Query: NIR SPAD

title: Active Reset for the N+P Single Ended SPAD Used in the NIR LiDAR Receivers
abstract: A monolithic resistorless circuit has been designed for active reset of the N<sup>/sup>P single ended (common anode) single photon avalanche diode (SPAD) This type of SPAD has enhanced the photon detection efficiency in the near infrared (NIR) region relatively to the P<sup>/sup>N (two ended) SPAD. Due to this fact, the N<sup>/sup>P SPAD is a better candidate for the light detection and range (LiDAR) working in the NIR region. The circuit is fabricated in a standard 0.18 <inline formula> <tex math notation="LaTeX"\mu \text{m} /tex math>/inline formula> CMOS image sensor process. The dead time after each photon detection is adjustable; the minimum measured value is 4 ns. The maximum photon count rate corresponding to this dead time is <inline formula> <tex math notation="LaTeX"{2.5}\cdot {10}{8} /tex math>/inline formula> photons/s. This circuit guarantees precise repeatable response, short and well controlled dead time, and after pulsing effect reduction. All these are essential for many SPAD applications and crucial for increasing the saturation level of the silicon photo multiplier (SiPM) based LiDAR systems working in strong background light conditions on sunny day.

title: Silicon hybrid SPAD with high NIR sensitivity for TOF applications
abstract: This paper proposes a single photon avalanche diode (SPAD) sensor array comprised of a hybrid structure which can maximize the fill factor of the active area and be compatible with the other detector layer optimized for various demands. In order to implement the hybrid structure, a 100mm pitch through silicon via (TSV) implementation method has been developed to access the back surface of the sensor layer. The achieved fill factor is up to 60% thus, photon detection efficiency can be reached 35% A 32x32 SPAD array and a dedicated application specific IC has been designed. We have proved the concept structure can work successfully through the characterization of the hybridized chip. On the other hand, we realized multi event detection capability should be considered when we apply the photon counting image sensor to a time of flight application in high background intensity, and the new concept of a SiPM based pixel structure has been considered. In order to prove the concept, fundamental experiments have been performed by using the new SiPMs which have extended sensitivity in the near infrared region, and a current mode front end ROIC which can mark a time of arrival and distinguish a photon quantity. A walk error has been studied and found the plot of the time of arrival and the photon quantity can be utilized for the measurement compensation.

title: 5.7 A 256x256 40nm/90nm CMOS 3D Stacked 120dB Dynamic Range Reconfigurable Time Resolved SPAD Imager
abstract: Light Detection and Ranging (LIDAR) applications pose extremely challenging dynamic range (DR) requirements on optical time of flight (ToF) receivers due to laser returns affected by the inverse square law over 2 3 decades of distance, diverse target reflectivity, and high solar background  Integrated CMOS SPADs have a native DR exceeding 140dB, typically extending from the noise floor of few cps to 100's Mcps peak rate. To deliver this DR to downstream DSP, large SPAD time resolved imaging arrays must count and time billions of single photon events per second demanding massively parallel on chip pixel processing to achieve practical I/O power consumption and data rates. Hybrid Cu Cu bonding offers a mass manufacturable platform to implement these sensors by providing high fill factor SPADs optimised for NIR stacked on dense nanoscale digital processors  Stacked sensor architectures involving pixel level histogramming, on chip peak detection and TDC/processor resource sharing are now being investigated [3 5]

title: Application of SPAD and Vis/NIR Spectroscopy to Estimation Nitrogen Status of Oilseed Rape Plant
abstract: The estimation of nitrogen status non destructively in oilseed rape was performed using spectral reflectance with visible and near infrared reflectance spectroscopy, and SPAD values of the oilseed rape leaves of 30 plots were measured by a SPAD 502 chlorophyll meter, and the research was carried out at experiment field in Zhejiang University during growing season from 2007 to 2008. The SPAD 502 chlorophyll meter was applied to investigate the distribution rule of chlorophyll concentration in the oilseed rape. Regression model between the spectral reflectance and SPAD value was built by partial least squares (PLS) The correlation coefficient (r) root mean square error of prediction (RMSEP) and bias in prediction set were 0.9368, 3.4992 and 1.834e 07. The correlation between the first derivative of spectral reflectance of oilseed rape leaves and SPAD value were analyzed, and the results showed that good correlation coefficient was obtained in the range from 510 to 640 nm and 685 to 720 nm, and the maximum value for correlation coefficient was at the wavelength 707 nm. The linearity equation between the red edge index and chlorophyll concentration was also analyzed, with the correlation coefficient of 0.986. It is concluded that Vis/NIRS combined SPAD 502 chlorophyll meter was a promising technique to monitor nitrogen status in oilseed rape.

title: NITROGEN ESTIMATION OF OILSEED RAPE USING SPAD AND VIS/NIR SPECTROSCOPY
abstract: The estimation of nitrogen status, non destructively, in oilseed rape was performed using spectral reflectance with visible and near infrared reflectance spectroscopy (Vis/NIRS) and SPAD values of the oilseed rape leaves of 30 plots were measured by a SPAD 502 chlorophyll meter, and the research was carried out at experiment field in the Zhejiang University during growing season from 2007 to 2008. The SPAD 502 chlorophyll meter was applied to investigate the distribution rule of chlorophyll concentration in the oilseed rape. Regression model between the spectral reflectance and chlorophyll concentration (SPAD value) was built by partial least squares (PLS) the correlation coefficient (r) root mean square error of prediction (RMSEP) and bias in prediction set were 0.9368, 3.4992 and 1.834e 07. Correlation between the first derivative of spectral reflectance of oilseed rape leaves and chlorophyll concentration (SPAD value) were analyzed, and the results showed that good correlation coefficient was obtained in the range from 510 to 640 nm and 685 to 720 nm, and the maximum value for correlation coefficient was at the wavelength 707 nm. The linearity equation between the red edge index and chlorophyll concentration (SPAD value) was also analyzed, with the correlation coefficient of 0.986. It is concluded that Vis/NIRS combined SPAD 502 chlorophyll meter was a promising technique to monitor nitrogen status in oilseed rape.

