What is an autocollimator?
An autocollimator is an optical instrument that is used to measure small angles with very high sensitivity. As such, the autocollimator has a wide variety of applications including precision alignment, detection of angular movement, verification of angle standards, and angular monitoring over long periods.

Principles of operation
The autocollimator projects a beam of collimated light. An external reflector reflects all or part of the beam back into the instrument where the beam is focused and detected by a photodetector. The autocollimator measures the deviation between the emitted beam and the reflected beam. Because the autocollimator uses light to measure angles, it never comes into contact with the test surface.

Digital vs. Visual Autocollimators

Digital Autocollimators
Digital autocollimators use an electronic photodetector to detect the reflected beam. Micro-Radian autocollimators take advantage of the latest detector technology including advanced silicon-based photodetectors and germanium-based detectors. The detector sends a signal to the Micro-Radian E2 digital controller which digitizes and processes the signal using proprietary DSP-based electronics. The processing creates a calibrated angular output which is traceable to the U.S. National Institute of Standards and Technology. The angular data is retrieved using the digital LCD display, the RS-232 interface, or the analog outputs which are all built into the E2 controller. Digital autocollimators are suitable for applications including calibrating rotary tables, checking angle standards, remote or long term angular monitoring, measurements of flatness or straightness, and to provide angular feedback in servo-controlled systems. Click here for a selection of Micro-Radian digital autocollimators or click here to view the E2 digital controller. Please contact us to discuss tradeoffs and limitations.

Digital Autocollimator Diagram

Visual Autocollimators
Visual autocollimators rely on the operator's eye to act as the photodetector. Micro-Radian visual autocollimators project a pinhole image. The operator views the reflected pinhole images through an eyepiece. Because the human eye acts as the photodetector, resolution will vary among operators. Typically, people can resolve from 3 to 5 arc-seconds. Because the human eye is able to discern mutiple images simultaneously, visual autocollimators are suitable for measuring multiple surfaces simultaneously. This makes them ideal alignment instruments in applications like aligning laser rod ends or checking parallelism among optics. Visual autocollimators can also be equipped with an eyepiece reticle for aid in lining up test optics to a master reference. All Micro-Radian visual autocollimators are focused on infinity for suitable use at any working distance. Click here for a selection of Micro-Radian visual autocollimators.

Visual Autocollimator Sample Applications

Measurement of non-parallelism in windows, laser rod ends, and optical wedges by the two-face reflection method.
Measurement of squareness of an outside corner by aperture sharing.
Angle comparisons by aperture sharing.
Checking right angle prisms for angular and pyramid errors.

Specialized Autocollimators

Laser Autocollimators
Micro-Radian is the only company that manufactures autocollimators with laser light sources. Micro-Radian laser autocollimators have emitted beams as small as 1.0 mm in diameter. These specialized instruments are designed for measuring small test parts including silicon components, miniature mirrors and lenses, and fiber optic components. Micro-Radian laser autocollimators are also available with IR sources and detectors for use in the near-IR. Click here for the TL40 laser autocollimator.

Beam Steering
The Micro-Radian TL40 laser autocollimator is available in a version suitable for measuring the position of an external laser beam. Please contact Micro-Radian for more information and to discuss your application.

Servo-controlled Systems
Micro-Radian digital autocollimators are available in a version suitable for providing angular monitoring in OEM servo-feedback and servo-feedforward systems. Please contact Micro-Radian for details.

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