Extreme-depth-of-focus imaging with a flat lens
Extreme-depth-of-focus imaging with a flat lens
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DOI：
10.1364/optica.384164
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发表时间：
2020-03-20
期刊：
影响因子：
10.4
通讯作者：
Menon, Rajesh
中科院分区：
文献类型：
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作者：
Banerji, Sourangsu;Meem, Monjurul;Menon, Rajesh
透镜执行从物体到图像平面的近似一对一映射。图像平面中的这种映射被维持在景深（或者如果对象在无限远处，则被称为焦深）内。当图像被大于景深的距离分开时，这需要重新聚焦透镜。这样的重新聚焦机构会增加成像系统的成本、复杂性和重量。在这里，我们表明，通过明智的多级衍射透镜（MDL）的设计，它是可能的，以大大提高超过4个数量级的焦深。使用这样的透镜，我们能够在我们的实验中保持对相距6米的物体的聚焦。具体地说，当用λ = 0.85 μ m的准直光照射时，MDL产生一束光束，该光束保持在5至1200 mm的焦点上。测量的聚焦光束的半峰全宽从6.6 μ m（距MDL 5 mm）变化到524 μ m（距MDL 1200 mm）。由于旁瓣得到很好的抑制，主瓣接近衍射极限，因此在整个焦距范围内以40度x 30度的水平x垂直视场成像是可能的。该演示为透镜设计开辟了一个新的方向，通过将焦平面中的相位视为自由参数，极限焦深成像成为可能。(C)根据OSA开放获取出版协议的条款，2020年美国光学学会
A lens performs an approximately one-to-one mapping from the object to the image plane. This mapping in the image plane is maintained within a depth of field (or referred to as depth of focus, if the object is at infinity). This necessitates refocusing of the lens when the images are separated by distances larger than the depth of field. Such refocusing mechanisms can increase the cost, complexity, and weight of imaging systems. Here we show that by judicious design of a multi-level diffractive lens (MDL) it is possible to drastically enhance the depth of focus by over 4 orders of magnitude. Using such a lens, we are able to maintain focus for objects that are separated by as large a distance as similar to 6m in our experiments. Specifically, when illuminated by collimated light at lambda = 0.85 mu m, the MDL produced a beam, which remained in focus from 5 to 1200 mm. The measured full width at half-maximum of the focused beam varied from 6.6 mu m(5 mm away from the MDL) to 524 mu m (1200 mm away from the MDL). Since the side lobes were well suppressed and the main lobe was close to the diffraction limit, imaging with a horizontal x vertical field of view of 40 degrees x 30 degrees over the entire focal range was possible. This demonstration opens up a new direction for lens design, where by treating the phase in the focal plane as a free parameter, extreme-depth-of-focus imaging becomes possible. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement