Design of the DICE LED head. The LED head is made of 8 aluminium blocks pierced with 24 holes corresponding to each of the 24 LED channels. Black masks are placed between each block to shape the beam and minimise the stray light. Each channel is equipped with an off-axis control photodiode that monitors the light delivered by the LED in real time. The photodiodes are placed on a board just behind the front face of the device. The LEDs are in thermal contact with an aluminium radiator, in order to dissipate waste heat and monitor the LED temperature. An additional central 25th channel delivers a pencil beam used to control the relative orientation of the device with respect to the telescope.