Question about light and cameras/eyes

This may be a bit of a strange question, but I am really stumped and cannot find a solid answer to this question, I'm hoping someone on ATS will be able to give a good answer. My question is basically this: if light is hitting our eyes from all different directions and angles then wont there be photons which come in from different angles but hit the same sensor at the back of our eye, and if so then how is it that we can form a crystal clear picture of what is in front of us, as if all the photons were coming at our eyes in a perfectly parallel manner? I feel like there's a really simple answer to this but I just cannot see it.

This picture should help illustrate what I mean:


The two yellow lines represent the path of two photons entering the eye through the pupil and then hitting the optical sensor nerves at the back of the eye. Given the difference in the angles at which the photons enter the eye, those two photons could have originated from two objects which are very far apart, but they can both hit the same sensors at the back of the eye. So how is it that we don't see a blurry mix of colors when we look out at the world?

Of course this diagram is very simplified and I have left out the lenses inside our eyes, perhaps there is something in the design of the lenses which prohibits light coming in from certain angles? I have thought about it quite a bit but I cannot see how any type of lense design could prevent this from happening in a consistent fashion. I would really appreciate an answer from someone who understands what is going on here, or sources which explain it. Thanks.

It's the lens that focuses the light. If you take the lens off a camera, you just get blurry crap. And both the lens of the eye and the camera is curved.

This article kind of touches on it, (although it's about the possibility of a camera without a lens)

Cameras as we know them have long been eye-like: a lens captures light and focuses it on film or a detection sensor, just as the lenses in our eyes focus light on our retinas. What would an eye be like without a lens? Capable of receiving light and to some extent discerning color, but otherwise useless, completely unable to focus that light. So a camera without a lens is kind of deal-breaker, right?

Read more: Finally, a Camera Without a Lens (and a Sensor the Size of a Pixel) | TIME.com techland.time.com...

And:

Situated behind the pupil is a colorless, transparent structure called the crystalline lens. Ciliary muscles surround the lens. The muscles hold the lens in place but they also play an important role in vision.

When the muscles relax, they pull on and flatten the lens, allowing the eye to see objects that are far away. To see closer objects clearly, the ciliary muscle must contract in order to thicken the lens.

- See more at: www.livescience.com...

Essentially, when someone has really bad eyesight, (near sighted or far sighted) and can't see squat, it's similar to taking off the lens of an SLR camera and looking through the viewer. (Which is just blurry light blobs.)




To add: (Not sure if it helps)

When light falls on the retina of the human eye, it hits 126 million sensory cells which transform it into electrical signals. Even the smallest unit of light, a photon, can stimulate one of these sensory cells

butdoesitfloat.com...

Here is a really good one for reading: The life of a photon

Of course, it talks in a singular sense, but we dont see single photons.

Boncho covered it. It's the lens that does the trick.

Okay, got the answer you are looking for. (Since you are asking about lens mechanics):

Converging lenses…

library.thinkquest.org...



All of this can be calculated with physics btw. Extremely useful with optics engineering.

Ok, so not only can we control the size of our pupils (for letting more or less light in) but we also have a lense which we can control with muscles inside of our eyes? I didn't realize we could actually control the shape of the lense, now it makes a bit more sense to me. But I'm still not fully understanding how the lense is able to solve this problem, I really need a detailed technical explanation of how it works. You've given me enough to go on for now, I should be able to figure out the rest myself. The reason I need to understand it in such detail is because I want to build a graphics engine which is very much based on the principles of how light travels and how the human eyes work.

ChaoticOrder
Ok, so not only can we control the size of our pupils (for letting more or less light in) but we also have a lense which we can control with muscles inside of our eyes? I didn't realize we could actually control the shape of the lense, now it makes a bit more sense to me. But I'm still not fully understanding how the lense is able to solve this problem, I really need a detailed technical explanation of how it works. You've given me enough to go on for now, I should be able to figure out the rest myself. The reason I need to understand it in such detail is because I want to build a graphics engine which is very much based on the principles of how light travels and how the human eyes work.

