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Laser Displays

Discussion in 'Projectors, Screens & Video Processors' started by buns, Jul 5, 2003.

  1. buns

    buns
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    starting to get bored
     
  2. nathan_silly

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    I was thinking this would be smart- using a laser pointer on screen, and pressing a button will select that button (ie like a light gun, but you can see where you're pointing to)

    It'll make DVD menu navigation alot easier and & faster.
     
  3. buns

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    i think you have taken me incorrectly...... this is a totally different technology...... no lcd displays...... the lasers map the image. I'll go and get the avs link.

    It has great potential i would have thought because (ssuming a reliable blue laser) the rgb would be highly coherent making for very pure colours and it should also be very good for fine tuning.

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  4. buns

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  5. nathan_silly

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    Read it.. don't like the idea of a laser Rear Projection!

    And I have to agree with that one bloke, if it's way beyond reach for 10 years then it's pretty much irreverent until it drops down in price to £1000-£5000.
     
  6. buns

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    Well i dont think it should be that far away..... in 10 years we should be using screens which roll up and need no projector!

    this technology surely is dependent on the maturity of blue lasers which isnt 10 years away.

    They will need to rename the whole thing though...... people see lasers as things from star trek which burn and kill!

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  7. calibos

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    You mean Light emitting polymer (LEP)screens buns?

    I haven't read the thread and I'm assuming the lasers wouldn't be very powerful but is even a low power laser safe. Would the beam coming from the lense be as bright as a laser pen/pointer because even those are supposed to be dangerous to the eyes. You never know though. The new heads up displays the American military are developing (micro laser paints image directly onto the retina) might filter down to the consumer electronics arena and we wont even need a screen. We'll all have our own personal 200inch screen. (as opposed to our own 50in screens with the current LCD eye glasses technology).

    I'm off to read that thread now!
     
  8. buns

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    frankly i think it would be a bad idea to look straight into a bulb projector! There is that potential for danger, but if these things are truly near to production then it will surely have been considered.

    what intrigues me most is why Alan Gouger isnt commenting...... is it all just hype...... or is it so good that they dont want to say until they sell off all their other machines!

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  9. Anders_UK

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    I have worked with Laser projectors for around 2 years now, and I have to say the picture quality is brilliant, mainly due to the intense colour saturation, however it does have its drawbacks, both optical performance (halo effect), safety, power consumption, space and cost.

    Not to used in the home I don't think. We have installed them on various simulators and in several planetariums, so it is reliable and fairly mature.
     
  10. buns

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    Anders,

    Why would you think then that AV specialists are keeping so quiet about this? Is it at all possible that someone has come up with a technique of circumventing the issues you mention?

    Also, how come power consumption is an issue? Solid state lasers which i would have encountered would be dramatically more efficient than any other device we would use in the lad.

    Good to hear from someone in the field

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  11. Marcus Wood

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    I wouldn't have thought safety would be an issue. Relatively crude laser 'projectors' have been commonly used in nightclubs for a long time. I mean the things that are used to draw shapes with lines of light, presumably using servoed mirrors.

    And what about the lasers in supermarket check-outs?

    Presumably the factor in damaging your eyes would be the density of light output (i.e. lumens per square metre at a particular distance). I would have thought this would need to be the same for a laser projector as for a conventional projector with the same apparent brightness.
     
  12. buns

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    Marcus,

    What you refer to is the intensity..... im fairly sure that the fact that the light is 'laser' is irrelevant! Laser if simply referring to the manner in which the light is produced. The result has the potential to be intense simply because of the propertied of the beam in which light is produced. So if you looked straight at a standard light source at an intensity the same as a given laser, both would cause similar damage (though im sure there is slight interpretation to someone more medically minded).

    What im long windedly saying is that im certain the machines will not be of any significant health risk

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  13. calibos

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    I wonder will refresh rates become a bigger issue again? In that this new tech draws/scans the image much like a crt tv.

    It'll be like sitting between the electron gun of your tv set and looking at the back of the screen!!
     
  14. buns

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    i dont know how the scanning and whatever for crt works, but lasers tend to have very good temporal responses, i suspect that the laser response will be limited by external circuitry

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  15. Anders_UK

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    It is very much the same path taken yes. i.e. top left to bottom right.

    The system I am fairly familiar with has quite a large laser generator where the white laser is then split to its prime RGB, using a similar techniques to 3 chip LCD and DLP PJ's. It is also where the image processing takes place. However it can power up to 3 display heads..with more channels being added all the time. The laser then travels down optical cable to the tiny light weight projection head. (see hear ...http://www.schneider-ag.de/)

    This is the system I have worked with and installed on various projects. The perfect solution to kack CRT's and naff black levels, just a tad expensive!!
     
