Displays
voltage DC/AC inverter to drive the backlight. Some industrial LCD displays nowalso feature on board LED controllers enabling zero to 100 per cent backlight dimming.
Will the lifetime of LED backlights have an impact?
LED lifetime characteristics are important,with estimations of between 70K and 100K hours being quoted by displaymanufacturers. Close scrutiny is often necessary to determine exactly howthat lifetime is specified: different ratingsmay be the result of the brightness value used as the initial reference point. A 100K hour lifetimewill often refer to a final brightness at 50 per cent of theminimum specified brightness,whereas a 70K hour lifetime often refers to 50 per cent of the typical brightness.
Is display size and format important?
Themechanical size and aspect ratio of the display is likely to be determined by the systemor equipment design. Some industry standards do prevail however: 3.5, 5.7, 6.5, 10.4 and 12.1in are all commonly availablewith a 4:3 classic aspect ratio.Wide format 15:9 aspect ratio displays such as 7.0, 8.0 and 9.0in are being adopted by HMI, in-vehicle and epos applications. Newindustrial LCD displaymodules also feature compactmechanical dimensions, since a slimmechanical bezel allows external switches and input devices to be closely associatedwith the display image.
What about the electrical interface?
Many industrial applications will use a single board computer (SBC), often with high levels of functionality allowing backlight control and the ability to drive display resolutions of VGA and above. There are two standards for the electrical interface: RGB CMOS and LVDS. These can both be implemented to use either six or eight-bit data which enables a colour palette of up to 262K and 16.7Mcolours respectively. The implementation of LVDS display interfaces on SBC and industrial LCD displaymodules is becoming mandatory as display resolutions and data rates increase and the need to reduce EMI becomes necessary.
Industry standard sizes prevail, including the 5.7in format
Should environmental factors be considered?
True industrial environments can present difficult challenges for displayswith extremes of temperature, ambient lighting conditions and mechanical shock and vibration. An industrial operating temperature range of -20 to 70°C covers the variations likely to be found inmost outdoor and indoor environments, although an increasing number of industrial displays nowhave a range of -30 to 80°C,which provides additional robustness where needed.
www.hitachi-displays-eu.com
April 2011 | 15
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