Journal
Saturday, May 17, 2008
¥ Finally, it's time to revise all my journal entries and my report. As I revise this, I feel that my web pages have started to look much better now. During the past week and after my finals, I have been working on revising my webpage. It seemed like a tremenduous work at first, but now everything seems to be working out, probably because I have much more knowledge of HTML now. I also feel that putting work of my entire semester onto a page diminishes the value of the efforts. It was still worth going through this because I learned about some things about my own eyes that I always wanted to learn about.Tuesday, May 6, 2008
¥ Today, I presented for the WISE 187 class. I couldn't believe how fast I talked today during the presentation. First, there was no laser, so in order to describe each surface, I had to use many words, rather than just point to it. Second, the time limit was 12 minutes and beyond that time points were going to be taken off. I also found out after the presentation that my presentation was exactly 12 minutes. Third, there were so many important and astonishing facts that I wanted describe, I felt that without talking fast I wouldn't be able to describe all these facts thoroughly. Overall, it was a fun experience. The other presentations were also very informative and exciting.Wednesday, April 30, 2008
¥ Today's undergraduate research celebration was excellent. I loved being at the URECA celebration where I saw many new faces and some known faces. It was interesting the way people were asking questions about my project and always related to defects of their own eyes. Most of the people, though, were very interested in the optical demostrations, such as the 3D glasses, Pig-toy, etc. It was still fun explaining how I started the project and how I got through learning about BEAM2 project without a Manual.Wednesday, April 30, 2008
¥ 1:10 in the morning!!!! I finally finished my project and settled on the issue of scraping out the glue from the poster. Now that everything was glued and perfect, I can look at it in the morning with a happy face.Thursday, April 24, 2008
¥ A normal eyeModels to put on the poster:
Hypothetical ball
Hypothetical ball with corneal bulge
Hypothetical ball with corneal bulge and crystalline lens, two shapes of crystalline lens
-far away object focusing onto retina
-close object focusing onto retina
Different corneal surfaces
Tuesday, April 22, 2008
¥ Ten Facts about Eyes:- No one has a perfect vision, not even those with 20/20 vision. The Snellen eye chart determines the ratio of the normal eye vision to the patient�s eye visio
n - The normal eye with 20/20 vision is called an Emmetropic eye
- Two thirds of the focusing power of the eye comes from the curved entrance surface (the cornea). The remainder comes from a crystalline structure called the crystalline lens
- The visual acuity is measured in Diopters
- Myopia usually occurs in younger children where children can clearly see near objects yet unable to focus distant objects.
- Hyperopia, a common defect within adults, is a condition where one is unable to clearly see nearby objects yet is able to focus objects that are further away.
- Older people lose the ability to change the focus of the eye (accommodate). This condition is called presbyopia.
- More than 98% of the world is affected by aberrations, deviation of rays from expected path
- Astigmatism, one of the types of aberrations, is the different focusing power in different planes
- Different objective tests to measure the visual acuity include direct ophthalmoscope, keratometry and Retinoscope
Thursday, April 17, 2008
¥
a) A normal Eye b) Another view of normal eye c)Hyperopic eye (far-sighted) d)Myopic eye(near-sighted)
Thursday, April 17, 2008
Here is a list of things that I thought should go on the poster.
I also thought about some illustrations that could accompany the poster.
-Using obstruction such as a finger when the light rays are passing
to show that the image on the retina is on the other side of the retina
-Pass a pin between the eye and a pin hole in a card, then another
image of the pin is seen coming in the opposite direction
-Look through two pin holes spaced less than the diameter of the
pupil, and focus on distant point past a needle a few inches away. Two
images of the needle are seen and covering the right-hand pin hole causes
the left image to disappear - observe what happens with a normal,
farsighted and nearsighted person.
Tuesday, April 8, 2008
¥ Here are some fascinating facts about human eyeball as it grows from infancy to puberty.
