High-resolution lens-coupled indirect X-ray scintillator imagers are required by many imaging applications. However, the severe weakening of image details prevents its further performance improvement. Through our research, this image degradation is attributed to the broadband loss of the high-spatial-frequency information caused by the high refractive index. A technique known as high-spatial-frequency spectrum enhanced reconstruction is thus proposed to retrieve this information. A two-dimensional high-density array is covered on the scintillator’s exit surface and operates as an encoder based on which high-frequency information can be shifted to the low-frequency region to improve the signal-to-noise ratio. The experimental results show that the middle-high-frequency signal intensities can be increased by an order of magnitude or more, up to $～50$ times. Therefore, the image details can be effectively enhanced to break through the performance bottleneck of such widely used X-ray imagers for synchrotron radiation facilities or tabletop X-ray tubes.