In this study, Background-Oriented Schlieren (BOS) technique is employed to measure the temperature field of a methane flame. High speed camera and a wavelet noise background are used to achieve strong spatial and temporal resolution. The basic optical flow algorithm is modified to account for the intensity variation. This is because the flame flow creates a considerable intensity variation between the pair of images under correlation. Principles of geometric optics are used in order to get the index of refraction. The density information is recovered by slotting the Gladstone-Dale equation in filtered back projection. The computed temperature field measurements are shown as a function of time. Finally, the measured temperature is compared with probe measurements. © 2011 Asian Network for Scientific Information.