For detected file system to ascertain file system readability select Reconstruct the file system box in the Advanced scan parameters setting dialog.
For Unknown file system the task is activated automatically.
Together with Reconstruct the file system box you may optionally activate deleted files search tasks.
Virtually reconstructed file system appears as Reconstructed file system tree directory in File system explorer view.
More detailed information is in Part VII, 1. General scan parameters setting and Part VII, 2. Advanced scan parameters setting.