The beautiful holographic stickers, which is the most common kind of hologram in Hong Kong are appealing.

“Holographic stickers help us sell flag,” said Miss Chow, Community Relation Assistant Manager of the Community Chest of Hong Kong.

In fact, holographic stickers are mainly used for anti-counterfeit purpose.

Hologram is not a common word. In Greek, “holo” means complete, “gram” means message.

It is a way of recording images by laser. Unlike photograph, hologram can record 3D images, that is where the word hologram comes from.

“Hologram is fundamentally different from ordinary printing, since hologram needs no ink at all,” said Herry Chung, Technical Developing Manager and Production Technical Consultant of Laser Art Studio Ltd, a hologram manufacturer in Hong Kong. “Also, hologram gives a much higher resolution.”

For this reason, Varsity cannot print a hologram for readers to see. But readers may find one on credit cards.

The process of producing a hologram is very delicate. They studied and imported this technology from the United States, Germany and Japan from 1992 to 1993.

Another important use of hologram is for military purpose. Since it can store lots of information, one can use satellite to take a holographic photo and enlarge the picture without losing resolution.

“Though we don’t produce it for military purpose, we do produce holographic lens for optical use,”said Mr. Chung.

The process of making hologram can be very simple. But making high quality hologram is extremely delicate.

The secret behind is that it uses an optical phenomenon called light interference to record the image.

It needs a coherent light source. So far, only laser can satisfy this criterion.

In a hologram factory, the manufacturing process for stickers involves five steps which are sampling, mastering, electro-forming, embossing and finishing.

The process for other holographic products is different, but the concept is the same.

Clients simply send a picture of the image they want to the manufacturers.

In the sampling process, manufacturers will make a plastic film for each colour of pattern, say, a film for eyes, another film for ears. A glass plate will then be made for each plastic film.

Then comes the mastering process, which means recording the image wanted on a plate. For simplicity, this plate can be regarded as the film in holography.

In the mastering room, no light except the laser is allowed.

“An error of one over 140,000 inches means the process has to begin all over again,” said Mr. Chung.

During mastering, no man will be allowed in the mastering room, as their temperatures and voices will destroy the process.

 

The process of using laser in the hologram is demonstrated.

“We remote-control the process in another room,” said Mr. Chung.

During the process, the laser beam will be diverged by a lens.

This alternate high and low intensity pattern of the light waves will cause the chemicals in the film to react.

After the film dries up, it will be coated with a nickel layer for electrolysis in the electro-forming process.

The intensity pattern of the film will be reproduced to the nickel layer.

Electro-forming allows mass production. The “mother” nickel plate will be used as a mould to give birth to another nickel plate “son”, and so on up to five “generations”.

With embossing, the interference pattern will be cut on an aluminium foil.

“The temperature, pressure and speed for embossing have to be carefully controlled,” said Mr Chung. “The error in temperature should be within 3 degree Celsius, and the pressure should be six tons per square inch.

”Finally, adhesives are put on the aluminium foil to make it an ordinary sticker with holographic effect.

By hot stamping, these holograms cannot be peeled off.

“Now, even we can't reproduce an identical interference pattern since the pattern is totally random,” said Mr. Chung.

Hence it will make it extremely difficult for criminal to produce a holographic sticker, or to peel it off and re-stick them on their pirate products, because the stickers will be destroyed after peeling.

“Our customers have to show their certificates or licences to prove that they are its copyright owners,” said Mr. Duncan Shiu, Marketing Manager of Laser Art Studio Ltd.

The history of hologram is about 30 years only. Its potential is very great.