A light engine for a three-dimensional printer includes a plurality of light emitting diodes (LEDs) arranged into respective groups, each respective group of LEDs including one or more LEDs, e.g., LEDs of different wavelengths. Corresponding to each respective LED group is a respective light pipe for receiving outputs of radiation from each the LEDs of the respective group and providing an output of the light pipe, and a respective telecentric optical system for collimating the output of the respective light pipe to provide a collimated output of the respective LED group. The respective telecentric optical system of each LED group includes a plurality of lenses, an absorber for constraining high angle rays of electromagnetic radiation propagating from the respective light pipe, and a crosstalk filter arranged to prevent rays of electromagnetic radiation propagating between adjacent ones of the light pipes of the light engine through the telecentric optical system.