Logitech Bluetooth Cordless Presenter Review

securitas writes "Many Bluetooth devices have (deservedly) received dismal reviews and we were prepared for the phaser-like Bluetooth Logitech Cordless Presenter to be another toy headed for the trash-heap of history. Instead we were surprised (some might say stunned :) ) at how well it performed. The Presenter combines a laser pointer, an electronic presentation remote control and a wireless optical mouse in one elegantly designed package."

Comments

$200!!!

[kwerle]

Damn, the keyspan USB remote is just $79.

Re:$200!!!

[ivan256]

The review says that the reciever is keyed to the device and the device to the reciever. In other words, you need to use a USB port for this thing even if you already have bluetooth support.

How it worked.

[wowbagger]

The zapper worked exactly like a light pen works.

Oh, you don't know how a lightpen works.

A CRT based screen "paints" the image by scanning an electron beam over the display surface. The graphics chip that generates the display knows where the beam is at any time (it has to, since it has to know what pixels to be sending out.)

The light pen (or gun) is a lens that focuses the display down to a point on a fast image sensor (typically a phototransistor). So, when the electron beam paints the part of the screen that the pen/gun is focuses on, the photosensor fires.

This signal is tied back to the graphics controller, which says "AHA! the electron beam is at 234x421 when the sensor fires. I'll record that into these registers".

After that, it is simplicity itself to set up a cursor.

Now, that technique won't work for a liquid crystal display, since they aren't "scanned" in the conventional sense - there is no pulse of light as the system writes the data to the LCD. Therefor, there is no way a light pen or light gun could work on an LCD display like a modern projector.

Now, in theory you could use a camera to sense a laser pointer's spot, and then move the pointer there. But then you would need a fairly high resolution camera, plus a calibration proceedure so the system would know what points on the camera corrisponded to what points on the display. You would also need a fairly narrow band filter to allow the camera (once calibrated) to see only the laser pointer spot - otherwise it might respond to other objects on the display.