JPH0233728A - Xerographic type optical memory system - Google Patents

Abstract

PURPOSE: To enable a high speed operation and to reduce power consumption by structuring a memory system so that it is controlled with an optical system and an electronic device without necessitating a mechanical system. CONSTITUTION: A recording medium 12 is provided with electro-photosensitive particles 14 embedded in a thermoplastic layer 16 on a transparent electrically conductive substrate 18. The particles are nonreactive to light the wave-length of which is in excess of 0.48micron. With the surface 20 of the medium 12 to be irradiated by the initial surface charge, a uniform charge is imparted to the entire surface by an electrifying device. With the medium 12 exposed to light having a wave-length less than 0.48micron, the particles 14 lose the surface charge and gain a different charge. Meantime, adjacently to the backing 24 of the medium 12, an eraser adjuster is provided, which heats the selected part of the medium 12; and with an electrifying device passing the surface 20 of that part, a charge with reversed polarity is impressed so that the charge is removed from the particles 14 in the medium 12. With the medium 12 cooled, the initial charge is impressed to the surface of the medium 12, that part is made photosensitive.

Description

[Detailed description of the invention] Suction and exhaust corporation The present invention relates to computer mass storage devices.

Mitsuho-0 Background With the introduction of high-speed digital computers into the commercial and industrial world, it is becoming increasingly important to store large amounts of digital data in a manner that does not significantly impact the operating speed of the computer and is economical. One problem arose with searching and searching. magnetic floppy disk, pigeon disk, magnetic tape, optical compact
Many forms of storage (memory) devices exist, such as disks, each with limitations in storage capacity, operating speed, and cost.

The large capacity primary memory devices used in modern computers, whether mainframes, minicomputers, or microcomputers, are magnetic tapes or magnetic disks. Even in a mainframe computer that uses one bank of hard disks with a diameter of 14 inches, there are 7 such disks, and the memory capacity is about 35
0 megahide. Since 1 hide is 8 pins, the total memory capacity is just under 3 giga hides. This is a significant amount of memory, but the required
- The size and cost of the disc and the equipment required to scan it are also significant. To achieve this storage capacity using a floppy disk, 100
The number of sheets exceeding 0 is required, which is unrealistic.

An optical compact disc known as a CD-ROM is currently being considered and is capable of providing the above-mentioned large storage capacity. It has an inherent disadvantage that once it is erased, it is generally not erasable, that is, it cannot be rewritten. Furthermore, CD-ROMs, like vinyl records, have a platter that must be mechanically rotated so that the appropriate portion of the rotation is read.
) has inherent limitations in terms of accuracy and speed. The problems of aligning the read head and the time required for the inherent mechanical movements slow the read process and increase the chance of errors and malfunctions. Of course, ROM (read-only memory)
This limitation alone is sufficient to render CD-ROMs useless in situations where data must be written to a storage device and a computer is running.

As mentioned above, the speed of write/read operations to the memory must also be considered. For conventional hard disks, the write speed is approximately 20 megahertz. Less expensive floppy disk memories have much slower write speeds.

Even at higher speeds, the operating speeds of today's computers and the expected operating speeds of future generations of computers depend on the speed at which a disk drive's head moves to the location where the desired information is stored or read. In order to make more economical use of the waiting time between reads and reads, the computer's central processing unit (CPU)
:Cer+tralProcessing Unit)
so that there is no need to wait between jobs (tasks) or perform unnecessary shift I.
The speed of data storage and retrieval must be increased.

It is therefore welcome that there is a significant need for a high capacity memory system for digital data storage that avoids these problems and disadvantages and yet provides ever greater storage capacity in a smaller size, lower cost memory system. It should be done. Such memory systems are hard
It would be desirable to be able to perform write and read operations much faster than any current operating speed in the case of disks, yet with a lower bit error rate than anything currently possible. In addition to having other advantages, it is desirable that such a memory system be erasable. The present invention satisfies these needs and, moreover, provides other related advantages.

FIELD OF THE INVENTION The present invention resides in an optical memory system for the storage and retrieval of digital data. The memory system includes a source of a write beam having a first wavelength less than a wavelength threshold and a source of a read beam having a second wavelength greater than the wavelength threshold. . Modulation means are provided for modulating the write beam with a write digital signal containing the digital data to be stored. Means are also provided for forming the write light beam into a write light beam, and means are provided for forming the read light beam into a read light beam.

The invention further provides means for deflecting the writing and reading light beams along a first axis in response to a first control signal; Means are included for deflecting these beams along a second transverse axis that is at an angle with the axis. Lens means are also included for focusing the writing and reading light beams to a focal point by a focal plane.

The memory system includes a stationary medium made of a dry film having electrophotosensitive particles embedded in a thermoplastic layer located on a substantially transparent conductive substrate. The particles are unresponsive to light of wavelengths greater than the threshold wavelength value.

The particles are initially uncharged and the film responds to light upon receiving an initial surface charge.

