基于SPAD值的植被“红边位置”确定方法探讨

以茶树、杨梅树和樟树为研究对象,每种树分3个部位随机采集50个叶片,应用线性内插方法、倒高斯方法、有理函数方法和拉格朗日等4种红边位置估算方法,分别计算了相关叶片的红边位置。同时将3种树叶的SPAD(叶绿素)值分别按照数值大小、树叶在树上的不同生长位置等为基数组成区间,再按照区间数据的不同组合共计分为25个区间段,然后运用SPSS软件,按照不同分划区间将红边位置与树叶的SPAD值进行双变量相关分析与计算。其结果表明无论怎样划分区间,依据SPAD值的红边位置以线性内插方法的吻合度最高,有理函数方法次之。     

烤烟鲜烟叶成熟度的量化

利用SPAD-502叶绿素计进行了连续两年的田间试验,研究了烤烟鲜烟叶的成熟度量化判别。结果表明不同成熟度鲜烟叶的差异主要表现在叶绿素含量上。选取与叶绿素含量关系密切的叶绿素相对值(SPAD)作为鲜烟叶成熟度的判别指标,并建立了烟叶成熟度的叶绿素计读数模型TMDSPADV,该模型的判别分类与先验的成熟度分类符合率为91%。因此,基于SPAD的成熟度TMDSPADV模型,可以进行量化的鲜烟叶成熟度判别。     

Compact SPAD pixels with fast and accurate photon counting in the analog domain

A compact pixel for single-photon detection in the analog domain is presented.The pixel integrates a single-photon avalanche diode (SPAD),a passive quenching & active recharging circuit (PQARC),and an analog counter for fast and accurate sensing and counting of photons.Fabricated in a standard 0.18μm CMOS technology,the simulated and experimental results reveal that the dead time of the PQARC is about 8 ns and the maximum photon-counting rate can reach 125 Mcps (counting per second).The analog counter can achieve an 8-bit counting range with a voltage step of 6.9 mV.The differential nonlinearity (DNL) and integral nonlinearity (INL) of the analog counter are within the ± 0.6 and ± 1.2 LSB,respectively,indicating high linearity of photon counting.Due to its simple circuit structure and compact layout configuration,the total area occupation of the presented pixel is about 1500μm2,leading to a high fill factor of 9.2％.The presented in-pixel front-end circuit is very suitable for the high-density array integration of SPAD sensors.     

SPAD值与鲜烟叶成熟度及烤后烟叶质量的关系

为探索快速、无损判断鲜烟叶成熟度的量化指标,以秦烟96为试验材料,应用叶绿素测定仪测定了各部位不同成熟度鲜烟叶SPAD值,并对相应烤后烟叶的经济性状、外观质量、化学成分、感官评吸质量进行了评价测定。结果表明,SPAD值能够较灵敏地区分烟叶黄绿面积10%~20%的差异,且与烟叶成熟度呈显著负相关关系,可较好地表示烟叶成熟度。综合烤后烟叶各项质量评价指标,下、中、上3个部位烟叶适宜成熟度对应的鲜烟叶SPAD值分别为8.6~11.4、17.9~18.6和13.2~20.3,SPAD值可作为成熟度的快速判定量化指标,用于指导烟叶适熟采收。     

Characterization of electronic displays using CMOS single‐photon avalanche diode image sensors

Advanced complementary metal‐oxide semiconductor‐compatible single‐photon avalanche diode array technology is progressing rapidly and is being deployed in a wide range of applications. We report for the first time the use of a complementary metal‐oxide semiconductor‐compatible single‐photon avalanche diode array to perform detailed optical measurements on pixels of an organic light‐emitting diode microdisplay at very high sampling rate, very low light level, and over a very wide dynamic range of luminance. This offers a clear demonstration of the huge potential of this single‐photon avalanche diode technology to reveal hitherto obscure details of the optical characteristics of individual and groups of organic light‐emitting diode pixels.     

