| 摘要 |
The target body (12) is made of a translucent material, e.g glass, having a refractive index n approximately equal to 2. The incident surface (14) is spherical convex. The rear surface (16) is flat or slightly curved. The centre of curvature of the rear surface lies on the axis of the hemisphere and the ratio of the radius (R2) of the rear surface to that (R1) of the incident surface is 2/(2-n) so that a refractive index of two gives a flat surface. The rear section is covered by a reflecting layer. The incident beam enter the target through the spherical surface, is reflected by the rear surface twice before exiting the target through the spherical surface. The reflected beam is parallel to the incident one.
|