When uncharged particles are irradiated by a writing light beam, they lose a surface charge and instead gain another charge. Regions of the medium with charged and uncharged particles change the state of the readout light beam.

A passage of the readout light beam through a charged particle corresponds to a recorded information bit of digital data in one binary logic state, and a passage through an uncharged particle corresponds to a recorded information bit of digital data in another binary logic state. corresponds to the recorded information bits.

A fixed mask is positioned substantially on the focal plane of the lens means, parallel to the medium and between the medium and the lens means. The mask is substantially opaque to both the writing and reading light beams, but its apertures are substantially transparent to these beams. These apertures delimit the area of the medium with charged particles and the medium with uncharged particles.

These apertures are individually sized to pass sufficient energy when exposed to the writing light beam for a predetermined period of time, thereby exceeding the sensitivity threshold of the media, and The particles in the corresponding area of the medium are charged, thereby generating charged particles. The apertures are arranged in a plurality of rows aligned with the first axis and positioned toward and adjacent the second axis.

The memory system further includes detection means positioned to be exposed to the readout light beam upon passing through the mask aperture and the medium. The detection means is responsive to the impingement of the read light beam and insensitive to the write light signal and is configured to pass through one of the regions of the medium with charged particles and with uncharged particles. A section 11M of the read light beam corresponding to the passage of one of the regions of the medium is detected. The detection means further generates a read digital data signal containing stored digital data from the medium.

In this way, the binary logic state of the recorded information bits corresponding to one of the regions of the medium is determined.

a first for detecting a write light beam and a read light beam for scanning along a selected one of the rows of apertures in the direction of the first axis at a selected scanning speed; Also included is a means for generating a control signal. This scanning speed for the writing light beam exposes each aperture to the writing light beam for at least a predetermined time interval, thereby charging the particles present in the corresponding area of the medium. selected to generate charged particles.

The optical memory system further includes means for generating a near control signal for selectively deflecting the write and read light beams to selected rows of apertures. This memory
The system further includes means for substantially uniformly charging the surface of the film with an initial charge prior to exposure to the writing light beam.

Other features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

As shown in the drawings as an example of a deaf person, the present invention comprises a digital
It is implemented in an optical memory system for data storage. Memory system 10 utilizes electrophotographic dry film as recording medium 12. As best shown schematically in FIGS. 3 and 4, the medium 12 is
It has submicron electro-photosensitive particles 14 embedded in a thermoplastic layer 16 mounted on a substantially transparent conductive substrate 18. For the media used in the presently preferred embodiment of the invention, particles 14
is 0. It does not react to light with a wavelength longer than 480 microns.

Particles 14 are in an uncharged state at an initial stage,
The medium becomes responsive to light only after receiving an initial surface charge. To apply an initial surface charge to the surface 20 of the medium 12, a Corona charging device 22 extending along the length of the medium is moved laterally across the surface of the medium, as shown in FIG. , giving a uniform charge intensity over the entire surface.

As shown in FIG. 4, 0. When the medium 12 is exposed to light having a wavelength of less than 480 microns, the initially uncharged particles 14 lose their surface charge when exposed to the light and instead acquire another charge. obtain. As explained in more detail below, the light used is a writing light beam modulated with a digital data signal. Thermoplastic layer 14 and conductive substrate 18 are mounted on a transparent glass backing 24 . Medium 12 according to the invention
Further details related to the operation of are discussed below. Remarkably, the media can be repeatedly charged, erased, and recharged without using the film stock as a photographic film, liquid solvent, or heating material, and thus keeping the media in an undeveloped state. It is possible to do so.

The electrophotographic material used in the preferred embodiment as medium 12 is Xerox Dry Microfilm.
(XDM) and are described in more detail in the U,S patent numbers listed below, which are incorporated herein by reference.

Patent No. 3,357,989; 3
．． 542,545: 3,64B, 607; 3.67
L2B2: 3,720,513; 3,816118
; 3,979,210:3.982,936; 3,
9B5,560; 4,013,462; 4,014
,695;4.02B,101;4,040.826
4,055,418 optical memory system 10 further includes a continuous wave monochromatic writing beam light tj26 in the visible light range having a wavelength less than 0.480 microns. Modulator 28 modulates the write beam at approximately 20 megahertz in accordance with a write data input signal on line 30 embodying the digital data stored by storage medium 12. In the preferred embodiment, the writing beam source 26 operates at a wavelength of 0.4 microns. It is a non-coberent mercury lamp. Collimation optics 32 form the modulated writing light beam into a substantially parallel writing light beam that is projected onto a parallel beam splitter for transmission.

The write data input signal is input to the central processing unit (CPU) of the computer by which the memory system 10 operates.
) 35a by the input/output (Ilo) device.

