Stereoscopic Images

SUMMARY

1. Bibliography 3

1.1 What is a stereoscopic image? 3

1.2 how to get a stereoscopic pair 4

1.3 historical review of stereo photographs 6

1.4 Stereoscopic image manipulation techniques 7

1.4.1 A block-based method 8

1.4.2 A hybrid method 9

2. Multiplexing stereoscopic images 11

2.1 problem statement 11

2.2 principles 11

2.3 filtering and multiplexing 12

2.4 implementation and test of different filters 14

2.4.1 How to test the results 14

2.4.2 Anaglyph image 14

2.4.3 Test of different filters 15

2.4.3.1 A narrow Gaussian filter 15

2.4.3.2 Gaussian filter 18

2.4.3.3 a square-shape filter 20

3. Research of an efficient coding method of the multiplexed stereoscopic pair 23

3.1. JPEG 23

3.2. Optimized JPEG 26

3.3. Is it worth coding using JPEG or JPEG-like coding? 29

4. Annex 30

4.1 JPEG coding 30

4.2 code to construct anaglyph 31

4.3 code to multiplex 32

4.4 code to demultiplex 35

4.5 useful function used in multiplex and demultiplex 36

4.6 anaglyph made from the two original images 38

4.7 references 39

1. Bibliography

1.1 What is a stereoscopic image?

Everyone knows what a stereo sound meansÐŽ¦ but few are those who know what a stereoscopic sound is.

Left image right image

ÐŽoStereoscopicÐŽ± is derived from stereo, which is a prefix meaning to put something in relief and scope which means to see. Stereoscopic means to see in relief.

A stereo sound is made of two sounds, one for the right ear and the other one is for the left ear. The same is true for the images. A stereoscopic is made of two images. One is seen by the left eye, and another one is seen by the right eye. Thus we use a pair of stereoscopic images.

In fact the pair of stereoscopic images is what our brain receives. Then it is analysed and a single image is build, a 3 dimension image. The purpose of the project is to underline how to synthesis those images and how to manipulate. WeЎЇll try to put the pair into a single image, as the brain. An image made of a pair could not be seen properly without any optical object, such as glasses.

1.2 how to get a stereoscopic pair

The effect is to duplicate the spacing of our eyes that gives us stereo vision. Although it's possible to take a pair of stereo images with a single camera and lens, it's not the easiest way and the results are somewhat unpredictable. It's important that the lenses be the same focal length, exactly parallel, and offset by just the right amount—called the stereo base distance. For this reason, special cameras are usually used.

The Argus 3D Stereo Camera uses 35mm film. It has 2 matched 28mm lenses, 2 apertures (daylight and flash), and 1 shutter speed so everything is in focus from 2 1/2 feet to infinity. It also has a built-in pop-up flash.

If you don't have a special camera, you can experiment using the one you do have.

1. Create a guide that helps you move the camera 2.5" between shots and also keep the lens aligned so it's parallel. Just take a flat board and put a small wooden rail on it. When you slide the camera along the rail from flush-left to flush right, the lens moves exactly 2.5 inches. You can even add hardware to mount the base to your tripod

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2. Select a scene where nothing is moving—not even clouds or leaves in the wind. Be sure to include something in the foreground to give you a stereo effect. (A shot of distant mountains won't have any.) Generally, a 35mm camera with a 35mm lens can handle a depth range from 2 meters (7 feet) to infinity. Photographs taken that only include objects in this depth range will view perfectly well in any viewing device. Here are some guidelines for other scenes:

• If a foreground object is as close as 5 feet, objects more than 20 feet away must be excluded.

• If a foreground object is as close as 3 feet, objects more than ten feet away must be excluded.

3. Use a level to keep the camera level between shots. 4. Set the camera to a small f-stop for maximum depth-of-field. 5. Use the same exposure for both pictures. An alternative approach is to buy two disposable cameras and tape them together. You might want to tape them to a board or tripod so they don't move or learn how to press both shutter releases together.

The problem with most stereo cameras is that they are based on old technology. There really isn't a high-quality modern 3D camera at a reasonable price. There are small firms that couple cameras together so you can take stereo images using modern equipment with autoexposure, auto focus, and so on. It's possible to couple two digital cameras in this same way. This eliminates the need to get film scanned to display it on the Web.

David Grenewetzki rigged two Kodak DC20 cameras to produce digital stereo pairs. Believe it or not he does this from remote control airplanes. There are lots more details on his Web site. Courtesy of David Grenewetzki

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