CA1057399A - Apparatus and method for reading videodisc - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention relates to reading of stored information from a videodisc. Attempts have been made in the prior art to read information from video-discs to produce a video signal having its amplitude varying with time. Through the entire process of re-cording to reading, however, poor quality of the repro-duced signal can result due to the format of the recorded signal and the manner of reading. The present invention overcomes these deficiencies by providing an improved apparatus and method for reading stored information on videodiscs, the information being in the form of a lineal series of regions of alternately high and low reflectivity in a direction normal to the disc surface.
In accordance with the invention, the reading system includes a polarized collimated beam of light, and an optical system between the light source and the video-disc for focusing the reading beam upon the videodisc.
Relative motion is provided between the reading beam and the alternate regions for generating reflections from the high light reflective regions on the video-disc. A light sensor is responsive to the reflections for generating a frequency modulated electrical signal caused by the reflections. The reproduced frequency modulated signal has its informational content in the form of a carrier frequency which has a frequency vary-ing with time.

Description

r,, ~

105739~

APPARATUS AND METHOD FOR RETRIEVING
INFORMATION FROM A VIDEODISC
_ CHNICAL FIELD
The present invention relates to reading of stored in~ormation from an information storage member, and more particularly to reading video information from a videodisc.
EACKGROUND OF THE PRIOR ART
Sy~tems have heretofore been developed for recordlng and reproducing signals at video frequencies upon disc~, tapes, or other media. Such systems have utilized, among other things~ optical recording upon photo~ensltive media, electron beam recording on thermo-plastic ~urfaces, and still other systems provide an instantaneously reproducible record of video information.
The prior art can generally be divided lnto system~ utilizing photographic surfaces, systems util-izing electron beam sensitive surfaces, ~agnetic record-ing systems, and as in the present invention, systems in which a radiant energy beam causes an irreversible change to a surface, thereby "writing" information thereon to be read out by a compatible reading apparatus.
Photographic systems have been described in the patents to P. C. Goldmark, et al, No. 3,234,326, which teaches recording on a continuous web such as a tape or ~ilm, or the patent to W. R. Johnson, No. 3,361,873, which teaches the photographic recordation of video information on a rotating disc in a spiral path.
, The patent to W. C. Hughes, et al, No. 3,283,310 - . ~

