IODP Expedition 402 X-ray image logger (XSCAN)

Digital x-ray images were taken of core section whole-rounds (WR) or split section-halfs (SHLF) by the X-ray Image Logger (XSCAN). Each x-ray image was flatfield corrected using a dark calibration image taken with the camera shutter closed and white calibration image taken with the shutter open. The raw image width in pixels was determined by the distance between the calibration right crop and left crop pixels. Multiple scans of the same sample may have been taken at various rotational offsets. The 0 degree position along the rotational axis is the camera oriented vertically facing downward with the sample positioned below. The camera rotates around a stationary sample holder, completes an entire scan, returns to the starting position, rotates, then completes another scan. Scan speed and exposure time are relative and automatically adjust as one or the other are altered prior to a scan. To improve constrast, after each scan pixel intensities are scaled by reshaping the image intensity histogram using the histogram expansion factor and histogram anchor parameters. The operator selects the region-of-interest (ROI) to encompass only the sample material.本数据集通过X射线成像记录仪（X-ray Image Logger, XSCAN）采集岩心完整切片（whole-rounds, WR）或劈开岩心半切片（split section-halfs, SHLF）的数字X射线图像。每幅X射线图像均采用相机快门关闭时采集的暗场校准图像与快门开启时采集的亮场校准图像进行平场校正。原始图像的像素宽度由校准右裁剪像素与左裁剪像素之间的距离确定。同一岩心样品可在不同旋转偏移量下开展多次扫描。旋转轴的0度位置定义为相机垂直朝下对准，样品置于相机下方。相机围绕固定样品架完成一整圈扫描后返回起始位置，再次旋转并进行下一次扫描。扫描速度与曝光时间为相对参数，扫描前调整其中任一参数时，另一参数将自动适配调整。为提升图像对比度，每次扫描完成后，将通过直方图扩展因子与直方图锚定参数重塑图像强度直方图，以此对像素强度进行缩放。操作人员可选取感兴趣区域（Region-of-Interest, ROI），使其仅覆盖样品本身。