JPS586925B2 - optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an apparatus for optical scanning in response to control signals and utilizing such an optical scanning apparatus for recording and reproducing signals, such as acoustic signals. Regarding the equipment that is used.

Certain ferromagnetic materials
mate-reals) and ferric magnetic materials (ferrim
easy axis magnetization in a direction perpendicular to the plane in a single crystal plate or film of agnetic mate-reals
n) having a reverse cylindrical magnetic domain (reverse
d cylindrical magnetic do
main) is a bubble domain (bubble dom)
ain), also known as Bobeck U.S. Patent No. 3,
460,104 and 3,470,546 and U.S. Pat. No. 3,460,116 to Obeck et al. in conjunction with logic elements such as shift registers.

Shaped trajectories including T-par trajectories and "angelfish" shaped trajectories were employed to discretely move the bubble domain in response to control signals.

The Faraday effect was used to visually observe the movement of domains along such trajectories.

The present invention provides an optical scanning device comprising: (i) an optically transparent magnetic plate capable of supporting a moving inverted cylindrical magnetic domain; and (ii) a bias magnetic field applied to the plate to maintain the inverted cylindrical domain. (iii) magnetic overlay means forming at least one continuous trajectory of uniform width in the plate over which light can bend; and (iv) each of the overlays. (V) means for generating inverted cylindrical magnetic domains and causing them to move uniformly and continuously along the trajectory; (vi) means for passing a polarized beam through the plate; and (vii) light passing through the inverted cylindrical domain and light passing through the pond portion of the plate. and analyzer means for identifying.

In one embodiment, there is a series of tracks formed by a pair of parallel, magnetically soft, uniaxial overlay films.

The overlay has a magnetizable axis along its path, and each pair is joined at the start of the trajectory to form a common domain nucleation field.

The overlay is first magnetized such that the polarity in the nucleation field is opposite to the polarity at the proximal end of the inverted cylindrical domain injected below the nucleation field.

A small transverse magnetic field is applied to counteract the magnetization of the orbit.

When the inverted cylindrical domains are injected below the nucleation field, the magnetic field of the inverted cylindrical domains together with the transverse magnetic field is sufficient to nucleate domain walls in the magnetic overlay film;
This wall moves along the film and splits into two walls aligned in a substantially common straight line within the pair of films forming the track, and this paired wall is exposed to the transverse magnetic field. continues to move to the end of the orbit under the influence of

At the end of each orbit near the nucleation field there is a magnetic retentive field for the inverted cylindrical magnetic domain and an electrical means for dividing the inverted cylindrical domain in the retentive field. One of the domains is injected below the nucleation field, and the second inverted cylindrical domain is sequentially transferred to the next holding field.

means for detecting the presence of an inverted cylindrical domain, means for pulsing the electrical means to inject the inverted cylindrical domain into the next trajectory in sequence when such a domain is detected; Located near the end of each track with means for applying a directional magnetic field.

At the end of each scan, a pulse of reverse polarity magnetic field returns the trajectory to its initial state.

In another embodiment of the invention, the tracks are permalloy (
formed by a helix of uniform width made of a flexible or magnetic material such as Permalloy, having means for generating an inverted cylindrical domain at one end, preferably at the center of the helix; ing.

The inverted cylindrical domain is driven in a helical trajectory by a rotating magnetic field.

Optical scanning devices with a helical trajectory can be used to record signals, such as acoustic signals, on a photosensitive plate, preferably a photographic plate, and to reproduce the recording.

(i) The signal is used to modulate the intensity of the polarized beam.

After passing through the analyzer, this polarized beam falls onto a photographic plate, which records the signal as an optical density modulation along the path of light through the moving domain.

(ii) a signal is used to modulate this bias magnetic field while keeping the light intensity constant, so that the area of the bubble domain is modulated by the signal, and the signal moves as an area modulated signal. is recorded along the path of light through the domain.

In either case, in order to reproduce the record (or after development if the photographic plate requires development), place the record in the optical path of the scanning device so that the recorded trajectory coincides with the path of the domain. , the recording may be scanned using a scanning device, and the modulation of the light emanating from the scanning device may be detected.

A preferred method is to employ a parallel light beam through the scanning device and place a field lens system in the path of the light exiting the analyzer so that all light passing through the plate is focused.

A small area detector is placed at the focal point of the field lens system to detect the modulation of the light.

During recording, it is important to place the photosensitive detector ahead of the analyzer in the optical path.

When reproducing a recording, the recording may be placed anywhere in the optical path, but alignment of the recording with the trajectory is most easily achieved by placing the recording where the signal was recorded.

The invention will be better understood by referring to the drawings attached hereto.

Referring to FIG. 1, the figure shows a reversed cylindrical magnetic domain (reversed cylindrical magnetic domain).
magnetic domains).

