A new parallel photodisplacement technique that achieves extremely high-throughput imaging is proposed, and its practical realization is studied numerically. In this technique, a linear region of photothermal displacement is excited by use of a line-focusing intensity-modulated laser beam and detected with a parallel heterodyne interferometer in which a charge-coupled device linear image sensor is used. Because of the integration and sampling effects of the sensor, the interference light is spatiotemporally multiplexed. To extract the photodisplacement component from the multiplexed sensor signal, a scheme of phase-shifting light integration under an undersampling condition is proposed for parallel interferometry. The frequencies of several control signals, including the heterodyne beat signal, modulation signal, and sensor gate signal, are optimized so as to eliminate undesirable components, allowing only the displacement component to be extracted. Preliminary numerical simulation results show that the proposed technique has the potential to perform photodisplacement imaging more than 10,000 times faster than conventional photoacoustic microscopy.