Kodak Research Leads to Lush Images in Seconds with the KODAK Photo Printer 6800

When you walk into a store and insert your digital media card into a new KODAK Picture Maker G3 kiosk, it only takes a few touches on the screen before vivid, glossy prints pop out. But in those few seconds, between the "click" of the media card and the "clunk" of the final photo, a myriad of sophisticated operations and complex chemical formulations are put into play-all to produce gorgeous images you can enjoy for years to come.

The KODAK Photo Printer 6800 inside the kiosk is what makes it all happen. This state-of-the-art thermal imaging system combines Kodak scientists' deep expertise in formulating chemical dyes, coating technology, image processing, and advanced software algorithms, with more than a decade of experience in retail thermal imaging.

Over the past two years, Kodak's researchers have dramatically shortened the time needed for creating a high-quality image to a mere 11 seconds per print. However, the shorter process presents new challenges due to the exceedingly rapid transfer of heat, threatening the quality of the overall image. Kodak's scientists have devised a host of sophisticated advancements to counteract these limitations. The result is vivid, crisp pictures in a matter of seconds.

Here's how it works. The KODAK Photo Printer 6800 creates an image by bringing specially coated paper into contact with a dye donor ribbon under a thermal print head (Figure 1). The donor is a very thin polyester sheet with three dry color patches in series-yellow, magenta and cyan- followed by a clear over-laminate patch, each one the size of a 4x6 print. The printer applies the colors across the entire area of the image in three separate passes: first the yellow, followed by magenta and finally the cyan patch. The different combinations of these colors create the complete palette of hues and shades needed to produce incredibly vivid, lifelike tones.

The paper is kept in precise registration by hundreds of mechanical teeth on a roller that moves the paper underneath a stationary thermal print head. To apply the dye, the thermal print head presses the donor ribbon against the paper, forcing positive contact between the two. Thousands of heated pixels on the print head apply heat up to 200 degrees Celsius (392 degrees Fahrenheit) to drive the dye onto the paper. The higher the heat, the more dye is transferred. For example, a red poppy in a picture requires more heat to create than the light blue sky in the background.

During printing, the thin polyester donor ribbon is in close contact with the extremely hot thermal head. The higher temperatures required for fast printing increases the chance of the ribbon being weakened by the excessive heat. Researchers have developed a special slip layer that is applied to the back of the donor, enabling the donor to slide past the print head without developing small wrinkles or folds that would create unsightly color lines on the image and ruin it (Figure 2).

Wrinkles in the donor ribbon can lead to unwanted lines in the picture.

Under certain conditions, the separation of the donor and receiver after printing can cause undesirable defects, especially at such high printing speeds. The inclusion of special additives-developed over many years of meticulous experimentation and research by Kodak's scientists-help to eliminate such printing artifacts by ensuring that just the right amount of dye is deposited to produce a continuous tone.

During the entire thermal printing process, special software algorithms are constantly at work to deliver crisp, sharp edges at the transitions between dark and light areas. At higher printing speeds, the thermal print head retains heat and has a tendency to transfer too much dye as it moves from a darker area to a lighter one. That tends to create a smudge around dark objects set against a lighter background, such as the image of a black cat lounging on a cream sofa.

To keep excess dye from "smearing" into the lighter area, the software scans the image data in real time, searching ahead for these dark/light junctures. When one is found, the software adjusts for the excess heat by changing the printing conditions to exactly compensate for the unwanted dye transfer. Now the edge of the cat will be distinct and sharp against the cushion, just as it is in reality.

Once all the three color patches are applied, the last step is to cover the picture with the laminate layer. This clear patch was precisely formulated by Kodak researchers to provide maximum fingerprint protection, waterproofing, and UV protection from bright light. The laminate has the added benefit of producing a high-gloss finish to enhance the beauty of the picture.

All these advances in thermal imaging, chemical dyes, coating and advanced software work in concert in the KODAK Photo Printer 6800 to produce lush images at maximum imaging speeds. Now, only mere seconds elapse between selecting an image at a KODAK Picture Maker G3 kiosk and the emergence of a final, glossy print that can be admired and cherished for years.