Overlaying light beams by one replacing the other where they intersect

[Tom.G]

(trying to interrupt the ego storm here)

Just brainstorming. Another probably-not-ideal concept that might lead to other ideas or be modified for improvement.

How about if the static image is rear projected on a screen and the high resolution moving image is front projected, or vice versa? Perhaps the relative brightness of the two could be adjusted for a visually acceptable result. Even different polarizations might be useful somehow.

Addendum:
Further thought. Can the screen with the low resolution image be an LCD display with a partialy transparent front surface upon which the Hi-res image is projected? Then further projected onto a large conventional screen if needed.

 

[sophiecentaur]

(trying to interrupt the ego storm here)

Sorry about that.

Even different polarizations might be useful somehow.

Would that be better than just blanking out a slot in the LD image? Cross polarisation methods work well for some 3D video systems.

 

[wosoka]

How about if the static image is rear projected on a screen and the high resolution moving image is front projected, or vice versa? Perhaps the relative brightness of the two could be adjusted for a visually acceptable result. Even different polarizations might be useful somehow.

Go on. I don't understand what difference it will make to combine rear and front projection.
I can alo have them be different polarization, but not sure what to do with that either.

Further thought. Can the screen with the low resolution image be an LCD display with a partialy transparent front surface upon which the Hi-res image is projected? Then further projected onto a large conventional screen if needed.

What's an LCD with partially transparent front surface?

 

[Tom.G]

For the relative brightness, I was thinking that you want the Hi-res image to be the center of attention. Some ways of doing that are to make it brighter, higher contrast, higher color saturation, and as you are doing, higher resolution.

The polarization comment was just a brainstorm comment in case someone could usefully incorporate it.

What's an LCD with partially transparent front surface?

Not a commercial prodict that I am aware of. I was thinking in terms of the front surface being a half-silvered mirror (beam splitter style), or perhaps an overlay of matte surface Mylar film, or even a sparse coating of the glass beads used on an ordinary projection screen.

 

[wosoka]

hi-res image is not meant to be in the center of attention or standing out, quite the opposite, the brightness of foveal and peripheral displays have to be as close as possible to merge together as seamlessly as possible.
Your LCD approach is problematic the same way as projection because of low resolution not being enough to perform a good merging area with the hires area.

 

[Tom.G]

hi-res image is not meant to be in the center of attention or standing out, quite the opposite, the brightness of foveated and peripheral displays have to be as close as possible to merge together as seamlessly as possible.

Ahh! Another constraint. Since psycho-optic effects naturally draw attention to a Hi-res part of an image, I assumed this was a desired effect. The combinations I suggested were meant to concentrate the observers attention so that edge artifacts would be ignored.

p.s. The more information we have available, the fewer the blind alleys that will be traversed. I also recognize that business reasons can be a restraining factor.

 

[sophiecentaur]

brightness of foveal and peripheral displays have to be as close as possible to merge together as seamlessly as possible.

This can be controlled with feedback. From what you've written about the constraints, it seem clear that the transition between HD and LD regions needs to be monitored closely by, presumably, a sampling camera. For best results, the camera would follow the hd scanning mirror. Not a problem but another thing to be thinking about.
To make the transition as invisible as possible, it would help to low pass spatial filter the edges of the hd area so there is no obvious change in resolution. If you see a diagonal line which suddenly develops 'jaggies' as it passes from hd to ld region, it could be attention grabbing. A smooth transition from hd to ld would obviate this. My point has been, all along, that sophisticated processes like that can be done much more conveniently by DSP. I can see how, intuitively, a sharp transition that has higher resolution than the coarse ld pixels could be attractive but the details of that transition tend to make the actual method of slotting in irrelevant. There is the question of how sharp the edge of an opto-mechanical system would be. Could it even be of sub-ld pixel size? We don't know as we don't have a device yet.

 

[wosoka]

I know it can be controlled in software, I was just replying to Tom that it is not what we want (because he was suggesting how we can get that effect) but rather something we want to avoid instead.