Thursday, March 27, 2008
¥ I was reading through the Optics book "Handbook of Optics" today, and the book explained some of the topics that I have been always wondering about. I found the chapter that deals with the vision corrections and what causes the different aberrations in eyes. The description of presbyopia is so much in detail here. They say that the refraction pattern in the cylindrical lens of the eyes causes presbyopia. I am writing very little of what I learned today. I am writing because I learned a lesson that if I want to master this I need to teach.
The most interesting part: I found out how the doctors assign numbers to the eyes. Myopic(near sighted) patients who have the focal length in front of the retina have the corrective lens with diverging property and they assign the negative value to it. The number that we are assigned has the unit (D) that is inverse of the meter and it has to do with where the focal point of our eyes is. The dioptic power(optical power of the spectacle) is the inverse of the focal length. I also found out that if myopic people, like me, do get a presbyopia then they can simply remove their myopic corrective lenses and get a good vision. For the far sighted people the value assigned to the lens is positive because the lens has to be converging to bring the focal point from the back of the eye on to the retina.
I also found out how the aberrations in our eyes step up in a polynomial function, mainly described by Zernike polynomials. The easiest corrections to make are the first orde ones, the tilt, then the defocus and astigmatism and then the spherical and axial. After a certain point, irregular aberrations are observed for which they have no defined description.
Which means that higher the polynomial order gets, the harder it gets to make the corrections for those. Since I have spherical aberrations, and almost no tilt, I have difficulty getting lenses because they have not yet found a way to create those corrective lenses.
The other interesting part I found was that, even the people with 20/20 vision have some irregular aberrations in their eyes. Even those people can't see perfectly.
The larger the pupil diameter is, the better the vision gets, with maximum possible diameter as 8 mm. The best example showed in the book was looking at statue of liberty from a distance about 5 km or looking at a standing quarter 5 feet away from it. People with perfect vision plus the corrective lenses added to reduce the irregular aberrations can see the statue clearly, but not sharp. However those with 8 mm diameter can see the picture sharply.
Tuesday, March 25, 2008
¥ First time using the ray tracing program without a manual! We created a new file with no hints of what should go in each row. Finally, solved that issue but then couldn't figure out why the eye just didn't look like a circle. Before coming to a circle, it went through many forms, as parboliod, inverted two half circle, circle with lines coming out of its top and bottom. But finally through some guesses and checks, It looked like a circle, (potentially sphere). At last, we couldn't solve how to put the screen in there, but finally just changin one number resolved even that issue. And Here is the Work:
This image is a simulation of eye ball as a water droplet(index of
refraction close to the eyeball). This inner cylindrical lens adds a
corrective factor so that the focus point of the rays is the back of
retina for a normal eye.
Tuesday, March 11, 2008
¥ Today, I attended a lecture about quantum entanglement. It was given by Joe Eberly, a highly regarded optical physicist from the University of Rochester. At first, he talked about the superposition of images. Consider a cube drawn in 3D, then there exists two cubes with different orientation in the same image. Stare at one square and make that a front face of the cube, then stare at the other square and make that a front face of the cube.[Book Reference] I found this really interesting because in the next slide he put two cubes together and asked us if we could see both orientation at the same time. Afterwards, I started losing him and couldn't understand what he was talking about. In order to probe Bell's Inequality, he showed that "cos^2(theta) > cos(theta)" which we know isn't true. After that I was completely lost with phi, theta and x.
Tuesday, March 4, 2008
¥ Today, in laserlab, we decided to go to the lecture by Robert Panoff, an accomplished condensed matter physicist. It was entitled "Many Body for Anybody." The purpose of this lecture was to bring out an awareness of computational thinking. Many programs involving thousands of computations are designed such that they would assist students in understanding phenomena, whether it is a physics, math or biology related. The projects are developed by programmers to encourage students to make inquiries while they perform experiments. These representationsof physics and other sciences through interactive simulation excite more students to invent something innovative. Rather than a simple sentence in a textbook, these programs simulate those sentences into something that can be viewed in an animation. It was very interesting to find out the opportunities in the programming field since my major is computer science.
Manushi ShahFebruary 2008