We introduce a 512 × 424 time-of-flight (TOF) depth image sensor designed in a TSMC 0.13 μm LP 1P5M CMOS process, suitable for use in Microsoft Kinect for XBOX ONE. The 10 μm × 10 μm pixel incorporates a TOF detector that operates using the quantum efficiency modulation (QEM) technique at high modulation frequencies of up to 130 MHz, achieves a modulation contrast of 67% at 50 MHz and a responsivity of 0.14 A/W at 860 nm. The TOF sensor includes a 2 GS/s 10 bit signal path, which is used for the high ADC bandwidth requirements of the system that requires many ADC conversions per frame. The chip also comprises a clock generation circuit featuring a programmable phase and frequency clock generator with 312.5-ps phase step resolution derived from a 1.6 GHz oscillator. An integrated shutter engine and a programmable digital micro-sequencer allows an extremely flexible multi-gain/multi-shutter and multi-frequency/multi-phase operation. All chip data is transferred using two 4-lane MIPI D-PHY interfaces with a total of 8 Gb/s input/output bandwidth. The reported experimental results demonstrate a wide depth range of operation (0.8-4.2 m), small accuracy error ( 1%), very low depth uncertainty ( 0.5% of actual distance), and very high dynamic range ( 64 dB).

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Interest in 3D depth cameras has been piqued by the release of the Kinect motion sensor for the Xbox 360 gaming console [1,2,3]. This paper presents the pixel and 2GS/s signal paths in a state-of-the-art Time-of-Flight (ToF) sensor suitable for use in the latest Kinect sensor for Xbox One. ToF cameras determine the distance to objects by measuring the round trip travel time of an amplitudemodulated light from the source to the target and back to the camera at each pixel. ToF technology provides an accurate high pixel resolution, low motion blur, wide field of view (FoV), high dynamic range depth image as well as an ambient light invariant brightness image (active IR) that meets the highest quality requirements for 3D motion detection.Depth and active IR images are produced by combining multiple images that are captured at different phase relationships of the clocks provided to the light source and pixel array. The captures are taken in rapid temporal succession to avoid motion blur. In addition, high differential dynamic range is necessary to simultaneously render high-reflectivity objects near the camera and lowreflectivity objects far from the camera. High dynamic range is realized by allowing each pixel to independently select the best shutter time (multi-shutter) and the best amplifier gain setting (multi-gain) at each capture.Due to the multiple captures that need to be taken in rapid succession and the high dynamic range requirements, ADC conversion must be performed many times per capture and due to noise considerations cannot happen simultaneously with integration. Therefore a high-bandwidth 2GS/s 10b, column-parallel ADC is employed. Noise and mismatches are cancelled by using a completely differential design from pixel through ADC.The ToF chip includes a 512×424 pixel array with 10μm pixel pitch fabricated in a standard TSMC 0.13μm CMOS LP 1P5M process. The 60% fill-factor (effective with μLens) pixel achieves a modulation contrast (MC) of 67% (measured at 50MHz) and a responsivity of 0.14A/W at 860nm. The chip can operate at high modulation frequencies of up to 130MHz to extract maximum depth quality while minimizing system light-source power. The schematic of the fully differential pixel design with a simplified detector plan is shown in Fig. 7.6.

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