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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

Program UI. (a) 840 nm SD-OCT program UI; (b) 1,310 nm SS-OCT program UI.
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f5-sensors-12-10395: Program UI. (a) 840 nm SD-OCT program UI; (b) 1,310 nm SS-OCT program UI.

Mentions: Figure 5 shows the user interface (UI) of the SD and the SS-OCT systems. Figure 5(a) is the UI of SD-OCT and Figure 5(b) is that of SS-OCT. The number “(1)” in the picture represents the system setup part consisting of control panels displaying the current program speed, image saving, background removal, adjusting the brightness and the chroma, driving the galvanometer scanning mirror, and scan mode change. At the spectral information part ((2)), the detailed information after FFT and changing to log scale can be seen. The spectrum information before FFT is shown at the depth profile part ((3)). The OCT image part ((4)) shows the real-time display of a 2D image based on the acquired data. The system speed is 120 frame/s in the SD-OCT system with the image size of 1,024 × 512 pixel, and 20 frame/s in the SS-OCT system (2,500 × 200 image size). The reason for the slower frame rate in the SS-OCT system is due to limitation of the data transfer speed from the digitizer.


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

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

Program UI. (a) 840 nm SD-OCT program UI; (b) 1,310 nm SS-OCT program UI.
© Copyright Policy
Related In: Results  -  Collection

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

f5-sensors-12-10395: Program UI. (a) 840 nm SD-OCT program UI; (b) 1,310 nm SS-OCT program UI.
Mentions: Figure 5 shows the user interface (UI) of the SD and the SS-OCT systems. Figure 5(a) is the UI of SD-OCT and Figure 5(b) is that of SS-OCT. The number “(1)” in the picture represents the system setup part consisting of control panels displaying the current program speed, image saving, background removal, adjusting the brightness and the chroma, driving the galvanometer scanning mirror, and scan mode change. At the spectral information part ((2)), the detailed information after FFT and changing to log scale can be seen. The spectrum information before FFT is shown at the depth profile part ((3)). The OCT image part ((4)) shows the real-time display of a 2D image based on the acquired data. The system speed is 120 frame/s in the SD-OCT system with the image size of 1,024 × 512 pixel, and 20 frame/s in the SS-OCT system (2,500 × 200 image size). The reason for the slower frame rate in the SS-OCT system is due to limitation of the data transfer speed from the digitizer.

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