Seeing the Solar System in a New Dimension: Unlock the Mystery of 3-D Imaging
By Shana McAlexander
Product Developer, Carolina Biological Supply Company
Moviegoers are demanding more from their sensory experience, and 3-D viewing has become popular for many blockbusters. Unlocking the mystery of 3-D imaging not only spurs discussion about the greatest 3-D movies, but it also provides opportunity to discuss visual perception, optics, and colors with your students.
Children and adults alike are drawn to 3-D technology in entertainment, and the same technology can enhance scientific observations. Making red/blue 3-D viewing glasses and sharing 3-D images from NASA’s photo gallery will have your students seeing the earth and solar system in a whole new dimension.
What are 3-D images?
We tactilely experience our surroundings in 3 dimensions (3-D). When we hold a glass of water, we feel a height, a width, and a depth, but how do our eyes sense 3 dimensions?
The perception of depth is facilitated by our stereovision; because of the distance between them, each of our 2 eyes captures an image from a slightly different angle. Our stereovision informs the making of 3-D images. The various types of 3-D imaging technologies all rely on providing a different picture for each eye. The right eye must not see what the left eye sees, and the left eye must not see what the right eye sees. The brain is tricked into overlapping the view from each eye to form a composite image that appears 3-D.
You can demonstrate the different perspective of each eye by holding a finger in front of your nose and viewing it first with 1 eye closed and then the other. As you open and close your eye, it will appear that your finger is moving. The closer the object is to your eyes, the greater the difference between the images from the right and left eye. When viewing a scene with both eyes, the brain overlaps (superimposes) the 2 images to yield a single image that appears to have depth.
Demonstrating depth perception
Individuals with low vision or no vision in 1 eye generally have difficulty with depth perception. You can demonstrate the ability to perceive depth with the following exercise. First, hold your arms out in front of you with your index fingers pointing toward each other. With both eyes open, bring your fingers together slowly until they touch. Now, try the same thing with only 1 eye open. Most people find it more challenging to bring their fingers into alignment when using only 1 eye.
Capturing the image
Most 3-D images are captured from 2 slightly different perspectives to mimic the stereovision of the eyes. In the making of a 3-D still image, there may be 2 adjacent camera lenses in 1 camera or 2 photos taken from a few inches apart. Likewise, in 3-D video, 2 camera feeds are processed post-filming to create a 3-D image. Alternatively, some computer software is designed to shift 1 image digitally so that it appears to be taken from a different angle.
3 types of 3-D
Stereo image pairs
Using stereo images to create a 3-D image is the most basic technique. Two images taken from slightly different points of view can be placed side by side. If one stares at the images while cross-eyed, thus hiding the right image from the left eye and hiding the left image from the right eye, the superimposed image appears in 3-D in the middle of the field of view. Devices are available to help facilitate this effect, but it can be achieved without assistance. Maintaining a cross-eyed view may lead to eyestrain and headache, and, if students try this, they quickly realize the inconvenience of watching an entire movie this way.
Here is an example of a stereo image pair taken by the SPOT satellite of Great Rift Valley in Kenya.
Source: SPOT Stereo Images
Remember that the key to seeing images in 3-D is to provide a different image to each eye. Anaglyph images present 2 offset, superimposed pictures, each in a different color, most often, chromatic opposites such as red and cyan. Wearing glasses with 2 different-colored lenses then allows 1 image to be seen through the red filter and the other through the cyan filter. The brain fuses the input from each eye, and the viewer perceives a 3-D image. You can make a class set of anaglyph viewing glasses by following these instructions.
Here is an example of an anaglyph with red and cyan images taken from the Mars Pathfinder landing site. Through red/cyan glasses, the image appears black and white. The red image is observed through the red filter as black, and the cyan (blue) image is observed through the cyan filter as black.
Click on image to enlarge.
PIA00995: The Twin Peaks in 3-D, as Viewed by the Mars Pathfinder IMP Camera
Here are anaglyphs of the sun taken from the Solar and Heliospheric Observatory (SOHO) spacecraft.
Click on image to enlarge.
©NASA, STEREO Graphics Gallery
You may have noticed that maintaining the original colors of photographs becomes a challenge when using the color anaglyph method. To deliver separate images to each eye without using colored filters, a new method was developed using polarized filters. Most of the current 3-D glasses offered at movie theaters have clear, polarized lenses. Students may be familiar with polarized sunglasses, which reduce glare by letting light enter from only 1 direction. The lenses of 3-D glasses are oppositely polarized so that one image is visible by the left eye and another image is visible by the right eye. Special video projector filters and screens are required to send the light in the correct direction. For a 3-D movie, there may be 2 projectors casting superimposed images on the screen or 1 projector alternating left and right images so quickly that the brain does not notice.
Find these and additional 3-D images at the following Web sites: