A modular light-emitting diode system enables flexible lighting arrangements. Find technical details at: DLI/VarioFlash IR12 and DLI/VarioFlash W12.

Industrial vision uses light to measure. The reflection of an illuminated widget typically passes through a lens of other imaging system and eventually hits a CCD chip inside a camera.

The CCD chip is merely a two dimensional matrix of light detectors which converts the spatial intensity distribution into electrons to form a 2D image. This 2D image is spatially discrete but analog in terms of grey levels.

The on-board camera processor then proceeds to convert this image into a video signal and usually outputs it through a connector on the rear of the camera.

Finally, the connected computer uses a frame grabber or other digital interface to create a digital image from the video signal input.

Once this image has been created, the computer processes and/or stores the acquired image. To monitor an industrial process, for example, software algorithms derive information from the images, such as dimension measurements and pattern or error recognition.

One of the most common mistakes made by budding imaging trainees and professionals alike is that they tend to concentrate their entire efforts on software which reduces shadow effects in the acquired image, rather than reducing those shadows in the first place using proper lighting.

Preventative medicine is the key here! The only way to get good results in image acquisition and processing is to get an intimate interplay between optics, mechanics and electronics.

Mess up in one area, and the images you produce are just about worthless.

Whereas there are hundreds of papers discussing optics, cameras, frame grabbers and software, this article is about lighting and in particular LED lighting.

So, exactly what are the advantages of LED lighting?:

• As LEDs require a DC power supply, they do not flicker.
• Their light emission is monochromatic and thus chromatic aberration is completely avoided in the lens of an imaging system.
• Their total cost of ownership (TCO) is low, as they are both very fairly priced and require little power and are just about maintenance-proof.
• Typical life expectancy of around 100,000 hours.
• High light intensity output combined with low mass and small size.
• Heat dissipation does not occur; neither does the generation of noise, vibration or high voltage.

One key factor that many manufacturers of lighting systems have failed to recognize is 'diversity'.

In practice there are not any off-the-shelf lighting solutions which can be taken directly from their packaging and put to work straight away.

Take for example the classical ring light - the number of parameters which may need to be adjusted, but which cannot be set is enormous: The diameter of a right light is static: it cannot be set by the end user.

Say you have to change the setup of your machine vision application and as a result your ring light has to illuminate a larger area and as such it's diameter must be increased.

The only way to get a ring light with a larger diameter is to order another one from the manufacturer. This costs time and is expensive.

Another non-variable key factor of a ring light is the angle at which the LEDs are mounted. Again, if you suddenly need your LEDs at a different angle, you need to buy a new ring light.

There is a whole multitude of other parameters which cannot be changed on a ring light, making their implementation in mission critical machine vision processes a very hazardous occupation.

With this in mind we, here at The Imaging Source, set to work developing the VarioFlash. The design of this modular LED lighting system was based on four design criteria:

• Only two types of modules are offered, one with infrared LEDs for monochrome and the other with white LEDs for color.
• It must be possible to realize various lighting situations (inter alia front lighting, silhouette projection, dark field) using modules of the same type.
• No special, nor expensive control unit is needed: the modules themselves are strobes.
• The modules must withstand the toughest industrial environments.

To read more about this remarkable new product, as featured in the current edition of Photonics, take a look at: DLI/VarioFlash IR12 and DLI/VarioFlash W12 Here you will find detailed product information, user and expert manuals in both English and German and photos of the DLI/VarioFlash.

As always, should you wish to speak to us about this or any other topic related to machine vision, please call us or email us.