Fig. 1. The basic optical diagram of FMCW laser ranging

Fig. 2. HCN gas cell signal diagram

Fig. 3. Schematic diagram of FMCW ranging system based on HCN gas cell

Fig. 4. Schematic diagram of HCN absorption peak phase fitting

Fig. 5. HCN combined with resampling multiline ranging system

Fig. 6. Error comparison of three measurement methods

Fig. 7. Differential error bar with a step of 10 mm

Fig. 8. Signal comparison diagram. (a) Before resampling and filtering；(b) After Resampling and filtering

Fig. 9. Comparison chart of the results of three measurement methods

Fig. 10. The standard deviation of four-way measurement at different positions

Fig. 11. Four-channel measurement differential error bar