CD/DVD manufacturers are finding that today’s customers demand blemish-free discs, picture-perfect disc image quality, and shipments with no mix-ups such as discs with the wrong image or in the wrong packaging.
Automated inspections systems play a crucial role in enabling optical disc manufacturers to meet these expectations. Using a camera to acquire an image and a computer to process the image, these systems determine if an object in the image meets acceptance criteria.
This allows optical disc manufacturers to ensure that:
- Discs have no defects such as warping and surface-related defects resulting from the printing process.
- Discs have the right images on them.
- Images have no color variation.
- Images adhere to original specifications.
- Discs are in the right packaging.
- Discs are correctly oriented in the packaging.
Several types of automated inspection systems—surface inspection, Ident code verification, print inspection, and disc orientation—are being used to achieve the quality control standards necessary to be competitive in today’s market.
Surface Inspection
This system detects defects that appear on the read-side surface. It includes applications such as:
- Detecting birefringence, tilt, and warp across the disc.
- Detecting surface defects such as dents, cuts, and scratches on large surface areas.
- Inspecting the metallization area for pinholes, blemishes, or color variation.
Ident Code Verification
This system reads and verifies the bar code or alphanumeric code etched into the hub on the back of a prerecorded disc. By verifying the Ident code, you can:
- Verify that the correct disc is in place prior to printing a label on it.
- Verify that the correct disc is inserted into the appropriate package.
- Sort discs into categories based on their Ident code.
- Verify readability of printed codes and characters etched into the disc.
Print Inspection
Print inspection involves performing a pixel-by-pixel comparison between a learned good image and running discs. The task is to look for a variation from the expected or ideal image quality. With a single inspection system, defects can be detected in print image quality, surface quality, and other defect types, including the detection of:
- Pinholes, color shifts, ghosting/feathering, missing/excessive ink, and watermarks in print image quality.
- Squeegee marks, scratches/dust, raised print, print thickness variations, and dents/bumps in surface quality.
- CD-R spectral ink, CMYK comparison, center-hub print defects, and metal-area defects.
Disc Orientation
Determination of a disc’s orientation prior to adding value to the disc in printing or packaging. Applications for this system include:
- Detecting disc orientation prior to printing to ensure that special molded or laser-etched features are visible after printing.
- Detecting disc orientation prior to packaging to ensure that the disc is correctly oriented relative to the graphics and packaging.
Conclusion
An automated inspection solution that includes all of these systems—using the most-advanced camera and imaging technology—can not only help optical disc manufacturers survive, it can help them increase output rates, reduce waste costs, and earn customer confidence that leads to repeat business.
Image courtesy of commons.wikimedia.org.
