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This product has multiple variants. The options may be chosen on the product page
This product has multiple variants. The options may be chosen on the product page
According to a recent Dallas Morning News article by writer Mary Jacobs, there&#;s should be more to selecting prescription glasses than simply handing in your eye prescription and choosing a frame. The type of lens material should also be considered. Many people are discovering the benefits of anti-reflective coatings.
Also known as anti-glare or AR coatings, these are special coatings that are designed to decrease the amount of reflective light in lenses. They can be applied to either the back, front or both sides of lenses so that a maximum amount of positive light enters the eyes to give you the clearest view possible. Here are some of the pros and cons of anti-reflective coating glasses, along with a few considerations.
Advantages of Anti-reflective Coating Glasses
AR coatings offer several benefits.
Drawbacks
On the other hand, anti-reflective coating glasses do have a few negatives.
- They&#;re can look dirty due to the clearness of the lenses. Although anti-reflective coatings are really not any dirtier than a regular pair of glasses, they&#;re more noticeable because there isn&#;t any glare to hide the dirt.
- As a result you may have to clean your lenses more frequently, which can especially be the case for some of the lower-cost AR coatings.
- They generally aren&#;t recommended for
reading glasses
that rest on the low bridge of the nose. If you do spend a considerable amount of time using a tablet, just be sure you read in conditions that provide adequate light.
Considerations and Warnings
- Coatings that are applied to the outside of lenses are more likely to peel, scratch or wear off. That&#;s why it&#;s a good idea for young children to postpone having them, unless they have specific needs in which an anti-reflective coating would be beneficial.
- Do not clean your lenses dry. Always rinse your lens off before cleaning them to avoid grinding any destructive particles into your AR lenses.
- Clean your lenses using a
microfiber cloth
; using a shirt or tie can be damaging.
- In addition to not cleaning your lenses properly, anti-reflective coating glasses can also be injured by extreme temperatures, such as being near ice or fire.
- Store your lenses in their
protective case
when they&#;re not being used.
- Although these coatings last longer than glasses without them, you still need to buy them from a reputable company that gives you a high quality guarantee. Be sure that the warranty includes lenses being changed in case there are issues with the coatings.
How to clean Lenses
that have Anti Reflective Coating
Watch Video
How to Order Glasses with anti-reflective lenses
1. SELECT THE FRAME
RX Safety offers a wide range of glasses frames that match perfectly with anti-reflective lenses. Choose your favorite eyeglasses, sunglasses, or prescription safety glasses.
AFTER CHOOSING THE PERFECT FRAME, CLICK IN &#;SELECT PRESCRIPTION LENSES&#;
2. SELECT LENS MATERIAL
Inside our prescription form, you can select your prescription type. Choose between, single vision, bifocal and progressive. Then, you will choose your lens material.
AFTER CHOOSING YOUR PRESCRIPTION TYPE, YOU CAN SELECT DIFFERENT LENS MATERIALS
3. SELECT LENS COLOR
Customize your lenses by choosing your lens color, including Transition options.
SELECT YOUR FAVORITE LENS COLOR
4. ADD EXTRA COATINGS
The glasses can be upgraded with special coatings such as anti-fog and anti-scratch to improve their overall performance. This is where you can add the anti-reflective coating.
SELECT YOUR PREFERRED COATINGS TO UPGRADE YOUR prescription safety glasses
5. ADD YOUR PRESCRIPTION INFORMATION
Now it is the time to upload or fill your prescription information. You&#;re done! The rest is with us. We will work on your glasses with anti-reflective lenses and deliver to your address.
ADD YOUR PRESCRIPTION INFORMATION
For any questions you may have, visit us at Rx-Safety.com. Please contact us and learn about all we have to offer in eyewear products.
For more information, please visit AR coating wholesaler.
