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0answers
40 views

Effects of lenses

I have three convex lenses that I'm arranging so as to function as a crude magnification device. My question is about the image that I see. It seems that no matter how I arrange them, with respect to ...
1
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2answers
85 views

Why does shorter focal length result in greater beam divergence?

So I got 2 converging Fresnel lenses, one with 50 mm focal length and other 70 mm. My experiment looks like this: When trying to focus and SMD LED emitter into a narrow beam (sticking to lenses ...
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0answers
14 views

Laser Diode with micro lens problem

Good morning all, I am looking at using a laser diode with a micro lens already applied to the fast axis.Here are the numbers I have been given by the manufacturer: 8° Diveregnce on both axis after ...
0
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1answer
75 views

Newton's ring conceptual doubt

Newton’s rings are formed as a result of interference between light waves reflected from the upper and lower surfaces of the air film developed between the convex surface of the plano-convex lens and ...
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0answers
21 views

Is the object focus always on the same side as the incident ray in converging lens?

We know that representation of a lens is made up of the lens itself, the principle axis, 2 foci points (object and image focus) and the optical center. In my notes it says that in a converging lens ...
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3answers
57 views

Why do we need telescopes/ binoculars/ etc? [closed]

Why do we need to use magnifying objects to see things that are far from us? Why isn't the light coming from those objects enough for us to see without special aid? Is it because light loses energy on ...
2
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1answer
24 views

What refractive index should be used while calculating the focal length of lens using lensmaker's formula?

Suppose a lens is half dipped in liquid. Then should the refractive index of liquid with respect to air should be taken. Or should refractive index of glass wih respect to liquid be taken. Or perhaps ...
0
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1answer
46 views

Calculating pupil magnification

Is it possible to calculate pupil magnification, given that these lens parameters are known: focal length f-number at infinity focus positions of front and back principal points position of the ...
0
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1answer
40 views

Front/rear effective diameter on a camera lens

I'm in the process of trying to understand lenses a bit better so I decided to take a look at the specs of an actual lens I have access to: Kowa LM25HC (datasheet). Can someone explain the meaning of ...
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1answer
22 views

Does entrance pupil diameter change with object distance?

Here is my current understanding of things, correct me if I'm wrong. Entrance pupil diameter effectively determines the light-gathering ability of a lens. It is related to the working f-number by the ...
0
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1answer
27 views

Thins Lens Equation Question

According to my textbook, it says that according to the thin lens equation, object distance and image distance vary inversely. However, when I do a converging lens simulation, as I increase the ...
-1
votes
1answer
38 views

Sign convention for lens [duplicate]

What will be the sign convention for radius of curvature of a concavo-convex lens ? I know for equibiconcave and equibiconvex separately but for mixed one I am not clear . For example for the ...
0
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0answers
66 views

“3f system” - two lenses with the same focus

Lets assume we have a point source of light. In a distance of f after it we have a lens with focus f and a mask, and in a distance f after it we have another lens with focus f. Than we look at the ...
38
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1answer
4k views

How is a (rifle scope) reticle in focus?

The lens zooms and focuses something very far away, yet the reticle inside the lens assembly is in perfect focus just like the far objects. How?
0
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0answers
62 views

Lens designing and light splitting

months ago I started thinking about making a lense that will have special features - high FOV without fisheye effect. I have written a program that solved it for me, here is a preview - it increases ...
0
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0answers
14 views

How do I determine the lens to set the focal length of a converging or diverging beam?

I have a gaussian beam going through two lenses. The first lens is focusing a collimated gaussian beam to a focal point either before or after the second lens. What formula do I use to get the focal ...
1
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0answers
26 views

Geometric optics limit in lens design [closed]

What is the rule-of-a-thumb ratio of lens' thickness to wavelength at which they can be designed using ray optics approximation? (The thickness is more relevant to gradient index lens, homogeneous ...
1
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0answers
16 views

Will a combination lens have symmetric focal length on either side?

