/ [units] The focused intensity/irradiance computed from diffraction theory,(at the peak of the diffraction pattern in the focal plane), is ## E_f=\frac{E_o A^2}{\lambda^2 f^2} ## where ## E_o ## is the irradiance (watts/m^2) of the incident beam. The irradiance as a function of distance from the center of the pattern is given by I = 4I 0 cos 2, where I 0 is the irradiance of each of the interfering rays. / ( sqrt * ) Learn more about hiring developers or posting ads with us

It only takes a minute to sign up.I have been trying to calculate what retinal irradiance value I get with a 1 blue LED system.Since the manufacturer didn´t give the spectral distribution information, I will approximate LED as a monochromatic one (using the 460 nm peak).From the datasheet, the LED intensity range goes from 6 lumen to 30 lumen. * ) However, the design formulation of a freeform reflective or refractive surface for producing prescribed irradiance patterns from a point source has been a great challenge. 7854 ")For a full-featured Laser Hazard Distance Calculator, with the NOHD, EDThis calculator will not work with Internet Explorer. * ) / Physics Stack Exchange works best with JavaScript enabled This will depend on the state of the eye lens (its optical power), spectrum of the LED, age of the person being irradiated. Detailed answers to any questions you might have 0.5 7854 As the beam power becomes spread over a larger and larger area, the amount of light entering a pupil decreases:At some distance from the laser, the light intensity (irradiance) will be at the Maximum Permissible Exposure (MPE). I converted into radiometric units with the eye curve sensitivity, and taking into account the angle percentage that reach the eye, I achieved the 0.006W valueMonochromatic LED? Optics Formulas. 7854 So, from the spacial LED curve, the The wavelength of 460nm has energy of about 2.7eV or Thanks for contributing an answer to Physics Stack Exchange! You appear to be running Internet Explorer or another incompatible browser; if so, all the results will be “.0”. such as Microsoft Edge, Mac Safari, Google Chrome, Firefox, etc. [beam-diameter-in-meters] In this case, the input optics of the second instrument is a "cosine receptors" and the instrument is aimed vertically upward to measure Ed directly.

The first two options are discussed below. The center is the “worst case” area for an eye to be located.Irradiance is the power of the laser, spread out over an area. ( Featured on Meta He considers the recovery of radi-ance, given irradiance at all surface orientations. The radiance-from-irradiance problem as discussed in this paper is addressed by Preisendorfer1 in his treatise on hydrologic optics. [beam-diameter-in-meters]

Discuss the workings and policies of this site [mw] Either it's a laser, or it's not monochromatic. $\begingroup$ This will depend on the state of the eye lens (its optical power), spectrum of the LED, age of the person being irradiated. [beam-diameter-in-meters] So currently this question lacks detail.Hi @Ruslan.

site design / logo © 2020 Stack Exchange Inc; user contributions licensed under 32.8 According to laser safety experts, the Maximum Permissible Exposure (MPE) for the eye to continuous wave visible laser light for a 1/4 second exposure is 2.54 mW/cm 2.This assumes that a person will blink, turn away or otherwise stop the exposure within 1/4 second. ) Plugging into the formula: I = 4I 0 cos 2 = 1.77I 0. ( Anybody can answer I reached a value of I know from the ray tracing software that only 3.7º of the LED (total from the center) reach the pupil. / 0.3048 ( * * ) This distance is called the Nominal Ocular Hazard Distance (NOHD):A laser beam can be made safer by increasing its divergence (beam spread), lowering its power, and reducing the exposure time.

Pre-isendorfer’s conclusion is that irradiance and radiance are equivalent and that irradiance can be inverted to give the The best answers are voted up and rise to the top If the calculated irradiance above is greater than 2.54 mW/cmThe Maximum Permissible Exposure varies depending on the laser's operating mode (continuous wave or pulsed), wavelength, exposure duration, and whether the exposure is to Eye, Skin or materials.In the U.S., milliwatts per square centimeter is most commonly used. * If the calculated irradiance above is greater than 2.54 mW/cm 2, then the laser light is a potential eye hazard. Stack Exchange network consists of 177 Q&A communities including

10 Thus the ratio is just 1.77. Laser beams get wider with distance. 1000 I added more relevant information to the problem. ( (Note: Because this online calculator only shows four decimal places, this may not be sufficient precision. $\endgroup$ – Ruslan Aug 21 '19 at 10:55 ) ( [mw] ( Light is a transverse electromagnetic wave. I want to find the Irradiance (Watts/m2) from the given power in the given spectral range to compare with the irradiance of the UV of this range in 1 Sun (AM 1.5).

Because laser beams diverge, the irradiance will be higher (more hazardous) closer to the laser, and will be lower (less hazardous) farther from the laser. * By using our site, you acknowledge that you have read and understand our Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Anybody can ask a question So currently this question lacks detail. That doesn't sound right. Typical 460 nm LEDs have FWHM ~20 nm. And you still haven't specified what kind of irradiance you're interested in – average over some area, maximum, or something else. * [beam-diameter-in-meters] * For the 6 lumen case, I used scotopic eye sensitivity curve (i want to apply the stimulus in a dark room) to convert the lumen value to radiant power (W).