working principle

The whiteness and chromaticity meter is based on the principle of optical diffuse reflection, and achieves accurate measurement of surface color and whiteness of objects by simulating standard light sources (such as D65 illuminating bodies) and specified observation conditions (such as d/o illumination geometry conditions). The core process includes:

Light source emission: Semiconductor light sources (such as LEDs or tungsten halogen lamps) emit light of a specific wavelength (such as blue light 457nm), which is then passed through a condenser lens and a color filter group to form a uniform test beam.

Integral sphere diffuse reflection: After entering the integral sphere, light is reflected multiple times on the inner wall to form a uniform diffuse light field, which illuminates the surface of the sample at the testing port.

Signal acquisition: The spectrum reflected by the sample is received and converted into an electrical signal by a silicon photovoltaic cell after passing through a condenser, light bar, and color filter group; Meanwhile, another silicon photovoltaic cell collects the substrate signal inside the integrating sphere as a reference.

Data processing: After amplification and mixing of two electrical signals, the whiteness values (such as R457, W10) and chromaticity parameters (such as Lab * values) are calculated by a microcontroller or embedded system, and the results are displayed digitally or printed out.

key metrics

Whiteness measurement accuracy:

R457 (ISO whiteness): Based on the diffuse reflectance factor of blue light, it reflects the whiteness of the sample at a wavelength of 457nm with an accuracy of ± 0.1.

Ganz whiteness (W10): calculated based on chromaticity coordinates (x, y), in accordance with the CIE1964 standard, suitable for polymer materials.

Chromaticity parameters:

Lab * value: L represents brightness, a (red green axis) and b (yellow blue axis) represent hue and saturation, and a color difference Δ Eab ≤ 0.5 is considered indistinguishable by the human eye.

Yellowth Index (YI): Quantifying the degree of sample yellowing, suitable for fields such as plastics and paper.

Repeatability and stability:

Repeatability ≤ 0.1 (deviation of multiple measurements of the same sample), stability error ≤ 0.1 (drift within 30 minutes).

Optical geometry conditions:

Using d/o (diffuse illumination/vertical observation) geometric conditions, with a diffuse sphere diameter of ≥ 120mm and a test hole diameter of 15-30mm, to eliminate specular reflection interference.

Compliant with standards:

Meets more than 40 international and national standards such as GB/T7973 and ISO2470, covering industries such as papermaking, ceramics, textiles, plastics, etc.