High-resolution true-color imaging based on wavelength-multiplexed far-field spatial-frequency shift imaging

As an innovative computational imaging technique proposed in recent years, spatial-frequency shift (SFS) technique shifts the high-frequency components into the passband of the system, thereby successfully overcoming the intrinsic trade-off between resolution and field-of-view (FOV). However, in practical far-field SFS scenarios, the extended propagation distance may lead to the degradation of the coherence and introduce ambient noise. Besides, color information is crucial for revealing subtle details, whereas most of the extant far-field SFS research concentrates on monochromatic recovery. Here, we report a high-resolution (HR) true-color imaging, termed wavelength-multiplexed far-field spatial-frequency shift (WMSFS). We demonstrate that WMSFS yields an enhancement in Signal-to-Noise Ratio (SNR) under high-level noise contamination. The WMSFS approach is also validated experimentally with the USAF 1951 resolution chart and butterfly wings sample. 2.83-fold spatial resolution improvement with accurate representations of color was achieved for the sample over a 1 m distance. Compared with conventional single-wavelength far-field SFS, WMSFS is capable of achieving true-color restoration of objects without compromising the high-resolution capabilities of the system. Further hyperspectral and high-resolution remote imaging might be obtained simultaneously based on this method.