All done with mirrors

Technology developed to improve bar and datacode readers could also be used to put tiny film projectors inside your mobile phone. Jon Excell reports.

It’s the weekly shopping trip to the supermarket. A mad dash up and down the aisles, a quick recce to establish the location of the speediest cashier – and then you join the queue.

Everything’s going smoothly until that impulse packet of mackerel totally confuses the barcode reader. The ’till beacon’ is illuminated, a chorus of tutting begins behind you, and Kevin from customer services is called in to sort things out.

Thankfully, scenarios like this may soon be a thing of the past, thanks to a data scanning system developed by engineers at Germany’s Fraunhofer Institute.

Said to be more accurate, faster and cheaper to manufacture than current technology, the new system is based on a micromechanical scanner mirror that oscillates 250 times per second, taking 500 readings.

Existing technology is based on precision-engineered mirrors, which are rather bulky and typically operate at around 20Hz. Because of their bulk, increasing the frequency beyond this can be an expensive process. Dr Harald Schenk who headed the project at the Fraunhofer Institute explained that a faster reading means that much more precise information can be provided.

The device is produced using conventional semiconductor manufacturing techniques. The mirrors are etched in a silicon substrate, complete with drive electrodes; even the mirror holder is made of semiconductor material. The whole process lends itself perfectly to high-volume, low-cost production said Schenk.

The electrodes bend around the circular reflecting surface of the mirror without touching it – the mirror plate and electrodes are extended to form tiny interlocking fingers. The electrostatic driving force sent to the mirror plate by the electrodes is thus amplified, allowing the drive voltage and power consumption to be minimised. Indeed, an input of just 15V will move the device through a scanning angle of 50 degrees.

Schenk said that the product is now ready for commercialisation, a decision that rests with an industrial partner whose identity is currently under wraps.

‘The product has been fully qualified at our institute – all the reliability issues, the process qualification and product qualification are finished,’ he said. But he did reveal that the first application of the technology will be in barcode or datacode scanning – possibly in a retail environment.

Schenk added that the technology could also be used to build tiny film projectors for mobile phones that would enable users to project video sequences on to any available surface.

Following the development of a prototype device capable of projecting images with a resolution of 256 x 256 pixels, Schenk’s team is building a new demonstrator with VGA (video graphics adapter) with a resolution of 640 x 480 pixels. He said that he believes it will eventually be possible to go up to SVGA (super video graphics adapter) resolutions of at least 800 x 600 pixels.

The current demonstrator device is not small enough for a mobile phone, however. ‘We were focussing on the principle rather than size,’ said Schenk. But he is confident that it will be relatively easy to shrink the device down. He confirmed that he is discussing the concept with mobile phone manufacturers, but declined to disclose exactly who.