1. Enter the laser wavelength in micrometers (µm) or nanometers (nm).
  2. Depending on your browser you can use your mouse, press the tab key, or use the return key to advance to the next input.
  3. For the laser mode of operation, choose Continuous, Single Pulse, or Repetitive Pulse.
  4. For Exposure Time a default value is shown to the right of the input box. If the input is blank the default will be used in the calculation.
  5. Enter parameter inputs using decimal or scientific notation. (0.001 is equivalent to 1E-3 1e-3).
  6. Use 1/e^2 beam diameter and divergence if you are entering values from a manufacturer’s laser data sheet.
  7. Basic hazard analysis values will appear in the Report.
    • Ocular MPE (J/cm² for Single Pulse; W/cm² for Continuous and Repetitive Pulse; for point sources only)
    • Eyewear (Optical Density (OD) for the eyewear filter rating for worst case exposure)
    • Intrabeam NOHD (Nominal Ocular Hazard Distance)
    • Diffuse NHZ (Nominal Hazard Zone for point source diffuse reflection)
  8. If you change an input, the output will be updated instantly.

Other Calculations Using EASY HAZ™ Basic

Easy HAZ™ Basic can be used to determine other hazard distances. Enter the laser wavelength in nm and follow the directions below. In each case the specified hazard distance will be displayed in the space for the Intrabeam NOHD.

Calculating Lens-On-Laser NOHD

To find the LOL NOHD: choose a beam diameter of 0.1 mm and a beam divergence of 1000b/f mrad where b = beam diameter on the lens and f = focal length of the lens

Calculating the Multimode Fiber Optic NOHD

To find the multimode FO NOHD: choose a beam diameter of 0.1 mm and a beam divergence of 1667NA mrad where NA = numerical aperture of the fiber

Calculating the Single Mode Fiber Optic NOHD

To find the single mode FO NOHD: choose a beam diameter of 0.1 mm and a beam divergence of 1273λ/ω mrad where λ = wavelength of the laser and ω = mode field diameter of the fiber in the same units as the wavelength

Calculation of Modified Diffuse Reflection NHZ

The Diffuse Reflection NHZ calculated is for a reflectivity of 100% and a viewing angle of 0 degrees. You can find other Diffuse Reflection NHZ values by multiplying the power by RcosV where R = Fractional Reflectivity (R=1 for 100%) and V = Viewing angle in degrees.

Example: R=20% and V=60 degrees
[cos(60)=0.5] RcosV=(0.2)(0.5)=0.1

Enter a power that is 0.1 times the laser power, and the value given for Diffuse Reflection NHZ will be for viewing a 20% diffuse reflection at 60 degrees.

Additional Useful Notes

For pulsed lasers, shorter pulses result in a lower MPE and a greater hazard. For repetitive pulse lasers at a constant average power, a lower pulse rate results in more energy per pulse, leading to a higher peak power and a greater hazard. If you have a Q-Switched laser but you don’t know the pulse duration, choose 100 ns (1E-7 s). The MPE is the same for pulse durations from 1 ns to several µs. Beam diameter and beam divergence affect Intrabeam NOHD only. If you don’t know these values, make your best guess. For most lasers 1 mm and 1 mrad will give you a worst case value of Intrabeam NOHD. If your laser beam is blue, use 0.5 mrad. More detailed information on laser hazard analysis will be available here in the future. If you have a question, e-mail us, or better yet, take our Applied Laser Safety course and learn all about basic laser hazard analysis. Now give it a try. You’re ready to use EASY HAZ™ Basic.