Iterative denoising phase retrieval method for twin-image elimination in continuous-wave terahertz in-line digital holography

•An iterative denoising phase retrieval method is proposed to solve the twin-image problem in continuous-wave terahertz in-line digital holography.•The positive absorption constraint and the denoising processing are combined to be applied simultaneously at the object field to further enhance the object constraint.•The complex object field is decomposed into real and imaginary parts for denoising respectively.•The iterative denoising phase retrieval method exhibits good robustness to noises existing in the hologram.