Access provided by: anon Sign Out. Microwave holographic interferometry Abstract: Microwave holography is an extension of the optical holography to the microwave field.
In fact, by using a well-known characteristic of the holographic process, it is possible to record the hologram at frequencies very far from the optical region microwave and to reconstruct a visible image by laser light. This paper describes the experimental apparatus and the technique used for obtaining a satisfactory optical wave reconstruction from microwave holograms.
The resolving power of the system which was experimentally tested, and visible images of microwave transparencies and of a back scattering object are given. As an alternative application of the microwave holography together with the optical wave reconstruction, in this paper, extension of holographic interferometry to the microwave region is suggested, and the visible image of a deformed object crossed by fringes due to microwave interference is also shown.
Holographic interferometry (HI) is a technique which enables static and dynamic displacements of objects with optically rough surfaces to be measured to optical. Holographic interferometry (HI), which provides interferometric comparison of real objects or events separated in time and space, is a technique of unparalleled .
The laser, the optical components for steering and shaping of object and reference beams, the experimental model, and the photosensitive material used for recording of holograms were rigidly mounted on top of the optical table by means of magnetic bases. One of the beams is directed by mirrors, expanded by means of a spatial filter microscope objective and a pinhole assembly , and is used to illuminate the experimental model to be recorded. The second beam is known as the reference beam and is not modulated by any intervening object. The spacing of the fringes is entirely dependent on the angle between the two beams and the wavelength of the light used; the fringe opacity is related to the intensities of the interfering beams.
The holographic plate consists of a highly sensitized emulsion that coated on a glass plate.
The hologram bears no resemblance to the original object, to interpret a hologram we need to reconstruct the image. This reconstruction wave must be identical to the reference wave used during the formation of the hologram. This process is called reconstruction.
On the same record plate before processing, another exposure corresponding to the deformed portion of the object for example: skull with an activated appliance in palate was recorded. These two reconstructed image waves interfered giving rise to an image with number of bright and dark fringes on the image.
From the fringe pattern the magnitude and direction of displacement can be calculated. Wedenhal P. Dermaut et al studied the bone deformation by class II elastic forces on double exposure holograms.
Gerrit kragt and Herman S Duterloo evaluated the initial effects of orthopedic forces on a macerated human skull using laser holography. Holography used to compute. Palvin et al studied mechanical reactions of facial skeleton to maxillary expansion determined by holographic interferometry.
Duterloo et al studied macerated human child skulls subjected to high-pull headgear traction. Displacements were measured using holography. Harradine et al carried out a pilot study using holograms as substitute for study casts. Legan et al evaluated displacements in the craniofacial complex during mid palatal suture opening using holography.
Batista et al evaluated stress area induced by rapid expansion appliance using double exposure holography. This transforms the image of the object into three dimensions. S, the patient records should be kept until 10 years after orthodontist retires from practice. Stetson put forth the idea that each mode existed in both the object and in the reference beam, and each pair recorded a separate hologram in the photographic plate. When these were reconstructed, both recordings reconstructed simultaneously from the same laser beam and the fields were then mutually coherent.
Powell objected to this idea, because it implied that the hologram had the power to coherently reconstruct fields that were incoherent during its recording. The resulting arguments gave rise to a set of experiments that were later published in Later, in April , Stetson and Powell obtained real-time interference patterns between a real object and its holographic reconstruction.
Since its introduction, vibrometry by holographic interferometry has become commonplace. By sequential imaging of frequency sidebands, the issue of fringe counting has been alleviated. Multiplexed measurements of optical sidebands   enable quantitative measurements of out-of-plane vibration amplitudes much smaller than the optical wavelength.
In off-axis configuration, holographic interferometry is sensitive enough to enable wide-field, laser Doppler imaging of optical fluctuations in amplitude and phase, either with a slow or a fast camera. A slow e. By shifting the frequency of the reference beam, the lowpass filter becomes a bandpass filter centered at the detuning frequency, and selective narrowband detection and imaging can be performed. This method permits microvascular blood flow imaging,  and wide-field measurement of photoplethysmograms by detection of out-of-plane tissue motion. It can be used for pulsatile blood flow imaging.
From Wikipedia, the free encyclopedia. The form of the fringe pattern is related to the changes in surface position or air compaction. Many methods of analysing such patterns automatically have been developed in recent years.