Off-axis Explained: What it is & How it Contributes to Comatic Aberration

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In summary: Off axis rays can cause various types of comatic aberration.A diagram illustrating off-axis rays in a mirror is called an off-axis diagram.
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roshan2004
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As I was studying Comatic aberration, in the definition of coma the word off-axis is used which I couldnot understand. What does off axis means? and how does it contribute to the comatic aberration? I also want to know about off axis diagrammatically.Thanks......
 
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By "axis" I assume you mean principle axis this beng a line drawn at 90 degrees through the centre of the lens/mirror.Off axis therefore would refer to a line parallel to the principle axis but above or below it or it could refer to a line at an angle to the principle axis.
 
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  • #3
roshan2004 said:
As I was studying Comatic aberration, in the definition of coma the word off-axis is used which I couldnot understand. What does off axis means? and how does it contribute to the comatic aberration? I also want to know about off axis diagrammatically.Thanks......

Diagram and explanation...

http://www.telescope-optics.net/coma.htm

...
 
  • #4
roshan2004 said:
As I was studying Comatic aberration, in the definition of coma the word off-axis is used which I couldnot understand. What does off axis means? and how does it contribute to the comatic aberration? I also want to know about off axis diagrammatically.Thanks......

As Creator's posted link states, the 'axis' refers to the "optical axis", which is an imaginary line that defines the centerline of the optical system. For rotationally symmetric elements (round lenses, etc), the optical axis passes through the center of each element.

Coma is an aberration that is identically zero on the optical axis.
 
  • #5
I am still confused about optical axis and off axis.Are these terms same or different?
 
  • #6
roshan2004 said:
I am still confused about optical axis and off axis.Are these terms same or different?

Principle axis,optical axis or just axis call it what you will,it is the line that passes symmetrically(at 90 degrees)through the centre of the lens/mirror.A ray passing through the optical axis of a lens will be refracted but it will not be deviated through an angle or laterally displaced,it will pass straight through.A ray traveling along the optical axis of a curved mirror will reflect back along the optical axis.Off axis refers to any ray that is not traveling along the optical axis.
 

1. What is off-axis and how does it contribute to comatic aberration?

Off-axis refers to the position of an object or light source that is not aligned with the central axis of a lens or mirror. In optics, comatic aberration is a type of optical distortion that occurs when off-axis light rays are focused at different points, resulting in a distorted image. Off-axis light rays contribute to comatic aberration by introducing varying degrees of distortion depending on their angle of incidence on the lens or mirror.

2. What causes off-axis light to contribute to comatic aberration?

Off-axis light rays contribute to comatic aberration due to the shape and curvature of lenses and mirrors. As off-axis light rays pass through or reflect off these optical surfaces, they are bent and focused at different points, causing a distorted image.

3. Can off-axis light be corrected to reduce comatic aberration?

Yes, off-axis light can be corrected to reduce comatic aberration using techniques such as aspheric lens design, multiple lens elements, or specialized coatings. These methods help to minimize the distortion caused by off-axis light rays and improve overall image quality.

4. Is off-axis light always a negative factor in optics?

No, off-axis light can also be used advantageously in certain optical designs. For example, off-axis illumination can be used in telescopes and microscopes to capture a wider field of view or to reduce the effects of certain types of aberrations.

5. How does off-axis light affect the performance of optical systems?

Off-axis light can significantly impact the performance of optical systems, especially those that require high precision and accuracy. It can introduce various types of aberrations, such as comatic aberration, which can result in distorted or blurred images. Therefore, it is important for optical systems to be designed and optimized to minimize the effects of off-axis light.

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