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Haze meter theory

Update time:2020-03-10 10:38:40 | Clicks:483

What is haze?

Haze is also called turbidity. It indicates the degree of unclearness of transparent or translucent materials. It is the appearance of cloudiness or turbidity caused by light scattering inside or on the surface of the material.

                                                                   

What is transmittance?

It is expressed as a percentage of the ratio of the luminous flux transmitted through the material to the incident luminous flux. Usually refers to the standard light source of a beam of parallel light perpendicular to the film, sheet, plate-shaped transparent or translucent material, the ratio of the luminous flux(T1) transmitted through the material and the incident light flux (T2)to the transparent material

Relationship between transmittance and haze?


Two very important optical performance indicators of transparent materials, such as aerospace plexiglass require light transmittance greater than 90% and haze less than 2%. Generally speaking, materials with high light transmittance have low haze value and vice versa, but not completely.. Some materials, such as ground glass, have high light transmittance and high haze values. So light transmittance and haze are two independent indicators.


Test principle

When testing, when there is no incident light, the received light flux is 0. When there is no sample, all the incident light is transmitted, and the received light flux is 100, which is T1. At this time, the parallel light is absorbed by the light trap, and the received light flux is the scattered light flux T3 of the instrument.

Then place the sample, and the instrument receives the light flux through the sample as T2; At this time, if the parallel light is absorbed by a light trap, the light flux received by the instrument is the sum T4 of the scattered light flux of the sample and the instrument. Based on the measured values of T1, T2, T3, and T4, light transmittance and haze can be calculated

Transmittance:

          Haze value:


Why measure haze and transmittance?

The first is the screen industry. In the screen industry, companies like screen covers, light guide plates, and diffuser plates have very high requirements for these two parameters. Second, the glass industry, whether it is outdoor or indoor, glass products have light transmission performance. The requirements are very high, the haze of the glass needs to be very low, and the transmittance is high; and the film industry is very widely used.


                                          cellphone screen              watch screen



How haze meter working theory?

This is the light path structure diagram of this haze meter. The light source emits parallel light, passes through the sample and enters the integrating sphere. Part of the transmitted light is parallel light and part is scattered light. A photoelectric sensor is installed on the inner wall of the integrating sphere perpendicular to the parallel beam to obtain the light flux signal. The light trap is used to absorb all the incident light when there is no sample in the test port. The light trap is equipped with a shutter, which is coated with the same high reflectivity coating as the integrating sphere wall. The shutter can be opened and closed as required.

Light trap: When measuring the haze, the light trap will open (because the scattered light will be collected to calculate the haze); when measuring the total transmittance, the light trap will be closed; haze meter can be automatically measured, all you have to do is place the sample at the test