hwx168 发表于 2013-6-8 15:19:00

lux（照度）和cd/m2(亮度)的关系

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<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
color:#333333;mso-font-kerning:0pt" lang="EN-US">lux</span><span style="font-size:12.0pt;
font-family:宋体;mso-bidi-font-family:宋体;color:#333333;mso-font-kerning:0pt">（照度）和<span lang="EN-US">cd/m2(</span>亮度<span lang="EN-US">)</span>的关系<span lang="EN-US">L=R</span>×<span lang="EN-US">E()<br/>
</span>式中<span lang="EN-US">L</span>为亮度<span lang="EN-US">,R</span>为反射系数<span lang="EN-US">,E</span>为照度<span lang="EN-US">.<br/>
</span>国际单位制<span lang="EN-US">(SIE</span>单位制<span lang="EN-US">)</span>的光度单位<span lang="EN-US"><br/>
</span>名称符号单位英文名<span lang="EN-US"><br/>
</span>光强度<span lang="EN-US">I</span>坎德拉<span lang="EN-US">Candela(cd)<br/>
</span>光照度<span lang="EN-US">E</span>勒克斯<span lang="EN-US">Lux(lx)<br/>
</span>光亮度<span lang="EN-US">L</span>尼特<span lang="EN-US">Nit<br/>
</span>光通量φ流明<span lang="EN-US">Lumen(lm)</span></span></p>

<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
color:#333333;mso-font-kerning:0pt" lang="EN-US">1.</span><span style="font-size:12.0pt;
font-family:宋体;mso-bidi-font-family:宋体;color:#333333;mso-font-kerning:0pt">光强度 光强度<span lang="EN-US">(luminousintensity)</span>是光源在单位立体角内辐射的光通量<span lang="EN-US">,</span>以<span lang="EN-US">I</span>表示<span lang="EN-US">,</span>单位为坎德拉<span lang="EN-US">(candela,</span>简称<span lang="EN-US">cd).1</span>坎德拉表示在单位立体角内辐射出<span lang="EN-US">1</span>流明的光通量<span lang="EN-US">.</span></span></p>

<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
color:#333333;mso-font-kerning:0pt" lang="EN-US">2.</span><span style="font-size:12.0pt;
font-family:宋体;mso-bidi-font-family:宋体;color:#333333;mso-font-kerning:0pt">光通量 光通量<span lang="EN-US">(luminousflus)</span>是由光源向各个方向射出的光功率<span lang="EN-US">,</span>也即每一单位时间射出的光能量<span lang="EN-US">,</span>以φ表示<span lang="EN-US">,</span>单位为流明<span lang="EN-US">(lumen,</span>简称<span lang="EN-US">lm).</span></span></p>

<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
color:#333333;mso-font-kerning:0pt" lang="EN-US">3.</span><span style="font-size:12.0pt;
font-family:宋体;mso-bidi-font-family:宋体;color:#333333;mso-font-kerning:0pt">光照度光照度<span lang="EN-US">(illuminance)</span>是从光源照射到单位面积上的光通量<span lang="EN-US">,</span>以<span lang="EN-US">E</span>表示<span lang="EN-US">,</span>照度的单位为勒克斯<span lang="EN-US">(Lux,</span>简称<span lang="EN-US">lx).</span></span></p>

<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
color:#333333;mso-font-kerning:0pt" lang="EN-US">4.</span><span style="font-size:12.0pt;
font-family:宋体;mso-bidi-font-family:宋体;color:#333333;mso-font-kerning:0pt">反射系数
人们观看物体时<span lang="EN-US">,</span>总是要借助于反射光<span lang="EN-US">,</span>所以要经常用到反射系数的概念<span lang="EN-US">.</span>反射系数<span lang="EN-US">(reflectancefactor)</span>是某物体表面的流明数与入射到此表面的流明数之比<span lang="EN-US">,</span>以<span lang="EN-US">R</span>表示<span lang="EN-US">.</span></span></p>

<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
color:#333333;mso-font-kerning:0pt" lang="EN-US">5.</span><span style="font-size:12.0pt;
font-family:宋体;mso-bidi-font-family:宋体;color:#333333;mso-font-kerning:0pt">光亮度光亮度<span lang="EN-US">(luminance)</span>是指一个表面的明亮程度<span lang="EN-US">,</span>以<span lang="EN-US">L</span>表示<span lang="EN-US">,</span>即从一个表面反射出来的光通量<span lang="EN-US">.</span>不同物体对光有不同的反射系数或吸收系数<span lang="EN-US">.</span>光的强度可用照在平面上的光的总量来度量<span lang="EN-US">,</span>这叫入射光<span lang="EN-US">(inci-dentlight)</span>或照度<span lang="EN-US">(illuminance).</span>若用从平面反射到眼球中的光量来度量光的强度<span lang="EN-US">,</span>这种光称为反射光<span lang="EN-US">(reflectionlight)</span>或亮度<span lang="EN-US">(brightness).</span>例如<span lang="EN-US">,</span>一般白纸大约吸收入射光量的<span lang="EN-US">20%,</span>反射光量为<span lang="EN-US">80%;</span>黑纸只反射入射光量的<span lang="EN-US">3%.</span>所以<span lang="EN-US">,</span>白纸和黑纸在亮度上差异很大<span lang="EN-US">.</span></span></p>

