# Laser line safety

I'm a researcher at University Federal of Santa Catarina Brazil and I work with lasers.

I'm looking for information about how to calculate the Nominal Ocular Hazard Distance (NOHD) to a laser line and not to a laser point.

I have a laser line with 150 mW, thickness 1,14 mm with working distance 5m and fan angle 30°. Link

I would like to know the Nominal Ocular Hazard Distance (NOHD) with application to this laser line.

• NOHD is not a physics concept. Commented Oct 16, 2020 at 2:51
• @G.Smith thanks for the excellent contribution, helped a lot, keep the hard work! Commented Oct 19, 2020 at 18:12
• @Pedro77 The Code of Conduct here says “Avoid sarcasm”. Commented Oct 19, 2020 at 18:56

Assuming this is a CW laser operating between 400nm-700nm:

$$E$$ (our irradiance) is taken to be the MPE (maximum permissible exposure) of a Class 2 laser: $$1.8T^{-0.25} \times 10^{-3} \text{ watts/cm}^2$$

Our NOHD will be:

$$D_{\text{NOHD}}=\frac{\phi}{w\times\theta\frac{\pi}{180}\times1.8T^{-0.25} \times 10^{-3} \text{ W/cm}^2}$$

where $$w$$ is our beam width (should be 7mm for lasers with a beam width less than 0.7mm), $$\theta$$ is our fan angle, and $$\phi$$ is our radiant power.

Plugging in our values and making $$T$$ a 'blink': $$D_{\text{NOHD}}=\frac{150\times10^{-3}\text{ W}}{0.7\text{ cm}\times 30^{\circ} \frac{\pi}{180}\times1.8\times0.25^{-0.25} \times 10^{-3} \text{ W/cm}^2}=160\text{ cm}$$

You have posted too little information really. What kind of laser is it? Wavelength? CW? Pulsed? Class?

• The streamline that I have is a laser diode with 640 nm, CW and Class 3B. Could you send me any reference to study about this calculation? So glad for your help Commented Oct 16, 2020 at 14:21
• Thanks for your help. This information it's very important for me. If you have any document to help me learn more, I'll be very happy. Commented Oct 19, 2020 at 19:40