Micron-level precise inspection of the cover glass

As technology advances, the demand for high-quality, defect-free cover glass for applications such as smartphones, tablets, and large-screen displays has skyrocketed. However, achieving micron-level precise inspection of these cover glasses is fraught with challenges.

When it comes to inspecting defects on large-size cover glass, the lighting conditions often pose a significant hurdle. In some cases, the illumination is too dim. This makes it extremely difficult to clearly discern the minute defects that may be present on the glass surface. Defects such as scratches, pits, or inclusions, which could potentially affect the functionality and aesthetic appeal of the end-product, remain hidden in the shadows. The human eye, even when aided by basic magnifying tools, struggles to identify these imperfections due to the lack of sufficient light.

On the other hand, overexposure is an equally vexing problem. When the lighting is too intense, the image captured of the cover glass becomes overexposed. Instead of a clear view of the glass surface with its possible defects, all that is presented is a blank expanse of white. This overexposure completely washes out any details, rendering the inspection process futile. The over-saturation of light masks the very features that need to be inspected, making it a major obstacle in the quality control process. Adding to these difficulties is the issue of reflection.

Glass, by its very nature, is a highly reflective material. When light hits the surface of the cover glass during inspection, the reflected light can create glare. This glare can be so intense that it conceals the defects. The reflected light acts as a veil, obscuring the true condition of the glass surface. Even if the lighting is adjusted to a seemingly optimal level, the reflection can still pose a problem, making it nearly impossible to achieve the micron-level precise inspection required for high-quality cover glass production. In the context of modern manufacturing, where the standards for cover glass quality are extremely high, the inability to accurately detect micron-level defects can have far-reaching consequences. Defective cover glass can lead to issues such as reduced touch-screen sensitivity, uneven display quality, or even potential breakage during the device’s lifespan. This not only affects the user experience but also incurs significant costs for manufacturers in terms of product recalls, customer dissatisfaction, and loss of brand reputation.

If you find yourself grappling with these challenges in cover glass inspection, Basson’s bi-telecentric lens offers a promising solution. This innovative optical device is designed with cutting-edge technology to overcome the difficulties associated with cover glass inspection. Basson’s bi-telecentric lens is engineered to provide high contrast imaging. This means that when it comes to capturing the image of the cover glass surface, it can clearly distinguish between the defects and the surrounding area. The high contrast ensures that the defects stand out prominently, allowing for easy identification. Whether it is a hair-thin scratch or a minuscule pit, the lens can capture it with remarkable clarity, without the issue of overexposure.

In traditional lenses, overexposure often occurs when trying to capture details on a reflective surface like glass. The light bounces off the surface in an uncontrolled manner, leading to an over-saturated image. However, Basson’s bi-telecentric lens is designed to manage the incoming light effectively. It has a unique optical system that regulates the amount of light reaching the sensor, ensuring that the image is neither too dark nor overexposed. This precise control over light enables the lens to clearly capture the defects on the glass surface, presenting a detailed and accurate view of the glass’s condition. One of the most remarkable features of Basson’s bi-telecentric lens is its ability to achieve micron-level accuracy.

When inspecting the cover glass, the lens can precisely capture the details of the defects at an extremely high level of precision. The edges of the defects are sharp and clear, with very few transition pixels. This high-resolution imaging is crucial for micron-level inspection. In the manufacturing process, even the slightest deviation from the perfect surface can be a sign of a defective product. With Basson lens, these minute details can be accurately detected, allowing manufacturers to make informed decisions about the quality of the cover glass. The telecentric design of the lens is another key factor in its effectiveness. Telecentric lenses are designed to have a parallel beam of light entering and exiting the lens. This design ensures that the magnification of the object remains constant regardless of its position along the optical axis.

In the context of cover glass inspection, this means that the size and shape of the defects are accurately represented, regardless of whether they are located at the center or the edges of the glass. This consistent magnification is essential for accurate defect measurement and analysis. Furthermore, the lens is equipped with an excellent stray light elimination design. Stray light, which is light that enters the lens at an unwanted angle, can cause a decrease in image contrast and clarity. In the case of cover glass inspection, stray light can be particularly problematic as it can add to the reflection-related issues. Basson’s bi-telecentric lens is designed to minimize the impact of stray light. By effectively eliminating stray light, the lens can provide a cleaner, more contrast-rich image of the cover glass surface. This makes it easier to identify and analyze the defects, even in the presence of ambient light or other sources of potential interference.

In practical applications, the use of Basson’s bi-telecentric lens has been proven to significantly improve the efficiency and accuracy of cover glass inspection. In a manufacturing plant that produces large-size cover glass for high-end smartphones, the adoption of this lens led to a notable reduction in the number of defective products reaching the market. The inspection team was able to detect even the most minute defects, such as sub-micron scratches that were previously undetectable. This not only improved the overall quality of the products but also reduced the costs associated with rework and product recalls.

In a research and development environment, the lens has also been invaluable. Scientists and engineers are constantly exploring new materials and manufacturing processes for cover glass. Basson’s bi-telecentric lens allows them to closely monitor the surface quality of experimental samples, providing detailed feedback on the effectiveness of new techniques. This has accelerated the pace of innovation in the cover glass industry, leading to the development of more durable, scratch-resistant, and optically superior cover glass. The lens is also adaptable to different inspection setups. Whether it is used in a manual inspection process, where an operator visually inspects the glass through a microscope equipped with the bi-telecentric lens, or in an automated inspection system, where the lens is integrated with a high-speed camera and image-processing software, it performs exceptionally well.

In automated systems, the lens can quickly capture high-resolution images of the cover glass, which are then analyzed by the software to detect and classify defects. The combination of the lens’s high-quality imaging and the advanced image-processing algorithms enables rapid and accurate inspection of large volumes of cover glass. In terms of maintenance, Basson’s bi-telecentric lens is designed to be robust and easy to care for. The lens is made of high-quality materials that are resistant to scratches and environmental factors.

Regular cleaning and calibration, following the manufacturer’s guidelines, ensure that the lens continues to perform at its optimal level over an extended period. This reliability and low maintenance requirement make it an attractive option for manufacturers who are looking for a long-term solution to their cover glass inspection needs. In conclusion, the challenges associated with micron-level precise inspection of large-size cover glass are significant. However, Basson’s bi-telecentric lens offers a comprehensive solution. Its high-contrast imaging, ability to avoid overexposure, micron-level accuracy, telecentric design, and excellent stray light elimination make it an ideal choice for cover glass inspection. Whether in manufacturing, research, or quality control, this lens has the potential to revolutionize the way cover glass is inspected, leading to higher-quality products and more efficient production processes.

Basson focuses on machine vision products used for precision measurement and defect detection.

Basson not only provides high-precision bi-telecentric lens systems, telecentric lens systems, telecentric light sources, coaxial illuminations and optical lenses, but also offers customized services.

With products designed in Germany, business planned in the UK and products made in China, Basson is able to provide superior products to customers through its global team. Currently, Basson is in preparation of production and assembly of products in Japan.

Dr. Liu Lu, acting as CTO of Basson, is a PhD degree holder of Oxford University.

Production and testing instruments include optical vacuum coating machines manufactured by Satis in Switzerland and Leybold in Germany, a laser interferometer from Zygo in the US, a spectrophotometer from PerkinElmer in the US, a spherometer from Hofbauer Optik in Germany, a centering instrument from Kyoritsu Electric in Japan, a NC grinding device made by Kojima Engineering in Japan and an automatic centering machine made by Shonan in Japan.