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Laser or Camera - Comparison Print

As the families of inspection technologies overlap in a number of dimensions, it is most useful to compare extremes. Telecentric laser systems and camera systems are compared below for coated or uncoated high quality optical film and glass.
Laser System Advantages:
 
bullet Simple packaging allows generation of multiple video channels (bright field, dark field, transmission, reflection, etc.) with a single laser scanner.
bullet System easily configured for bright and dark field video channels, in transmission and/or reflection.
bullet Modular design provides simple upgrades in the future (additional transmission/reflection channels, coating uniformity, polarity shift, distortion, etc.)
bullet Detection is consistent across the line and independent of line speed.
bullet Operation in ambient light, no shrouding.
bullet High power, coherent lighting.
bullet Wavelength can be selected to maximize defect signature
bullet Relatively simple installation and alignment procedure.

Laser System Disadvantages:

bullet Limited detection capability for opaque, multi-colored films.  Laser systems are color-blind; a white light source is preferable.
bullet High base cost, relative to camera systems.  Usually not cost-effective if the task is predominately bright field or if a four-camera system can satisfy the detection requirements.

Camera System Advantages:

bullet Lower entry cost.  Excellent for simple/moderately difficult bright field applications.
bullet Intuitive.  Easier to understand.

Camera System Disadvantages:

bullet Number of cameras required.
bullet Bank of cameras required for each optical channel (two banks of cameras required for bright field and dark field).
bullet Difficulty in packaging many cameras on the production line
bullet Alignment of cameras relative to each other.
bullet Alignment of cameras relative to the light source, sheet/film and dark field masking
bullet Relatively low powered, incoherent light source.  Shrouding of the (dark field) cameras against ambient light will be required.
bullet High power consumption and greater operating costs. Light source and camera-to-camera inconsistencies can result in varying detection across the line.  This inconsistency becomes more dramatic as the number of array pixels increases (from 2048 to 8196).
bullet Optical upgrades are very difficult.  Additional bank(s) of cameras and possibly additional light sources (if a reflection channel is required) would be necessary.
 
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