用激光散斑跨零法监测皮肤血流变化

由皮肤散射形成的动态激光散斑携带了皮肤血流的信息.由于来自运动着的红血球的散射光两次经过皮肤表面,因而受到三次随机调制.本文根据串级散斑的快速时间涨落的特点,提出了用激光散斑的胯零率测量皮肤血流的新方法,给出了跨零率与血流速度参数之间的关系式和实验结果.     

A new approach for noninvasive skin blood imaging in microcirculation

A new noninvasive method is proposed for optically imaging blood under skin. A mini-mirror is used to guide the light incident onto the skin surface, while blocking specularly reflected light from the tissue. Moreover, by using two linear polarizers at right angles, the specular reflection can be reduced further, while also blocking the rough surface scattered light. A circular polarizer may be used to obtain the same effect. As a result, the blood flow beneath the surface of skin can be visualized clearly. The effect of the mini-mirror is also analyzed theoretically and experimentally.     

Optical testing of hard disks

A device and methodology for surface testing of hard disk blanks are presented. A beam of laser light is scanned in a spiral pattern across the disk, and surface defects are diagnosed from the modulation of the scattered light. Since acceptable polish marks also scattered significant levels of light, it was necessary to make use of the directional characteristics of the scattered light in the disk test device.     

The characterisation and application of a pulsed neodymium YAG laser DGV system to a time-varying high-speed flow

Doppler Global Velocimetry (DGV) is a whole-field measurement technique which has attracted significant interest from the fluid-flow research community since its introduction in 1991. Practical implementations of the methodology have focused on two principal laser light sources: the argon ion laser, applied to steady state or slowly varying flows; and the pulsed neodymium YAG laser for the measurement of instantaneous velocity fields. However, the emphasis in the published literature has been very much on research using the argon laser. This paper reports the application of a Q-switched, injection-seeded neodymium YAG laser to the proven Oxford DGV system, and the use of this combination in a short duration unsteady high-speed flow. The pertinent characteristics of the apparatus are described, and the impact of these on the integrity of the resulting velocity measurements is presented. Adaptations to the commercial laser system that make it suitable for application to the measurement of transient high-speed flows are described. Finally, the application of this system to a short duration unsteady flow is described. This application is based on the flow found in a new type of transdermal drug delivery device, where particles of the drug material are projected at high speed through the skin. Whole-field velocities are recorded, and values as high as 800 m/s are evident.     

A laser electro-optic device for the orientation of mass-produced components

An experimental device is described which is used to orientate small industrial components being fed along conveyor belts or in bowl feeders. The component orientation is identified by laser light scattered from discrete regions of the component which moves through a field of view. Subsequent electronic signal processing leads to the control of a pneumatic system used to reject unwanted component modes. The device has been shown to be effective at feed rates up to above 100 components per minute. Flexibility of the device is demonstrated by a number of examples which include the orientation of grub-screws in either one of two stable orientations, and by the orientation of non-cylindrical-shaped components. In these examples, reliability of successful orientation has been found to be greater than 99%.     

A particle timing laser velocity meter

A fluid velocity meter is described; this operates by measuring the time taken for individual dust particles carried in the flow to travel between two points in space. A laser is used to produce two light beams parallel to one another and approximately normal to the flow direction. These beams are focused to two point or line foci in the region of interest: these foci are separated by a distance of the order of 1 mm in the flow direction. A particle crossing both foci in succession gives two scattered light pulses, and the time interval between these is measured by an oscilloscope or digital chronometer. The particles are natural dust particles occurring in the laboratory air or tap water. As in Doppler and fringe anemometers, the advantage of the laser is its spatial coherence: it enables extreme intensity to be obtained in small, well-defined regions. The instrument might be described as a fringe anemometer in which all the light is concentrated into the two end fringes, the others being eliminated.     

Device for UV irradiation of blood with a disposable blood flow system

A device for extracorporal irradiation of blood by UV light with λ=300–400 nm is described. A disposable blood flow system with a specially profiled polymer cuvette is proposed. Mixing of blood during irradiation ensures uniform irradiation of blood cells passing through the cuvette, which makes it possible to enhance the healing effect of the procedure. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 289–292, March–April, 1999.     