In this discussion on finding the focal length for combination lens, the image described in the answer shows the measure of focal lengths. Description of the Gullstrand equation also talk about front ...
2
votes
2answers
47 views

Focusing white LED light into a spot as small as possible

An aperture (about 1mm) is placed 2cm in fount of the LED, collimated by a f=50mm lens, then focused by a f=100mm lens into a 3x3mm spot. The focal distance of the second lens cannot be decreased. ...
0
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0answers
70 views

How do hypermetropic people see objects beyond the focus of their convex corrective lenses?

The way I have developed intuition about optics suggests that humans can only see objects if two rays of light that originally emanated from the same point reach the eye in a way such that when ...
1
vote
2answers
60 views

Depth of field of the human eye

When reading about the basics of photography and the physics involved, I learned about  depth of field. Long story short, the message is that with a smaller aperture, the length of the depth of field ...
2
votes
2answers
73 views

Difference in focus between lenses and glasses [closed]

I have both glasses and contact lenses. The prescriptions are both recent and up to date. I am 46, so I'm starting to have a harder time to focus on things that are very close to my eyes, compared ...
1
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0answers
30 views

Biconvex lenses in 2 media

The question is what is the formula of the focal length of a biconvex thin lens if object medium is water and the image medium is air. I know that we have: 1/f = (n-1)*(1/R1 - 1/R2) , if the medium ...
0
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0answers
24 views

Screen distort for corrective lens

Can we apply a screen distort for corrective lens for eye ware instead of using a lens maker? Just test at home with a phone screen and buy at shop. To reframe the question can we bring to effect a ...
2
votes
1answer
49 views

Focal length of Convex lens

Is it true that, twice the focal length of a convex lens is equal to the radius of curvature? Please give your opinion.
1
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2answers
56 views

What's the difference between these two approximations for thin lenses?

I have seen the thin lens equation, which describes the following relation. $$\frac{1}{\text{image distance}} + \frac{1}{\text{object distance}} = \frac{1}{\text{focal length}} \tag{1}$$ However, I'...
0
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0answers
42 views

Spherical aberrations: 2 Plano-convex lenses with suitable distance

" By using two Plano-convex lenses separated by a suitable distance: When the two plano-convex lenses are separated at a suitable distance, the total deviation is divided equally between the two ...
1
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3answers
43 views

Does density of light power (w/m²) increase after passing a convex lens ?

Does density of light power (w/m²) increase after passing a convex lens ? and if so i need the equation that represent that increase
1
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1answer
61 views

Can we see through the central obstruction of a lens?

I have a very basic question in optics inspired by this article from the University of Stanford which clearly states that one should see a light source through a mask in the middle of a lens if the ...
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votes
1answer
24 views

For nearsightedness how does the concave lens not shift the focus point for near objects?

In case of myopia, the light focuses in front of, instead of on, the retina when observing far away objects. while for near objects the eye is able to focus the light onto the retina. For most people ...
0
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0answers
15 views

In this situation, is an endless sequence of images (theoretically) formed?

I was dealing with an optics problem, where an object is placed at $u= -60$ cm in front of a biconvex lens of radius of curvature $R=30$ cm and refractive index $\mu=1.5$ . Simple calculations show ...
0
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0answers
27 views

Conservation of radiant flux in imaging?

I've been deriving the imaging equation for irradiance on a photosensor in terms of the object radiance: $$ E(x,y)=\frac{1}{f^2}\int\!\!\!\int \, L(x,y,u,v)\cos^4\theta \, \mathrm{d}u\,\mathrm{d}v ,$...
0
votes
1answer
37 views

Lens metrology: How to measure a double-sided thick aspherical lens optically?

