ADF stands for Auto Darkening Filter, which is consist of optical band pass filer, one or two LCD’s (Liquid Crystal Display), protection lens and electronic circuit unit.
LCD reduces visible light intensity entering eyes by electronic circuit which is energized by sensors. LCD response speed and circuit design will decide ADF reaction speed. The faster reaction speed is the better.
The welding arc consists of a wide-spectrum range of lighting. Some lighting is harmful to human eyes, like UV, FUV, NUV, NIR and IR. Optical band pass can stop UV (Ultra-Violet, including near UV and deep UV) and IR (Infra-Red, including near IR and far IR) light from entering human eyes when the welding arc is generated.
UV (especially deep UV) and IR (especially near IR) can damage the retina of human eyes if exposed for a certain period of time. According to DIN standards, the “UV component of welding arc light shall not surpass 0.000012% max of general UV range, and IR component shall not surpass 0.015% max of general IR range.”Optical band pass is composed of many multi-layer optical films, and each layer thickness is strictly controlled within a quarter of the visible wavelength, around 100 nm. All these layers work together to create optical interference for visible light band pass, which means visible light can pass through while UV and IR are stopped by the band pass. The optical layer is deposited by evaporation process in a vacuum oven. Each layer's thickness is different from the others. If any layer fails to be the right thickness, the whole band pass transmittance vs. wavelength curve will be influenced dramatically. Some UV or IR segment will arise and more UV/IR light will enter the welder’s eyes.
If poor-quality band pass is used, user’s eyes will be exposed to harmful UV or IR during each use. In the short-term, it will cause sore, burning eyes, eye-sight will decrease considerably or it may even cause temporary blindness. In the long-term it can cause cataracts, iris aging, glaucoma, floaters, retinal detachment and permanent blindness.
Naked human eyes can’t tell if a band pass curve is good or bad since UV/IR rays are mostly invisible. But a judgment can be made using the following criteria:
Band pass transmission color: High quality band pass looks more colorful (from blue to red) and more comfortable to human eyes than poor quality band pass. Since a manual or semi-manual production process can’t control the optical layer precisely, it’s hard to widen the visible light wavelength range while keeping UV/RI as low as required. Besides optical layer thickness control problem, a manual or semi-manual production process can not have many optical interference layers which means higher colorfull transmission, because of production cost.
How a band pass is made: Usually the quality of band pass made by fully automatic evaporation equipment is much higher, more consistent and more reliable than that made by manual or semi-manual evaporation equipment, because of different tolerances and process controls. A automatic production process usaully is capable of having more optical inerteference layers easily, comparing with a manual or semi-manual process. The hard-coating process, in which anti-erosion optical material is used, can withstand atmospheric environment longer than the soft-coating process, which is usually combined with manual or semi-manual evaporation equipment. The shelf life of hard-coating band pass (around 6 months) is much longer than that of soft-coating band pass (less than a month) during production.
Since the polarized outside of an LCD is a type of plastic film it’s easily scratched and difficult to clean. By using a glass Protect Lens we're able to make an anti-scratch and anti-smear ADF lens, which is crucial in rugged environments.
There are three processes to combine Band Pass, LCD and Protect Lens. The first is non-laminated process. Just simply put Band Pass, LCD and lens together and put glue at the edge area. There are two (or three) air gaps between Band Pass/ LCD/Protect lens. The second is glass-to-plastic lamination process: laminating hard plastic film on outside of LCD. But there is still an air gap between Band pass and LCD or LCD/LCD, and not full anti-scratching. The third is glass-to-glass lamination technology. Glue band pass with LCD and Protect Lens at one time. So there is no air gap between Band Pass/LCD and LCD/Protect Lens.
Glass-to-glass lamination is achieved by gluing the band pass, LCD and protect lens together at one time without any air bubbles, contamination or debris. The advantages of glass-to-glass lamination are:Band pass is protected from atmospheric erosion and acidic environment which can corrode the band pass.
Reduces haze on ADF: By reducing internal light reflection between band pass/LCD/protect lens, we considerably improve the image contrast.
Relieves dizziness problems: Reduction of haze reduces dizziness, so users will be more comfortable with crystal clear ADF's.
Avoid eyesight damage: If welder looks through non-glass-to-glass-laminated ADF it's like wearing dirty, foggy glasses which can damage eyesight over long periods.
Increased product life and reliability. By gluing all parts together we increase the strength of the ADF.
Anti-scratch and anti-smear lens: Since the outside of glass-to-glass laminated ADF is glass rather than plastic it makes the ADF much less likely to scratch or smear.
Shade is a measurement unit of visible light transmittance for special welding and very dark measurement application. If the shade number is higher, the transmittance is lower and the arc is larger.