I Reference Resources
The calculation refers to the first part of GB7247.1-2001 safety standards of laser products, including equipment classification, requirements and user guides. The term laser used in this standard includes LED (light-emitting diode) at all times.
II Noun interpretations
Maximum Permissible Exposure (MPE): the laser radiation level at which human eyes will not have adverse consequences under normal circumstances.
Nominal Ocular Hazard Distance (NOHD): the distance at which the beam irradiance or irradiation amount is equal to MPE of the corresponding cornea.
Intrabeam viewing: the eyes are exposed to laser radiation to look at the laser beam.
III Computing Methods
The illuminator adopts laser wavelength λ= 808 nm, output power P = 2 W, illumination angle 15-45 degrees.
The corresponding MPE can be found in table 6 of GB7247.1-2001. It is at the intersection of the wavelength range of 700 ~ 1050 nm and the emission duration of 10-3～10 seconds. C4 and C6 can be calculated by the formula given in the notes to tables 1 to 4 with intrabeam viewing. The maximum permissible irradiance is EMPE=29.6 W/m.
(1) When the beam divergence angle is 15°, the outgoing beam diameter (reference emission aperture) a = 30mm = 0.03m. NOHD=1m with atmospheric attenuation ignored.
(2) When the beam divergence angle is 45°, the outgoing beam diameter (reference emission aperture) a = 30mm = 0.03m. NOHD=0.3m with atmospheric attenuation ignored.
According to the above calculation, when laser divergence angle is at the maximum angle of 45 °, the safety distance to human eyes is 0.3m away from the laser emission point. When the laser divergence angle is at the minimum angle of 15 °, the safety distance to human eyes is 1m away from the laser emission point. It can be seen that the laser safety distance is 1m away. Considering the atmospheric attenuation of the laser, the corresponding NOHD value should be reduced.
In addition, the laser used in the laser camera by our company adopts light intensity homogenization treatment, which weakens the collimation of the laser beam. Unlike the conventional untreated laser beam, its safety is higher than the above calculation results.
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