The material requirements for suitable magnetic materials to support inverted cylindrical magnetic domains are described in Gianola. Smith. Thiele
and IEEE Tra by Van Uitert.
nsact-ions on Magnetics. V
ol. May-5. No. (September 1969), in which many materials are listed.

Suitable magnetic materials exhibit uniaxial anisotropy as a result of their crystal structure, such as the orthorhombic crystal structure found in orthoferrite.

However, bubble domains have been observed in 3D materials such as mixed rare earth garnets, such as gadolinium iron garnets where appropriate uniaxial anisotropy has been developed.

The plate is cut so that the axis of easy magnetization is perpendicular to the plate surface.

Such plates exhibit a strip domain structure in the "unmagnetized" state.

By applying a suitable bias magnetic field perpendicular to the plate, the polarity of the magnetization is preserved therein.

As the field increases further, the diameter of the cylindrical domain decreases, but remains stable up to a certain field value at which this domain collapses.

The ratio of maximum to minimum diameters is approximately 3:1 for plates of any thickness.

The ratio of the bias field when the domains expand into a strip to the value when the domains collapse is 1.6:1 for thin plates and 1:1 for thick plates.

The optimal thickness of the plate, d, for a given minimum domain diameter is where σW is the 180° wall energy and MS is the saturation magnetization, both in units of c. g. The unit is s.

At this thickness, the domain diameter is at its minimum, and at the center of the stable region (1-1.4 times the magnetic field when spread) the bubble diameter is twice the plate thickness.

The bias magnetic field for this state is 1.2πMs.

In addition to the above-mentioned conditions for the presence and stability of inverted cylindrical domains, the plates employed must also have sufficient Faraday rotational capacity (Faraday rotatability).
day rotation).

That is, it is preferable that the light passing through the domain wall be rotated by a minimum of 0.5°, that is, the minimum Faraday rotation ability is 100 100/d°/cm.

This condition is generally satisfied.

Generally, Faraday rotation power is a function of wavelength.

In practical use of the present invention, it is also necessary that the plate transmit an appreciable amount of light.

Generally, a light source illuminates the entire plate with polarized light, but only the light transmitted through the domain passes through the analyzer.

The maximum allowable absorption coefficient α for the material is the domain size,
Depending on the intensity of the illumination and the characteristics of the detector, the following relation holds true:

That is, AD/ASe-adsin-2(2θ)Iin
= Pn where θ = total rotation of the magnetic plate, AD = area of the cylindrical domain, As = total scanning area of the plate, ■ in = total incident power on the plate from the light source, Pn = detector for the desired bandwidth is the noise equivalent optical power.

The minimum required mobility of the cylindrical domains within the plate depends primarily on the domain velocity required by the application and the saturation magnetization of the plate.

The required mobility μ is calculated by the following formula.

μ=v/0.12MS Here, V=domain velocity, Ms=saturation magnetization of the plate.

An example of a material suitable for practicing the invention is mixed garnet Eu
0.09Gd2.32Tb0.59F5.0O12.

For this material, MS≈20 emu/gm.

For a plate 0.025 mm (0.001 in.) thick, the domain diameter is approximately 15
It can vary from μ to 5 μ with a bias magnetic field of 100 oe.

When employed on a helical trajectory as described below, a rotating magnetic field of 5 to 100 e is sufficient to drive the domains.

The Faraday rotation power of this material is 10,0
Wavelengths as low as 00 Å are sufficient to be applicable.

In order to obtain a large Faraday rotation ability with relatively low absorption, it is preferable to use light in the range of 7000 Å,
At this time, the power required for the light source is minimized.

FIG. 1 shows a plate 1 of such material cut perpendicular to its magnetizable axis.

Under the conditions described above, in the presence of a bias magnetic field directed in the direction of magnetizing the plate, the small diameter cylindrical domain 2
is maintained, in which the polarity of magnetization is opposite across the plate.

Such a domain can change the value of the bias field from a value lower than the "run out" value on the plate when the plate is partially or totally unmagnetized, and when this domain is reversed. This occurs by increasing the divergence value to a higher value when it collapses into a cylindrical magnetic domain.

Alternatively, the plate can be fully magnetized and placed in a bias magnetic field suitable for maintaining an inverted cylindrical magnetic domain, for example by a current flowing in small loops in the plane of the plate. arise.

Such domains are generated by applying a partial magnetic field in the opposite direction to the bias field.

The inverted cylindrical domain is IEEETransaction
on Magnetics Vol. May-5, No.
．． 3 (September 1969) p. 544, Bobeck et al., p. It can also be created by dividing an existing inverted cylindrical domain, as shown by Perneski at 544.

If the bias field is not uniform, the inverted cylindrical magnetic domain moves within the plate to minimize its energy.

This property can be achieved by applying a partial magnetic field, i.e. by providing "tracks" of soft magnetic material whose poles are generated by an externally applied magnetic field, and by sending an electric current through a conductor. It has been used to control and operate such domains.