~057399 is illustrative of recordation of information on a thermo-plastic film surface, which utilizes an elec-tronic beam writing apparatus such as was disclosed in U. S. Patent No. 33120,991.
Yet other systems have employed an electron beam to record information on a special storage medium.
One such system has been disclosed in the patent to D. P. Gregg, No. 3,350,503. An alternative scheme utilizing an electron beam on a photosensitive medium 10 such as photographic film has been taught in the patent to R. ~. Dubbe, et al, No. 3,444,317.
In recent years, alternative methods have been disclosed for high density recording which are based upon either removal of material or vaporization of material by laser beam bombardment. These methods have been discussed briefly in the magazine "Elec-tronics", of March 3, 1969, at page 110. Further, a "laser thermal mlcro image recorder" was described in some detail by C. O. Carlson and H. D. Ives in a paper given at the 1968 WESCON meetin~ estern Electronic Show and Convention), which paper wa~ published in ;Volume 12 of WESCON Technical Papers for 1968, at page 1 of Section 16/1. The authors have referred to artlcles in the December 23; 1966, issue of "Science", Volume 54, No. 3756, at pages 1550 and 1551, the Proceedings of the Fall Joint Computer Conference of 1966, pages 711-716, and an article in the "Bell Systems Technical Journal", of March 1968, pages 385, 405.
These publications disciose a recording tech-;3o nique which utilizes a thin metalllc film coating upon a substrate. The thin metal film, under applied heat, melts rapidly and forms small globules within a recorded spot. A highly concentrated spot of laser illumination can apply sufficient heat in a short enough time so that a suitably modulated laser beam impinging upon a moving surface can produce a pattern of holes in the metallic surface which, when "read back', can reproduce the information recorded.
As pointed out in the Carlson and Ives paper, , --`~ 105~73 --3 ~-supra, khe slze of the recorded spot or hole can be much smaller than the diameter of the imaged laser beam.
By an appropriate choice of metal film materialg film thickness, laser divergence and spot power, an appro-priate system can be designed to record video frequencieswith reasonably high reso].utior.. Howeverg the quality of the video signal reproduced from such recordings has not been good due to a low signal-to-noise ratio resulting from the direct recording of the video signal onto the recording medium. Additionally, the use of a modulated laser beam to select~vely produce a pattern of holes on the metallic surface of a videodisc is not conducive to faithfully represent an amplitude varying analog video signal. Likewise, reading back the re-corded information in the form of a track of holes orspots on the surface of the disc is ineffective to faithfully recreate an analog video signal from the recorded track on the disc. The lack of fidelity in the reproduced video signal can be atkributed primarily to the 'Lna~ility of the laser beatn modulator to "write precise analog signals in the coating of the disc.
Consequently, the rcproduced signal developed by the reader suffers ln the same manner.
BRIEF SUMMARY OF THE INVENTION
The present lnvention provides an improved apparatus and method for reading stored information on a videodisc, the s~tored information having the form of a lineal series of regions representing a frequency modu-lated information signa]
3 In accordance w-lth the invention, there is provided an apparatus and method for reading stored information on videodiscs, the information being in the form of a lineal serles of regions of alternately high and low reflect'lv-lty normal to the surface of the disc. That is, when vlewed from a point above the sur-face of the discg an lmpinging light beam directed nor-mal to the surface would reflect alternately with high and low levels of reflected lighk in a direction oppo-site that of the impingi.ng l-lght beam.

~. .. i . ~

:' . . ~ ;. . .

.. ~

- ~OS7399 The reading system includes a polarized colli-mated reading beam of light, and an optical system between the light source and the videodisc for focusing the reading beam upon the videodisc. Relative motion is provided between the reading beam and the alternate regions for generating re~lections ~rom the high re-flective regions on the videodisc. A light sensor is responsive to the reflections for generating a fre-quency modulated electrical signal. The ~requency modulated electrical signal so developed has its informa-tional content in the form of a carrier frequency which has a frequency varying with time.
In a preferred embodiment, the disc-shaped videodisc has uniform rotational motion imparted to it -~
by atrotational driver synchronized with a transla-tional driver. The translational driver provides rela-tive motion between the reading beam and the disc for causing the focused light beam to move radially across the videodisc sur~ace as it rotates. An electrical synchronizer provides a constant relatlonship between the two drivers The videodisc has a lineal series of regions positioned in track-like ~ashion upon its upper surface.
The sequence of alternate regions of high and low re-flectivity normal to the disc surface represents afrequency modulated signal.
; The reading system preferably includes a low power laser for producing a reading light beam, a polarizing beam splitting cube, and a quarter wave plate. Light passes from the laser source through the polarizing beam splitter and to the quarter wave plate.
The quarter wave plate is used to rotate the incident reading light beam forty-five degrees on passage through to the videodisc. At the videodisc the optical system includes an objective lensJ and a hydrodynamic air bearing for supporting the lens above the surface of the videodisc. The objective lens has an aperture larger in diameter than the diameter of the reading beam. The - optical system makes use o~ mirrors and lenses for ' :. , , : . . . .. : . ...
: ... . . .. .
- . . . .
. . , . : , diverging the reading beam from the laser source to at least fill the entrance aperture of the objective lens.
The reflected light from the videodisc returns by means of mirrors and lenses through the quarter wave plate where it i8 once again rotated forty-five degrees to impart a total of ninety degrees rotation relative to the beam from the source. The emerging beam passes on to ~he polarizing beam splitting cube which is adapted to direct the reflected reading beam to a sensor and away from the laser source.
The reflected light from the videodi~c direc-ted toward the sensor represents a frequency modulated signal having its informational content in the form of a carrler frequency having a frequency varying with time.
The frequency modulated output signal of the sensor may be changed into a time dependent voltage signal for display on a standard television monitor.
The novel eatures which are believed to be characteristic of the invention~ both as to organization and method of operation, together with further ob~ects and advantages thereo~, will be better understood from the following description considered in connection with the accompanying drawings in which several preferred embodiments of the invention are illustrated by way of , . 25 example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a defini-tion of the limits of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a generalized diagram of the appara-tus of the present invention;
` FIG. 2 is a view of the optical path through the objective lens of FIG. l;
FIG. 3 is a representational indication of the , 35 relative spacing between a point of impingement of the ; writing beam and of the reading beam; and FIG. 4 is a diagram of a novel Pockels cell stabilizing circuit.
' .