Memory system 10 further includes a source 36 of near-infrared, collimated and polarized readout light having a wavelength greater than 0.480 microns. In the preferred embodiment, the readout beam source is a GaAlAs laser operating at a wavelength of 0.82 microns. As will be more easily understood from the following description, the read light source 36 provides constant illumination and is turned on and off during operation of the memory system, even when the system is in write mode. There is no need for switching. Moreover, since the medium 12 is only sensitive to writing light in the visible spectrum, the near-infrared read light beam will not deflect or modify the stored charge present on the particles 14. It is possible to penetrate the medium without any interference, thereby allowing the stored data to be read repeatedly.

The readout light beam generated by light source 36 is projected through reference optics 38 to form a substantially parallel readout light beam that is projected onto beam splitter 34 . The read light beam and the reflected beam of the transmitted write light beam are projected from the beam splitter along one single optical path for both the write and read light beams.

Beam aperture 40 is positioned to intercept the readout light beam transmitted through the beam splitter.

As described in more detail below, the readout light beam is
The write light beam is used only to read information from the memory medium 12, and the write light beam is used only to write information to the medium.

To accomplish this, the writing light beam has a wavelength greater than the threshold wavelength value of the medium above which the medium 12 becomes photosensitive. In contrast, the read light beam has a subthreshold wavelength, which renders the medium unresponsive to the read light beam.

A horizontal baffle plate 42 exists along a horizontal axis in response to a horizontal baffle drive signal provided by a control circuit indicated generally in FIG. 1 by the reference numeral 44.
It is positioned along the optical path to deflect either the write light beam or the read light beam. As best shown in FIG. 2, it is a solid state device with a bimorphic piezoelectric crystal that is electronically controlled by horizontal baffle drive signals provided by control circuitry 44. The baffle drive signal deforms the bimorph crystal such that the write/read circumferential light beam is incident on the aluminized reflective surface 46 attached to one side of the bimorph crystal. Perform a scan along the horizontal axis at the selected scan rate. In FIG. 2, two rays “A” and “B”
” is schematically shown reflecting off the aluminized surface 46 at times “1” and “2” corresponding to two of the many deflection angles allowed by the deflector 42. . The change in angle between the reflected rays at time "1" and time "2" is shown by the double-headed arrow in both cases of rays "A" and "B".

The writing/reading light beam is horizontally deflected Fi.
, 4.2, there is a vertical deflector 50 having a construction somewhat similar to the horizontal deflector 42, except that the write/read light beam passes through a bimorph crystal. also exists.

Vertical baffle 50 deflects the write/read light beam along a vertical axis that is substantially perpendicular to the horizontal axis in response to a vertical baffle drive signal provided by control circuit 44. let If appropriate drive signals are used for horizontal deflector 42 and vertical deflector 50,
The write/read light beam can be scanned horizontally or vertically across any desired portion of the medium 12.

After the write/read light beam passes through the vertical baffle plate 52, the beam passes through a horizontal cylindrical lens 52 and a horizontal cylindrical lens 54, which together condition and further focus the light beams through a focal plane. Pass in order.

The fixed mask 56 is substantially on the focal plane and on the media 1
located in parallel on the two sides.

Mask 56 is adhered to one side of media 12 facing towards lenses 52 and 54. This mask is shown in Figure 5.
As best shown in FIG. is opaque. In the presently preferred embodiment of the invention, aperture 58 is
They are 1 micron in diameter (i.e., 1.0 x 10-' meters), and their center points are 2 microns apart from each other, both along the rows and between the rows. With this arrangement, 25
x106 apertures, 5,000 rows x5. O
The dimension with the aperture in the O0 row is 1. It is possible to locate it in the matrix of Ocll+. In this way, and with a relatively small 4.3 inch x 4.
By using a 3 inch square mask 56 over a similarly sized block of media 12 equal to an area of about 119 cd, it is possible to have 3.0 x 10 9 apertures. As will be discussed in more detail below, each aperture 58 delimits a correspondingly sized region of the medium 12 that may have charged or uncharged particles. The charged state and uncharged state of particles are determined by whether the information stored in the region is "1" or "0" in binary notation.
” and this state of the particle can be detected using a readout light beam.

It is capable of storing 3.0 gigahertz of information on a 4.3 inch x 4.3 inch square medium 12, which is approximately the storage capacity of seven conventional 14 inch hard disks. It means that there is.

Focal plane mask 56 is fabricated using a diaphragm material developed using a light exposure technique to form the opaque portions of the mask and the transparent apertures 58. Other suitable techniques may be used to manufacture this mask.

By using the focal plane mask 56, problems with conventional focusing are solved because the aperture 58 acts as an aperture diaphragm, so that there are no diffraction problems. In the presently preferred embodiment of the invention, the write and read beams have a diameter of 0.4 microns and 0.4 microns, respectively. .82 microns, and the apertures have a wavelength of 1.0 microns.It should be noted that by decreasing the diameter of the apertures or the spacing between apertures, or both, the concentration of the medium 12 can be increased. It means getting.

The film medium 12 used in the presently preferred embodiment of the invention has sufficient resolution through the use of a focal plane mask 56, and further increases information storage density without diffraction problems. is possible.