Such trajectories have been employed to generate periodic array motions of inverted cylindrical domains for applications in computer logic devices such as shift registers, ring counters, etc.

Inverted cylindrical domains tend to repel each other at large distances.

However, when the cylindrical domains approach within three diameters, they coalesce into one inverted cylindrical domain.

It has also been discovered that an inverted cylindrical domain can be moved along a substantially uniform trajectory in a uniformly continuous and optically accessible manner while maintaining a substantially constant diameter. .

Thus, the Faraday effect can be exploited so that when illuminating the plate with polarized light, the light passing through the region of the inverted cylindrical domain is isolated.

A useful optical scanning device is thus provided.

In the description of the invention, the term "trajectory" is used to refer to the passage of the inverted cylindrical domains within the magnetic plate, creating a magnetic field gradient that defines the trajectory, and the inverted cylindrical magnetic domains must be distinguished from devices such as soft magnetic overlays, which are employed in combination with magnetic fields to move the magnetic field.

The magnetic thin film overlay must be adjacent to the magnetic plate so that the magnetic plate is exposed to the magnetic field, but need not be on the surface of the magnetic plate.

In most cases, the trajectory is defined by a pair of magnetic overlays with a constant gap on the order of the domain diameter.

If the trajectory thus defined is curved, the magnetic field gradient required to position and move the inverted cylindrical domain is created by the rotating magnetic field.

In the case of a straight trajectory, the required magnetic field gradient is created by the partial magnetic field of the domain walls in the magnetic overlay, which can move along the overlay in response to the magnetic field.

In Figures 2a and 2b, a plate 10 of ferrous or ferric ferromagnetic material capable of supporting inverted cylindrical domains is shown.
is magnetized and placed in a bias magnetic field oriented as shown by HB in Figure 2b, with sufficient strength to support the inverted cylindrical domain.

An overlay 11 made of soft magnetic material is placed on top of the plate 10 or on the plate 1.
It is placed close to 0.

This upper layer consists of parallel strips 11a and 11b of relatively soft magnetic metal such as Permalloy.
, these strips have uniaxial magnetic anisotropy along the length of the strip, and a They are combined into one strip 11c.

In Figures 2a and 2b, the orbit is adjacent to the south pole of the inverted cylindrical magnetic domain.

At the beginning of the process of moving the cylindrical domain along the trajectory,
The magnetic overlay 11 has the strip 11c at the north pole and the strip 11
Each of a and 11b is magnetized into a single domain structure with the south pole.

A small transverse bias magnetic field is applied, opposite the direction of magnetization of the magnetic overlay 11, sufficient to move the domain walls along the strips 11a and 11b, and then the inverted cylindrical domains are overlaid. is injected below the nucleation field 11c.

Means for implanting such inverted cylindrical domains are discussed below.

The magnetic field from the inverted cylindrical domain along with the transverse magnetic field
A nucleation field of 1 nucleates a domain wall in strip 11, and then this domain wall moves under the influence of a transverse magnetic field to form a common straight line in strips 11a and 1lb. It is divided into two domain walls 13a and 13b that are lined up.

The speed at which the domain walls move across the magnetic overlay is controlled by the strength of the transverse magnetic field.

The magnetic field gradient in the domain wall drives the inverted cylindrical domain along a linear trajectory of the light between strips 11a and 11b.

The device shown in Figure 3 has a plurality of upper layers as shown in Figures 2a and 2b, further creating inverted cylindrical domains, and sequentially directing a series of such domains into orbit. It also has the means to do so.

FIG. 3 shows a magnetic body capable of supporting inverted cylindrical magnetic domains and maintained by suitable magnetic means (not shown) in a suitable bias magnetic field to support such domains. The plate 20 has a series of magnetic overlays 21, 22, 23, 24 and 25, consisting of a low coercivity magnetic material, with magnetization oriented along their length. It exhibits uniaxial magnetic anisotropy with an easy axis.

Each of the magnetic overlays 21-25 has the same shape as overlay 11 of FIG. 2, forming a track along which the inverted cylindrical domains can move.

A holding field 26 facing the nucleation field of each overlay 21 to 25
, 27, 28, 29, and 30, which consist of a hard magnetic overlay, such as an iron-cobalt alloy, magnetized to hold the inverted cylindrical domain at the end closer to the nucleation field. There is.

An electrical circuit 31, referred to in the following description as a "fishbone" circuit, is electrically isolated from the holding field and is provided as a thin film having a configuration as shown in FIG.

A small permanent magnet overlay 32 is placed close to the holding field 26 near the end of the fishbone circuit, and a "hairpin"
An electric circuit 33 is provided.

The magnet 32 forms a storage field for inverted cylindrical domains that can be divided by pulses of current flowing through the hairpin loop 33, and one divided inverted cylindrical domain is inserted onto the holding field 26 at the beginning of the scanning motion. , and one inverted cylindrical domain is retained in storage 32 for subsequent segmentation during a new scan.

