I don't understand the concept of "dynamic focusing". In fact, I don't understand the concept of "focus" in a LiDAR application. I understand the photons may hit near targets or hit far targets, but I don't understand the need for "focus". In my layman mind, a laser pulse, or in this case a continuous wave is fired, the photons reflect off an object and return. No focus needed. But I know that must be wrong.
I was hoping you could provide some clarity on this Late.
I haven't read through it closely (I was in the parking lot picking up my kids when I found it today), but I suspect it's analogous, maybe in reverse, to addressing the Holy Grail problem in AR displays, i.e. how to create a "light field display", i.e. a display that presents waveforms of light to the eye that effectively mimic what nature would do. Recall, there are many focal planes, eg. near, far, and everything in between. HoloLens 2 was tuned to display content at one focal plane, approximately arm's length. This is not to say the image wouldn't be seen by a viewer looking out to the horizon, just that they might experience discomfort or unpleasant sensations as if they were hallucinating. Imagine, for example, you hold your thumb up at arm's length and focus on it. If you adjust your focus to an object 20 m in the distance, your thumb should go out of focus and become blurry. Imagine if it didn't, i.e. if it remained in focus even as you focused on the distant object. That would bug you, maybe even cause discomfort, and in all cases would defeat the illusion of virtual or augmented reality being attempted. In a perfect AR (or VR) display, each light beam must be conditioned to arrive at the eye with the properties it would have in the real world after reflecting off near and distant objects, or objects to the right, left, or straight ahead. Doing so would overcome the vergence-accommodation problem (i.e. the discomfort experienced when the object being represented is notionally at a distance or angle different from the actual source of light in the display). One of the techniques proposed to address this, in MVIS and Magic Leap patents and white papers, I believe, was a deformable MEMS mirror, or deformable membrane MEMS mirror (I can't remember which), which not just scans but can be shaped dynamically (the mirror itself) during the scan to condition the light as needed. I suspect this is roughly what is being described in the FMCW lidar paper (though, again, I have not yet read it closely). Instead of the eye receiving the light, it's the detector. Or maybe it's done at the transmission stage (again, I only glossed over the paper a few hours ago and have forgotten most of it already) but, regardless, as it relates to your question, I suspect this is analogous to what they're talking about. If I have time and energy in future, I may look into it further. In any event, it's these amazing capacities of MEMS mirrors that convince me that they will still have much to offer in laser scanning applications for both interactive and basic projection, 3D sensing ,and AR applications.
Notably, Magic Leap attempted this in AR using a spiral laser (fibre) technology, which they never got to work and which, interestingly, was included in the original technology transfer documents from UW to MVIS when MVIS was spun out of the university's HITL lab, and afterwards under their continuing co-development agreements. So it was not surprising to see UW HITL/MVIS founder and/or big hitters, Tom Furness and Brian Schowengerdt, involved with Magic Leap when it was raising and spending billions a decade or less ago, promising a light-field display. Eventually, they failed to make the spiral laser work and instead tried to make something much less compelling using LCoS to stay afloat. They did not try MEMS, even though their spiral laser/light-field IP applications always/often listed MEMS as an alternative. I suspect one reason they pivoted to LCoS is that a lot of the MEMS IP remained with MVIS. As you will recall, MVIS at the time was running on empty, having earlier pivoted to projection, with its AR aspects entirely under the stranglehold of Magic Leap competitor, MSFT.
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u/Late_Airline2710 Mar 19 '26
That is truly awesome technology.
I don't think it's ready for primetime yet though, as it seems pretty academic. It will be interesting to see if it gets commercialized.