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ILLUMINATION:

LEDs light up large format scanning's future!

CCD wide format scanner makers drop fluorescent tubes for LED benefits

CCD (charge couple device) wide format scanner design has traditionally used fluorescent tubes which are slow to warm up. One reason for the growth in popularity of CIS (contact image sensor) scanners is their use of long-life LED (light-emitting diode) illumination to provide benefits like instant-on scanning and low power consumption.

White LED

In releasing its new generation, extra-wide CCD SmartLF Gx+ 56 wide format scanner, Colortrac claims that its "major new innovation" is its use of an LED illumination system. It has a point. LED-powered lighting represents the future of large format scanning. Those using fluorescent tubes represent the past.

However, the first company to use white LEDs in a CCD wide format scanner was not Colortrac, but Image Access, the German manufacturer of the WideTEK series. Image Access first introduced white light LEDs in February 2007. Its rivals have been slow on the uptake.

No more. Contex is also jumping on the bandwagon, offering a stop-gap "LED light cartridge upgrade" for its fluorescently lit HD Series CCD scanners which it says "provides sharper scans, lasts longer, reduces power consumption by up to 33%, features true instant-on, and is easy to install". Clearly, an LED light source has much to offer compared to fluorescent tubes.

LEDs now lead a mini-revolution in large format scanning. Driven by the hugely practical benefits of LED lighting, there is now an unstoppable movement within the scanning industry to replace the once standard fluorescent tubes with a white LED light source in CCD scanners.

CCD and CIS LEDs

In a CIS scanner there are three types of LED - red green and blue (RGB). A colour image is built up by the red, green and blue LEDs being rapidly strobed onto the document. RGB LEDs do not provide a wide colour gamut (number of colours) or a high dynamic range (gradations of tone).

A traditional CCD scanner uses white light flourescent tubes which are shone through red, green and blue colour filters to create colour images. This method is much more colour sensitive than RGB LEDs and allows a wider colour gamut and a higher dynamic range to be captured with greater accuracy. CCD scanners using LEDs work in the same way. They use white LEDs instead of RGB ones and shine white light through colour filters to capture colour on a document.

CIS wide format scanners are suited to scanning monochrome, greyscale or limited colour technical documents, maps and artwork where high colour fidelity (very accurate colour reproduction) is not needed.

CCD scanners - whether lit by white LEDs or fluorescent tubes - are suited to colour scanning where accurate colour reproduction is needed.

Advantages of LEDs over Fluorescent Tubes

Fluorescent tubes used in CCD-based wide format scanners need to be warmed up, typically for an hour or more, in order to stabilise the light source for high fidelity colour scanning.

Fluorescent tubes are comparatively energy inefficient. Because of the warm-up time, a fluorescently lit scanner needs to remain on all day once it has been switched on, if it is to be used again. LEDs only come on while the scanner is actually scanning. Some CCD scanners can power down into a low-energy sleep mode. This does not remove the need for warm-up if high quality colour accuracy is needed, nor does it make the CCD scanner energy efficient enough to qualify for ENERGY STAR® status.

At present only scanners using LEDs can claim to be truly "instant-on". Further, only scanners with LED illumination are able to qualify for full ENERGY STAR power saving status. There are NO CCD scanners using fluorescent tubes which are ENERGY STAR qualified. The mechanics of their design simply forbid it.

LEDs are more robust than fluorescent tubes and cope better with the knocks and bumps of transportation. They also last longer. Colortrac estimate that fluorescent tubes have a useful working life of about 8,000 hours. As a result, fluorescent tubes are generally regarded as a consumable item likely to fail every 18 months to two years. LEDs, however, are expected to outlive the scanner.

In comparing the new LED illuminated SmartLF Gx+ 56 to their previous generation of SmartLF Gx CCD scanners with fluorescent tubes, Colortrac say that the new LEDs use 30% less power in operation and 94% less when idle. Colortrac and Image Access agree that the working life of an LED system is about 50,000 hours or "5 years constant operation, 24 hours per day, 7 days per week - with no vacation!" say Colortrac.

As fluorescent tubes contain mercury, scanner operators are required to dispose of them in a responsible, environmentally-friendly way. Given the pressure of working in a CAD drawing office, we wonder how many companies care to dispose of them with due care and consideration? LEDs take the responsibility off the scanner owner and make our need to ask such questions irrelevant.

Overall, LEDs have less issues and many more positive benefits.

In summarising the benefits of LED illumination within the new SmartLF Gx+ 56, Colortrac claim that they provide their customers with instant-on colour calibration, lower ENERGY STAR qualified running costs, lower consumable, service and disposal costs and greater reliability due to the LEDs' robust, solid state, digital design.

CCD scanners which use fluorescent tubes today are soon to be made redundant.

Let the buyer beware.

To see which scanners use LEDs and which use fluorescent tubes, download our large format scanner comparison chart.