Abstract: A light-folding element includes an object-side surface, an image-side surface, a reflection surface and a connection surface. The reflection surface is configured to reflect imaging light passing through the object-side surface to the image-side surface. The connection surface is connected to the object-side, image-side and reflection surfaces. The light-folding element has a recessed structure located at the connection surface. The recessed structure is recessed from the connection surface an includes a top end portion, a bottom end portion and a tapered portion located between the top end and bottom end portions. The top end portion is located at an edge of the connection surface. The tapered portion has two tapered edges located on the connection surface. The tapered edges are connected to the top end and bottom end portions. A width of the tapered portion decreases in a direction from the top end portion towards the bottom end portion.

Abstract: A multi-shifting shift register is adapted for outputting a selected address signal to a memory unit, and includes a control circuit for outputting a number (i) of shift signals and a timing pulse signal. One of the shift signals is at an enabled state and the other ones of the shift signals are at a disabled state during each cycle of the timing pulse signal. A multi-shifting circuit includes a number (N), which is larger than the number (i), of cascaded register units, each of which has a flip-flop that has an input end, and an output end for generating an address signal, and a selector that has the number (i) of select inputs for receiving the number (i) of the shift signals respectively from the control circuit, the number (i) of address signal inputs, and an output. The output end of the flip-flop is connected to a first one of the address signal inputs of the selector.