Fig. 1. Spectra and frequency spectra of SO₂ gas
(a): Optical density and differential optical density; (b): Frequency spectrum; (c): Drawing of partial enlargement

Fig. 2. Spectra and frequency spectra of NO₂ gas
(a): Optical density and differential optical density; (b): Frequency spectrum; (c): Drawing of partial enlargement

Fig. 3. Schematic diagram of experimental system

Fig. 4. Error comparison of SO₂ with same concentration

Fig. 5. Error comparison of NO₂ with same concentration

Fig. 6. Error comparison of SO₂ and NO₂ with different zoom multiple

Fig. 7. Errors of different concentrations SO₂ with different zoom multiple

Fig. 8. Error of different concentrations NO₂ with different zoom multiple