The apertures 58 of the mask 56 either have not been irradiated with the writing light beam and thus retain their initial uncharged state, or have particles that have been irradiated with the writing light beam, and thus the media surface 20. This defines the area of the medium 12 that loses a second surface charge and gains another charge in its place. Regions of the medium 12 with charged particles and regions with uncharged particles change the propagation phase velocity of the orthogonal elements of the readout light beam, so that as the beam passes through the region, the resulting electric field and This results in a rotation of the angle of the magnetic field.

When the electric and magnetic fields pass through a region with charged particles, they rotate by a first degree of rotation, and when they pass through a region with uncharged particles, they rotate by a second degree of rotation, the difference from the first degree being detectable. only rotates.

When passing through a region with uncharged particles 14, the electric and magnetic fields of the readout light beam rotate as a result of the initial charge placed on the surface 20 of the medium 12.

When the readout light beam passes through a region with charged particles, it rotates further. The reason for this is that the area with charged particles is 120
It can have a voltage of V, but the voltage of the initial surface charge is 100V.
This is because it can be. This higher voltage value is due to the additional charge imparted by the photons that impinge on the photosensitive particle and add additional energy to it. In the presently preferred embodiment of the invention, a region containing charged particles and through which the electric and magnetic fields through which the readout light beam rotates by a first degree of rotation corresponds to a binary "1" and contains uncharged particles. As a result, the area of smaller rotation degree is 2
Corresponds to base “0”.

impinging an area of the medium 12 with a specific amount of light energy;
Its sensitivity threshold is exceeded and thereby the thermoplastic layer 1
6 (see FIGS. 3 and 4), each of the apertures 58 in the mask 56 must be such that the photosensitive particles 14 embedded therein acquire a charge, and each of the apertures 58 in the mask 56 must be such that the writing light beam passes through them. It must have an opening of the minimum dimensions relevant to the time of encroaching the medium.

The dimensions of this aperture must be of sufficient value to pass sufficient energy when exposed to the writing light beam to exceed the sensitivity threshold of the medium. Of course, while the writing light beam is invading the medium, the control circuit 4
4 and is determined by the scanning speed of the beam, which is discussed in more detail below.

Aperture 58 irradiated with the readout light beam
The readout light beam passes through the medium and then, in a preferred embodiment of the present invention, passes through an associated photodetector circuit, designated by the reference numeral 63. The readout light beam passes through a spherical lens 60 that focuses the readout light beam onto a photodetector 62, which is a photodetector photodiode. Photodetector 62 generates an indicator signal indicative of detection of the readout light beam and provides the indicator signal to pulse condition comparator 66 . The photodiode responds to the incidence of the readout light beam, but does not respond to light at the wavelength of the write optical signal. The light 62 and the circuit 63 are
It is a conventional 0PIC photodetector, such as Model No. 15OO6 manufactured by Sharp, which integrates a photodetector emerent and peripheral circuitry on one chip.

Senarmont's polarization compensator 64 is connected to the photodetector 62.
and the lens 60, and also on the optical path of the readout light beam. Compensator 64 includes associated conventional circuitry (not shown). The electric and magnetic fields of the readout light beam are determined by measuring the intensity of the readout light beam against a predetermined reference value after passing through one of the regions of the medium 12 defined by one of the apertures 58. Detect and measure rotation angle. The intensity of the readout light beam is
The well-known Malus' law
w) varies as a function of the angle of rotation of the electric and magnetic field vectors. This standard value is
It is based on the rotation that the readout light beam experiences when passing through a region of uncharged particles 14. The compensator 64 is based on the perceived phase difference between the readout light beam passing through the charged and uncharged areas, but is
5 to generate a data display signal.

This data indication signal effectively modulates the amplitude of the indicator signal from photodetector 62 and further causes the recorded information bits of the digital data in which the rotation is stored to be in a binary logic state of "0". If an indication is detected, the indicator signal is attenuated. Electronic signal amplitude comparator 66 monitors the indicator signal and further determines the indicator signal by comparing the indicator signal to a predetermined amplitude threshold level.
i.e., the detected rotation angle corresponding to the passage of the readout light beam through the region of charged particles exceeds the predetermined threshold, indicating that the recorded information bit is "1". Generates a binary output "1" only when The output of comparator 66 is a read digital data signal containing the digital data stored in the area of the medium 2 scanned by the read light beam.

This read digital data signal is provided to the computer's I10 device 35a.

To provide an initial charge on the surface 20 of the medium 12, Cor
otron 68 extends over the entire vertical length of the medium,
It is movable across the horizontal width of the medium.

The Corontron 68 (like the device 22 described in connection with FIG. 3) is a Corona charging device that sprays electrons uniformly onto the surface 20 of the medium 18, thereby providing a uniform charge strength over the entire surface. It has a rear baffle plate. Once the media is provided with an initial charge prior to any exposure with the write light beam, the Corontron 68 is moved out of the optical path of the write/eject light beam.

