Endpointing with determination of remaining distance

A method comprising:

• acquiring an image of a cut face at a first position on a sample;
• comparing the image with predetermined references from respective reference face positions;
• based on the comparing, determining a distance value from the first position to a target position;
• and
• outputting the distance value.

One or more computer-readable storage media having defined therein executable instructions which, when executed by one or more processors, actuate the one or more processors to:

• cause an ion beam to mill a sample to a cut face at a current position;
• acquire an image of the cut face from a scanning electron microscope (SEM);
• compare the image with predetermined references from respective reference face positions, to determine a distance value indicating a separation between the current position and a target position;
• if the current position is within a tolerance range relative to the target position, issuing a notification indicating that the target position has been reached;
• and
• otherwise, causing the ion beam to resume milling the sample.