  It is of great importance to monitor large solar active regions in the
far-side of the Sun for space weather forecast, in particular, to predict their
appearance before they rotate into our view from the solar east limb. Local
helioseismology techniques, including helioseismic holography and
time-distance, have successfully imaged solar far-side active regions. In this
Letter, we further explore the possibility of imaging and improving the image
quality of solar far-side active regions by use of time-distance
helioseismology. In addition to the previously used scheme with four acoustic
signal skips, a five-skip scheme is also included in this newly developed
technique. The combination of both four- and five-skip far-side images
significantly enhances the signal-to-noise ratio in the far-side images, and
reduces spurious signals. The accuracy of the far-side active region imaging is
also assessed using one whole year solar observation.
