Utilizing Haze Meters and turbidity Meters for Assessing the Quality of Transparent and Translucent Materials

Haze meters is also known as turbidity meters, indicates the degree to which transparent or translucent materials are not clear. Is the cloudy or hazy appearance in or on a material due to light scattering.

Expressed as a percentage of the ratio of the scattered luminous flux to the luminous flux transmitted through the material. Usually only the scattered light flux deviated from the direction of incident light by more than 2.5 degrees is used to calculate the haze. The distance creates beauty, and the haze is the same. The same piece of glass has different haze, and the display effect is also different.

working principle:
When a parallel beam of light is incident on a medium (such as transparent plastic), due to the inhomogeneity of the optical properties of the material; surface defects, inhomogeneity of internal organization, existence of bubbles and impurities, etc., the beam will change direction (diffusion and deflection), The part of the random light generated is called scattered light.

Internationally, it is stipulated that the ratio of the scattered luminous flux that passes through the sample and deviates from the direction of the incident light to the transmitted luminous flux is expressed as a percentage, which is the so-called haze. A sample with a high haze will give people a more blurred feeling.

Light will also be lost when passing through the sample, that is, the transmitted luminous flux passing through the sample is always smaller than the incident luminous flux irradiated on the sample. The ratio between the two is expressed as a percentage, which is internationally defined as light transmittance. The reason for the decrease of light transmittance is the reflection of light by the two surfaces of the sample and the absorption of light energy of the full wavelength or part of the wavelength of the incident light by the sample.

But pay attention: haze and light transmittance are two concepts. Materials with high haze may not have very low light transmittance. If such material is used for window glass, the room will appear bright during the day, but it is also concealed; if it is used for car windshield, it is obviously required that both are good, so as to observe clearly.

In the process of testing the haze and light transmittance of the sample, it is necessary to measure the incident light flux (T1), the transmitted light flux (T2), the scattered light flux of the instrument (T3), and the scattered light flux of the sample (T4). Then the calculation method of light transmittance and haze value is as follows:

Light transmittance: Tt=T2/T1×100%

Haze: H=T4/Tt×100%

During the test, when there is no incident light, the received luminous flux is 0, when there is no sample, all the incident light is transmitted, and the received luminous flux is 100, which is T1. At this time, use the optical trap to absorb the parallel light, and the accepted luminous flux is the scattered luminous flux T3 of the instrument;

Then place the sample, the luminous flux received by the instrument is T2, if the parallel light is absorbed by the light trap at this time, the luminous flux received by the instrument is the sum of the scattered luminous flux of the sample and the instrument T4. The light transmittance and haze value can be calculated according to the measured values of T1, T2, T3 and T4.

1. Calculation principle of haze
A beam of parallel light from a standard “C” light source is irradiated vertically on a transparent or translucent film, sheet, or plate. Due to the scattering caused by the interior and surface of the material, all the light passing through the object makes part of the parallel light deviate from the incident direction by more than 2.5° The percentage of the ratio of the scattered luminous flux Td to the luminous flux T2 passing through the material, that is:

2. Calculation principle of transmittance
Transmittance, expressed as a percentage of the ratio of the luminous flux transmitted through the material to the incident luminous flux. It usually refers to the ratio of the luminous flux T2 passing through the material to the incident luminous flux T1 irradiating the transparent material, namely:

If the light passing through the glass is likened to soldiers breaking through the barrier, the first thousands of troops are called the incident luminous flux T1, all the way through thorns and thorns, there are casualties, and the remaining ones that successfully enter the barrier are called T2. Among the soldiers who entered the customs, in addition to following the army to move forward, some may flee to all sides due to the impact of the battle. We call deserters who deviate 2.5° from the direction the army is traveling as Td.

3. The relationship between haze and transmittance
Haze and transmittance are two very important optical performance indicators of transparent materials. In packaging applications, hazy films may reduce consumers’ quality perception, such as packaging products that look blurry.

Generally speaking, materials with high light transmittance have low haze value, and vice versa, but not entirely. Some materials have high light transmittance but high haze value, such as frosted glass. Therefore, light transmittance and haze value are two independent indicators.

Haze Meter – Turbidity Meter HM-100 conforms to both ASTM and ISO international standards ASTM D 1003, ISO 13468, ISO 14782, JIS K 7361 and JIS K 7136. It already includes a CNAS Calibrate Certificate.  It is no need to do warm-up, after instrument is calibrated, it can be used. And measurement time is only 1.5 seconds.

HM-100 Haze Meter/Turbidity Meter

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