Laser Power Ratings & OFL PowerCheck
The PowerCheck Test
We test lasers in a couple of different ways.
(1) For high power lasers and modules and also to evaluate new products we use thermopile sensor on an optical bench:
This method allows us to collect more detailed information but takes some time to set up.
The optical bench allows us to easily add IR or bandpass filters in front of the sensor so we can check the output at specific wavelengths.
The thermopile sensor is also convenient for 405nm lasers where optical power meters are often less accurate.
The image above shows testing of a the 50mW+ 405nm pen. The background reading is 7mW, the laser peaks at 75mW, the average ouptut is 67mW so we would label this laser as 67 - 7 = 60mW.
(2) To check lower power lasers and as a convenient quick test for lasers before dispatch we use a hand-held Coherent Lasercheck.
The laser is fitted with freshly charged batteries and powered up for 10 seconds. The average power reading is then taken at a distance of 12 inches over the next 10 seconds using a Coherent Lasercheck calibrated in accordance with ISO 10012-1.For all DPSS (green) lasers our IR filter (see OFL 30 for details) is fitted onto the meter as shown below. This filter blocks about 6% of the laser power at 532nm and over 99% of IR. The filter effect is factored into the reported reading.
Direct reading of a red diode laser (no filter required because no IR is present)
Direct reading of a <1mw Green Laser fitted with an internal IR filter
The IR Filter fitting we use for Green DPSS Lasers
Our Power Meter is calibrated in accordance with ISO 10012-1 and has a NIST traceable certificate.
Laser Power Ratings, Labeling and Classification
The Laser Label
Often laser safety labels are mistakenly used (or misused) as a guide to laser power, they are NOT a power rating and their purpose is to warn the user of the appropriate safety requirements.
There is more than one laser classification system in use worldwide and also various additional policies and regulations so this is a complicated area.
The complexity and and possible misinterpretation of regulations has been exploited by some rogue traders in the past, this brief summary is to highlight some key points for we think may be of interest to potential customers and explain some potentially confusing issues.
Often laser safety labels are mistakenly used (or misused) as a guide to laser power, they are NOT a power rating and their purpose is to warn the user of the appropriate safety requirements.
There is more than one laser classification system in use worldwide and also various additional policies and regulations so this is a complicated area.
The complexity and and possible misinterpretation of regulations has been exploited by some rogue traders in the past, this brief summary is to highlight some key points for we think may be of interest to potential customers and explain some potentially confusing issues.
Classes
The UK System classifies laser products and approvals using
Class 1, 1M, 2, 2M, 3R, 3B and 4 and uses CE approval.
The US System classifies laser products and approvals using
Class I, IIA, II, IIIA, IIIB and IV and uses FDA approval and 21CFR compliance.
These classes are progressive so a Class IIIB or 3B rating will, by default, also cover lasers in Classes 1 and 2. [Click on the the Safety tab for full class details.]
In addition to the Class a laser safety label will also show a maximum power output such as: <1mW, <5mW , <200mW etc. This has led to some confusion because the requirement is simply that the laser power (at the wavelength specified) should not exceed this figure which must be equal to or lower than the class maximum.
For the lower power classes the manufacturers will often simply state the upper limit of the class such as Class 2 <1mW or Class 3R <5mW rather than the actual laser power. The lasers can in fact be any power up to the limit specified. For higher power lasers the variations can be considerable.
Example:
In Class 3B that covers 5-500mW all the following labels are allowable for a laser with a peak output of 49mW:
Class 3B <50mW, Class 3B <100mW, Class 3B <200mW
In practice, to allow for manufacturing tolerances, the output on the safety label needs to be overstated by a safe margin. Since the labels do not imply any lower output, stating higher maximum values simply reduces the pressure on quality control to ensure the rated power is not exceeded.
Product Classification
These classes are primarily concerned with safety - the 'Accessible Emission Limit' of finished products - they cannot be used as a power guide.
A Class 1 Laser Product such as a DVD recorder can contain a 200mW laser diode that is a Class 3B laser. Since the laser is not accessible the product can be CE approved as Class 1.
A green DPSS laser pointer that is described accurately and sold as having a genuine 1mW output the assigned class may be less obvious: Since the power of DPSS lasers peaks slightly as they warm up then settles at a steady value Class 2 (or 2M) (1mW) may be exceeded in the warm-up cycle when the laser may briefly be Class 3R (<5mW). Furthermore to gain approvals which covers product use such as FDA or CE certification a manufacturer needs to account for abnormal use. For instance, if the wrong batteries were used it could give a momentary output of 6mW and exceeding Class 3R before burning out. To be marked as CE approved a Class 3B label would be needed whereas in normal use it may be expected to behave as a Class 1M or Class 2 laser product.
In the case of laser components, or spare parts where the manufacturer cannot control the final use, Class 3B is usually used as a 'catch-all' unless the component is known to have intrinsic limitations that prevent the output from exceeding the maximum of a lower class.
Manufacturers Ranges and Related Vendor Scams
Manufacturers often produce a range of lasers with different power ratings in the same body and as discussed above may legitimately adopt different labeling practices. This has in the past been exploited by some rogue traders who have failed to point out that the Safety Label is no real indication of the practical power output that can be achieved in use.
One of our suppliers produces top quality lasers with power outputs rated as at least 100, 200, 300 or 400mW, all have the same external appearance.
They are all labeled as Class 3B <500mW which complies with safety regulations. They also have the appropriate safety features for the US and European markets and have CE and FDA approval.
They have a separate product label which gives the output power the user can expect in practice. Looking at the power output graph of a laser (see below) helps to explain why they have adoped this policy of a single label:
The power output of this laser averages around 150mW, never less than 100 or above 200mW. It is sold on the basis that the customer gets what they pay for and this laser is sold as as a >100mW model.
In this case the selling practice is realistic and an appropriate Safety Label for this laser should show at least Class 3B <200mW .
The potential problem with rogue traders is that the laser safety label (which should show a maximum output for safety considerations) is misrepresented as a "power rating" for the laser. Since double the power is roughly double the price the rip-off potential is considerable.