All along you don't seem to understand that unlike in software you cannot cut a physical pixel in half or into a shape you want or add a gradient to a single physical pixel, all you can do with physical pixels is change their color or hide them.
I don't understand how many times I have to give the same example. I even told you, what you describe now, is done in merging the edges of similar resolution video projectors, because pixels are pretty much the same size. It's a common technique in video mapping called "edge blending". I've mention this before and now you talk like I don't know about it when I've literally talked about it myself here.
But here one pixel is considerably larger than the other. if you add a gradient/fade to 180 pixels in the hi res screen you will only be able to add that fade to 3 pixels in the low res screen. This does not make it smooth, no matter how much "DSP" you throw at it.
I'm sorry but this is going nowhere. You are repeating the same suggestion I have responded to.
I got the answer I needed from another forum:

Saturated absorber's are dyes, ceramics, glasses that bleach when a high illumination threshold is reached. Mainly used in pulsed lasers for mode locking or q-switching at enormous energies.

A crude example is eyeglasses that turn into sunglasses when UV moves /changes charge on a silver ion implanted in the glass. In fact that is probably the only example I can think of that has a decay time longer then a millisecond or so.

With the exception of the photochromic sunglasses, and the electrochromic window glass in development, everything else needs such high energy density to impractical to bleach with a mere diode laser...."Optical Limiting" is an area undergoing much research for the "Holy Grail" but you have either too slow, too fast, or too much energy. There is a major need for a glass that does what you want on the battlefield, in aviation, and for laser safety, but so far nothing easy or cheap or well suited has appeared. Some progress has been made in home /building windows, but the contrast ratio is low

There. What I want exists but has too low transition time or needs too much power.
Sadly there is no way of making the transition smoother other than making the foveal region bigger to make the transition area less noticeable, which is what some companies like Varjo are doing.
This definitely does not stop my research but concludes this topic as I'm aware of software methods of minimizing the noticeable seam and there is no point in discussing in physics forum about software algorithms anyway.

 

[sophiecentaur]

All along you don't seem to understand that unlike in software you cannot cut a physical pixel in half or into a shape you want or add a gradient to a single physical pixel, all you can do with physical pixels is change their color or hide them.

I understand the basics of sampling theory and that is what we are discussing. I am not suggesting doing anything to change the shapes of pixels and their fine positioning is not an issue. You are implying that the 'hole' would have transitions that are less than an LD pixel size and that positioning it could be positioned with a similar accuracy. That's a big ask and would involve a very expensive mechanical solution if it were even possible. The system I have suggested would have fewer moving parts and much lower requirements. Linearity would not be an issue either. The
If you are prepared to have an significant overlap around the HD portion, there can be a progressively weighted sum of HD and LD samples across the edge which can be made invisible. The pixel size is not relevant because the error need never be worse than the LD quality.
But, of course, this requires a tapered response for the opto mechanical gate which is another demand for your proposed system. This would be trivial if the hole were generated digitally in the LD image.
I think it's true to say that simple mechanical registration is unlikely to be easy to achieve to a high enough degree but that 'positional correction' of the HD image could be achieved relatively easily . Whatever the mechanical error is likely to be, the HD image position can be adjusted to put it in the right place. If the HD image is rectangular, the correction would be easier to achieve but an irregular cut-out shape or jitter would be much less visible. Again, this is something that could be achieved with software.
Your quote from another forum suggests that you should not hold your breath and I agree there will be a long wait before anything turns up - if ever. I guess there needs to be a number of possible well funded applications for the idea.

 

[wosoka]

I understand the basics of sampling theory and that is what we are discussing. I am not suggesting doing anything to change the shapes of pixels and their fine positioning is not an issue.

You are not but the way you suggest to do it digitally can only be done optically/physically by doing those steps. I tried to explain why but either I can't explain it as I've tried several times or I'm wrong, but you are yet to be able to explain to me how I'm wrong here as well, for because of the same one of two possible reasons.
Honestly, I would be glad to be proven wrong as it would make my life way easier to do this digitally, but from my persepctive and understanding you are repeating the same points I believe I have addressed several times by now, so this is going nowhere.

The system I have suggested would have fewer moving parts and much lower requirements.

