Application Of ND filters in LCD And CRT Panels For Aviation

By Sean Dinkel, HOYA

Reflected sunlight is an omnipresent hazard to pilots during daylight hours, hindering their ability to read cockpit instrumentation and displays, particularly at cruising altitudes above the clouds. This reduced instrument visibility impairs operational safety by delaying or preventing pilots from accessing important information on cockpit displays.

A number of techniques have been attempted to address this problem, from pilots simply shielding the display with a hand or wearing sunglasses to attaching a cover to the display to shield the screen. These workarounds create as many unsafe environments and situations as they prevent, and they do not correct the root problem: the presence of the external light directly striking and reflecting off of the display.

It is possible to reduce external light reflection from the display surface by using a filter with an anti-reflective (AR) coating. However, this approach alone cannot eliminate the reflection for the entire visible light region as well as for various angles of incidence. It also is possible to brighten the display by increasing the backlight’s synchrotron radiation intensity if using a cathode ray tube (CRT) display.  But, brightening the display can increase power consumption and prematurely deteriorate the light source, as well as create “burn-in” defects on the display surface.