Color range images captured by a four-phase CMOS image sensor

As 3-D displays become more common, the demand for 3-D-related products is rapidly increased. Three-dimensional image sensors based on the time-of-flight (TOF) technique are one of these products and are applied to many applications. In this paper, a new pixel based on the continuous-wave modulation method was proposed to measure the TOF and was embedded in a test complementary metaloxidesemiconductor (CMOS) image sensor. Compared with other range imagers, no complex control signals, high operating voltage, or multilevel control voltages are needed in this pixel. The chip, with 92 × 30 pixels, was fabricated using the Taiwan Semiconductor Manufacturing Company's 0.18-μm CMOS standard process, and a time-switched color measurement was applied to this rangefinder system. A pulse train of red, green, and blue lights is emitted sequentially from a light-emitting diode array. The distance is easily calculated from the phase differences, and the color information is estimated using the difference in reflection coefficients under a different light. The measured distance and color are compared with the actual distance and color-corrected images. A color range image with a distance error of 3.56 cm and an L^*a^*b color difference of 40.23 can be observed. This rangefinder system provides a new perspective to capturing a colored range image.