Fig. 1. Structural diagram of sensor

Fig. 2. Schematic diagram of reflecting surface with certain curvature

Fig. 3. Electric field diagrams of x-y cross sections with different curvature radii. (a) r_∞; (b) r_L; (c) r_M; (d) r_S

Fig. 4. Reflectance spectra with different curvature radii

Fig. 5. Electric field diagrams of y cross sections with different curvature radii. (a) r_∞; (b) r_L

Fig. 6. Production diagram of Fabry Perot humidity sensor. (a) No discharge; (b) 1 discharge; (c) 2 discharges; (d) Fabry Perot humidity sensor coated with PVA film

Fig. 7. Comparison of reflectance spectra before and after optimization

Fig. 8. Humidity measuring device diagrams. (a) Schematic diagram; (b) physical diagram

Fig. 9. Reflectance spectra and corresponding spatial frequency spectra when humidity increases. (a) Reflectance spectra; (b) spatial frequency spectra

Fig. 10. Curve fitting diagrams of increasing and decreasing humidity

Fig. 11. Wavelength stability at humidity of 29.1%