Source: Link Testing Instruments Co.,Ltd.
In the quality control of glass products, transparent plastics, and optical materials, the uniformity of internal stress distribution directly impacts mechanical strength and operational safety. Residual stress resulting from improper annealing can cause glass containers to spontaneously shatter during filling or transport and can compromise the imaging quality of optical components. Accurately and efficiently quantifying this critical parameter remains a key focus for many manufacturers and testing agencies.
The LTYLY-03S polariscopic stress meter from Link Testing is designed around two detection principles—quantitative compensation and qualitative color comparison—offering a measurement solution for laboratories and production lines that balances data precision with operational efficiency. In quantitative mode, the instrument employs a high-precision absolute angle encoder, achieving an optical path difference measurement accuracy of within 2.0 nanometers and a resolution of 0.1 nanometers. This configuration eliminates the need for manual calculations based on traditional visual scale readings; instead, operators can read optical path difference values directly from the color touchscreen, thereby reducing data errors caused by visual estimation or calculation mistakes. For rapid screening scenarios, the qualitative mode utilizes the interference color sequence produced by a full-wave plate, enabling operators to quickly assess the scope and approximate level of stress distribution—making it particularly suitable for the preliminary screening of mass-produced items on the production line.
In terms of practical application, the instrument's adaptable design resolves the challenges associated with testing samples of varying specifications. It features a polarization field diameter of 150 mm and a test space that is continuously adjustable within a 280 mm range, accommodating samples ranging from pharmaceutical glass ampoules and infusion bottles to mobile phone screens and optical windows. For irregularly shaped glassware or dark-colored samples with low light transmission, operators can manually adjust the field-of-view brightness to suit the laboratory environment; this minimizes interference from ambient light or the sample's base color when observing interference colors, thereby enhancing consistency in determining the compensation endpoint. Additionally, the instrument includes a built-in micro-printer for immediate output of test results, while features such as historical data retrieval and multi-level user access management facilitate traceability within the laboratory's quality management system and enable effective control over equipment usage.
Regarding industry applicability, the LTYLY-03S is designed and manufactured in accordance with multiple standards, notably the YBB standard system, which sets specific requirements for internal stress testing in pharmaceutical glass containers. Taking low-borosilicate glass ampoules as an example, the standard stipulates that the optical path difference resulting from maximum residual stress after annealing must not exceed 40 nm/mm. The specific testing procedure follows YBB00162003-2015 ("Method for Determination of Internal Stress"), requiring a field-edge brightness of at least 120 cd/m² and a polarization field of no less than 85 mm; furthermore, a 565 nm full-wave plate and a quarter-wave plate must be inserted between the polarizer and the analyzer. For colorless samples, the quarter-wave plate is first inserted into the field of view and zeroed; the operator observes the dark cross appearing at the bottom of the sample (viewed from the opening) and rotates the analyzer until the blue-gray hue is replaced by brown, then records the rotation angle to calculate the optical path difference. For colored samples or those with low light transmission, an averaging method may be employed to determine the endpoint. Parameters such as the polarization field diameter and field-of-view brightness of the LTYLY-03S meet or even exceed the aforementioned standards. The instrument can be directly integrated into existing testing workflows—including pharmaceutical packaging inspection, quality control for daily-use glassware, standards compliance verification by third-party testing agencies, and optical material performance testing at research institutions—ensuring data comparability across different devices.
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