Lens Savers®

* Amada, Trumpf, Bystronic, Mazak, Mitsubishi, Tanaka,
Precitec, Laser Lab 등의 주요 CO2 레이저 장비들에 적용 가능합니다. *

LENS SAVERS® LENS SHIELD PRODUCT PROFILE

Lens Savers® protective windows shield CO2 laser focusing lenses against spatter damage. Users report savings of 50% and more on their optics budgets when using inexpensive and disposable Lens Savers® windows. On a single laser the savings are thousands of dollars annually. One large shop with more than a dozen lasers reports savings exceeding $50,000 per year.

The focusing lens of a CO2 laser is positioned at the end of a long chain of delicate and expensive optics which direct the laser beam at the target---a sheet of steel---under thousands of watts of power. The focusing lens, which can cost anywhere from $500 to $3000, seals the rest of the laser system's equally expensive optics from the sparks, smoke and particles ( known as "spatter") thrown off during the cutting or welding process while it also focuses the beam at the target. As the focusing lens gets dirty, the quality of the weld or cut degenerates because the lens and its delicate anti-reflective coating begin to absorb laser energy. As energy is absorbed by the lens it delivers less power and it heats up and begins to distort the focus. Weld or cut quality then degrades.

Eventually, the laser focusing lens must be replaced due to the power loss and focus distortion caused by spatter damage. If the lens is not replaced, it will absorb so much laser power that it will melt or explode, thereby rupturing the barrier that shields the rest of the system optics and causing a catastrophic failure of the CO2 laser system which results in extensive downtime as well as a very expensive repair.

Protective windows have been used to protect against welding spatter for many years. But, until ICL developed a new way of mounting them, protective windows worked only in low pressure environments such as welding. Under high pressure these protective windows will fail unless something is done to prevent breakage. CO2 laser cutting systems use assist gas under pressure to aid in the cutting process. Before the engineers at ICL's Lens Savers® Division created a technical solution to the problem, the high gas pressure used in cutting had made it impossible to use lens protection windows. ICL's patent pending pressure bypass lens mounting method has now made it possible to use Lens Savers® protective windows in all CO2 laser cutting systems. Lens Savers® adapters or lens mounts let the pressure within the cutting head equalize on both sides of the protective window. A cavity is formed between the Lens Savers® window and the lens which is allowed to pressurize. There is another high pressure area on the opposite side of the Lens Savers® window where the assist gas is being used to enhance the cut. Since both areas are under high pressure, with the Lens Savers® window sandwiched in the middle, the window is effectively under zero pressure and does not break.

ICL's engineers have now designed a full line of window and lens mounts and adapters that allow CO2 laser users to put a Lens Savers® window into a system without any modifications except the addition of the mount or adapter. They have created an assortment of ingenious ways to squeeze Lens Savers® into the confined spaces where focusing lenses are typically positioned. Lens Savers® adapters are available for all major CO2 laser systems, including Amada, Bystronic, Cincinnati, Laser Lab, Mazak, Mitsubishi, Strip-it and Trumpf.

Trumpf L3030 및 L4030용 Lens Savers® 시스템 구성


Amada Apelio 2415 및 3015용 Lens Savers® 시스템 구성

Power Loss

There are several reasons for power loss in a laser, but most of the losses are from Fresnel reflection of the laser beam off of the two (2) surfaces of the lens or window and from absorbance. Power loss in a laser system is a function of reflection losses and absorbance. As noted above, all of the materials used for Lens Savers® windows absorb very little energy. Accordingly, substantially all of the losses users experience are from reflection until the window becomes damaged by spatter. Reflection is a function of the refractive index of the optical material. Those losses are described above in the section on reflection and absorbance.

In practice, power loss translates into slower operation of the laser, except at the margins where power loss will be so severe that cutting of particularly thick material becomes impossible.

Absorbance and Reflection

Lens Savers® protective windows are polished optical crystal windows made from single crystal potassium chloride (KCl) and Sodium Chloride (NaCl). These optical materials absorb very little laser energy at 10.6 microns, which is the wavelength at which CO2 lasers operate. For YAG systems, the windows are made from a type of glass ---BK-7--- which absorbs little energy at 1064nm, the wavelength at which YAG lasers operate.

Lens Savers® windows are made from materials that have very low refractive indices at their operating wavelengths. KCl, for example, has a refractive index of 1.454 at 10.6 microns and it transmits at better than 93% without application of an AR coating. Reflection losses through the 2 surfaces of an uncoated KCl window at 10.6 microns are 6.8%. NaCl has a refractive index of 1.49 and reflection losses at 10.6 microns are around 8%. Coated BK-7 transmits 99% of the available energy at 1064nm. Uncoated BK-7 has a refractive index of 1.506 at 1064 nm and losses are about 8%. Coated BK-7 transmits over 99% of available energy in a YAG laser at 1064nm.

