Torcal-Milla Francisco Jose, Sanchez-Brea Luis Miguel
Appl Opt. 2017 Apr 20;56(12):3628-3633. doi: 10.1364/AO.56.003628.
Highly collimated beams are required in numerous applications and techniques. Different methods have been proposed for collimating monochromatic point light sources during the recent years. In this work, we analyze how a finite size and polychromatic light source can be collimated using only one diffraction grating and a CMOS camera placed after the source and the collimating lens. For this, we determine the period of the fringes diffracted by the grating and compare it with the period of the grating. Analytical equations are obtained to predict the amplitude of the fringes and their period. Since self-images disappear for finite size polychromatic sources at long distances from the grating, the period has to be measured close to the grating. In addition, we give an analytical equation to determine the error in the positioning of the source in terms of the source size and the setup parameters. Finally, we experimentally corroborate the obtained analytical formalism using a white LED of size s=0.6 mm collimated by a lens with focal length f=25 mm, and a Ronchi binary grating of period d=250 μm. In this case, we achieve an experimental error in the positioning of the source with respect to the focal plane of the lens of δz=92 μm.
在众多应用和技术中都需要高度准直的光束。近年来，人们提出了各种用于准直单色点光源的方法。在这项工作中，我们分析了如何仅使用一个衍射光栅以及置于光源和准直透镜之后的互补金属氧化物半导体（CMOS）相机来准直有限尺寸的多色光源。为此，我们确定了由光栅衍射的条纹周期，并将其与光栅周期进行比较。获得了用于预测条纹幅度及其周期的解析方程。由于对于有限尺寸的多色光源，在离光栅较远的距离处自成像会消失，所以必须在靠近光栅的位置测量周期。此外，我们给出了一个解析方程，用于根据光源尺寸和装置参数确定光源定位的误差。最后，我们使用尺寸为s = 0.6毫米的白色发光二极管（LED），通过焦距f = 25毫米的透镜以及周期d = 250微米的朗奇二元光栅进行实验，证实了所得到的解析形式。在这种情况下，我们实现了光源相对于透镜焦平面定位的实验误差为δz = 92微米。