（英）STI埋层的高光电流和低暗计数率单光子雪崩二极管

本文研究和分析了一种0.18-μm CMOS工艺单光子雪崩二极管（SPAD）,其结构能抑制过早的边缘击穿（PEB）,同时获得较大的光电流和低的暗计数率（DCR）。该SPAD由p-well/deep n-well的感光结,deep n-well向上扩散形成的区域和边缘Shallow Trench Isolation（STI）共同形成的保护环组成。通过测试确定了与光电流和暗率有关的STI层的大小。结果证明,在STI层与保护环之间的重叠区域为1-μm 时,SPAD的暗计数率和光电流最佳。此外,直径为10-μm的圆形SPAD器件的暗计数率为208Hz,且在波长为510nm时峰值光子探测概率为20.8%,此时具有低的暗计数率和高的探测效率以及宽的光谱响应特性。     

用于单光子TOF测量的时间-幅度变换器

基于新型共源共栅电流源的积分方法,设计了一种用于单光子飞行时间(TOF)测量的时间-幅度变换器(TAC).该方法有效简化了 TAC电路结构,减小了 TAC占用面积,显著提高了TOF的满量程范围(FSR).采用0.18 μm标准CMOS工艺设计.集成TAC的单光子探测器像素单元的填充因子可达到26.8％.后仿真结果表明,...     

基于SMIC 0.13μm CIS工艺的单光子TOF传感器像素设计

设计了一种基于SMIC 0.13μm CIS工艺的单光子飞行时间(TOF)传感器像素结构。针对传统单光子雪崩二极管(SPAD)结构的不足,采用p阱和STI共同作为保护环,避免器件提前发生边缘击穿从而减小器件面积,增加深n阱使有源区耗尽层变窄,从而降低雪崩击穿电压,增加硅外延层将器件的光谱响应峰值转移到所需要的光波长,以此提高器件对指定波长光的吸收能力。通过浮动SPAD阳极电压的方式,采用低压CMOS晶体管实现主动式淬灭电路从而快速地控制雪崩电流淬灭,以达到缩短死区时间的目的。通过SILVACO TCAD和Cadence IC设计套件对工艺、像素器件结构以及相关电路进行仿真,验证了该设计的可行性。     

Use of chlorophyll meter for nitrogen management in lowland rice

The chlorophyll meter (SPAD-502) can be used to diagnose the nitrogen (N) status of rice (Oryza sativa L.) to decide for fertilizer-N side-dressing. The objective of this study was to determine the relationships between SPAD meter readings, unadjusted and adjusted for specific leaf weight (SLW) and N on dry weight basis (Ndw), N on leaf area basis (Na) and yield. The correlation coefficients (r) between SPAD and Ndw ranged from 0.82 to 0.90; between SPAD and yield, from 0.75 to 0.90; and between SPAD/SLW and yield from 0.77 to 0.85 on pooling the data experiment-wise. The corresponding r values over all experiments were 0.87, 0.81 and 0.80, respectively. The results of better relationship between SPAD and Ndw; and between SPAD and yield in the late reproductive and early ripening phases allows prediction of plant N status based on direct SPAD meter readings. It is quick, simple and non-destructive unlike N prediction based on Kjeldahl procedure or SPAD/SLW.     

单光子雪崩二极管SPICE仿真模型的建立和应用

单光子雪崩二极管(SPAD)作为一种高效的光子探测器件被广泛应用于量子通信和三维成像等领域。在Cadence中建立了一个SPAD的Spice模型,通过Verilog-A语言,采用两个e指数函数的组合,以连续函数的方式描述了SPAD在盖革模式区等效电阻的动态变化。这两个e指数函数分别体现了高阻区和低阻区的等效电阻特性,解决了分段电阻模型仿真不收敛的问题。该Spice模型模拟了SPAD器件在“接收光子-雪崩产生脉冲-淬灭-复位”工作过程中的动态特性和SPAD从正偏到二次击穿的静态I-V特性。将其应用到4种不同淬灭电路的仿真中,验证了该模型的有效性和稳定性。