Optics : Lens Combinations with laser beam problem

In summary, the conversation revolves around determining the focal length of the second lens and the separation between the lenses in a laser beam expander system. The first lens has a 50.0 mm focal length and the second lens needs to expand a 1.0 mm diameter beam to 8.0 mm. The equation 1/f = 1/f1 + 1/f2 is used to solve for the focal length of the system, and the magnification of the image is determined using the equation Mt=(yf/yi) (per lens). However, the speaker is having trouble finding a logical solution and is seeking assistance.
  • #1
Blitzy89
11
0
Hello. I've been struggling with this problem for some time, and honestly I do not know how to solve it.

Homework Statement



Two positive lenses are to be used as a laser beam expander. An axial 1.0 mm diameter beam enters the short focal length positive lens, which is followed by a somewhat longer focal length positive lens, from which it emerges with a diameter of 8.0 mm. Given that the first lens has a 50.0 mm focal length, determine the focal length of the second lens and the separation between the lenses

I suppose that yi=1.0mm; yf=8.00mm;f1=50.0mm



Homework Equations


Focal length of system = f
1/f = 1/f1 + 1/f2
Magnification of image Mt=(yf/yi) (per lens)


The Attempt at a Solution



I tried to solve this by combining the two lenses as a system, but I can't find an answer that makes sense.
Any help is greatly appreciated.
Thank you
 
Physics news on Phys.org
  • #2
Do you understand the system before putting numbers in ?

http://www.edmundoptics.com/technical-support/lasers/beam-expanders/
 
Last edited by a moderator:

FAQ: Optics : Lens Combinations with laser beam problem

1. How do I calculate the focal length of a lens combination with a laser beam?

The focal length of a lens combination with a laser beam can be calculated by using the formula 1/f = 1/f1 + 1/f2, where f1 and f2 are the focal lengths of the individual lenses. This formula applies to lenses in contact with each other, and the focal length can be positive or negative depending on the orientation of the lenses.

2. Can I use any lens with a laser beam, or are there specific types of lenses that work best?

Not all lenses are suitable for use with a laser beam. It is important to choose a lens that is transparent to the wavelength of the laser and has a high damage threshold to prevent the lens from being damaged by the intense laser light. Additionally, lenses with a longer focal length are more suitable for collimating or focusing a laser beam.

3. How do I determine the spot size of a laser beam after passing through a lens combination?

The spot size of a laser beam after passing through a lens combination can be calculated using the formula d = 2.44λf/D, where λ is the wavelength of the laser, f is the focal length of the lens combination, and D is the diameter of the laser beam before passing through the lenses.

4. What is the difference between a convex and concave lens in terms of their effect on a laser beam?

Convex lenses have a positive focal length and are used to converge or focus a laser beam, while concave lenses have a negative focal length and are used to diverge a laser beam. This is because convex lenses cause the laser beam to bend towards the center and converge, while concave lenses cause the laser beam to bend away from the center and diverge.

5. Can I combine more than two lenses in a lens combination with a laser beam?

Yes, it is possible to combine more than two lenses in a lens combination with a laser beam. However, each additional lens introduces more potential sources of error and can complicate the calculations. It is important to carefully consider the design and purpose of the lens combination before adding more lenses.

Similar threads

How does a dielectric interact with a laser beam?
Replies
1
Views
2K
Analyzing this 2-lens optical system
Replies
5
Views
562
A ABCD matrix formalism for real laser
Replies
0
Views
1K
I Using simple lenses to image AFM Probes
Replies
10
Views
2K
I Tilted plane wave through a 2 lens system
Replies
5
Views
2K
A Mode matching to an optical cavity
Replies
0
Views
1K
I How to narrow a beam to 1 mm diameter?
Replies
1
Views
824
I Total focal length and magnification
Replies
4
Views
2K
Where to place a thin lens to couple a ray into a fiber
Replies
1
Views
1K
4 Lens optical system/fourier transform
Replies
1
Views
1K

Hot Threads

Recent Insights

Back
Top