LCD Production Quality Control
AOI Alignment System

Project
Due to the continuous development and popularity of consumer electronics, such as LCD TVs, LCD monitors and notebook PCs, global demand for TFT-LCD (thin film transistor liquid crystal display panels) keeps increasing. A major TFT-LCD manufacturer in Taiwan with 7.5-generation (1950 x 2250 mm) LCD production needed to have a full range of new inspection systems.
 

Automated defect inspection is absolutely necessary to ensure the quality of large, mass-produced LCD panels. The manufacturer’s goal is to sell 100% “no failure” screens, therefore, a fast and highly accurate visual inspection of each finished assembly is essential. Before and after each step in the complete manufacturing process, an alignment is necessary to ensure the glass is positioned accurately. Advantech’s ARK-5260 fanless embedded IPC, with two add-on PCI cards, was chosen as the key component for an Automated Optical Inspection (AOI) alignment system.

Requirements
‧Excellent computing power with Intel® AtomTM D510 1.66GHz CPU to handle image data
‧All-in-one set with both image grabbing and LED lighting control capability
‧Four independent image grab channels with BNC/HIROSE connectors
‧Four independent channels for 5 - 50V LED light with software control
‧Embedded software supports most of the popular image process libraries, such as Matrox Imaging Library (MIL), eVision,HALCON
‧Windows XP Embedded ready with MUI and EWF functions
‧Extremely compact, sealed construction with fanless operation

System
The glass defect inspection equipment is for 7.5G glass substrates, capable of inspecting LCD glass plates up to 1950 x 2250 mm. The equipment performs a variety of critical tasks: image grabbing and processing, defect location, statistical computation, as well as data analysis and review. Before and after the defect inspection processing, the alignment procedure is conducted to ensure the TFT-LCD to be inspected is precisely positioned on the system. This procedure is fundamental and critical, as incorrect position of the glass on the system may lead to serious inspection errors. The AOI alignment systems are implemented at many stages throughout the manufacturing process.
 

Advantech’s ARK-5260 operates with two added PCI cards. The first is a 4-channel PCI-bus Image Grabber Card with BNC or Hirose interface, which is connected to a CCD camera. The CCD camera captures the image of the cross mark on the glass, and calculates the variance from the absolute X and Y coordinates. According to the variance, it further moves the glass to an ideal position through PLC. The second PCI card is a 4-channel isolated analog output card. With this card, this system features 4-channel LED light software control. The system connects to an LED light through a standard LED connector interface. It could enable 5 – 50V wide-range LED light which illuminates the image to amplify features that need to be inspected. Also, the ARK-5260 connects to an encryption key via printer port. This ensures the security of the API. The printer port further provides easy access for a wide range of image process libraries, as most image process libraries in the world are available through printer port dongles.

Conclusion
Advantech’s ARK-5260 high performance rate was an exact match for the Taiwan LCD maker’s requirements. Featuring two PCI slots for application expansion and system integration, the ARK-5260 also comes with five USB 2.0 and four standard serial port interfaces. It supports up to 2 GB of DDR SDRAM. Offering great flexibility in space critical environments, the ARK-5260 is ideal for embedded system applications required by machine automation, industrial plants, and cabinet integration. Its rubberized anti-vibration card-holder for system cards, combined with an anti-vibration HDD-bay, ensure maximum reliability; plus, the ARK’s simple, modularized, user-friendly design is ready for quick installation, as well as easy expansion and maintenance.

Suggested Application Implementation

ARK-5260  Fanless Embedded Box IPC with Intel® Atom™ D510 processor and PCIe/ 2 x PCI Expansion slots

ARK-3420  High Performance Solution with PCIe Expansion and Dual SATA HDDs for Image Processing and Surveillance Applications