From brightness and color temperature to circadian rhythm control, a healthy lighting environment requires a more sophisticated control system.

Adjustable brightness and color temperature are now standard features in lighting products. However, when lighting begins to prioritize “health,” the evaluation criteria extend beyond simply providing clear and comfortable vision.

Light provides a temporal signal for the circadian rhythm, influencing wakefulness, melatonin secretion, and sleep. However, brightness and color temperature merely describe a light fixture’s output; they cannot fully reflect the circadian stimuli actually received by the human eye: even with the same illuminance and correlated color temperature, the circadian effects may differ due to variations in the light spectrum.

Furthermore, light distribution, the direction of the line of sight, and natural light entering the room all influence the lighting environment. Therefore, “healthy light” cannot be defined solely by brightness and color temperature; it requires more precise adjustments to artificial lighting in conjunction with the actual lighting environment.

Metrics such as glare, color rendering, and flicker form the foundation for evaluating the visual quality of a lighting environment. To further determine whether a lighting environment is healthy, one must also consider its impact on human circadian rhythms.

The national standard GB/T 46119—2025, “Dose of Non-Visual Biological Effects of Light on the Human Eye,” co-drafted by MiJi Technology, classifies such effects—which do not depend on the formation of visual images but can trigger physiological responses—under the category of “non-visual biological effects of light on the human eye.”

Excerpt from GB/T 46119—2025

This standard incorporates the melanin response to daylight (D65) equivalent illuminance (m-EDI), circadian stimulation value (CS), and daily cumulative light biological effect (DCLA) into a quantification system, and provides recommended values for circadian-stabilizing lighting during different time periods.

In real-life situations, the impact of light on circadian rhythms varies depending on age, field of view, and the photoclimate of the region. This standard also incorporates these factors into its quantification system to adjust certain indicators and recommended values.

Therefore, circadian lighting must not only ensure visual comfort during daily use but also adjust artificial light in accordance with these conditions, so that the light actually received by the human eye better meets the health requirements of the current environment.

Using a single set of fixed brightness and color temperature parameters throughout the day makes it difficult to meet the needs of different times, environments, and usage scenarios.

For healthy adults with regular sleep-wake patterns, more abundant light is typically needed during daytime work and activities, while light stimulation should be minimized as bedtime approaches and during sleep. Time curves can thus provide a basic rhythm for light output throughout the day.

In 2022, a research team published recommendations in PLOS Biology:

The above values cannot be directly applied to all populations; children, the elderly, and shift workers still require separate consideration.

A time curve can only describe the general rhythm of a day; it cannot reflect the actual lighting conditions in a room at any given moment, nor can it be adjusted for different populations. Light output must be adjusted according to the time of day, the target audience, and specific visual needs.

The amount of artificial lighting required to compensate for natural light varies between cloudy and sunny days in the same room. Whether the curtains are open or closed also affects the amount of natural light entering the room.

Even under identical time and environmental conditions, activities such as working, reading, watching TV, and preparing for sleep carry different weights in terms of visual comfort and circadian rhythm goals.

While “cool in the morning, warm in the evening” can serve as an intuitive interactive cue, it is insufficient on its own to make these judgments.

This information ultimately translates into changes in brightness, spectrum, and output patterns:

• Time determines the baseline luminance and spectral change curves.

• Natural light, shading conditions, and occupancy determine how much artificial light is needed at any given moment.

• The scene selected by the user—or the scene requirements inferred based on usage habits—determines how the current output balances visual comfort with rhythmic goals.

When natural light or usage conditions change, the product uses sensors to detect environmental changes. AI algorithms then dynamically adjust the brightness, color temperature, and spectrum of the artificial light based on temporal and spatial conditions as well as usage requirements.

During the adjustment process, the output light must change smoothly to avoid noticeable brightness jumps, color shifts, or flickering.

At the same time, installation location, light distribution, and natural light also affect the light actually received by the human eye; therefore, it is necessary to verify whether the effect meets expectations at typical usage locations.

In this way, circadian lighting can provide appropriate and stable light output tailored to the needs of different environments and scenarios, creating a natural, comfortable, and healthy lighting environment for users.