An extremely high-sensitivity image sensor has been developed with a combination of an active-matrix high-efficiency electron emission device (HEED) array and a high-gain avalanche rushing amorphous photoconductor (HARP) target. Following the description of the requirements for the use of the electron emitter as an image-sensing probe, the characteristics of a fabricated 640 x 480 pixel active-matrix HEED image sensor with a HARP target are presented by image-pickup experiments under a dark condition. The emission current density of the experimental HEED under an active-matrix drive was 4 A/cm(2) corresponding to a practical level. A clear image observed in the prototype compact camera demonstrates that the surface-emitting HEED is useful for image sensing based on HARP with high sensitivity and sufficient definition. c 2008 American Vacuum Society.