Ultra-Bright Heads-Up Displays Using a Method of Projected Color Images by Combination of LEDs and Polymer-Dispersed Liquid Crystals

A heads-up display (HUD) commonly uses liquid crystal technology to generate images. However, the intensity of the light decreases significantly due to passing through polarizers. Therefore, a polarizer-free display is a superior approach to utilize light more efficiently. We demonstrate the feasibility of using polymer dispersed liquid crystal (PDLC), which consists of polymer and liquid crystal, as an optical shutter to fabricate a simple see-through projected display device. The unique electro-optical characteristics of PDLC make it suitable to define the projected image shape. In our device, we used a 36 watts collimated light emitting diode as a backlight source so that the projected image can also be seen clearly under daylight. Since PDLC does not require/utilize polarizers, it achieved high light efficiency ( ~ 70%). In this paper, we showed promising results of projected images with various colors (red, green, and blue) that can be applied to see-through projected displays. From our experimental results, the see-through projected display device by PDLC can achieve a contrast ratio of 1000:1 and the response time is approximately 15 ms. The driving voltage is less than 25 V and brightness is over 3000 nit.