When it comes time to build an optical system, you&#;re not going to get very far without familiarizing yourself with the plano-convex lens or singlet spherical lens. Whether it&#;s an industrial, pharmaceutical, defense or CO2 laser application, the plano-convex lens is essential if light needs to be focused, collected and collimated.

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A plano-convex lens is an optical component whose purpose is to focus light into a single point. The &#;plano&#; portion refers to one side being flat (a plane) and the &#;convex&#; portion refers to the other portion of the lens being bowed outward. A plano-concave lens (a subject for another day) means it is bowed inward or is caved in.

This outward bowing produces what&#;s called a positive focal length. A positive focal length means that the focal point (or the point where light converges) is on the opposite side of the lens as the object. This means the image will be both inverted and flipped as seen in the below image.

Difference between plano-convex and biconvex lens

• Thread starter

  klng

• Start date

  Jun 6,

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  Difference Lens

In summary: The best antireflection coatings can reduce loss to about 0.1%.In summary, to focus a large diverging beam, you will need to use a lens with an appropriate focal length and coating. Good luck with your setup!In summary, the conversation discussed the use of two plano-convex lenses for a simple telescope setup. It was mentioned that it does not matter which side of the lens faces the light source, as long as the focal lengths are correct. There was also a discussion about the best way to minimize spherical aberrations in a telescope, with the conclusion being that having the two plane surfaces facing each other is the best method. Additionally, the conversation touched on the use of plano-convex vs bicon

• Jun 6,

• #1

klng

22

0

Hi all,

I am implementing a lab activity for a 2 lens set-up that will serve as a simple telescope.

In the teacher's manual, it lists down 2 plano-convex lenses, with the 2 curved surfaces facing each other. The plane faces will respectively face the light source and the observer's eye.

A simple net search shows that regardless of which side (i.e. plane or curved) of the planoconvex lens is facing the light source, the point of convergence of the light rays will be the same on the opposite side of the lens.

Which then begs the following 2 questions, what then is the key difference(s) between a plano-convex lens and a biconvex lens? Will my 'telescope' fail to work if i use 2 biconvex lens instead?

Thanks in advance. Physics Forums rock!

 

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• Jun 6,

• #2

Lambduh

69

1

It won't matter at all. For a set up like a simple telescope all that matters are the focal lengths of the lenses.

There shouldn't be much of a difference at all.

 

• Jun 6,

• #3

Redbelly98

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Biconvex lenses will be worse than plano-convex in terms of spherical aberrations.

Using two plano-convex lenses, with the plane surfaces facing each other, would minimize spherical aberrations in a telescope. It seems the teacher's manual got it wrong, or the author was not considering aberrations when they made the telescope diagram.

 

• Jun 6,

• #4

Andy Resnick

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Redbelly98's correct- the idea is to have each surface participate equally in the optical power of the combined instrument. For example, using a plano-convex singlet to expand and collimate a light coming out of a pinhole (a spatial filter), putting the plane side facing the collimated beam side will result in considerably more spherical aberration than placing the plane side towards the pinhole- in the first situation, the plae surface contributes zero optical power, while in the second it contributes power.

Are you interested in learning more about Imaging Plano Convex Lens? Contact us today to secure an expert consultation!

 

• Jun 6,

• #5

klng

22

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Thanks a lot to all those who have applied. This forum is a great resource haven.

So to conclude, a better way to have a better telescope will be to have the 2 plane surfaces facing each other. The curved surfaces will then face the light source and the observer's eye respectively. Is this the right conclusion?

 

• Jun 7,

• #6

Redbelly98

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Yes, that's right.

 

• Aug 18,

• #7

Artie84

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What's written here is correct in many cases, but it is dependent on what your application is:

1. If your 'telescope' is for imaging distant objects:

In this case the object is near infinity and the incoming field can be considered nearly collimated. Plano-convex lenses are best, with flat surfaces facing the inside of the telescope. The goal is to have both sides of the lens active in deviating the light direction.

2. If your 'telescope' is being used for image relay of small, nearby objects about a focal distance away from the lenses:

Plano-convex is fine, but the flat surfaces should now be facing outward. If the magnification of this image relay system is close to 1:1, then the use of biconvex lenses will eliminate most abberation. If the magnification is far from 1:1, then biconvex lenses will make things worse.

In any case, orientation and use of plano-convex vs. biconvex lenses won't matter terribly much. You will still form a fine image so long as the lenses are the correct distance apart. These details only affect small distortions in the image.

 

• May 27,

• #8

udayag

2

0

hi to alll

I am new to this forum. I have small doubt regarding converging light beam. I have highly diverge light beam of diameter of 1cm. I want to focus or converge the light beam with the distance of 20cm.How can i achieve maximum focus without much loss? which type of lens shall i use?.

I planned to use of planoconvex lens. expecting the your earliest response guys

Thank you for your attention

 

• May 28,

• #9

Artie84

2

0

Hi Udayag,

This is probably not the right thread for your question, but I'll try to answer it anyway.

First, your question is not very clear. My guess is that you are trying to focus a large diverging beam, and you want the focus to be 20cm away from your lens.

If you are focusing a collimated beam, this is easy: Just use a 20cm focal length lens.

If you are focusing a diverging beam, it is more difficult. If you know where the previous focus is, you can use the lens equation, [tex]$/frac{1}{f}=/frac{1}{d_o}+/frac{1}{d_i}$[/tex] to determine the focal length. If not, you can try trial and error.

The most typical way to focus a diverging beam is in a "4-f system", meaning four focal lengths. This actually uses two lenses. The first lens collimates the diverging beam, and the second focuses it. This is used for systems where it is important to preserve the wavefront shape across distances. If your beam is a simple gaussian beam (the standard output of most solid-state lasers), you don't need to worry about the 4-f configuration.

Either way, to minimize loss you need to make sure you have an appropriate coating on your lens. An uncoated lens will typically give you 8% loss (a 4% reflection on both the front and back surfaces). It is standard to sell lenses with broadband coatings that reduce loss to less than 1% over a range of wavelengths.

 

FAQ: Difference between plano-convex and biconvex lens

What is the difference between a plano-convex and a biconvex lens?

A plano-convex lens has one flat side and one convex side, while a biconvex lens has two convex sides. This means that the curvature of a plano-convex lens is only on one side, while the curvature of a biconvex lens is on both sides.

Which type of lens has a greater focal length?

A biconvex lens has a greater focal length than a plano-convex lens. This is because the curvature on both sides of a biconvex lens allows for light to converge at a greater distance, resulting in a longer focal length.

What are the advantages of using a plano-convex or biconvex lens?

Both types of lenses have their own advantages. A plano-convex lens is easier to manufacture and has a lower cost compared to a biconvex lens. On the other hand, a biconvex lens has a longer focal length and can produce less distortion in images.

Which type of lens is commonly used in magnifying glasses?

Biconvex lenses are commonly used in magnifying glasses. This is because of their longer focal length and ability to produce clear magnified images.

Can plano-convex and biconvex lenses be used interchangeably?

In some cases, these lenses can be used interchangeably. However, it is important to consider the specific application and the properties of each type of lens before making a substitution. For example, a biconvex lens may not be suitable for applications that require a flat field of view.

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