Wednesday, December 26, 2007

Computer screen mounted desk lamps?

Philips Ambilight TVPhilips "Ambilight" range of flat panel TVs have lights around the edges and on the back. The light level and color is automatically adjusted so the lights match the brightness and colour of the image on the screen. This is claimed to reduce eyestrain. If this works, perhaps the same technique could be applied to desktop LCD computer screens. Apart from reducing eyestrain, this might be a way to provide very power efficient lighting for offices, schools and homes.

The latest Philips "Ambilight" range of flat panel TVs have a translucent bezel around the screen with colored LEDs in it. These are adjusted to blend with the image on the screen. Perhaps the same approach could be taken with LCD screens in offices. A row of LEDs could be placed around the display. These would be automatically adjusted to suit the image on the screen and the room lighting level.

A much simpler approach would be to have some holes in the enclosure to let out some of the light from the back light of the LCD screen. Some Apple notebook computers illuminate the logo in the lid this way: the logo is made of translucent plastic, allowing the backlight to show through. Using this approach the lighting would not change color or brightness with picture content, as the Phillips system does, but would automatically change brightness in step with the backlight.

Both LCDs and the fluorescent back lights used in LCD panels are very efficient. If the lights on the screen could replace some (or all) of inefficient incandescent room lights, this would save on power. Lights on the screen could be powered from the screen power supply, from the computer or from a separate mains supply.

Of course, placing lights on the screen is contrary to usual recommendations for office lighting, which have the light at high intensity, above and behind the desk. However, these recommendations were developed at a time when office workers read from paper flat on a desktop of several square metres. These guidelines may need to be revised where an LCD screen and keyboard is used for most work, with a desktop area of one square metre or less

Lights on an LCD screen should be sufficient to illuminate one square metre or so of desktop used around it. This would be enough to see the keyboard in front of the screen and some paperwork on either side, plus use the telephone

An adjustable low power fluorescent or LCD task lighting, might be used to supplement the screen light. This could be USB powered, or from the screen or computer power supply, to prevent having to provide a separate mains power supply.

Low power room lighting

If each desk is provided with general and task lighting, then the room light can be lower. The room need only be bright enough to allow people to see their way around and prevent glare. This could be achieved by using low wattage LED or fluorescent lights which double as emergency lights. This could be used to lower the installation and running costs of the lights.

Offices are commonly equipped with two lighting systems: a high brightness mains powered one for everyday use and a low voltage battery backed system for emergency use. The mains powered system provides reading level light everywhere in the office. The emergency system provides only enough illumination to find your way to an exit. The emergency lights need only operate from batteries for a few minutes and so need not be efficient or provide glare free lighting.

The standard room lights could be replaced with efficient low wattage fluorescent or LED lights, designed to provide a comfortable level of illumination for general office use, but not bright enough for reading or close work. Some, or all, of these lights could have battery backup, so they would also be used as the emergency lights. The new lights might be retrofitted into existing fittings. Very small LED and fluorescent light fittings can be added to the existing ceiling surface or suspended from it. The lower power required would also allow less cabling to be used, lowering the installation cost.

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