We designed and tested a device to stimulate specifically one photoreceptor type, or a combination of some of them, of the human eye by using up to six primaries. The device produces a homogeneous light field over 40 degrees which is projected onto the retina through a Maxwellian view optical system. It avoids the use of an artificial pupil, does not need pupil dilation and retinal illumination can be easily controlled. We successfully tested it with four primaries for melanopsin and S-cone stimulation while maintaining other photoreceptors at a fixed level in photopic regime.