Adjacent to the ends of the tracks formed by overlays 21-25 are small permanent magnet overlays 34, 35, 36, 37 and 38 which have passed through the tracks formed by overlays 21-25. It has the function of maintaining an inverted cylindrical domain.

A permanent magnet 39 is located near the end of the fishbone circuit as a storage location for the inverted cylindrical domain.

Near the ends of the overlays 21-24, sensing strips 40 of magnetoresistive material, such as permalloy, are placed across the track so that the resistance changes as the inverted cylindrical domain passes underneath.

A similar second sensing strip 41 is provided across the final track formed by the overlay 25.

The method of operation of the device will be better understood by referring to Figures 3a, 3b, 3c and 3d.

The magnetic overlay and part of the electrical circuitry are shown in these figures and the same part numbers as in FIG. 3 are used.

In FIG. 3, inverted cylindrical domain 42 is shown located adjacent the end of magnet 32. In FIG.

When a pulse of current is introduced into circuit 33 creating a partial magnetic field opposing the bias, the domains elongate as shown at 43 in Figure 3a and as shown at 42 and 44 in Figure 3b. It is divided into two inverted cylindrical domains.

Both of these two inverted cylindrical domains are equivalent to the original inverted cylindrical domain.

The effect of the current pulse in circuit 33 is to create a new inverted cylindrical domain 44 in holding field 26 while retaining inverted cylindrical domain 42 in field 32.

In FIG. 3c, the effect of a current pulse in the fishbone circuit 31 on an inverted cylindrical domain such as 44 located on the underside of the holding field 26 is shown.

This inverted cylindrical domain is divided into a domain injected below the nucleation field of the overlay 21 and a second domain 46 .

The effect of the injected inverted cylindrical domain 45 combined with the transverse magnetic field is that it moves along the overlay under the influence of the transverse magnetic field carrying the inverted cylindrical domain 45 and lies on a common straight line as shown in Figure 3d. The purpose is to form a domain wall core in the cladding 21 that is divided into domain walls 48a and 48b that are aligned.

The second inverted cylindrical domain is held on the next holding field 27.

When the inverted cylindrical domain 45 is detected by the detector strip 40, a pulse is applied to the fishbone circuit.

Returning to FIG. 3, detector strip 40 is connected to a current source 49.

As the inverted cylindrical domain passes across the detector strip, a voltage is generated in the current source, which is amplified by amplifier 50 and triggers pulse generator 51 which pulses fishbone circuit 31. used.

The lateral bias magnetic field required to move the domain walls within the magnetic overlays 21-25 is provided by a coil 52 adjacent to the plate, which is supplied with current by a power supply battery 53.
caused by

As the inverted cylindrical domain is injected under the nucleation field of the overlay 25 and moves along the trajectory formed by the overlay 25, it is detected by another detector strip 41 connected to a current source 54. be done.

The voltage generated in current source 54 is amplified by amplifier 55.

The signal from amplifier 55 is sent to pulse generator 56, which applies a current pulse of opposite polarity to field coil 52 to reset magnetic overlays 21-25 to the desired initial state.

Generator 56 is isolated from coil 52 by capacitor 57.

At the same time, the voltage from amplifier 55 is applied to pulse generator 58 which pulses circuit 33, thus creating an inverted cylindrical domain in holding field 26 ready to begin a new cycle.

The pulse from the amplifier 55 is also sent through a time delay circuit 59 to the pulse generator 51 which starts a new cycle. 58
Termination at the end of that cycle by breaking the circuit between X and C.

The inverted cylindrical domain moving along the trajectory is a permanent magnet 34~
38 at the end of each track.

The next moving inverted cylindrical domain merges with the already held domain.

Similarly, the second inverted cylindrical domain generated in the final holding field 30 is held by the magnet 39.

In the next cycle, the holding field 30 is
The second inverted cylindrical domain generated in this merges with the already retained inverted cylindrical domain.

FIG. 4 illustrates the use of a trajectory such as that shown in FIG. 3 in an optical scanning device.

A point light source 70 is placed at the focus of the aiming lens system 71.

The collimated light passes through a polarizer 72 and then through a magnetic plate 73 containing electrical and magnetic circuits that impart the desired motion to the inverted cylindrical magnetic domains.

The bias a-field necessary to support the inverted cylindrical magnetic domain within plate 73 is provided by surrounding solenoids 74.

Coils 75 and 76 (corresponding to coil 52 in FIG. 3) provide the necessary transverse magnetic field.

The light then passes through an analyzer 77 which annihilates light that passes through portions of the plate that do not have inverted cylindrical domains.

The light passing through the cylindrical domain has its plane of polarization rotated with respect to the plane of polarization of the light passing through that portion of the plate, and a portion of it is transmitted by the analyzer.

The light passing through the analyzer is projected by a field lens system 78 onto an optical photodetector 79, such as a photodiode.

