CIE Illuminant Technology

Yujileds® achieved using only one single LED to accurately simulate CIE illuminant for the first time in the world.

With the iteration of LED technology, especially the technological updating of Yujileds® phosphors. As a leader in LED spectroscopy engineering, we successfully simulated and commercialized CIE illuminators using a single LED for the first time in the world. Traditional light sources, such as fluorescent tubes, have not been able to achieve accurate simulation at the spectral level on simulating CIE illuminants, but Yujileds has successfully achieved accurate simulation by using our precise control of the LED spectrum.

CIE series product

The design of using only one single LED offers unbeatable advantages

Before we use a single LED to simulate CIE illuminant, multiple LEDs were used on the market. However, the single-LED design offers unbeatable advantages.

The lighting emitting surface is smaller.

There are differences in the reflective position between different LEDs, which brings some challenges to optical design, and the illumination uniformity is difficult to meet international standards, such as ISO 3664:2009, in some special scenarios.

The design of the circuit is easier.

Compared to the semiconductor red and deep red LEDs which are typically at 1.7V – 2.1V, when mixing with the 3V blue or green LEDs and the 3.5V violet or UVA LEDs, the electrical circuit design has to be organized carefully and more components have to be involved with more complexities. Yujileds® CIE series product uses a single LED to achieve the spectrum of the above LED combinations, making it much easier to design circuits.

Normal CIE illuminant design
Yujileds CIE illuminant design

Simulating CIE illuminant with multiple LEDs requires enough area to arrange different LED.

Yujileds® CIE illuminant products use only one single LED design. It enables CIE illuminant simulations in a small area.

Yujileds® CIE Illuminant Technology: Accurate Simulation of CIE Illuminant with Only Single LED.

Spectral accuracy index (SAI)

At present, most of the spectrum simulation products on the market are still in the stage of qualitative description of the degree of accuracy. There is a lack of a quantitative method for calculating spectral accuracy on the market. When Yujileds® developed the CIE illuminant series, we used the Spectral Accuracy Index (SAI) to describe simulation accuracy and control product quality. This ensures that CIE illuminant has accurate parameters from R&D to production.

To calculate the spectral accuracy index, we need to use two spectral power distributions, one of the products and the other of reference. The formula is shown as follows:

Spectrum accuracy index


C = normalized measured spectrum

Ref = normalized reference spectrum

Max = maximum wavelength

Min = minimum wavelength

CIE standard illuminant A simulation

CIE Illuminant A, often referred to as standard illuminant A, is a reference light source designed by the International Commission on Illumination (CIE) to represent the spectral characteristics of incandescent lamps. It closely resembles the warm, yellowish light emitted by traditional household light bulbs. This illuminant has a smooth spectral distribution across visible wavelengths and is widely used in various applications, including color measurement, photography, and lighting design, to simulate the lighting conditions commonly encountered in everyday environments. Because incandescent lamps have almost unchanged spectral morphology after preheating, incandescent lamps representing CIE standard illuminant A are also commonly used in light source modules of high-precision instruments and equipment.

CIE A simulation

Yujileds® product simulates the spectrum of CIE standard illuminant A perfectly in the visible wavelengths (380nm – 780nm). The Spectral Accuracy Index (SAI) is up to 96. Usually, the SAI of normal LEDs is only 30-35. Therefore, it can perfectly replace incandescent lamps in any scene without worrying about any changes caused by the absence of traditional LEDs due to spectral loss. In addition, compared to traditional incandescent lamps, its spectrum is already in a stable state when directly lit. Therefore, using this product in the instrument will save the time of waiting for the spectrum of the incandescent lamp to stabilize.

CIE standard illuminant D50 simulation

CIE Illuminant D50 is a standardized reference light source developed by the International Commission on Illumination (CIE) to represent average daylight conditions at a color temperature of approximately 5000K. It is commonly used as a benchmark for color-related applications, such as color matching, quality control, and color reproduction in industries like graphic arts, printing, and photography. As a fundamental component in color science, CIE Illuminant D50 plays a crucial role in ensuring consistent and reliable color communication across different media and visual contexts. Unlike CIE illuminant A, it is the sun’s rays at a special moment, influenced by weather, date, and time. Therefore, an artificial light source that stably simulates the D50 is necessary for related industries.

CIE D50 simulation

In the visible wavelengths (380nm – 780nm), Yujileds® product simulates the spectrum of CIE standard illuminant D50 perfectly. The Spectral Accuracy Index (SAI) is up to 90. In contrast, the Spectral Accuracy Index (SAI) of fluorescent tubes currently used to simulate D50 now is only about 60.

CIE standard illuminant D65 simulation

This product simulates the spectrum of CIE standard illuminant D65 in visible wavelengths (380nm – 780nm). CIE D65 closely simulates midday daylight. This makes it also a useful tool in color science like CIE standard illuminant D50. The typical Spectral Accuracy Index (SAI) is 85 from 380nm to 780nm, much higher than normal Leds (about 60).

CIE D65 simulation

CIE illuminant E simulation

Unlike other illuminants that are based on real or typical light sources, CIE illuminant E represents a perfectly uniform light source that emits equal energy at all wavelengths. Because of this property, no artificial light source could simulate illuminant E before. Yujileds® realizes the simulation of illuminant E from 450nm to 780nm through the combination of chip and phosphor.

CIE E simulation

Since the energy of illuminant E is similar in any band. It will simplify the design of light source modules for various precision instruments, and it opens up more possibilities for signal processing of subsequent test results.

CIE Illuminants: Elevate Accuracy in Color Quality Control and Colorimetry.

CIE illuminants find widespread applications in areas such as printing, photography, graphic design, material science, colorimetry, and color management. They are indispensable for accurate color reproduction, color measurement, and ensuring consistent color appearance across different media and devices.

CIE illuminant in industry

In the printing industry, CIE illuminants are essential for color matching and quality control. D50 is commonly used as the reference illuminant for color proofing and printing on commercial offset presses.


Photographers and graphic designers also rely on CIE illuminants to calibrate and profile their displays and cameras for accurate color representation. By using the appropriate illuminant in calibration, they can ensure that the colors they capture or display on their devices match real-world colors.


In product design and material science, CIE illuminants are used to evaluate the color properties of materials under different lighting conditions. This helps to ensure that materials and products appear consistent and reliable under various illuminants, such as in different lighting environments or when viewed from different angles.


Additionally, CIE illuminants are also used in colorimetry, a field that quantitatively measures color. Colorimeters and spectrophotometers, which measure color values, rely on CIE illuminants to define the reference standard against which color measurements are made.


CIE illuminants are particularly important in color management systems, which aim to maintain consistent color appearance across different devices and media. By using the same illuminant as a reference for color reproduction and measurement, color consistency can be achieved across different devices, such as monitors, printers, and scanners.


Moreover, CIE illuminants are used in color-matching algorithms to calculate color differences between samples. The CIE XYZ color space, which is based on the CIE illuminants, is commonly used for color difference calculations, allowing for accurate color comparison and analysis.