JPS58161143A - Apparatus for storing information - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to information storage devices, and more particularly to devices for storing information on optical disks as carrier frequencies with time-varying frequency variations.

Various schemes have been developed in the past for recording signals at video frequencies on disk tape or other media. These systems have utilized optical recording on photosensitive media, electron beam recording on thermoplastic surfaces, and other methods for replayable recording of video information, among others.

Prior art techniques utilize true surfaces, electron beam sensing surfaces, magnetic recording techniques, and techniques similar to the present invention in which a beam of radiant energy causes irreversible changes to the surface and thereby [Reload information 1]
However, it can be roughly classified into two types.

No. 3,234,326, owned by BC Goldmark et al., which teaches recording on a continuous web such as tape or film, or rotation in a helical path No. 33,618'73, owned by Dufryer R. Nojonsson, which teaches the photographic recording of video information into a digital camera.

U.S. Patent No. 328 owned by Duffrew C. Hughes et al.
No. 3,310 describes the recording of information on thermoplastic film surfaces (1), which utilizes an electron beam writing device such as that disclosed in US Pat. No. 3,120,991 (1).

Other systems have also used electron beams to record information on special storage media. One such approach is disclosed in US Pat. No. 3,350,503 owned by TB Bullet. Another approach using an electron beam to a photosensitive medium such as photographic film is disclosed in U.S. Pat. No. 3, owned by R.F.
No. 444,317.

In recent years, other methods for high-density recording have been disclosed, based on removal of material by laser beam bombardment or deposition of material.

These methods are described in the magazine “Electronics”
ctronics) J March 8, 1969 Issue No. 1
It is discussed in detail on page 10. Additionally, ``Laser Thermal Microimage Refuge'' in some detail, by C.O. Carlson and H.D. Ives, 1968 Wescon 14Esc.

N) Meeting (Western Electro
nic 5hoiu-4 = anci Conve++tion);
al Papers), Volume 12, 1968, Section 16/1, Page 1. This author was published on February 23, 1966 by Lee [Science (5c)
) J Vol. 54 No. 3756 No. 155 f
il ~ p. 1551, 1966 7 All Noyoing Computer Fun 7 Allens (Fall J
oing Computer Conference
e) Proceedings of
nss'), pages 711-716, and the Bell Systems Technical Journal (March 1968).
Be1l Systems Technical
Journal), pages 385 and 405.

These publications disclose recording techniques that utilize very thin metal films on a substrate. This thin metal film is heated and melts rapidly, creating tiny spherules within the recorded spot. Since a highly concentrated spot of laser light can be burnt by applying enough heat in a sufficiently short time, a suitably modulated laser beam impinging on a moving surface will A pattern of holes can be generated and the recorded information can be reproduced during "readback".

As pointed out in the Carlson and Ives paper 1 cited above, the size of the recorded spot or hole can be much smaller than the diameter of the imaging laser beam. It is a matter of designing a suitable scheme for recording video frequencies at high resolution by appropriate selection of metal film material, film thickness, laser die per diem and spot power.

In accordance with the present invention, the Carlson and Ives laser thermal microimage recording method is used in conjunction with prior art disk recording to provide a new and useful arrangement and method for recording video information.

This invention relates to storing information on optical discs. In the past, when attempting to store video information on a disk, processing power methods were used to create recorded information directly on the disk from an information signal that varied in amplitude or time. The present invention provides an improved apparatus and method for reliably storing information in the form of a carrier frequency with time-varying frequency changes from the carrier frequency on an optical disk. In the second invention, a light source having a photoresponsive coating covering a substrate of the disk is provided, and a light source interacts with the photoresponsive coating of the optical disk during rotation of the disk. Generates a beam.

An optical device defines an optical path between the light source and a responsive coating on the disk and focuses the light beam onto the coating. A light intensity modulator responsive to the information signal is disposed in the optical path to intensity modulate the light beam. A beam optically focused through an intensity modulator onto a responsive coating on the disk forms an information track emanating from the indicia representing a frequency modulated information signal.

The information signal sequence (modified covering of the disk) contains information in the form of a carrier frequency that changes in frequency as a function of time.

The arrangement of the invention includes a spindle that rotates the disk in a precise circle, and a lead screw that translates the throat at a very constant speed along the radius of the rotating disk. As will be apparent, it is desirable to have the disk drive synchronized or otherwise cooperated with the translational drive to create a helical trajectory of a predetermined pitch. In a preferred embodiment, the spacing between adjacent turns of the helix is 2 μm from center to center. If the diameter of the spot is 1 μm, there is a guard region of 1 μm between the spots of adjacent tracks.

The "write head" in a preferred embodiment is an air bearing-L
It is a microscope objective lens that floats at a constant height above the disk of the microscope. This constant height is necessary because the depth of focus of the objective lens is shallow.

