StereopsisIntroduction to Computational and Biological Vision

Final project by

Andrey Trushkin,Irena Farberov.

Introduction

Stereovision :

Each eye captures its own view and the two separate images are sent on to the brain for processing. When the two images arrive simultaneously in the back of the brain, they are united into one picture. The mind combines the two images by matching up the similarities and adding in the small differences. The small differences between the two images add up to a big difference in the final picture! The combined image is more than the sum of its parts. It is a three-dimensional stereo picture.

The word "stereo" comes from the Greek word "stereos" which means firm or solid. With stereo vision you see an object as solid in three spatial dimensions--width, height and depth--or x, y and z. It is the added perception of the depth dimension that makes stereo vision so rich and special.

Two Eyes = Two Separate Views!

How the stereogram becomes: a subject photograph from two different points located on distance of 6 cm from each other (6 cm - approximate distance between eyes of the person), and then consider the received pictures in a stereoscope. Though at viewing each eye sees only one picture, a human brain, on a habit, combines two images and, in aggregate, sees a volume picture. All is very simple; and that seemed yesterday surprising, today hardly will cause interest at spoilt by three-dimensional games and a drawing of the computer public. So we thought in that way, until we have suddenly beheld the image of the dragon who has stepped directly from the screen!

Seen so has interested, that, not losing time, we have begun to "scan" the Internet, trying to discover everything, as to stereo-grams. The opened world has amazed! It has appeared, that the stereo-image can be received by simple means; it is literally on an empty place!

The person sees world around volume. Therefore quite natural desire is the desire to embody this world such what it is - having not only width and height, but also depth.Basically, it is not difficult. The subject is perceived volume because we look at it two eyes. To receive the stereo image it is enough to remove its two cameras, or one camera from two positions corresponding to positions of the left and right eye, or the special device with two objectives.Complexities arise when we will want to see the stereo image removed thus. For this purpose it is necessary, that each eye would see the image intended for it, and did not see the image for other eye. Without special training of an eye at the person look, as a rule, how it is offered to them the nature, instead of the volume image see two flat.How to manage to see the world image such, as well as the world - three-dimensional? The

very first, that comes to mind - to learn eyes to look at stereo images a little differently, than

on a flat picture. After some training it is possible to force to see the left eye one image, and

right another.

Viewing of stereo photosWay 1Draw near closely the picture centre so that to concern with its tip of a nose. Not changing focusing of eyes, be removed gradually from it while instead of two will not see three pictures. Central will have stereo effect. Way 2Fence off pictures from each other a sheet of paper so that each eye saw only one image.

Application of stereogramsWhether there is an advantage of stereo pictures?At first sight, stereo images seem absolutely useless toys. But it is far not so. It appears, stereograms even are useful to health! For those who spends all the days long behind the computer, having fixed stopped eyes in one point of the screen, viewing of stereo grams offers fine warm-up for eyes. Features of stereo grams force eyes to change a habitual point of focusing, thereby saving up our sight. It is rather useful to consider stereo images. Not superfluous even to establish on the computer stereo wall-paper and from time to time to turn a look to them.

Looking at stereo pictures - in itself pleasant pastime, however entertainments in the stereo world on it are not settled. You can play in plain stereo game. Game suggests to wander on a three-dimensional labyrinth

Mathematics studying! Spatial stereo-images of geometrical figures allow to present better their structure, and strict principles of construction - to develop mathematical abilities.

Use of stereo-images on web pages Despite all specificity of a stereo-drawing, it is quite possible to think up to it practical

application. For example, stereo-banners. It is possible to decorate with stereo-images and usual web page to think up three-dimensional background drawing, an emblem .

Goals of our project:

We want to receive the stereo image from two regular pictures

The program should identify three-dimensional subjects

Examining the influence of different factors to received stereo picture.

Design of our Program

This program was implemented with Dot.Net for Windows.

Processing Stages

• Loading the pictures

• Generate disparity map

• Generate depth map

• Smooth with Gaussian

• 3D Preview

Examples and Results:

Simpsons

Results:

Example 2:

Example3:

Results:

Conclusions

The algorithm is very successful on artificial pictures.

Success on recognizing shape from random noise

It is very sensitive to deviation in the epipolar line, issue that common in real photos.

Real photos are never correct :

it is impossible to set the cameras exactly in the same angle

in each camera the objects are differently pushed into pixels

many other problems like color correction on digital cameras.

That fact make real images extremely difficult to recognize.

References:

en.wikipedia.org/wiki/Stereopsis www.vision3d.com

www.lessons4living.com/free.htm

http://www.knowdotnet.com/articles/examplesandtutorial.html

Ohad Ben Shahar, - Lectures on "Introduction to Computational and Biological Vision", BGU computer science department

Vishvjit S.Nalwa:”A Guided Tour of Computer Vision”

Christopher Brown: “Advances in Computer Vision “