The medium 12 used in the present invention is sensitive to temperatures above normal ambient temperatures, and the memory system 10 includes a heatable device located adjacent to the glass backing 24 of the medium 12. An erase regulator 70, which is a shoe, is included. The extinction regulator heats a selected correspondingly sized portion of the medium 12 to a sufficiently high temperature such that charged particles present in the corresponding portion of the medium are exposed to an electric field of opposite polarity. When it is hit, it imparts that charge and returns to its uncharged state. Because glass is used as the backing 24 (see FIGS. 3 and 4), heat is primarily transferred transversely through this glass, but not laterally, thereby causing adjacent media The heated parts are separated so that they do not get heated.

Currently, erasure regulators are configured to erase corresponding portions of media 12 by 7
selectively heated l c to heat above 0°C
This is the foot of TA. At 70°C, media 12 is erased in about 5 seconds, and as the temperature increases somewhat, the erase process is completed more quickly. As a practical matter, after the medium has been heated, Coront
A ron charging device 68 is passed across the surface 20 of the medium corresponding to the heated portion and a charge of opposite polarity is applied to it. By doing this, medium 1
2. Efficiently removes charge from the particles present in that portion of 2.

Once the media has cooled sufficiently, the polarity of Corontron 68 is returned to the polarity required to apply an initial charge, and an initial charge is applied to the surface of the erased portion of media 12, photosensitizing the charge on this portion. Make it. The now erased portion of the medium stores data based on the writing light beam impinging on the medium and the photosensitive particles that have been stripped of their original charge and are being re-charged by the writing light beam's impingement. I am in a position to do so. Unless erased, the photosensitive particles 14 will retain their charge and, when charged to a certain degree, will remain in the medium 1 without any physical deformation of the medium.
A charged field is provided in one area of 2.

This charge is retained by the charged particles for an extended period of time, and there is no need to maintain any power to the system.

By using an erase conditioner 70 with an area smaller than the total surface area of the medium 12, the medium can have several regions of charged particles corresponding to the apertures of the blocks simultaneously erased by the erase conditioner 70. It is possible to divide the tree into blocks of . In a preferred embodiment, erasure regulator 70 is capable of selectively moving the periphery of media 12 for erasure purposes;
Furthermore, when it is not being used to heat the medium, it can be used for writing/
It is a rectangular heatable pad that can also be moved outside the readout light beam.

As previously discussed, control circuit 44 provides horizontal deflector drive signals to baffle plates 42 and 50 to control horizontal and vertical scanning of the write/read light beam on media 12''. and vertical deflector drive signals. The control circuit 44 includes a synchronous controller 72 that controls the overall timing and operation of the controller circuit.
is included. This synchronous controller 72 provides control signals for two 20 MHz clocks 74 and 76, each clocking a horizontal scanning circuit and a vertical scanning circuit. Clocks 74 and 76 each output to their respective horizontal scan counter 78 or vertical scan counter 80.

Each of these scan counters counts from 1 to 5,000 corresponding to the 5,000 apertures 58 present in each row and each column of the focal plane mask 56.

The individual outputs of scan counters 78 and 80 are each provided to a corresponding horizontal D/A converter 82 or vertical D/A converter 84. The D/A converter converts the output of the digital counter given by the output of the scanning counter into
It is converted into an analog voltage signal that serves as a deflector drive signal applied to a corresponding one of horizontal baffle plate 42 and vertical baffle plate 50. This analog voltage signal is used to deform the bimorph piezoelectric crystal portion of the baffle plate to scan the beam in either the horizontal or vertical direction as desired. In this manner, under the control of synchronization controller 72, memory system 10 can be operated to automatically scan media 12.

In a conventional manner, the operation of scanning is manually performed in the horizontal and vertical directions by a horizontal manual scanning circuit 86 and a vertical manual scanning circuit 88, which respond to manual input by the user of a particular information address to which the optical memory performs write/read operations. It is also possible to control. Manual scan circuits 86 and 88 individually provide corresponding D/A signals as provided by scan counters 78 and 80 via the automatic scan mode.
A digital signal is provided to a converter 82 or 84. Here, conventional scanning techniques are used to perform a horizontal scan of a row of apertures from left to right or an incremental scan of a row of apertures from left to right and then right to left. It should be understood that it can be used to control scanning. Of course, the media could be scanned vertically by columns rather than by rows.

Although the memory system 10 has been described and illustrated with a beam splitter that directs the write and read light beams along one single optical path through 1 cent horizontal and vertical baffles, the read function and Since the writing function is performed by light of different wavelengths, an optical system with separate horizontal and vertical baffles for the respective write and read light beams may be utilized. In this way, write and read functions can occur simultaneously. To that end, a scan control circuit would be provided for each of the sets of horizontal and vertical baffles.

