The Haze Meter (also referred to as a transmittance and haze tester) is a sophisticated optical device that measures the visual appearance and optical transmission characteristics of transparent or translucent samples.

Similarly to how a peel tester gauges a sample’s physical performance characteristics, the haze meter evaluates its optical performance characteristics. This instrument finds applications across various sectors, including plastics films, glass production, solar cells, LCD panels, and packaging.

The Two Core Metrics of a Haze Meter: Total Transmittance vs. Haze

Three possibilities occur when light falls on a translucent substance: it either gets reflected, absorbed, or passes through. In a haze meter, the passing light is analyzed using the separation of its two unique scientific properties:

Total Luminous Transmittance:

This is the total light that penetrates the sample divided by the total light that impinges upon it. This test is meant for testing total transparency. An example would be a clear glass window that will have high transmittance, while a tinted one would have low transmittance.

Haze:

The haze value of an optical material is defined as the amount of light that scatters off the transmitted light by more than 2.5 degrees from the direction of the transmitted light. Haze results in loss of contrast and causes objects to look smoky and hazy.

Which industries use Haze Meters?

Industries that use haze meters are-

• Automotive industry for glass manufacturing
• Pet and mineral water bottle manufacturing industries
• Glass panel manufacturing industries
• Packaging material manufacturing industries
• Pharma industries

What materials can be tested using a Haze Meter?

The materials that can be tested using a haze meter are-

• Plastics and polymer films
• Rigid plastic containers
• Display glass
• Solar panel covers
• Beverages
• Chemicals and resins
• Pharma products
• Cosmetic items

How a Haze Meter Works (The Optical Setup)

The hazemeter uses an optical arrangement known as the “Integrating Sphere,” which allows the capture of both direct light and diffused light.

• Light Source: The calibrated lamp (such as the daylight lamp as per CIE Standard Illuminant D65 or A) emits light in the form of a collimated and parallel beam to the test surface.
• Specimen Holder: The specimen strip or sheet is positioned parallel to the entrance port of the integrating sphere.
• Integrating Sphere: An integrating sphere is essentially a spherical chamber with its inner walls coated with a highly reflective, matte white surface, such as barium sulfate.
• Photodetector: An extremely sensitive detector of light measures the amount of light that enters the sphere.
• Light Trap: The light trap, placed right across the entrance port, can be either closed or opened. If it is opened, then all the "straight through" parallel light (less than $2.5^circ$ deviation) gets absorbed by it, enabling the measurement of the scattering light, which is then used for the haze calculation.

Common Industry Standards

To ensure uniformity throughout supply chains around the world, haze meters must adhere to stringent international optical standards:

• ASTM D1003 – Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics. This is one of the most referenced standards on a global scale for films, sheets, and plaques.
• ISO 14782 – Plastics – Determination of haze of transparent materials.
• ISO 13468 – Plastics – Determination of total luminous transmittance of transparent materials.