Mask Inspection System for Color TV Picture Tubes
This is an On-line flexible video based system for automated
inspection / measurement of the shadow mask used in television and computer
monitors. The system consists of a vision system, integrated with a positioning
system and user friendly software developed on a windows platform.
Image Processing System
The Shadow Mask Inspection System is used for measuring the slot
width, bridge width and pitches (Horizontal and Vertical) of the apertures
of the Shadow Mask. The system has a video camera positioned on the top
of the Shadow Mask. The Shadow Mask is firmly held in position with the
help of suitable fixtures and the arrangement has X and Y movement.
The video camera captures the image of the shadow mask at the desired
location specified by the user. The image captured by the camera is digitized
using a PC add-on Frame Grabber Card. The captured data is accessible
by the Software. The image is then processed using advanced image processing
algorithms and the result is displayed on the PC. A diffused lighting
arrangement is provided to enhance the quality of the acquired images.
The flexible Vision Software allows the user to select the type
and shape of the mask apertures to be measured/inspected.
In addition, an option to select the gun or screen side of the mask is
provided. User defined inputs such as tolerance limits for each parameter
being measured, region of interest (ROI) for measurement etc., can be
entered for each analysis. The shadow mask is inspected for the following
parameters at different locations on the mask namely slot width, bridge
width, horizontal and vertical pitch of the apertures. The front screen
displays a mimic diagram which represents the mask under inspection. The
expected and measured values of the apertured dimensions are also displayed.
The pass/fail status is indicated on the mimic screen by red/green dots
at the corresponding x-y locations. A provision for displaying the on-line
picture of the mask under inspection, when needed, is provided to manually
calculate the aperture size, pitch and other parameters of the Shadow
The results of each inspection, accepted tolerances and user defined values
are stored in the database for further processing and report generation.
Detailed and summary reports based on batch ID, type of masks selected
and parameters measured are provided. Bar graphs and Histograms are used
to provide detailed SPC reports and analysis. An option to make a hard
copy of the same is also provided.
The primary application of the Vision System is for inspection
of shadow masks used in television and computer monitors. The system can
be used as a quality control tool during the manufacturing of masks. The
modular design of the software system allows a great degree of customization
in relatively short time for other inspection applications involving gauging