Technology explained

OKI Printing Solutions Digital LED Technology

02/10/2000

OKI Printing Solutions have been using superior Digital LED technology in page printers for many years, see why our competitors are now changing to this leading technology

For many years, OKI Printing Solutions have been using Digital LED technology in their page printers.

What does this part of the printer do?

To understand this completely would require an understanding of the electrophotographic process, but this can be summarised:

A light source controlled by the printer's CPU shines light on a light sensitive drum creating an attractive charge like a magnet. The drum rotates past a toner store attracting toner particles where the light shone. The drum next rotates past paper to which the toner is transferred, making the image that is finally fused onto the paper.

The light source in the process can either be a relatively large laser unit or a compact Digital LED Array.

Here is the complete Digital LED light source in an OKIPAGE desktop printer with its top cover open.

OKI Printing Solutions scientists examined these two types of light sources carefully and conclusively decided that, the Digital LED light source was far superior. It consists of an array thousands of individual digital LED light sources spanning the width of the image drum, shining through focusing lenses directly down onto the drum surface.

Superior image quality through more accurate drum illumination

The improved image quality can be explained by the design of the two types of light source. A laser source consists of a large relatively heavy, but delicate arrangement built into a large case. The case contains a single laser light source and a complex system of lenses and rotating mirrors that deflect the laser beam across the drum as it rotates. Complex timing is used to ensure that the laser can still produce a horizontal track across the drum surface while the drum continuously rotates. The edges of the drum are further from the laser than the centre and so careful parallax correction must be employed.

Laser light sources for laser printers have improved over the last few years and many of the original print quality issues related to the technology have now been resolved however Oki still believe that the Digital LED source is still superior. This is why:

The Digital LED source consists of thousands of individual solid state Digital LED light sources that shine directly through focussing lenses onto the drum surface. The array stretches right across the drum thereby eliminating any possibility parallax errors or timing errors.

Superior print quality through smaller dot size.

At 1200dpi, a theoretical ideal dot size would be calculated as:

25.4mm (1 inch) divided by 1200 = 21.2 ìm (21.2 micrometers)

Laser heads can produce dot sizes of 60ìm whereas OKI Printing Solutions Digital LED technology can produce dots as small as 34ìm

The following three images show some 2 point text printed with laser and Digital LED technologies. (2 Point text is about 0.7mm tall !)

Oki LED printer

Lexmark Optra S2450 (Laser)

HP Laserjet 4000T (Laser)

Superior reliability

The Digital LED light source has no moving parts and therefore is ultimately more reliable. In fact OKI Printing Solutions are so confident of the reliability of the source, they guarantee it for the life of the printer!

The Digital LED light source allows higher print speeds at higher resolutions than traditional laser light sources...

Superior Speed

As shown above, a laser head must scan the laser across the image drum for every line of data. There is a limit to how fast the drum can be rotated while maintaining the horizontal scanning integrity. As Digital LED technology utilises multiple light sources, there is no 'scanning' action needed, so Digital LED technology does not suffer this disadvantage and can therefore print faster at higher resolutions. This graph shows how print speed is not related to technology for Digital LED technology but laser technology needs to slow down as resolution increases.

In summary Digital LED Technology advantages:

  • Smaller, more compact size allows Oki to build smaller printers using less raw materials and less world resources.
  • Smaller dot size gives sharper crisper text and graphics
  • More accurate light sourcing gives better quality imaging
  • Technology inherently able to work faster giving higher speed printers at higher resolutions
  • Simple no moving part technology gives incredible robustness and reliability

Oki Digital LED technology is present in all our page printers. The advantages of our technology become even more relevant in colour printers - see the explanations of our Single Pass Colour technology.

In fact Digital LED technology as a light source is so good that some of our competitors are now starting to adopt it for their own high quality printers!

A scan from one of our major competitor's literature:

But OKI Printing Solutions have been pioneering the use of Digital LED technology in printing devices for many years!!

Printing Ideas