Conventional　backlight　system　of　liguid　crystal　display　(LCD)　always　uses　side-in　light　emitting　diodes　(LEDs).　It　requires　that　the　thickness　of　the　light　guide　plate　should　be　larger　than　LED＇s　light-emitting　section　width.　To　solve　this　problem,　a　free-form　optical　coupling　module　for　side-LED　backlight　is　proposed,　which　includes　collimator　lens　and　a　free-form　reflector.　The　light　is　firstly　collected　and　collimated　by　immersing　collimator　lens,　and　then　reflected　and　gathered　into　the　LGP＇s　incident　surface.　By　using　Snell＇s　law,　differential　geometry　method　and　aplanatic　principle,　the　detailed　design　of　the　module　is　presented,　and　the　feasibility　is　shown　by　optical　simulation.　Simulation　results　show　that　by　choosing　0.4　mm×0.4　mm　LED　chip　as　the　light　source,　the　thickness　of　the　light　guide　plate　is　reduced　0.6　mm,　and　the　light　utilization　can　still　reach　96.23%.　Compared　with　the　conventional　structure,　the　light　utilization　increases　by　11.22%.　The　optical　coupling　module　can　realize　a　thinner　backlight　module　effectively,　and　simultaneously　help　to　restrain　the　hot　phenomenon.　©　2016,　Chinese　Laser　Press.　All　right　reserved.