.. : . .

.. . . .

~-``` lOS7399 DETAILED DESCRIPTION OF THE INVENTION
Turning first to FIG. 1, the writing apparatus ~ includes a writing head 12 which is, in the pre~erred A embodiment, a dry microscope objective lens 14 mounted 5 upon an air bearing support member 16. A 40X lens has been ~ound to be satisfactory. A disc 18 is specially prepared and may be constructed according to the teachlngs of the prior art, in which a substrate has coated thereon a very thin film o~ a metal with a reason-10 ably low melting point and a high surface tension.
A crystal oscillator 20 controls the drive elements. The disc 18 is rotated by a first, rotational drive element 22 which is coupled to a spindle 24. A
second, translational drive element 26 controls the 15 position of the writing head 12.
A translating carriage 28, which is driven by the translational drive element 26 through a lead screw and travelling nut, moves the writing head 12 in the radial direction relative to the rotating disc 18. The 20 carriage 28 is provided with appropriate mirrors and len~es so that the remainder o~ the optics and elec-tronics necessary to the writing device may be perman-ently mounted.
In the preferred embodiment of the present 25 lnvention, the beam o~ a polarized cutting laser 30, which is an argon ion laser, is passed through a Pockels cell 32 which is driven by the Pockels cell driver 34. An FM modulator 36 receives the video signal that is to be recorded and applies the appropriate 30 control signals to the Pockels cell driver 34.
As described hereinafter, the video in signal is o~ the type displayable on a TV monitor. Accord-ingly, it is a voltage varying with time signal. The FM modulator 36 is of standard design and converts the 35 voltage varying with time signal to a frequency modu-lated signal having its informational content in the form of a carrier frequency having frequency changes with time corresponding to said voltage variations with time.
As is known3 the PoGkels cell 32 responds to . . . .. . .. .
. . . . . . ~ .. : . . . . . :

- . , : - -.

--` ` 1057399~
~ -7~
applied signal voltage by rotating the plane of polariza-tion of the light beam. Since a linear polarizer transmits light only ln a predetermined polarization plane, a polarizer, such as a Glan prism 38 in the preferred embodiment, is included in the writing beam path to provide a modulated writing beam 40. The modulated writing beam effectively follows the output of the FM modulator 36.
The modulated writing beam 40 emerging from the Pockels cell-Glan prism combination 32, 38 is applied to a first mirror 42 which directs the writing beam 40 to the translating carriage 28. The first mirror 42 transmits a portion of the writing beam 40 to a Pockels cell stabilizing circuit 44 which responds to the average intensity of the writing beam to maintain the energy level f of the beam.
A lens 46 is inserted in the path of the writing i beam 40 to diverge the substantially parallel beam so that it will spread to fill the entrance aperture of the ob~ective lens 14 for optimum resolution. A dichroic mirror 48 is included in the path oriented to substantially transmit all of the writing beam 40 to a second, articulated mirror 50. The articulated mirror 50 then directs the beam through the lens 14 and is capable of shifting the point of impingement of the beam 40 on the surface of the disc 18, A series of holes is formed in the metal coating by the writing beam. One hole is formed for each cycle of the FM modulated signal represented by the modulated writing beam 40. ~ince the modulated writing beam tracks the output of the FM modulator 36, the holes formed in the .

mb/ ~

.