The 40X dry microscope objective was found to be satisfactory in focusing the energy of the laser beam at the disk surface to enable the writing of 1 μm sponts.

A portion of the write beam is sensed by a novel Pockels cell stabilization circuit that helps maintain the average power of the beam for a given level modulation.

An argon ion laser is used as the writing beam. A combination of Pockels cell and Grand Prism 7° modulates the laser beam with video information. In accordance with the present invention, a "read after write" capability is provided to monitor write operations. the second, helium-neon (1-(e-
A Ne ) r readout laser is provided which directs a lower power beam into the write beam path, but at a slight angle to the write beam as it enters the write head. The second angle is approximately 2 μm below the writing spot.
A read beam is selected to illuminate an area on the written trunk.

This trailing beam is reflected from the disk surface back through the write throat and passes through a dichroic mirror where the read beam is inserted into the write path.
) and then retraces its optical path.

The read beam is then directed to a beam splinter and further through a bandpass filter which blocks any write beam that may have followed the same path. The readout beam then impinges on a photodetector to generate a video information signal. The characteristics of this signal are displayed on an oscilloscope or television monitor to indicate peak "record" power, average record power, and whether focus is accurate.

"Write then read 4 information can also be used in error checking schemes, especially when territorial type information is being written. Input video information is The returned information is then compared for "identity" with the delayed input information. If there are too many discrepancies, recheck and realign the device or eliminate the disk.

The configuration of this invention rotates the disk in a perfect circle and records at a constant speed along the radius of the rotating disk.
Includes a precision lathe where the machine is translated. As can be seen, it is required that the two drives be synchronized or otherwise cooperate so that a 10-helical track of a given pitch can be created. If desired, concentric circles can also be created by alternating translation and writing.

In a preferred embodiment using a spiral, the spacing between the open turns of adjacent spirals is 2 μm from center to center.

If the spot diameter is 1 μm, there is a guard region of 1 μm between spots in adjacent tracks.

The features believed to be novel and characteristic of the invention, together with further objects and advantages thereof, both as to mechanism and method of operation, are set forth in the appendix herein by way of preferred embodiments or examples of the invention. It will be better understood by considering the following description in conjunction with the drawings. It should be specifically understood, however, that the drawings are for purposes of illustration and description only and are not intended to limit the scope of the invention.

Turning first to FIG. 1, the writing device includes a writing head 11-12, which in this embodiment is a dry microscope objective 14 mounted on an air bearing support member 16. . A 40X lens has been found to be satisfactory. A disk 18 is specifically provided, which can be constructed according to the teachings of the prior art, in which the substrate is coated with a very thin film of a metal with a very low melting point and high surface tension. .

A crystal oscillator 20 controls the driving elements. The disk 18 is rotated by a first rotary drive element 22 which is connected to a spindle 24 .

A second translational drive element 26 controls the position of the door 12 for writing.

A translation carriage 28, which is driven by translation drive element 26 through the lead screw and transfer nut, moves write head 12 in its radial direction relative to rotating disk 18. . Carriage 28 is configured such that the remainder of the optical and electronic systems necessary for the writing device are permanently mounted.
Has a generous mirror and lens.

12- In an embodiment of the invention, polarization splitting laser 30, (
The beam (which is an argon ion laser) passes through a Pockels cell 32 which is driven by a Pockels cell driver 34 . FM modulator 36 receives the video signal to be recorded and provides appropriate control signals to Pockels cell driver 34. As is well known, Pockels cell 32 responds to an applied signal voltage by rotating the plane of polarization of the light beam. Since a linear polarizer transmits light only in a given plane of polarization, a polarizer, such as a Glan prism 38 in the embodiment, is placed in the write beam path to provide a modulated write beam 40.

A modulated writing beam 40 emerging from the Pockels cell 32 and Glan prism 38 combination is directed to a first mirror 4 which directs a second writing beam 40 onto a translation carriage 28.
Can be applied to 2. This first mirror 42 transmits a 13-portion of the writing beam 40 to a Pockels cell stabilization circuit 44 which maintains the energy level of the beam in response to the average intensity of the writing beam.

A lens 46 is inserted into the path of the writing beam 40 to diverge a substantially uniform beam that fills and widens the entrance aperture of the objective lens 14 to provide optimum resolution. A dichroic mirror 48 is placed in a passageway oriented to transmit substantially all of the writing beam 40 to a second arthroscope 50 . (It was shown in Eliot's patent application earlier)
A similar mirror can also be used in this invention. This arthroscope 50
then directs the beam through lens 14, beam 4
The point of zero impact can be varied on the surface of the disk 18.

