A solar simulator is a device that can precisely reproduce the characteristics of sunlight in a laboratory environment. Its core objective is to simulate key parameters such as the spectral distribution, irradiance (light intensity), and spatial uniformity of the sun through artificial light sources and optical control technology, providing stable and controllable "artificial sunlight" for fields such as aerospace, photovoltaics, agriculture, and scientific research. Its working principle can be decomposed into four core links: light source excitation, spectral regulation, light intensity control, and homogenization treatment, as detailed below:
I. Light Source Excitation: Simulating the "Energy source" of Solar Radiation
The foundation of a solar simulator is an artificial light source, which needs to generate initial light radiation through specific light-emitting devices. Its performance directly determines the basic energy level of the simulation. The common types and principles of light sources are as follows:
Xenon lamps (the most mainstream) : They utilize the continuous spectrum produced by xenon gas during high-voltage arc discharge, covering the ultraviolet (UV), visible light (VIS) to near-infrared (NIR) bands, which are highly consistent with the natural continuity of the solar spectrum. Xenon lamps have high luminous intensity and a wide spectral range, making them the core light source for simulating full-spectrum sunlight.
LED array: Composed of LED chips of different bands (such as ultraviolet leds, red/green/blue visible light leds, near-infrared leds), it achieves segmented regulation of the solar spectrum by precisely controlling the luminous intensity of each chip. LED light sources have the advantages of long lifespan, low energy consumption and fast response speed, making them suitable for scenarios that require dynamic spectral adjustment (such as agricultural light formula research).
Halogen tungsten lamps: They generate heat and emit light by electrified tungsten wires, supplementing the radiation energy in the infrared band. They are often used in conjunction with xenon lamps to enhance the spectral matching degree in the near-infrared region.
The excitation process of the light source requires power supply through a stable power system to avoid unstable light intensity caused by voltage fluctuations. It is usually paired with a high-precision constant current/voltage power supply to ensure the stability of the energy output by the light source.
Ii. Spectral Regulation: The "Core Technology" for Matching Solar Spectra
The solar spectrum varies in different application scenarios (for instance, ground sunlight has an AM1.5G spectrum and space sunlight has an AM0 spectrum). The solar simulator needs to adjust the original spectrum of the light source to the target spectrum through optical filtering and correction technology. The core means include:
Filter combination: By adding specific band filters (such as ultraviolet cut-off filters, infrared enhancement filters, neutral density filters) to the optical path, bands that do not match the target spectrum in the light source are eliminated, or the energy of specific bands is enhanced. For instance, when simulating the AM0 spectrum of the space environment, the infrared band absorbed by the atmosphere needs to be removed, and the spectral deviation of the xenon lamp should be corrected through a filter.
Spectral fine-tuning module For high-precision scenarios (such as photovoltaic cell efficiency testing), the device is equipped with an adjustable spectral compensation component. By controlling the insertion depth or Angle of the filter through the motor, it can achieve fine regulation of specific bands (such as the 600-700nm visible light region). Ensure that the spectral matching degree (SM) meets international standards (such as the requirement of IEC 60904-9 that SM≥0.75).
LED spectrum synthesis: For LED light source simulators, by independently controlling the currents of different leds such as red, green, blue, and infrared, the energy proportion of each band can be directly adjusted to achieve digital matching of the target spectrum, which is far more flexible than traditional filtering methods.
Iii. Light Intensity Control: The "Energy Valve" for Precisely Adjusting Irradiance
The intensity of sunlight varies with time and the environment (such as sunny days, cloudy days, and altitude differences). The simulator needs to achieve precise control of irradiance through a photomulterometer system (units: W/m² or mW/cm²). Common techniques include:
Variable diaphragm/attenuator: By mechanically changing the light-transmitting area in the optical path or inserting neutral attenuators with different transmittance, coarse adjustment of light intensity and range switching can be achieved (such as adjusting from 100W/m² to 1000W/m²).
Closed-loop control of light source power: Combined with high-precision irradiance sensors (such as silicon photovoltaic cells, thermocouple detectors), the output light intensity is monitored in real time. The power supply of the light source (such as the current of the xenon lamp, the driving voltage of the LED) is adjusted through the feedback circuit to ensure the stability of the light intensity (such as ±0.5%/ hour), meeting the long-term experimental requirements (such as material aging tests).
Pulsed light emphasis section: Some simulators support pulsed mode. By controlling the luminous time duty cycle of the light source (such as 10%-100%), high-intensity pulsed light can be output in a short period of time to simulate extreme light scenarios such as solar flares (such as radiation resistance tests of aerospace materials).
Iv. Homogenization Treatment: "Spatial Calibration" to Ensure Light Stability
In practical applications, the tested samples (such as photovoltaic cells and satellite components) need uniform light coverage; otherwise, it will lead to testing errors. The solar simulator achieves spatial uniformity of light through an optical light homogenization system. The core technologies include:
Integrating sphere: A hollow sphere with a high-reflectivity material (such as polytetrafluoroethylene) coated on the inner wall. When the light source is incident from the side, the light is reflected multiple times inside the sphere and forms a uniform surface light source when it exits from the outlet, with a uniformity of ±2% or less. It is widely used in photovoltaic cell efficiency testing.
Lens array/diffuse reflector: By using a micro-lens array to split the light beam into multiple sub-beams and re-superposition them, or by using a diffuse reflector (such as frosted glass, holographic diffuser) to scatter parallel light into uniform diffuse light, it ensures a consistent light intensity distribution on the sample surface (such as uniform light irradiation for agricultural crops).
Precision optical path collimation: By using components such as mirrors and collimating lenses, the scattered light emitted by the light source is calibrated to parallel light, simulating the parallelism of sunlight (especially in the aerospace field, it is necessary to restore the space parallel light irradiation conditions), and the parallelism can be controlled within ±0.5°.
Summary: Multi-system collaboration achieves "Artificial Sunlight"
The working principle of a solar simulator is as follows: the light source excitation provides the energy basis → spectral regulation matches the target spectrum → light intensity control ensures precise energy → homogenization processing guarantees spatial stability. The four systems work in coordination through the electronic control unit (ECU) to ultimately output an artificial lighting environment highly consistent with natural sunlight. Its core value lies in breaking through the uncontrollability of natural light, providing repeatable, adjustable and high-precision lighting conditions for various industries, and promoting innovation throughout the entire process from material research and development to product testing.
For instance, the solar simulator of Saifan Optoelectronics, through the hybrid light source design of "xenon lamp + LED supplementary light", multi-layer filter spectral correction technology, and integrating sphere uniform light system, can achieve multi-spectral switching such as AM0/AM1.5G, with light intensity stability reaching ±0.3% per hour and uniformity ±1.5%. Meet the strict demands of high-end scenarios such as aerospace material aging and photovoltaic efficiency testing.
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