Compact Measurement of the Optical Power in High-Power LED Using a Light-Absorbent Thermal Sensor

Abstract

LED (Light-Emitting Diode) presents advantages such as luminescence, reliability, durability compared with conventional lighting. It has been widely applied for life, healthcare, smart farm, industry, and lighting from indoor to the automotive headlamp. However, the LED is vulnerable to thermal damage originated from the high junction temperature, especially in high power applications. Hence, it requires precise qualification on the optical power and the junction temperature from the pilot line to secure reliability. In this study, the photo-thermal sensor is proposed by employing a sheet-type thermocouple composed of photo-absorbent metal film and thermocouple. This sensor aims low-cost qualification in pilot line for high-power luminous devices and optical monitoring of costly luminaire such as automobile LED headlamp. The sensor is designed to detect the increased temperature response of LED hot spots from the transferred thermal power and absorbed optical power. The temperature response of each sheet-type thermocouple is utilized as a signal output of the absorbed optical power and hot spot temperature based on the introduced sensor equation. The proposed thermal sensor is evaluated by comparing the experiment with the measured reference value from the integrating sphere and the attached thermocouple at a junction. The experiment result reveals 3% of the maximum error for the optical power of 645 mW.

Compensation of environmental parameters for optical detection of chemical oxygen demand

“…As shown in figure 1 and table 1, the device is composed of two main parts: light source emission chamber 1 and signal detection circuit 5 . Among them, light source emission chamber mainly has light source drive circuit 3 to control UV-LED light source 2 , and signal detection chamber 5 mainly uses signal detection circuit 6 to process the signals on silicon photodiode detectors 4 .…”

“…COD is an important indicator in water environment protection and marine hydrological monitoring, so the accurate measurement of COD is well worth investigating. Since the water quality detector is in seawater for a long time, the change of ambient temperature affects the optical power of the LED light source and the dark current of the silicon photodiode in the miniature water quality detector [2][3][4][5]. At the same time, the output signal of the detector is disturbed by the atmospheric noise in the lightning weather [6][7][8].…”

Modelling and Thermographic Measurements of LED Optical Power

“…Heat transfer analysis can support the investigations of optical phenomena. In the literature, there are numerous thermal analyses of LED structures based on different modelling approaches, such as 3D-FEM (finite element method), analytical conjugate analyses, and compact simplified models [ 4 , 9 , 10 , 11 , 12 , 13 ]. In this research, a heat transfer analysis using compact 3D-FEM modelling was performed to validate the obtained experimental results.…”