Abstract
This research assesses optical measurement methods used to characterise the transmission haze in correlation with its visual perception. Seven silica-filled amorphous polymer test samples from a developed sample set were selected for this purpose. The optical properties of these polymers were examined using commercial haze meters, along with alternative measuring techniques such as BTDF and luminance camera measurements. The BYK commercial instrument used an integrating sphere to measure the scattered light through the samples, whereas the Rhopoint commercial instrument used an image-based technique to analyse contrast loss through the samples. For the alternative measurements, a Near Field Goniophotometer was used to conduct BTDF measurements at different angles and evaluate possible haze changes for different exit port aperture dimensions. Also, luminance images were acquired and a post-processing image method was used. This enabled assessing the loss of contrast caused by the samples and replicating the approach of the Rhopoint instrument. Following, the different optical methods were analysed and compared. Multiple psychophysical tests presented under different assessment conditions were performed to collect the subjective data and establish visual scales using the Maximum Likelihood Difference Scaling approach. In fact, test samples were backlit through a contrast pattern with three distinct predefined air gap sizes (0mm, 4mm, and 8mm) between the test sample and the contrast pattern. Finally, the results show a clear correlation between the visual and optical haze scales. The samples presented with a 4 mm air gap appear to have the best correlation and to be an optimal configuration to assess haze.
