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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

Microscope and OCT images of LED array (a) The microscope image of LEDs; (b) The OCT image of LEDs; (c) the inner frame view of LED.
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f9-sensors-12-10395: Microscope and OCT images of LED array (a) The microscope image of LEDs; (b) The OCT image of LEDs; (c) the inner frame view of LED.

Mentions: To examine the amount of fluorophore covering the chip, OCT scans of 12 LEDs are performed and compared with the microscopic image. Importantly, the volume of the fluorophore area is calculated because it is crucial to constant illumination and should be carefully monitored in manufacturing process. Figure 9(a) is the microscopic view of the sample containing 12 LEDs with the width of 13.35 mm and the height of 19.97 mm. Each LED size is 3 mm in width and 5.44 mm in height, respectively. Figure 9(b) is the reconstructed 3D OCT image of the entire sample that is taken in a burst scan without any rearrangement during the scan. The space of the fluorophore part was extracted from the single entire OCT image and the volume was calculated. Figure 9(c) graphically shows the inner part of a LED indicating the fluorophore space. This inner part is also extracted from the obtained OCT image. The unit in Figure 9(c) is in pixel and each pixel size in x, y, and z direction is 4 μm, 58.2 μm, and 58.2 μm, respectively.


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

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

Microscope and OCT images of LED array (a) The microscope image of LEDs; (b) The OCT image of LEDs; (c) the inner frame view of LED.
© Copyright Policy
Related In: Results  -  Collection

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

f9-sensors-12-10395: Microscope and OCT images of LED array (a) The microscope image of LEDs; (b) The OCT image of LEDs; (c) the inner frame view of LED.
Mentions: To examine the amount of fluorophore covering the chip, OCT scans of 12 LEDs are performed and compared with the microscopic image. Importantly, the volume of the fluorophore area is calculated because it is crucial to constant illumination and should be carefully monitored in manufacturing process. Figure 9(a) is the microscopic view of the sample containing 12 LEDs with the width of 13.35 mm and the height of 19.97 mm. Each LED size is 3 mm in width and 5.44 mm in height, respectively. Figure 9(b) is the reconstructed 3D OCT image of the entire sample that is taken in a burst scan without any rearrangement during the scan. The space of the fluorophore part was extracted from the single entire OCT image and the volume was calculated. Figure 9(c) graphically shows the inner part of a LED indicating the fluorophore space. This inner part is also extracted from the obtained OCT image. The unit in Figure 9(c) is in pixel and each pixel size in x, y, and z direction is 4 μm, 58.2 μm, and 58.2 μm, respectively.

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