It should be noted here that in the case of the memory system 10 according to the present invention, the system operates purely optically without requiring any mechanical movement, with the exception of a slight movement generated by the piezoelectric crystal baffle. controlled by systems and electronic devices.

In such systems, there are no mechanical heads that must be moved, and the information storage medium 12 is stationary. The media does not need to be moved by rotation or the like (in addition, the read/write heads do not need to be moved to align with the tracks or sectors being read or written).
Since there is no need to physically move the fJ medium,
The present invention provides a system capable of operating at extremely high speeds, limited only by the speed of the required electronics and optics. Physically, such speeds are significantly faster than any system using mechanical parts. 20
Write speeds of megahertz and read speeds of 3 to 5 gigahertz are also possible. This improves the access times required by traditional magnetic hard disks by thousands of times, while providing the same storage capacity as using many large hard disks. Another advantage of the present invention is that it has a significantly improved bit error rate over that possible with magnetic hard disks, and has minimal power consumption.

As already noted, memory system 1 according to the invention
In the case of 0, the writing light beam and the reading light beam are
Operating at two different frequencies that do not interfere with each other's operation, and thus with appropriate control circuitry, the memory system is capable of writing to medium 12 and reading from the same medium at the same time. This consideration inherently increases the operating speed of the memory system, further increasing operating efficiency and speed significantly. Coupled with the fact that no moving parts are used in the memory system, the operating speed of this system is significantly increased over any currently available system.

Although particular embodiments of the invention have been described herein by way of example, it will be appreciated that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

[Brief explanation of the drawing]

1 is a schematic diagram of an optical memory system embodying the present invention; FIG. 2 is a schematic diagram of a beam deflector used in the memory system of FIG. 1; and FIG. FIG. 4 is an enlarged partial schematic diagram showing a storage medium used in the memory system of FIG. 1; FIG. 4 shows a portion of the memory medium charged to the initial surface charge of FIG. FIG. 5 is a schematic diagram illustrating how the surface charge of is transferred to photosensitive particles embedded in the medium in the memory system of FIG. 1 showing an aperture mask adhered to the medium. 2 is an enlarged partial schematic diagram of the storage medium used; FIG. 1963.10.18 Month/Day

Claims (1)

