http://eia.udg.es/%7Eqsalvi/papers/2006-MJ.pdf

Review of CMOS image sensors

The pinned photodiode is the primary photodetector structure used in most CCD and CMOS image sensors. This paper reviews the development, physics, and technology of the pinned photodiode.

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A Review of the Pinned Photodiode for CCD and CMOS Image Sensors

This paper investigates terahertz detectors fabricated in a low-cost 130 nm silicon CMOS technology. We show that the detectors consisting of a nMOS field effect transistor as rectifying element and an integrated bow-tie coupling antenna achieve a record responsivity above 5 kV/W and a noise equivalent power below 10 pW/Hz(0.5) in the important atmospheric window around 300 GHz and at room temperature. We demonstrate furthermore that the same detectors are efficient for imaging in a very wide frequency range from ~0.27 THz up to 1.05 THz. These results pave the way towards high sensitivity focal plane arrays in silicon for terahertz imaging.

Broadband terahertz imaging with highly sensitive silicon CMOS detectors

Single-photon avalanche diode (SPAD) arrays are solid-state detectors that offer imaging capabilities at the level of individual photons, with unparalleled photon counting and time-resolved performance. This fascinating technology has progressed at a very fast pace in the past 15 years, since its inception in standard CMOS technology in 2003. A host of architectures have been investigated, ranging from simpler implementations, based solely on off-chip data processing, to progressively "smarter" sensors including on-chip, or even pixel level, time-stamping and processing capabilities. As the technology has matured, a range of biophotonics applications have been explored, including (endoscopic) FLIM, (multibeam multiphoton) FLIM-FRET, SPIM-FCS, super-resolution microscopy, time-resolved Raman spectroscopy, NIROT and PET. We will review some representative sensors and their corresponding applications, including the most relevant challenges faced by chip designers and end-users. Finally, we will provide an outlook on the future of this fascinating technology.

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Single-photon avalanche diode imagers in biophotonics: review and outlook

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).

A 0.13 μm CMOS System-on-Chip for a 512 × 424 Time-of-Flight Image Sensor With Multi-Frequency Photo-Demodulation up to 130 MHz and 2 GS/s ADC

A single-photon avalanche diode-based pixel array for the analysis of fluorescence phenomena is presented. Each 180 times 150 - mum2 pixel integrates a single photon detector combined with an active quenching circuit and a 17-bit digital events counter. On-chip master logic provides the digital control phases required by the pixel array with a full programmability of the main timing synchronisms. The pixel exhibits an average dark count rate of 3 kcps and a dynamic range of over 120-dB in time uncorrelated operation. A complete characterization of the single photon avalanche diode characteristics is reported. Time-resolved fluorescence measurements have been demonstrated by detecting the fluorescence decay of quantum-dot samples without the aid of any optical filters for excitation laser light cutoff.

Single-Photon Avalanche Diode CMOS Sensor for Time-Resolved Fluorescence Measurements

This paper presents the design and characterization of a lock-in pixel array based on a buried channel photo-detector aimed at time-of-flight range imaging. The proposed photo-demodulator has been integrated in a 10-μm pixel pitch with a fill factor of 24%, and is capable of a maximum demodulation frequency of 50 MHz with a contrast of 29.5%. The sensor has been fabricated in a 0.18-μm CMOS imaging technology and assembled in a range camera system setup. The system provides a stream of three-dimensional images at 5-20 fps on a 3-6 m range, with a linearity error lower than 0.7% and a repeatability of 5-16 cm, while the best achievable precision is 2.7 cm at a 50-MHz modulation frequency.

A Range Image Sensor Based on 10- $\mu{\hbox {m}}$ Lock-In Pixels in 0.18- $\mu$ m CMOS Imaging Technology

This paper presents the design and electro-optical test of a 160 × 120-pixels CMOS sensor specifically conceived for Time-Of-Flight 3D imaging. The in-pixel processing allows the implementation of Indirect Time-Of-Flight technique for distance measurement with reset noise removal through Correlated Double Sampling and embedded fixed-pattern noise reduction, whereas a fast readout operation allows the pixels values to be streamed out at a maximum rate of 10 MSample/s. The imager can operate as a fast 2D camera up to 458 fps, as a 3D camera up to 80 fps, or even coupling both operation modes. The chip has been fabricated using a standard 0.18 μm 1P4M 1.8 V CMOS technology with MIM capacitors. The resulting pixel has a pitch of 29.1 μm with a fill-factor of 34% and includes 66 transistors. Distance measurements up to 4.5 m have been performed with pulsed laser light, achieving a best precision of 10 cm at 1 m in real-time at 55 fps and 175 mA current consumption.

A 160 $\times$ 120-Pixels Range Camera With In-Pixel Correlated Double Sampling and Fixed-Pattern Noise Correction

Because we are living in a three-dimensional world, the usual intensity map provided by standard digital cameras is often not sufficient to build the sophisticated models required by systems capable of analyzing and interpreting their environment. A three-dimensional (3D) image sensor has great potential for improvement in many areas like ambient-assisted living, virtual reality, gaming, security and surveillance, etc., because it significantly increases the robustness of object classification and avoids time-consuming post-processing steps. Although the first commercial products are now available on the market, one of the main barriers to mass deployment of such 3D vision tools is the large pixel dimension, which ultimately reduces the sensor resolution and increases costs.

An 80×60 range image sensor based on 10µm 50MHz lock-in pixels in 0.18µm CMOS

The large interest shown in the field of terahertz detectors research by the scientific community brought to the
development of several kinds of devices based on different principles. Many, however, have some peculiar
characteristics that prevent their use in low-cost or compact equipment, because of cryogenic cooling, or the use of
exotic materials, etc.
Recently, approaches using field-effect transistors exploiting the oscillation of electron density (plasma waves) or the
phenomena known as "self-mixing" in RF modulators, allowed to foresee the possibility to employ standard CMOS
technologies to build such sensors.
In this work we analyze the behavior of this kind of detectors in order to understand how to design an optimized device
and then how to exploit it by proper readout. Optimized electromagnetic coupling to the detector has been implemented
using a dipole antenna. Electromagnetic simulations together with the developed model allowed calculating a projected
noise figure of the detector of 38ρW / √Hz. Two dedicated readout circuits have been designed, one intended to read the
detector as a current generator, while the other reads it as a voltage generator. The developed circuits have been designed
and sent for fabrication in a standard 0.35μm CMOS technology.

Lorenzo Gonzo

Papers

Single-Photon Avalanche Diode CMOS Sensor for Time-Resolved Fluorescence Measurements

A Range Image Sensor Based on 10- $\mu{\hbox {m}}$ Lock-In Pixels in 0.18- $\mu$ m CMOS Imaging Technology

A 160 $\times$ 120-Pixels Range Camera With In-Pixel Correlated Double Sampling and Fixed-Pattern Noise Correction

An 80×60 range image sensor based on 10µm 50MHz lock-in pixels in 0.18µm CMOS

Analysis and Design of a CMOS-based Terahertz Sensor and Readout