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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

Circle chip LED. (a) Microscope top view 3D image; (b) 850 nm SD-OCT top view 3D movie 1; (c) 1,310 nm SS-OCT top view 3D movie 2.
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f8-sensors-12-10395: Circle chip LED. (a) Microscope top view 3D image; (b) 850 nm SD-OCT top view 3D movie 1; (c) 1,310 nm SS-OCT top view 3D movie 2.

Mentions: Figure 8 is the experimental result with a transparent chip LED for confirming the status of wire connection. Figure 8(a) is the microscope image of a transparent chip LED with the same equipment and magnification as previously used. Figure 8(b) is the 3D reconstructed animation with SD-OCT (850 nm center-wavelength). With this system, the electric wire presence is observable, but not enough to decide if there is any discontinuity. However, the SS-OCT approach provides better SNR for the wire inspection as shown in the 3D reconstructed animation Figure 8(c). On the contrary, the image of fluorophore beneath the wire is dimmer than the images taken from SD-OCT.


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

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

Circle chip LED. (a) Microscope top view 3D image; (b) 850 nm SD-OCT top view 3D movie 1; (c) 1,310 nm SS-OCT top view 3D movie 2.
© Copyright Policy
Related In: Results  -  Collection

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

f8-sensors-12-10395: Circle chip LED. (a) Microscope top view 3D image; (b) 850 nm SD-OCT top view 3D movie 1; (c) 1,310 nm SS-OCT top view 3D movie 2.
Mentions: Figure 8 is the experimental result with a transparent chip LED for confirming the status of wire connection. Figure 8(a) is the microscope image of a transparent chip LED with the same equipment and magnification as previously used. Figure 8(b) is the 3D reconstructed animation with SD-OCT (850 nm center-wavelength). With this system, the electric wire presence is observable, but not enough to decide if there is any discontinuity. However, the SS-OCT approach provides better SNR for the wire inspection as shown in the 3D reconstructed animation Figure 8(c). On the contrary, the image of fluorophore beneath the wire is dimmer than the images taken from SD-OCT.

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