<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;color:#333333;
mso-font-kerning:0pt">亮度和照度的关系如图<span lang="EN-US">6-2(a)</span>所示<span lang="EN-US">,</span>最常用的照度单位是呎烛光<span lang="EN-US">(footcandle).1</span>呎烛光是在距离标准烛光一英尺远的一平方英尺平面上接受的光通量<span lang="EN-US">.</span>如果按公制单位<span lang="EN-US">,</span>则以米为标准<span lang="EN-US">,</span>照度就用米烛光<span lang="EN-US">(metrecandle)</span>来表示<span lang="EN-US">,</span>即<span lang="EN-US">1</span>米烛光是距离标准烛光一米远的一平方米面积上的照度<span lang="EN-US">.1</span>米烛光等于<span lang="EN-US">0.0929</span>呎烛光<span lang="EN-US">.</span></span></p>

<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
color:#333333;mso-font-kerning:0pt" lang="EN-US"><img src="file:///C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\msohtml1\01\clip_image001.jpg" alt="lux（照度）和cd/m2（亮度）是怎么换算的" height="338" width="532"/></span></p>

<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;color:#333333;
mso-font-kerning:0pt">从图<span lang="EN-US">6-2</span>上<span lang="EN-US">,</span>我们不难理解亮度和照度之间的关系<span lang="EN-US">,</span>其关系为<span lang="EN-US">:</span></span></p>

<p class="MsoNormal" style="text-align:left;line-height:18.75pt;
mso-pagination:widow-orphan;background:white;word-break:break-all" align="left"><span style="font-size:12.0pt;font-family:宋体;mso-bidi-font-family:宋体;
color:#333333;mso-font-kerning:0pt" lang="EN-US">L=R</span><span style="font-size:12.0pt;
font-family:宋体;mso-bidi-font-family:宋体;color:#333333;mso-font-kerning:0pt">×<span lang="EN-US">E<br/>
</span>式中<span lang="EN-US">L</span>为亮度<span lang="EN-US">,R</span>为反射系数<span lang="EN-US">,E</span>为照度<span lang="EN-US">.<br/>
</span>因此<span lang="EN-US">,</span>当我们知道一个物体表面的反射系数及其表面的照度时<span lang="EN-US">,</span>便可推算出它的亮度<span lang="EN-US">.<br/>
<br/>
</span>亮度也有几种度量单位<span lang="EN-US">.</span>亮度的单位是用一种理想化了的标准状态来定义的<span lang="EN-US">(</span>如图<span lang="EN-US">6-2b).</span>以一支标准蜡烛当作光源<span lang="EN-US">,</span>放在一个半径为<span lang="EN-US">1</span>公尺的球体的中心位置<span lang="EN-US">.</span>假设这个蜡烛会均匀发散它的全部光线<span lang="EN-US">,</span>则落在球体内表面一平方公尺表面积上的所有光量为<span lang="EN-US">1</span>个流明<span lang="EN-US">(lumen).</span>实际应用中<span lang="EN-US">,</span>亮度单位用流明太小了<span lang="EN-US">,</span>所以通常取其十倍的单位——毫朗伯<span lang="EN-US">(millilambert)</span>来表示<span lang="EN-US">.</span>比毫朗伯稍大的单位是呎朗伯<span lang="EN-US">(footlambert),1</span>毫朗伯等于<span lang="EN-US">0.929</span>呎朗伯<span lang="EN-US">.</span>英国标准的呎朗伯是用光源的烛光数<span lang="EN-US">,</span>从光源到表面积的英尺数和表面的反射率来规定的<span lang="EN-US">.</span>在有些国家<span lang="EN-US">,</span>普遍使用的是米制单位<span lang="EN-US">,</span>是以毫朗伯为基础的<span lang="EN-US">.</span>光亮度的单位还有<span lang="EN-US">:</span>坎德拉<span lang="EN-US">/</span>平方米<span lang="EN-US">(</span>即尼特<span lang="EN-US">,Nit=1cd/m2)</span>等<span lang="EN-US">.<a href="http://www.cnhwx.com">红外线</a></span></span></p>

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