This paper briefly summarizes a method of imaging inside a scattering medium with visible and near infrared lasers and provides new data on coherence properties of scattered light that help define practical limitations of chrono-coherent imaging. This method has been named chronocoherent imaging (CCI) because it coherently records a time correlated image by using holographic recording techniques.

1.1 Basilar membrane mechanics as the basis of inner ear function The function of the hearing organ ha been based mainly on the basilar membrane mechanics because it is the only structure accessable from the outside and therefore has been measured extensively Bekesy,1960; Johnstone & Boyle, 1967; Rhode, 1971, 1980; Sellick et a!. 1982; Robles et aL, 1986). Although the organ of Corti consists of a complex and highly organized arrangement of sensory cells, the role of individual cells in mechanical analysis of the auditory stimuli was not known. 1.2 The avialable measuring techniques not suitable for cellular vibration measurements The basilar membrane vibrations were measured with (i) capacitive probe (Wilson & Johnstone, 1972); (ii) homodyne interferometry (Khanna & Leonard, 1982); and (iii) Mossbauer method (Johnstone & Boyle, 1967; Rhode, 1971). The first technique required the placement of the probe close to the surface to be measured while the other two techniques required the placement of an optical reflector or radioactive foil on the structure to be measured. In order to place the foil on a cell the overlying cells or structures would have to be removed, seriously compromising the integrity of the cochlea and altering its response. 1.3 Need for cellular vibration measurement Correlations made between the basilar membrane tuning and the outer hair cell condition suggested that the outer hair cells may be directly involved in the mechanical tuning of the cochlea (Khanna & Leonard, 1982, 1986 a, b). These results provided the inspiration to build a non-invasive optical vibration measuring system with which the mechanical response of individual cells could be measured in an intact organ. 1.4 Organization of ITER It became quite clear about ten years ago that state of the art technology in several fields was needed to design and build the necessary measuring instrument and to fully exploit its potential. An international team of experts from several fields of science were therefore invited to help design the instrument and to carry out the cellular measurements with it. This International Team for Ear Research is called ITER. A preliminary report of our progress has been published (ITER, 1989).

A new method has been developed for determining intraocular distances. It is based on interferometry methods in conjunction with the laser Doppler technique, using partially coherent light. In a first approach two distances are measured: the axial eye length (distance cornea-retina) and the thickness of the retina. An accuracy of +/- 10 micrometers for optical distances is achieved. Comparisons with the usual ultrasound technique show a good agreement also for geometrical distances.

The shape of the tympanic membrane is fairly complicated and seems to be of significant importance in the coupling of the acoustic sound pressure in the external ear canal to the motion of the middle ear ossicles. Precise measurements of the tympanic membrane shape are not available in literature. To measure the shape of a very thin, curved biological membrane a technique is required which does not deform the surface during the measurement. Casting techniques are therefore not well suited. A noncontacting measurement technique based on moire interferometry proved to be a better tool. A moire shift interferometer was used to measure with great precision the shape of the external surface of human and cat tympanic membrane. The dense matrix of z(x,y) values thus obtained does not only describe the shape with high spatial resolution but may also be used to calculate different geometrical parameters. As an example of direct application the authors have calculated the area of the curved surface to the pars tensa and pars flaccida for a human and a cat tympanic membrane.

To measure the surface shape and shape change of soft biological material, the use of a noncontacting metrological technique is imperative. One of these techniques is moire contouring, which is particularly interesting because of its simplicity and low cost. We propose a method to mathematically reconstruct a surface shape from moire topograms. The method is based on the recording of three topograms which are shifted in phase by translating the object. The method is implemented in an apparatus which fully automatically performs all required steps to finally yield a 512 by 512 point matrix of surface height values, with a height measuring resolution of 20 micrometers . The resolution for measuring small height displacements is 2 micrometers . Due to this high resolution, it is possible to investigate the deformation of the tympanic membrane, caused by small pressure changes in the middle ear cavity. Full field deformation data are shown. The data can be used to obtain information on the movement of the manubrium, or to calculate volume displacements and surface area changes.

Society of Facial Research is used frequently. It is of great value clinically, but the method has several weak points concerning objective and quantitative assessment. This study uses moire topography to solve these problems. mA moire camera, FM3013, of the lattice irradiation type was used for measurement of the face. Five moire photographs were taken: at rest, wrinkling the forehead, closing the eyes lightly, blowing out the cheeks and grinning. The degree of facial palsy was determined by the Asymmetry Index (AI) as a measure of the degree of facial deviation. Total AI was expressed as the average AI based on calculations of the measurement in 5 photos. Severe paralysis is represented by an AI of more than 20%. Partial paralysis has a range of 20-8%. Nearly normal is judged to be less than 8%. Ten normal individuals are measured as control and show an AI of 3% or less. Moire topography is useful in assessing the recovery process because it has the benefit of making the site and grade of palsy easily achieved by the AI and the deviation in its patterns. The authors propose that the moire method is better for an objective and quantitative evaluation than the society's method.

