Design of an Imaging Telescope with Variable Magnification and Imaging Distance

Vacuum spatial filters, used to control beam quality and remove unwanted high spatial frequency noise from amplified beam pulses, mostly rely on two-lens imaging telescopes with no flexibility in magnification and imaging distance unless the lenses themselves are replaced. New three-lens and four-lens imaging telescopes facilitate adjustable beam magnification and imaging distance by altering only lens positions. Systems of ray matrices were constructed for three-lens and four-lens systems. This formalism determines the required adjustments of lens positions and can be used to predict and analyze beam magnification and imaging distance. Constraints, primarily fixed positions of lenses that are not moved, were set to maximize the convenience of the lens systems, confirming that for a range of magnification, not all lenses need to be moved when optimized initial focal lengths are used. A more detailed ray tracing program was created to model the new designs, verifying ray matrix calculations and revealing a peak-to-valley wave front error of typically 0.02 to 0.05 waves. Experimentally tested three-lens systems presented magnifications with a maximum deviation of 2.3% from the calculated values, confirming the calculations.