A common problem with Fresnel lenses in display systems (especially fast display systems) is the presence of ghosting

The disadvantage is that it reduces the light transmittance.Because the highest principle in the application of back projection is to retain maximum brightness.

Another method to eliminate ghosting has been tested successfully.

This is especially evident when the lens focal length/diameter ratio is low, especially in high contrast images.In normal video applications, the Fresnel optical lens is reflected from the working face because the ghostly light is longer than the image light, because most of the ghostly light intensity propagates through the interference surface.It is then removed from the wrong direction through the working face or interference face, thus effectively eliminating ghosting.Although the Angle of interference can be designed so as not to interfere with the straight path of the light, the light reflected by the ghosting will inevitably reach the interference surface. A wideband anti-reflection (AR) coating is applied to the Fresnel lens structural surface.The normal internal reflection of a acrylic force ranges from 3,9 percent to more than 10 percent, reducing ghostly phenomena, a proportion of reflected light that is imperceptible.However, the application of the coating has not been completely successful, and the ghosting image is very obvious and uncomfortable. In addition, multiple reflections inside Fresnel lens may cause multiple shadows, because the Angle of the structural surface changes.One very efficient way is to dye the lens material Fresnel optical lens, Moir

The overlap occurs when different light intensity passes through the Fresnel lens structure.According to the Beer rule, the ghosting light is also thinner.When applied to a back projection display.This is not acceptable in back-projection applications, which look like a copy of the image as it is shifted across the screen, as if the image element is projected onto the screen.Absolutely unacceptable when text is displayed.It's going to be a very bad shadow.However, it is possible to blacken the Fresnel optical lens only by using black absorbent material.As shown in figure 7, the Fresnel lens and diffuser screen design must carefully consider the pitch matching of the system imaging element.

In principle, the cylindrical mirror fringe and Fresnel lens circular ring produce moire fringe.Increased transmission efficiency. However, as long as the display sharpness and high contrast (such as text display) are displayed, ghosting is a very annoying image-free Fresnel optical lens, since the functional Angle of the anti-reflection coating needs to change gradually with the Fresnel lens center out.One of the common problems with Fresnel lenses in display systems (especially fast display systems) is the presence of ghosting, which produces distinct moire streaks, which deepen the color of the interference surface. The screen is usually made up of Fresnel lenses and cylindrical mirrors with diffusion agents.Internal total reflection (TIR) occurs when passing through one side of the lens plane.Although it is difficult to do Fresnel optical lenses, so.

Ghosting is caused by internal reflection of Fresnel lens working face. There are many ways to reduce the visibility of ghosting image.In the next chapter, I will explain the disadvantages of Fresnel lens.