Aligning and Affixing Your Parallax Barrier

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Alignment with the Identical Grid Pattern on the Panel:

First, we generate the pinhole grid for the iPhone 6 screen size. It is simply a grid of horizontal and vertical lines which are both 4 pixel thick and separated apart by 5 pixels. Equivalently, we set every 5th element in both row and column to 1 using the MATLAB code below:

iphone6_testPattern = zeros(1334,750);
iphone6_testPattern(3:5:1334,3:5:750) = 255;
imwrite(iphone6_testPattern, 'iphone6_testPattern.png');

Now, with the test pattern being displayed on the screen, place the printed pinhole mask over it. Translate and rotate the mask slowly while using the moire magnification as the guide [1]:

Displaying the same Pinhole Grid Pattern on the Display Panel allows for easy Alignment of the Pinhole Mask using Moire Magnification.

Relative pitch/orientation of the pinhole mask determine the scaling/rotation of the magnified dotted grid. When perfectly aligned and in the optimum viewing zone, we would see a single large pixel with iPhone 6 sub-pixel arrangment as shown earlier at one angle and dark from all other viewpoints. If you move your head out of the head box, the views will start to repeat and hence you will see  Here, we see a wide bright spot .

Testing with Distinct Views’ Interlaced Image:

The quality of the parallax barrier and its alignment with the super-pixels will manifest itself in the visibility of 5 distinct views in the horizontal and vertical directions and the seamless transition between these views. And the easiest way to test it is to display the interlaced numbers’ sequence with 5 base images.

Interlaced 5 Base Images of a Numbers’ Sequence shows 5 Distinct views via Motion Parallax

Interlaced 5 Base Images of a Numbers’ Sequence shows 5 Distinct views via Motion Parallax

Affixing the Parallax Barrier:

Acrylic spacer described earlier in the “What Will You Need” section serves two purposes. It both helps in

  1. Adjusting the Field of View of the pinholes and hence determining the spacing between the virtual cameras to capture our synthetic scene, and also in
  2. Helping affix our pinhole mask securely on to the iPhone screen. You do this by first sandwiching the mask between the two spacers and hot gluing the corners. Then we stick the spacers to the screen using the double sided tape on the rear spacer when the proper alignment is verified as described above.

Once the mask has been affixed on to the iPhone screen, the capacitive screen would become inoperable through touch. Hence you can use a bluetooth game controller or a keyboard as the input device to your iOS app while it is running.


Now we’re ready to move on to creating and running your iOS app.

References:

[1] Hirsch, M., Lanman, D., Wetzstein, G., Raskar, R. “Construction and Calibration of LCD-based Multi-Layer Light Field Displays”. OSA Int. Symposium on Display Holography 2012.

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