Improved wafer-scale testing of optoelectronic devices, such as CMOS image scan devices, is provided. A probe card includes an LED light source corresponding to each device under test in the wafer. The LED light sources provide light from a phosphor illuminated by the LED. A pinhole and lens arrangement is used to collimate the light provided to the devices under test. Uniformity of illumination can be provided by closed loop control of the LED light sources using internal optical signals as feedback signals, in combination with calibration data relating the optical signal values to emitted optical intensity. Uniformity of illumination can be further improved by providing a neutral density filter for each LED light source to improve uniformity from one source to another and/or to improve uniformity of the radiation pattern from each LED light source.