Olympus DPlan 50x Oil Immersion Objective

The Olympus D Plan 50X Oil Immersion objective (part number 1-LB555) is a high-magnification achromat with a built-in iris diaphragm, designed for the Olympus BHT, BHTU, BHS, CHS, and CHT microscope series. At 50X with a maximum NA of 0.90, it delivers the resolving power needed to clearly distinguish fine subcellular structures, microorganisms, and material surface features at a magnification level that sits between the common 40X dry and 60X/100X oil objectives.

The integrated iris diaphragm is a particularly useful feature — it allows you to continuously adjust the effective numerical aperture without changing objectives. Stopping down the iris reduces NA, which increases depth of field and improves contrast on low-contrast specimens, while opening it fully maximizes resolution. This makes the 50X iris objective especially practical for metallurgy, materials inspection, and any application where specimen contrast varies significantly.

Oil immersion at this magnification eliminates the refractive index mismatch between the objective front element and the coverslip, ensuring maximum light collection and sharpest possible images. Standard RMS threading and 160mm tube length make this a direct drop-in for any BHT/BHS/CH-era Olympus nosepiece. This unit is in excellent condition with flawless optics.