Reliably detect minute defects in solar cells flat panel displays and similar products
11 megapixel high-resolution camera and sophisticated vision software ensure solar cell inspection with utmost precision
Flovel develops, manufactures, and markets high-resolution cameras for industrial applications. The company also has developed inspection systems making optimum use of the advantages of area sensors and high pixel count. Systems from Flovel are widely used for various applications in the industry. The company boasts particular expertise in the area of solar cell inspection, enabling its customers to implement reliable high speed, high-precision inspection during manufacture.
Synergy of camera technology and advanced image processing creates a new paradigm
Flovel has made a name for itself by developing CCD cameras and other digital cameras for industrial applications, as well as offering inspection and analysis systems based on these products. From the outset, the company has focused on high resolution type cameras using area sensors.
Cognex is cooperating with Flovel on the technology level, and Cognex expertise is being applied to the company's development projects. The first product that led to the cooperation between the two companies was a character recognition system making use of the In-Sight® vision system from Cognex. Flovel decided to rely on Cognex know-how in this difficult field. Subsequently, it was agreed to expand the cooperation to encompass other aspects of image processing technology, an area that is rapidly growing in importance. New products buoyed by the synergy of advanced technological know-how are already on the horizon.
Using high-resolution cameras to inspect a wide area with high precision requires that image data from the measurement are processed at a fast rate with high accuracy. This is where Cognex technology is a perfect fit, helping to bring high-performance products from the drawing board into reality.
A clear lead over competitors in the solar cell inspection field, thanks to outstanding camera resolution
Flovel has been focusing on developing cameras based on area sensors mainly for two reasons: the mechanics can be kept simple, and there are no dimensional tolerances caused by movement errors of a line sensor. By utilizing the advantages of area sensors over line sensors and by providing outstanding resolution, Flovel was able to offer systems for solar cell inspection earlier than any of its competitors.
The inspection of solar cells requires accurate detection of a wide range of conditions, including external cracks and chipping, as well as breaks, shorts, and displacement of the microscopic line patterns. The need to maintain high yields imposes severe restrictions on the time available for inspection. The inspection system from Flovel is geared to fully meet these requirements. It employs the 11 megapixel camera ADK-1100B and implements advanced image processing through the CVL™(Cognex Vision Library) SDK (Software Developer’s Kit) from Cognex, resulting in outstanding performance.
Among the many image processing applications on the market, Cognex vision software was selected because it provides the best match for the high resolution of the camera. Flovel also develops image processing software in-house, but in terms of positioning accuracy and processing speed, the Cognex product was judged to be superior. What's more, it also facilitates camera connection, making it a winner for this demanding application.
Reliable and fast detection of defects on the order of several tens of microns in a single pass
Flovel began to offer solar cell inspection capability in 2001 as an extension of an inspection system for screen printed circuit patterns. A configuration designed with Cognex vision software was introduced in 2004.
Detection items during inspection of screen printed patterns include displacement, line breaks, chipping, shorts, halation, line width errors, foreign particles, and hops. If complex patterns are checked using a camera with low pixel resolution, image acquisition has to be divided into several steps, with the need to switch tasks. The high-resolution camera from Flovel, on the other hand, is able to capture even complex patterns in a single pass, greatly simplifying work piece transport requirements. This advantage, combined with the high processing speed of the Cognex vision tools, enables the system to complete an inspection in a much shorter timeframe than competing products.
To obtain increased conversion efficiency of light into electrical energy, solar cells require circuit patterns with very fine line widths, which are susceptible to breaks. The lines in the pattern on a solar cell measuring 160 by 170 millimeters are only 100 micron wide. This means that defects as small as 70 micron must be detected in order to identify a line break or other problems. The high-resolution camera from Flovel, paired with advanced Cognex vision software makes it possible to accomplish this task in a single pass, at high speed and with high reliability.
Technological development that anticipates the inspection needs of the future
Another advantage of the Flovel high-resolution inspection system is the fact that adjustment and maintenance requirements after installation are very simple. In systems based on low-resolution products, multiple cameras have to be used which involves the need for repeated adjustment steps for each camera. With a single high-resolution camera, initial costs may be somewhat higher, but in the long run, maintenance and operation costs are lower, ultimately leading to costs savings. The inspection process is also simplified, since a single processing operation will suffice.
For solar cell inspection, the Flovel system is configured with the 11 megapixel camera ADK-1100B as standard, but most setups use the even higher resolution 44 megapixel camera AKZ-4400BV. Compared to the inspection products of other manufacturers where 5 megapixel cameras are still the norm, the superior capabilities of the Flovel system are evident.
For cases where tact time considerations make near-instantaneous shooting desirable, Flovel has developed the 16 megapixel single-chip camera ADK-1600B. However, a recent trend in the inspection of products such as solar cells is toward using various wavelength ranges and performing multiple inspection steps with different color and gradation settings in order to detect even very slight aberrations. Flovel is moving to develop systems with even finer gradation capabilities for deep-level inspections.
According to the company, inspection needs are also growing in the flat panel display sector. Here the requirements for wide-angle and high-accuracy inspection are even more demanding than for solar cells. For this type of application, the 100 megapixel camera AKZ-M1 is used as standard equipment.
The market for solar cells is highly promising, with higher energy conversion efficiency and quality being major factors. This means that inspection technology will become even more important in the future. Being prepared to cover the complex and diversifying needs of the industry therefore is the key to success.
About Flovel Co., Ltd.
Established February 1975
Head office: Tachihi Building No.3 Hall, 6-1, Sakae-cho, Tachikawa-shi, Tokyo 190-0003, JAPAN
Capitalization: 10 million yen
Fields of activity: Development, manufacture, and marketing of industrial-use CCD cameras, digital cameras, and various kinds of inspection systems