Optical systems for spy-hole
![image_systeme-optique-a-judas-](https://glass.promic.fr/wp-content/uploads/2020/11/image_systeme-optique-a-judas-.jpg)
Optical systems for spy-hole
A spy-hole is composed of an optical system including several lenses
which allow to widen the field of vision
A spy-hole is composed of an optical system including several lenses
which allow to widen the field of vision