Lenses vs Mirror (refraction vs reflection)

suggestions

#1

Here’s an idea:
What would be the pro’s/cons to using mirrors instead of lenses?

pros:
Mirrors are easier to work with and you can shape them any way you desire.
Mirrors absorb less light
Mirrors are less prone to distortion, provided that the surface they’re painted on in rigid enough. And distortion can be minimized by shaping the mirror painting surface.
There is no need for a sweet spot because the entire mirror is the sweet spot.
Mirrors are easier to move for focus and IPD.
Mirrors can be treated easier for anti-glare, blue and red light filter, etc…
The front of the headset would be lighter by placing the OLED panels towards the back, front, side, w/e.
Easier to implement a mirror using smaller (tiny) mirrors that can be moved back and forth to enable multi-focus scenes.
Easier to manufacture,

cons:
The OLED screens can’t be in front of the face.
More prone to scratching and breaking upon impact.
The silver reflective paint may flake over time.

Anyone else has an idea?


#2

Hum if you look at the North Star project from leap motion you will see that using reflector instead of lens comes with his own set of problems, specially for large FOV headsets. Also creating ellipsoidal reflectors is not a so easy task… direct eyes projection is a alternative where micro mirrors could be used like in DLP projectors

http://blog.leapmotion.com/northstar/

If you’re talking about using mirrors without any magnification or lens in the optical path please explain your concept because I don’t see how this is possible …


#3

Mirrors do the same thing as lenses . Mirrors can both magnify and focus. The difference is that one reflects while the other refracts.

Mirrors are easier to work with and shape. I’m not sure what you’re referring to when you say crating “creating ellipsoidal reflectors is [sic] not a so easy task.”

A mirror is simply a reflective surface painted onto a sturdy surface. Glass is often used, but is not the only base.


#4

Quality mirror with no aberration are not so easily done, the ellipsoidal mirror use for AR ( could be for VR) must be made using precision industrial tools with optic quality requirement did you look at the link a provided?


#5

I didn’t look at the link, but I will now. :smiley:

But the same can be said for lenses.


#6

Mirrors are not magic, they also have aberrations albeit different kinds than lenses.

In (amateur) astronomy it is neverending debate “lens vs mirror” and general consensus is good lens is better but for large diameters lenses are too expensive or not possible at all. So up to ~10-15cm most people prefer lenses and then mirror/hybrid territory begins.

Still, things might be different in budget territory which is what we have. But if mirror was really advantage on budget then I suppose some HMD’s would use it. Problem with mirrors might be construction/design related more than quality related - you would need to reflect from the sides (as the screens can’t be behind head) and this will make the geometry complicated - similar (probably more severe) to what we face with parallel projections with Pimax.


#7

How about what google glass did, they had some sort of plastic with the mirrored screen inside it


#8

Using miroirs complexify the placement of the optics especially for large FOV headsets. Just look at the North Star project how the lateral view is contrain by the placement of the panels on the headset.

The information screen on google glasses was small… if you want to look at alternatives for big VR lens direct retinal project is the deal …

Not sure I would try the first beta :sunglasses:


#9

I remember before flatscreens were available that some people had camera doorbells with a flat monitor in the house. It was actually a sort of projector onto a curved surface which produced a ‘flat’ screen.

I will try to illustrate it because I couldn’t find a google image for it.

So the projector has a certain squished version of the final image that corelates to the curve in the projector screen. I imagine something like that could be used to wrap the image around someones head and then addition lenses would be used to get it all in focus like we do now


#10

Probably not unlike the new near wall laser projetors

Only required to shrink 2 of them on a prescription glasses frame :sunglasses:


#11

Haha, hey I wasn’t being practical here, this is the wild west after all


#12

More seriously is that you still have some kind of micro array required to form the image micro mirrors or lcd. Then things begin to get complicated vs a simple lcd + lens concept