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A new development in angle measurement based on the internal-reflection effect (AMIRE) is described in which a pair of right-angle prisms is used to replace the previously used elongated critical-angle prisms, resulting in lower costs and a more compact size. Excellent linearity is achieved through careful alignment of the right-angle prisms. The measurement sensitivity and range can be selected through the use of light sources with different polarization states. Experiments with a prototype sensor demonstrated a measurement range of 1.6 [degrees], a resolution of 0.04 arcsec, and a nonlinearity error of [+ or -]0.1%. Both analytical and experimental results are presented. Key words: Angle measurement, internal reflection, reflectance, right-angle prism.

We describe a new method of angle measurement that is based on the internal-reflection effect at an air-glass boundary. The method uses a differential detection scheme to largely reduce the inherent nonlinearity of the reflectance versus the angle of incidence in internal reflection. With nonlinearity reduced, the displacement of the angle of incidence can be determined accurately by measuring the reflectance. The resolution and measurement range are determined by the initial angle of incidence, the polarization state of the light, and the number of reflections. Compared with interferometers and autocollimators, this method has the advantage of a simple sensor design for applications ranging from a wide measurement range to extremely high resolution. Other advantages are compact size, simple structure, and low cost. A theoretical analysis of the method and some experimental results of a prototype sensor are presented. The possible applications of the method are also discussed.

Elongated critical-angle prisms that provide multiple reflections have been used to increase measurement sensitivity while retaining excellent linearity in the recently developed angle-measurement method, angle measurement based on the internal-reflection effect. Key words: Angle measurement, internal reflection, reflectance, multiple reflections.