Methods and systems for non-contact temperature measurement of an object on which is attached or etched a diffraction grating. The diffraction grating expands and contracts as the object expands and contracts upon there being a change in temperature of the object. Upon a light beam being received on the diffraction grating, the diffraction grating produces a pair of complementary light beams and one of the light beams is reflected back onto the diffraction grating and then onto the other light beam in a manner that causes the reflected light beam to propagate alongside and non-parallel to the other light beam. The resultant two light beams are thereafter impinged onto a camera at respective first and second impingement locations. The temperature of the object is then determined based on the separation distance between the first and second impingement locations.