Fig. 1. Schematic of projective background-oriented schlieren apparatus

Fig. 2. Offset of light generated after flow field measurement

Fig. 3. Refractive index distribution function and projection

Fig. 4. Flow chart of proposed algorithm

Fig. 5. Results for each process. (a) Image capture; (b) image filter; (c) correlation analysis; (d) temperature field reconstruction

Fig. 6. Correlation analysis of images. (a) Correlation function; (b) schematic of correlation analysis process; (c) offset of particles in x-axis direction; (d) offset of particles in y-axis direction

Fig. 7. Offset of particles in x-axis direction. (a) Flame tip interception at moment 1; (b) flame tip interception at moment 2; (c) offset of particles in x-axis direction

Fig. 8. Photograph of measurement instrument

Fig. 9. Flame tip interception

Fig. 10. Comparison among flame tip interceptions at different moments. (a) Moment 1; (b) moment 2

Fig. 11. Particle offset. (a) x-axis; (b) y-axis

Fig. 12. Refractive index gradient at flame tip

Fig. 13. Refractive index at flame tip

Fig. 14. Density gradient at flame tip

Fig. 15. Density at flame tip

Fig. 16. 3D reconstruction of temperature field at flame tip

Fig. 17. Temperature distribution on tangent surface at flame tip