Owing to the resolution of the recording device, digital holograms are generally fabricated with in-line configurations. However, holograms obtained in this way are plagued by the annoying problems of zero-order noise and the twin images. Here, we investigate methods to suppress the zero-order noise. We compare the suppression ability of each method with different ratio factors. The ratio factor is defined as the ratio between the reference light amplitude and the object light amplitude. We also introduce a new parameter, the normalized correlation peak value, to evaluate the fidelities of holograms obtained under various ratio factors. Results show that the suppression abilities and the hologram fidelities strongly depend on the ratio factor. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3596202]
