A CMOS image sensor which is capable to simultaneously sense an optical and an op-chip potential image was designed and fabricated. The sensor was designed with target applications to sense neural activities and DNA spots in on-chip configuration. We designed compatibly configured light sensing pixel and potential sensing pixel. The pixel size is 7.5 mum. A QCIF (176 times 144) dual image sensor was fabricated and characterized. The basic characteristics of the potential sensing pixel are discussed and dual imaging functions are demonstrated