Electronic Autocollimators
Electronic Autocollimators
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电子自准直仪
DOI：
10.1117/12.959449
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
Thomas H. Thurston
中科院分区：
文献类型：
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作者：
Thomas H. Thurston
自准直仪是一种光学仪器，它使用自己的准直光来检测反射镜的微小角位移。电子自准直器提供连续的输出电压，其符号和幅度与反射镜位移成比例。电子自准直器的设计和性能考虑进行了讨论，重点是内部和外部噪声，带宽和灵敏度之间的权衡，光源的选择，和用途。包括不同类型的自动准直仪和附件选择标准的审查。自动准直仪的类型所有的自动准直仪都体现了相同的基本设计：物镜透镜焦平面上的标线图案被投射到反射镜上。反射镜将该投射光的全部或部分返回到物镜透镜，物镜将光聚焦在焦平面上，其中可以使用若干方法中的任何一种来将掩模版的返回图像与掩模版本身进行比较或者检测返回图像的移动。如何进行这种比较决定了自准直仪的类型。有三种主要类别或类型的自准直仪：第一种和最知名的是视觉自准直仪。最简单的视觉自准直仪需要操作员通过目镜观察并比较两个或多个返回图像的位置。这些“校准”自动准直仪基本上是通/不通的设备，用于验证两个或多个反射表面的校准，最佳精度约为5弧秒。如果规定在视场中移动返回图像，或者在返回图像中移动第二个目镜十字线，我们就有了一个视觉测量自准直仪。这些仪器允许操作员测量两个图像之间的角度，精度约为1弧秒。这些仪器中的一些仪器的测量刻度盘的刻度可降至十分之一秒，但在实践中，在目镜中观察时，通常很难（如果不是不可能的话）看到小于一弧秒的图像移动。视觉自动准直仪通常用于静态系统的测量。测量的最终准确度在很大程度上取决于观察者的视觉敏锐度及其持久能力。也许这些仪器最重要的特点是它们的能力，具有人眼作为探测器，同时容纳一个以上的返回图像，以及它们固有的2轴能力。第二种类型的自准直仪是自动自准直仪。这是最复杂的自动准直仪，有一个伺服电机驱动系统，用于连续寻找和保持零位。该系统通过在自准直仪内重新对准、偏移或偏离返回光来自动改变返回光的方向，以使返回光线以预定图案聚焦。当满足该模式或条件时，自准直仪被称为"归零"。"如果镜子应该移动到一个新的位置，错误信号循环通过伺服电机将驱动系统重新建立零条件。今天制造的自动准直仪很少。由于其光学和机械复杂性，特别是在2轴模型中，它们非常昂贵。对于许多现代应用，它们受到其重量和尺寸以及3 - 4 Hz的有限动态带宽的限制。它们的优点是，如果反射镜部分被遮挡，则可以提供恒定的输出。第三类自准直器是电子自准直器，其提供连续的输出电压，其符号和幅度与反射镜的角位移成比例。Electornic自动准直仪提供所有自动准直仪中最好的全方位性能。特别是，它们可以提供紧凑的尺寸、非常高的灵敏度、高动态带宽和非常低的漂移。电子自准直仪通常由光学头和电子单元组成。光学头包含所有的光学元件、光源、检测器、前置放大器和通常的机械测量装置。电子单元具有稳压电源、灯驱动电路、解调器和相位检测器电路、面板仪表、增益控制和便于与计算机或记录器接口的输出插孔或连接器。设计考虑在电子自准直仪中有几个因素的相互作用，仪器的最终性能取决于这些因素中的每一个对于46/SPIE 251光学校准（1980）0-弧度I trts，rted，69的重要性
An autocollimator is an optical instrument which uses its own collimated light to detect small angular displacements of a mirror. Electronic autocollimators provide a continuous output voltage, the sign and amplitude of which are proportional to the mirror displacement. Design and performance considerations of electronic autocollimators are discussed with emphasis on internal and external noise, the trade -off between bandwidth and sensitivity, selection of light sources, and uses. Included is a review of the different types of autocollimators and the criteria for selection of accessories. Types of autocollimators All autocollimators embody the same basic design: a reticle pattern at the focal plane of an objective lens is projected onto a mirror. The mirror returns all or part of this projected light back to the objective lens, which focuses the light on the focal plane, where any of several methods may be used to compare the return image of the reticle with the reticle itself or to detect movement of the returned image. How this comparison is made determines the type of autocollimator. There are three main categories or types of autocollimators: first and best known is the visual autocollimator. The simplest type of visual autocollimator requires the operator to look through an eyepiece and compare the positions of two or more returned images. These "alignment" autocollimators are basically go /no -go devices good for verifying the alignment of two or more reflecting surfaces to a best accuracy of about 5 seconds of arc. If provision is made to move the return image across the field of view, or move a second eyepiece reticle across the return image, we have a visual measuring autocollimator. These instruments allow the operator to measure the angle between two images to an accuracy of around one arc second. Some of these instruments have their measuring dials graduated down to tenths of a second, but in practice, it is usually very difficult, if not impossible, to see an image movement of less than one arc second when looking in the eyepiece. Visual autocollimators are normally used for measurements of static systems. Ultimate accuracy of measurements depends to a large extent on the visual acuity of the observer and the lasting power thereof. Probably the most important features of these instruments are their ability, having the human eye as a detector, to simultaneously accomodate more than one return image, and their inherent 2 -axis capability. The second type of autocollimator is the automatic autocollimator. This, the most complex of the autocollimators, has a servo -motor driven system for continuously seeking and maintaining null. This system automatically changes the direction of the returned light by reaiming, off -setting, or deviating it within the autocollimator, to cause the return rays to come to a focus in a predetermined pattern. When this pattern or condition is satisfied, the autocollimator is said to be "nulled." If the mirror should move to a new position, the error signal looped through the servo -motor will drive the system to reestablish the null condition. Few automatic autocollimators are made today. Due to their optical and mechanical complexity, especially in 2 -axis models, they are quite expensive. For many modern applications they are limited by their weight and size as well as by their limited dynamic bandwidth of 3 -4 Hz. They have the advantage of giving a constant output if the mirror is partly obscured. The third category of autocollimators are the electronic autocollimators, which provide a continuous output voltage, the sign and amplitude of which are proportional to the angular displacement of the mirror. Electornic autocollimators offer the best all around performance of all the autocollimators. In particular, they can offer compact size, very high sensitivities, high dynamic bandwidths, and very low drift. Electronic autocollimators normally consist of an optical head and electronic unit. The optical head contains all the optical components, the light sources, a detector, a pre -amp and usually a mechanical measuring means. The electronic unit has regulated power supplies, a lamp driving circuit, demodulator and phase detector circuits, a panel meter, gain control and an output jack or connector to facilitate interfacing with computers or recorders. Design considerations The interaction of several factors come into play in an electronic autocollimator, and the ultimate performance of the instrument will depend on how important each of these factors is considered for a 46 / SPIE Vol 251 Optical Alignment (1980) 0 -Radian I tr ts, r ted, 69