Homogenized LED-illumination using microlens arrays for a pocket-sized projector

We present an LED-based ultra-mini DMD projector with a size of 75 mm × 67 mm × 42 mm. A compact homogenizer consisting of a double-side mierolens array and two condensers was proposed to reduce the size of the pocket-sized projector. The homogenizer not only allowed for a reduction in the total track length of the system, but also reduced the angle of the rays emitted from the LED with the micro field lens array. The double-side well-aligned 124 × 146 mierolens array was fabricated using backside alignment and hot embossing techniques. The mierolens array was square-arranged and the fill-factor was extremely high. The uniformity and total throughput of this projector were higher than those of the current pocket-sized projectors. Moreover, the optical performances of the projector such as color difference and the LED alignment tolerance were also measured and discussed.