Claims: 1. An optical memory system for storing and retrieving digital data, comprising: a source of a write beam having a wavelength less than 0.480 microns; a write digital signal comprising digital data to be stored; means for performing amplitude modulation of the writing light beam; first lens means for forming the writing light beam into a substantially parallel writing light beam; a light source for a readout beam having; a second lens means for forming the readout beam into a substantially parallel readout beam; and a second lens means for forming the write light beam and the readout beam into one single optical path. means for outputting the write/read light beam along the optical path; first means on the optical path for deflecting the write/read optical beam in response to a first control signal, typically along a first axis transverse to the optical path; and; deflecting the write/read light beam generally across the optical path and along a second axis substantially orthogonal to the first axis in response to a second control signal. second means on said optical path; third lens means on said optical path for focusing said write/read light beam through a focal plane; and third lens means mounted on a substantially transparent conductive substrate. A static media made from a dry film with submicron electrophotosensitive particles embedded in a thermoplastic layer that is insensitive to light at wavelengths greater than 0.480 microns. wherein the particles are initially uncharged and the film is responsive to light after receiving an initial surface charge, and the uncharged particles are irradiated with the writing light beam. Then, the surface charge is lost and another charge is acquired, and the rotation angles of the electric and magnetic fields of the readout light beam differ depending on the region containing the charged particles and the uncharged particles, and furthermore, the electric and magnetic fields are ,
passing through the region with the charged particles at a first degree of rotation;
Further, when passing through the region having the uncharged particles, the particles rotate at a second degree of rotation that is detectably different from the first degree of rotation, and the first degree of rotation is detected to be different from the first degree of rotation in one binary logic state. corresponds to a recorded information bit of said digital data, and a second degree of rotation corresponds to a recorded information bit of said digital data in the other binary logic state; a fixed mask located generally on the focal plane of the third lens means and further placed parallel to the medium between the medium and the third lens means, the mask comprising a plurality of opaque to the write and read light beams by a partially transparent aperture, the aperture delimits the region of the medium by the charged and uncharged particles; have dimensions that pass sufficient energy when exposed to exceed a sensitivity threshold of the medium and further charge the particles present in the corresponding region of the medium to generate charged particles; The aperture has its own plurality of rows and columns.
said fixed mask arranged in a matrix with said rows aligned along said first axis and said columns aligned along said second axis; positioned to be exposed to the read light beam after passing through the aperture and the medium, responsive to the impingement of the read light beam and unresponsive to the impingement of the write light beam; a light detection means for detecting the presence of said readout light beam and further generating an indicator signal indicative of detection of said readout light beam; said readout light after passing through said mask aperture and said medium; phase detection means positioned to be exposed to the beam, the medium being oriented such that the phase velocity of propagation of the light beam is changed so that the electric and magnetic field vectors of the readout beam are changed; rotation, whereby a rotation angle is detected and a data indication signal is generated indicating to which of the first and second degrees of rotation the detected rotation angle corresponds, thereby said phase detection means such that a binary theoretical state of a recorded information bit corresponding to any one of said areas of the medium is determined; and said data indication signal for inhibiting said indicator signal. responsive control means; fourth lens means positioned between the medium and the light detection means for focusing the readout light beam onto the light detection means and the phase detection means; means for receiving said indicator signal from said medium, comparing said indicator signal to a predetermined threshold level, and further generating a read digital data signal comprising stored digital data being read from said medium. a comparator; a selected one from said column of said apertures in the direction of said first axis at a selected scanning speed by deflecting said write/read light beam;
a first means for generating said first control signal to scan along said two columns, said speed of said selective scanning of said writing light beam individually moving said apertures at said predetermined times; said first means being of a value sufficient to expose said writing light beam to charge said particles in a corresponding area of said medium; said writing/reading light beam; a second means for generating said second control signal to selectively expose said selected rows of said apertures; prior to exposing to said writing light beam; charging means for substantially uniformly charging the surface of the film with the initial charge and for exposing at least a portion of the film to a field of polarity opposite to that of the initial charge for erasing; ; being movable to a position adjacent to said medium and heating a selected portion of said medium sufficiently above ambient temperature such that said charged particles present in said selected portion of said medium are transferred to said charging means; When exposed to a field of opposite polarity, it releases its charge and returns to an uncharged state,
The optical memory system as described above further comprises erasing means movable outside the write/read light beam when not being used for heating the medium. 2. the first means and second means for deflecting the write/read light beam together select an angle of the write/read light beam along the first axis and the second axis; 2. The memory system of claim 1, wherein the memory system is an electrically controlled piezoelectric crystal, each deformable in response to the first and second control signals to orient the memory. 3. The memory system of claim 1, wherein the wavelength of the light source of the write light beam is about 0.4 microns and the wavelength of the light source of the read light beam is about 0.82 microns. 4. The memory system of claim 1, wherein the mask apertures have a width of about 1 micron or less and a spacing between adjacent ones of about 1 micron or less. 5. Each of said first means and second means for generating first and second control signals includes said first and second means operated by a clock and for detecting said write/read light beam. The means includes a scanning counter for outputting a count signal to a D/A converter for generating first and second control signals indicative of a desired value of deflection of the write/read light beam. The memory system of claim 1. 6. The memory system according to claim 5, wherein the clocks of the first means and second means for generating the scan counter are controlled by a Synch controller so as to operate synchronously. 7. The memory system according to claim 5, further comprising manual input means for selecting the count signal and applying it to the D/A converter. 8. The memory system of claim 1, wherein said medium is mounted on a planar which is a substantially transparent glass backing with said medium side and toward said fourth lens means. 9. Claim 8, characterized in that the erasing means is an electrically heatable pad having dimensions smaller than the dimensions of the medium for heating selected parts of the erasing means. memory system. 10. The mask of claim 1, wherein the mask is formed from a photographic sheet developed to form the aperture, which is transparent to the write/read light beam, as a generally circular section. Memory system as described. 11. The memory system of claim 1, wherein the mask is glued onto the surface of the medium in the direction of the third lens means. 12. The memory system of claim 1, wherein the phase detector includes a Senarmont compensator. 13. The memory system according to claim 1, wherein the light detection means includes a photodiode. 14. An optical memory system for storage and retrieval of digital data, comprising: a source of a write beam having a first wavelength less than a wavelength threshold; and a write digital signal comprising digital data to be stored. modulating means for modulating said writing light beam; means for forming said writing light beam into a writing light beam; a light source for a read light beam having a second wavelength greater than said wavelength threshold; means for forming the read light beam into a read light beam; means for deflecting the write light beam and the read light beam along a first axis in response to the first control signal; means for deflecting the write and read light beams along a second transverse axis that is at an angle with the first axis in response to a control signal; a submicron electrophotosensitive dry film embedded in a thermoplastic layer formed on a substantially transparent and electrically conductive substrate; a stationary medium produced by a method in which the particles are unresponsive to light having a wavelength greater than the threshold wavelength value, and the particles are initially uncharged;
