Reconstruction of off-axis lensless Fourier transform digital holograms based on angular spectrum theory

Abstract

A simple holographic high-resolution imaging system without pre-magnification，which is based on off-axis lensless Fourier transform configuration, has been developed. Experimental investigations are performed on USAF resolution test target. The method based on angular spectrum theory for reconstructing lensless Fourier hologram is given. The reconstructed results of the same hologram at different reconstructing distances are presented for what is to our knowledge the first time. Approximate diffraction limited lateral resolution is achieved. The results show that the angular spectrum method has several advantages over more commonly used Fresnel transform method. Lossless reconstruction can be achieved for any numerical aperture holograms as long as the wave field is calculated at a special reconstructing distance, which is determined by the light wavelength and the chip size and the pixel size of the CCD sensor. This is very important for reconstructing an extremely large numerical aperture hologram. Frequency-domain spectrum filtering can be applied conveniently to remove the disturbance of zero-order. The reconstructed image wave field is accurate so long as the sampling theorem is not violated. The experimental results also demonstrate that for a high quality hologram, special image processing is unnecessary to obtain a high quality image.

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“…This property makes ASM ideal for our experimental setup as it does not have any distance limitations. In summary, ASM has been chosen due to its ability to maintain high-quality image resolution over various distances, providing an efficient and reliable tool for our experimental analysis [22] .…”