Of all the things Magic Leap has done, I consider Fiber Scanning Displays (FSD) to the “The Big Con”. The reason why is that Magic Leap made such a big deal about it being one of their “core technologies” early on, so many people today are that it will work, and yet is it so easy, with 4th-grade math, to prove it is impossible. Fiber Scanning Display” is still showing up in 33 Magic Leap patent applications published in 2017
That anybody would promote that FSD could support the resolution required was incredibly naive/ignorant and/or incredibly corrupt. It also would seem to show, hard as it is to believe with all big money involved, that nobody was looking at Magic Leap in serious technical detail. Maybe they were just “big picture” people who didn’t sully themselves with 4th-grade math.
It has said that “a good con must be believable.” In the case of FSD, the University Washington HID Lab in the mid early to mid-2000’s had shown they could make a low resolution highly distorted FSD projector with a fiber projector and they had papers and patents being published ever since.
So the con goes something like, “it is just a matter of improvements, “Moore’s Law”, and scaling up right?” . . . Wrong, as you scale up the resolution, the fiber has to move impossibly fast. As I showed in a previous article, even at lower resolution/speeds is the image highly distorted and non-very non-uniform in intensity.
One Web Calculation and 4th Grade Math
There is a one piece of semi-complex math that is solved by doing an online search for a “roll length calculator,” of which there are many, such as on Handymath. Working from Ivan Yeoh’s 2015 Ph.D. dissertation (the best and most recently available information on FSD), he had 180 spirals which would nominally be 360 pixels across the circle at the equator of the image with only a 50Hz frame rate. This still ignores the Nyquist re-sampling from a grid to the spiral.
Starting with 360 pixels across in 1 mm or 1mm/36 = ~0.00278mm per loop. Now scale this up to 1080p (1920 by 1080 pixels), requires 1080 loops to give an inscribed 1920 x 1080 pixels image.
Using the coiled rope web calculation (inputs and results show below), plugging in 0.00278 mm which gives a ~6mm (=0.00278x1080x2) diameter coil to give 1080 turns. The path length (of the tip) works out to about 10.17 meters (see below) whereas for the Yeoh paper with only 180 loops and a nominal 360 pixel across the circle, the length was only ~0.26 meters and still they dropped down to a flickering 50Hz just to do that.
To prevent flicker with a zero persistence display, you really should have a refresh rate of about 120Hz (and not 50Hz or even 60Hz). And since there is one out and one back for each complete “scan” that hits the outer rim only once, this means you it must go the path length of the spiral 240 times a second to “hit” the center and outer most pixel 120 times a second.
Thus the fiber needs go 10.17 meters X 240/sec = 2,400 meters/sec. For reference, the speed of sound is a mere ~343 meters per second (varies with temp and air density) so the fiber has to average about 7 times the speed of sound and because it is accelerating and decelerating back to zero at each end, it has to have a peak velocity of greater than 14 times the speed of sound!!!!!
If this is not insane enough, they need an optical (clear) fiber that will move at the resonate frequency required, while driving it all contained in a near perfect vacuum so whatever it is won’t spontaneously combust due to air friction along with the sonic boom destroying the users hearing. Not to mention turning the user’s brain to Jell-O from the vibration. And if you find this miraculous material, it must also follow an exact uniform path particularly at the center as is passes through zero and reverses or else the pixels will not be in the right place and/or wiggle.
You can play with my assumptions above and plug in different numbers, but you can’t come up with any rational way to make it even come close. There is nothing in any of Magic Leap’s or the University of Washington’s papers or patents that show how it could be scaled up as much as 720p not less 1080p effective resolution.
Now For The Sad Part of this Story – Were Is the “Smart Money?”
What gets me is that with all the “very smart” people and those with all that money that reviewed the Magic Leap investment, this “little problem” should have been quickly discovered. Magic Leap’s whole credibility should have been gone back then.
Just about every person at Magic Leap with math, engineering, and/or science degree must know by now that FSD is a crock. And still, the myth is still being perpetuated that FSD will work and Magic Leap is still filing patents like FSD will exist (to support the myth or fool investors?). Of course, not of Magic Leap’s patents or papers deals with the speed of the “magic” fiber.
And this is not the only things that are downright silly in their patents. The whole depth planes concept also falls apart as I discussed last time; to support the six focus planes the dream about in their patents, they would need a stack of 6 x 3 = 18 waveguides with even more insane optical routing.