1. Articles from Shengnan Ai

    1-7 of 7
    1. Feature Of The Week 07/22/2019: Tsinghua University Demonstrates A “Sparse Sampled” Smart CCD Camera for Compressed Sensing Optical Coherence Tomography.

      Feature Of The Week 07/22/2019: Tsinghua University Demonstrates A “Sparse Sampled” Smart CCD Camera for Compressed Sensing Optical Coherence Tomography.

      Optical coherence tomography (OCT) is a promising imaging technique in medicine and biology, which allows for obtaining high-resolution, cross-sectional images of biological tissues. In the past decade, the imaging speed of OCT is consistently increasing, and currently OCT can acquire three-dimensional (3D) images in real time with imaging speed up to 10-MHz A-scan rate. With such a high imaging rate, OCT system has to acquire a large amount of data, which is too massive for data transmission and storage. Compressed sensing (CS) technique is a powerful method to solve this problem. It exploits the sparsity property of the signal and ...

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    2. Compressed sensing spectral domain optical coherence tomography with a hardware sparse-sampled camera

      Compressed sensing spectral domain optical coherence tomography with a hardware sparse-sampled camera

      We present a sparse-sampled camera for compressed sensing spectral domain optical coherence tomography (CS SD-OCT), which is mainly composed of a novel mask with specially designed coating and a commercially available CCD camera. The sparse-sampled camera under-samples the SD-OCT spectrum in hardware, thus reduces the acquired image data and can achieve faster A-scan speed than conventional CCD camera with the same pixel number. Compared with a conventional SD-OCT system, the CS SD-OCT system equipped with the sparse-sampled camera has better fall-off and SNR performance. CS-OCT imaging of bio-tissue is also demonstrated.

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    3. Conjugate transformation for dispersion compensation in optical coherence tomography imaging

      Conjugate transformation for dispersion compensation in optical coherence tomography imaging

      In optical coherence tomography (OCT), the sample dispersion tends to increase the signal width and hence lower down the resolution, resulting in serious image quality degradation, especially for imaging over a large depth range or media with large dispersion coefficient. In this letter, instead of the conventional Fourier transformation for dispersion compensation that can compensate the image only ideally at a certain depth, a novel transformation, as called conjugate transformation, is proposed to achieve high resolution at all depth by utilizing the conjugate function of the signal itself as an optimized integral kernel. A large dispersion media of ZnSe is ...

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    4. Endoscopic optical coherence tomography with a focus-adjustable probe

      Endoscopic optical coherence tomography with a focus-adjustable probe

      We present a focus-adjustable endoscopic probe for optical coherence tomography (OCT), which is able to acquire images with different focal planes and overcome depth-of-focus limitations by image fusing. The use of a two-way shape-memory-alloy spring enables the probe to adjust working distance over 1.5 mm, providing a large scanning range with high resolution and no sensitivity loss. Equipped with a homemade hollow-core ultrasonic motor, the probe is capable of performing an unobstructed 360 deg field-of-view distal scanning. Both the axial resolution and the best lateral resolution are ∼ 4    μm ∼4  μm , with a sensitivity of 100.3 dB. Spectral-domain ...

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    5. Feature Of The Week 11/26/2016: Tsinghua University Demonstrates Optical Computing Technique and Achieves High Speed OCT of 10 Mega-A-Scans/Second.

      Feature Of The Week 11/26/2016: Tsinghua University Demonstrates Optical Computing Technique and Achieves High Speed OCT of 10 Mega-A-Scans/Second.

      In the past few decades, OCT has been applied in a wide range of applications including clinical and material research areas. For some biomedical applications such as surgical guidance, real-time volumetric OCT (4D-OCT) imaging is in high demand. However, for high definition volumetric imaging in real time, i.e., 1000 pixels along 3 spatial dimensions and 30 volumetric imaging per second, the data flow will be 1000×1000×1000×30=30GVoxel/s. To process these massive data is a big challenge to the performance of current GPUs and CPUs. Professor Ping Xue, Postdoc Xiao Zhang and their colleagues from Tsinghua ...

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    6. Optical computing for optical coherence tomography

      Optical computing for optical coherence tomography

      We propose an all-optical Fourier transformation system for real-time massive data processing in high speed optical coherence tomography (OCT). In the so-called optical computing OCT, fast Fourier transformation (FFT) of A-scan signal is optically processed in real time before being detected by photoelectric detector. Therefore, the processing time for interpolation and FFT in traditional Fourier domain OCT can be dramatically eliminated. A processing rate of 10 mega-A-scans/second was experimentally achieved, which is, to our knowledge, the highest speed for OCT imaging. Due to its fiber based all-optical configuration, this optical computing OCT system is ideal for ultrahigh speed volumetric ...

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    7. Ultrahigh-speed optical coherence tomography utilizing all-optical 40 MHz swept-source

      Ultrahigh-speed optical coherence tomography utilizing all-optical 40 MHz swept-source

      We present an ultrahigh-speed optical coherence tomography (OCT) based on an all-optical swept-source with an A-scan rate of 40 MHz. The inertia-free swept-source, which has its output power of 41.2 mW and tuning range of 40 nm and high scan linearity in wavenumber with Pearson’s correlation coefficients r of 0.9996, consists of a supercontinuum laser, an optical band-pass filter, a linearly chirped fiber Bragg grating, an erbium-doped fiber amplifier, and two buffer stages. With sensitivity of 87 dB, high-speed OCT imaging of biological tissue in vivo is also demonstrated.

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    1-7 of 7
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  2. Topics in the News

    1. (7 articles) Tsinghua University
    2. (7 articles) Ping Xue
    3. (6 articles) Chengming Wang
    4. (3 articles) Tianyuan Chen
    5. (3 articles) Ning Zhang
    6. (1 articles) Duke University
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    Ultrahigh-speed optical coherence tomography utilizing all-optical 40 MHz swept-source Optical computing for optical coherence tomography Feature Of The Week 11/26/2016: Tsinghua University Demonstrates Optical Computing Technique and Achieves High Speed OCT of 10 Mega-A-Scans/Second. Endoscopic optical coherence tomography with a focus-adjustable probe Conjugate transformation for dispersion compensation in optical coherence tomography imaging Compressed sensing spectral domain optical coherence tomography with a hardware sparse-sampled camera Feature Of The Week 07/22/2019: Tsinghua University Demonstrates A “Sparse Sampled” Smart CCD Camera for Compressed Sensing Optical Coherence Tomography. Optical coherence tomography through a rigid borescope applied to quantification of articular cartilage thickness in a porcine knee model An Experimental Review of Optical Coherence Tomography Systems for Noninvasive Assessment of Hard Dental Tissues Low-Cost, Portable System Takes OCT Beyond Ophthalmology Comparison of diagnostic performance in assessing the rewiring position into a jailed side branch between online 3D reconstruction systems version 1.1 and 1.2 derived from optical frequency domain imaging Corneal sublayer thickness in patients with pseudoexfoliation syndrome evaluated by anterior segment optical coherence tomography