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On Tue, Feb 22, 2000 at 01:46:37AM -0000, Peter Pachla wrote: I really like the Sun "Starfire" concept. It's very pie-in-the-sky at this point... but basically you sit in front of a giant screen whose lower 18" is horizontal, like a desk, and curves upwards and inwards like a baseball backstop. The entire thing is a touchscreen and scanner also; any paper you lay on the surface becomes an electronic document with no further intervention. You can work on the horizontal surface to reduce arm fatigue but also drag reference materials or large windows of other kinds up onto the vertical part of the display. So it would seem to be the best of both worlds (vertical monitor for easy reading, combined with a horizontal work surface like a drafting table). This was never built of course, they did a "video prototype". I've seen the video once but it has become available retail so I ordered a copy to see it again. Once wireless touchscreen "web pads" become more commonplace we may see people using those to operate a big-screen display remotely; the pad can display user-interface elements while the big-screen shows what you're actually working on. You can position it however it's most comfortable. There have been a variety of touchscreen and pen type devices over the years. The most common ones now are the resistive and capacitive types; both involve a film coating over the CRT. With the resistive one, there are two layers with some kind of grid of transparent resistive traces; and the pressure of your finger causes them to come into more intimate contact, lowering the resistance between the two traces which cross at that point. The resistance is proportional to the pressure, and this is handy in some applications. With the capacitive type, the presence of your finger changes the capacitance and this gets detected, but these screens are not pressure-sensitive. You can also use a stylus that has a similar effect on the capacitance, but not a hard-tipped one. There is also the Surface Acoustic Wave (SAW) variety, which (I think) somehow uses ultrasound to detect very slight deformations in the glass as you press your finger against it; this type is also pressure-sensitive. There have been infrared beam touchscreens but those tend to be lower-resolution. It detects your finger breaking a pair of crossing beams. And of course there's the old lightpen trick. There is a hardware register somewhere which has a pointer to the VRAM memory location where the color value for the current dot (or character) being painted is coming from; so when the pen detects that the phosphor dot under it has just been lit up by the electron gun, simply go check that pointer to determine what the coordinates of that dot are. I imagine high-persistence phosphors probably interfere with the ability of this method to work very well. And there is another kind of touchscreen that is simply a base that you set a conventional monitor on. I believe it detects a force differential between several strain gauges; as you push on the screen, the weight distribution on the base changes in proportion to where you're pushing and how hard. But it's been a while since I've seen material on this kind and I've never seen an actual unit. I'd bet the calibration would be somewhat finicky. For use with a stylus, the additional options are RF-based. Some of them require the stylus (or puck, in the case of a digitizing board) to be powered and emitting a low-power radio signal. It's picked up by a criss-crossing grid of circuit board traces behind the screen, which act as antennae, and the signal strength gives it a clue to where the pen is located. An advantage of this method is that you can move the cursor without physical contact. My Dauphin DTR-1 uses this type of digitizer, and I can move the cursor with the pen up to 1/2" or so away The disadvantage is that the pen must be powered, with batteries in the case of the DTR-1 or else tethered to the machine in other cases. There are also RF-type pens that are passive; the machine emits RF and the pen acts as a transponder to relay it back. My IBM 730T Thinkpad uses an unpowered type of pen but I haven't opened it up to see if the detector is just a grid of circuit board traces or something more. I believe the Newton and other practical PDAs like the Palm probably use resistive screens, because they work with your finger as well as the stylus (but with less precision), and the stylus is just a chunk of plastic. -- _______ http://www.bigfoot.com/~ecloud (_ | |_) ecloud(a)bigfoot.com finger rutledge(a)cx47646-a.phnx1.az.home.com __) | | \__________________________________________________________________