Absolute distance measurement by lateral shearing interferometry of point-diffracted spherical waves

Abstract

We describe a method of absolute distance measurement based on the lateral shearing interferometry of point-diffracted spherical waves. A unique feature is that the distance measurement is not confined only along a single line of the optical axis, but the target is allowed to take movement freely within a volumetric measurement space formed by the aperture angle of point-diffraction. Detailed measurement theory is explained along with experimental verification.

Retrieving the axial position of fluorescent light emitting spots by shearing interferometry

“…This would also allow using the expansion in Ref. 17 for a reconstruction of the x-and y-positions. In the case of the method presented here, two simplifications can be applied.…”

“…The combination of the method for the recording of the phase with the direct stochastic optical reconstruction microscopy imaging technique enabled a very precise localization of gold nanoparticles in the nanometer range. 16 Lateral shearing setups based on point diffracted spherical waves 17 and a wedged glass plate 18 have been reported for the measurement of 3-D distances in the range of several millimeters 18 up to several hundred millimeters. 17 In this work, a phase-sensitive method for the depth-resolved detection of fluorescent light based on the combination of illumination with an interference pattern arising from two intersecting beams with shearing interferometry is proposed.…”

“…16 Lateral shearing setups based on point diffracted spherical waves 17 and a wedged glass plate 18 have been reported for the measurement of 3-D distances in the range of several millimeters 18 up to several hundred millimeters. 17 In this work, a phase-sensitive method for the depth-resolved detection of fluorescent light based on the combination of illumination with an interference pattern arising from two intersecting beams with shearing interferometry is proposed. This aims at combining the advantages of fluorescence detection and using highly sensitive interferometric signals for the depth evaluation.…”

Fast searching measurement of absolute displacement based on submicron-aperture fiber point-diffraction interferometer

“…Besides, the achievable accuracy of the existing measurement technique is limited by the machining error of standard parts in the system. The method based on point-diffraction interferometer (PDI) [3][4][5][6][7] provides a feasible way for the in-situ high-precision measurement of three-dimensional absolute displacement, in which two optical fibers are applied to generate the lateral shearing spherical wavefronts. The point-diffraction spherical wavefronts from two fibers, which are installed on the target to be measured, interfere with each other, and the absolute displacement of the target can be retrieved from the interference field.…”

“…Thus, the fiber point-diffraction spherical wavefront [8][9][10][11][12][13][14] plays the role as ideal measurement reference, and it determines the achievable measurement accuracy of the system. The numerical aperture (NA) of traditional fiber PDI is smaller than 0.20 [4,5,[15][16][17]. To extend the measurement range with optical fiber, a submicron-aperture fiber [8,18] with cone-shaped exit end has been proposed to get both high-NA and high-intensity spherical wave.…”