Tasks

Tasks to be solved on the course

Task 1

Make a good magnified image 1:2, using only two plano-convex singlet lenses. The system shall have an aperture between the lenses, that are to be separated by 1-2mm. Choose one lens with f=100mm and the other with f=200mm and orient the for best performance. The f-number (defined as the system focal length divided by the diameter of the aperture) shall be 2, and there is to be no vinjetting.

The object is 20mm and the imaging quality shall be such that spot size in the middle of the image is max 1mm. Defocus if you need.

Q1.1 What is the spot size for a periferal image point? Compare to the spot size for an on-axis point.

Q1.2 Which aberration dominates?

Q1.3 At what spatial frequency does the MTF for an axial image point go to zero? Is the lens diffraction limited?

Task 2

Reduce the aperture to half the original size and answer the same questions as in task 1.

Task 3

Exchange the singlets for achromats,  to get a system with the same magnification and f-number 4 (the same as in task 2). Answer the same questions as in task 1. (Help: if you hadn't already noticed, you can find off-the-shelf achromats in a catalogue in the program.)

Task 4

Construct a telescope with an angular magnification between 7 and 10. Use suitable achromats for all lenses. If you need an aperture somewhere it is ok. Make sure that the field of view is reasonable from what you normally can expect from this kind of equipment.

The resolution of the normal human eye (Visus = 1) is 0,5 mrad. The telescope shall match that.

The aberrations and the spot size should be set at “angular” and the instrument should be adjusted for viewing without accommodation.