In lens metrology, how do people measure a double-sided thick aspherical lens optically? By "optically" I mean for example, using wavefront sensing, interferometry or the interferogram methods. I ...
0
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0answers
25 views

what needs to be minded when changing the lens on a Time of Flight camera

Okay, so first of all I'm not really an expert when it comes to optics, but I have a small project where I would like to simulate how the behavior would change if I apply a different lens on the ToF-...
0
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0answers
35 views

In Ray Optics, For combination of lenses, what is an optical interval?

In ray optics, what is an optical interval? i have no idea about optical interval. please explain deeply
1
vote
1answer
44 views

How does the human eye not get a distorted image from an irregular object?

Suppose I have a sheet of cardboard, or for that matter any irregularly shaped object. Now we do know that reflection on cardboard is irregular and not specular as it is a rough surface compared to a ...
0
votes
1answer
23 views

Determining a spherical mirror setup just from the image and object heights

I am working through some questions to prepare for an upcoming exam and got stumped by a question involving a spherical mirror where we are only provided with the image height (1 cm), object height (0....
0
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2answers
41 views

Confused with image and object distance in lens

I am not sure why S is negative in this image. How do we determine whether it's negative or positive?
1
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2answers
70 views

Light focusing on long distances

If I have a green laser (500 nm wavelength) with initial beam diameter 3 mm, with proper lenses I can easily focus it to 1 mm or 0.5 mm for small distances like 10 cm. My question is can I focus it ...
1
vote
2answers
52 views

Human eye dispersion [duplicate]

As we know dispersion is caused by a convex lens.our human eye also has a convex lens so dispersion must take place in eye also this leading to a formation of blurred image on retina.then why are we ...
0
votes
1answer
22 views

Making a lense using an array?

Would it be possible to build a lense out of array elements with a higher refractive index inter spaced with void elements eg a matrix of glass with air. I imagine that the spacing would have to be ...
1
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0answers
19 views

Directional multi perspective mini magnifying glass

I recently stumbled across an optical challenge that apparently nobody seems to be able to solve. It is about an optical device that should magnify rays of light from specific directions. Explaining ...
1
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1answer
73 views

Shape of a virtual image

There are a lot of posts regarding real vs virtual images. I 'think' I understand the distinction clearly, however, there is one thing that I can't quite wrap my head around. What is the "shape" or ...
2
votes
2answers
221 views

How to measure the refractive index of a lens?

how to measure the refractive index of a lens? (a simple method) I want to find a simple method to measure the refractive index of a lens.
0
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0answers
30 views

Calculate Optical-Ray Angle (in respect to optical Axis) for every Pixel on Sensor Plane

I'm currently working on designing a catadioptric image system for mobile robot systems and do think I need help with the first steps of the calculation. The design of the mirror will be based on this ...
-1
votes
1answer
230 views

Should the thickness of a plano-convex lens affect its focal length and intensity of light at the image?

Using Lens maker formula for thick lens, where f is the focal length R1 and R2 are the radii of the two sides d is the thickness n is the index of refraction For a plano-convex lens, R2=∞. So the ...
0
votes
1answer
46 views

Why does the human eye-lens have a constant magnification for a fixed object distance?

The human eye-lens flexes to change focal length and thereby bring objects of various distance into focus. The magnification of the lens $M$ is always constant for an object with distance $d_o$ ...
2
votes
1answer
62 views

Geometric optics question (from 2001 GRE)

In the diagram above, two lenses with focal lengths $f_1 = 20$ cm and $f_2 = 10$ cm are placed $40$ cm and $70$ cm from an object $O$, respectively. Where is the final image formed by the two-lens ...
0
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1answer
22 views

How can I achieve small field of view by 2 or more lenses?

I have the following problem. I have a sensor with 1mm diameter and I need to have 500 urad (microradian) field of view. If I understand correctly, that would generally mean that I need to use 2meter ...
0
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1answer
31 views

Distorted Converging Lens

You have a converging lens made from a certain plastic that focuses sunlight when the lens is 12 cm from the ground. The lens is curved identically on both sides. You leave it out in the sun so that ...