| MadSci Network: Physics |
Hi,
Thank you for your question. It is certainly an interesting thought, using an array of lasers to create a television. That said, there are two ways of considering this question:
As you explain in your idea, the crux is that you have to be able to tune the frequency of the laser. The problem for me is that I do not know over what range you have to tune the laser. You see, normally, laser light is extremely monochromatic (i.e. has only one color): a laser with wavelength of 500 nm can easily have a spread in wavelengths of one in a thousand nm [1]. Visible light, by the way, is between 390 and 700 nm [2]. This probably means that we need to be able to change the very precisely defined laser wavelength by quite a bit.
Tunable lasers do indeed exist [3, 4, 5, 6]. To do so, generally, mirrors or prisms are shifted so the wavelength can be modified. The information I could find is a bit sparse, but they seem rather expensive and not wieldy. I do remember when I did research, changing the frequency of our dye laser would be a day job - and for your television, you'd need to do that about 100,000 times per second (number of lines in the display multiplied with a decent refresh rate). A large grid of them (about 3000 for a regular HD television) would be needed.
Present-day laser-televisions [7] work in a way more similar to old-fashioned cathode ray televisions [8]. They use three different lasers (a red one, a green one and a blue one) to create a combination that is perceived by our eyes to be the color intended. This works because our eyes perceive color using cones that are sensitive to three different color spectra. lor using cones that are sensitive to three different color spectra.
To give you a different perspective, consider plasma televisions [8]. Plasma televisions work by creating a very small plasma that ignites a pixel. If you go into a store, they look just fine - their image quality is gnenerally as good or better as that of an LCD. Their big downside is the fact that they use a lot of power, which heats up the room and is expensive. For this very prosaic reason, they are becoming a niche product. By the way, lasers are typically quite power-hungry.
On the balance, I think that it would quite a challenge to create an image based on this principle. It would be worth considering wheter using three lasers with a fixed frequency is easier than a single, tuneable laser.
Cheers,
Bart
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