Reply (reverse) reflector is composed of many replies (reverse) reflective optical cell array structure, retro-reflective optical unit mainly beads and cubic corner cube into two categories. Retro-reflectors for motor vehicles is composed of many cubic corner cube array composed of manufacturing an optical plastic injection. The so-called cube corner cube (Cube Comer Retroreflector, abbreviated as CCR) that is a reflection of three prism reflecting surface at right angles to each other, also known as the three sides of a right angle cone prism, corner cube, pyramid prism. It corresponds to a corner of a cube cut from (Figure 4.2.1, b shown). Right triangle OAB, OBC, OCA three reflecting surfaces, the bottom surface of an equilateral triangle ABC is cone angle (also called string side) and later for the sake of the narrative unity, will be renamed the front underside, and its location is also on the most front. The light incident from the front, followed by the three reflecting surfaces, and then exit from the front. The outgoing light and the incident light and the reverse parallel with a certain offset between e, as shown in Figure 4.2.1 (c) in FIG. If a beam of light incident on the front is full, every outgoing light, although offset, but together with the outgoing beam on the incident beam completely overlap but do not see the offset. It should be noted that in the cube corner cube, only after three secondary reflection of light reflecting surfaces to form reverse (reply) reflection.

    From the above description we can see, in front of the entrance pupil of the incident beam (△ ABC). Stare out the front of the inverted (△ A'B'C '), as shown in Figure 4.2.2. Effective outgoing beam of light through the hole for a regular hexagon DEFUHI. In the incident ray other than the regular hexagon, without the third reflection on the surface of three times to meet with the front, through the front of reflected refracted away from the third reflecting surface, can not return along the direction of incident light, resulting in loss of light energy, reducing the reflectivity. Since only two-thirds of the area of ​​a regular hexagon in front of the area, so there will be a third of the light energy loss. Retro-reflector (Figure 4.2.3 (α)) with this cube corner cube array composed of light through theeffective area of ​​the reply and only two-thirds of the entire surface area of the front reflector.

    In order to reduce the loss of incident light energy, usually two ways to make a cube corner cube Ke and sleep completely overlap:
    (1) The front of the three corners of an equilateral triangle (Figure 4.2.2 44DI, 4BEF, 4CGH) cut into the front of a regular hexagon DEFGHI cube corner cube, its reflective surfaces were pentagon OJDEK, OKFGL, OLHU. This cube retro-reflector array consisting of corner cube as shown in Figure 4.2.3 (b).
    (2) by the three reflecting surfaces triangle OAB, OBC, OCA expanded square OAC'B, OBA'C, OCB'A. This cube retro-reflector array composed of corner cube in Figure 4.2.3 (c) below.

    Retro-reflectors are used on the vehicle is mainly in the form of two arrays. Since the square reflecting surface reflecting surface is easy to manufacture than the pentagon, so the use of more.

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