Re: Madtronix 3D Imager Calibration Issue

On Jun 11, 7:01 pm, vectrex...@xxxxxxxxxxx wrote:
By coincidence I am currently writing an article about the 3D imager
for publication in VGT, so am quite familiar with it.

I bought one of the first Madtronix imagers. I didn't get a
calibration wheel, and I've had numerous problems with the colour
wheels. John sent me a replacement set, since the first batches were
quite pale in colour. The second set was better but I still had a lot
of timing issues that were never completely resolved. I made the
mistake of messing with the sticker placement on my own. I'm a bit
embarrassed to ask John for another set of wheels to mess with.

The Vectrex FAQ (v6) describes at length some possible reasons, and makes
some suggestion for improvement, by stating that the user should sit
further back from the screen, and that ghosting can be reduced by
playing the game with a game overlay present.

My old writings come back to haunt me. :-) I wrote those sections of
the FAQ back in the mid 90's when the original imagers were treated as
mythical beasts, and in some ways they still are.

Finally, regarding the placement of stickers which are on different
places for the different colour wheels, it is hard to describe their
exact places in this message. When you say sticker positioned at the
very top, do you mean the centre of the black segmet on the colour
wheel?

Hmm. I'd have to look at John's original wheels. The thing is, I
believe John replicated the electronics of the original imager which
uses a transmissive scheme (ie, the IR beam goes through a hole in the
hub of the disk) while John's redesign uses a reflective setup (IR
beam is bounced off a sticker near the *circumference* of the disk)
that makes the placement of the sticker even more tricky. One of the
original problems with the imager redesign was the width of the
sticker (and thus the width of the square wave sent back to the
Vectrex for timing purposes). As John mentions in another post in the
thread, even a fraction of a millimeter off in placement or width and
the whole 3D effect and colour timing falls apart.

John has my complete sympathy with regards to these quality control
issues. It's a time consuming and sometime costly effort to rectify
these sorts of problems over the net. It's like trying to tell
someone how to fix a television over the phone with the possibility
they could electrocute themselves. :-)

Regards,
Rob S.

.

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