An optical transparency 80 carrying information is placed in the path of the collimated light beams between lens systems 71 and 78.

In FIG. 4, this transparent body includes an analyzer 77 and a field lens 78.
It is located between.

However, this position is not absolute and may be between elements 71 and 72, between 72 and 73, or between 73 and 77.
It is also possible to place it in between.

Using the scanning member of FIG.
The rows are scanned sequentially in the same way as a television rask, except that there is no flyback.

Detector 79 thus records the modulation of the light.

The signal indicating the start of each scan line is provided by the detector strip "
Obtained from the “Fishbone” circuit.

The retaining fields 26-30 of the magnetic plates, the part containing the generator 32, the termination member 39, and the nucleation end of the overlay and the retaining field for retaining the inverted cylindrical domain are optically shielded. The inverted cylindrical magnetic domain moving along the trajectory must be the only optical path.

FIG. 5 shows another type of trajectory that may be employed for optical scanning.

In FIG. 5, a plate 80 of magnetic crystal capable of supporting an inverted cylindrical magnetic domain is coated with a constant width of Permallo.
Overlay 8 consisting of pieces of soft magnetic material such as
1 is arranged in an Archimedean spiral.

The Archimedean spiral is determined by the bit a and the track width W in the equation r=θa, where r is the radius from the center of the helix and θ is the total angle scanned from the center.

If w=a, the upper layer becomes a solenoid disk lol
It is necessary that <a.

To avoid overlap when scanning with inverted cylindrical domains of diameter p, the trajectory width must be greater than p/2.

Therefore, p/2<W<a for helical overlays useful in the practice of the present invention.

The helix terminates at or near its center in the form of a permalloy disk 82, which serves as a holding and generating field for the inverted cylindrical domain.

The outer end of the helix terminates in the form of a permalloy disk 83, which likewise serves as a holding field for the inverted cylindrical magnetic domain.

To maintain an inverted cylindrical magnetic domain within the magnetic plate, a bias magnetic field must be applied perpendicular to the plane of the magnetic plate.

Such domains are propagated along magnetic trajectories by the rotating magnetic field in the plane of the magnetic plate.

The inverted cylindrical domains propagate along helical trajectories due to the combined effects of the rotating magnetic field, the trajectory of the permalloy, and the domains themselves.

The rotating magnetic field magnetizes the permalloy, creating a magnetic field gradient in the region of the domain.

When this gradient exists, the domains are pulled toward one edge of the permalloy trajectory.

Because permalloy has a low coercivity and high permeability, its magnetization follows that of a rotating magnetic field that creates a rotational gradient that drives the domains along the trajectory.

By momentarily decreasing the bias field, the size of the "generator" domain at the central permalloy disk 82 is increased and the domain is initiated along this trajectory.

As the transverse magnetic field rotates, this domain tries to remain around this circle and depart along the helix.

This action elongates the inverted cylindrical domain and eventually splits one inverted cylindrical domain into two inverted cylindrical domains.

Before another rotation of the transverse field generates another domain, the DC bias field returns to its original value, and only one domain remains along the helix until this field is reduced again. and propagate.

Therefore, the inverted cylindrical domain moves along a helical trajectory according to the rotation of the transverse magnetic field, and this continues until the inverted cylindrical domain is captured on the permalloy disk 83 at the active end of the trajectory.

Domains emerge one after another, are driven along a helical trajectory, and merge with domains already in the disk 83.

By applying a rotating magnetic field in the plane of the magnetic plate, the trajectory of FIG. 5 is adopted in the apparatus of FIG. 4.

An optical scanning device employing the helical overlay of FIG. 5 can be used to record and reproduce electrical signals, such as acoustic signals.

Such a device is shown in Figures 6a and 6b.

Similar parts on both sides have the same reference numbers.

6a and 6b, the light emitted from the light source 90 is collimated by a lens system 91, and a polarizer 92 and a transparent plate 93 supporting the spiral trajectory in FIG.
and a magnetic plate that can support the inverted cylindrical magnetic domain and is conveniently attached to the plate 93 supporting the orbit, and reaches the analyzer 95.

Analyzer 95 is oriented to block the polarized light transmitted by the portion of the plate that does not have an inverted cylindrical domain.

Light passing through the inverted cylindrical domain on plate 94 is partially transmitted by analyzer 95 to a light spot on plate 96.

This light spot moves in a spiral as the domain moves in a helical trajectory.

A lens system 97 is provided to focus the light passing through the plate 96 onto a photodetector 98.

The bias magnetic field necessary to maintain the inverted cylindrical domain is provided by solenoid 99.

The rotating magnetic field across the magnetic plate is generated by two pairs of coils 100 and 101.
, 102, and 103.

An alternating current having the desired rotational frequency is applied to the coils 100 and 1.
01 and the same alternating current is supplied to coil 102.
and 103 are secondarily supplied.

During recording, plate 96 is an unexposed photographic plate or similar photosensitive detector.

