Abstract: A compact size light engine apparatus is disclosed, comprising at least a wedged dichroic mirror or a dichroic X-plate/cube to combine multiple RGB LEDs, and a folded light path assembly with a folding mirror or a right-angle prism for a miniaturized light engine system. Furthermore, the compact size light engine apparatus may comprise at least a long red wavelength light source with peak wavelength over 630 nm. A 2-channel/3-channel/4-channel compact size light engine configuration is disclosed that comprise at least one red light source, one blue light source, and one green light source, combined by a wedged dichroic mirror or a dichroic X-plate/cube into co-axis light path without Etendue increase and illuminate digital mirror device (DMD) micro-display and afterwards project the image from the micro-display onto the screen through projection lens.