Common-path laser encoder

Common-path laser planar encoder

“…The Doppler frequency shift carries the displacement information of the grating scale. In our previous work, we have shown that the Doppler frequency shift is the same within a specific order diffracted beam, whether the diffracted beam is focused or divergent along different incident directions [1]. Consider the 3-D diffraction of a two-dimensional sinusoidal surface relief grating scale with its two grating vectors respectively along the X -and the Y -axes.…”

“…In our previous work, we adopted a pair of rectangular apertures to implement the phase shift [1]. Here, we adopt a pair of circular apertures, 1 A and 2 A , to produce a specific phase shift between the signals measured respectively by the D1 and the D2. Similarly, we adopt a pair of circular apertures, 3 A and 4…”

“…For subnanometer resolution and long-range measurement, the noise level and drift of a measurement system must be small enough. Practically, displacement drift error in a measurement system is frequently more than hundreds of nm per hour [1]. Note that the error contribution of drift generally cannot be averaged out using a number of measurements identically carried out over a reasonable time [2][3][4][5].…”

“…In our previous work, we demonstrate a common-path laser encoder (CPLE) for onedimensional displacement measurement [1]. However, the CPLE cannot measure 2D displacements and geometrical errors of a precision stage.…”

Heterodyne common-path grating interferometer with Littrow configuration

“…Their grating interferometer has a measurement resolution of 2.3 nm over a 20-mm range. In our previous work, we presented a common-path laser encoder (CPLE) [9]. The CPLE has a measurement resolution of 0.1 ± 0.046 nm.…”