## 1 Introduction
The research results show that proper fin structures give the best heat dissipation performance for LEDs; the high heat transfer coefficient and copper fins have a positive effect on the \(T_{\rm j}\) of the LED. [PERSON] et al. [22] used a flexible woven heat sink (FWHS) of copper belts to conduct an experimental study on the heat dissipation performance of LED headlamps under the ambient temperature between 30 \({}^{\circ}\)C and 80 \({}^{\circ}\)C. The results of the study showed that the overall temperature of the headlamp increased almost linearly with the input power and the ambient temperature. The cooling effect of FWHS was enhanced with the wind speed, and the optimal wind speed was about 2 m/s. At ambient temperature below 50 \({}^{\circ}\)C, the total thermal resistance was stably maintained at 4.42 \({}^{\circ}\)C/W. However, the total thermal resistance rapidly increased when the ambient temperature exceeded 50 \({}^{\circ}\)C, achieving a total thermal resistance of 5.61 \({}^{\circ}\)C/W at 80 \({}^{\circ}\)C.  
[PERSON] et al. [23] developed a three-dimensional vapor chamber (3D VC) device to solve the heat dissipation problem of LED automotive headlamps. This 3D VC included a flattened heat pipe and a circular vapor chamber. The research results showed that both-sides heating had better thermal performance than one-side heating when the total heating load on the 3D VC was the same. The 3D VC had good temperature uniformity and had the lowest thermal resistance of 0.125 \({}^{\circ}\)C/W at a 50 W heating load. [PERSON] et al. [24] used a heat-pipe-based cooling system with piezo fans to improve the heat dissipation of automotive headlamps. The heat pipe had a heat capacity 2-3 times higher than die-cast heat sinks, and the weight was reduced by 50%. The piezo fan blew directly to the LED substrate and generated air convection in the headlamp lampshade. This system improved the heat transfer coefficient of the air and reduced the temperature of the measurement point on the LED substrate by 7.6 \({}^{\circ}\)C and increased the heat transfer coefficient of the air in the headlamp enclosure by three times compared with natural convection (5 W/m\({}^{2}\) K increased to 15 W/m\({}^{2}\) K). The higher \(T_{\rm j}\) of the LED reduced the lifetime of the LED lamp and its illuminance, changed color rendering [25, 26], deteriorated the chip package, melted the solder joint, and damaged the chip [27, 28]. Therefore, the main purpose of the methods mentioned above for improving heat-dissipation of automotive LED lamps is to reduce \(T_{\rm j}\) to increase the efficiency and lifetime of the LED lamps. However, the ambient temperature directly affects heat dissipation performance, and thus the \(T_{\text{j}}\) of the LEDs in lamps, and also affects the power consumption of the LED lamps. Compared with the research on LED chips, the literature discussing the automotive LED lamp is less. In the references of this paper, only Refs. [13; 19; 22] have proposed the test method for a whole automotive LED lamp. The method of Ref. [13] is to put an automotive LED lamp on the incubator, let it be in the environment with an ambient temperature of 30 \({}^{\circ}\)C-80 \({}^{\circ}\)C, and test whether the proposed heat dissipation design can effectively reduce the LED junction temperature. Similarly, Ref. [22] tests the thermal resistance of different heat dissipation designs and the corresponding LED junction temperature. In Ref. [19], an automotive LED lamp is placed at a room temperature of 25 \({}^{\circ}\)C. A fixed power of 25 W is input to test the LED junction temperature corresponding to different heat dissipation designs. In addition, the spectrum and angular distribution of light output by the automotive LED lamp are also tested. This study proposed a simple measurement system and method that can simultaneously measure the temperature, power consumption, and optical properties of an automotive LED lamp at different ambient temperatures.