Laser speckle limits the resolution that can be achieved in holography. Time- varying speckle is even more troublesome, as it can destroy the coherence needed to record a hologram or the correlation needed to obtain fringes in holographic interferometry. This paper looks at the problems these effects can cause in biomedical holography and at how these problems might be minimized. Applications of the time-varying speckle itself, some already widely used, others more speculative, are also discussed.

Double-exposure speckle photography was used for measuring the in-plane deformation of broken lower legs bones supported with different fixing devices under axial loading. An osteosynthesis plate, an external fixator, and an intramedullary nail mounted on the tibial shaft were tested. The results for different loading conditions were analyzed and compared with those obtained by holographic interferometry.

The aim of the present paper is to demonstrate the applicability of the holographic interferometric microsrop using photorefractive BTO crystal as a recording medium. The changes in the stable cell line LSTC-SF1, infected with a virus causing Aueski disease are investigated by comparison of the infected and uninfected sells's states.

The human tooth as an optical system, or more exactly as an optical device, is considered. In this report the authors examine the main properties of such a system.

The statistical evaluation of the size, shape, density and regularity of the cells in the human corneal endothelium is an important diagnostic technique. A method based on the Fourier transform of the cell boundaries was developed which can yield these statistical properties. The development of a hybrid optical/digital technique to obtain these statistical perimeters is our goal. The input images were tracings of human endothelial cell patterns. The optical Fourier transform of each image was obtained, and the radial projection and the angular correlation function were plotted versus distance and angle respectively. The average size of the cells was obtained from the first peak of the radial projection. The width of this peak is related to the coefficient of variation of the average cell size. The separation of the peaks in the normalized angular correlation plot is related to cell shape. This method is suitable for rapid analysis of large numbers of endothelial cell images. This technique may have potential for diagnostic ophthalmology.

A new algorithm for the reconstruction of a real image from its Hartley transform modulus only is presented based on the general theory of the amplitude-phase retrieval problem. From our simulating calculation, it is shown that the image reconstruction can be successfully achieved from its Hartley transform modulus only by using the Y/G algorithm. The influence of noise contained in Hartley transform intensity on the convergent solution is also examined in detail.

After digitizing and preliminary processing of a few roentgenographs, the optimum storage regime is determined. Then the pattern is improved. By means of standard fine differentiating procedures in the frequency area compared with special alternative ones the cysts are contoured and localized. Pattern correlation recognition made on the basis of the Singular Value Decomposition is applied.

The expansion of the cornea of fresh enucleated bovine eyes was tested by means of double-exposure holographic interferometry. The tissue was subjected to small increases in intraocular pressure. Preliminary results indicate that each bovine cornea has its own special elastic expansion which appears in a different fringe pattern.

For severe otitis media with effusion, insertion of a ventilation tube is performed for the purpose of ventilation of the middle ear cavity and normalization of the eustachian tubular function and middle ear mucosa. The ventilation tube is left in place for as long as several months or even a few years. However, the influence of the indwelling tube on vibration of the tympanic membrane is unknown. Therefore, the authors observed the influence by means of time-averaged holography using human tympanic membranes. The following results were obtained. After insertion of a ventilation tube, vibration pattern of the tympanic membrane was not obviously changed, but the vibration amplitude of the tympanic membrane was decreased, especially at 500 Hz. Generally speaking, the change caused by insertion of a ventilation tube was very small. Also, the vibration pattern of perforated tympanic membrane was not changed, but the vibration amplitude of perforated tympanic membrane was decreased at the low frequency area.

Mechanical properties of tibia fixed with an external fixative device (external fixator) were investigated under some simulated loading conditions. Deformation measurements were performed using double exposure holographic interferometry and real-time holographic interferometry. According to the results of the holographic interferometry, strains on the fixation pins and rods were also measured using strain gauges. The results showed that, with most types of external fixator, dislocations of both fractured ends were mainly caused by decrease in strength of the fixation pins. With increase in strength of fixation pins, angular deformation of the rod was more obvious. Increase in the strength of the rod was not always effective in decreasing dislocation of both fractured ends. Changes in bracing technique with marked change in rigidity of external fixator were useful to decrease dislocation of both fractured ends.

