New type of CD design for better audio?

Hello everyone, I'm new here so please be easy on me. I had an idea one day while working. What if you could use a certain optical disk to make analogue sounds? It would work like this: Every optical hobbyist knows that if you hook up a headphone jack to a laser and a sound source you can modulate the laser. Now if you add a solar cell or a solar resistor to a headphone jack and plug it into the speakers and shine the laser at it, it will make a sound. That's how almost how CD lasers work I think except they store compression data instead without modulating it. Now say you had some sort of disk that using a modulated laser could basically burn analogue sound to it almost like what a magnet does to magnetic tape using the effect explained earlier. Could you could produce new vinyl record sound without the wear down that plagues the records and led it to it's doom? Or would it be just another failed project?

Yep! - another failed project.

CDs don't work like that, the audio isn't impresed into the disk like it is in vinyl, the sound is first sampled at a high rate, in the case of CDs it's normally 44100 times per second, then the samples are turned into digits, then a compression algorithm is used to optimize the signal to noise ratio and finally the bits in the data are saved to the disk as long or short length pits. The disc writable layer is not capable of direct analog recording.

What *might* work is an optical pickup on vinyl records but special care would be needed because on a normal record deck, the stylus tip is responsible for moving the whole arm assembly. An optical system would need servo motors to maintain tracking.

Brian.

I think there may have been some player for vinyl that used a laser, but I may be wrong. Anyway, it's safe to say that
analog audio recording and playback has had it's day a long time ago ; )
What is slightly sad is that still 16-bit is the standard for CD audio, 24-bit would be nice : )
And the few SACDs that there are for artists I would pay for, are hugely expensive Japanese imported disks : (

Laser turntable

http://en.wikipedia.org/wiki/Laser_turntable

http://www.elpj.com/

DIY :
http://www.youtube.com/watch?v=TRhAa4qaJPk

Laser Turntable in action :
http://www.youtube.com/watch?v=v0_uEQp2Vg8

I love that slightly retro/industrial look. I've decided my next home project has to look like a retro hi-fi!

Use laser protecting goggles to protect eyes.



Safety :
http://www.caa.co.uk/docs/49/Alesa%20card%20web.pdf

Could I use light sensative paper covered in fixer Between 2 dark plastic plates with a laser shining through it but using the laser first to etch it in without fixer?

Of course, laser beam and laser beam dot is not good for watching.

Even small 5mW cheap chinese laser pointer dot is not good for watching.

I'm not so sure the sandwich of light-sensitive paper would be much better than the old movie film reels that had the strip of analog audio running alongside the movie images. It uses variable width, but I'm guessing they must have experimented with variable brightness in those days too. I think it would not be high quality, but if you were curious maybe some research into the old film reel audio methods may be a good way to go.

If you really want to go down the analog laser route, you must first decide how you are going to store the audio. Modulating the laser intensity probably wont work because they have very limited operating current range and their light output per mA is highly non-linear. Also setting the optimum 'exposure' level on the medum would be very dificult and again it would likely be non-linear. This is the very reason why the width of the light track rather than it's transmissiveness was used on celuloid movies. Don't forget also that you need two of everything to record in stereo, an analog track can only carry one channel of audio at a time.

What might be interesting as an experiment, but would take many hours to get resuls, would be to make a holographic recording. I did some experiments with HeNe lasers about 35 years ago and had some success at making holographic photographs, it would be interesting to try recording images of vinyl records in 3D and see if the groove could be reproduced in high enough resolution to recover it's shape and hence audio. Not something to try at home though - unless you have a very tolerant partner!

Brian.