荧光增感屏的光学模糊效应研究

Investigation for Optical Blur in Phosphor Intensifying Screen

文章研究了可见光在稀土荧光增感屏Gd2O2S:Tb中的输运过程。运用蒙特卡罗(MC)方法计算了出射可见光的收集效率,增感屏的线扩展函数(LSF)和调制传递函数(MTF)。研究表明在增感屏内光源距离出射面越近、可见光的收集效率越高,造成的模糊越小;距离出射面越远、可见光子的收集效率越低,造成的模糊越大。增感屏越厚、线扩展函数的半高宽(FWHM)越大,模糊效应越严重;增感屏越薄、模糊越小,空间分辨率越高。增感屏厚度为0.5mm时,可见光的收集效率最大,造成的模糊大小为0.34mm,图像处理过程中必须考虑光学模糊的影响。

The transport of optical photons in the rare earth phosphor （Gd2O2 S： Tb） intensifying screen is investigated using Monte Carlo （MC） method. The optical collection efficiencies（OCE）, the line spread function （LSF） and the modulation transfer function （MTF） for screens with different thickness are calculated. It is found that OCE, LSF and MTF not only vary with the thickness of the intensifying screen, but also dependent on the depth of optical sources where photons started. It is quantitatively shown that most of photons emitted from the sources near the detection surface are collected , photons emitted from the sources far from the detection surface are less collected and thinner Screens have better spatial resolution. As the thickness of the screen is 0. 5 mm, OCE gets the maximum value and the quantity of the optical blur is about 0.34 mm which should be considered in the image processing.