The inverted cylindrical magnetic domain is generated by pulsing the direct current supplied to the lenoid coil 99 and driven along a helical trajectory as described above by the rotating magnetic field supplied by the coils 100, 101, 102 and 103. .

The light transmitted by analyzer 95 to photographic plate 96 is directly modulated by varying the intensity of light source lamp 90 to create a density modulated record on the photographic plate.

For this purpose, it is advantageous to employ as a light source a light-emitting diode that can be modulated at high frequencies.

Instead of modulating the light source, it is also possible to use a constant light source to modulate the diameter of the inverted cylindrical magnetic domain by modulating the bias magnetic field provided by the solenoid 99.

The range of the applied magnetic field is approximately 0.5πMs (here, Ms
is the saturation magnetization of the magnetic plate).

This range provides approximately 300% variation in domain diameter.

If the track width is at least the maximum domain diameter and the light intensity is strong enough to fully expose the photographic record, this method of recording results in area modulated tracks.

The total recording time caused by such a trajectory at constant rotational frequency is πL2/2apf.

where L is the overall diameter of the helical overlay, p is the domain diameter expressed in the same units, a is the pinch of the helix, and f is the upper cutoff frequency of the signal to be recorded.

The minimum required frequency of the rotating magnetic field is pf/πL.

Therefore, most of the recording execution time is occupied by recording in a small diameter range.

By varying the frequency of the rotating magnetic field so that the linear velocity along the trajectory of the inverted cylindrical domain is constant, the recording execution time is improved by a factor of two.

Rotational frequency pf/2π required to generate constant linear velocity pf
r (where r is the radius from the center of the helical overlay of the inverted cylindrical domain at that moment).

After recording, the photographic plate is developed.

To then reproduce this record, the developed photographic plate is placed in the light path in line with the helical trajectory, and the inverted cylindrical domain is placed in orbit under a constant bias magnetic field and illumination system of constant luminous intensity. 6a, amplify the resulting signal, and send it to an acoustic exchanger, such as a loudspeaker.

For example, a mixed garnet Eu0.09Gd2.32Tb0.59 with a thickness of 0.025 mm (0.001 in.)
The bias magnetic field applied to the Fe5.0O12 plate is 85
By varying between ~100 oe, the domain diameter varies between 15μ and 5μ.

This variation is large enough to allow either amplitude modulation or density modulation to obtain maximum recording run time, but density modulation is preferably performed with a bias field of 100 oe.

To create a magnetic field gradient large enough to drive the domain along the guide trajectory, the transversely rotating magnetic field must be between 5 and 1
0oe and the orbital thickness is at least 5000
Must be λ.

An example of a detector is a silicon diffused pin photodiode (EG&G, Inc., No. SGD
-040).

This minimum detectable power requires a light source of at least 10 mW when the analyzer and polarizer are positioned 5° from extinction.

These light sources are common and can be of the light emitting diode or incandescent type.

The foregoing explanation is for the purpose of aiding understanding only and should not be considered limiting.

The invention is not limited to the above description; obvious modifications will be apparent to those skilled in the art.

Embodiments of the present invention are as follows.

1) an optically transparent magnetic plate capable of supporting a moving inverted cylindrical magnetic domain in an optical scanning device; and means for applying a bias magnetic field to the plate to maintain the inverted cylindrical domain; Generates a magnetic gradient in the plate, thereby making the domain
means for uniformly and continuously moving along continuous trajectories in said plate such that light reaches over at least a portion of said domains; means for placing the beam into orbit; means for passing a polarized beam through the plate; and an analyzer for distinguishing between light that has passed through the inverted cylindrical domain and light that has passed through the pond portion of the plate. A device characterized in that it consists of means.

2) In the apparatus of paragraph 1, the analyzer is configured to transmit light that has passed through the inverted cylindrical porcelain domain and to extinguish light that has passed through the pond portion of the plate. Features.

3) The device according to item 2, characterized in that the plate is a crystal of rare earth orthoferrite.

4) The device according to item 2, characterized in that the plate is made of rare earth garnet.

5) The device according to item 2, characterized in that the plate is made of BaFe12O19.

6) A device according to item 2, characterized in that the orbit is formed by an Archimedean spiral of a soft magnetic strip having a uniform width in a rotating magnetic field.

7) A device for signal recording, comprising an optical scanning device according to clause 6, further modulating the polarized beam in response to the signal to be recorded while the inverted cylindrical domain is moving in the orbit. and a photographic plate arranged to record the modulated light passing through the analyzer in the form of an optical density modulation along the path of the light through the inverted cylindrical domain on the orbit. A recording device comprising:

8) A device for recording a signal, comprising an optical scanning device according to paragraph 6, further comprising modulating the area of the inverted cylindrical magnetic domain in response to the signal as the domain moves in the orbit. means for modulating the magnetic field sustaining the domain in order to record the light passing through the analyzer in the form of an area modulation along the path of the light through the orbiting inverted cylindrical domain; 1. A recording device characterized in that it has a photographic plate arranged to do so.

