Abstract
We propose and demonstrate a new imaging technique to noninvasively see through scattering layers with the aid of a spatial light modulator (SLM). A relay system projects the incoherent light pattern emitting from the scattering layer onto the SLM. Two coded phase masks are displayed, one after another, on the SLM to modulate the projected scattered field and the two corresponding intensity patterns are recorded by a digital camera. The above procedure helps to achieve two goals. Firstly, since the coded phase masks are digitally synthesized, the point spread function of the imaging system can be engineered such that the image retrieval becomes more reliable. Secondly, the two recorded intensity patterns are subtracted one from the other and by that the background noise of the recovered image is minimized. The above two advantages along with a modified phase retrieval algorithm enable a relatively easier and accurate convergence to the image of the covered object.
Highlights
A quadratic phase mask with a focal length of 6.9 cm was multiplied with coded phase mask (CPM) synthesized using Gerchberg-Saxton algorithm (GSA) and both were displayed on the spatial light modulator (SLM)
The explanation to the success of the two-shot method is as following; in each intensity pattern measured by the camera after passing through the scattering media there is a dominant bias function, which does not contain any information on the hidden object, but on the other hand, www.nature.com/scientificreports www.nature.com/scientificreports obscures the relatively small signal, which does contain the information about the object autocorrelation
After the elimination of the bias, the autocorrelation of the difference between the two measured intensities mostly contains the information of the covered object autocorrelation as is indicated by Eq (10), and the object itself can be reconstructed by the phase retrieval algorithm operating on this autocorrelation
Summary
The goal of the following mathematical formalism is to obtain the expression of the intensity distribution over the sensor plane for any arbitrary object and diffuser functions. Knowing this distribution might improve our understanding of the parameters which contribute to the quality of the reconstructed images. We choose to represent the object intensity distribution o(r) as a series of delta functions, whereas the diffuser D(r) and the CPM C(r) are represented as Fourier series of linear phases, as following, N.
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