A Comparison of KCl with ZnSe is instructive to illustrate why the materials used in Lens Savers® work so well. The low refractive index of KCl makes it a much more efficient laser energy transmitter than uncoated ZnSe from which CO2 laser focusing lenses are made. ZnSe has a very high refractive index (2.40)---so high that it is the material of choice in the field of internal reflection spectroscopy where high reflection is desired. Without an anti-reflective (AR) coating, ZnSe will transmit less than 70% of available energy. Reflection losses through the two surfaces of an uncoated ZnSe window are 29% at 10.6 microns. After application of an AR coating to ZnSe, manufacturers claim that transmission at 10.6 microns is 99%. As the delicate AR coating on ZnSe focusing lenses deteriorates from spatter damage and normal cleaning, the performance of the lens degrades.

Unless you are operating near the power limit of a CO2 laser system, you will not need an AR coating on a Lens Savers® window in a CO2 laser system. ICL does not sell AR coated Lens Savers® for CO2 lasers, and we do not recommend AR coatings on Lens Saver® for CO2 lasers because they are too expensive for the nature of the product. However, ICL will provide AR coated windows for CO2 lasers at $23.99 per window in minimum batches of 50 windows for YAG lasers, AR coatings are relatively inexpensive and we offer both uncoated and AR coated windows from stock. We leave it the user to decide whether the extra performance is worth the extra cost of AR coatings.

The Operating Environment

Laser optics are subjected to a variety of conditions that cause performance degradation over time or which make it impossible to use the optics under certain conditions. These environmental factors include spatter, cleaning, pressure, moisture and heat. Variables that can affect optics life are the composition of the laser target, the composition of assist gases and different ways that operators handle the optics. Most of these factors can be adequately controlled, or at least identified, by the user. Lens Savers® windows enable users to control two factors which affect lens life---spatter damage and the degradation of the lens that arises from cleaning it. Spatter and cleaning both lead to a deterioration of the AR coating on a ZnSe lens. Even lenses that appear clean can degrade badly in performance when the AR coating begins to get wiped off. Lens Savers® block spatter and limit the amount of cleaning a lenses require, thereby extending lens life.

But, Lens Savers® are affected by other environmental factors, the most significant of which are pressure and moisture. CO2 laser Lens Saver® windows are hygroscopic, so care must be taken by the user to protect them from moisture when they are not in use. In use, the assist gas is usually sufficiently dry to protect against moisture damage. Detailed handling instructions are included with every package of Lens Saver® windows, and by following these instructions most environmental issues can be effectively dealt with. "Handling CO2 Laser Lens Saver® Protection Windows" However, there is one enemy of Lens Saver® windows that must be overcome by the lens mount---assist gas pressure.

Many of our new customers tell us at the outset that they have tried lens protection windows in CO2 laser cutting systems but that the windows always broke very quickly. These customers tell us that they know lens protection windows work in welding lasers, so they cannot understand why they won't work in cutting lasers. The answer is almost always pressure. NaCl and KCl, the materials from which CO2 laser Lens Saver® windows are made, will not take much more than 25 pounds of pressure without breaking unless something is done to solve the pressure problem. The good news is that we've solved the problem. ICL has invented a series of patent pending lens mounts and adapters that allow Lens Saver® windows to survive while operating in the high assist gas pressures that are employed with CO2 lasers for cutting many substrates such as stainless steel.

Selecting a Lens Savers® Window Mount or Adapter

If you are using your laser for cutting with assist gases at pressures in excesss of 25 psi, you must use a Lens Savers® window mount or adapter to keep the window from breaking under pressure. These mounts are described in detail in the following pages and ICL will design custom mounts for any system for $499.00, which is the same price that we charge for all lens mounts and adapters in our standard product range. If you don't see what you need, ask us and we will design it for you.

Custom Lens Mounts and Adapters

ICL routinely makes lens mounts and adapters for customers systems. In many cases, we can make an adapter or lens mount for a price that will not exceed the $499.00 that we charge for standard lens mounts. Some of these custom mounts become standard parts, but there are many mounts that we have already designed which are beyond the scope of this catalog because they do not apply to systems which are of broad interest. If you need a custom lens mount, please do not hesitate to call us. We can usually design and fabricate a custom lens mount within 4 to 6 weeks.