Laser Induced Damage Threshold Tutorial
The following is a general overview of how laser induced damage thresholds are measured and how the values may be utilized in determining the appropriateness of an optic for a given application. When choosing optics, it is important to understand the Laser Induced Damage Threshold (LIDT) of the optics being used. The LIDT for an optic greatly depends on the type of laser you are using. Continuous wave (CW) lasers typically cause damage from thermal effects (absorption either in the coating or in the substrate). Pulsed lasers, on the other hand, often strip electrons from the lattice structure of an optic before causing thermal damage. Note that the guideline presented here assumes room temperature operation and optics in new condition (i.e., within scratch-dig spec, surface free of contamination, etc.). Because dust or other particles on the surface of an optic can cause damage at lower thresholds, we recommend keeping surfaces clean and free of debris. For more information on cleaning optics, please see our Optics Cleaning tutorial.
Testing Method
Thorlabs' LIDT testing is done in compliance with ISO/DIS and ISO specifications.
First, a low-power/energy beam is directed to the optic under test. The optic is exposed in 10 locations to this laser beam for 30 seconds (CW) or for a number of pulses (pulse repetition frequency specified). After exposure, the optic is examined by a microscope (~100X magnification) for any visible damage. The number of locations that are damaged at a particular power/energy level is recorded. Next, the power/energy is either increased or decreased and the optic is exposed at 10 new locations. This process is repeated until damage is observed. The damage threshold is then assigned to be the highest power/energy that the optic can withstand without causing damage. A histogram such as that below represents the testing of one BB1-E02 mirror.
The photograph above is a protected aluminum-coated mirror after LIDT testing. In this particular test, it handled 0.43 J/cm2 ( nm, 10 ns pulse, 10 Hz, Ø1.000 mm) before damage.
The photograph above is a protected aluminum-coated mirror after LIDT testing. In this particular test, it handled 0.43 J/cm( nm, 10 ns pulse, 10 Hz, Ø1.000 mm) before damage.
Example Test Data
Fluence
# of Tested Locations
Locations with Damage
Locations Without Damage
1.50 J/cm2
10
0
10
1.75 J/cm2
10
0
10
2.00 J/cm2
10
0
10
2.25 J/cm2
10
1
9
3.00 J/cm2
10
1
9
5.00 J/cm2
10
9
1
According to the test, the damage threshold of the mirror was 2.00 J/cm2 (532 nm, 10 ns pulse, 10 Hz, Ø0.803 mm). Please keep in mind that these tests are performed on clean optics, as dirt and contamination can significantly lower the damage threshold of a component. While the test results are only representative of one coating run, Thorlabs specifies damage threshold values that account for coating variances.
Continuous Wave and Long-Pulse Lasers
When an optic is damaged by a continuous wave (CW) laser, it is usually due to the melting of the surface as a result of absorbing the laser's energy or damage to the optical coating (antireflection) [1]. Pulsed lasers with pulse lengths longer than 1 µs can be treated as CW lasers for LIDT discussions.
When pulse lengths are between 1 ns and 1 µs, laser-induced damage can occur either because of absorption or a dielectric breakdown (therefore, a user must check both CW and pulsed LIDT). Absorption is either due to an intrinsic property of the optic or due to surface irregularities; thus LIDT values are only valid for optics meeting or exceeding the surface quality specifications given by a manufacturer. While many optics can handle high power CW lasers, cemented (e.g., achromatic doublets) or highly absorptive (e.g., ND filters) optics tend to have lower CW damage thresholds. These lower thresholds are due to absorption or scattering in the cement or metal coating.
Pulsed lasers with high pulse repetition frequencies (PRF) may behave similarly to CW beams. Unfortunately, this is highly dependent on factors such as absorption and thermal diffusivity, so there is no reliable method for determining when a high PRF laser will damage an optic due to thermal effects. For beams with a high PRF both the average and peak powers must be compared to the equivalent CW power. Additionally, for highly transparent materials, there is little to no drop in the LIDT with increasing PRF.