Performance analysis of an optical device for cylindrical flow visualizations

The performance of an optical device which allows a laser beam to be converted into a thin cylindrical light sheet is presented; a double conical reflector is associated with a focusing system. The adjustment possibilities of the optical parameters are related according to the Gaussian laser beam theory, sheet diameter and thickness, focusing distance, sheet field depth and power density. An example of the visualization in a Taylor-Couette flow is described.     

Spectroscopic measurement of blood volume and its oxygenation in a small volume of tissue using red laser lights and differential calculation between two point detections

An optical method for measuring blood volume and its oxygenation in a small volume of tissue (<1 cm³) based on the Beer–Lambert law is proposed. Three red laser lights are used because the difference of absorption by oxy- and deoxy-haemoglobin is large, but the absorption of the light by tissue itself causes a large offset value. The scattered light was detected at two receiving points, and the differential calculation between the values obtained from the receiving points were examined to eliminate the offset value. The result shows that the blood volume in skin is obtained from the regression analysis without the offset value. This method was evaluated by using a simple model which contained real blood. The relationship between the concentration of erythrocyte and the output of this method shows good linearity. Also, measuring depth as a function of the distance between incident and receiving points was estimated by using plastic plates having similar optical properties to skin. The maximum measuring depth was almost linear to the distance.     

双光栅夹有机溶液构成的宽带光限幅器

提出一种新光限幅器件并给出初步的实验验证。该器件是将非线笥有机溶液夹在两块不同的浮周型透射光栅之间构成的。     

Fluctuations in doubly scattered laser light

Fluctuations in laser light, doubly scattered by brownian particles, were analysed by measuring the spectral noise power of the photodetector current. Scattering took place at two spatially separated systems of spherical particles. Analytic expressions for the field and intensity correlations are derived. The analytic expressions for the spectrum of the intensity fluctuations of the doubly scattered laser light demonstrate that the frequency dependence of the spectrum depends strongly of the geometry of the experimental arrangement. This is not the case for singly scattered light where in good approximation the spatial and temporal correlations can be separated analytically.Our measurements show that the noise spectrum of the doubly scattered radiation may have the same frequency dependence as the spectrum of the singly scattered light. However, there are conditions where the frequency dependence of the noise of the doubly scattered light diverges markedly from that of the singly scattered light.     

基于菲涅尔反射的光纤激光器功率测量方法

分析了光纤熔接点处的菲涅尔散射光模型,得出熔接点散射光功率与输出光功率成线性关系的结论。利用该结论设计了kW级光纤激光器的振荡器、泵浦源输出功率检测装置,并安装在某kW级光纤激光器上进行了实验。通过建立线性估计函数,利用最小二乘法对光纤熔接点的散射光功率与光纤激光器的振荡器、泵浦源输出功率的关系进行了拟合。通过实验验证了熔接点散射功率与光纤输出功率的线性关系。实验表明利用熔接点散射光功率间接测量光纤激光器输出功率的方法线性度优于4%。     

Temperature distribution in deep tissue phantom during laser irradiation at 1,064 nm measured by thermocouples and thermal imaging technique

Abstract  

Moxibustion generates heat stimulation which expands blood vessels and promotes blood circulation. Furthermore, moxibustion provokes the release of diffuse noxious inhibitory controls (DNIC) to treat and prevent diseases. However, inherent drawbacks, such as pain, burn scars, smoke and bad smells, limit its use. A novel noncontact-type laser therapy device having effect similar to that of commercial moxibustion is being developed using a 1,064-nm infrared (IR) diode-pumped solid state (DPSS) laser. The therapy device allows direct interaction of laser light with the skin rendering temperature distribution both on the skin surface and deep under the skin. We devised a sample holder containing a tissue phantom to measure the three-dimensional temperature distribution with thermocouples inserted deep inside the phantom. Agar gel of 2.5% concentration was used as the tissue phantom in our experiments. Our results revealed that the maximum temperature occurred far below the surface of the tissue phantom, which was heated by laser irradiation at 1,064 nm. This occurrence was also confirmed by a thermal imaging method. In contrast, temperature gradually decreased through the depth of the tissue phantom heated with commercial moxibustion. Simple analytical models were constructed to explain the underlying heat-transfer mechanisms involved in moxibustion and laser irradiation.     

