In this paper, we propose a differential single-pixel imaging (SPI)
approach based on time stretch and demonstrate its capability for image quality
improvement and reconstruction time reduction versus the conventional timestretch-
based SPI approach.
In this paper, we present a high-speed single-pixel imaging (SPI) system based on all-optical discrete cosine transform (DCT) and demonstrate its capability to enable noninvasive imaging of flowing cells in a microfluidic channel. Through spectral shaping based on photonic time stretch (PTS) and wavelength-to-space conversion, structured illumination patterns are generated at a rate (tens of MHz) which is three orders of magnitude higher than the switching rate of a digital micromirror device (DMD) used in a conventional single-pixel camera. Using this pattern projector, high-speed image compression based on DCT can be achieved in the optical domain. In our proposed system, a high compression ratio (approximately 10:1) and a fast image reconstruction procedure are both achieved, which implicates broad applications in industrial quality control and biomedical imaging.
In this paper, a systematic review is made on our research related to photonics-assisted compressive sampling (CS)
systems including principle, structure and applications. We demonstrate their utility in wideband spectrum sensing and
high throughput flow cytometry. Photonics-assisted CS systems not only can significantly reduce the data acquisition
rate but also can achieve a large operational bandwidth (several GHz or even a few tens of GHz), which is one to two
orders of magnitude larger than that of traditional electric CS systems. Single-channel and multi-channel photonicsassisted
CS systems are presented in this paper and demonstrated to enable accurate reconstruction of frequency-sparse
signals from only a few percent of the measurements required for Nyquist sampling. On the other hand, we also
implement time-stretch-based single-pixel imaging systems with high frame rates, three orders of magnitude faster than
conventional single-pixel cameras. To show their utility in biomedical applications, a real-time high-throughput imaging
flow cytometer is demonstrated. In general, photonics-assisted CS systems show great potential in both wideband
spectrum sensing and biomedical imaging applications.
Proc. SPIE. 9720, High-Speed Biomedical Imaging and Spectroscopy: Toward Big Data Instrumentation and Management
KEYWORDS: Optical fibers, Optical design, Digital signal processing, Compressive imaging, Image compression, Imaging systems, Cameras, Sensors, Image restoration, Single mode fibers, Image quality, Digital micromirror devices, High speed imaging, Frequency conversion, Active optics, Electrooptic modulators
Compressive sampling (CS) is an emerging field that provides a new framework for image reconstruction and has potentially powerful implications for the design of optical imaging devices. Single-pixel camera, as a representative example of CS, enables the use of exotic detectors and can operate efficiently across a much broader spectral range than conventional silicon-based cameras. Recently, time-stretch CS imaging system is proposed to overcome the speed limitation of the conventional single-pixel camera. In the proposed system, as ultra-short optical pulses are used for active illumination, the performance of the imaging system is affected by the detection bandwidth. In this paper, we experimentally analyze the bandwidth limitation in the CS-based time-stretch imaging system. Various detector bandwidths are introduced in the system and the mean square error (MSE) is calculated to evaluate the quality of reconstructed images. The results show that the decreasing detection bandwidth leads to serious energy spread of the pulses, where the MSE increases rapidly and system performance is degraded severely.
A wavelength-swept fiber optical parametric oscillator (FOPO) based on dispersion tuning technology at wavelength around 1 μm is demonstrated. A continuous wave single-longitudinal-mode ytterbium doped fiber laser with a line-width of 0.05 nm is modulated through a LiNbO3 Mach-Zehnder modulator to be a pulsed source with variable repetition rate. The pulsed source is amplified with a two-stage ytterbium doped fiber amplifier (YDFA) to a mediate power and a high power YDFA to peak power higher than 40 W. And a homemade 50-m photonic crystal fiber (PCF) which provides the optical parametric gain is pumped by the pulsed source. The optical modulator is driven by a frequency-swept electrical clock signal with frequency ranges from 107.24 MHz to 107.31 MHz. Thus the FOPO generates a wavelength-swept light source with a range of 80 nm centered at 1065.10 nm. Through careful customizing the sweeping rate of the driving clock signal, the sweeping rate of the parametric oscillator can be up to 10 kHz, which is limited by currently used electrical sweeping source. The generated pulses train are with pulse width of about 110 ps. For the electrical scan is used instead of the traditional mechanical scanning method in conventional wavelength-swept sources, it performs better stability under prolonged operation. The wavelength-swept FOPO is potential to be applied in OCT systems for its good stability and advantaged wavelength band.