9) A device for reproducing a recorded signal, comprising an optical scanning device according to paragraph 6 and a path of an inverted cylindrical magnetic domain placed in the path of the light exiting the analyzer. having a photographic image consisting of a correspondingly density-modulated helix;
Apparatus characterized in that it comprises a photographic plate placed in the path of light exiting the analyzer, and means for detecting modulation of the light exiting the photographic plate.

10) The apparatus of paragraph 9, comprising means for collimating the polarized beam incident on the magnetic plate and a field lens system arranged to focus the light passing through the photographic plate. , characterized in that the means for detecting modulation of light is located at the focal point of the field lens system.

11) A device for reproducing a recorded signal, comprising an optical scanning device according to paragraph 6 and an area-modulated helix corresponding to the signal, coinciding with the path of an inverted cylindrical magnetic domain moving in a helical trajectory. An apparatus characterized in that it consists of a photographic plate placed in the path of the light exiting the analyzer, having a photographic image consisting of a trajectory, and means for detecting the modulation of the light exiting the photographic plate.

12) The apparatus of paragraph 11, comprising means for collimating the polarized beam incident on the magnetic plate and a field lens system arranged to focus the light passing through the photographic plate. , characterized in that means for detecting modulation of light are located at the focal point of the field lens system.

13) The apparatus of paragraph 2, in which the trajectories include a pair of parallel
formed by a magnetically soft, magnetically uniaxial overlay, the overlay such that the polarity of the nucleation field is opposite to the polarity of the end of the inverted cylindrical domain adjacent to the trajectory; means for magnetizing an inverted cylindrical domain, means for injecting an inverted cylindrical domain under the nucleation field, and applying a magnetic field to the overlay opposing its magnetization state, thereby causing an inverted cylindrical When a domain is injected onto the underside of the nucleation field, a domain wall is created in the nucleation field adjacent to the inverted cylindrical domain and moves through the overlay, along a common straight line. means for applying a magnetic field such that the two domain walls of cause the inverted cylindrical domain to be carried along the trajectory.

14) A plurality of Parallel Term 13 trajectories and a permanent magnetic holding field overlay adjacent to each nucleation field and near the end of each trajectory to detect the presence of inverted cylindrical domains. detection means located at the detection means; and electrical means for dividing the inverted cylindrical domain in each holding field into a first inverted cylindrical domain and a second inverted cylindrical domain in response to a control signal from the detection means. and the retentive field is arranged such that the first inverted cylindrical domain is injected into an adjacent nucleation field, and the second inverted cylindrical domain is sequentially injected into the next retentive field. Apparatus characterized in that it also comprises means for guiding the inverted cylindrical domains, thereby allowing the inverted cylindrical domains to move sequentially through each of said tracks.

15) an optical scanning device comprising: an optically transparent magnetic plate capable of supporting a moving inverted cylindrical magnetic domain; and means for applying a bias magnetic field to the plate to maintain the inverted cylindrical domain; magnetic overlay means forming at least one continuous track of uniform width in the plate, capable of generating at least one continuous track of uniform width within each of the overlays; means for uniformly and continuously moving the upper domain along the trajectory; means for generating inverted cylindrical magnetic domains and placing them on the trajectory; and passing a polarized beam through the plate. and analyzer means for distinguishing between light passing through the inverted cylindrical domain and light passing through the pond portion of the plate.

[Brief explanation of the drawing]

FIG. 1 is a sketch showing the shape of an inverted cylindrical domain in a plate of a ferrous magnetic material or a second magnetic material. Figure 2a is a plan view of a linear magnetic trajectory used to propagate an inverted cylindrical domain. Figure 2b is a side view of the track of Figure 2a. FIG. 3 shows a plurality of parallel tracks on a magnetic plate and means for sequentially inserting inverted cylindrical domains to provide a rask-type scan. Figures 3a and 3b illustrate how to initiate a scan using the trajectory of Figure 3. 3c and 3d illustrate how an inverted cylindrical domain can be inserted onto the trajectory of FIG. 3, resulting in a second domain for subsequent insertion into an adjacent trajectory, and
This figure shows how an inverted cylindrical domain is driven along a trajectory. FIG. 4 shows an optical scanning device utilizing a magnetic plate capable of supporting an inverted cylindrical domain using the trajectory of FIG. FIG. 5 shows a helical trajectory that can be employed in an optical scanning device. 6a is an end view of an optical scanning device utilizing the trajectory of FIG. 5; FIG. Figure 6b is a side view of the apparatus of Figure 6a. 1, 10, 20...Magnetic plate, 2, 12...
...inverted cylindrical domain, 11, 21, 22, 23, 2
4, 25...Magnetic overlay, 31...Fish bone circuit.

