Video Recording Heads Research Articles

Panoramic Video: Recording and Representing the Digital Heritage Experience

In an essay on architectural representation, Stan Allen (2000) wrote about a paradoxical nature of built forms: “Buildings are presumably more tangible and physically present than drawings, yet it is only in the experience of the building that the most intangible aspects of reality can be made visible.”Documenting a heritage site is difficult since no representational method can make an exact copy without loss. This paper specifically examines panoramic recording media and related technologies as new means to archive and represent architectural heritage. It looks at cost effective and widely available platforms such as 360 video recording, YouTube, and immersive Head Mounted Display (HMD) equipment. Tests with subjects are conducted to probe how the experience of recorded panorama compares to the spatial and temporal experience in the physical space. For instance, the subjects with HMD are tested for the ability of sensing the correct scale and proportion of spatial forms in the playback. Through analysis of the test results, discussions are made as to the roles such systems can play in conveying the spatial environment, especially in representing some of its intangible aspects.The paper shows examples of prototype designs for exhibition that utilize panoramically recorded onsite footage in derivative forms. Recordings of sites such as Palladio’s villas and the Acropolis in Athens are used to demonstrate spatial and temporal editing, interactive panoramic walk-through combined with a map, and creation of a framed-video narrative reduced from panoramic videos. These methods illustrate a range of possibilities that put each dislocated recording back into context while controlling a balance between the viewer’s exploration and the intent of the curation, and shed a light on what is often difficult to achieve by other means of representations.

The influence of head position and head position change on spontaneous body posture and motility in full-term AGA and SGA newborn infants

No consensus exists concerning the influence of head position and head position change on body posture and motility. Especially the existence of an asymmetric tonic neck reflex (ATNR) in full-term newborns is an issue of discussion. Three-hour video recordings were made of 15 full-term appropriate for gestational age (AGA) and 15 full-term small for gestational age (SGA) infants between the third and eight postnatal day. During a playback of the video recording head position, head position change and several movement patterns of the four limbs were fed into a computer using an event-detecting program. Furthermore, spontaneous head turnings were selected and body posture just before, immediately at and 1 min after the head turning were sketched. The data were analyzed concerning: (1) influence of head position on symmetry of movement of the four limbs; (2) the existence of an ATNR and ATNR-related patterns. In both AGA and SGA infants all movement patterns except hand-face and hand-mouth contact showed a symmetrical distribution, independent of head position. Furthermore, the occurrence of an ATNR following a spontaneous head turning in both AGA and SGA infants was rare. From our results it may be concluded that the ATNR is rare in full-term AGA and SGA newborns. Furthermore, this study demonstrates that head position is not a major factor influencing quantitative aspects of spontaneous motor behaviour. The results are of clinical importance as they imply that in the examination of the neurological condition of the full-term newborn infant by means of observation of spontaneous posture and motility, head position is not of major importance.

Electroceramic Thin Films Part II: Device Applications

Ferroelectric thin films have experienced tremendous development in recent years due to the advent of sophisticated film-synthesis techniques and an increase in the understanding of the related materials science and integration of films into various novel devices. Major advances in ferroelectric thin-film synthesis and characterization were addressed last month in the June MRS Bulletin. This volume is dedicated to selective device issues and applications.Ferroelectric materials can be used to fabricate capacitors for integration into nonvolatile ferroelectric random-access memories (NVFRAMs) and as high di-electric layers for capacitors with high capacitance for manufacturing planar dynamic random-access memories (DRAMs). Ceramic conductors can be applied to ohmic, voltage-dependent, and thermally sensitive resistors; fast-ion conductors; and humidity and gas sensors. Piezoelectricity is being exploited in micromachines such as accelerometers, displacement transducers, and actuators such as those required for inkjet printers, for video-recording head positioning, and for micromachining. Pyroelectricity can be utilized in the fabrication of high-sensitivity room-temperature infrared detectors while electro-optic activity can be used in color-filter devices, displays, image-storage systems, and optical switches for integrated optical systems. These applications of electroceramic thin films are only part of a more extensive list.

