Active optics technology using 261 actuators

The active optics technology used in the Subaru Telescope deploys two key characteristics. The first is the sheer number of actuators. The second is that the actuators are embedded directly in holes in the back of the primary mirror, to enhance correction precision. The Subaru Telescope is a reflective telescope with a monolithic mirror more than 8m in aperture. To prevent this enormous mirror from warping and maintain sharp images of stars at all times, an advanced technology called active optics is required.

To minimize the weight of the Subaru Telescope's primary mirror, its thickness is pared to just 20 cm. Unfortunately, this thin profile causes the mirror to warp under its own weight when tilted, reducing the precision of the painstakingly crafted mirror surface. To correct this problem, 261 robot fingers called actuators support the primary mirror, maintaining it in an ideal shape no matter what its orientation.

Active optics technology using 261actuators