Non-contact, imaging photoplethysmography (IPPG) uses video sequence to measure variations in light absorption, caused by blood volume pulsations, to extract cardiopulmonary parameters including heart rate (HR), pulse rate variability, and respiration rate. Previous researches most focused on extraction of these vital signs base on the focus video, which require a static and focusing environment. However, little has been reported about the influence of defocus blur on IPPG signal’s extraction. In this research, we established an IPPG optical model in defocusing motion conditions. It was found that the IPPG signal is not sensitive to defocus blur by analysis the light intensity distribution in the defocus images. In this paper, a real-time measurement of heart rate in defocus and motion conditions based on IPPG was proposed. Automatically select and track the region of interest (ROI) by constructing facial coordinates through facial key points detection, obtained the IPPG signal. The signal is de-noised to obtain the spectrum by the wavelet filtering, color-distortion filter (CDF) and fast Fourier transform (FFT). The peak of the spectrum is corresponded to heartbeats. Experimental results on a data set of 30 subjects show that the physiological parameters include heart rate and pulse wave, derived from the defocus images captured by the IPPG system, exhibit characteristics comparable to conventional the blood volume pulse (BVP) sensor. Contrast experiment show that the difference between the results measured by both methods is within 3 beat per minute (BPM). This technology has significant potential for advancing personal health care and telemedicine in motion situation.
We describe the application of wavefront coding technique for infrared imaging system to control thermal defocus. For traditional infrared imaging system, athermalization is necessary to maintain imaging performance which may increase complexity and cost of the imaging system. Wavefront coding includes a phase mask at the pupil which can re-modulate wave front so as to produce an encoded image. After digital processing, the system is insensitive to defocus. In this paper, the combination of wavefront coding technique and infrared imaging system has been discussed. We report here the optic design of the wavefront coding IR system based on Zemax. The phase mask is designed to ensure that the modulation transfer function (MTF) is approximately invariant in the range of working temperature. Meanwhile, we designed three IR systems to put up contrast experiments. System one and two are designed to compare the influence before and after the insertion of phase mask. System three is designed to compare the imaging performance before and after reducing lens in wavefront coding IR system. The simulation results show that the infrared imaging system based on wavefront coding can control thermal defocus in a temperature varying from -60ºC to 60 ºC, at the same time the weight and cost of optical elements are reduced by approximately 40%.
Optical technology is an important and immerging technology for non-destructive and rapid detection of pork freshness.
This paper studied on the possibility of using multispectral imaging technique and scattering characteristics to predict the
freshness parameters of pork meat. The pork freshness parameters selected for prediction included total volatile basic
nitrogen (TVB-N), color parameters (L *, a *, b *), and pH value. Multispectral scattering images were obtained from
pork sample surface by a multispectral imaging system developed by ourselves; they were acquired at the selected
narrow wavebands whose center wavelengths were 517,550, 560, 580, 600, 760, 810 and 910nm. In order to extract
scattering characteristics from multispectral images at multiple wavelengths, a Lorentzian distribution (LD) function
with four parameters (a: scattering asymptotic value; b: scattering peak; c: scattering width; d: scattering slope) was used
to fit the scattering curves at the selected wavelengths. The results show that the multispectral imaging technique
combined with scattering characteristics is promising for predicting the freshness parameters of pork meat.
This paper described a control system of mobile navigation robot for precision spraying in greenhouse environment,
which were composed of main control module, motor driving module, ultrasonic detecting module and wirless remote
control module. The hard circuits of control system were built. The main control module used ARM7TDMI-S-based
LPC2210 micro-processing controller. The motor driving module consisted of voltage amplifier circuit based
SN74LS245N and DM74LS244N chips, RC filter circuit, and HM-YZ-30 DC brush motor driver. The ultrasonic
detecting module consisted of four standard ultrasonic ranging modules which were arranged on the four sides around
the mobile navigation robot, and used GM8125 chip to expand serial communication interfaces. An obstacle-avoiding
strategy and its algorithm were proposed and the control programs of mobile navigation robot were programmed. The
mobile navigation robot for spraying can realize the actions such as starting and stopping, forward and backward moving,
accelerate and decelerate motion, and right and left turn. Finally, the functional experiments of the mobile navigation
robot were conducted in the laboratory environment. The results showed that the ultrasonic detecting distance of the
robot was 50.5mm-1832.0mm and detecting blind zone was less than 50mm, the ultrasonic detecting angle of individual
ultrasonic detecting module of robot was similar to U-shaped and its vaule was about 45.66°, and the moving path of
navigation robot was approximately linear.
A wedge-shaped probe is developed and applied for the detection of transient electrical signals in an ultrafast scanning
tunneling microscope measurement system. The probe is composed of a low- temperature grown GaAs photoconductive
switch and a metal tip with a diameter of 5 micrometers. The designed probe functions as a sampler of transient signals
generated by a sample of coplanar strip photoconductive switch with ultrafast optical pulses of 100 fs in the ultrafast
measurement system. The shape of the probe makes the approach of the probe to the sample in a way that is much easier
than the traditional rectangular one. The metal tip is attached to the coplanar strip transmission line integrated in the
photoconductive switch. The design of the probe is presented and its performances have been reported in this paper.
Photo of the wedge-shaped probe is given and transient signals in picoseconds were observed in contact mode with the
developed wedge-shaped probe.