In this paper, a quasi-simultaneous multi-focus imaging technique named simulfocus imaging is reported. This technique was developed for measuring an entire object distributed in the depth direction beyond the depth of field (DOF) with high resolution in a single shot. Simulfocus imaging can acquire multiple focal planes in one shot by synchronizing a tunable acoustic gradient index (TAG) lens and a lock-in pixel image sensor. The TAG lens is a tunable-focus lens whose focal position can be changed at a high speed of several tens to several hundreds of kilohertz. The lock-in pixel image sensor is a special image sensor that can execute multiple exposures at an arbitrary timing during a single shooting. The sensor includes a number of photoelectron storage units in each pixel, and the units where the photoelectrons generated by each exposure are stored can be freely selected. Since an image can be acquired for a single storage unit, and the lock-in pixel image sensor has a number of storage units, the lock-in pixel image sensor can acquire multiple images in one shot. By assigning a specific exposure timing to each unit and synchronizing the exposure timing with the focus fluctuation of the TAG lens, it is possible to simultaneously acquire images in different focal planes. To evaluate the system, we conducted experiments to show the effectiveness of simulfocus imaging in microscope and telescope configurations. From the experimental results, it was confirmed that simulfocus was effective in both configurations.