Topic report Swept source OCT

Presentation on theme: "Topic report Swept source OCT"— Presentation transcript:

1 Topic report Swept source OCT
Student : Yen-Chun Liang Advisor : Sheng-Lung Huang

2 Outline Introduction Swept source Commercial OCT

3 Introduction

4 Introduction Time-domain OCT Fourier-domain OCT
-improve the detection sensitivity -higher scan speeds -800nm (Spectrometer + CCD array) -1300nm(swept light source )(CCD are expensive) SD-OCT參考端的反射鏡是不動的，因為SD-OCT不需要掃瞄機制來改變參考端與樣品端的光程差以取得樣品軸向深度的訊號 TD-OCT則需要有掃瞄機制 SD_OCT的偵測端是使用silicon-based 的CCD偵測器,但光源波長須限制在1000nm以下 若要掃皮膚則需要光源約1300nm，此時偵測端使用的是GaAS CCD ,不過此類型的CCD價格昂貴 因此如果需要掃皮膚 則會使用 SS-OCT

5 SD-OCT & SS-OCT SS_OCT 與 SD_OCT 主要不同處有兩個地方，第一個在光源的不同,(swept source laser) 光源波長會隨時間變化 第二個在接收段偵測器的不同

6 Swept source

7 Swept source Fourier domain mode locking Laser(FDML)
Sampled grating distributed bragg reflector Laser (SG-DBR)

8 FDML

9 axial resolution of 25 μm Each tomogram line was acquired within 5 μs. The cross-section consisting of 14,000 A-scans was collected within 70 ms (14,000 × 5 μs)

10 FDML FFP-TF(Micron optic) Fiber delay line:2km FSR:230nm
bandwidth~0.12nm Fiber delay line:2km

11 FDML centered at 1300 nm with 135 nm maximum scanning range
average output power of 6 mW About 70% of light propagating in the cavity is coupled out and delivered to two fiber Michelson interferometers The second one is used to generate a reference fringe signal necessary for time to optical frequency remapping

12 Integrated swept source SG-DBR

13 SG-DBR smaller cavity length than fiber-optic ring lasers
Wavelength sweep from nm nm 100k Hz Small size(3mm chip) Low cost , low power

14 SG-DBR Gain section : Phase section :
Wavelength is controlled by three currents that are applied to the back mirror, front mirror, phase sections Gain section : provides the required amplification for optical oscillation Phase section : provides fine adjustments to the effective spacing between the mirrors SOA: provides boosts the output power from the laser

15 SG-DBR

16 Commercial OCT

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