Fig. 1. (a) Schematic diagram of typical DASH interferometer, where L₁ and L₂ are collimating lenses. L₃ and L₄ are imaging lenses, gratings 1 and 2 are tilted by a Littrow angle θ_L, Δd is the asymmetric offset of two optical arms. Outgoing wavefronts have the same phase. (b) Schematic diagram of the calculation of OPD. Because wavefronts 1 and 2 have the same phase, the OPD at point X on image plane can be obtained by |BX| + |XA|.

Fig. 2. Schematic diagram of wavefronts movement approximation, where red and blue lines represent wavefronts and arrows denote the direction of approximated wavefronts.

Fig. 3. FOV effects and comparisons at [(a) and (c)] 15873 cm⁻¹ and [(b) and (d)] 15803 cm⁻¹. Red lines represent results calculated from Eq. (5). Black dots denote simulation results. Blue lines indicate averaged difference between calculation and simulation results. Averaged difference is obtained by averaging the absolute values of all differences.

Fig. 4. Phase comparisons of OPD offset effect (a) at 15873 cm⁻¹ and (b) at 15803 cm⁻¹. Red lines represent results calculatedfrom Eq. (5). Black triangles represent simulation results. Blue lines indicate averaged difference between calculation and simulation results.

Fig. 5. (a) Averaged interferogram from five recorded pictures. (b) Analysis signal generated from the selected area shown in panel (a). (c) Schematic diagram of inversion phase from analysis signal shown in panel (b). Blue points indicate the retrieved raw phase and red points reptrsent the unwrapped phase.

Fig. 6. Phase variations at 512nd pixel when grating on the linear stage is gradually moved.