and after receiving the initial surface charge, the film is responsive to light, and the uncharged particles, when irradiated by the writing light beam, instead of losing the surface charge, acquire another charge, and the The medium with charged particles and the region with uncharged particles change the conditioning of the readout light beam such that passage through the charged particles records the digital data in one binary logic state. said stationary medium corresponding to a recorded information bit of said digital data whose passage through said uncharged particle corresponds to a recorded information bit of said digital data in another binary logic state; a fixed mask located parallel to the medium and between the medium and the lens means, the mask itself being directed to the writing and reading light beams; is substantially opaque, but its plurality of apertures are substantially transparent to the write and read light beams, and the apertures allow the regions of charged and uncharged particles to be separated from each other. Although limited in scope, the apertures individually have dimensions that accept sufficient energy when exposed to the writing light beam for a predetermined time to exceed the sensitivity threshold of the medium, thereby generating charged particles, said apertures being arranged in a plurality of rows aligned with said first axis and positioned adjacent thereto by one row in the direction of said second axis; a fixed mask; conditioning of the writing beam corresponding to the passage of the medium with the charged particles through one of the regions and the passage of the medium with the uncharged particles through one of the regions; and generating a read digital data signal containing stored digital data read from said medium, thereby detecting two of the recorded information bits corresponding to one of said areas of said medium. positioned to be exposed to the readout light beam after passing through the mask aperture and the medium and responsive to the incidence of the readout light beam for the purpose of determining a value logic state; is insensitive to said writing light beam; scanning at a selected speed along a selected one of said rows of said apertures in the direction of a first axis; means for generating a first control signal for deflecting a write light beam and a read light beam to cause the selected scanning speed of the write light beam to generate charged particles; , further comprising: said means being of a value such that said apertures are individually exposed to said writing light beam for at least a predetermined time to charge said particles in a corresponding region of said medium; means for generating the second control signal for selectively deflecting the write light beam and the read light beam to the selected row of the aperture; and means for substantially uniformly charging the surface of the film with an electric charge. 15. The memory system of claim 14, wherein the width of the aperture is greater than both the first and second wavelengths. 16. The memory system of claim 15, wherein the wavelength threshold is about 0.480 microns and the aperture width is about 1 micron or less. 17. The detection means detects a rotation angle of an electric or magnetic field of the reading light beam after passing through one of the regions of the medium, and the rotation angle relative to a threshold value is
15. The memory system of claim 14, wherein the binary logic state of the recorded information bit is indicated as 1 or 0. 18. A computer system that handles the storage and retrieval of digital data, with a central processing unit (CPU) that handles the digital data and master control of the computer system; I/O (input/output) means for inputting and outputting digital data to and from the central processing unit and further generating a write digital data signal containing the digital data to be stored; a light source for a writing beam having a small first wavelength; modulating means for modulating the writing beam by the write data digital signal provided by the I/O means; means for shaping the readout light beam into a readout light beam; a light source for a readout light beam having a second wavelength greater than the threshold wavelength value; means for shaping the readout light beam into a readout light beam; means responsive to deflecting the write light beam and the read light beam along a first transverse axis; means for deflecting the writing and reading light beams along a second transverse axis; lens means for focusing the writing and reading light beams through a focal plane to a focal point; is a static medium produced by a dry film with submicron electrophotosensitive particles embedded in a thermoplastic layer mounted on a transparent, electrically conductive substrate, said particles having said threshold wavelength. the particles are initially uncharged and the film is reactive to light after receiving an initial surface charge, and the uncharged particles The area of the medium with the charged particles and the area of the medium with the uncharged particles loses the surface charge and gains another charge when irradiated by the write light beam, and the area of the medium with the charged particles and the area of the medium with the uncharged particles are in the state of the read light beam. changing the modulation such that passing the charged particle corresponds to the recorded information bit of the digital data being in one binary logic state and passing the uncharged particle corresponds to the other binary logic state. said computer system corresponding to recorded information bits of said digital data in a logic state; substantially on said focal plane and further between said medium, said lens and said lens means; a fixed mask positioned in parallel with the media, the mask being substantially opaque to the write and read light beams and having a plurality of apertures opaque to the write and read light beams; is substantially transparent, the apertures defining a region of the medium with the charged particles and a region of the medium with the uncharged particles, each of the apertures comprising:
having dimensions that permit the passage of sufficient energy when exposed to the writing light beam for a predetermined time to exceed the sensitivity threshold of the medium and to further increase the energy in the corresponding area of the medium. charging the particles to generate charged particles, the particles being in a plurality of rows aligned with the first axis and adjacent by one row thereto in the direction of the second axis; the fixed mask being positioned; positioned to be exposed by the readout light beam after passing through the aperture and the medium;
It is responsive to the impingement of the read light beam and non-reactive to the write light beam, thereby inhibiting the passage of the medium with the charged particles into the region and the uncharged particles. detecting the conditioning of the readout light beam in response to passage within the region of the medium having a readout digital signal to the I/O means containing stored digital data read from the medium; detection means for generating a data signal, thereby determining a binary logic state of a recorded information bit corresponding to one of said areas of said medium; and said first axis at a selected scanning rate. means for generating a first control signal for deflecting the writing light beam and the reading light beam to scan along a selected one of the rows of the apertures in the direction of the writing direction; The selected scanning speed for the optical beam is
exposing each of the apertures to the writing light beam for at least a predetermined time to a value sufficient to charge the particles present in the corresponding area of the medium to generate charged particles; means for generating said second control signal for selectively deflecting said write/read light beam to said selected row of said aperture; and means for substantially uniformly charging the surface of the film with the initial charge prior to charging the film.