Lens intermediate

Diffraction lens Intermediate lens Projector lens... 

The final set of magnetic lenses beneath the specimen are jointly referred to as post-specimen lenses. Their primary task is to magnify the signal transferred by the objective lens. Modern instruments typically contain four post-specimen lenses diffraction, intermediate, projector 1, and projector 2 (in, order of appearance below the specimen). They provide a TEM with its tremendous magnification flexibility. 

Fig. 2. (a) Ray diagram in the electron microscope under imaging (microscopy) conditions. E electron source C condenser lens S sample O objective lens bfp back focal plane of O I intermediate lens P projector lens, (b) Structural imaging, diffraction and compositional functionalities of TEM. 

Figure 2.5 Operational principles of a transmission electron microscope. S, specimen OL, objective lens BF, back focal plane Imj, intermediate image IL, intermediate lens Im2, second intermediate image PL, projector lens FIm, final image DP, diffraction pattern.

Because elements that will later form the CNS appear earlier than most other systems in the developmental process, disturbances of neurulation may result in severe abnormalities of the brain and spinal cord. Other ectodermal thickenings, the otic placode and lens placode, develop into the inner ear and lens, respectively. A series of mesodermal blocks called somites form around the neural tube, and these somites give rise to the axial skeleton. The intraembryonic coelom appears in the lateral mesoderm and later divides into the pericardial, pleural and peritoneal cavities. The intermediate mesoderm forms the nephrogenic cord, which later becomes the kidneys. 

---