Motivated by the key role of point spread function in an imaging system, we propose an interferenceless coded aperture correlation holographic (I-COACH) technology with low speckle and high energy efficiency annular sparse coded phase mask (CPM) as system pupil to improve imaging performance. In the proposed method, a modified Gerchberg–Saxton (GS) algorithm is proposed to obtain a low speckle and high energy efficiency annular sparse CPM and to suppress speckle and increase the intensity of the holograms. Therefore, the randomly distributed amplitude in the bandwidth of the GS algorithm is replaced by the annular amplitude to determine the spatial position, and the band-limited random phase and quadratic phase are used as the initial phase to approximately meet band-limited conditions; meanwhile, in the iterative process of the algorithm, appropriate constraints are imposed on the information within and outside the band limit. All are used for obtaining the CPM with low speckle and high energy efficiency. Therefore, the proposed technique here is coined as low speckle I-COACH owing to the characteristics of CPM and imaging performances. The experimental results show that, under the same experimental conditions, the proposed method can obtain holograms with low speckle and intensity enhancement of about 8%, and further improve the quality of reconstructed images due to the improvement signal-to-noise ratio (SNR) of the holograms. The proposed method provides a powerful reference method for further expanding the I-COACH system to the field of low-intensity optical signals detection and imaging.
Bibliographical noteFunding Information:
Funding. Beijing Municipal Natural Science Foundation (4182016); National Natural Science Foundation of China (61575009).
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