~ 1057399 -7a- :

coati.ng also track the output of the FM modulator.
0bviously, slnce the informational content in the OUtptlt signal of the FM modulator 36 is ln the form fff frequency changes ln time about a carrier frequency, and since the "hole", "no hole" sequence represents the stored lnf~rmatlon ~ d slnce the disc ' ~ ' .
. .
.
mb l .

`

`` 1057399 18 is rotating at a uniform speed, the "hole", "no hole! sequence changes to represent the stored video in~ormation by the holes being formed closer or farther apart and the size of the hole becomes larger or smaller as the writing beam 40 changes under the control of the FM modulated output signal from the FM modulator 36.
The ob~ective lens 14 and the associated air bearing 16 e~fectively fly on a cushion o~ air at a ~ubstantially fixed distance from the surface of the di~c 18. That distance is determined by the geometry of the bearing 16, the linear velocity of the disc 18, and the force used to load the head against the disc 18.
The fixed spacing is required because the focal toler-ance of a lens capable of resolving a l~m spot is also of the order of 1 ~m.
A second, relatlvely low-power laser 52 pro-:
vides a monitoring beam 54. In the preferred embodi-ment, the reading laser 52 is a helium-neo device which enables the reading beam 5L~ to be distinguished ~rom the writing beam 40 by wavelength. A polarlzing, beam 3plitter cube 56 tran~mit~ the reading beam 54 to a mirror 58 that directs the beam 54 through a second diverging lens 60 that spreads the reading beam 54 to fill the entrance aperture of the objective lens 14.
A quarterwave plate 62 is placed in the opti-cal path and, in con~unction with the plane polarizing beam splitter 56, prevents light retlected from the disc 18 ~rom re-entering the laser 52 and upsetting its mode of oscillation. The quarterwave plate 62 rotates the plane o~ polariæation of the beam by 45 degrees on each pass so that the reflected beam is rotated 90 degrees with respect to the polarizing beam splitter 56 and is therefore not passed by it.
A second mirror 64 in the reading beam 54 path directs the beam into the dichroic mirror 4~ and is capable of l-imited ad~u~tment so that the paths of the writing and reading beams are substantially identical, except that the reading beam "spot" impinges on the disc 18 downstream from the writing beam spot as explained in .
. .

~057399 greater detail below.
A filter 66 that is opa~ue to the argon ion beam is interposed in the path of light reflected from the beam splitter 56. The He.Ne reading beam 54 that is return~d from the disc surface ls able to pass through the filter 66 and through a lens 68 onto a photo-detector 70.
The reflected light of the reading beam im-pinges upon the photodetector 70. The photodetector 70 operates in its standard manner and generates an elec-trical current representative of the light impinging ; thereupon. In this case~ the photodetector generates the signal represented by the "hole", "no hole" con-figuration formed in the coating. The "hole", "no hole" configuratlon is representative of the output of the FM modulator 36. The output of t;ie FM modulator 36 ~ is a carrier frequency having frequency changes with ; time representing the video signal to be recorded. The "hole"~ "no hole" configuration is representative o~ a carrier fre~uenc~J having frequency changes with time representlng the stored video signal. The output of the photodetector 70 is an electrical signal repre-senting the stored carrier frequency having frequency changes with time representing the stored video signal.
The output of the photodetector 70 is applied to a preamplifier 72 whlch provides a signal of suffi-cient amplitude and signal strength for subsequent ; utilization. A video discriminator 74 then provides a video output signal which can be utilized in several 3 ways, two of which are shown~ as examples only The discriminator 74 is of standard design and function. It takes the frequency modulated signal from the photodetector 70 and changes it to a time dependent voltage signal having its informational content in the form of a voltage varying with time format suitable for display in the TV monîtor 76.
In a first application, the vicleo output is applied to a TV monitor 76 and an oscilloscope 78. As ` is well known, the TV monitor ls responsive to a voltage ., - : ~
. . - . ~ . .

