There are many places in the car that uses glass, which can be roughly divided into front windshield glass, rear windshield glass, door glass, triangular window glass, and sunroof glass. In particular, the laminated glass is composed of double-layer glass and three layers of PVB film.

    We know that PVB film has the following advantages:

    First of all, after bonding two layers of glass, it is safe, heat preservation, UV resistance, noise reduction, cold and heat resistance, moisture resistance, oil resistance, non-toxic, odorless, non-flammable, and various physical properties are relatively stable;

    Secondly, the optical properties are excellent, the refractive index is close to glass and other materials, high light transmission, no yellowing, etc.;

    In addition, the use process is relatively simple; the product price is not high. It is also used in automobiles because of its so many advantages, especially its physical properties of refraction and emission of light.

    In the car, the HUD is a complex optical system. Whether it is a W-shaped HUD or an ARHUD, it is directly projected on the front windshield of the car. The windshield has two sides, inside and outside, which both reflect light. The inner and outer surfaces of the ordinary car window glass are parallel. The same incident light will form two reflected rays on the glass. After they are simultaneously received by the human eye, a double image will be formed, and two graphics will appear. This phenomenon We call this ghosting.

    There are various solutions to eliminate the ghosting of the WHUD front windshield, but the most mature is to use the wedge-shaped PVB film laminated glass to adjust the reflected light. The PVB film between the two layers of glass inside and outside the ordinary front windshield is of uniform thickness. If this film is replaced with a wedge-shaped film, by adjusting the angle of the wedge-shaped film and the thickness of the glass, we can make the reflected light from the two surfaces keep getting closer. This eliminates ghosting effects. However, due to the special shape of the PVB film with a wedge-shaped cross-section, the manufacturing cost is relatively high, resulting in the price of the PVB film with a wedge-shaped cross-section is several times higher than that of an ordinary PVB film with a uniform thickness.