Abstract: An optical system affixed to an electronic apparatus is provided, including a first optical module, a second optical module, and a third optical module. The first optical module is configured to adjust the moving direction of a first light from a first moving direction to a second moving direction, wherein the first moving direction is not parallel to the second moving direction. The second optical module is configured to receive the first light moving in the second moving direction. The first light reaches the third optical module via the first optical module and the second optical module in sequence. The third optical module includes a first photoelectric converter configured to transform the first light into a first image signal.

Abstract: A brake disk includes a central hole so as to be connected to a wheel shaft and a serrated periphery which includes a plurality of first protrusions and a second protrusion is located between any two adjacent first protrusions. Two recesses are connected between the second protrusion and the two adjacent first protrusions. A plurality of first grooves and second grooves are defined in each of two sides of the brake disk. Each second groove communicates with the first groove corresponding thereto so that rain drops, dust and debris from lining plates of calipers can be easily removed from the brake disk.

Abstract: A brake disk has a disk body. The disk body has two sides, an outer periphery, a central hole, multiple through holes and multiple curved grooves. The central hole is defined through the disk body. The through holes are defined through the disk body around the central hole. The curved grooves are defined respectively in the sides of the disk body and each groove has a first end extending to the outer periphery of the disk body and a second end extending to and communicating with one of the through holes.