Accelerated wear characteristics of video heads in a helical scan system

Abrasive Al/sub 2/O/sub 3/ tape is used to accelerate wear of video recording heads in consumer helical scan video recorders. The development of the wear scar is studied as a function of time and the increase in the length of the wear scar is measured using optical microscopy. Changes in longitudinal and transverse head radii are determined as a function of time and the dependence of head wear on head position in the scanner window is studied. The results show that the use of abrasive tape is an efficient tool in the acceleration of wear of helical scan heads.

Imaging of magnetic surfaces by detection of photothermally modulated stray fields

Images from surfaces of ferro- and ferrimagnetic solids are obtained by photothermal modulation of magnetic properties by a focused laser beam and by measuring the surface stray fields using a sensor coil. The lateral resolution is about 10 µm. The method was applied to a sample consisting of cementite plates in an austenite matrix and to monocrystalline ferrite material for video recording heads. Amplitude and phase images are influenced strongly by external magnetic fields. The signal is increasing slightly as a function of the modulation frequency.

Soft-magnetic multilayers for video recording heads

The effect of inducing a uniaxial anisotropy in microcrystalline Fe/FeCrB multilayers by applying a magnetic field during deposition was studied. Not only a reduction of remanent magnetization, but also an increase of permeability (at 10 MHz) are the result. In the hard axis direction a permeability of 6000 is found for a 10 nm/3 nm Fe/FeCrB multilayer. Calculations show that such high permeabilities are interesting for high-density recording heads without ferrite in the core. The domain structure in the head shows the presence of the uniaxial anisotropy. Large unwanted closure domains, in which rotation permeability is low, are present.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effects of the surface configuration of magnetic layers on durability against mechanical stress

This work was carried out in order to improve the durability of metal evaporated tape (ME tape) used in 8mm VCRs. The relationship between the surface configuration of the tape and mechanical stress induced by the impact of a high speed rotating video recording head have been investigated mainly by means of a still-frame life test. The following conclusions have been ascertained. 1) There is an optimum oxygen content level in the Co-Ni magnetic layer in regards to still-frame life. 2) Under low humidity conditions, still-frame life is reduced. 3) Still-frame life is strongly affected by the surface micro roughness (topography) of the magnetic layer, particularly the presence of the steep, high density protrusions which prolong tape life to a great degree.

Monocrystalline high-saturation magnetization ferrites for video recording head application: III. CoII doped MnZn ferrites with large FeII contents

It is shown that substitution of CoII into FeII-rich MnZn ferrites makes it possible to enlarge the FeII content permissible for combined write/read video recording heads. This results in an increase of the saturation magnetization Ms, which is important when high-coercivity magnetic tapes are used. A properly chosen CoII content compensates the magnetocrystalline anisotropy of the ferrites in such a way that the temperature of the maximum in the magnetic permeability μ′ versus temperature curve, caused by anisotropy compensation by FeII, is lowered to the level at which a recording head operates. We report on monocrystalline ferrites with suitable CoII-FeII concentration combinations, showing Ms values of up to 0.660 T and a maximum in μ′(T) at 40°C of 600–700 at 4.5 MHz. We show that with CoII substitutions, the enlargement of the FeII content does not give rise to larger magnetic disaccommodation effects. The present paper is the third in a series of three dealing with FeII-rich ferrites for video recording head application.

Monocrystalline high-saturation magnetization ferrites for video recording head application: I. Zn ferrous ferrites

Monocrystalline Zn ferrous ferrites ZnxFe3-xO4, with x ⩽ 0.4, are considered as candidate materials for video recording heads, to be used for writing on magnetic tapes of high coercivity. The saturation magnetization of these ferrites can be as high as 0.7 T at 20°C. We show that because of the small dimensions of modern video recording heads, the relatively high electrical conductivity of the Zn ferrous ferrites is not an obstacle to their use at video frequencies. Measurements are reported of magnetic and electrical parameters relevant to recording head application. It is shown that some of the magnetic parameters can be influenced positively by CoII additions. The present paper is the first of a series of three dealing with FeII-rich ferrites for video recording head application.

