C2R Colibri 5 Series, User Manual

Page: 38 / 168

Colibri serie 5 : User’s guide
© 2000-2008 C2R Technologie, Sarl. All rights reserved.
38 38
Rev. C
Thermal Considerations
Care must be taken when designing the Image Engine into any system. Internal heating of the
Image Engine can occur in high duty cycle scanning applications in several ways. The high
visibility aimer dissipates a significant amount of power as heat. The illumination and aiming LEDs
also release heat, and are a major contributor to thermal increases in high use or in presentation
mode.
An increase in temperature around an Image Engine can cause noise levels on the imager,
degrading image quality. The thermal rise can also affect the laser diode. In a continuous
scanning or high use environment, the Image Engine temperature can rise 15° to 20°C. Under
high ambient temperature conditions, the laser diode is at risk of thermal breakdown and possible
failure. The image quality and decode performance will also degrade
The Power Control PWM can be used to reduce the effect of the illumination LEDs on thermal
rise, however, this also reduces the intensity of the illumination. Reducing the intensity of the
illumination reduces total power used but can also reduce the depth of field in low light
environments.
Centering
Use Centering to narrow the imager‟s field of view to make sure the imager reads only those bar
codes intended by the user. For instance, if multiple codes are placed closely together, centering
will insure that only the desired codes are read. (Centering can be used in conjunction with Aimer
Delay, page 36, for the most error-free operation in applications where multiple codes are spaced
closely together. Using the Aimer Delay and Centering features, the imager can emulate the
operation of older systems, such as linear laser bar code imagers.)
In the example below, the gray area is the full imager field of view and the white area is the
centering window. Bar Code 1 will not be read, while Bar Code 2 will be.