Photoacoustic-guided convergence of light through optically diffusive media

We demonstrate that laser beams can be converged toward a light-absorbing target through optically diffusive media by using photoacoustic-guided interferometric focusing. The convergence of light is achieved by shaping the wavefront of the incident light with a deformable mirror to maximize the photoacoustic signal, which is proportional to the scattered light intensity at the light absorber.     

Fibre-optic systems for dynamic light scattering — a review

‘Photon correlation spectroscopy’ has become a standard method in applied science for analysing the properties of submicron particles in a fluid environment. The fast, local fluctuations in the intensity of the light scattered from such particles are recorded and analysed in terms of the local motions. This has led to the use of the method both to characterize particle geometry and to monitor particle translation as a marker for fluid flow. The advent of fibre-optics has enabled portable, small, remote and more flexible systems to be established in recent years. This paper reviews those instrument designs which have represented advances in the development of fibre-based systems. Emphasis is laid on instruments (a) for monitoring blood flow and (b) for measuring Brownian-induced translatory diffusion in colloidal suspensions.     

Frame-rate analysis of arterial blood flow in human and rat using laser speckle image sensing

In imaging of blood flow by means of a laser speckle technique, we have proposed so far an estimation parameter based on the spatial contrast of speckle patterns observed for the blood flow in skin tissue and a blood vessel. This parameter enable us to image a relative blood flow distribution from a single speckle pattern, thus, it analyzes the blood flow with a frame-rate of an imaging device used. In this study, we investigated availability of this parameter for detecting changes in arterial blood flow caused by medication and cold stimulation to the skin tissue. Experiments were conducted for an anesthetized rat and a human wrist to confirm the feasibility of the present parameter.     

Full-field laser metrology for fluid velocity measurement

This paper reviews the development of full-field laser metrology from its inception as a dynamic extension of scattered light speckle photography, a voherent optical technique originally developed to make full-field measurements of quasi-static displacements in transparent solids, to its present applications in fluid dynamic studies. The full-field laser velocimetry technique, including both double exposure and multiple exposure recording methods, is discussed in detail, and comparison is made of their advantages and disadvantages in applications to steady and unsteady flows. Both the coherent light speckle and the particle image modes of operation are defined and evaluated. Computer aided ‘point-wise’ (Young's fringe) and ‘global’ (Fourier filtering) methods of optically analyzing the specklegrams are also discussed. Finally, experiments in which full-field laser velocimetry has been applied to a study of convective flow in a liquid are described, thus illustrating the potential of this new, non-onvasive optical technique.     

Electro-optical granulometer for measurements of flowing particles

An electro-optical technique is described for the measurement of the size distribution of particles from 2.5 μm upwards, in a flow. The apparatus utilizes a white light source, a photodiode array and particle-sizing electronics. The data acquisition system is a multichannel analyser or a microcomputer. This device is an extension to the flow case of a previous device designed for static size analysis, and a critical comparison with size acquisition systems commercially available is given. Shape of particles and outline of waveform during particle detection are discussed.     

Doppler standard deviation imaging for clinical monitoring of in vivo human skin blood flow

We used a novel phase-resolved optical Doppler tomographic (ODT) technique with very high flow-velocity sensitivity (10microm/s) and high spatial resolution (10microm) to image blood flow in port-wine stain (PWS) birthmarks in human skin. In addition to the regular ODT velocity and structural images, we use the variance of blood flow velocity to map the PWS vessels. Our device combines ODT and therapeutic systems such that PWS blood flow can be monitored in situ before and after laser treatment. To the authors' knowledge this is the first clinical application of ODT to provide a fast semiquantitative evaluation of the efficacy of PWS laser therapy in situ and in real time.     

Doppler velocimetry in a supersonic jet by use of frequency-modulated filtered light scattering

A new nonintrusive velocimetry diagnostic that combines the sensitivity of frequency-modulated (FM) absorption spectroscopy techniques and the spectral discrimination afforded by atomic-vapor absorption filters is presented. Doppler-shifted light from a FM Ti:sapphire laser scattered from a supersonic flow is imaged through a potassium-vapor cell and is detected by FM spectroscopy. The difference between the potassium resonance frequency and the laser frequency when the scattered light is in resonance is the flow-induced Doppler shift.