Borehole Imaging – Optical Scanner – Overview.
The optical scanner is a high resolution CMOS camera borehole imaging probe which is commonly run in combination with an acoustic scanner for detailed, high resolution images of the borehole through 360°. Ideal and commonly used for structural studies and geotechnical investigations but has applications in casing inspection and insitu stress analysis.
The optical scanner is a borehole imaging probe which is capable of a high resolution, true colour image thus creating an image of the full 360 degree borehole wall. The high resolution CMS camera system is focussed through a prism to all 360° slices of the borehole wall to be recorded during a survey.
A single, true colour image is produced from the survey.
The optical scanner operates in air filled and/or clear fluid filled conditions. Ideally the probe should be centrallised in the borehole to avoid unwanted shadow effects.
Of importance for the optical scanner is the marker position which is established during manufacture and/or servicing. The marker position acts as the reference point for all subsequent image orientation. Internal magnetometers and accelerometers, used to probe and image orientation are factory calibrated.
Verification, performed using jigs or project boreholes where a known reference or structure orientation is available, focus on confirmation of the marker position and the functionality of the internal magnetometers and accelerometers.
There are two main areas of image data processing:
Orientating, filtering and de-spiking the images, as well depth validation.
Picking and classifying or structures through to true structure dip and dip direction generation.