Abstract
AbstractA versatile imaging‐based method is presented for quantifying the transparency of materials based on “illumination diffusion” (ID), representing scattering‐ and refraction‐induced change in the spatial distribution of transmitted light intensity. Samples are backlit through a graticule mask, with analysis performed by comparative evaluation of graticule images recorded as‐is and viewed through a sample, mimicking visual perception. ID‐haze is quantified as the reduction of contrast, while ID‐sharpness is derived from imaged knife‐edge acuity. Measurements are performed for diverse materials, including clarified polyolefins, silica‐filled amorphous polymers, semicrystalline films, and etched polymer sheets. Comparisons with the respective haze and clarity values obtained using a common ASTM D1003 haze‐meter are made in terms of their quantitative correlation and suitability for applications. In particular, unlike conventional instruments, ID‐based analysis captures the variation of transparency with sample‐to‐object “airgap” distance. Gratifyingly, ID‐haze generally features a one‐to‐one correlation with standard ASTM haze, when determined at a specific distance. The presented method also enables sensitive detection of local defects—differentiating them from large‐area characteristics—and accurately extracts the contribution of luminescence to loss of transparency. ID‐based method therewith offers unique opportunities for application‐ and airgap‐specific transparency analysis, and advanced options for optical process‐ and quality control.
Highlights
A low value of haze is typically desired for packaging optics, as well as ordinary packaging.[1,2,3] It characterizes the materials, allowing the consumer to clearly see and appraise ability of light to pass through a material without substantial a product.[2,3,11] The opposite, i.e., high haze, is often sought scattering, which otherwise obscures the features of objects for applications in optics such as light-management layers
Due to the specific instrument geometry prescribed by the current standard, haze is independent of sample placement along the optical axis—that is, clearly contrary to the common visual observation of improved material transparency when placed in contact with an object
We report an advanced extension of this method for providing a complete quantitative description of in-contact and distance-dependent transparency of materials, and describe the practice and advantages thereof
Summary
(orientation, surface texture from flow instabilities, wear of calenders or molds, etc.) and end-use (contamination, Optical transparency of materials is a key property for a wide abrasion).[1,5,6,7,8,9,10]. Adding to the confusion, selected ASTM D1003 haze-meters measure “clarity” using a non-standardized[19,20,21] definition for light scattered at low angles (generally correlating with the ability to resolve fine object details), according to which the clarity of a material does vary with sample placement. This presents one with difficulties in reconciling haze and clarity into a meaningful measure of transparency that correlates with visual perception. Measurements are performed using a commercial instrument developed by Rhopoint Instruments Ltd. on a wide range of materials—including clarified polyolefins, filled amorphous polymers, and etched polymer sheets—and the results compared throughout with those obtained using a conventional haze-meter
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