Experiment
We assemble the basic SLI set-up consisting of a projector and a camera. The projector is used to project a light pattern, which can be a single stripe on a target surface. By measuring the distortion between the captured and reflected image, the depth information can be extracted. This technique can be useful for imaging and acquiring three-dimensional information.
We used the gray code representation as our pattern. In the gray code, the numbers are represented as binary patterns and the consecutive numbers differ by only one bit position as shown in Table 1. The gray code structured light patterns we set up in class are shown in Figure 1.
Table 1. Binary code and Gray code representation
Figure 1. Gray code structure light patterns for the different binary patterns projected onto a white background (IPL whiteboard).
Figure 2. Gray code structure light patterns projected on a pyramid
We determine the stripe ordinals by recombining the different stripe codes. The binarized images are multiplied by their corresponding bit weights and are added to form the image and background bit stacks. Note that each vertical line in the bit stack represents a unique number. Using the depth from disparity equation, we were able to determine the surface depth or height of our pyramid.
Figure 3. Reconstruction I. The pyramid object is reconstructed using the SLI technique.
Figure 4. Reconstruction II. The Matlab command, medfilt2 was used to lessen the other stray peaks present in the reconstructed figure.
Tips:
1. Make sure that the background and object binarized images are multiplied by their corresponding bit weights in the gray code. I did not obtain good results during the early parts of the activity because I inadvertently switched the two background images and their gray codes.
We were able to successfully reconstruct the surface of our pyramid using the structured light illumination technique. I give myself a grade 0f 10 for this activity.
References:
[1]. M. Soriano, " Activity 8: 3D reconstruction from structured light" Physics 305 Lectures, 2009.
For teaching concerns please visit: https://sites.google.com/site/alongjas/
We used the gray code representation as our pattern. In the gray code, the numbers are represented as binary patterns and the consecutive numbers differ by only one bit position as shown in Table 1. The gray code structured light patterns we set up in class are shown in Figure 1.
Table 1. Binary code and Gray code representation
Figure 1. Gray code structure light patterns for the different binary patterns projected onto a white background (IPL whiteboard).
Figure 2. Gray code structure light patterns projected on a pyramid
We determine the stripe ordinals by recombining the different stripe codes. The binarized images are multiplied by their corresponding bit weights and are added to form the image and background bit stacks. Note that each vertical line in the bit stack represents a unique number. Using the depth from disparity equation, we were able to determine the surface depth or height of our pyramid.
Figure 4. Reconstruction II. The Matlab command, medfilt2 was used to lessen the other stray peaks present in the reconstructed figure.
Tips:
1. Make sure that the background and object binarized images are multiplied by their corresponding bit weights in the gray code. I did not obtain good results during the early parts of the activity because I inadvertently switched the two background images and their gray codes.
We were able to successfully reconstruct the surface of our pyramid using the structured light illumination technique. I give myself a grade 0f 10 for this activity.
References:
[1]. M. Soriano, " Activity 8: 3D reconstruction from structured light" Physics 305 Lectures, 2009.
For teaching concerns please visit: https://sites.google.com/site/alongjas/
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