Adaptive High Dynamic Range for Time-of-Flight Cameras
Adaptive High Dynamic Range for Time-of-Flight Cameras
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DOI：
10.1109/tim.2014.2377993
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发表时间：
2015-07
影响因子：
5.6
通讯作者：
Miguel Heredia Conde;K. Hartmann;O. Loffeld
中科院分区：
文献类型：
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作者：
Miguel Heredia Conde;K. Hartmann;O. Loffeld
传统数码相机的动态范围有限是一个众所周知的问题。一种常见的解决方案是对使用不同曝光时间获取的几张图像应用高动态范围(HDR)技术。使用光子混频器件(PMD)的飞行时间(ToF)相机也不例外，因为其双像素的动态范围也是有限的。此外，在这种情况下，像素通道的饱和会导致错误的深度测量。一个合适的解决方案是由偏振模色散设计的抑制背景照明(SBI)系统。该系统实际上通过硬件扩展了摄像头的动态范围，但在启动时也会引入噪声。在本文中，我们提出了一种自适应HDR(AHDR)方法来解决ToF情况下的问题，它克服了系统有限的动态范围，允许在理论上无限的动态范围内进行传感，仅限于照明系统的功率和较高距离或较低照明强度时信噪比的衰减。我们的方法能够从场景的其余部分中检测和分割导致意外饱和的相关场景区域，即关闭的前景对象，并考虑它们来调整采集图像的曝光时间。结果表明，与单次采集相比，AHDR原始图像的细节损失减少，信噪比更高。这在保持高帧速率的同时，显著减少了深度误差，并有效地提高了关键区域的轴向分辨率。此外，还消除了与SBI相关的噪声。
The limited dynamic range of conventional digital cameras is a well-known problem. A common solution is to apply high-dynamic-range (HDR) techniques over several images acquired using different exposure times. Time-of-flight (ToF) cameras using a photonic mixer device (PMD) are not an exception, since the dynamic range of its dual pixels is also limited. Furthermore, in this case, the saturation of the pixel channels leads to wrong depth measurements. An appropriate solution is the suppression of background illumination (SBI) system designed by the PMD. This system actually extends the dynamic range of the camera by hardware, but it also introduces noise when activated. In this paper, we present an adaptive HDR (AHDR) solution to the problem for the ToF case that overcomes the limited dynamic range of the system, allowing sensing along a theoretically infinite dynamic range with the only limitations of the power of the illumination system and the decay of the SNR with higher distances or lower illumination intensities. Our method is able to detect and segment relevant scene regions responsible for unexpected saturation, i.e., close foreground objects, from the rest of the scene and adjust the exposure times of the acquired images considering them. The results show a reduction in detail losses and a higher SNR in the AHDR raw images, with respect to single acquisitions. This results in a dramatic depth error reduction and effective axial resolution improvement in critical areas, while keeping a high frame rate. In addition, the SBI-related noise is eliminated.