微小激光加工区辐射测温系统的调焦

Focusing in Radiometric Temperature Measurement for Small Laser-Processed Region

将红外辐射测温系统用于半导体基片表面温度测量时,系统的调焦状况将影响测温结果的准确性。对这种影响进行了理论计算。结果表明,当被测高温区面积较大时,可以允许较大的调焦范围。但在激光诱导扩散等激光微细加工工艺中,曝光区直径仅数十微米量级,对系统的调焦提出了较高的要求。计算了在可见光波段和近红外波段两种情况下系统成像物镜的焦距。当成像物镜在波长为0.546μm时的焦距为30mm,并固定像距为196mm时,得到在波长为1.335μm时的物距比波长为0.546μm时大1.33mm。利用这个结果,结合在不同物距时系统对被测高温区进行扫描得到的温度分布,提出了调焦的方法。利用该方法,系统物距可调节到最佳物距为中心±0.05mm的范围内,满足了微小面元温度测量的要求。

The effects of focusing on the measurement precision of radiometric pyrometer have been analyzed. The results show that the larger of the high temperature region, the larger of the permissible focusing range. In experiment such as laser-induced diffusion, the diameter of the exposed region is only tens of microns. Therefore, the requirement of focusing is stringent. Then a focusing method was proposed to solve this problem. In the system used in the experiment, the image distance is fixed, and the focal length of the object lens is 30 mm at wavelength of 0.546 μm. The calculated results suggested that the change of focal lengths at different wavelengths causes the change of objective distances obviously. Based on these calculated results and the measured temperature distributions of the same object at different objective distances, the objective distance can be adjusted in the range of ± 0.05 mm around the ideal value, to meet the need of the radiometric temperature measurement for a small region.