The invention implements room temperature imaging of a photovoltaic diode image array operating in any spectral band (visible through extreme thermal). The invention also operates the photo diodes at zero bias voltage and thus eliminates 1/f (burst) noise and dark current. And the invention simplifies the electrical-mechanical interface between the readout integrated circuit (ROIC) and the photodetector array and minimizes the component count on the ROIC. These advantages are realized by multiplexing the photocurrents from each photodiode in the array according to an orthogonal or biorthogonal code set. The multiplexed current is supplied to an op amp such that zero bias is maintained for the photodetector array. The code set also allows the photocurrent generated by each photodiode to be recovered.