雷射光由高折射率介質(密介質)進入到低折射率介質(疏介質)，當折射角等於900時，有一對應臨界角(qc)，由此臨界角即可求得待測材料折射率。此時，密介質為待測材料，疏介質為空氣。此種量測技術，求得材料折射率準確度可達小數點以下第二位。由實驗得知，綠光雷射所測得材料折射率皆較紅光雷射為大，上述驗證可見光為正常色散。另外溫度也是影響材料折射率因素之一，溫度越高，折射率越小。溶液濃度也是影響折射率另一因素，材料折射率會隨濃度增加而增加。本系統是以氦氖雷射當主光源，其他紅光及綠光半導體雷射當副光源，再以光敏電阻當光檢測器，如此即可製作成低成本高精度之折射率測量儀。

When the laser light enters from the high refractive index medium (dense medium) to the low refractive index medium (coarse medium), have a corresponding critical angle, use this critical angle to obtain the unknown material refractive index. Now, the dense medium is the testing material, and the coarse medium is the air. This kind of measuring technology, obtains the unknown material refractive index accuracy to reach below the decimal point second. We know the green laser measures the
material refractive index to be bigger than the red laser; the above confirming visible light is the normal dispersion. Moreover the temperature will also affect the material refractive index, the temperature is higher, and the refractive index will be smaller. The solution concentration will also affect the refractive index; the refractive index will increase along with the solution concentration. The systems is using He-Ne laser as main source, the other sources such as red and green laser diodes as assistant sources.And use photo-resister as receiver, and so, the systems can reach low cost high precision of the
refractive index meter.