- `
1~)57399 varying with time signal. The information to be dis-played on the TV monitor is represented by a voltage change with time.
The TV monitor 76 shows the picture fidelty of the recording, and the oscilloscope 78 indicates the signal-to-noise ratio of the record and the quality of the cutting, whether it is light or heavy. Not shown, an appropriate feedback loop could be provided through the Pockels cell stabilizing circuit 44 to assure an adequate dlscrimination on the disc between a "hole" or "black" area and "no hole or "white" area.
As an alternative utilization, the video out-put of the discriminator 74 is applied to a comparator 80. The other input of the comparator 80 is taken from the video input signal which is directed through a delay line 81. A delay that is equal the accumulated delays of the writing system and the time elapsed between the instant of writing of the information and the time required for that incremental area of the disc to reach the reading point must be imparted to the input vldeo signal.
Ideally, the video output signal of the dis-~iminator 74 should be identical in all respects to the video input signal, after the proper delay.
As previously mentioned, the output from the discriminator 74 is a voltage varying with time signal.
The video in signal is also a voltage varying with time signal. Any differences noted represent errors which might be caused by imperfections in the disc's surface or malfunc~ions of the writing circuits. This applica-tion, while essential if recording digital information, is less critical when other information is recorded.
The output of the comparator circuit 80 can be quantized and counted~ so that an acceptable number of errors can be established for any disc. When the errors counted exceed the standard, the writing operation can be terminated. If necessary, a new disc can be written.
Any disc with excessive errors can then be reprocessed - to serve as a "new" disc for a subsequent recording.
;
- , .
", ' ', .:
, .

... ~ , .
, `: ' .

~057399 -11-- .
Well-known techniques are available to trans-late the write head assembly 12 in the radial direction with respect to the rotating disc 18. While in FIG. 1 the rotational and translational drives 20, 22 are in-5 dicated as independent, the drives are synchronized to :
enable the writing assembly 12 to translate a prede-termlned increment for each revolution of the disc 18, by means of the common crystal osclllator 20.
Turning next to FIG. 2 there is shown, in somewhat exaggerated form, the slightly differing opti-cal paths of beam 40 from the writing laser 30 and the beam 54 from reading laser 52. The writing beam 40 coincides with the optical axis of the microscope objec- -tive lens 14. The reading beam 54, in contrast, makes 15 an angle with the axis so that it falls some distance X, equal to ~ kimes the focal length of the ob~ective, "downstream" from where the writing beam 40 is "cutting". -~
The resulting delay between reading and writing allows the molten metal to solidify so that the recording is read in its final ~tate. If lt ~re read too soon while the metal was still molten, it would not provide pertinent information for ad~usting the recording par-ameters.
This is best indicated in FIG. 3 where two points in the same information channel are shown as dis-placed. The point A, which is the point of impingement ~ of the writing beam 40, is shown as being on the optical t axis ~ the ob~ective lens 14. Separated from point A, in the direction of medium motion, as indicated by the 30 arrow, is the reading point B, which is at an angle from the axis of the microscope ob~ective lens 14.
A distance between points A and B of two m~ has provided a satisfactory monitoring of the writing operation.
; Turning finally to FIG. 4J there is shown an 35 idealized diagram of a Pockels cell stabilizing circuit 44, suitable for use in the apparatus of FIG. 1. As is known, a Pockels cell rotates the plane of polarization of the applied light as a function of an applied volt-~ age. Therefore; the Pockels cell is used to rotate ;:', - '' ~ .,, .
'- ' : . ' ' . ~
.

