Yoon Sowon J, Bajcsy Peter, Litorja Maritoni, Filliben James J
Information Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, USA, 20899.
Dakota Consulting Inc., Silver Spring, MD, USA, 20910.
Opt Eng. 2018 Sep;57(9). doi: 10.1117/1.oe.57.9.093101.
Light field cameras are an emerging imaging device for acquiring 3-D information of a scene by capturing a field of light rays traveling in space. As light field cameras become portable, hand-held, and affordable, their potential as a 3-D measurement instrument is growing in many applications, including 3-D evidence imaging in crime scene investigations. We evaluated the lateral resolution of commercially available light field cameras, which is one of the fundamental specifications of imaging instruments. For the evaluation of the camera's lateral resolution, we imaged Siemens stars under various imaging configurations and experimental conditions, including changes in distance between the camera and the resolution target plate, illumination, zoom level, location of the Siemens star in the camera's field-of-view, and cameras of the same model. The analysis results from a full factorial experiment showed that (i) when a lower zoom level of the camera was used, the lateral resolution tended not to be affected by distance; however, when a higher zoom level was used, it tended to decrease significantly with respect to the distance, (ii) the center region of the camera's field-of-view provided a better lateral resolution than the peripheral regions, (iii) a higher zoom level yielded a higher lateral resolution, (iv) the two cameras of the same model used in the study did not show a significant difference in the lateral resolution, and (v) changes in illumination did not affect the lateral resolution of the cameras.
光场相机是一种新兴的成像设备，通过捕捉在空间中传播的光线场来获取场景的三维信息。随着光场相机变得便携、可手持且价格亲民，其作为三维测量仪器在许多应用中的潜力不断增长，包括犯罪现场调查中的三维证据成像。我们评估了市售光场相机的横向分辨率，这是成像仪器的基本规格之一。为了评估相机的横向分辨率，我们在各种成像配置和实验条件下对西门子星进行成像，这些条件包括相机与分辨率目标板之间的距离变化、光照、变焦级别、西门子星在相机视场中的位置以及同一型号的相机。全因子实验的分析结果表明：（i）当使用相机的较低变焦级别时，横向分辨率往往不受距离影响；然而，当使用较高变焦级别时，横向分辨率往往会随着距离显著降低，（ii）相机视场的中心区域比周边区域提供更好的横向分辨率，（iii）较高的变焦级别产生较高的横向分辨率，（iv）本研究中使用的同一型号的两台相机在横向分辨率上没有显示出显著差异，并且（v）光照变化不会影响相机的横向分辨率。
