Spectrophotometer: Applications and Measurement Considerations

A spectrophotometer is an instrument used to measure the reflected spectral power and light characteristics of objects to determine their standard color values. However, measurement results can vary due to differences in color difference calculation methods and light source selection. Therefore, it is crucial to carefully select appropriate color difference formulas and light sources when using a spectrophotometer.

A spectrophotometer is typically used to measure color characteristics and reflectance of objects, providing various numerical values to describe the color and color difference of objects.

Here are the values that a spectrophotometer can generally measure:

 • Tristimulus Values: Measures the reflected light intensity of objects at different wavelengths, calculating the RGB tristimulus values perceived by the human eye.
 • Chromaticity Coordinates: Computes chromaticity coordinates based on measured tristimulus values, often represented as xyY or Lab coordinates. These coordinates describe color tone, brightness (xyY), and include lightness (L), red-green (a), and yellow-blue (b) components (Lab).
 • L, a, b Color Indices: L value indicates brightness, a value denotes red-green, and b value represents yellow-blue in the Lab color space, quantifying color characteristics accurately.
 • Color Difference: Measures color differences between samples, typically represented by ΔE (Delta E), reflecting the overall color difference between two colors. Additional values such as ΔL, Δa, Δb indicate brightness, red-green, and yellow-blue differences, aiding in assessing color similarity or variance.

These measurements and analyses assist in determining standard color, evaluating color differences, and adjusting color consistency during production processes. When using a spectrophotometer, it is essential to select appropriate measurement parameters and color spaces based on specific application needs to ensure accurate and reliable color measurements.

Components of a Spectrophotometer:

 • Light Source: Utilizes standardized light sources like incandescent lamps, xenon lamps, or LEDs to illuminate the object under test, with stability and spectral characteristics affecting measurement results.
 • Integrating Sphere: A spherical reflection cavity with highly reflective inner walls uniformly mixes and diffuses light reflected or transmitted from the sample, ensuring uniform light distribution, minimizing light source effects, and providing a stable measurement environment.
 • Sensor: Captures light reflected or transmitted by the sample and converts it into electrical signals. Common sensor types include photodiodes or photodiode arrays detecting spectral information across different wavelength ranges.
 • Detector: Receives electrical signals from the sensor and converts them into digital signals for computer or data processing unit analysis.
• Measurement/Observation Modes: Spectrophotometers are classified into “0/45 degrees” and “d/8 degrees” based on measurement/observation modes: “0/45 Degrees” measures surface reflectance with light incident at 0 degrees and detected at 45 degrees. “d/8 Degrees” measures transmittance and reflectance with diffuse light incidence and detection angles of 8 degrees.
 • Spectral Analysis: Spectrophotometers analyze parameters and spectral curves across different bands, typically ranging from 380nm to 740nm, covering most of the visible spectrum. Different instrument models may have varying band ranges and resolutions.

The spectrophotometer plays a crucial role in both industrial and scientific fields, primarily used for measuring color differences between standard and test samples, providing color difference values and chromaticity values for analyzing and controlling color deviation issues to ensure product quality stability and consistency. In addition to these primary applications, the spectrophotometer has the following key uses:

• Color Matching: Spectrophotometers adjust product color matching by measuring color difference values, allowing for the precise adjustment of color intensity to match design requirements and ensure color consistency across products.
• Color Analysis: By analyzing sample chromaticity values, spectrophotometers provide detailed information about sample color attributes such as brightness, hue, and saturation, helping users understand and compare different sample color characteristics effectively.
• Whiteness and Yellowness Testing: Spectrophotometers measure whiteness and yellowness values of samples, assessing color purity and brightness, which is particularly important in industries like paper, coatings, plastics, and other color-critical applications.
• Color Quality Control: Spectrophotometers enable precise measurement and comparison of sample chromaticity and color difference values, assisting businesses in achieving color consistency control, promptly identifying and resolving color deviation issues to enhance product quality and market

DSCD-920_Desktop Spectroradiometer

Color Difference Assessment for Plastic Products:

• Linking Raw Materials and Production Processes: The color difference of plastic products is closely related to the quality of raw materials and production processes. Spectrophotometers help detect and quantify the impact of different raw material batches or production process variations on product color. This assists production personnel in adjusting raw material ratios and process parameters to minimize color deviation issues.
• Enabling Data-driven Analysis: Spectrophotometers quantify color parameters of plastic products, such as brightness (L), red-green value (a), and yellow-blue value (b) in the Lab color space, generating data that allows for comparison of color differences among different batches or production conditions.
• Ease of Use and High Precision: Spectrophotometers offer straightforward operation and high precision, facilitating rapid and accurate measurement of color differences in plastic products. Comparing color difference values between samples helps ensure color consistency and stability across products.
• Automatic Calibration and Practicality: Modern spectrophotometers often feature automatic calibration, ensuring measurement accuracy and stability. These instruments are highly practical, capable of stable operation in industrial production environments, helping businesses improve efficiency and reduce production costs.
• Enhancing Product Quality and Cost Reduction: Timely and precise measurement and analysis of color differences in plastic products using spectrophotometers assist businesses in enhancing product quality, reducing scrap rates caused by color deviations, lowering production costs, and enhancing competitiveness and market image.

Textile Industry Color Measurement Applications and Considerations:

• Dye Strength Measurement: Using spectrophotometers, standard dye stored in a database can be compared with newly purchased dye. By measuring the color characteristics of both, the percentage of dye strength of the newly purchased dye compared to the standard dye can be determined. This data is used to adjust production formulas to ensure dyeing quality meets requirements.
• Determining Product or Sample Suitability: Spectrophotometers can quickly and accurately determine whether produced products or samples meet design or customer-specified color standards. This rapid assessment helps businesses adjust production processes promptly to ensure product quality.
• Assessing Color Difference, Fade Resistance, Staining Resistance, Yellowing, Whiteness, and Brightness of Fabrics: Spectrophotometers can evaluate various aspects of color and quality in fabrics, including measuring color differences between fabrics, assessing fade and stain resistance, and measuring yellowing, whiteness, and brightness indicators. Compared to human observation, spectrophotometers provide more accurate and objective measurement results, particularly sensitive and reliable for detecting minor differences.
• Enhancing Production Efficiency and Quality Control: Through the application of spectrophotometers, businesses can achieve precise monitoring and control of dyes and product quality, promptly identifying and resolving production process issues, improving production efficiency, reducing waste rates, ensuring product quality stability, and enhancing competitiveness.

Considerations:

• Thin and Sparse Samples: If samples are too thin or sparse, layering multiple times until the measurement value stabilizes and remains unchanged is recommended. Avoid overly fragile samples to ensure measurement stability and accuracy.
• Small Sample Size: If samples are too small for direct measurement, consider using colored cloth as a backing or creating a black frame to secure the sample for measurement. A small hole slightly smaller than the sample size in the center of the frame allows for testing after calibration, ensuring measurement accuracy.
• Pile or Carpet Fabrics: For fabrics like pile or carpet with raised fibers, comb the fibers neatly and place optical glass on the fabric surface for measurement after calibration. If the entire fabric consists of the same type and batch of raw materials, testing can be conducted on the reverse side of the fabric.
• Yarn Color Measurement: For yarn samples, wrap the yarn neatly around a specialized yarn board before measurement. Pay attention to maintaining moderate tension during yarn winding and ensure consistent tension to avoid measurement errors and ensure accurate yarn color measurement.