Conventional FMCW-LiDAR uses a high-performance ADC to obtain digitized signals and analyze bit frequencies through FFT to measure distance. High accuracy, SNR, and real-time operation in FMCW Lidar requires a high sampling rate ADC and many FFT points, which is a burden on hardware and signal processing.
In this study, a frequency-mixed FMCW-LiDAR was designed to overcome the limitation of the conventional system. The local oscillator LO was supplied in the form of an electric chirp signal, and the resolution and measurable range of the signal are determined according to the range of sweep frequency. By mixing the sweeping LO and beat signals, the proposed system enables frequency analysis on the time axis, enabling efficient analysis in data acquisition.
An optical interferometry measurement system has lots of advantages, and it is widely used in various applications. For a longer range and higher speed of optical interferometry measurement, it is required a higher burden of data amount during the data acquisition (DAQ) process. A novel light source called comb-swept laser was proposed to solve the heavy load in DAQ, but comb-swept laser needs a solution for the distance aliasing problem. Recently, optical Vernier sampling was suggested to solve the distance aliasing problem with two different free spectral range (FSR) combs. This research introduces a new type of FSR-tunable comb-swept laser for optical Vernier sampling to measure long-range with high speed without high-speed DAQ.
We propose a fast surface profiling measurement method using a color confocal microscope based on time-encoded spectroscopy. The chromatic confocal microscopy can acquire depth information at high speed because it does not require depth scanning. On the other hand, in chromatic confocal microscopy, depth information is obtained through the wavelength of the reflected light, which is difficult for wide field imaging. By applying time encoded spectroscopy technology, depth information can be obtained at high speed through time information of reflected light. As a result, we could obtain the 3D surface shape without scanning by measuring the reflected light through the CCD over time.
A multi-spectral laser speckle contrast imaging (MS-LSCI) system is proposed using only a single wavelength-swept laser, which provides both highly coherent and multi-spectral outputs to simultaneously generate laser speckle contrast images and multi-spectral images, respectively. Using a laser light swept from 770 to 821 nm at a repetition rate of 5 Hz and a CCD camera of 335 fps, 67 multi-spectral frame images are acquired in 0.76 nm wavebands over 51 nm spectral range. The spectral sub-windowing method of single wavelength-swept laser source is used to solve the lack of spectral information from a few individual light sources, which is a limitation of conventional MS-LSCI systems. In addition to the speckle flow index from the LSCI frames, the multi-spectrally encoded images can generate additional images of spectral absorbance. To further examine the performance of the MS-LSCI system, an in vivo cuff-induced ischemia experiment was conducted to show the real-time imaging of hemodynamic and blood oxygen saturation changes simultaneously over the entire 2.5 cm × 4.5 cm field of view.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.