It would have the exact same amount of moving parts, two steppers or galvos.

If you are prepared to have an significant overlap around the HD portion, there can be a progressively weighted sum of HD and LD samples across the edge which can be made invisible.

Again, I have addressed this. No matter how big the transition is the bigger pixels don't have enough resolution to not create a popping effect as a constantly changing gradient.
Have you even tried simulating this with photoshop? I know its not easy to create an animation in photoshop for this but I don't have time to make more animated illustrations myself either. If you claim the gradient is smooth then test it by creating an animation where a spot of the image which is constantly moving is 20x higher resolution then the rest of the image and has a transition with the low res section where the transition gradient resolution and steps is the resolution of the low res pixels (x20 times less). Save the animation, load it in fullscreen and try to follow that spot around with your eyes at 100mm distance from the screen. You will get an effect of a foveated display but your foveal view will be following the spot instead of the other way round. You will notice the gradient creating a "pixel" popping effect from the low resolution of the gradient fade.
If you don't have time to make an animation, well, so don't I.

But, of course, this requires a tapered response for the opto mechanical gate which is another demand for your proposed system. This would be trivial if the hole were generated digitally in the LD image.

My proposed system requires an optical (not mechanical) gate to form a black spot on the low resolution projector via a photochromic layer and an UV/IR beam which is overlayed with the visible spectrum high resolution projection beam via a dichroic mirror before they reach the galvo or stepper motor mirrors. There is no added mechanical parts, only optical.

Again we are going around circles as I have tried explaining all this numerous times already.

 

[sophiecentaur]

You are not but the way you suggest to do it digitally can only be done optically/physically by doing those steps. I tried to explain why but either I can't explain it as I've tried several times or I'm wrong, but you are yet to be able to explain to me how I'm wrong here as well, for because of the same one of two possible reasons.

Let's establish some basics about what the user is actually going to be presented with. I have never come across a video display that is intended to be viewed close enough for the pixels to be highly visible and I have to assume that the hd pixels will be low pass filtered to eliminate the sampling (pixels per cm) rate component. Yes, the LD pixels may be visible but even that is not necessary with the right display. So I assume we are dealing with two displays with different cutoff spatial frequencies and not with a load of little squares. It's very hard work to look at a pixellated display and actually, the detail in such a display is harder to see than than when the correct LP filtering is done.
Do you agree with that and/or do you understand what I am talking about? If you have any doubts about pixellated displays then just take good quality picture and zoom in till the pixels are visible. How would you describe he 'viewing experience' as you zoom out in small steps?

 

[berkeman]

Thread closed temporarily for Moderation...

 

[berkeman]

As I said once already,
we are not moving them digitally.
This is not comparable to a digital program like Photoshop that works with digital pixels and only when finished with the digital filters on the digital pixels converts the results to be viewed on fixed size physical pixels.
You are not merging two images with varying resolution digitally, but trying to merge two projected images in the real world with different, un-changeable resolutions.

Look,
https://i.imgur.com/X2o4l11.gif
Try to show how you can move the "small pixel" here smoothly instead of steps without creating gaps or overlaps.
Not only that, but as a small pixel moves into the space of one of the big pixels, the big pixel has to hide and its area filled with small pixels, again with specific positions and sizes.
No you can't add anything in between, because this isn't a digital program but illustration of "phsyical" pixels projected on a surface.Pot, kettle, black. You are not my mind reader nor am I yours. This has nothing to do with the topic, try sticking to it. I don't have time to read what you wrote to a straw man.
I just challenged your idea above. There, I wasted time making an animated illustration. Show me a solution to that and we'll call it a day, I'll even apologize for not seeing the solution sooner.Why do you think there is no way? because you have expertise in all aspects of this project? Just because you aren't aware of a solution means there isn't any? Do you see the irony? I literally just posted this and you completely ignored it and are making that statement:
Guess what? This wasn't my idea, someone from another forum suggested it. What did I do with his idea? Took it on board.

Thread will remain closed. The newbie OP has a 10-day vacation to reconsider how best to benefit from the PF.

Thank you everybody for trying your best to help the OP in this thread.