In order to use the specified CW damage threshold of an optic, it is necessary to know the following:
- Wavelength of your laser
- Beam diameter of your beam (1/e2)
- Approximate intensity profile of your beam (e.g., Gaussian)
- Linear power density of your beam (total power divided by 1/e2 beam diameter)
Thorlabs expresses LIDT for CW lasers as a linear power density measured in W/cm. In this regime, the LIDT given as a linear power density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size, as demonstrated by the graph to the right. Average linear power density can be calculated using the equation below.
The calculation above assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other non-uniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right).
Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at nm scales to 5 W/cm at 655 nm):
While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application.
Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information.
Pulsed Lasers
As previously stated, pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material. Unfortunately, it can be very difficult to compare the LIDT specification of an optic to your laser. There are multiple regimes in which a pulsed laser can damage an optic and this is based on the laser's pulse length. The highlighted columns in the table below outline the relevant pulse lengths for our specified LIDT values.
Pulses shorter than 10-9 s cannot be compared to our specified LIDT values with much reliability. In this ultra-short-pulse regime various mechanics, such as multiphoton-avalanche ionization, take over as the predominate damage mechanism [2]. In contrast, pulses between 10-7 s and 10-4 s may cause damage to an optic either because of dielectric breakdown or thermal effects. This means that both CW and pulsed damage thresholds must be compared to the laser beam to determine whether the optic is suitable for your application.
Pulse Duration
t < 10-9 s
10-9 < t < 10-7 s
10-7 < t < 10-4 s
t > 10-4 s
Damage Mechanism
Avalanche Ionization
Dielectric Breakdown
Dielectric Breakdown or Thermal
Thermal
Relevant Damage Specification
No Comparison (See Above)
Pulsed
Pulsed and CW
CW
When comparing an LIDT specified for a pulsed laser to your laser, it is essential to know the following:
- Wavelength of your laser
- Energy density of your beam (total energy divided by 1/e2 area)
- Pulse length of your laser
- Pulse repetition frequency (prf) of your laser
- Beam diameter of your laser (1/e2 )
- Approximate intensity profile of your beam (e.g., Gaussian)
The energy density of your beam should be calculated in terms of J/cm2. The graph to the right shows why expressing the LIDT as an energy density provides the best metric for short pulse sources. In this regime, the LIDT given as an energy density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now adjust this energy density to account for hotspots or other nonuniform intensity profiles and roughly calculate a maximum energy density. For reference a Gaussian beam typically has a maximum energy density that is twice that of the 1/e2 beam.
Now compare the maximum energy density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately [3]. A good rule of thumb is that the damage threshold has an inverse square root relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 1 J/cm2 at nm scales to 0.7 J/cm2 at 532 nm):
You now have a wavelength-adjusted energy density, which you will use in the following step.
Beam diameter is also important to know when comparing damage thresholds. While the LIDT, when expressed in units of J/cm², scales independently of spot size; large beam sizes are more likely to illuminate a larger number of defects which can lead to greater variances in the LIDT [4]. For data presented here, a <1 mm beam size was used to measure the LIDT. For beams sizes greater than 5 mm, the LIDT (J/cm2) will not scale independently of beam diameter due to the larger size beam exposing more defects.
The pulse length must now be compensated for. The longer the pulse duration, the more energy the optic can handle. For pulse widths between 1 - 100 ns, an approximation is as follows:
Use this formula to calculate the Adjusted LIDT for an optic based on your pulse length. If your maximum energy density is less than this adjusted LIDT maximum energy density, then the optic should be suitable for your application. Keep in mind that this calculation is only used for pulses between 10-9 s and 10-7 s. For pulses between 10-7 s and 10-4 s, the CW LIDT must also be checked before deeming the optic appropriate for your application.
Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. Contact Tech Support for more information.
[1] R. M. Wood, Optics and Laser Tech. 29, 517 ().
[2] Roger M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, Philadelphia, PA, ).
[3] C. W. Carr et al., Phys. Rev. Lett. 91, ().
[4] N. Bloembergen, Appl. Opt. 12, 661 ().
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