Subaru's primary focus camera boasts a very wide field of view of 30 minutes, which is equivalent to the diameter of the full moon as seen from earth, enabling Subaru to make not only very precise, but also speedy observations of the heavens. The only telescope in the world equipped with a glass primary mirror of 8 m in diameter, Subaru is a powerful aid to research on the birth of galaxies and the structure of the universe. Previously, structural considerations prevented heavy optical systems from being placed on top of the primary focus of large reflecting telescopes. This problem was overcome by the development of a smaller and lighter prime focus corrector lens optical system, comprising seven large lens elements in five groups. With a diameter of 52 cm and total weight of 170 kg, this high-precision lens unit is the fruit of Canon's lens design and manufacturing technologies. Stellar light picked up by the world's largest mirror and passed through this unit is focused on a giant CCD unit consisting of ten 4,096 x 2,048 pixel CCDs, producing images of 80 megapixels.