An infrared imaging method in which direct measurement of energy gap variations can be achieved by digital image processing is proposed. This method allows economic and easy evaluation of the temperature coefficients of a semiconductor energy gap. The key components of the method are a polychromator, a computer equipped with a frame grabber and a variable temperature cryostat. Tentative experimentation conducted on LEC grown semi-insulating GaAs has resulted in a fairly good agreement with the theoretical model. This proposed method could be applicable for most compound semiconductors.