**Appendix A**


**Table A1.** Theoretical evaluation values (orthogonal arrays) for the measurement uncertainty of focal length (unit: mm) under different focal lengths, relative distances, and periods of grating (with Δ*p*1 = 0.001 mm, Δ*p*2 = 0.01 mm, Δ*d*2 = 0.01 mm, Δ*α* = Δ*θ* = 0.01◦).
