High accuracy profile measurement of quasi-conical mirror surfaces by laser autocollimation

A three-axis autocollimator for detection of angular error motions of a precision stage

“…A 0 and A 1 are the initial positions of the 0th-order and the 1st-order diffracted beam spots, respectively. If the distance between A 0 and A 1 is denoted by L, L can be expressed by [14] L ¼ f tan f 1st (1) where f is the focal length of the collimator objective. f 1st is the diffraction angle of the 1st-order diffracted beam, which is given by [15] …”

“…In the detection, a light beam from the autocollimator is projected onto a flat mirror reflector along the surface normal of the mirror, which is mounted on the stage moving table. The reflected beam from the flat mirror reflector is received by the autocollimation unit, which consists of a collimator objective and a two-directional light position-sensing detector placed at the focal plane of the collimator objective [14]. Based on the principle of autocollimation, the pitch and yaw errors will be converted into Y-and X-directional linear displacements of the light spot on the detector, respectively, from which the pitch and yaw errors can be simultaneously detected.…”

Measurement technologies for precision positioning

“…The shortcomings of a conventional autocollimator can be overcome by using a laser diode as the light source [41]. The laser beam is collimated to a thin parallel beam with a diameter of approximately 1 mm.…”

Design and Testing of a Micro-thermal Sensor Probe for Nondestructive Detection of Defects on a Flat Surface

“…However, regarding the substrate size of microthermal sensor (20 mm 9 20 mm), a parallelism of better than 2 arc-seconds is at least required between the microthermal sensor surface and a target surface. Therefore, in this paper, an optical tilt detection assembly based on the laser autocollimation [22] is designed to detect tilts of both the micro-thermal sensor and a target surface. A schematic of the sensor tilt measurement by using the optical tilt detection assembly based on the laser autocollimation is shown in Fig.…”