Fig. 1. Schematic diagram of interferometer
Fig. 2. Schematic of the optical system of the interferometer
Fig. 3. Change of beam size measurement error with coherence
Fig. 4. Change of coherence with the slit separation
Fig. 5. Schematic of RC focusing mirror
Fig. 6. Relationship between the distance between the light source and the slit and the degree of coherence
Fig. 7. Simulation diagram of interferometer
Fig. 8. Vertical interference fringes and fitting graph (L=30 m, d=16 mm)
Fig. 9. Horizontal interference fringes and fitting graph (L=40 m, d=18 mm)
Fig. 10. Data points and fitted curve
Fig. 11. Effect of intensity imbalance factor on coherence and beam size
$ {L}_{{x}} $![]() /m
| $ {L}_{{y}} $![]() /m
| $ \lambda /\mathrm{n}\mathrm{m} $![]() ![]() | $ \Delta \lambda $![]() /nm
| ${w}_{{x} }\times {w}_{{y} }$![]() ![]() | $ {d}_{{y}} $![]() /mm
| $ {d}_{{x}} $![]() /mm
| $ {f}_{1} $![]() /mm
| $ {f}_{2} $![]() /mm
| vertical | horizontal | 40 | 30 | 500 | 10 | $ 2\;\mathrm{m}\mathrm{m}\times 1\;\mathrm{m}\mathrm{m} $ | $ 1\;\mathrm{m}\mathrm{m}\times 2\;\mathrm{m}\mathrm{m} $ | 16 | 18 | 1000 | 100 |
|
Table 1. Structure parameters of interferometer
| Airy disk radius/μm | RMS radius of spot diagram/μm | wave front error/
$ \lambda $![]() ![]() | cut-off frequency of MTF/(lp·mm−1)
| original design | $ 56.55 $ | $ 24.25 $ | $ 0.207 $ | $ 20.2 $ | new design | $ 36.48 $ | $ 0.05 $ | $0.050$ | $ 33.5 $ |
|
Table 2. Comparison of the results of interferometer optical path quality evaluation
| L/m
| d/mm
| $ \left|\gamma \right| $![]() ![]() | $\sigma /{\text{μ}}\mathrm{m}$![]() ![]() | vertical profile | 30 | 16 | 0.56 | 160.7 | 30 | 18 | 0.47 | 162.9 | 30 | 20 | 0.40 | 161.5 | horizontal profile | 40 | 16 | 0.52 | 227.5 | 40 | 18 | 0.40 | 239.4 | 40 | 20 | 0.42 | 209.6 |
|
Table 3. Results of simulation
fitting value of visibility | true value of the degree of coherence | absolute error of visibility
$ {u}_{\left|\gamma \right|} $![]() ![]() | relative error of visibility
$ {\delta }_{\left|\gamma \right|} $![]() ![]() | $ {V}_{\rm{y}}=\dfrac{2\sqrt{\rho }}{1+\rho }\left|{\gamma }_{\rm{y}}\right| $ | $ \left|{\gamma }_{\rm{y}}\right| $ | $ \dfrac{2\sqrt{\rho }}{1+\rho }\left|{\gamma }_{\rm{y}}\right|-\left|{\gamma }_{\rm{y}}\right| $ | $ \left(\dfrac{2\sqrt{\rho }}{1+\rho }\left|{\gamma }_{\rm{y}}\right|-\left|{\gamma }_{\rm{y}}\right|\right)/\left|{\gamma }_{\rm{y}}\right| $ |
|
Table 4. Error calculation table
L/mm
| $ \lambda /\mathrm{n}\mathrm{m} $![]() ![]() | d/mm
| $ \left|\gamma \right| $![]() ![]() | 30000±10 | 500±10 | 16±0.01 | 0.6±0.06 |
|
Table 5. Parameters of vertical interferometer and measurement standard deviation