A Pennsylvania inventor has developed a laser-based device that surpasses the traditional canes used by the blind to feel their way through the world. Nazir A. Ali, president and founder of Nurion-Raycal in Paoli, said that he has sold more than 400 of the $2990 LaserCanes and that there is a long waiting list of people wanting to purchase one.The LaserCane employs diode lasers directed upward, forward and downward, and gated detectors monitor the returning light. Reflected light from the upward or forward channels indicates an obstacle. The absence of reflected light from the downward channel indicates a drop-off. Toward the top of the cane, three sequentially fired diode lasers emit beams upward, straight ahead and downward. The duration of their pulses is typically 150 ns, and the repetition rate is 80 Hz. Farther down the cane, three gated detectors measure the laser light that is reflected from the surroundings. A return signal from the upward-directed beam indicates the presence of a tree branch or other overhanging obstacle. The absence of a return signal from the downward-directed beam indicates a curb or other drop-off ahead, because the detector is located beneath the laser on the cane. And the presence or absence of a return signal from the straight-ahead beam allows the user to steer between obstacles.The LaserCane probes the user's surroundings with laser light. The LaserCane communicates with the user by emitting audible signals that indicate which detectors are receiving a return signal or by producing vibrations on the side of the cane that are felt with a finger. The latter technique takes advantage of a Braille reader's practiced tactile sensitivity.Ali has been working on the LaserCane since the 1970s. He originally employed infrared technology, but when inexpensive diode lasers became available, he was quick to adopt them. Until recently, he and Earl J. Bennett, a product designer who has played an integral role in developing the device, have been hand-making the canes one at a time. They have begun an alliance with a New Jersey company that will mass-produce them.