Autofocus Is Not Always the Safer Choice

Most code reader specs start with one question: does it autofocus?Autofocus sounds safer. It handles more distances, more product heights, more variety.
Flexibility has a cost.

Autofocus in a modern code reader usually means a liquid lens. When voltage changes, the fluid reshapes, and the system refocuses. That refocus takes time. Fast implementations settle in tens of milliseconds. Some published specs run near 100 ms.

At 330 ft/min (100 m/min, a common packaging cadence), 100 ms of settling equals about 6.6 inches of part travel, often longer than the part itself. That is the gap between where the lens focused and where the part actually is when the shutter fires.

An autofocus system still has to decide where to focus. Distance sensors get fooled by shiny or angled surfaces. Image analysis costs frames. Focus sweeps pay settling time at every step.

A barcode decoder does not need tack-sharp focus. It needs enough contrast to resolve the pattern. A C-mount fixed lens with the iris stopped down often covers more product-height variation than a liquid lens refocusing on every part, without the settling cost.

Fixed focus is the stronger optical choice. Liquid lens is only worth it when the focus actually needs to change during operation, and there the cost is settling time on every read. If the liquid lens just sets the distance once at install, the cost becomes reduced depth of field. The harder question is which cost your application is actually paying.