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Non-destructive inspection methods for LEDs using real-time displaying Optical Coherence Tomography.

Cho NH, Jung U, Kim S, Kim J - Sensors (Basel) (2012)

Bottom Line: The SD-OCT and SS-OCT images were compared with each other in the same sample to study their advantages.In addition, the volume of the fluorophore space was calculated from the OCT images.We expect this method can improve the inspection efficacy over traditional inspection methods such as Charged Coupled Device (CCD) camera or X-ray instruments.

View Article: PubMed Central - PubMed

Affiliation: School of Electrical Engineering and Computer Science, Kyungpook National University, 1370, Sankyuk-dong, Buk-gu, Daegu 702-701, Korea. nhcho@knu.ac.kr

ABSTRACT
In this study, we report the applicability of two different Optical Coherence Tomography (OCT) technologies for inspecting Light Emitting Diode (LED) structures. Sectional images of a LED were captured using a Spectral Domain OCT (SD-OCT) system and a Swept Source OCT (SS-OCT) system. Their center wavelengths are 850 and 1,310 nm, respectively. We acquired cross-sectional two dimensional (2D) images of a normal LED and extracted sectional profiles to inspect possible wire disconnection that may be present in the LED manufacturing process. The SD-OCT and SS-OCT images were compared with each other in the same sample to study their advantages. The distribution of fluorescence material was observed more clearly with the SD-OCT of 850 nm wavelength, whereas the status of wire connection was clearer in the SS-OCT images with 1,310 nm wavelength. In addition, the volume of the fluorophore space was calculated from the OCT images. This is the first report that a nondestructive optical imaging modality such as OCT can be applied to finding screen defects in LED. We expect this method can improve the inspection efficacy over traditional inspection methods such as Charged Coupled Device (CCD) camera or X-ray instruments.

No MeSH data available.


Related in: MedlinePlus

1,310 nm SS-OCT system. (a) Schematic diagram of the SS-OCT system; (b) Photograph of 1,310 nm SS-OCT system and sample arm optic setup.
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f3-sensors-12-10395: 1,310 nm SS-OCT system. (a) Schematic diagram of the SS-OCT system; (b) Photograph of 1,310 nm SS-OCT system and sample arm optic setup.

Mentions: The schematic diagram of the developed SS-OCT system is shown in Figure 3(a). The center wavelength (λC) of the light source (Santec HSL-2000, Komaki, Japan) is 1,310 nm, while the Full Width Half Maximum (FWHM) is 110 nm, and the maximum line scan speed is 20 kHz. We used a balanced detector (Thorlabs PDB110C) as a light detection tool whose effective bandwidth is from 800 to 1,650 nm, and the electronic bandwidth is 100 MHz. A PCT-5122 digitizer (NI) which has two analog input channels, one trigger channel at a maximum sampling rate of 100 MHz, was used for signal processing. A PCI-6221 DAQ board (NI) with a maximum sampling rate of 833,000 samples per second was used for driving the galvanometer scanning mirror (Thorlabs GVS002). The axial and lateral resolution is 4 μm and 58 μm, respectively. The lateral scanning range is flexibly set to cover the sample area.


Non-destructive inspection methods for LEDs using real-time displaying Optical Coherence Tomography.

Cho NH, Jung U, Kim S, Kim J - Sensors (Basel) (2012)

1,310 nm SS-OCT system. (a) Schematic diagram of the SS-OCT system; (b) Photograph of 1,310 nm SS-OCT system and sample arm optic setup.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472834&req=5

f3-sensors-12-10395: 1,310 nm SS-OCT system. (a) Schematic diagram of the SS-OCT system; (b) Photograph of 1,310 nm SS-OCT system and sample arm optic setup.
Mentions: The schematic diagram of the developed SS-OCT system is shown in Figure 3(a). The center wavelength (λC) of the light source (Santec HSL-2000, Komaki, Japan) is 1,310 nm, while the Full Width Half Maximum (FWHM) is 110 nm, and the maximum line scan speed is 20 kHz. We used a balanced detector (Thorlabs PDB110C) as a light detection tool whose effective bandwidth is from 800 to 1,650 nm, and the electronic bandwidth is 100 MHz. A PCT-5122 digitizer (NI) which has two analog input channels, one trigger channel at a maximum sampling rate of 100 MHz, was used for signal processing. A PCI-6221 DAQ board (NI) with a maximum sampling rate of 833,000 samples per second was used for driving the galvanometer scanning mirror (Thorlabs GVS002). The axial and lateral resolution is 4 μm and 58 μm, respectively. The lateral scanning range is flexibly set to cover the sample area.

Bottom Line: The SD-OCT and SS-OCT images were compared with each other in the same sample to study their advantages.In addition, the volume of the fluorophore space was calculated from the OCT images.We expect this method can improve the inspection efficacy over traditional inspection methods such as Charged Coupled Device (CCD) camera or X-ray instruments.

View Article: PubMed Central - PubMed

Affiliation: School of Electrical Engineering and Computer Science, Kyungpook National University, 1370, Sankyuk-dong, Buk-gu, Daegu 702-701, Korea. nhcho@knu.ac.kr

ABSTRACT
In this study, we report the applicability of two different Optical Coherence Tomography (OCT) technologies for inspecting Light Emitting Diode (LED) structures. Sectional images of a LED were captured using a Spectral Domain OCT (SD-OCT) system and a Swept Source OCT (SS-OCT) system. Their center wavelengths are 850 and 1,310 nm, respectively. We acquired cross-sectional two dimensional (2D) images of a normal LED and extracted sectional profiles to inspect possible wire disconnection that may be present in the LED manufacturing process. The SD-OCT and SS-OCT images were compared with each other in the same sample to study their advantages. The distribution of fluorescence material was observed more clearly with the SD-OCT of 850 nm wavelength, whereas the status of wire connection was clearer in the SS-OCT images with 1,310 nm wavelength. In addition, the volume of the fluorophore space was calculated from the OCT images. This is the first report that a nondestructive optical imaging modality such as OCT can be applied to finding screen defects in LED. We expect this method can improve the inspection efficacy over traditional inspection methods such as Charged Coupled Device (CCD) camera or X-ray instruments.

No MeSH data available.


Related in: MedlinePlus