A grating collimator comprising: a light guide configured to guide light as guided light at a non-zero propagation angle relative to a plane of a guiding surface of the light guide, the guided light having a propagation direction toward an output of the grating collimator; a light-recycling light source configured to provide light to the light guide and to recycle light received from the light guide, the light recycled by the light-recycling light source being configured to augment the provided light; and a diffraction grating coupler at the guiding surface of the light guide, the diffraction grating coupler being configured to diffractively redirect the light provided by the light-recycling light source into the light guide as the guided light at the non-zero propagation angle, and wherein the light-recycling light source comprises an optical emitter configured to emit light, an optical diffuser configured to diffuse light received from the light guide, and an optical reflector configured to reflect light diffused by the optical diffuser in a direction toward the light guide as reflected diffuse light, the light emitted by the optical emitter and the reflected diffuse light being provided in combination as the light provided to the light guide, and wherein the light-recycling light source further comprises a collimation layer configured to collimate the light provided to the light guide; wherein the optical emitter and the optical diffuser are located between the optical reflector and an output of the light-recycling source; and wherein either the optical emitter is located between the optical diffuser and the output of the light-recycling source, or the optical diffuser is located between the optical emitter and the output of the light recycling source. a light guide configured to guide light as guided light at a non-zero propagation angle relative to a plane of a guiding surface of the light guide, the guided light having a propagation direction toward an output of the grating collimator; a light-recycling light source configured to provide light to the light guide and to recycle light received from the light guide, the light recycled by the light-recycling light source being configured to augment the provided light; and a diffraction grating coupler at the guiding surface of the light guide, the diffraction grating coupler being configured to diffractively redirect the light provided by the light-recycling light source into the light guide as the guided light at the non-zero propagation angle, and wherein the light-recycling light source comprises an optical emitter configured to emit light, an optical diffuser configured to diffuse light received from the light guide, and an optical reflector configured to reflect light diffused by the optical diffuser in a direction toward the light guide as reflected diffuse light, the light emitted by the optical emitter and the reflected diffuse light being provided in combination as the light provided to the light guide, and wherein the light-recycling light source further comprises a collimation layer configured to collimate the light provided to the light guide; wherein the optical emitter and the optical diffuser are located between the optical reflector and an output of the light-recycling source; and wherein either the optical emitter is located between the optical diffuser and the output of the light-recycling source, or the optical diffuser is located between the optical emitter and the output of the light recycling source.