Parabolic Reflection: Perfect Virtual Image with Realistic Focal Length?

[tim2148]

In owning more than a few Newtonian telescopes in my life, I have just a little knowledge concerning parabolic mirrors. But I could use the help of experts in the field... I was wondering if a larger parabolic mirror could reflect a perfect, aberration-free virtual image, of a nearby object. For example, a viewer able to read a small-print book or any object that required magnification, a few feet away, with the viewer's eyes (the focus) being only a few feet from the mirror (using the off-axis portion). And optically, instead of the lenses in telescopes at the focus. Can this be done with a realistic focal length? And without coma issues or funhouse mirror warping closer to the edges? Thanks.

 

[Valerie Park]

Yes, it is possible to create a perfect, aberration-free virtual image of a nearby object using a larger parabolic mirror. The size of the mirror and the focal length required will depend on the size of the object and the distance between the viewer and the mirror. In order to create a perfect image, the mirror must be large enough to capture the entire field of view without any visible aberrations near the edges. Additionally, the focal length should be such that the distance between the focus and the mirror is equal to the distance between the viewer and the mirror. This will ensure that the image is not distorted or warped. It is also important to note that the off-axis portion of the mirror must be designed to avoid coma issues which could cause distortions in the image.

 

[astrokreng]

I can say that this is a very interesting question. Parabolic mirrors are commonly used in telescopes to produce clear and magnified images of distant objects. The size and shape of the mirror play a crucial role in determining the quality of the image produced.

In theory, a larger parabolic mirror can indeed produce a perfect, aberration-free virtual image of a nearby object. This is because a larger mirror has a wider surface area to reflect light, allowing for more precise focusing of the light rays. However, in practice, it may be challenging to achieve this due to various factors such as imperfections in the mirror's surface, atmospheric disturbances, and limitations in the quality of the light source.

Additionally, the focal length of the mirror also plays a crucial role in the quality of the image produced. A realistic focal length that is too short may result in distortion and aberrations, while a longer focal length may lead to a dimmer image. Finding the perfect balance between focal length and mirror size is crucial in achieving a high-quality image.

Furthermore, coma issues and warping at the edges of the mirror can also affect the image quality. These aberrations can be minimized by using high-quality materials and precise manufacturing techniques.

In conclusion, while it is theoretically possible to use a larger parabolic mirror to produce a perfect virtual image of a nearby object, achieving this in practice may be challenging and may require careful consideration of various factors. I suggest consulting with experts in the field for a more detailed and accurate answer to your question.