Why Does a Fresnel Lens Create an Upright Image in a Galilean Telescope Setup?

In summary, the conversation discusses the use of a Fresnel lens and its similarities to a Plano Convex lens in terms of geometric optics. It also mentions the formation of an upright image when viewed through the lens with the naked eye, compared to an inverted image when viewed through a screen. The conversation concludes with a resource for further information on object-image relations for converging lenses.
  • #1
soomro
2
0
I have a Fresnel lens which is equal-ant to a Plano Convex lens, Consider object on one side and my eye is on the other side of the lens, when I see through that lens I always do see an upright image of same size even if I flip the lens, Can anyone please tell me geometric optics equal-ant of this configuration.


eye--------200-500mm di ---------- FRESNEL lens ------------- 500mm dis-------------OBJ
 
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  • #2
Considering only geometric optics, plano-convex lenses work the same when viewed from either side.

There are slight differences for wave optics, but they are seldom noticeable except in the context of lasers and the minimization of phase errors.

The best way to estimate the focal length is allow sunlight to fall on the lens, and measure the distance when it forms an image.
 
  • #3
MY question is why I do see upright image with naked eye if eye look from other side of lens, while if I place screen on other side I do see inverted image which it should be.

If I do use simple geometric optics Its will be 1-OBJ 2-LENS and 3-Image, but if there is no screen on image plan & I see it with naked eye I do always see upright image.
 
  • #5


The configuration you have described is known as a Galilean telescope, which is a type of optical system that uses a combination of a negative and positive lens to create a magnified, upright image. The Fresnel lens in this case acts as the negative lens, while the object being viewed serves as the positive lens. This setup is commonly used in low-power telescopes and binoculars due to its compact design and ability to produce a clear image. In terms of geometric optics, this configuration can be explained by the principles of refraction and the formation of virtual images. As light passes through the Fresnel lens, it is refracted and diverged, creating a virtual image that is then magnified through the positive lens. The orientation of the image remains the same due to the symmetry of the lenses and the placement of the object and eye in relation to the lens. Overall, the Galilean telescope using a Fresnel lens is an efficient and effective way to view objects at a distance.
 

Related to Why Does a Fresnel Lens Create an Upright Image in a Galilean Telescope Setup?

1. How does a Fersnel lens work?

A Fersnel lens is a type of lens that utilizes a series of concentric grooves on the surface to bend and focus light. The grooves act as a series of tiny prisms, directing the light towards a central point, creating a magnified image.

2. What are the advantages of using a Fersnel lens for imaging?

Fersnel lenses are thinner and lighter than traditional lenses, making them more compact and easier to handle. They also have a larger aperture, allowing for more light to pass through and creating a brighter image. Additionally, Fersnel lenses have minimal chromatic aberration, resulting in a sharper and more accurate image.

3. Can a Fersnel lens be used for both magnification and projection?

Yes, Fersnel lenses are commonly used for both magnification and projection purposes. They can be used in devices such as magnifying glasses, projectors, and even lighthouses.

4. What are the limitations of a Fersnel lens for imaging?

One limitation of Fersnel lenses is that they have a lower resolving power compared to traditional lenses. This means that they may not be suitable for high-precision imaging applications. Additionally, Fersnel lenses can produce some optical distortions, such as the "bullseye effect", which can affect the quality of the image.

5. How are Fersnel lenses made?

A Fersnel lens is typically made by molding plastic or glass into a series of concentric grooves. These grooves can also be etched onto the surface of a lens. The manufacturing process for Fersnel lenses is relatively simple and cost-effective, making them a popular choice for various applications.

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