Methods and apparatus for pupil detection are described. First light is emitted from a first light source at a first illumination angle relative to the axis of a detector. Second light is emitted from a second light source at a second illumination angle relative to the axis. The first light and the second light can have substantially equal intensities. The second illumination angle is greater than the first illumination angle. Reflected first light and reflected second light are received at the detector. The difference between the reflected first light and the reflected second light can be determined. The difference can be used to detect the pupils of a subject's eyes.