Over the past century there has been a dramatic increase in the demand for float glass in many fields of industry.
Usually, 10 to 30% of produced float glass is coated with various coatings for different purposes. As a consequence
quality control of the coatings is one of the most current issues during the process of float glass manufacturing.
In this work we describe a system designed for the online control of reflectivity, transmittance and color coordinates of
the coatings during the glass production process. The working principle of the system is based on the measurement of the
spectral characteristics of reflectivity and transmittance of coatings within the 400-700 nm spectrophotometer spectral
range during the online coating process.
The measurement unit consists of two microspectrometers (one for the measurements of the spectral characteristics of
the reference source, and the other for the measurements of the reflectance spectrum), illumination head (consisting of
one white 1W LED and collimating lenses), stabilized power supply, microprocessor and 18 bits precision ADC. The
use of the reference channel allows us to stabilize the intensity of the incident light up to 10-4 level. The repeatability of
the measurement of reflectivity coefficient in laboratory conditions was in range of ± 0.001. However, in the
measurements in the factory environment, due to the vibration of the glass ribbon on the conveyer, the measurement
reproducibility was about ± 0.005.
Progresses in the optical coatings and optical material fields require an increase in the sensitivity and accuracy of the
optical parameters' measurement methods and systems. In this work we describe a flexible and high-accuracy system for
measuring the main optical characteristics at 632.8 nm wavelength. The system comprises two methods: a laser ratio-metric
measurement method for absolute measurement of the transmittance and the specular reflectance, and an
integrating-sphere method for assessment of the total integrated scattering. The system utilizes an intensity stabilized He-
Ne laser as a light source. Two four-element trap detectors are used: the first for monitoring of laser power, the second
(fixed on a motorized stage) for the measurement of reflectance and transmittance, one after another. A PMT mounted to
the exit port of a 40 cm diameter integrating hemisphere, is used for measuring the total integrated scattering. A series of
measurements with several reference mirrors showed that the system is able to measure the specular reflectance with a
reproducibility of <0.005%, transmittance of 0.005% with a reproducibility <0.005%, and total integrated scattering
about 10 ppm, with a reproducibility of < 5 ppm at 2 sigma. The system allows characterizing of optical components
with diameters between 5 mm and 50 mm.