Point source detection with and without the convolution of Laplacian. (a) Measured PSF, (b) r-band data, (c) the sharpened image of PSF, and (d) the sharpened image of r-band data. The sharpened images are obtained by convolving the Laplacian of the image with the Laplacian of the corresponding PSF (see Eq. (1)). We replace the negative values with zeros in (c) and (d) due to the byproduct of this convolution. The red crosses in (b) and (d) indicate the point source detection using DAOStarFinder with 2D Gaussian kernels fitted from (a) and (c), respectively. The sharpened image (d) with improved dynamical range allows us to detect blended images better as shown in the red central cross.