The piezoelectric properties in bone have been recognized for nearly three decades. Most investigations concerning this effect have focused on strain induced potentials. In this paper, the authors describe a quasi-heterodyne holographic system used to measure the piezoelectric effect in bone. Data are acquired at video rates using four phase shifts and the phase is reconstructed at discrete locations over the surface of the bone. Phase changes can be measured to a precision of at least 4 degrees. The interference fringes are observed in real-time by producing a hologram of dry, bovine tibia held in a vice. A voltage is applied to electrodes on the surface of the bone and a single component of surface displacement is measured. Because the piezoelectric coefficients in bone are extremely small, approximately a picometer per volt, it is useful to improve the signal-to-noise ratio of the technique. The method the authors have pursued is to average over repeatedly acquired data sets. The presence of air turbulence, however, requires that compensation for spurious phase changes be applied to the data before averaging. We have developed a technique which compensates for low spatial frequency phase changes, allowing averaging over temporally separated data sets. The basis of the technique is to surround the object by a stationary control. The phase over this control is used to correct for the phase over the object. The corrected phase images are averaged together to improve the background signal-to-noise. The concept was evaluated on an aluminum blade and was shown to improve the phase estimate. Preliminary results on bone indicate cantilever bending due to an applied voltage with a piezoelectric constant of 0.6 pm/V.

The paper presents a system that may be used in a wide range of biomedical fields. The system can be applied in conjunction with different optical techniques: (a) holography, (b) moire method, (c) speckle techniques, (d) photoelasticity. The system has been built in such a way that an operator with average skills will be able to use it; data acquisition and processing are fast and almost automatic. A brief description of the system, its main components and the basic theory behind it, are given. The use of the system is illustrated with examples in orthopedics and in the cardio-vascular area.

A real-time holographic interferometry system was developed for the inspection and engineering analysis of disposable reagent containers used in a clinical chemistry centrifugal analyzer. The system featured a commercial holographic camera plus a specially designed machine vision apparatus and permitted the manual or automated detection of bonding flaws which could result in field failure.

The unique and useful features of holography in image formation and in image analysis can make it a valuable addition to the techniques used in medical research and diagnosis. By combining holography with endoscopic imaging it is possible to obtain holographic imaging inside natural cavities of the body or in other difficult to access environments. Possible applications of endoscopic holography are presented.

The possibilities of this learning system made for interferogram and speckle-correlogram processing are reviewed. Its easy learning and robustness seem to be useful both for industrial applications and for experiment.

Resolution criteria for resolving two line images under coherent and incoherent illumination are presented. This technique has been used to interpret psychophysical data obtained from hyperacuity paradigms.

To visualize electron transfer interactions of proteins in the cellular nieinbrane, we have developed a polarized laser flash-induced anisotropy decay imaging. The time-resolved anisotropy is particularly sensitive to protein-protein interactions. This technique has been successfully applied to examine formation and dissociation of electron transfer complex in adrenal cortex and liver. Electron transfer plays a significant role for steroid hormone synthesis from cholesterol in adrenalcortex and for drug metabolism in liver such as detoxification of chemical compounds. Several redox partners perticipate in dynamic electron transfer interactions. The terminal enzyme cytochrome P-450 receives electrons to activate molecular oxygen, resulting in hydroxylation of various substrates.

In the paper diffraction of focused laser beam in thin blood-vessels (TBV) is discussed. Theoretical description of this process is given, a number of model experiments are carried out and TBV scattering in biological objects in vivo is analysed. Relations, establishing connection between scattered field and differential characteristics of blood flow in vessels, diameter of which are about or smaller than those of erythrocytes, are obtained. Analysis of theoretical model correctness is carried out. The paper also contains description of two modifications of a sensor for analysis of diff use scattering biological objects vibrations. The modifications are based on modified homodyne Michelson speckle-interferometer and laser self-excited oscillator with fiber-optical delay line.

This paper presents the results of experimental investigations of a series of conformationally inhomogeneous compounds with polarization sensitive coherent active (anti-Stokes) Raman scattering spectroscopy (PS CARS). Interpretation of vibrational spectra is refined and spectroscopic parameters are determined of resonances of complex spectral band of n-penthane (bands at 868 and 841 cm'), 5,5-dimethyl, 2-ethinyle, 1,2-dioxane (bands at 949 and 910 cm1) which were not resolved previously with use of spontaneous Raman scattering spectroscopy (SRS). Thereby the principle of holographic spectroscopy was realized and tested in the full scale.

Currentmethods ofdetermining the shape and elevation ofthe cornea!surface are inadequate both in terms ofaccuracy and extent. Much of the corneal surface is missed by these methods -particularilythe critical center and most of the periphery. All current measuring techniques assume this surface to be spherical -which it is not. Mathematical assumptions have been employed to reconstruct the surface. These assumptions fall short of the accuracy required for realistic assessment of the effect of external influences on corneal shape. Modern surgical methods designed to modulate the corneal surface curvature or alter the refractive state of the eye demand precise measurement of this surface -the main refractive element of the human eye. Single side-band holographic techniques provide the means whereby this demand can be realized. Surface elevations in the sub-micron range can be readily imaged with this technique.

Previous attempts to analyze the corneal surface have been limited to geometric interpretation of ring displacement (Placido disc technology). Use of holographic interferometry allows real time optical measurement of the corneal surface. Clinical examples of holographic interferometry will be presented.