Medical Electronics I Case Study
Farsighted system development
CIE looks at an innovative mobile vision screening device that was developed using a credit card-sized COM Express mini module from Kontron
O
ptovist from Vistec AG is a patented mobile vision screening device for vision testing which features innovative computer technology. b-plus GmbH, which specialises in embedded designs, was commissioned with the development of the device’s electronics. Their brief was to find the right computing platform providing high performance, the integration of specific functions and dual display support - all of which needed to be housed in the minimum amount of space. b-plus selected the CPU module in the COM Express standard from Kontron - a product that has been available for a number of years. Correct vision is crucial, especially in the workplace and in road traffic and there are various accepted guidelines which stipulate, for example, when employees have to have their vision tested, either to check their suitability for a certain profession, i.e. as a pilot or vehicle operator, or to detect any type of defective vision or inadequate vision correction with glasses.
For these occupational medical checks
which predominantly are carried out by companies' and works' doctors, mobile vision screening devices became established in the market during the 70s and 80s.
Analogue goes digital In the past, there were limitations on the number of optotype tests which could be carried out on vision testing equipment as these were only available either as optical discs, as slides or as printed foils. This purely mechanical design hinders flexibility when selecting different vision tests and it is comparatively costly when adaptations have to be made to comply with new testing regulations or with special customer requests.
This was the reason why Vistec set about developing Optovist, a mobile vision screening device which presents optotype tests digitally on the integrated high resolution 1.8" LCD display. This paves the way for a practically unlimited variety of vision tests, including vision acuity, eye position and even colour sense testing. The series of tests can be easily changed to conform with updated testing regulations or in various national markets where different regulations have to be
38 October 2013
Custom design vs. Computer-on- Module
Flexibly adjustable
A further advantage is that the height of the new system can be flexibly adjusted which ensures extremely ergonomic handling and optimal test results. Height adjustment of the Optovist is carried out electrically to cater for the subject's size etc., resulting in particularly comfortable testing environment. Furthermore, the internal display which provides the optotypes, can be tilted continuously. This makes vision testing much more comfortable for multi-focal and progressive lenses wearers. Subjects can even carry out adjustments themselves by using a rotary knob on the device thus obtaining the optimal test field position according to his visual aid – i.e. for looking straight ahead to test farsightedness or to check a 40cm reading distance at a tilted test field angle of 35°.
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has a separate high resolution operating tablet with touch control, which makes operation as intuitive and easy as it is with a modern smartphone or tablet PC. Apart from the intuitive control concept, carrying out the vision screening is self-explanatory and promotes secure operation thanks to the written instructions and symbols on the 17.8 cm/7" sized high resolution touch display.
New hardware
So the demands on the hardware were clear. First and foremost a small form factor with a low power dissipation processor technology was required, as the Optovist vision screening device had to keep to a small footprint (39 x 24 x 44 cm) in order to be really manageable and portable. Further ticks on the specification list had to be its light weight and a high level of
Right at the start of the planning, the question arose as to whether it made sense to develop a completely new customer- specific board - especially due to the requirements in terms of space-saving design and the specific interfaces. It quickly became clear that a solution with standardised Computer-on-Modules and individual carrier-board would result in significant advantages in comparison to a full custom design.
For one thing solutions based on compact COTS solutions are not just as space-saving but they can be realised much faster and more cost-efficiently than individually developed designs. Apart from that future-safety of the new system design was right at the top of Vistec's list of requirements. That meant that the selected hardware had to be available years from now and upgrades can be made totally hassle-free – while maintaining full hard- and software compatibility to the existing designs. Simply exchanging CPUs and chipsets on full custom boards is no easy task. COTS modules, however, can be easily changed
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adhered to. Customer-specific testing is easy to carry out as well. All this is possible with one completely digital device. In addition, over 28 integrated light diodes can carry out a field of vision measurement which underlines the versatility of this efficient solution.
Multi-focal glasses wearers often experience problems with other systems without the tilting display feature when testing of nearsightedness was being carried out. With the Optovist it is easy to determine whether special visual aids, like for example for VDU glasses for screen work, are necessary.
Digital touch display
For operating and configuring vision tests the device can be connected via USB to a PC or notebook. To enable even more convenient operation the new system now
robustness without vulnerable fans for year- long, reliable mobile usage. Apart from the ultra-small format, the new hardware had more than anything to deliver good performance: fast and precise graphic performance was an absolute necessity. Last but not least dual display support
was a requirement, so that high resolution graphic signals could be attached to transmit high resolution graphic signals both to the internal display for the eye test as well as to the external operating panel. Furthermore, specific interfaces were required, to connect the operating panel via a cable, for the control of the stepper motors for the electrical height adjustment of the device and for the control of the 28 LEDs for the orientating field of vision measurement. In order to accommodate all these
requirements, a standard single board computer was out of the question. As a result Vistec looked for an embedded design partner with the right hardware and design-in know-how to realise this custom design on the baseboard – from the joint planning of the system right up to the final realisation of the serial product. In b-plus, Vistec found a partner with great expertise in connecting displays and a long list of references with board designs and firmware solutions as well as in housing integrations.
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