FEMTO-ST Institute, Université Bourgogne Franche-Comté, CNRS, 25000 Besançon, France.
Sección Física, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Apartado 1761, Lima, Peru.
Sensors (Basel). 2018 Jun 22;18(7):2005. doi: 10.3390/s18072005.
Standard computer vision methods are usually based on powerful contact-less measurement approaches but applications, especially at the micro-scale, are restricted by finite depth-of-field and fixed working distance of imaging devices. Digital holography is a lensless, indirect imaging method recording the optical wave diffracted by the object onto the image sensor. The object is reconstructed numerically by propagating the recorded wavefront backward. The object distance becomes a computation parameter that can be chosen arbitrarily and adjusted to match the object position. No refractive lens is used and usual depth-of-field and working distance limitations are replaced by less restrictive ones tied to the laser-source coherence-length and to the size and resolution of the camera sensor. This paper applies digital holography to artificial visual in-plane position sensing with an extra-large range-to-resolution ratio. The object is made of a pseudoperiodic pattern allowing a subpixel resolution as well as a supra field-of-observation displacement range. We demonstrate an in-plane resolution of 50 nm and 0.002deg. in , and θ respectively, over a working distance range of more than 15 cm. The allowed workspace extends over 12×10×150mm3. Digital holography extends the field of application of computer vision by allowing an extra-large range of working distances inaccessible to refractive imaging systems.
标准的计算机视觉方法通常基于强大的非接触式测量方法，但应用，特别是在微观尺度上，受到有限景深和成像设备固定工作距离的限制。数字全息术是一种无透镜、间接成像方法，记录由物体衍射的光学波到图像传感器上。通过将记录的波前向后传播，对物体进行数值重建。物距成为一个可任意选择和调整以匹配物体位置的计算参数。不使用折射透镜，通常的景深和工作距离限制被替换为与激光源相干长度以及相机传感器的大小和分辨率相关的限制更小的限制。本文将数字全息术应用于具有超大的分辨率与景深比的人工视觉平面内位置感应。物体由一个伪周期图案组成，允许亚像素分辨率以及超过观察场的位移范围。我们演示了在超过 15cm 的工作距离范围内，在 θ、φ 和 ψ 方向上分别具有 50nm 和 0.002deg. 的平面内分辨率。允许的工作空间扩展到 12×10×150mm3。数字全息术通过允许大的工作距离范围，扩展了计算机视觉的应用范围，这些范围对于折射成像系统来说是无法到达的。
