Gerald Zach

A 16

A time-of-flight depth sensor is presented employing a correlation based concept. The pixels are able to suppress contributions of ambient light up to 150 klx autonomously and directly in the electronic circuits consuming only 2 μA, each. All 16 × 16 pixels capture the depth information simultaneously at maximally 16 frames per second using an external A/D converter (ADC). Additionally, an embedded 12-bit ADC can be used for converting the analog output values of the pixels to the digital domain at lower frame rates. Distance measurements in a range of 0-3.2 m show standard deviations in the centimeter range and a linearity error within -1/+2 cm. The influence of extraneous light is expressed as a relative distance error which is also in the centimeter range. A complete impression of the sensor system is given by discussing the pixel circuits, the ADC design, the design of the modulated light source providing 0.9 W optical power in the near infrared, and the auxiliary setup including an FPGA board. Additionally, a sensor model is provided to predict the measurement error due to stochastic sources. Three-dimensional snapshots as well as a comparison with state-of-the-art sensors and products complete the paper.

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The integration of the fast and efficient silicon p-i-n photodetectors is presented. The suggested advanced p-i-n design speeds up the detectors, avoiding slow carrier diffusion: the p+ anode is arranged in a thick n

16 Pixel Distance Sensor With In-Pixel Circuitry That Tolerates 150 klx of Ambient Light

low-doped intrinsic region placed inside an n+ -doped region. Two p-i-n detector concepts are compared: a plain p-i-n photodiode and a structured p-i-n fingerdiode that is optimized for shorter wavelengths. Due to this setup and a thick intrinsic region, a responsivity of R=0.25 A/W (0.42 A/W) {0.27 A/W} at a wavelength of lambda=410 nm (660 nm) {850 nm} for the p-i-n fingerdiode, a bandwidth up to f3dB=3GHz and a dark current of Idark=0.36 pA at Vp-i-n=17 V for the p-i-n photodiode could be reached. As a system-on-chip (SOC), BiCMOS circuitry is combined with the integrated photodetector to an optoelectronic integrated circuit (OEIC) as shown on an exemplary application of a 6-Gb/s monolithic optical receiver. The chips are realized in a modified 0.5 mum BiCMOS process

Integrated BiCMOS p-i-n Photodetectors With High Bandwidth and High Responsivity

This work covers a correlation-based, optical time-of-flight matrix range sensor which is able to suppress ambient light up to 150klx full-electronically and autonomously in each single pixel. The CMOS-compatible sensor features 16×16 pixels and permits distance measurements with a standard deviation of 1cm (5cm) up to 1m (3.2m), while the linearity error is within ±2cm for the entire measurement range within a measurement time of 50ms per distance point. A 0.9W LED source is used to illuminate the field of view with near-infrared light, which is modulated at 10MHz. In this design, the current consumption could be reduced from 100µA to 2µA per pixel, while increasing the distance measurement performance at the same time.

Extraneous-light resistant multipixel range sensor based on a low-power correlating pixel-circuit

Within this work an integrated range finding single pixel sensor manufactured in a standard 90nm CMOS technology is presented. The sensor works on the time-of-flight principle obtaining the distance information out of the correlated sent and received signals. The implementation of a range-finding sensor in 90nm technology is using the most advanced process for a distance sensor up to now based on the bridge circuit. Background light suppression is inherently provided in the pixel sensor. The pixel facilitates a high fill factor accounting to 90% at an area of 50 × 64 µm² and has a power consumption of 2 µW. Measurement results show a standard deviation of 2 cm at 1.2 m covering the range from 0.2 to 3.2 m at 120 klx background illumination.

Range finding sensor in 90nm CMOS with bridge correlator based background light suppression

Real-time 3D imaging has reached a state of development where several fields of application are possible, such as factory automation, consumer electronics, security, and robotics. The first commercial products have already been launched, or will be available soon. Accuracies in the centimeter range or even below, low cost, and robustness to disturbances in realistic indoor and outdoor environments are the key performance demands for these sensors, which are mostly based on the time-of-flight (TOF) principle either in pulsed or continuous-wave (CW) mode.

A 2×32 range-finding sensor array with pixel-inherent suppression of ambient light up to 120klx

Within this work a 28 pixels line sensor for distance measurement applications is presented based on the time-of-flight principle and the double-correlator circuit concept. An on-chip oscillator block generates 15-phase steps of the fundamental 10 MHz clock with σ = 1.28 %, which is necessary for calculating the triangular correlation function out of which the distance information is obtained. Measurement results in a range up to 3 m with a standard deviation ≥ 3.5 cm are achieved. The pixel autonomous background light suppression is capable of managing background illumination > 100 kLux. A smart bus concept reduces the number of control signals to the pixels and guarantees 80 dB attenuation from the oscillator signals to the analog differential outputs of the chip. The line sensor was realized in a single-chip solution embodying the silicon PIN photodiode detectors.

Smart distance measurement line sensor with background light suppression and on-chip phase generation

A 32 pixel line sensor is presented for range finding applications of non-cooperative targets based on the time-of-flight (TOF) principle of modulated light. The sensor is realized as an optoelectronic integrated circuit (OEIC) containing the PIN photodiode with a high bandwidth of >1 GHz together with a high responsivity of 0.45 A/W at 660 nm and a novel, quasi differential correlating active integrator circuit in each pixel. Distance information is gained in every pixel, integrating the weak received signal correlated with the transmitted modulation signal. The single pixel achieves a minimum standard deviation of 8.5 mm in a measurement range of 1.5 m - 3.2 m with an optical transmission power of 1.5 mW and a plain white paper target. Exemplarily a scanned 3D depth image of the university logo demonstrates the potential of the sensor. Single pixel size is 210 mum times 105 mum with an optical fill factor of 45%. The sensor chip was fabricated in a 0.6 mum BiCMOS process including PIN-technology.

Distance Measurement Line Sensor with PIN Photodiodes

The presented distance measurement sensor is implemented as an opto-electronic integrated circuit (OEIC) in a modified 0.6 mum BiCMOS technology. The measurement principle is based on the determination of the phase shift between a received optical signal and an electrical modulation signal. The newly developed double-cathode photodetector (DCP) performing the opto-electronic correlation and the all-passive read-out circuit are implemented on a single chip. By using the DCP the fill factor is greatly improved compared to K. Oberhauser et al (2006). For an optical active area of Apd = 115times120 mum2 a very high fill factor of etafill = 67 % is reached. The sensor is capable of measuring distances up to sd = 6.2 m with an optical transmitted power of Popt = 1.2 mW at a wavelength of lambda = 650 nm.

Monolythically Integrated Optical Distance Measurement Sensor with Double-Cathode Photodetector

In this work an integrated Time-Of-Flight (TOF) based range finding single pixel sensor in 90nm CMOS is presented. The sensor exploits a PN photodiode for the signal detection, achieving the pixel size of 80 × 86.5 µm2 at the fill factor of ∼ 93%. Measurement results show a standard deviation of 2.5 cm at 1 m and less than 8 cm for distances up to 3.2 m. Ambient light suppression is accomplished inherently in pixel through the bridge correlator circuit approach, whereby the measured distance changes only in the range +3.2cm to −1.2cm for applied DC light up to 180 klx. An inverter feedback ensures a long integration of the modulated signal canceling out the influence of the photodiode capacitance. Due to very small structure sizes, the circuit itself occupies an area of only 13 × 17 µm2 and together with a shrunken photodiode high count multipixel sensors can be realized.