Laser Safety Eyewear - M-Rated Filters

M-Rated (Ultrafast) Filters

Protection against ultrafast lasers available in four frame styles

Ultrafast lasers (those with pico- and femtosecond pulse lengths) require that the laser safety eyewear possess an "M" rating. LASERVISION offers a number of plastic and mineral glass filters which have been tested for stability against ultrafast lasers and have been assigned the necessary M-rating.

Until recently, ultrafast lasers with picosecond (ps) or femtosecond (fs) pulse lengths were the preserve of advanced research laboratories. Today, ultrafast lasers are being used in increasing numbers in many industrial and medical processes. As with all lasers, laser safety eyewear must be used which has been tested and certified to provide the protection necessary for the particular wavelength(s), power levels (irradiance) and pulse lengths of the laser in question. For ultrafast lasers, the eyewear must carry an M-rating in accordance with BS EN 207.

Ultrafast lasers behave differently to those with longer pulse lengths. When a ps or fs laser strikes a filter, a non-linear optical effect called induced transmission can occur. This results in a momentary increase in the spectral transmittance of the filter material when it is irradiated with short, high-energy laser pulses. Even those filters which provide high protection levels with nanosecond or longer pulses can exhibit induced transmittance with shorter pulses and hence suffer from reduced protection against ps and fs lasers.

LASERVISION has undertaken a great deal of research to develop plastic filter materials which provide high (M-rated) protection against ultrafast lasers. The culmination of this programme is filter type P1006, a novel plastic filter which has been certified with the extremely high M L6 protection rating. For even higher protection levels, absorbing glass is the only appropriate filter material available. LASERVISION has performed laser damage testing of new and existing absorbing glass filters against ultrafast lasers. As a result, appropriate M protection certificates have been awarded for these filters as well.

Filter type 39 is a new absorbing mineral glass and is the high power glass equivalent of the P1006 plastic filter. Type 39 has been awarded protection ratings of M L8 or M L9 (depending upon the frame style chosen) for the wavelength range of the Ti:Sapphire laser (750-1100nm).

The table below gives an overview of the currently available LASERVISION filter materials with M protection ratings. The frames ALL STAR (L-02K), PROTECTOR (L-08K) and ECO (L-07K) also provide M rated protection. Please note that the overall rating of the filter + frame combination is the lower of that provided by the filter or frame.

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M-Rated Filters	Frame Style	Protection
P1006	DYNA GUARD (670)	M L6 >315-532nm M L7 980-1065nm
Type 23	ALL STAR (L-02K) ECO (L-07K) PROTECTOR (L-08K)	M L9 795-805nm
Type 27	ALL STAR (L-02K)	M L8 >315-532nm M L9 1030-1100nm
	VISION (L-05K)	M L5 >315-532nm M L5 1045-1064nm
	ECO (L-07K)	M L6 >315-532nm M L6 1030-1100nm
	PROTECTOR (L-08K)	M L8 >315-532nm M L9 1030-1100nm
Type 35	ALL STAR (L-02K)	M L9 1030-1100nm
	ECO (L-07K)	M L6 1030-1100nm
	PROTECTOR (L-08K)	M L9 1030-1100nm
Type 37	ALL STAR (L-02K)	M L8 >315-532nm M L9 1030-1100nm
	VISION (L-05K)	M L6 >315-532nm M L6 1045-1064nm
	ECO (L-07K)	M L6 >315-532nm M L6 1030-1100nm
	PROTECTOR (L-08K)	M L8 >315-532nm M L9 1030-1100nm
Type 39	ALL STAR (L-02K)	M L8 >315-532nm M L9 >750-1100nm
	ECO (L-07K)	M L6 >315-532nm M L9 >750-1030nm M L6 >1030-1100nm
	PROTECTOR (L-08K)	M L8 >315-532nm M L9 >750-1100nm
Type 48	ALL STAR (L-02K)	M L8 720-<795nm M L9 795-1200nm
	ECO (L-07K)	M L8 720-<795nm M L10 795-805nm M L6 1030-1100nm
	PROTECTOR (L-08K)	M L8 720-<795nm M L10 795-805nm M L9 805-1200nm
Type 58	ALL STAR (L-02K)	M L2 620-680nm M L6 >680-690nm M L8 >690-795nm M L9 >795-1064nm M L5 >1064-1400nm M L1 >1400-1580nm
	ECO (L-07K)	M L8 700-795nm M L10 >795-805nm M L9 >805-900nm M L6 >1030-1064nm M L5 >1064-1100nm
	PROTECTOR (L-08K)	M L2 620-680nm M L6 >680-690nm M L8 >690-795nm M L10 >795-1064nm M L5 >1064-1400nm M L1 >1400-1580nm
Type 68	ALL STAR (L-02K)	M L8 750-800nm M L9 >800-1000nm M L8 >1000-1064nm
	ECO (L-07K)	M L8 750-800nm M L6 >1030-1064nm
	PROTECTOR (L-08K)	M L8 750-800nm M L9 >800-1000nm M L8 >1000-1064nm

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