Keplerian Telescope and real image

[xchen2004]

Homework Statement

Imagine that you will build a Keplerian telescope and record the images that
it produces on a CCD chip. The CCD chip records the light intensity at each
pixel and thus can be used to produce an image, if the chip is at the location
of a real image. Draw how you will modify the basic Keplerian telescope to
accomplish this. Also, given that the magnification of a telescope is defined as
how much bigger it makes an object look to a given imaging system, does the
magnification change given your modification?

Relevant Equations

none

I know that the Keplerian Telescope produces an inverted virtual image. What modification should I make to generate real images? Will switching the first lens with the second lens change the telescope into a microscope? Thank you!

 

[berkeman]

Welcome to PF.

Can you post a link or two to information about Keperian telescopes and maybe use "Attach files" to upload a typical image of one? Then can you say more about why anything needs to get modified? Thanks.

 

[xchen2004]

Beams are not focused after the second lens. The telescope forms a virtual image. But I need form a real image after telescope to record image on chips.

 

[berkeman]

Okay, good, thanks. So what do you need to add in order to form a real image? Hint -- what does the eye add to form an image on its retina?

 

[xchen2004]

You mean adding a third lens, so the light focuses on the focal point of the third lens, then forms a real image?

 

[berkeman]

That seems like a possibility to me. To form a high quality image, you would want the lens system that you add to be achromatic, but maybe in the context of a simple schoolwork problem, they just want you to insert a simple lens to form the real image.

What equations should you use to calculate the power of that new lens?

 

[xchen2004]

I tried to achieve the task with only 2 lenses. I moved the second lens to the left of the right focal point of the first lens. I can indeed obtain a real image. However, after using ABCD matrix to calculate the angular magnification of the system, I found M<1, which means it is a microscope not a telescope..... Is there a way to achieve a telescope with only two lenses? It is part 1d. Thank you!

 

[phyzguy]

Isn't there already a real image in the drawing you posted of the Keplerian telescope? Can't you just put the CCD there?