in-lens objective lens

One of the objective lenses for the high-resolution SEM.
The in-lens objective lens has a very short focal length, and both spherical and chromatic aberrations of this lens is one to tenth or less compared to those of the out-lens objective lens. Thus, the SEM image resolution is greatly improved at high-to-low accelerating voltage. As shown in Figure, a specimen is placed in a strong magnetic field (indicated by yellow region) created by the pole-piece of the objective lens.
However, the space around the specimen is narrow and the size of the specimen which can be handled is limited, several mm in diameter and 2 to 3 mm in height.
A magnetic material (magnetic specimen) is magnetized by the strong magnetic field in this lens, thereby not suitable for observation of the magnetic specimen.
For the SEM instrument equipped with the in-lens objective lens, it is possible to attach an EDS detector, but WDS and EBSD detectors cannot be attached. To detect secondary electrons emitted from the specimen, the TTL (through-the-lens) detector is used. The side-entry goniometer stage is used as the specimen stage. Due to the structure of the in-lens objective lens, the type of the goniometer stage is similar to that for TEM.