~oS7399 plane polarized light, and the rotated light is passed through a plane polarizer, such as a Glan prism. The light iSSUillg from the polarizer will be amplitude modulated in accordance with the applied voltage.
Stated another way, the standard operating mode of a Pockels cell 32 and Glan prism 38 is for use as a light intensity modulating means. Each cycle from the FM modulator drives the Pockels cell through its full operating range of ninety degrees. Within this oper-ating range of ninety degrees, one operating point passes all light applled thereto and identified as a full light transmitting state. A second operating point passes no light and is identi~ied as a full light blocking state. The Pockels cell itself only rotates the plane of polarization. The Glan prism passes light in one plane of polarization and no light in the plane displaced ninety degrees from that plane in which all the light passes.
Depending upon the individual Pockels cell, a voltage change o~ approximately 100 volts will cause the cell to rotate the plane of polarization through 360 degrees. However, the transfer characteristic of an individual cell may drift spontaneously, correspond-ing to a voltage change of - 50 volts, and accordingly, a feedback loop is desirable to maintain the cell with-in a useful, reasonably linear, operatlng range.
The stabilizing circuit 44 includes a photo-sensitive silicon diode 82, which is positioned to receive a portion of the writing beam 40 reflected from the mirror 42 of FIG. 1. The silicon diode 82 functions in much the same fashion 8S a solar cell and is a source ; of electrical energy when illuminated by incident radia-tion. One terminal of the silicon diode 82 is connected to common reference potential 84, indicated by the conventional ground symbol, and the other terminal is connected to one input of a differential amplifier 86.
The silicon cell 82 is shunted by a load 88 which enables a linear response.
The other input to the differentlal amplifier -- .

, 86 is connected through an appropriate potentiometer 90 to the common reference 84. A source of power 92 is coupled to the potentiometer 90, which enables the setting of the differential amplifier 86 to establish the average light level transmitted by the Pockels cell 32 .
Accordingly, a pair of output terminals of the dlfferential amplifier 86 are respectively connected through resistive elements 94, 96 to the input terminals of the Pockels cell 32 of FIG. 1. It is noted that the Pockels cell driver 34 is a.c. coupled to the Pockels cell 32, while the dlfferential amplifier 86 is d.c.
coupled to the Pockels cell 32.
In operation, the system is energized. The light from the writing beam impinging on the silicon diode 82 generates a differential voltage at the input to the differential emplified 86. Initially, the poten-tiometer 90 is adjusted to produce light at a predeter-mined average level of intensity. mereafter, if the ~0 average level of intensity impinging on the silicon cell 82 either increases or decreases, a correcting voltage will be generated in the differential amplifier 86. The correcting voltage applied to the Pockels cell 32 is of a polarity and magnitude adequate to restore 25 the average level of intensity to the predetermined level.
Thus there has been shown an improved video disc recording assembly. A microscope objective lens mounted on an air bearing "flies" at a predetermined distance from the surface of a metallized disc. me metallized coating is such that a laser beam can, under suitable modulation, deliver sufficient energy to melt localized areas of the surface. Under surface tension, the molten metal retracts leaving a clear area of appro~
35 imately one micron in diameter.
A second, low-energy laser utilizing substan-tially the same optical path is directed through the , same microscope objective lensg but is brought to the surface of the disc at a slight distance "downstream"

;i .
.

-- ` lOS~399 from the point of writing. The reading beam is returned through an appropriate o~tical system that excludes the reflected energy of the writing beam and enables an analysis ~ the information that has been written on the disc.
The playback information can, among other things, control the intensity of the writing beam to assure adequate "recording levels"g determine whether an unacceptable number of errors have been made in the 10 recording process.
.

.

. . . . . . ..

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An optical system for retrieving a frequency modulated signal stored on a surface of an information storage member in the form of a lineal series of regions of alternately high and low directional reflectivity normal to said surface, said system comprising: means for producing a polarized collimated beam of light; support means for holding the information storage member; optical means for defining an optical path between said light beam producing means and said information storage member held upon said support means, and for focusing said light beam upon the alternately high and low directional reflectivity regions, said optical means being further employed for collecting reflections from said high light reflective areas; means for providing relative motion between said beam of light and said alternate regions for generating reflections from said light reflective region representing the stored frequency modulated signal; and light sensing means responsive to said reflections for generating a frequency modulated electrical signal corresponding to said reflections, said last mentioned frequency modulated signal having its informational content in the form of a carrier frequency having frequency changes in time corresponding to the stored information.

