Very Close Focus

Very close focus inspections, typically in the 0–3 mm range, require precise lens configuration and careful handling of the scope. Zibra Corp’s in-house lens design capabilities allow for custom-built objective lenses that meet specialized close focus requirements with minimal lead times.

Fiber-based scopes are highly sensitive to the tip lens focus, which is fixed at the time of manufacturing and cannot be altered by adjusting the video or eyepiece lenses. In contrast, rigid scopes use a relay lens system that allows refocusing at the rear lenses, changing the working distance at the tip. This makes rigid scopes more adaptable to varying inspection distances.

In close focus applications, the reduced depth of field requires precise positioning of the probe. Illumination can also present a challenge, as sufficient space is needed for light to reach the inspection area. Mirror tubes are sometimes employed in side-view close focus setups, as the air gap between the scope tip, mirror, and target enables the light to converge properly at the focal point.

Zibra Corp incorporates focus distance into probe specifications, ensuring each scope is configured for its intended use. Our engineering team works closely with customers to determine the correct optical design for each close focus application, delivering scopes that provide sharp, consistent imaging at extremely short working distances.