3-D imaging systems can be used in a variety of applications such as in automobile, medicine, robot vision systems, security and so on. Recently many kinds of range finding methods have been proposed for 3-D imaging systems. This paper presents a new type of CMOS range image sensor based on the Time-of-Flight (TOF)principle with a spatial resolution of 336 × 252 (QVGA) and pixels of 15 × 15 μm2 size. A pixel structure of the sensor consists of single layer polysilicon gates on thick field oxide and has a function of background light induced charge reduction. The chip was fabricated in a 0.35 μm standard CMOS process with two poly and three metal layers. The presented sensor achieves a minimum range resolution of 2.8cm at framerate of 30fps and the resolution is improved to 4.2mm for 10 frames averaging, which corresponds to 3fps.
This paper presents a purely CMOS Active Pixel Sensor (APS) capable of time-of-flight (TOF) range imaging. The TOF sensor introduced is used to calculate range in the charge domain. To obtain high speed and highly efficient charge transfer that is important for TOF range imaging, a high gain inverting amplifier and two capacitors connected
alternatively to the feedback path are used. The high speed and highly efficient charge transfer using a high gain inverting amplifier in a negative feedback loop enables the TOF range imaging to be based on standard CMOS technology. Moreover, CMOS based amplifier circuits have matured and are relatively easy to design. The analysis of the APS together with simulation results suggests that the proposed technique can achieve a sufficient range resolution
of millimeter to centimeter depending on the maximum measured range.