iLight is a system that supports collaboration over real-world objects, even when a user is not in the same physical location. The iLight uses an aligned camera and video projector  that allows a user to draw on a video image of a real-world scene using digital ink. The drawn marks are projected onto the scene, and are visible to remote users through the video image, as well as to local users in the vicinity of the projector.
Block diagram

iLight GUI
The iLight GUI is shown  at left. The real-world scene is visible in a live video image.

For example, consider a shared whiteboard. The iLight system uses a bright video projector to “draw” images on a local whiteboard, while transmitting a video image of the whiteboard to remote users. In operation, remote users draw on the camera image with familiar graphical tools such as rectangles and free-form (digital) pens, while local users draw directly on the whiteboard using physical (dry-erase) pens. The remotely drawn images are then projected onto the whiteboard. and will be visible to all in the local vicinity, while the local pen markings (as well as the projected drawings) are visible to the remote user through the video image.

iLight has several novel features. An "image copy" tool allows selected regions of the video image to be cut and pasted. Thus hand-drawn figures may be copied and pasted as if they were digital. Additionally, photos or other digital images may be dragged onto the iLight GUI, where they are then projected, and may be moved, copied, or otherwise manipulated.
For use with three-dimensional objects, our colleagues at jPAL in Nakai, Japan have developed an optical system that removes parallax using the half-silvered mirror arrangement shown at right. This removes parallax by aligning the camera's center of projection with that of the projector so that figures projected at any distance from the system will be aligned (unlike simpler systems where the camera is offset from the projector). We have also developed a custom-designed projector lens with substantially greater depth of field -- images remain in focus over a range of more than 20cm ( an order of magnitude greater than conventional projectors).

Here's a scenario that illustrates how a remote expert could assist a telecommuter without the expense of a “house call.” An employee working from home is having difficulty with a printer in their home office. By directing the iLight system at the troublesome device, a support staffer can remotely inspect the printer, and then indicate where and how to manipulate the device. Over a voice channel the expert learns that the home worker needs to change the print cartridge, but does not know the procedure. From the iLight image, the expert can determine the make and model of the printer, and indicate how the printer may be opened (top). The telecommuter can then take the suggested action to reveal the ink cartridge inside. If it is not obvious, the expert can highlight its location by drawing a white rectangle over it (center). This indicates the desired location even though the object is both irregular and poorly reflecting. With this assistance from the remote expert, the telecommuter is able to successfully locate and replace the cartridge (at bottom).
Example ilight scenario

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