A light emitting module comprising a light mixing chamber comprising: - a base having a reflective inner surface, - at least one partly light transmissive side wall extending from the base towards an at least partly light transmissive, semi-reflective light exit window arranged opposite to the base, and - a carrier for carrying at least one light emitting diode and being positioned at a distance from a nearest portion of the at least one partly light transmissive side wall, wherein - the at least one light emitting diode is arranged to emit source light in a main direction different from 90 degrees with respect to the semi-reflective light exit window and in the main direction away from the nearest portion of the at least one partly light transmissive side wall for enabling subsequent mixing of the source light within the mixing chamber to generate mixed light, and - wherein the semi-reflective light exit window and the at least one partly light transmissive side wall are arranged for coupling out source light and mixed light as emitted light (106"), - wherein the mixing chamber has an inner mixing chamber width in the direction along the base between the nearest portion of the at least one partly light transmissive side wall and an opposite portion of the at least one partly light transmissive side wall being positioned opposite to the nearest portion of the at least one partly light transmissive side wall, and an inner mixing chamber height spacing the base and the semi-reflective light exit window, wherein the inner mixing chamber width and the inner mixing chamber height have an aspect ratio in the range of 4 to 15, - characterized in that the semi-reflective light exit window has a reflectivity in the range from 30 to 80% for source light and mixed light, and - in that the distance from the at least one light emitting diode to the nearest portion of the at least one partly light transmissive side wall is in the range from 5 to 30 % of the inner mixing chamber width. - a base having a reflective inner surface, - at least one partly light transmissive side wall extending from the base towards an at least partly light transmissive, semi-reflective light exit window arranged opposite to the base, and - a carrier for carrying at least one light emitting diode and being positioned at a distance from a nearest portion of the at least one partly light transmissive side wall, wherein - the at least one light emitting diode is arranged to emit source light in a main direction different from 90 degrees with respect to the semi-reflective light exit window and in the main direction away from the nearest portion of the at least one partly light transmissive side wall for enabling subsequent mixing of the source light within the mixing chamber to generate mixed light, and - wherein the semi-reflective light exit window and the at least one partly light transmissive side wall are arranged for coupling out source light and mixed light as emitted light (106"), - wherein the mixing chamber has an inner mixing chamber width in the direction along the base between the nearest portion of the at least one partly light transmissive side wall and an opposite portion of the at least one partly light transmissive side wall being positioned opposite to the nearest portion of the at least one partly light transmissive side wall, and an inner mixing chamber height spacing the base and the semi-reflective light exit window, wherein the inner mixing chamber width and the inner mixing chamber height have an aspect ratio in the range of 4 to 15, - characterized in that the semi-reflective light exit window has a reflectivity in the range from 30 to 80% for source light and mixed light, and - in that the distance from the at least one light emitting diode to the nearest portion of the at least one partly light transmissive side wall is in the range from 5 to 30 % of the inner mixing chamber width.