title: Time Domain Near Infrared Optical Tomography with Time of Flight SPAD Camera: The New Generation
abstract: We present the first laboratory results of the new generation of time domain near infrared optical tomography setup, which is based on a time of flight 32x32 SPAD camera with high photon detection probability in the NIR range.

title: Fully Depleted SiPMs Optimized for Automotive NIR ToF in 180nm Technology
abstract: In recent years, Single Photon Avalanche photo Diodes (SPADs) are getting a lot of attention in the fast growing applications and markets of Time of Flight (ToF) and 3D imaging. In particular, in the automotive market, where many Light Imaging, Detection, and Ranging (LiDAR) systems use SPAD as their sensor. A special device, based on SPAD technology, is specifically attractive for LiDAR systems, namely the Silicon Photo Multiplier (SiPM) This is a parallel connected array of SPADs which gives the combination of sensitivity, down to a very few photons, and excellent time resolution, providing information about the number of simultaneously impinging photons. This is in contrast to the classical SPAD, which has only a digital "zero/one" behavior. Automotive LiDARs and other ToF applications uses near Infra Red (NIR) illumination and thus a good Photon Detection Efficiency (PDE) is required for these wavelengths, usually 905nm or even 940nm. In order to have good PDE in the NIR regime, one needs a thick absorbing region in the SPAD device. This is very challenging for CMOS based SPAD devices, where the multiplication depth is dictated by ion implants. Furthermore, the deep absorption usually generates electrons that reach the multiplication region by slow diffusion mechanism and creates a lag that deteriorates the ToF performance. We present in this paper the optimization of such an SiPM by means of layout and process.

title: Ground Truthing and Physiological Validation of Vis NIR Spectral Indices for Early Diagnosis of Nitrogen Deficiency in cv. Barbera (Vitis vinifera L. Grapevines
abstract: Several narrow or broadband spectral indices can be calculated at varying spatial and spectral resolution, which can then be correlated with the physiological and nutritional status of the leaves. In a three year trial carried out on fruiting, potted cv. Barbera grapevines subjected to full (N+ or no (N0) nitrogen supply, seasonal evolution of different leaf spectral indices were correlated with non destructive chlorophyll readings (Minolta SPAD meter) leaf gas exchange, and vine performance. Throughout the entire trial, N starvation resulted in greater than proportional limitation of vine yield as compared to vegetative growth (55% compared to 26% less than values measured on N+ Indices calculated within the red edge spectral domain had highest sensitivity to relative change between N+ and N0, also indicating that the promptest response was recorded at the median shoot zone level. Twelve broadband indices were linearly correlated with leaf blade N concentration at veraison, indicating that N values 1.8% of dry matter identify a limiting N status. Any of these indices collected at the leaf level can be reliably used as a non destructive predictor of N availability, albeit due to significant between year variation in their absolute values at a given N level, readings should always include a well supplied N treatment.

title: Chlorophyll Content Detection of Field Maize Using RGB NIR Camera
abstract: In order to rapidly detect the chlorophyll content in the field, the RGB NIR camera was used to collect the multi spectral image of maize canopy. The SPAD value was measured at the same time to indicate the chlorophyll content. The multi spectral images were processed. Considering the features of multi spectral images, after image median filtering and segmentation to remove the background effect by field soil, dry straw and weeds, 15 image parameters were extracted including the average grey value of each channel (AR, AG, AB and ANIR) the vegetation indices (ANDVI, ANDGI, ARVI, ADVI) vegetation coverage index (VCI) hue average(AH) and image texture parameters (energy (AASM) moment of inertia (ACON) correlation (ACOR) entropy (AEN) and inverse difference moment (AL) The sensitive parameters were selected by correlation coefficient analysis and RF method. There were 4 and 8 parameters, respectively. After modeling, the LS SVM model built by RF selected parameters showed better detection accuracy with Rc2=0.87 and Rv2=0.74. It could be used for rapid and non destructive detection of the chlorophyll content for field maize.

title: Silicon photomultipliers and single photon avalanche diodes with enhanced NIR detection efficiency at FBK
abstract: Silicon photomultipliers (SiPMs) have recently obtained a growing attention as an alternative to traditional photomultiplier tubes for detecting low photon fluxes. SiPMs are currently used in many medical and physics applications, but they are also emerging as a valuable option in single photon or few photon applications, like light detection and ranging, optical spectroscopy, and bio medical instrumentation. During last years at Fondazione Bruno Kessler (Trento, Italy) we developed two different SiPM technologies, with peak sensitivity in the green wavelength region and in the blue one. Recently, we also started to develop a new technology with increased sensitivity in the red and near infra red (NIR) wavelength region. This development poses several technological and design challenges since the single photon avalanche diode (SPAD) internal structure has to be modified in order to collect carriers generated by photons absorbed at a depth of several microns. In this paper we will describe the first NIR SiPMs and NIR SPADs produced in FBK and we will present and discuss their experimental characterization. These devices show promising performance: SiPMs with 35 m m cell reach a PDE of about 18% at 850 nm and of more than 10% at 900 nm. These values are mainly limited by the SPAD border effect, which will be discussed in the paper by means of TCAD simulations. The full potentiality of these devices, in terms of PDE, will also be demonstrated by PDE measurements on a single SPAD with shielded active area border.