Simultaneous spatial and angular positioning of plane specular samples by a novel double beam triangulation probe with full auto-compensation

• Simple double beam triangulation method with full auto-compensation.Simultaneous spatial and angular positioning of plane specular samples.
• The setup uses a single source and a single detector.
• Both the spatial and the angular positions are determined from the relative distance of the beams on the detector.
• The second beam doubles the resolution of the measurement.

The positioning of a plane specular sample to be measured or processed is an important requirement in many fields of research and industry. Where a sample is to be processed either by electromagnetic waves or a particle beam of higher numerical aperture the irradiance or the particle number over unit area is position and angle dependent. Where optical properties of a sample are to be measured, such as in spectrophotometry, these parameters can depend on the angle of incidence and on the value of the irradiance, i.e. on the angular and spatial position of the sample. In some cases parameters of many samples have to be compared among each other or to those of a standard, this also requires the highly accurate positioning of each sample to the same position. This paper describes a method that is suitable for high accuracy alignment of specular plane samples both angularly and spatially. It applies a double beam triangulation probe, where the second beam serves not only as a reference beam to compensate for any changes of the transmitting media and that of the laser but also doubles the sensitivity of the probe. The method does not compete with interferometric methods, it is required only in special applications, but provides an absolute uncertainty for spatial positioning in the sub-micrometer range and an angular one in the 0.0003° range. Furthermore, the accuracy is tunable by the parameters of the setup.