Common transmittance measurement methods and equipment

1. Spectrometer measurement method

A spectrophotometer is the most accurate and comprehensive tool for measuring transmittance, capable of counting the passage of light wavelength by wavelength.
Its working principle is to separate the mixed light into single wavelength light through a monochromator, which is received by a detector after passing through the sample, and compared with the original light intensity to calculate the transmittance. By continuously scanning different wavelengths, a complete transmittance spectrum curve can be drawn.

2. Sample processing of spectrophotometer

1) For solid materials such as glass and plastic sheets, it is necessary to ensure that the surface is clean and free of scratches, and the sample needs to be placed vertically.

2) For liquid samples such as solutions and oils, specialized quartz colorimetric dishes should be used to prevent the formation of bubbles and distortion of readings.

3) Calibration required before measurement: First, use air or pure solvent as the "blank" sample and set the instrument to 100% transmittance; Then simulate a completely opaque state with a shading board and set it to 0%. After these two calibrations, the instrument establishes an accurate measurement benchmark.

There are various types of spectrophotometers: visible spectrophotometers focus on the visible light range of 400-760 nanometers; The UV visible spectrophotometer extends the measurement range to 200-1000 nanometers and can evaluate the transparency of materials in the ultraviolet region, such as sunscreen glass and optical filters.

3. Haze meter

The haze meter is specifically used to measure the "haze" caused by internal scattering of materials, which refers to the degree of blur in the image formed by light passing through the material. Through a precise integrating sphere optical system, it can accurately separate the total transmitted light into parallel transmitted light and scattered transmitted light. The ratio of total transmitted light to incident light is the transmittance, while the ratio of scattered light to total transmitted light is the haze. Used for scenes where transparency and imaging quality need to be controlled, such as screen protectors and packaging films.