Use an optical mouse, on the end of your finger, and point at the screen.
The mouse looks at that part of the screen and transmits the image to the computer. The computer matches the correct part of the image to the image from the mouse, and that's where you are pointing.
With different optics, it could work in combination with a laser pointer if users were some distance away from a screen.
How would it work on a single colour area? Would it need to do this? Micro-coding could be superimposed on an otherwise blank area to help with this, if required.
-- Ling, Nov 01 2004

For non-believers http://www.epanoram...ts/pc/lightpen.html
Description of guns and light pens [Ling, Nov 04 2004]

Why video screens flash when the gun trigger is pulled http://www.howstuff...com/question273.htm
[Ling, Nov 04 2004]

My old Dragon 32 microcomputer had a light pen with software that worked pretty much like this. To select from a menu, you pointed the pen at the appropriate flashing block, and the software matched the input to the serial port with the block that was flashing at that instant.
With this version, how large an area does the mouse see? What are the chances of that pattern of pixels appearing somewhere else on the screen?
-- angel, Nov 01 2004


[angel], that's going back some time....
Of course, related technology is the humble playstation gun, which detects the refresh on the CRT display.
//how large an area does the mouse see?//
Hmm.. if it is big, it effectively reduces the working point from the edge of the screen. If it is small, then every pixel looks just like every other pixel. The centre of the image would be the mouse "point". I suppose it would probably be around the size of a typical icon. Maybe a bit bigger.
-- Ling, Nov 01 2004


[angel] wow. dragon.. I remember them, I must've been 8.
-- neilp, Nov 01 2004


Although I like this idea, I'm not sure I'd really like to use it. My mouse hand is quite comfortable resting on my desk. Having to point at the screen would require my having to raise and support my arm in mid-air. Surely this would quickly become tiresome?
-- Gordon Comstock, Nov 01 2004


Old technology: The way this used to work was timing. The sensor on the light pen was activated only when the beam scanned under it. So, the system could tell exactly where the tip of the pen was at all times. It didn't need to recognize shapes or anything. (I had a couple years experience with this twenty years ago, using the IBM Fastdraft system. It had a one MEGAbyte CPU driving two B&W workstations. All for just $100,000!)
-- ldischler, Nov 01 2004


I'm not sure if TFT displays are scanned like the CRT displays.
-- Ling, Nov 02 2004


[Gordon Comstock] if your arm gets tired attach to the end of one's nose.
-- benfrost, Nov 02 2004


What if you did not have to hold anything in your hand (or on your finger), but had a couple of tiny cameras mounted near the screen. The camera (on looking vertically, the other horizontally), could track your finger and figure where you were pointing - optically. Then you would not have to wield a device to point - the screen would be the optical mouse. They have this technology working for Playstation games, should be easy to implement for a computer.
-- trekbody, Nov 02 2004


<pointing at bun icon>
-- 2 fries shy of a happy meal, Nov 03 2004


I think this is baked by a vid game gun
-- -----, Nov 04 2004


For all those that think that this is the same as a gun, or a light pen, please see the link - particularly the bottom paragraph.
-- Ling, Nov 04 2004



random, halfbakery