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Hong Kong: 100 hours community service for shining lasers at police

A 37-year-old bank manager was sentenced July 23 2020 to 100 hours of community service for aiming laser beams at vehicles and officers at a Hong Kong police station on January 1 2020. The incident did not appear to be connected to protests against police which occurred in Hong Kong during 2019.

Kwok Fu-wah was said to have aimed the lasers "out of impulse". The incident interfered with police duties but there were no injuries reported.

He was originally charged with possessing offensive weapons in a public place which is punishable by imprisonment. However, prosecutors allowed him to plead guilty to "a diminished charge of similar nature" resulting in the lesser sentence of community service. The principal magistrate noted Kwok had a good background and was sorry for his actions.

His two laser pointers were examined by police, who said the "two devices could cause ocular damage if the eyes were directly exposed to the laser beam within 60 meters [200 feet]."

From the South China Morning Post


The 60 meter "ocular damage" distance probably refers to the laser's Nominal Ocular Hazard Distance. For a handheld laser with a typical beam of 1 milliradian beam spread, this corresponds to a laser of roughly 70 milliwatts. (The laser color would not be a factor in injury, only the power and divergence.)

In many countries the legal limit for a laser pointer is 1 mW; in the U.S. pointers of up to 5 mW are allowed to be sold.

A NOHD of 60 meters does not mean that injury will occur at that distance. As explained elsewhere, there is a safety or reduction factor built into the NOHD. At around 20 meters (66 feet), a 70 mW 1 mrad beam with a nominal 1/4 second exposure could cause the smallest detectable change in the retina about half the time, under laboratory conditions. Beyond 20 meters the chance of injury becomes even less until at the 60 meter NOHD it is considered an allowable exposure.

A one-quarter second exposure is used in the laser safety field for cases of accidental or unwanted beams. A person will blink, move or otherwise avoid eye exposure the laser light within that time.

The distance from Kwok to the police officers was not stated in the article.