Adaptive optics is a new technique to greatly enhance the resolution of an image. Imaging with adaptive optics systems is becoming common at large astronomical and military telescopes. A modern telescope is the most powerful tool for imaging distant objects at high resolution. The reason is that it can collect light over a large aperture (which is usually a curved mirror several meters in diameter) and can theoretically focus that light into a sharp image. A large-diameter mirror is significantly superior to a small one, since the exposure time is proportional to the inverse square of the diameter. Therefore, a mirror 1 m (40 in.) in diameter will detect a faint object in an 8-h exposure, but an 8-m (320-in.) telescope is 64 times greater in area and will thus image the same object in only 7.5 min. Unfortunately, telescopes of all sizes are limited to blurry images because of the Earth's turbulent atmosphere.