2. The system as claimed in Claim 1, including an information storage member defining said surface.

3. The system as claimed in Claim 1, including means responsive to the output of said light sensing means for changing said frequency modulated electrical signal into a time dependent voltage signal representing said stored information, said time dependent voltage signal having its informational content in the form of a voltage varying with time format and being suitable for display by a standard television monitor.

4. The system as claimed in Claim 2, further comprising: a beam polarizer, and a polarization shift-ing means for shifting the plane of polarization of said beam, said polarizer and shifting means disposed in the path of said light beam with the beam polarizer located between said light beam source and said shifting means, said shifting means rotating said beam during incident and reflected passages through the shifting means to and from the storage member, said polarizer substantially reducing the intensity of the reflected beam passed through said shifting means toward said light beam producing means.

5. The system as claimed in Claim 4, wherein said shifting means is a quarter wave plate for rotat-ing said light beam ninety degrees by accumulative incident and reflected passages through said plate.

6. The system as claimed in Claim 4, wherein said beam polarizer is a polarizing beam splitting cube adapted to direct said reflected beam passed through said shifting means toward said light sensing means.

7. The system as claimed in Claim 1, wherein said optical means includes: an objective lens; and hydrodynamic air bearing means for supporting said lens above said surface of said information storage member.

8. The system as claimed in Claim 7, wherein said collimated beam of light has substantially parallel light rays; said objective lens has an entrance aperture larger in diameter than the diameter of said light beam as provided by said light source; and said optical means further includes mirror means for folding said light beam path provided by said light source, and a diverging lens for spreading the substantially parallel light beam from said light source to at least fill said entrance aperture of said objective lens.

9. The system as claimed in Claim 1, wherein:
said storage member is disc-shaped; said means for providing relative motion comprises rotational drive means for producing uniform rotational motion of said disc; and wherein said apparatus further comprises: translational drive means synchronized with said rotational drive means for moving said focused light beam radially across said surface of said disc-shaped storage member; and electrical synchronizing means for maintaining a constant relationship between said rotational motion and said translational motion.

10. A method for reading an information signal stored on a record member, the information signal being in the form of alternate areas of high and low directional reflectivity normal to the surface of the record member, comprising the steps of: providing an information storage member having an information bearing surface, said surface having a lineal series of said areas positioned in track-like fashion upon said surface, the sequence of alternate regions representing a frequency modulated signal having its informational content in the form of a carrier frequency having frequency changes with time varying from said carrier frequency; imaging a polarized collimated beam of light upon said series of regions; providing relative motion between said imaged beam of light and said alternate regions for generating reflections from said light reflective regions representing said stored frequency modulated signal; and sensing said reflections and generating a frequency modulated electrical signal corresponding to said reflections, said frequency modulated electrical signal having its informational content in the form of a carrier frequency having frequency changes in time from said carrier frequency.

11, The method as claimed in Claim 10, including the step of demodulating said frequency modulated electrical signal to produce a time dependent voltage signal represent-ing said stored information, said time dependent voltage signal having its informational content in the form of a voltage varying with time format and being suitable for display by a standard television monitor.

12. The method as claimed in Claim 10, further comprising the step of shifting the plane of polarization of said polarized beam by rotating said beam during incident and reflected passages to and from the storage member, thereby substantially reducing the intensity of the reflected beam passed to a light beam source utilized in producing the light beam in said imaging step.

13. The method as claimed in Claim 12, wherein said shifting step includes rotating said light beam ninty degrees by accumulative incident and reflected passages of said second light beam to and from said storage member surface.

14. The method as claimed in Claim 10, wherein the storage member is disc-shaped and said step of providing relative motion includes: producing uniform rotational motion of said disc; and synchronizing said rotational motion with movement of said storage member for effecting relative movement of said imaged light beam radially across said surface of said disc-shaped storage member to maintain a constant relationship between said rotational motion and said translational motion.