Objectives

Microscope objectives are the optical components closest to the sample. They collect light from the sample and form the magnified image used by the microscope or optical metrology system.
In 3D optical metrology, the objective plays a key role in determining the measurement field of view, lateral resolution, working distance, depth of field, and the ability to capture fine surface details. Its performance directly affects the quality and reliability of surface measurements.

Microscope objectives are commonly defined by:

  Magnification for example 10X, 40X, 100X: determines the image scale and is directly related to the field of view.

  Numerical aperture (NA): describes the ability of the objective to collect light and resolve fine details. Higher NA usually improves lateral resolution but reduces depth of field.

  Working distance (WD): the distance between the front of the objective and the sample when the image is in focus. This is especially important when measuring structured, tilted, or delicate samples.

  Field of view (FOV): the area of the sample that can be observed or measured in a single acquisition.

  Optical correction: indicates how well the objective compensates for optical aberrations such as chromatic aberration, spherical aberration, and field curvature.

  Objective type and measurement technique: in optical 3D metrology, objectives may be optimized for techniques such as confocal microscopy, interferometry, or focus variation, depending on the system configuration and application.

By selecting the appropriate objective, users can balance measurement area, lateral resolution, working distance, and measurement reliability according to the sample and application.