  16. Mr_Belowski

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    White laser? Perhaps my physics is a little rusty, but isn't that, er, impossible? As laser light is produced by electrons moving between energy levels (like I said, my physics is very rusty ;)), the wavelength is fixed. That is, a laser emits light at a single wavelength.

    And white light contains a mixture of, well, all wavelengths I suppose.

    Wouldn't you need three separate lasers (pure R G and B) to do this?
     
  17. buns

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    likewise, i would consider a white laser as a contradiction

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  18. gothmog

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    I guess a 'White' laser in this case would be a single laser that uses a mixture of three gasses that emit a pure Red, Green and Blue simultaneously. So not strictly 'white' in the physics sense, but kinda white ;)

    Cheaper than having 3 lasers I'd imagine ;)

    --Jon
     
  19. John_N

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    Agreed. There is no such thing as a _solid_state_ white laser. Lasers operate in exactly the manner you describe with electrons falling between energy levels.

    In the same manner, there is no such thing as a white LED. A white LED works by using a single wavelength emitter to excite a phosphor. There is usual a Gallium Nitride based diode and an InGaN active layer.

    One version combines a blue LED with a yellow phosphor that generates white light by mixing blue with the yellow light emitted by the phosphor. The combination of an ultraviolet LED with red, blue and green phosphors generates white light, just as fluorescent lamps do. Ultraviolet light excites the phosphors to generate visible light.

    This method is fine for white LEDs but the light generated is incoherent and this technique thefore is not suitable for white laser production.

    HOWEVER

    I think you may be able to get a white gas laser by using mixed gas like Argon and Krypton mix, in order to get emission of red, green and blue in roughly equal proportions through the same laser head. In other words, we have a laser tube that outputs mixed red, green and blue laser light that our eyes perceive as white. These lasers are bigger & bulkier than solid state lasers and the laser tube needs cooling (air or water) and a high running voltage and a very high starting voltage. This is why I suspect a white laser will be bulky and consume a lot of power.

    J


    J
     
  20. buns

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    well a laser can work in many ways..... electroluminiscence is the future of things.

    Personally i would be very surprised by the use of pumped lasers, they are really not good for this, the efficiency is terrible also. Addmitedly this sort of thing has been about for sometime, but any excitement for us should be limited to a solid state laser solution.

    the avs thread is starting to puzzle me on the actual state of play..... i can think of half a dozen relatively simple techniques of using solid states for projection..... someone out there must have thought about it too!

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  21. John_N

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    Errrr. Hang on a second. :)

    All lasers work on similar principle. They definitely do not use any principle of electroluminescence or using a phosphor. The nature of the physics means that you can not control the precise nature of the emission and therefore you do not end of with coherent light which is the secret of a laser. You do not get any amplification using a phosphor or an electroluminescent media.

    All lasers are pumped.

    A laser consists of at least three components:

    1. A gain medium that can amplify light that passes through it
    2. an energy pump source to create a population inversion in the gain medium
    3. two mirrors that form a resonator cavity

    The gain medium can be solid, liquid, or gas and the pump source can be an electrical discharge, a flashlamp, or another laser. The specific components of a laser vary depending on the gain medium and whether the laser is operated continuously (cw) or pulsed.

    Semiconductor lasers are light-emitting diodes within a resonator cavity that is formed either on the surfaces of the diode or externally. An electric current passing through the diode produces light emission when electrons and holes recombine at the p-n junction. Because of the small size of the active medium, the laser output is very divergent and requires special optics to produce a good beam shape. This is one of the reasons why you can still see the output from a laser pointer if you are not staring at the beam.

    Sure you could use 3 solid state lasers in a projection display device. The difficulty being in creating solid state green lasers (at the moment, green lasers can be produced by using a laser diode and an ND:YV04 crystal as a freqency doubler which is not terribly efficient). Bue lasers of reasonable power are also still difficult.

    Just remember though that there is no such thing as a free lunch. If we try to scan a laser spot like a CRT on a screen and modulate it to make an image, the entire image will not be as bright as the laser spot is when stationary. This is impossible. The power per unit area of the beam would reduce proportionally. This means that for a bright image, you would have a pretty powerful laser scanning across the screen. Multiply this by three for each colour and you have an eyesight hazard.

    Laser light is particularly damaging because of the high intensity of the beam due to the fact that the beam acts as an illuminator with a small solid angle and a particularly pure frequency that your eyes are not designed to cope with. Your eyes aer less sensitive to some colours than others (red for example) and hence you can easily view a red laser which will damage your eyes because you are not perceiving it as being very bright when in fact there is a lot of energy in the beam.
     

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