Hadamard speckle contrast reduction for imaging system: Comprehension and evaluation

Coherent imaging systems always suffer from speckle phenomenon, which blurs the image, and therefore making the information extraction quite difficult. Hadamard speckle contrast reduction (SCR) is considered to be effective to deal with this problem in optics. In this paper, we explore the working principle and effectiveness of this approach, from mathematical deduction to system simulation, and from optics to millimetre wave frequencies, so as to understand why it works and how well it can perform. We show that the effectiveness of Hadamard SCR is linked to the texture of the objects´ surface. The investigated cases are in the region of both millimetre wave frequencies and optics, but it should be clear that it is a wave-oriented discussion and therefore the problem should be considered in terms of electrical size, beyond the limitation of working frequencies.