menavy : Camera-phones - 一五一十部落| My1510

Camera-phones

 

摄像手机

 

Dotty but dashing

 

细微而有力

 

Nanotechnology could improve the quality of mobile-phone cameras

 

纳米技术提升摄像手机的图像品质

 

Apr 8th 2010 | From The Economist print edition

 

CAMERA-PHONES, a gimmick and a luxury a few years ago, have become ubiquitous. The International Telecommunications Union estimates that 4.6 billion mobile phones are in use at the moment. Of those, more than a billion are equipped with cameras, according to Tom Hausken, an analyst at Strategies Unlimited, a market research firm based in Mountain View, California. Dr Hausken estimates that some 800m camera-phones will be sold this year.

 

在几年前还仅仅是个嘘头同时也很昂贵的摄像手机,现在已经无处不在了。国际电信联盟估计现今有46亿部手提电话在使用中。当然,依Tom Hausken所言,其中的10亿部配备有摄像头,Tom Hausken(汤姆?豪斯肯)是位于加州山景城名为Strategies Unlimited的一家市场调查公司的分析师。Hausken(豪斯肯)博士估计,今年将有8亿部带摄像功能的手机售出。

 

Yet most of the photos taken with these phones will be grainy and of low resolution—fine for capturing the essence of a moment to send to friends and family, but not good enough to frame for the wall. The reason is that both camera and lens have to be small, to fit with all the other gubbins on a phone. A typical camera-phone is equipped with a one- or two-megapixel silicon-based camera chip that is about 8mm across. Phone cameras with up to five megapixels are becoming available, but InVisage, a small firm based in Menlo Park, California, hopes to leap from that to a photographically respectable 12 megapixels, without an increase in size or cost, by adding tiny crystals called quantum dots to the process.

 

然而,用这些手机拍摄的相片将是模糊的,分辨率也不高-影像品质可以满足在朋友和家人之间传送抓拍到的瞬间概况需要,但却不足以放到相框里挂在墙上。原因在于镜头和相机的体积为适应其他相机配置的需要而发生的减小。典型的摄像手机配备有100万或200万像素的硅基相机芯片,芯片尺寸约为8mm。可用的摄像手机摄像头的像素已经达到500万。然而,一家名为InVisage的小公司,该公司位于加州的门洛帕克。他们把名为quantum dots(量子点)的微晶体加入到制程中,在不增加体积或成本的前提下,将有望使现有手机相机的分辨率从现有水准跃升到相当逼真的1200万像素。

 

In a typical camera-phone, the image is focused by the lens onto a photosensitive silicon chip. Light striking this detector liberates electrons from some of the silicon atoms, producing an electrical signal that is converted by the chip’s electronics into a picture. Silicon, however, is not the best material for sensing light. Its physical properties (its narrow bandgap, in physics parlance) mean that it sometimes releases electrons even though no light has fallen on it, resulting in a noisy image. On top of that, the way chips are made requires the incoming light to pass through circuitry that has been deposited on to the silicon, reducing the level of illumination.

 

在典型的摄像手机中,影像由镜头聚焦到光敏硅芯片上。光线投射到探测元件上,然后部分硅原子释放电子,产生电信号,电信号被芯片上的电路转化为图像。硅并不是{zh0}的感光材料。它的物理特性(物理学术语是窄的能带隙)意味着即使没有光线投射到,它有时也会释放电子,结果导致图像噪音。此外,芯片的制作工艺也需要入射光线通过淀积在硅片上的电路,这使得光照度(光源照射在被照物体单位面积上的光通量)降低。

 

InVisage’s approach is to build the photodetector out of quantum dots on the surface of a chip, above the circuitry. A quantum dot is a semiconducting crystal just a few nanometres (billionths of a metre) across that can be engineered to absorb light of a particular colour by changing its size. The larger the dot, the redder the light it absorbs; the smaller, conversely, the bluer. Placing the quantum dots on top of the electronics means more pixels can be crammed into a given area and less incoming light is lost. Moreover, photodetectors based on quantum dots produce less noisy images, so the picture is sharper even if the number of pixels is not increased.

 

InVisage的方案是在芯片的表面也就是淀积的电路之上用quantum dots(量子点)建立光电转换元件。quantum dots(量子点)的尺寸仅为几个纳米(1纳米=10亿分之一米)的半导体晶体,在设计时可以通过改变尺寸来吸收不同波段的光。量子点的尺寸越大,吸收的红光越多,反之则为蓝光。在电路上设置量子点意味着更多的像素被聚焦到给定区域,也即更少的入射光损失。此外,基于量子点的光电转换元件的图像噪声很小,因此即使像素数目没有增大,而图像也能因此而更为锐利。

 

Edward Sargent, InVisage’s chief technology officer and a professor of optoelectronics at the University of Toronto, says his firm’s quantum dots are made of metal chalcogenides (which are a combination of metals such as zinc, indium, bismuth and lead with selenium, sulphur or tellurium). The dots are synthesised in a paint-like colloidal suspension which is then coated on to silicon wafers before they are cut up into chips.

 

Edward Sargent(爱德华?萨金特)是InVisage公司的首席技术主管,也是多伦多大学的光电子学教授。他说,他们公司的量子点材料是金属硫族化物(锌(Zn),铟(In),铋(Bi)和硒(Se),硫(S),碲(Te)的化合物)。量子点在类似油漆的悬浮胶体中合成,在硅晶圆切割成芯片前涂布在硅晶圆表面。

 

In addition to using them in camera-phones, Dr Sargent is working on employing quantum dots to make solar cells. He thinks cells made this way will be comparable in cost to organic solar cells (themselves much cheaper than traditional silicon ones) while being at least twice as efficient. But commercialisation of quantum-dot solar cells is still a few years away. For the moment, he is concentrating on camera-phones.

 

除了在摄像手机上的应用之外,Sargent(萨金特)博士还在研究量子点在太阳能电池方面的用途。他认为,在考虑到用量子点制备的电池和有机太阳能电池(有机太阳能电池制造成本比传统的硅电池更为低廉)相比,光电转换效率至少提高两倍时,这两者的费用接近。但是量子点太阳能电池的商业化仍然是几年以后的事情。目前,他关注的仍然是摄像手机。

 

 

Title of the illustration:Telling tales with tellurium

插图说明:碲(Te)叙说的xx



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