The size of your pupils is like an aperture of a camera.

Link

If your f-stop is wrong taking a picture, you are letting too much light in, or not enough, and pictures come out terrible. Thankfully our eyes do it automatically. (It's actually pretty neat how a camera is almost exactly made like the eye, but of course it also makes total sense).

The lens of your eye has an auto focus. No lens, and it's an SLR camera without a lens. With bad eyesight, it's a SLR camera with manual focus set on the wrong distance.

You should consider a night course in photography for fun. Find one that works with film if you can.

ChaoticOrder
The reason I need to understand it in such detail is because I want to build a graphics engine which is very much based on the principles of how light travels and how the human eyes work.

Everything to do with light and perception/manipulation of it, can be found here. With equations to help you along if you need them.

ChaoticOrder
Ok, so not only can we control the size of our pupils (for letting more or less light in) but we also have a lense which we can control with muscles inside of our eyes? I didn't realize we could actually control the shape of the lense, now it makes a bit more sense to me.

You can until you become *ahem* annually challenged. At about 42 I noticed my eyesight was going to crap, now my arms are not long enough to read AND I can't see well at a distance. My eyes got stuck at about 20 feet with astigmatism sauce.

When you get old enough, your lens hardens, and you can't adjust it anymore. That's why you get presbyopia.

BTW, lenses are doing really nifty mathematical transforms with the images, if you delve deeply enough. At one time, the NRO had a crack team of Swiss lens crafters who worked in the basement and were thrown Brie and wine occasionally, their job was to grind lenses that could do math transforms on SAR data to turn it from a hologram looking muddle into a real image.

I'm not sure what you mean here, but your drawing at least is missing some details. First, you have a lens in there, and second you have essentially and aperture which is why your pupils get bigger/small under various light conditions. Don't forget that the signal that is received by the eye is not the same after its interpreted by your optical lobe. For example the image is flipped right side up inside your brain.

reply to post by boncho


Thanks for the resources, they are very helpful. The thing that made me think about this in the first place is due to the way I want to design this engine. Instead of light coming into the eye, I'm doing it the opposite way around, sending light from the eye and then drawing a picture based on what the photons collide with. Keeping in mind that a monitor is just an array of pixels, I basically need to send out a photon from each pixel and build up my image that way. Of course, sending the photons straight out parallel to each other would not work, you'd just get a zoomed in image of what ever it was in the distance that the photons ended up colliding with.

But thanks to your resources I now realize that each photon must travel through a single focal point, and the distance of that focal point from the origin point will determine how the camera is focused. What is brilliant about that is that it will create a completely natural depth-of-field effect. The only downside is that the focus of the camera will need to be manually adjusted, which could be troublesome if such an engine were to be used in a game (but then again, it's not like you can control the focus in any game which does have a depth-of-field effect). In any case, I'm still going to try it out and see how it looks.

I think that sounds like "ray tracing", have you looked at that yet?

Bedlam
I think that sounds like "ray tracing", have you looked at that yet?

I think it's more like path tracing than ray tracing, but I have a few new ideas I want to add to it.

I was inspired by this John Carmack lecture:

reply to post by defcon5


Not just light conditions

Your pupils also dilate when you are scared

Part of the fight or flight reflex caused by adrenalin

Cody

The simple answer is, you dont really have random light hitting your eye. Instead of thinking about the workings of the eye and the light rays as they are entering, think about the source. Each atom/molecule is like a tiny light bulb, the only light you see from that source is the light that travelled the shortest and most direct path, all other paths are at an angle. At that point is where the lens comes into play.

reply to post by ChaoticOrder


It's basically a property of how lenses work, and the position of your retina.

The only light that actually gets focussed on your retina, is the light that enters the lense from DIRECTLY AHEAD...

And light that enters the lense from an off angle, isn't refracted into your retina, it is refracted to a point beside, above, or below your retina.

Basically, the general angle that light enters the eye through the lense, is preserved, so that if light hits your lense from like, 60 degrees off center, it's going to hit the inside of your eye, at 60 degrees off center, as opposed to dead center, where your retina is.