Comparison of semi-penta prisms and standard penta prisms
Properties	Semi-Penta Prism	Standard Penta Prism
Number of reflection	1	2
Optical path deflection angle	45°	90°
The direction of the image	Possible reversal (correction required)	Remain unchanged
Volume	Smaller (space-saving)	Larger
Cost	Lower (less material)	Higher

How to select materials for semi-penta prisms?
Laser processing systems: fused silica(UV) or ZnSe(IR) with laser high reflectivity coating.
Imaging systems: primary choice BK7 optical glass with wavefront correction optics.
Extreme environments: fused silica (high-temperature and radiation resistant) or Ge (anti infrared interference).