Fwd: Re: cheap-shit laser displays

Subject: Re: cheap-shit laser displays
From: Danny Ayers <[email protected]>
To: Kragen Javier Sitaker <[email protected]>
Cc: [email protected]

On 8 July 2010 09:37, Kragen Javier Sitaker <[email protected]> wrote:

> 12kHz is a horizontal scan on a 320×200 60Hz-refresh display; 28.8kHz
> is a horizontal scan on a 640×480 60Hz-refresh display. The
> newly-fashionable 16:9 aspect ratio gives you more screen space than
> 4:3 for the same number of horizontal scans; 1024×600 is the same
> number of pixels as 900×680, but at a 12% lower horizontal scanning
> frequency. You could carry this much further, e.g. with a 8:3 or 16:3
> aspect ratio.
>
> The cones of cheap dynamic earphones can move hundreds of microns at,
> I hope, tens of kilohertz.

I would imagine so - many earphones can give reasonable response at
10kHz+. My guess though is that the deflection would be significantly
non-linear. There should also be some advantage here in driving the
scan with a sine wave, I believe it would reduce the 'bounce' of
overtones a sawtooth would create. Although it may turn out to be
straightforward to compensate for non-linearity using analog and/or
physical components, I suspect there may be advantages in doing a lot
of this this digitally. For example, a crude (but fastish) 1 bit D/A
converter followed by an analog resonant filter, with extra damping on
the moving parts might be combinable to provide an accurate scan
curve.

Cheers,
Danny.

-- 
http://danny.ayers.name

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