The invention is directed to a pancratic mirror objective system for laser focussing and especially for laser machining apparatus. The pancratic mirror objective system preferably includes a convex paraboloid mirror and an ellipsoid mirror. The ellipsoid mirror can be approximated by a toric or spherical form. The focus F.sub.1 of the paraboloid mirror P and the first focus of the ellipsoid mirror E are coincident. By rotating the ellipsoid mirror E about the axis parallel to the incident laser beam through the first focus F.sub.1, the effective image side aperture (for example K=4 to K=8) and the focal length are varied. The track control compensates for the movement of the focus F.sub.2 in laser machining apparatus.
In a laser processing machine for processing workpieces using a laser beam (2), a telescope (1) for widening the laser beam (2) comprises an ellipsoidal mirror (3) and a paraboloidal mirror (4) whose axes of rotation (6) extend parallel, in particular collinear, to each other. This orientation permits precise production of the reflecting surfaces of the two mirrors through one single clamping (e.g. through diamond lathe) such that later adjustment is not required.
An optical system capable of providing a magnification which can be varied comprises a pair of ellipsoidal mirrors [(20, 21)]which are so mounted and arranged that the focus for radiation reflected from one mirror corresponds substantially with the input focus for the other mirror. The mirrors are preferably mounted so that they are pivotable.
A beam expander suitable for use with laser machining apparatus comprises a convex paraboloidal surface 7 and a concave paraboloidal surface 8 formed from a single metal element 10. The expander has an optional zoom facility provided by a plane mirror 12, moveable along an input-output axis, for altering the position of an incident beam on the convex surface 7 thereby altering the magnification of the system.
