Contrast has designed a lens for an electronic viewfinder (EVF) system. In this setup, an eMagin 100302-01 Organic Light Emitting Display (OLED) is used to form a tiny image, measuring just 9mm x 14mm. In order to view this image, a specialized viewfinder lens is needed. This lens must create an image for the viewer that appears to be at infinity, for relaxed-eye viewing. The image must be sharp over the entire display, free of any color defects, and must allow the user to place their eye 25mm away. In order to be truly useful, the lens must be designed so that the user's eye may move around slightly and still provide a crisp image. The area in which the user's eye may be placed for good viewing is called the "eyebox" of the EVF system.

 

The lens that Contrast has designed for this application is to be used with an eMagin SVGA OLED microdisplay (800x600 full-color pixels). Our lens provides an image to the viewer that measures 20-degrees from corner-to-corner. This is equivalent to watching an 87" display at a distance of only 10 feet away. The Contrast lens measures 1 inch in diameter and is made of two common plastic materials - acrylic and polycarbonate - cemented together. We took advantage of the material properties of these two plastics, specifically the fact that they have different refractive index and dispersion values, to practically eliminate any chromatic aberration in the lens system. The front and back surfaces are conic-section aspheres and the cemented surfaces are spheres. These lenses are extremely simple to produce and cost just pennies apiece in large, production quantities.

Using the photograph above as an image on the OLED display, our lens produces the image below, as seen by the viewer looking into the EVF. The image produced is clear and sharp and free of color defects. As seen through our EVF lens, the image measures 20-degrees from corner-to-corner.

EVF OUTPUT IMAGE

 

SUMMARY

We have shown an example of one of the many lens systems we designed for use in electronic viewfinder applications. Contact us to learn more about how Contrast Optical can solve your optical design problems.