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How does Optical Filters inspect their windows?

Optical Filters has developed the Optical Inspection Standard (OIS). The content of this standard is based on our experience with the materials that we use, the process of each job, and the expectations of our customers.

What are the benefits of laminating glass when plastic is not an option?

Laminated glass offers high levels of impact resistance equivalent to safety glass. If laminated glass were to break, the shards would adhere to the adhesive layer rather than scatter about.

How are glass and plastic windows compared?

Comparable in many ways, the use of plastic or glass windows is often dependent on the project itself.

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Window Features Laminated Glass Plain Laminated Polycarbonate
Weight Typically heavier Light weight
Flammability UL94 Rated Excellent Excellent
Safety and Impact Resistance Good Excellent

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Abrasion/Scratch Resistance Laminated Glass Laminated Polycarbonate with Hard Coating
Plain Excellent Good
AR Optical Coating Good Good
Dispersive Etch or Coating Excellent Good

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Chemical Resistance Laminated Glass Polycarbonate
Plain Excellent Poor
AR Optical Coating May react to some cleaning products Good (with Hard Coating)
Dispersive Etch or Coating Excellent Good (Resistant to common cleaning products)

Options for Reducing Front Surface Reflections

  • Dispersive etch or AR coating
  • Dispersive coating

How can privacy be incorporated into my window?

A light control film (LCF) or blur film can be added to any window, this controls the position from which a display can be viewed.

Do all displays emit Electromagnetic (EMI) and Radio Frequency (RFI) Interference?

All displays emit some level of radiation. What is important however, is that these levels do not exceed the levels set out by the relevant standard. These levels are specified as being acceptable limit to ensure that the performance of an electronic or electrical apparatus will neither disturb that of another apparatus nor be degraded by electromagnetic disturbance.

EMI from an LCD or LED display originates from the internal electronic circuitry and is channelled through the open display. This is why a shield is either required across the aperture or on the circuitry itself.

EMI on a plasma display emanates from the display itself and the reaction between the phosphors in the subpixels and the gas in the plasma state. This cannot be dealt with at circuit board level.

How does a shielded window work?

The purpose of a shielded window first and foremost is to be able to see through it to the display. Depending upon the frequency, the wire mesh or conductive coating absorbs and conducts the interference signal. The effectiveness of the shield, measured in decibels (dB), is determined by testing the level of the signal passing through the aperture both before and after fitting the shield and taking the difference.

What is Electromagnetic Compatibility (EMC)?

Electromagnetic Compatibility is the ability of two electrical or electronic systems to co-exist without disturbing the correction operation of each other.

What is the difference between conventional meshes and EmiClare™ mesh?

Conventional meshes are specified by the Open Peripheral Interface (OPI) and their material (copper or stainless steel). There is very little difference between all of the mesh types, though copper mesh is preferable below 200 megahertz (MHz).

EmiClare mesh offers high levels of shielding and light transmission while eliminating optical distortion patterns associated with other meshes across any range.

How is using EmiClare EMI in my project beneficial?

The decision to choose between a mesh window and conductive coating is based upon the shielding effectiveness necessary for the project. A mesh window typically offers 60-80 dB of attenuation, while a conductive coating would offer <40 dB.

Conductive coatings are often favoured for their high light transmission and optical clarity. EmiClare EMI shielded windows are the zero-compromise solution to this trade-off. Being a mesh window, it has high levels of shielding, but the mesh configuration has been optimized for high light transmission while eliminating the optical distortion patterns often associated with typical mesh windows.

How do I ground my window to a display?

There are several ways of achieving this, here are the two most common:

  • The most EMI efficient method is to use a mesh extension as it eliminates interface losses from various gasket options.
  • The use of a conductive silver busbar termination to the window, then, clamping the window to a conductive bezel. A conductive gasket or silver loaded epoxy adhesive can be used if a match between the silver busbar and the bezel is not achievable.

What if my EMI shielded window is not offering adequate attenuation?

  • Check that the window is installed properly; no gaps should be present between the window and the bezel.
  • Ensure that you are using the correct conductive adhesive/gasket.
  • If the window is terminated with a silver busbar, you can try using a window with a mesh extension. Mesh ground directly onto the bezel will yield better results.

How can frosting or misting be prevented on the front of a display?

ThermaClare is a transparent heated window with the option to add EMI shielding.

How can the contrast enhancement on a display be improved?

  • Utilize coloured filters (Available in neutral grey or a colour matched to the display)
  • The use of a circular polarizer allows colour to show through with deep saturation by cutting glare and reflection
  • Add a non-glare or anti-reflective finish to the front of the display to reduce surface reflections

What does a circular polarizer do?

Circular polarizers are efficient contrast enhancement filters that improve the sunlight readability. Ambient light passing through a circular polarizer is transformed to a polarized circular motion, which when reflected from the surface of a display is rotated through 90° and can no longer pass back through the filter as the polarization of the reflected light is out of phase with the polarizing filter.

The effect of this is that the background to the display appears dark blue or black. The signal from the display has not been polarized and appears very bright against this dark background.

Can you use a circular polarizer on an LCD display?

Though possible, it is important to be aware that LCDs contain linear polarizers; the polarizing element of a circular polarizer must be correctly aligned with the polarizer of the LCD to avoid colour distortion.

What does a linear polarizer do?

Linear polarizers confine light to a single plane. This linearly polarized light can be modified to suppress reflections and to eliminate glare in a variety of applications.

What is moiré fringing?

This is an optically distracting black and white pattern caused by optical interference between mesh and pixel structures. This can be reduced with conventional meshes by rotating the mesh to minimize the optical interference.

This can be eliminated by using EmiClare mesh, which changes the aperture shape from square to rectangular.

What type of window is suitable for food production lines?

A polycarbonate laminate or glass in a polycarbonate or polyester sandwich laminate.