Laser hazard evaluation method for middle infrared laser systems

Marshall, Wesley J.; Aldrich, R. C.; Zimmerman, Sheldon

doi:10.2351/1.4745424

Cited by 8 publications

(4 citation statements)

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“…Therefore, for exposures of skin and cornea above this MPE at 1.54 m, severe hazards can exist, negating the term "eye safe." For a thorough understanding of laser hazard evaluation methods, see Marshall et al 6 The Yucatan mini-pig ͑Sus scrofa domestica͒ was used in this study as the model for determining the threshold dose at the minimum visible lesion ͑MVL͒ level for laser injury to skin at 1.54-m wavelength for a single 0.60-ms pulse and a single 31-ns pulse. The ED 50 along with the fiducial limits at the 95% confidence level were determined for this exposure duration using the Probit 7 analysis technique.…”

Section: Introductionmentioning

confidence: 99%

Visible lesion thresholds with pulse duration, spot size dependency, and model predictions for 1.54-μm, near-infrared laser pulses penetrating porcine skin

et al. 2006

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Er:glass lasers have been in operation with both long pulses (hundreds of microseconds) and Q-switched pulses (50 to 100 ns) for more than 35 yr. The ocular hazards of this laser were reported early, and it was determined that damage to the eye from the 1.54-microm wavelength occurred mainly in the cornea where light from this wavelength is highly absorbed. Research on skin hazards has been reported only in the past few years because of limited pulse energies from these lasers. Currently, however, with pulse energies in the hundreds of joules, these lasers may be hazardous to the skin in addition to being eye hazards. We report our minimum visible lesion (MVL) threshold measurements for two different pulse durations and three different spot sizes for the 1.54-microm wavelength using porcine skin as an in vivo model. We also compare our measurements to results from our model, based on the heat transfer equation and the rate process equation. Our MVL-ED50 thresholds for the long pulse (600 micros) at 24 h postexposure were measured to be 20, 8.1, and 7.4 J cm(-2) for spot diameters of 0.7, 1.0, and 5 mm, respectively. Q-switched laser pulses of 31 ns had lower ED50 (estimated dose for a 50% probability of laser-induced damage) thresholds of 6.1 J cm(-2) for a 5-mm-diam, top-hat spatial profile laser pulse.

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Section: Introductionmentioning

confidence: 99%

Visible lesion thresholds with pulse duration, spot size dependency, and model predictions for 1.54-μm, near-infrared laser pulses penetrating porcine skin

et al. 2006

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“…24 For lasers operating within the retinal hazard region, more of the emitted energy may enter the pupil and become focused on the retina when the exit beam diameter is larger than the pupil. This reduction in beam diameter concentrates the beam irradiance on the cornea.…”

Section: Telescopic Viewing "Condition 1…mentioning

confidence: 99%

Rationale for laser classification measurement conditions

Sliney

Marshall

Brumage

2007

Journal of Laser Applications

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The basic concept of laser hazard classification with four fundamental risk groups and several subclasses is well understood by most laser users. However, many readers of laser safety standards are frequently puzzled by the rigid measurement conditions applied for hazard classification, even if this is normally a task performed by the laser manufacturer and not by a laser user or a Laser Safety Officer. The historical rationale for the measurement conditions is provided and it is emphasized that the aim of each measurement is to simulate a wide range of ocular exposure conditions that would be reasonably foreseeable worst-case viewing conditions during the use of the laser product. Measurements, if needed to compare human exposures with the maximum permissible exposure limits, emphasize actual exposure conditions and generally do not match the measurement used for hazard classification.

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“…This MPE varies only with exposure durations and biological systems. We interpreted these standards for the various wavelengths and pulse widths with the help of Marshall, et al 2 Several types of laser systems such as the COIL, can produce wavelengths in the NIR, (1200 nm to 1400 nm), with pulse widths ranging from Q-switched nanoseconds (ns) to continuous wave (CW). A commonly used laser that generates these wavelengths is the Neodymium Yittrium Lithium Florine (Nd:YLF), which lases at the 1314 nm line.…”

Section: Introductionmentioning

confidence: 99%

Comparative analysis of spot size dependence for lesions produced by infrared laser pulses

et al. 2003

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The current laser safety standard for skin exposures, ANSI Z136.1, was based on a limited number of data points for various beam sizes at a few specific wavelengths. To help refine this standard, we explore the existence of a relationship between beam spot size and the ED 50 lesion threshold values. In the first phase of this study we analyzed the spot size dependence of the skin lesion thresholds from previously documented experiments. We utilized the thermal skin model to predict damage thresholds and compared these with those presented in this paper. We report the results of this analysis , which we used to design an experiment to determine the true spot-size dependency of skin laser damage thresholds. The data collected in this first phase is discussed and compared to the existing ANSI Z136.1 (2000) laser safety standard.

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Laser hazard evaluation method for middle infrared laser systems

Cited by 8 publications

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Visible lesion thresholds with pulse duration, spot size dependency, and model predictions for 1.54-μm, near-infrared laser pulses penetrating porcine skin

Visible lesion thresholds with pulse duration, spot size dependency, and model predictions for 1.54-μm, near-infrared laser pulses penetrating porcine skin

Rationale for laser classification measurement conditions

Comparative analysis of spot size dependence for lesions produced by infrared laser pulses

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