Objective lens 14 and associated air bearing 16
effectively floats on a cushion of air at a substantially constant distance from the surface of disk 18. This distance is
It is determined by the geometry of the bearing 16, the linear speed of the disk 18, and the force used to load the head against the disk 18. This certain amount of space is required because the focal tolerance of a lens capable of resolving a 1 .mu.m spot is also 14 mm in 1 .mu. beats.

A second relatively low power laser 52 directs the monitor beam 5
Add 4 to 5. In the embodiment, the readout laser 52 is
It is a helium-neon device that allows the read beam 54 to be raised to a wavelength that is erased from the write beam. Polarizing beam splitting cube 56 transmits readout beam 54 to mirror 58 which directs beam 54 through a second diverging lens 60 which spreads readout beam 54 to fill the entrance aperture of objective lens 14. do.

A quarter-wave plate 62 is placed in the optical path in conjunction with the plane polarizing beam splitter 56 to allow light reflected from the disk 18 to enter the laser 521 again and perturb its oscillation mode. prevent. The quarter wavelength plate 62 is
It rotates the polarization plane of the beam by 45 degrees each time it passes through, so that the reflected beam is rotated 90 degrees with respect to the polarizing beam splitter 56 and therefore does not pass therethrough.

A second mirror 64 in the read beam 54 path directs the beam into a dichroic m1rror 48 such that the read beam "spot" is aligned with the write beam as will be explained in more detail below. Disc 18 downstream from the spot
Limited adjustments can be made so that the paths of the write and read beams are substantially identical, except for the point where they impinge on the top.

A filter 66 opaque to the argon ion beam is inserted into the path of the light reflected from beam splitter 56 . The He-Ne read beam 54 returned from the disk surface may pass through a filter 66 and a lens 68 onto a photodetector 70.

The output of photodetector 70 is applied to a preamplifier 72 which provides a signal with sufficient amplitude and signal strength for subsequent use. A video discriminator 74 then provides a video output signal which may be utilized in a number of ways, two of which are shown by way of example only.

In the first application, the video output is the television monitor 7
6 and oscilloscope 78. tv set·
A monitor 76 indicates the video fidelity of the recording, and an oscilloscope 78 indicates the signal-to-noise ratio and quality of canting, light or heavy, of the recording. Although not shown, an appropriate feedback system is applied to ensure that the gap between the "hole" or "black" and "non-hole" or "white 1" areas is well differentiated on the disk. This can be done by providing a loop.

As an alternative use, the video output of discriminator 74 is applied to comparator 80. Other power for comparator 80 is taken from the video input signal, which is directed through delay line 81. The accumulated delay of the writing scheme and the delay equal to the time elapsed between the moment of writing the information and the time required for the incremental area of the disk to reach the reading point must be imparted to the input video signal. No.

Ideally, the video output signal of discriminator 74 should be identical in all respects to the video input signal after an appropriate delay. Differences to note are defects on the surface of the disc,
Alternatively, it represents an error caused by the sensitization effect of the write circuit.

17-1b- This application is important when writing digital information, but is less critical when other information is recorded.

The output of the comparator circuit 8() can be quantified and counted, so that an acceptable number of errors can be established for any disc. When the counted error exceeds the standard, the write operation can be terminated. If necessary, you can burn a new disc. A disc with excessive errors can then be reprocessed and serve as a new disc for subsequent recording.

Known techniques are available for radially translating write head assembly 12 relative to rotating disk 18. In FIG. 1, a rotational and a translational drive device 2 is shown.
Although shown as 0.22 independent, these drives may be synchronized by a common crystal oscillator 20 to translate write assembly 12 by a predetermined increment for each revolution of disk 18.

Next, if you turn over the second figure, you will see a somewhat exaggerated 18
- , the slightly different optical paths of beam 40 from write laser 30 and beam 54 from read laser '52 are shown. The writing beam 40 is aligned with the optical axis of the microscope lens 14. In contrast, the reading beam 54 makes an angle a with the optical axis and is directed downstream from the writing beam 40 to the focal point of the objective lens 52. deviated by a distance #I!× equal to 0 times the kn distance.As a result, the resulting delay between succession and writing causes the molten metal to solidify, whereupon the record is read in its final state.

If the metal is read out so quickly that it is stuck, it does not provide adequate information to adjust the recording parameters.

This is best illustrated in FIG. 3 where the points 2-) on the same information channel are shown offset. Point A, which is the point of impact of the writing beam 4 ( ), is shown to be at the optical axis -F of the objective lens 14 . 9. A distance of 2 μm between points A and B is located at an angle α from the axis of the microscope objective 14, as indicated by the arrow, away from point A and in the direction of the movement of the medium. Distance provides a satisfactory monitor of write operations.

Turning finally to FIG. 4, an idealized LΣ diagram of a Pockels cell stabilization circuit 44 suitable for use in the apparatus of FIG. 1 is shown. As is well known,
A Pockels cell rotates the plane of polarization of applied light as a function of applied voltage. .