Monocrystalline high-saturation magnetization ferrites for video recording head application: II. MnZn ferrites with large FeII contents

Monocrystalline FeII-rich MnZn ferrites are considered as candidate materials for video recording heads, to be used for both writing and reading when magnetic tapes of high coercivity are applied. It is examined how saturation magnetization and magnetostriction constants vary with chemical composition within relevant areas of the ternary composition diagram MnFe2O4-ZnFe2O4-FeIIO4. From the results and data known for the magnetocrystalline anisotropy a composition is selected which offers a fairly good compromise between high-saturation magnetization and suitable soft magnetic properties. A study is presented of magnetic and electrical properties of monocrystals of this composition, relevant to their use as video recording head materials. The present paper is the second in a series of three dealing with FeII-rich ferrites for video recording head application.

Magnetic permeability of monocrystalline MnZn ferrous ferrite in a simple model video recording head

The influence of stress on the magnetic permeability of monocrystalline Mn-Zn ferrous ferrite in a simple model video recording head is investigated. For that purpose the self-inductance and magnetic loss to be expected for a stress-free head at various temperatures and frequencies are compared with data measured on a real head.

Professional recording of the standard PAL signal

Quadruplex video tape recording was introduced in 1956 by the Ampex Corporation of America and was soon adopted by broadcasters throughout the world. During the subsequent 21 years many improvements have been made, but the same basic format is still used for most high quality broadcasting. Advanced video-recording head design, sophisticated velocity-error compensation, the use of digital techniques and improvements in recording tape have all contributed to the development of modern colour-capable recorders. Electronic editing equipment and cassette machines have been introduced to provide comprehensive production facilities. However, the use of multigeneration recording shows that further improvements in timing stability and a reduction in head banding and moire would be desirable. Furthermore, there is a need to reduce capital and revenue costs. New helical formats can now provide broadcast quality at much reduced cost, and a new quadruplex format offers improved quality with some cost reduction. The broadcaster is faced with a difficult choice that may ultimately be influenced by the advent of digital recording.

A theory of eddy current limited heads

Many video recording heads are fabricated from electrically conductive, magnetic alloys and are operated at frequencies where the skin depth is small compared with head dimensions. We present a novel theory wherein it is assumed that flux flows only in a skin layer which covers all the surfaces of the head. The gap regions are treated as magnetic transmission lines. Computations of the head inductance compare well with experiment. This model is simple enough to be readily applied to the design of other heads made from conductive materials.

Electron mirror measurements of magnetic fields over audio and video heads and tapes

The measurement of magnetic fields over audio and video magnetic recording heads and tapes was achieved with a stroboscopic electron mirror microscope which had some attachments for image scanning and readout of current density distribution at the final screen. The curves obtained were processed on a digital computer. This made it possible to calculate the distribution of magnetic fields at any height over the surface of the specimen. The frequency response curves of audio and video recording heads were measured in the range of 0-10 MHz. The magnetic field distribution of sinusoidal and video recorded signals on the tape was also measured at various heights over the tape.

Pressure sintering of MnZn and NiZn ferrites

Polycrystalline MnZn and NiZn ferrites suitable for recording-head applications have been prepared by pressure sintering (hotpressing). General conditions for pressure sintering and details of the apparatus are described. Also discussed are the effects of grain size and temperature, in the normal range of glass bonding, on the magnetic and physical properties of pressure-sintered MnZn ferrite. It was observed that the strength of the ferrite increased with decreasing grain size in the range studied (15 to 500 μm). An opposite effect was noted for resistance to material wear. Increases in permeability up to 30 percent were obtained by relieving residual machining stresses with anneals in the 500 to 900°C range. Similar increases in strength were observed for low-temperature anneals. However, at temperatures higher than 500°C, the strength was reduced strongly, with the amount of the reduction being dependent upon the surface finish of the ferrite and its geometry. In general, strength was reduced with coarser surface finish and increasing surface-to-volume ratios. Data on material wear and hardness as functions of grain size and composition are presented. Improvement in performance of video recording heads fabricated of pressure-sintered MnZn ferrite as compared to Alfesil and single-crystal MnZn ferrite is also demonstrated.