  Image Rotation and Subtraction (IRS) is a high-contrast imaging technique
which can be used to suppress the speckles noise and facilitate the direct
detection of exoplanets. IRS is different from Angular Differential Imaging
(ADI), in which it will subtract a copy of the image with 180 degrees rotated
around its PSF center, rather than the subtraction of the median of all of the
PSF images. Since the planet itself will be rotated to the other side of the
PSF, IRS does not suffer from planet self-subtraction. In this paper, we have
introduced an optimization algorithm to IRS (OIRS), which can provide an extra
contrast gain at small angular separations. The performance of OIRS has been
demonstrated with ADI data. We then made a comparison of the signal to noise
ratio (S/N) achieved by algorithms of locally optimized combination of images
(LOCI) and OIRS. Finally we found that OIRS algorithm can deliver a better S/N
for small angular separations.
