Advanced Imaging


Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

New Light Shines on Direct Part Mark Identification

Advancements in optical engineering enable handheld imagers to overcome reading challenges for aerospace and military aviation applications
Stationary imager
Stationary imagers can be permanently installed at the appropriate focal distance and angle for optimal lighting to read low-contrast direct part marks.
handheld imager
The handheld imager can be rapidly adjusted to deliver three types of illumination: bright field, dark field and diffused.

By Susan Snyder

To give handheld imagers the same performance as stationary imagers, a new optical solution has been developed that manipulates the lighting produced by a standard handheld and redirects it at the desired angle for reading direct part marks.

Most handheld imagers simulate bright field (or on-axis) illumination. Bright field illumination causes the light to bounce back directly into the imager, prohibiting its ability to see the symbol.

While bright field is effective for reading high-contrast 2-D codes, it is not suitable for reading low-contrast direct part marks. By coupling a specially designed optical attachment to the front end of the handheld imager, the bright field illumination is transformed into the optimal lighting needed to decode the symbols.

The patented optical technology behind the attachment calls upon the total internal reflection principle, which makes fiber optics function as well as creates the reflection off a lake. At small angles, light is not able to cross the boundary between two materials with different indices of refraction. In the case of the reflection on the lake, the two materials are air and water. In the case of the optical technology, it is air and plastic. The case is designed in such a way that the angles of the plastic contain the light and allows it to propagate until it reaches the desired position in front of the imager. Another angle is designed into the technology which allows the light to leave the plastic at the desired position to illuminate the symbol. The solution is unique in that it can transform on-axis illumination into either shallow or diffused illumination.

The advantage to this type of solution is that external light sources are not needed to provide multiple types of illumination, making it suitable for use with handheld imagers. Because it utilizes the light source already designed into the handheld imager, it doesn?t add additional lighting apparatus to the imager or require power supplies. The handheld imager can be rapidly adjusted to deliver three types (bright field, dark field and diffused) of illumination that are specifically designed for reading the most challenging, low-contrast symbols. To provide further ease of use, the optical read angle and focal distance is designed into the optic, so the operator does not have to search for the optimal spot for reading the part. All the operator needs to do is position the imager over the symbol and squeeze the trigger.

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