03 imaging sensors 成像传感器

imaging sensors 成像传感器

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摘要：

  1. 人眼结构：杆状细胞感觉强度(夜视)，锥状细胞感觉颜色(白天视力)

CCD Camera

CCD: Charge-coupled device (semiconductor) 电荷耦合器件(半导体)
Single IC sensor device 单集成电路传感器装置
Consists of an array of photosensitive cells 由一系列光敏细胞组成
Each cell produces an electric current dependent on the incident light falling on it. 每个电池产生的电流依赖于入射光
Video signal output 视频信号的输出
Array of small fixed elements 小的固定元素的数组
Can read faster than TV rates 读入速度比电视信号快
Can add refracting elements to get color in 2x2 neighborhoods 可以添加折射元素计算出2x2邻域的颜色
8-bit intensity common

Blooming Problem with Arrays 阵列的晕染问题

  1. Difficult to insulate adjacent sensing elements. 难以隔离相邻的传感元件
  2. Charge often leaks from hot cells to neighbors, making bright regions larger. 充电经常从热电池漏到邻近的电池，使明亮的区域变大

8-bit intensity can be clipped 8bit可以被剪切

In A/D conversion the bright values were clipped to lower values. 在A/D转换中，亮值被剪切为较低的值

Lens distortion distorts image 透镜畸变使图像失真

Zoom lenses often show severe distortion. 变焦镜头经常出现严重失真

Orbiting satellite scanner

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Human eye 人眼结构

100M sensing elements in retina 视网膜中的100万个传感元件

图！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！

Rods（杆） sense intensity (night vision) 杆状细胞感觉强度(夜视)
Cones（锥） sense color (daytime vision) 锥状细胞感觉颜色(白天视力)
Nonuniform distribution of sensing elements 传感元件分布不均匀
Fovea has tightly packed elements, more cones in small region – high resolution 中心凹内的元素排列紧密，小区域内的视锥细胞较多，分辨率较高
Periphery has more rods – more sensitive to motion 外围有更多的杆状细胞-更敏感的运动
Focal length is about 20mm 焦距约为20毫米
Pupil/iris controls light entry and amount of light 瞳孔/虹膜控制光的进入和光的量
Eye scans, or saccades to image details on fovea 眼睛通过扫描中央凹来获得图像的细节
100M sensing cells funnel to 1M optic nerve connections to the brain 100兆（百万）个传感细胞汇集到1百万个连接大脑的视神经

Surface data (2.5D) 2.5D成像

Surface data (2.5D) sensed by structured light sensor 2.5D成像由结构光传感器感知 Projector projects plane of light on object 投影仪把光投射到物体上
Camera sees bright points along an imaging ray 照相机沿着成象射线看到亮点
Compute 3D surface point via line-plane intersection 通过线-面相交计算三维曲面点
Only visible surface shape extracted (hence, the term 2.5D) 只提取可见的表面形状(所以叫做2.5D)

Magnetic Resonance Imaging (MRI) 磁共振成像

Sense density of certain chemistry
S slices x R rows x C columns
Volume element (voxel) about 2mm per side
Could be uneven in different dimensions
A graph is shaded 2D image created by “volume rendering” a 3D volume: darkness codes depth