LED based projectors have numerous advantages compared to traditional projectors: they are more compact, exhibit a larger color gamut and a longer lifetime, the supply voltage is lower, the absence of ultra violet, infrared radiation and mercury vapour, etc. Furthermore LED��s can switch on and off very rapidly (possibility to pulse them) and they have a high dimming ratio that can be used to improve the contrast. However, there is also an important disadvantage: the optical power per unit of ��tendue (luminance) of an LED is significantly lower than that of e.g. an UHP-lamp. Because of this and the ��tendue limitation of the projector (small light valve, f-number projection lens), the projected flux on the screen will not be high. Despite this shortcoming, LED��s are still very interesting for low power applications because of their superior properties. However we have to collect the available light flux optimally and combine multiple LED��s with high luminance within the available system ��tendue. In this paper we have studied collection optics that collect the LED flux with high optical efficiency and collimation and reshape the spot in a uniform illuminated rectangle with the sizes of the micro display. We have designed ��Gradually Tapered Light Pipes��, ��Elliptical Reflectors�� and ��Parabolic Reflectors��. Furthermore we have combined many of these LED/collector combinations to get a high luminance illumination engine for LED based projectors.