  The measurement rate of cameras that take spatially multiplexed measurements
by using spatial light modulators (SLM) is often limited by the switching speed
of the SLMs. This is especially true for single-pixel cameras where the
photodetector operates at a rate that is many orders-of-magnitude greater than
the SLM. We study the factors that determine the measurement rate for such
spatial multiplexing cameras (SMC) and show that increasing the number of
pixels in the device improves the measurement rate, but there is an optimum
number of pixels (typically, few thousands) beyond which the measurement rate
does not increase. This motivates the design of LiSens, a novel imaging
architecture, that replaces the photodetector in the single-pixel camera with a
1D linear array or a line-sensor. We illustrate the optical architecture
underlying LiSens, build a prototype, and demonstrate results of a range of
indoor and outdoor scenes. LiSens delivers on the promise of SMCs: imaging at a
megapixel resolution, at video rate, using an inexpensive low-resolution
sensor.
