次图像（外部灯光）的强度和穿过挡风玻璃的位移经常不同，可以给飞行员提供关于其高度、速度和接近角度的欺骗性光学提示，从而增加其视觉负荷。当前透明胶片中的多重成像规范模糊且不定量。 典型规范规定“多次成像不应引起反对。” 5.2 二次图像和主图像的角度分离与飞行员对挡风玻璃的接受程度有关。该程序提供了一种量化角度分离的方法，以便对透明度进行更客观的评估。本程序用于研究多重成像，量化机组投诉，或作为挡风玻璃规格的基础。 5.3 值得注意的是，挡风玻璃的基本多重成像特性是在设计阶段早期确定的，在挡风玻璃制造后几乎不可能改变。事实上，一个完美制造的挡风玻璃有一些多重成像。对于特定挡风玻璃，建议在选择多重成像的规格标准时小心，因为固有的多重成像特性可能会因挡风玻璃厚度、材料或安装角度而发生显著变化。 建议建立任何公差，以考虑固有的多成像特性。

1.1 This test method covers measuring the angular separation of secondary images from their respective primary images as viewed from the design eye position of an aircraft transparency. Angular separation is measured at 49 points within a 20 by 20° field of view. This procedure is designed for performance on any aircraft transparency in a laboratory or in the field. However, the procedure is limited to a dark environment. Laboratory measurements are done in a darkened room and field measurements are done at night (preferably between astronomical dusk and astronomical dawn). 1.2 Units— The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard. 1.3 This standard possibly involves hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 With the advent of thick, highly angled aircraft transparencies, multiple imaging has been more frequently cited as an optical problem by pilots. Secondary images (of outside lights), often varying in intensity and displacement across the windscreen, can give the pilot deceptive optical cues of his altitude, velocity, and approach angle, increasing his visual workload. Current specifications for multiple imaging in transparencies are vague and not quantitative. Typical specifications state “multiple imaging shall not be objectionable.” 5.2 The angular separation of the secondary and primary images has been shown to relate to the pilot's acceptability of the windscreen. This procedure provides a way to quantify angular separation so a more objective evaluation of the transparency can be made. This procedure is of use for research of multiple imaging, quantifying aircrew complaints, or as the basis for windscreen specifications. 5.3 It is of note that the basic multiple imaging characteristics of a windscreen are determined early in the design phase and are virtually impossible to change after the windscreen has been manufactured. In fact, a perfectly manufactured windscreen has some multiple imaging. For a particular windscreen, caution is advised in the selection of specification criteria for multiple imaging, as inherent multiple imaging characteristics have the potential to vary significantly depending upon windscreen thickness, material, or installation angle. Any tolerances that might be established are advised to allow for inherent multiple imaging characteristics.