Therefore, a Pockels cell is used to rotate a plane-polarized beam of light, and the rotated light is passed through a plane polarizer, such as a Grand Prism.

The light emerging from the polarizer is amplitude modulated by the applied voltage.

Depending on the individual Pockels cell, approximately] 00
A voltage change in volts causes the cell to rotate the plane of polarization 360 degrees. However, the movement characteristics of an individual cell can vary arbitrarily in response to voltage changes of ±50 volts, so a feedback loop is desired to maintain the cell within a useful, reasonably linear operating range.

Stabilization circuit 44 includes a photosensitive silicon diode 82 positioned to receive a portion of write beam 40 reflected from mirror 42 of FIG. The silicon diode 82 operates in much the same manner as a solar cell, providing a source of solar energy when illuminated by an incident beam of light.

One terminal of the silicon diode 82 is connected to a common reference potential 84 represented by a conventional ground signal, and the other terminal is connected to one power source of a differential amplifier 86. Silicon cell 82 is shunted by a load 88 allowing a linear response moat.

The Ikekata input of differential amplifier 86 is connected to common reference 84 through a suitable voltage divider 90. A power supply 92 is coupled to a voltage divider 90, which is coupled to a differential amplifier 86 to establish the average light level delivered by Pockels cell 32.
It is given by setting .

The pair of output terminals of the differential amplifier 86 are then connected to the input terminals 21-20- of the Pockels cell 32 of FIG. 1 through resistive elements 94 and 96, respectively. Pockels cell driver 34 is Pockels cell 3
Note that differential amplifier 86 is AC coupled to Pockels cell 32, while differential amplifier 86 is DC coupled to Pockels cell 32.

In operation, this scheme is activated. Light from the writing beam impinging on silicon diode 82 generates a differential voltage at the input to differential amplifier 86. at first,
The partial pressure meter 90 is adjusted to produce light at a predetermined average level of intensity. A correction voltage is then generated in differential amplifier 86 as the average level of intensity impinging on silicon cell 82 increases or decreases. pockels cell 3
The correction voltage applied to 2 is of sufficient polarity and magnitude to restore the average level intensity to a predetermined level.

An improved video disc recording assembly has thus been demonstrated. The microscope objective, mounted on an air bearing, floats 1° at a predetermined distance from the surface of the metallized disk. At a surface tension of 1, such that enough energy can be released to melt an area, the molten metal will contract leaving a distinct area of about 1 micron in diameter. do.

A second low-energy laser utilizing substantially the same optical path is directed through the same microscope objective, or
The point of writing is brought to the surface of the disk a short distance downstream 1.

The subsequent beam is returned through a suitable optical system that eliminates the reflected energy of the writing beam, allowing analysis of the information pierced by the disc.

The reproduction information, in particular, controls the intensity of the writing beam to ensure an appropriate recording level 1 (7), and determines whether an unacceptable number of errors or errors have occurred in the recording process.

[Brief explanation of the drawing]

Figure 1 is a schematic drawing of the device of the invention. FIG. 2 is a diagram of the optical path through the objective of FIG. 1; FIG. 3 is a diagram illustrating the relative spacing between the points of impact of the write beam and the read beam. FIG. 4 is M of the new imaginary Pockels cell stabilization circuit. 18... Disc, 22... Rotation drive element, 1
2... To write/g, 20... Uniform drive element,
30...Polarization splitting laser, 40...Writing beam,
(2 Bonkels cell, 38... Grand prism, 46... Objective lens, 1G... Bearing, 50... Arthroscope, 52... Readout laser. t2 figure

Claims (1)

[Claims] 1) A device for storing information in an information storage member, comprising a first means for generating an information signal to be stored, a substrate having a first surface, and information covering the first surface and corresponding to the information signal. an information storage member including a photoresponsive coating carrying an indicia; and means for moving the storage member relative to a light source that produces a light beam of sufficient intensity to act on the coating and cause it to carry an information indicia; , an optical means forming an optical path between the light source and the coating of the storage member, and an optical means for focusing the light beam on the coating; a light intensity modulating means installed and operating over a range of high and low light transmission states to modulate the intensity of the light beam carrying the information to be stored;
The information storage member includes an optical disc, the information stored on the disc is in the form of a frequency modulated signal, and the signal is in the form of a carrier frequency that performs a frequency timing conversion representing the stored information. means for moving said storage member rotates said storage member at a substantially constant speed, and said light intensity modulating means is responsive to said frequency modulated signal for each cycle of said frequency modulated signal. 2. A device according to claim 1, characterized in that the light beam is modulated with a frequency modulated signal to be stored on the disk, varying between a light transmitting state and a low light transmitting state.