Claims (1)

[Claims] 1. An optical scanning device comprising: an optically transparent magnetic plate capable of supporting a moving inverted cylindrical magnetic domain; and for applying a bias magnetic field to the plate to maintain the inverted cylindrical domain. magnetic overlay means forming at least one continuous trajectory of uniform width in the plate in which light can bend, and generating a moving magnetic gradient within each of the overlays. means for thereby uniformly and continuously moving domains on the orbit along the orbit; and means for generating inverted cylindrical magnetic domains and placing them on the orbiter; Apparatus characterized in that it comprises means for passing a polarized beam through a plate and analyzer means for distinguishing between light that has passed through the inverted cylindrical domain and light that has passed through the pond portion of the plate. . 2. A device according to paragraph 1, characterized in that the analyzer is configured to transmit light that has passed through the inverted cylindrical magnetic domain and to extinguish light that has passed through the pond portion of the plate. A device that does this. 3. An apparatus according to paragraph 1, wherein the analyzer is configured to transmit light that has passed through the inverted cylindrical magnetic domain and to extinguish light that has passed through the pond portion of the plate, and is formed by a pair of parallel, magnetically soft, magnetically uniaxial overlays connected at the start of the orbit to form a nucleation field; means for magnetizing the overlay so that the polarity is opposite to the polarity of the end of the inverted cylindrical domain adjacent to the trajectory; and means for injecting the inverted cylindrical domain below the nucleation field. and applying a magnetic field to the overlay opposing its magnetization state, such that when an inverted cylindrical domain is injected below the nucleation field, the domain walls are in the nucleation field. a magnetic field created adjacent to the inverted cylindrical domain and moving through the overlay such that the two domain walls in a common straight line carry the inverted cylindrical domain along the trajectory. A device characterized in that it has a means for applying, and consists of. 4. An apparatus according to paragraph 1, wherein the analyzer is configured to transmit light that has passed through the inverted cylindrical magnetic domain and to extinguish light that has passed through the pond portion of the plate, and wherein the analyzer is configured to transmit light that has passed through the inverted cylindrical magnetic domain and to extinguish light that has passed through the pond portion of the plate, and the trajectory is formed by an Archimedean spiral of a strip of soft magnetic material having a uniform width in a rotating magnetic field. 5. An optical scanning device according to paragraph 1, wherein the analyzer is configured to transmit light that has passed through the inverted cylindrical magnetic domain and to extinguish light that has passed through the pond portion of the plate. , an optical scanning device in which the trajectory is formed by an Archimedean spiral of a strip of soft magnetic material of uniform width in a rotating magnetic field; an inverted cylindrical domain moves in the trajectory; means for modulating said polarized light beam in response to a signal to be recorded during said analysis; Signal recording device, characterized in that it has a photographic plate arranged to record in the form of density modulation. 6. An optical scanning device according to paragraph 1, wherein the analyzer is configured to transmit light that has passed through the inverted cylindrical magnetic domain and to extinguish light that has passed through the curved portion of the plate. , an optical scanning device in which the trajectory is formed by an Archimedean spiral of a strip of soft magnetic material having a uniform width in a rotating magnetic field; the inverted cylindrical magnetic domain moves in the trajectory; means for modulating the magnetic field sustaining the domain in response to the signal to modulate the area of the domain in response to the signal; and means for modulating the magnetic field sustaining the domain in response to the signal; Signal recording device characterized in that it has a photographic plate arranged to record in the form of area modulation along the path of light passing through an inverted cylindrical domain on orbit. 7. An optical scanning device according to paragraph 1, wherein the analyzer is configured to transmit light that has passed through the inverted cylindrical magnetic domain and to extinguish light that has passed through that portion of the plate. , an optical scanning device whose trajectory is formed by an Archimedean spiral of a soft magnetic strip of uniform width in a rotating magnetic field; in the path of light exiting the analyzer; a photographic plate placed in the path of light exiting the analyzer having a photographic image consisting of a density-modulated helix corresponding to a signal corresponding to the path of a placed inverted cylindrical magnetic domain; and the photographic plate. Apparatus for regenerating a recorded signal, characterized in that it comprises means for detecting the modulation of light emanating from the apparatus. 8. An optical scanning device according to paragraph 1, wherein the analyzer is configured to transmit light that has passed through the inverted cylindrical magnetic domain and to extinguish light that has passed through the pond portion of the plate. , an optical scanning device whose trajectory is formed by an Archimedean spiral of a strip of soft magnetic material of uniform width in a rotating magnetic field: an optical scanning device in which an inverted cylindrical magnetic domain moves in a rotating magnetic field. a photographic plate placed in the path of the light exiting the analyzer, having a photographic image consisting of a helical trajectory modulated in area corresponding to the signal, coincident with the path; and detecting the modulation of the light exiting the photographic plate; Apparatus for regenerating a recorded signal, characterized in that it comprises means for regenerating a recorded signal.