Focus & Stage

Focus Won't Stay Put? A 10-Second Fix.

A quick reference for focus that drifts down after you let go.

Tim Pellerin · Sky Optical Services

You focus, look away for a second, and the image has drifted down out of focus. It is frustrating, but it is usually a tension setting, not a worn-out microscope, and on most scopes you can fix it in about ten seconds.

Do this

Find the tension ring. On most scopes it sits next to the coarse focus knob. Turn it to add drag.
Set it snug, not stiff. Just enough that the stage holds its position.
Test it. Focus, wait ten seconds, and look again.
Check the stage knobs too. Stage sliding on its own? Many mechanical stages have a tension collar on the X and Y knobs.

Avoid this

Forcing a stuck knob. If a knob will not turn, stop. Forcing it can strip the gears.
Twisting the two focus knobs against each other. Turning the left and right knobs in opposite directions can damage the mechanism.
Over-tightening. Too stiff makes focusing jerky and wears the gears.
Still slipping or grinding. The focus gears or rack may be worn. That is a service call.

The habit, every time

STEP 1

Tension ring snug

STEP 2

Test: focus holds

STEP 3

Stage knob tension

Watch it in a minute

Microscope Minute from Sky Optical Services

Still slipping, or grinding when you turn the knob? The focus gears or rack may be worn. That is a service call. Never force a stuck knob.

Request Service Printable Guide (PDF) Watch the Video

Need hands-on help? See our microscope repair and maintenance service in Houston.

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