Trimodal microlens

Abstract

A trimodal microlens configuration is provided for the lenses in a microlens array utilized as a diffraction separator for generating separated bands of different color when the microlens array is provided with a collimated light source. To provide the trimodal functionality, each microlens is divided up into three segments, with the center segment providing a red, green, blue diffraction pattern, with the left segment providing a blue, red, green diffraction pattern, and with the right segment providing a green, blue, red diffraction pattern. This pattern is directed towards an adjacent liquid crystal color display in which its sub-pixels are arranged red, green, blue, with the green sub-pixel aligned with the center segment of the corresponding lens. The result of the trimodal lens is an overlapping of illumination for each of the sub-pixels in that the lens segment aligned with the particular colored sub-pixel provides one third of the light, with the other two thirds of the light being provided by adjacent segments of the lenses in the microlens array. The result of the overlapping illumination of the sub-pixels is that the viewing direction is symmetric about a normal to the array which makes the design of the diffuser used with liquid crystal displays quite simple and eliminates off-axis dead zones. The trimodal structure of the microlens also permits fabrication of a thin lens which minimizes the number of steps for a diffraction line and thus limits the number of etching steps required as well as making the etching process easier to control.