Microscopy Focus Stacks for Coating Defects: Preserve the Original Frames

A focus-stacked microscope image can combine details from several depths into one sharp view that never existed as a single optical plane. It is useful for presenting a coating defect, but should not erase the evidence needed to understand where each feature appeared.

Separate the overview from the evidence

Microscope depth of field limits how much vertical structure appears sharp at once. Leica’s microscopy guidance explains how digital methods can extend the apparent in-focus region. Preserve the original frames as well as the composite: a presentation image and a measurement record serve different purposes.

Start with an overview locating the defect on the panel. Add a lower-magnification view connecting the marked location to the microscopic field. Without that chain, a close-up may be impossible to relocate after cleaning or further testing.

Record how the stack was made

Field	Purpose
Sample and location	Connect the image to the affected part
Objective and camera setup	Identify the optical configuration
Scale calibration	Support lateral measurements
Frame sequence and focus spacing	Preserve the sampled focal range
Software and settings	Make processing reviewable
Original frames	Allow ambiguous edges to be checked

Keep depth claims within the method

A feature becoming sharp at a different focus setting is an observation, not automatically a calibrated coating-thickness measurement. Optical geometry, transparent layers and instrument mechanics can affect interpretation. A quantitative thickness or depth claim requires an appropriate validated method and reference.

Similarly, a composite alone cannot establish whether a particle is embedded or resting on a surface. Preserve the sample, examine the focal sequence and identify what additional evidence would distinguish the possibilities. Avoid destructive follow-up until the relevant observations are recorded.

Check the composite against its source frames

Reflected highlights, low-contrast regions and steep features can produce misleading boundaries during stacking. If a line appears only in the composite, mark it as uncertain rather than using it as a precise defect perimeter.

For example, a bright ring around a suspected inclusion may shift between focal planes. A composite could make that ring appear continuous. The source frames help a reviewer decide whether the ring describes the sample or the assembly process. This is an illustrative imaging problem, not a NANOLAB test result.

Prepare a reviewable final figure

Label stacked images as stacked. Tie the scale bar to calibrated image dimensions; never paste a bar from another magnification or resize it independently. State relevant cropping, contrast adjustment and compositing. Include a single-plane view beside the composite when it resolves an important ambiguity.

Retain an unedited copy and give processed versions distinct filenames. A reviewer should be able to move from the published figure back to the original frames and sample location. A strong report distinguishes what is visible, what was measured and what remains unresolved.

Technical references

These sources support the identified technical concepts. The planning examples in this guide are illustrative and are not NANOLAB performance test results.

• Leica Microsystems: depth of field in microscope images

Related guides

• Coating Microscopy Images: Keep the Scale Bar and Sample Context
• Keeping Focus and Camera Distance Consistent in Gloss Comparisons

Discuss your surface and intended use with NANOLAB. Follow the current instructions for the exact product when planning application and care.