  Recently, ghost imaging has been attracting attentions because its mechanism
would lead to many applications inaccessible to conventional imaging methods.
However, it is challenging for high contrast and high resolution imaging, due
to its low signal-to-noise ratio (SNR) and the demand of high sampling rate in
detection. To circumvent these challenges, we here propose a ghost imaging
scheme that exploits Haar wavelets as illuminating patterns with a bi-frequency
light projecting system and frequency-selecting single-pixel detectors. This
method provides a theoretically 100% image contrast and high detection SNR,
which reduces the requirement of high dynamic range of detectors, enabling high
resolution ghost imaging. Moreover, it can highly reduce the sampling rate (far
below Nyquist limit) for a sparse object by adaptively abandoning unnecessary
patterns during the measurement. These characteristics are experimentally
verified with a resolution of 512 times 512 and a sampling rate lower than 5%.
A high-resolution (1000 times 1000 times 1000) 3D reconstruction of an object
is also achieved from multi-angle images.
